05th International Conference on Permafrost - 2 ... - IARC Research
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PERMAFR os T<br />

I<br />

Fifth <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g><br />

PROCEEDINGS VOLU 'ME 2<br />

Editor:<br />

Kaare Senneset<br />

i<br />

Organized by<br />

The Norwegian Committee <strong>on</strong> <strong>Permafrost</strong><br />

The Norwegian Institute of Technology<br />

' TAPIR PUBLISHERS<br />

-%ndheim, Norway<br />

Organizing Committee<br />

Kaare Flaate<br />

Odd Gregersen<br />

KaareH~eg<br />

Bjarne Instanes<br />

Tore Jfirgensen<br />

J<strong>on</strong> Krokebrg<br />

William Martin<br />

Magne Often<br />

Alv Orheim<br />

Ole Rcistad<br />

Otto Salvigsen<br />

Kaare Scnneset<br />

Johan Ludvig Sollid<br />

Reidar S~tersdal

0 Tapir Publishers, Tr<strong>on</strong>dheim, Norway<br />

ISBN 82-5 19-0863-9<br />

Printed in Norway.

-<br />

CONTENTS<br />

VOLUME 1: SCIENCE<br />

CLIMATE CHANGE AND GEOTHERMAL REGIME<br />

PALEOCLIMATE AND PERMAFROST IN THE MACKENZIE DELTA<br />

D. Allen, F. Michel and A. Judge<br />

METEOROLOGICAL CONDITIONS’ INFLUENCE ON THE PERMAFROST<br />

GROUND IN SVEAGRUVA, SPITSBERGEN<br />

S. Bakkehoi and C. Bandis<br />

THERMAL CURRENTS OF ACTIVE LAYER IN HORNSUND AREA<br />

H. Chmal, J. Klementowski and K. Migala<br />

FREEZING-POINT DEPRESSION AT THE BASE OF ICE-BEARING<br />

PERMAFROST ON THE NORTH SLOPE OF ALASKA<br />

T.S. Collett and KJ. Bird<br />

NATURAL GROUND TEMPERATURES IN UPLAND BEDROCK<br />

TERRAIN, INTERIOR ALASKA<br />

CM. Collins, RK. Haugen and R A. Kreig<br />

THAWING IN PERMAFROST - SIMULATION AND VERIFICATION<br />

M. Ymuz Corapcioglu and S. Panday<br />

SCHEFFERVILLE SNOW-GROUND INTERFACE TEMPERATURES<br />

D.T. Desrochers and HB. Granberg<br />

A LONG-TERM PERMAFROST AND CLIMATE MONITORING<br />

PROGRAM IN NORTHERN CANADA<br />

DA. Etkin, A. Headley and KJL. Stoker<br />

PERMAFROST-CLlMATIC CHARACTERISTICS OF Different CLASSES<br />

M.K. Gmrilowa<br />

LATE QUATERNARY SOLIFLUCTION IN CENTRAL SPITSBERGEN<br />

P. Klysz, L. Lindner, L. Marks and L. Wysokinski<br />

GEOMORPHOLOGICAL EFFECTS AND RECENT CLIMATIC RESPONSE<br />

OF SNOWPATCHES AND GLACIERS IN THE WESTERN ABISKO<br />

MOUNTAINS, SWEDEN<br />

L. Lindh, R. Nyberg and A. Rapp<br />

GAS-HYDRATE ACCUMULATIONS AND PERMAFROST DEVELOPMENT<br />

YuF. Makog<strong>on</strong><br />

A HYPOTHESIS FOR THE HOLOCENE PERMAFROST EVOLUTION<br />

L.N. Maximova and YYe. Romanovsky<br />

DIVISION AND TEMPERATURE CONDITION OF THE LAST<br />

GLACIATION IN NORTHERN CHINA<br />

Sun, Jianzh<strong>on</strong>g and Li, Xinguo<br />

33<br />

39<br />

44<br />

50<br />

56<br />

61<br />

67<br />

73<br />

78<br />

84<br />

89<br />

95<br />

102

REGIONAL PERMAFROST<br />

SHORELINE PERMAFROST IN KANGIQSUALUJJUAQ BAY, UNGAVA, Quebec<br />

M. Allard, MK. Seguin and Y. Pelletier<br />

PERMAFROST DATA AND INFORMATION: STATUS AND NEEDS<br />

R.G. Barry<br />

GEOCRYOLOGICAL MAP OF MONGOLIAN PEOPLE' S REPUBLIC<br />

V.V. Baulin, GL. Dubikov, Yu.T. Uvarkin, AL. Chekbvsky, A. Khishigt,<br />

S. Dolzhin and R. Buvey-Bator<br />

GEOTECHNICAL AND GEOTHERMAL CONDITIONS OF NEAR-SHORE<br />

SEDIMENTS, SOUTHERN BEAUFORST SEA, Northwest TERRITORIES,<br />

CANADA<br />

SR. Dallimre, P.J. Kutfurst and JAM. Hunter<br />

MASSIVE GROUND ICE ASSOCIATED WITH GLACIOFLUVIAL SEDIMENTS,<br />

Richards ISLAND, N.W.T., CANADA<br />

SR. Dallimore and SA. Wove<br />

PERMAFROST AGGRADATION ALONG AN EMERGENT COAST,<br />

Churchill MANITOBA<br />

L. Dyke<br />

CHARACTERISTICS OF THE MASSIVE GROUND ICE BODY IN THE<br />

Western CANADIAN ARCTIC<br />

(Fujinb, Kazuo, Sato, Seiji, Matsuda Kyou, Sasa, Gaichirau, Shimizu,<br />

Osamu and Kato, Kikuo<br />

MEASUREMENTS OF ACTIVE LAYER AND PERMAFROST PARAMETERS<br />

WITH ELECTRICAL Resistivity SELF POTENTIAL AND INDUCED<br />

POLARIZATION<br />

E. Gahe, M. Allard, M.K. Seguin and R. Fortier<br />

THE ALPINE PERMAFROST ZONE OF THE U.S.S.R.<br />

A.P. Gorbunov<br />

ON THE SPATIAL DYNAMICS OF SNOWCOVER - PERMAFROST<br />

RELATIONSHIPS AT SCHEFFERVILLE<br />

HB. Granberg<br />

PERENNIAL, CHANGES IN NATURAL, COMPLEXES OF CRYOLITHOZONE<br />

G.F. Gravis, N.G. Moskalenko and A.V. Pavlov<br />

PERMAFROST AND ITS ALTITUDINAL ZONATION IN N. LAPLAND<br />

P.P. Jeckel<br />

113<br />

119<br />

123<br />

127<br />

132<br />

138<br />

143<br />

148<br />

154<br />

159<br />

165<br />

170<br />

A MODEL FOR MAPPING PERMAFROST DISTRIBUTION BASED ON<br />

LANDSCAPE COMPONENT MAPS AND CLIMATIC VARIABLES 176<br />

M.T. Jorgens<strong>on</strong> and RA. Kreig

PERMAF'ROST SITES IN FINNISH LAPLAND AND THEIR ENVIRONMENT<br />

OCCURRENCES DE PERGELISOL EN LAPPONIE FINLANDAISE<br />

L. King and M. Seppali<br />

CRYOGENIC COMPLEXES AS THE BASIS FOR PREDICTION MAPS<br />

I.V Klimovsky and SP. Gotovtsev<br />

GLACIAL HISTORY AND PERMAFROST IN THE SVALBARD AREA<br />

J.Y. Lundvik,- J. Mangerud and 0. Salvigsen<br />

REGIONAL FACTORS OF PERMAFROST DISTRIBUTION AND THICKNESS,<br />

HUDSON BAY COAST, QUEBEC CANADA<br />

R. Levesque M. Allard and M.K. Seguin<br />

PINUS HINGGANENSIS AND PERMAFROST ENVIRONMENT IN THE<br />

MT.DA-HINGANLING, NORTHEAST CHINA<br />

Lu, Guowei<br />

NATURAL GEOSYSTEMS OF THE PLAIN CRYOLlTHOZONE<br />

E.S. Melnikov<br />

Predicting THE OCCURRENCE OF PERMAFROST IN THE ALASKAN<br />

DISCONTINUOUS ZONE WITH SATELLITE DATA<br />

LA. Morrissey<br />

MODERN METHODS OF STATIONARY ENGINEERING - GEOLOGIC<br />

INVESTIGATIONS OF CRYOLITIC ZONE<br />

A.V. Pavlov and V.R. Tsibulsky<br />

PETROGRAPHIC CHARACTERISTICS OF MASSIVE GROUND ICE, YUKON<br />

COASTAL PLAIN, CANADA<br />

W.H. Pollard and SR. Dallimre<br />

CONTENT OF NORTH AMERICAN CRYOLITHOLOEICAL MAP<br />

AJ. Popov and G.E. Rosenbaum<br />

NEW DATA ON PERMAFROST OF KODAR-CHARA-UDOKAN REGION<br />

NN. Romanovsky, VN. Zaitsev, S.Yu. Volchenkoc, VP. Volkova and<br />

O.M. Lisitsina<br />

MEAN ANNUAL TEMPERATURE OF GROUNDS IN EAST SIBERIA<br />

S.A. Zamolotchibva<br />

ALPINE PERMAFROST IN EASTERN NORTH AMERICA: A REVIEW<br />

T.W. Schrnidlin<br />

SEASONAL Freezing OF SOILS IN CENTRAL ASIA MOUNTAINS<br />

I.V. Seversky and E.V. Seversky<br />

ALPINE PERMAFROST OCCURRENCE AT MT. TAISETSU, CENTRAL<br />

HOKKA 0, IN NORTHERN JAPAN<br />

1- Toshio, Takahashi, Nobuyuki and Fukuda, Masami<br />

Some<br />

183<br />

189<br />

194<br />

199<br />

205<br />

208<br />

213<br />

218<br />

224<br />

230<br />

233<br />

237<br />

241<br />

247<br />

253

ROCK GLACIERS AND GLACIATION OF THE CENTRAL ASIA MOUNTAINS<br />

S.N.Titkov<br />

GEOCRYOGENIC GEOMORPHOLOGY, EAST Flank OF THE ANDES OF<br />

MENDOZA, AT 330 S.L.<br />

D. Trombotto<br />

OUTER LIMIT OF PERMAFROST DURING THE LAST GLACIATION IN<br />

EAST CHINA<br />

Xu, Shuying, Xu, Defu and Pan, Baotian<br />

THE GEOCRYOLOGICAL MAP OF THE USSR OF 1:2,5OO,OOO SCALE<br />

ED. Yershov, KA. K<strong>on</strong>dratyeva, SA. Zamolotchikova, N.I. Trush and<br />

YeN. Dunaeva<br />

THE PERMAFROST ZONE EVOLUTION INDUCED BY DESTRUCTION OF<br />

Soil OVEWYING COVER IN THE AMUR NORTH<br />

S.I. Zubolotnik<br />

DISTRIBUTION OF SHALLOW PERMAFROST ON MARS<br />

A.P. Zent F.P. Fanale, JR. Salvail and S.E. Postawko<br />

259<br />

263<br />

268<br />

274<br />

278<br />

284<br />

PHYSICS AND CHEMISTRY OF FROZEN GROUND,<br />

FROST HEAVE MECHANISM<br />

ON THE METHOD OF CRYOHYDROGEOCHEMICAL INVESTIGATIONS<br />

N.P. Anisinwva<br />

Hydrochemistry OF RIVERS IN MOUNTAIN PERMAFROST AT 330 L.S.,<br />

MENDOZA - ARGENTINA<br />

EM. Buk<br />

FROST LINE BEHAVIOUR AROUND A COOLED CAVITY<br />

A.M. Cames-Pintaux and J. Aguirre-Puente<br />

A FROST HEAVE MODEL OF SANDY GRAVEL IN OPEN SYSTEM<br />

Chen, XB., Wang, KQ. and He, P,<br />

OBSERVATIONS OF MOISTURE MIGRATION IN FROZEN SOILS DURING<br />

THAWING<br />

Cheng, Guohng and E J. Chamberlain<br />

GEOCRYOLOGIC STUDIES AIMED AT NATURE CONSERVATION<br />

AB. Chizhov, A. Gavrilov and Ye.I. Pizhankova<br />

IRON AND CLAY MINERALS IN PERIGLACIAL ENVIRONMENT<br />

T. Chodak<br />

290<br />

294<br />

299<br />

304<br />

308<br />

316

FROZEN SOIL MACRO- AND MICROTEXTURE FORMATION<br />

YeM. Chuvilin and O.M. Yazynin<br />

ACOUSTICS AND UNFROZEN WATER CONTENT DETERMINATION<br />

M.H. Deschatres, F. Cohen-Tenoudji, J. Aguirre-Puente and B. Khastou<br />

THERMODYNAMICS THEORY FORECASTING FROZEN GROUND<br />

Ding, Dewen<br />

PORE SOLUTIONS OF FROZEN GROUND AND ITS PROPERTIES<br />

EJ. Dubikov, N.V. Ivarwva and VJ. Akrenov<br />

FORMATION PROBLEM OF THICK ICE STREAKS, ICE SATURATED<br />

HORIZONS IN PERMAFROST<br />

G.M. Feldman<br />

FROST HEAVE<br />

K.S. Forland T. Forland and S.K. Ratkje<br />

PARAMETRIC EFFECTS IN THE Filtrati<strong>on</strong> FREE CONVECTION MODEL<br />

FOR Patterned GROUND<br />

KJ. Gleas<strong>on</strong>, W. B. Kruntz and N. Caine<br />

HEAT AND MOISTURE TRANSPORT DURING ANNUAL FREEZING AND<br />

THAWING<br />

JP. Gosink, K. Kawasaki, T.E. Osterkamp and J. Holty<br />

SUMMER THAWING OF DIFFERENT GROUNDS - AN EMPIRICAL MODEL<br />

FOR WESTERN SPITSBERGEN<br />

M. Grzes<br />

OBSERVATIONS ON THE REDISTRIBUTION OF MOISTURE IN THE ACTIVE<br />

LAYER AND PERMAFROST<br />

S.A. Harris<br />

A MATHEMATICAL MODEL OF FROST HEAVE IN GRANULAR Materials<br />

D. Piper, J.T. Holden and R.H. J<strong>on</strong>es<br />

ELECTRIC CONDUCTIVITY OF AN ICE CORE OBTAINED FROM MASSIVE<br />

GROUND ICE<br />

Horiguchi, Kaoru<br />

PHYSICAL-CHEMICAL TYPES OF CRYOGENESIS<br />

VN. K<strong>on</strong>ischm V.V Rogov and SA. Pokl<strong>on</strong>ny<br />

TEMPERATURE OF ICE LENS FORMATION IN FREEZING SOILS ,<br />

J.M. K<strong>on</strong>rad<br />

Microstructure OF FROZEN SOILS EXAMINED BY SEM<br />

;‘Kumai,jMotov<br />

, ”. . ,,-./<<br />

CRYOGENIC DEFORMATIONS IN FINE-GRAINED SOILS<br />

Yu P. Lebedenko and L.V; Shevchenko<br />

320<br />

324<br />

329<br />

333<br />

339<br />

344<br />

349<br />

355<br />

361<br />

364<br />

370<br />

377<br />

381<br />

384<br />

390<br />

396

PROPERTIES OF GEOCHEMICAL FIELDS IN THE PERMAFROST ZONE<br />

V.. Makarov<br />

THE DYNAMICS OF SUMMER GROUND THAWING IN THE Kaffioyra<br />

PLAIN (NW SPITSBERGEN)<br />

K. Marcinid, R. Przybylak, W. Szczepanik<br />

A METHOD FOR MEASURING THE RATE OF WATER TRANSPORT DUE TO<br />

Temperature GRADIENTS IN UNSATURATED FROZEN SOILS<br />

Nakarw, Yoshisuke and AR. Tice<br />

FILTRATION PROPERTIES OF FROZEN GROUND<br />

BA. Olovin<br />

"HERMODIFFUSE ION TRANSFER IN GROUNDS<br />

YE. Ostroumov<br />

ELECTROACOUSTIC Effect IN FROZEN SOILS<br />

A.S. Pavlov and AD. Frolov<br />

SPATIAL VARIATION IN SEASONAL FROST HEAVE CYCLES<br />

E. Perfect R.D. Miller and B. Burt<strong>on</strong><br />

Directi<strong>on</strong> OF ION MIGRATION DURING COOLING AND FREEZING<br />

PROCESSES<br />

Qiu, Guoqing, Sheng, Wenkun, Huang, Cuilan and Zheng, Kaiwen<br />

DYNAMICS OF PERMAFROST Active LAYER - SPITSBERGEN<br />

J. Repelewska-Pekalowa and A. Gluza<br />

INVESTIGATION OF ELECTRIC POTENTIALS IN FREEZING DISPERSE<br />

SYSTEMS<br />

VP. Romanov<br />

PHYSICO-CHEMICAL NATURE OF CONGELATION STRENGTH<br />

B A. Saveliev, V.V. Razumov and VE. Gagarin<br />

HYDROGEOCHEMISTRY OF-KRYOLITHOZONE OF SIBERIAN PLATFORM<br />

SL. Schwartsev, VA. Zuev and MB. Bukaty<br />

THE FORMATION OF PEDOGENIC CARBONATES ON SVALBARD:<br />

THE INFLUENCE OF COLD TEMPERATURES AND FREEZING<br />

R .S. Sletten<br />

Measurement OF THE UNFROZEN WATER CONTENT OF SOILS:<br />

A COMPARISON OF NMR AND TDR METHODS<br />

M.W. Smith and AR. Tice<br />

GENESIS OF ARCTIC BROWN SOILS (PERGELIC CRYOCHREPT) IN<br />

SVALBARD<br />

F.C. Ugolini and R.S. Sletten<br />

401<br />

406<br />

412<br />

418<br />

425<br />

431<br />

436<br />

442<br />

448<br />

454<br />

459<br />

462<br />

467<br />

473<br />

478

OXYGEN ISOTOPIC COMPOSITION OF SOME MASSIVE GROUND ICE<br />

LAYERS IN THE NORTH OF WEST SIBERIA<br />

RA. Vaikmae VJ. Solomatin and Y.G. Karpov<br />

OXYGEN ISOTOPE VARIATIONS IN ICE-WEDGES AND MASSIVE ICE<br />

YuK. Vasilchuk and V.T. Trofimv<br />

THERMODYNAMIC AND MECHANICAL CONDITIONS WITHIN FROZEN<br />

Soils AND THEIR EFFECTS<br />

PJ. William<br />

TlME AND SPATIAL Variati<strong>on</strong> OF TEMPERATURE OF ACTIVE LAYER-<br />

IN SUMMER ON THE Kaffioyra PLAIN (NW SPITSBERGEN)<br />

G. Wojcik K. Marciniak and R. Prqbylak<br />

Temperature OF Active LAYER AT BUNGER OASIS IN ANTARCTICA<br />

IN SUMMER 1978-79<br />

G. Wdjcik<br />

CHEMICAL WEATHERING<br />

PERMAFROST REGIONS OF ANTARCTICA:<br />

GREAT WALL STATION OF CHINA, CASEY STATION AND DAVIS STATION<br />

OF AUSTRALIA<br />

Xie, Youyu<br />

WATER MIGRATION IN SATURATED Freezing Soil<br />

Xu, Xiaozu, Deng, Youseng, Wang, Jiacheng and Liu, Jiming<br />

EFFECT OF OVER CONSOLIDATION RATIO OF SATURATED SOIL ON<br />

FROST HEAVE AND THAW SUBSIDENCE<br />

Yamamcto, H., Ohrai, T. andIzuta, H.<br />

MASS TRANSFER INFROZEN SOILS<br />

ED. Yershov, YuP. Lebedenko, VD. Yershov and Ye.M. Chuvilin<br />

STRESS-STRAIN PREDICTION OF FROZEN Retaining STRUCTURES<br />

REGARDING THE FROZEN SOL CREW<br />

YuK. Zaretsb, Z.G. Ter-Martirosyan and A.G. Shchobolev<br />

STUDY OF FROZEN SOILS BY GEOPHYSICAL METHODS<br />

YuD. Zykov, N.Yu. Rozhdestuenrky and OP. Chervinskaya<br />

484<br />

489<br />

493<br />

499<br />

505<br />

511<br />

516<br />

522<br />

528<br />

533<br />

537

I<br />

HYDROLOGY, ECOLOGY OF NATURAL AND DISTURBED AREAS<br />

THE OUTFLOW OF WATER IN PERMAFROST ENVIRONMENT -<br />

SPITSBERGEN 543<br />

S. Bartoszewski, J. Rodzik and K. Wojciechowski<br />

MODELLING OF AVERAGE M<strong>on</strong>thly STREAMFLOWS FROM<br />

GLACIERIZED BASINS IN ALASKA 546<br />

D. Bjerkelie and R.F. Carls<strong>on</strong><br />

PROTECTION OF The ENVIRONMENT IN JAMESON LAND 552<br />

C. Baek-Madsen<br />

SUSPENDED SEDIMENT TRANSPORT IN ARCTIC RIVERS<br />

MJ. Clark, A.M. Gurnell and JL. Threlfall<br />

558<br />

THE BUFFERING POTENTIAL OF CARBONATE SOILS IN DISCONTINUOUS<br />

PERMAFROST TERRAIN, AGAINST NATURAL AND MAN-INDUCED<br />

ACIDIFICATION 564<br />

LA. Dredge<br />

PHYSICAL AND CHEMICAL CHARACTERISTICS OF THE Active LAYER<br />

AND NEAR-SURFACE PERMAFROST IN A DISTURBED HOMOGENEOUS<br />

PICEA MARIANA STAND, FORT NORMAN, N.W.T., CANADA 568<br />

K.E. Evans, G.P. Kershaw and B J. Gallinger<br />

HYDROLOGY AND GEOCHEMISTRY OF A SMALL DRAINAGE BASIN IN<br />

UPLAND TUNDRA, NORTHERN ALASKA 574<br />

KR. Everett and B. Ostendorf<br />

ENVIRONMENT Protecti<strong>on</strong> Studies IN PERMAFROST ZONE OF<br />

THE USSR 580<br />

NA. Grave<br />

CLASSIFICATION OF GROUND WATER IN PERMAFROST AREAS ON THE<br />

QINGHAI-XTZANG PLATEAU, CHINA 583<br />

Guo, Pengfei<br />

<strong>Permafrost</strong> HYDROLOGY OF A SMALL ARCTIC WATERSHED 590<br />

DL. Kane and L.D. Hinzman<br />

FLOWING WATER EFFECT ON TEMPERATURE IN OUTWASH DEPOSITS 596<br />

A. Karczewski<br />

SALIX ARBUSCLEOIDES ANDERSS, RESPONSE TO DENUDING AND<br />

IMPLICATIONS FOR NORTHERN RIGHTS-OF-WAY 599<br />

G.P. Kershaw, B J. Gallinger and L J. Kershaw<br />

ABLATION OF MASSIVE GROUND ICE, MACKENZIE DELTA 605<br />

A.G. Lmkowicz<br />

HYDROGEOLQGICAL FEATURES IN HUOLAHE BASIN OF NORTH<br />

DAXINGANLING, NORTHEAST<br />

Lira, Fengt<strong>on</strong> and Tu, Guangzh<strong>on</strong>g<br />

CHINA 611

SHALLOW OCCURRENCE OF WEDGE ICE: IRRIGATION FEATURES<br />

A A. Mandamv and IS. Ugarov<br />

SOIL INFILTRATION AND SNOW-MELT RUN-OFF IN THE MACKENZIE<br />

DELTA, N.W.T.<br />

P. Marsh<br />

LATE PLEISTOCENE DISCHARGE OF THE YUKON RIVER<br />

OK. Mas<strong>on</strong> and J.E. Beget<br />

INFLUENCE OF WATER PHENOMENA ON Depth OF SOIL THAWING IN<br />

OSCAR 11 LAND, NORTHWESTERN Spitsbergen<br />

C. Pietrucien and R. Skowr<strong>on</strong><br />

INFLUENCE OF AN ORGANIC MAT ON THE ACTIVE LAYER<br />

D.W. Riseborough and CR. Burn<br />

PERENNIAL DISCHARGE OF SUBPERMAFROST GROUNDWATER IN TWO<br />

SMALL DRAINAGE BASINS, YUKON, CANADA<br />

R.O. Van Everdingen<br />

WETLAND RUNOFF REGIME IN NORTHERN CANADA<br />

Woo, M.K.<br />

STREAMFLOW CHARACTERISTICS OF THE QINGHAI<br />

(NORTHERN TIBETAN) PLATEAU<br />

Yang, Zhengniang and Woo, Ming-hm<br />

RATIONAL EXPLOlTATION AND UTILIZATION OF GROUND WATER IN<br />

PERMAFROST REGION OF THE MT.DA-XINGANLING AND MT.XIAO-<br />

XINGANLING, NORTHEAST CHINA<br />

Zheng, Qipu<br />

615<br />

618<br />

622<br />

628<br />

633<br />

639<br />

644<br />

650<br />

656<br />

PERIGLACIAL PHENOMENA, GEOCRYOLOGY<br />

GROUNDWATER PROTECTION IN THE PERMAFROST ZONE<br />

V.Ye. Afanusenko and V.P. Volkova<br />

MINERO-CRYOGENIC PROCESSES<br />

A. L. Ahumada<br />

UPFREEZING IN SORTED CIRCLES, WESTERN SPITSBERGEN<br />

S. Prestrud Anders<strong>on</strong><br />

TEPHRAS AND SEDIMENTOLOGY OF FROZEN ALASKAN LOESS<br />

J.E. Beget<br />

MORPHOLOGICAL FEATURES OF THE ACTIVE ROCK GLACIERS IN THE<br />

ITALIAN ALPS AND CLIMATIC CORFSLATIONS<br />

S. Bell<strong>on</strong>i, M. Pemni and C. Smiraglia<br />

659<br />

661<br />

666<br />

672<br />

678

OBSERVATIONS ON NEAR-SURFACE CREEP IN PERMAFROST, EASTERN<br />

Melville ISLAND, ARCTIC CANADA 683<br />

L.P. Bennett and HM. French<br />

OBSERVATIONS ON AN ACTIVE LOBATE ROCK GLACIER, SLIMS RIVER<br />

VALLEY, ST, ELIAS RANGE, CANADA<br />

W. Blumstengel & SA. Harris<br />

GENERAL MOISTENING OF THE AREA AND INTENSITY OF CRYOGENIC<br />

PROCESSES<br />

NF. Bosibv<br />

THERMOKARST LAKES AT MAYO, YUKON TERRITORY, CANADA<br />

CR. Burn and M.W. Smith<br />

LOESS AND DEEP THERMOKARST BASINS IN ARCTIC ALASKA<br />

L.D. Carter<br />

A FIRST APPROACH TO THE SYSTEMATIC STUDY OF THE ROCK<br />

GLACIERS IN THE ITALIAN ALPS<br />

A. Cart<strong>on</strong>, F. Dramis, and C. Smiraglia<br />

GEOCRYOLOGY OF The CENTRAL ANDES AND ROCK GLACIERS<br />

A.E. Corte<br />

689<br />

695<br />

700<br />

706<br />

712<br />

718<br />

ROCK GLACIERS IN THE SOURCE REGION OF URUMQI RIVER, MIDDLE<br />

TIAN SHAN, CHINA<br />

Cui, Zhijiu and Zhu, Cheng<br />

SEASONAL FROST MOUNDS IN AN EOLIAN SAND SHEET NEAR S<strong>on</strong>dre<br />

Stromfjord W. GREENLAND<br />

J.W.A. Dijhns<br />

PINGOS IN ALASKA: A REVIEW 734<br />

0 J. Ferrians, Jr.<br />

REGULARITIES IN FORMING THE DISCONTINUITY OF A CRYOGENIC<br />

SERIES 740<br />

S.M. Fotiev<br />

ROCK GLACIER RHEOLOGY A PRELIMINARY ASSESSMENT 744<br />

JR. GiamIino and JD. Vitek<br />

THE USE OF MICROBIOLOGICAL CHARACTERISTICS OF ROCKS IN<br />

GEOCRYOLOGY 749<br />

D A. Gilichinsky, G M. Khlebnibva, D.C. Zvyagintsev,<br />

D.C. Fetiorov-Davydov and NN. Kudryavtseva<br />

THERMIC OF PERMAFROST ACTIVE LAYER - SPITSBERGEN 754<br />

A. Gluza, J. Repelewska-Pekalowa and K. Dabrowski<br />

724<br />

728

SOIL FORMATION PALEOGEOGRAPHIC ASPECTS IN YAKUTIYA<br />

S.V. Gubin<br />

AEROPHOTOGRAMMETRICAL MONlTORING OF ROCK GLACIERS<br />

W. Haeberli and W. Schmid<br />

SURFACE SOIL DISPLACEMENTS IN SORTED CIRCLES, WESTERN<br />

SPITSBERGEN<br />

B. Hallet, S. Prestrud Anders<strong>on</strong>, C.W. Stubbs and E. Carringt<strong>on</strong> Gregory<br />

MICROMORPHOLOGY AND MICROFABRICS OF SORTED CIRCLES,<br />

JOTUNHEIMEN, SOUTHERN NORWAY<br />

C. Harris and JD. Cook<br />

CRYOSTRATIGRAPHTC STUDIES OF PERMAFROST, NORTHWESTERN<br />

CANADA<br />

D.E. Harry and H.M. French<br />

THAW LAKE SEDIMENTS AND SEDIMENTARY ENVIRONMENTS<br />

D.M. Hopkins and J.G. Kidd<br />

PERIGLACIAL SOIL Structures IN SPITSBERGEN AND IN CENTRAL<br />

EUROPA<br />

A. Jahn<br />

CONTINUOUS PERSISTENCE OF THE PERMAFROST ZONE DURING THE<br />

QUATERNARY PERIOD<br />

EM. Katas<strong>on</strong>ov<br />

PROBLEM OF INTEGRAL INDEX STABILlTY OF Ground COMPLEX OF<br />

PERMAFROST<br />

VP. Kovalbv and P.F. Shvetsov<br />

ICE WEDGE GROWTH IN NEWLY AGGRADING PERMAFROST, WESTERN<br />

Arctic COAST, CANADA<br />

J. Ross Mackay<br />

HEAT FLOW AND PECULIARlTIES OF CRYOLlTHOZONE IN WESTERN<br />

SIBERIA<br />

VP. Melnikov, VN. Devyatkin and Y.P. Bevzenko<br />

MICROTOPOGRAPHIC THERMAL CONTRASTS, NORTHERN ALASKA<br />

F.E. Nels<strong>on</strong>, SJ. Outcalt, KM, Hinkel, D.F. Murray and B.M. Murray<br />

FROST MOUNDS IN Kaffioyra AND HERMANSENOYA,<br />

NW SPITSBERGEN, AND THEIR ORIGIN<br />

W. Niewiarowski and M. Sinkiewicz<br />

CONTEMPORARY FROSTACITONONDIFFERENTORIENTEDROCKWALLS:<br />

AN EXAMPLE FROM THE SWISS JURA MOUNTAINS<br />

A. Pancza and J.-Cl. Ozouf<br />

759<br />

764<br />

770<br />

776<br />

784<br />

790<br />

796<br />

801<br />

805<br />

809<br />

815<br />

819<br />

824<br />

830

,<br />

, I<br />

GEOCRYOGENIC Slope Caves in The SOUTHERN CASCADES<br />

FL. Perez<br />

TRACES OF ICE IN CAVES: Evidence of FORMER PERMAFROST<br />

A. Pissart, B. Van Vliet-Lame, C. Ek and E. Juvigne<br />

THE THEORY OF CRYOLITHOGENESfS<br />

AJ. Popov<br />

ORIGIN OF MASSIVE GROUND ICE ON TUKTOYAKTUR PENINSULA,<br />

NORTHWEST Territories CANADA: A REVIEW OF Stratigraphic<br />

AND GEOMORPHIC EVIDENCE 850<br />

VA. Rampt<strong>on</strong><br />

ANDES SLOPE Asymmetry DUE TO Geliflucti<strong>on</strong><br />

M.C. Regairaz<br />

THE DEVELOPMENT OF DEPRESSED-CENTRE ICE-WEDGE POLYGONS IN<br />

THE Northernmost UNGAVA PENINSULA, QUEBEC, CANADA 862<br />

M. Seppala, J. Gray and J. Richard<br />

The UPPER HORIZON OF PERMAFROST SOILS 867<br />

Yu L. Shur<br />

FROST SHATTERING OF ROCKS IN The LIGHT OF POROSITY 872<br />

R. Uwinoka and P. Nieminen<br />

FLUVIO-AEOLIAN INTERACTION In A REGION OF CONTINUOUS<br />

* ,<br />

PERMAFROST<br />

J. Vandenberghe and J. Van Huissteden<br />

Regularities OF FORMING SEASONALLY CRYOGENIC GROUND 882<br />

EA. Vtyurina<br />

Observati<strong>on</strong>s OF SORTED.CIRCLE Activity CENTRAL ALASKA 886<br />

J.C. Walters<br />

Patterned GROUND GEOLOGIC CONTROLS, MENDOZA, ARGENTINA 892<br />

WJ. Wayne I(<br />

LANDSLIDE MOTION IN DISCONTINUOUS PERMAFROST 897<br />

S.C. Wilbur and J.E. Beget<br />

THE CHARACIERISTIC OF CRYOPLANATION LANDFORM IN THE<br />

Interior OF area QINGHAI-XIZANQ PLATEAU , < 903<br />

Zhang, Weixin, Shi, Shengmn, Chen, Fahu and Xu, Shuying<br />

THE PREDICTION OF PERMAFROST ENERGY STABILITY 906<br />

LA. Zhigarew and 0.Yu. Parmuzina<br />

834<br />

840<br />

846 '<br />

856<br />

876

VOLUME 2: ENGINEERING<br />

SITE INVESTIGATIONS AND Terrain ANALYSES,<br />

SUBSEA PERMAFROST<br />

BOREHOLE INVESTIGATIONS OF THE Electrical PROPERTIES OF<br />

FROZEN SILT<br />

SA. Arc<strong>on</strong>e and A J. Delaney<br />

PERMAFROST AND Terrain Preliminary MONITORING RESULTS,<br />

NORMAN WELLS PIPELINE CANADA<br />

M.M. Burgess<br />

CONTRIBUTION TO THE STUDY OF THE Active LAYER IN THE AREA<br />

AROUND CENTRUM LAKE, NORTH EAST GREENLAND<br />

M. Chir<strong>on</strong> and J.-F. Loubiere<br />

SEASONAL VARIATIONS IN RESISTIVITY AND TEMPERATURE IN<br />

Disc<strong>on</strong>tinuous PERMAFROST<br />

A. Delaney, P. Sellmann and S. Arc<strong>on</strong>e<br />

PERMAFROST CONDITIONS IN THE SHORE AREA AT SVALBARD<br />

0. Gregersen and T. Eidsmoen<br />

CORE DRILLING THROUGH ROCK GLACIER-PERMAFROST<br />

W. Haeberli, J. Huder, H.-R. Keusen, J. Pika and H. Rdthlisberger<br />

REMOTE Sensing LINEAMENT STUDY IN NORTHWESTERN ALASKA<br />

Huang, SL, and N. Lozano<br />

THERMAL EVIDENCE FOR AN ACTIVE LAYER ON THE Seabottom OF<br />

THE CANADIAN BEAUFORT SEA SHELF<br />

J A. Hunter HA. MacAulay, S.E. Pullan. R.M. Gagne RA. Burns and RL. Good<br />

FOUNDATION CONSIDERATIONS FOR Siting AND DESIGNING THE RED<br />

DOG MINE MILL FACILlTES ON PERMAFROST<br />

T.G. Krzavinski, T.A. Hammer and G.G. Booth<br />

ELECTRIC PROSPECting OF INHOMOGENEOUS FROZEN MEDIA<br />

V;V: Kuskov<br />

PREDICI'ION OF PERMAFROST THICKNESS BY THE 'TWO POINT" METHOD<br />

I.M. Kutasov<br />

THE USE OF GROUND PROBING RADAR IN THE DESIGN AND MONITORING<br />

OF WATER RETAINING EMBANKMENTS INPERMAFROST 971<br />

P.T. Lafleche A.S. Judge and JA. Pil<strong>on</strong><br />

PEAT FORMATION IN SVALBARD<br />

J. Lag<br />

910<br />

916<br />

922<br />

927<br />

933<br />

937<br />

943<br />

949<br />

955<br />

961<br />

965<br />

977

PERMAFROST GEOPHYSICAL INVESTIGATION AT THE NEW AIRPORT<br />

SITE OF KANGIQSUALUJJUAQ, Northern QUEBEC, CANADA 980<br />

M.K. Seguin, E. Gahe M. Allardand K. Ben-Mibud<br />

D.C. RESISTIVITY ALONG THE COAST AT PRUDHOE BAY, ALASKA 988<br />

P.V. Sellmann, A J. Delaney and SA. Arc<strong>on</strong>e<br />

EM SOUNDINGS FOR MAPPING COMPLEX GEOLOGY IN THE<br />

PERMAFROST TERRAIN OF NORTHERN CANADA<br />

AX. Sinhu<br />

MAPPING AND ENGINEERING-GEOLQGIC EVALUATION OF KURUMS 1000<br />

AJ. Tyurin, NN. Romanovsky and D.O. Sergqev<br />

Development AND THAWING OF ICE~RICH PERMAFROST AROUND<br />

CHILLED PIPELINES MONITORED BY RESISTANCE GAUGES 1004<br />

R.O. Van Everdingen and L.E. Carls<strong>on</strong><br />

THE ORIGIN OF PATTERNED GROUNDS IN N.W. SVALBARD 1008<br />

B. Van Vliet-Lanoe<br />

THE STATISTICAL ANALYSIS ON FROST HEAVE OF SOILS IN<br />

SEASONALLY GROUND FROZEN AREA 1014<br />

Wang, Jianguo and Xie, Yinqi<br />

DISCONTINUOUS PERMAFROST MAPPING USING THE EM-31<br />

D.S. Washburn and A. Phukan<br />

994<br />

1018<br />

A DISCUSSION ON MAXIMUM SEASONAL FROST DEPTH OF GROUND 1024<br />

Xu, Ruiqi, Pang, Guoliang and Wang, Bingcheng<br />

PRINCIPLES FOR COMPILING AN ATLAS OF SEASONAL FROST<br />

Penetrati<strong>on</strong> JILIN, CHINA (1: 2000000) 1026<br />

Zhang, Xing, Li, yinr<strong>on</strong>g and S<strong>on</strong>g, Zhengyuan<br />

GEOTECHNICAL Properties FROST HEAVE PARAMETERS<br />

SEGREGATION FREEZING OBSERVED IN WELDED TUFF BY OPEN<br />

SYSTEM FROST TEST HEAVE<br />

1030<br />

Akagawa,Satoshi, Goto, Shigem and Saito,Akira<br />

SOME ASPECTS OF SOILS ENGINEERING PROPERTIES IMPROVEMENT<br />

DURING DAM CONSTRUCTION 1036<br />

G.F. Bianov, V.. Makarov and EL. Kadkinu<br />

FROST HEAVE FORCES ON H AND PIPE FOUNDATION PILES 1039<br />

J.S. Buska and J.B. Johns<strong>on</strong>

THAW Settlement OF FROZEN SUBSOILS IN SEASONAL FROST<br />

REGIONS<br />

Cheng, Enyuan and Jiang, H<strong>on</strong>giu<br />

TENSILE ADFREEZING STRENGTH BETWEEN SOIL AND FOUNDATION<br />

Ding, Jingkang, Lou, Anjin and Yang, Xueqin<br />

Interacti<strong>on</strong> BETWEEN A Laterally LOADED PILE AND FROZEN SOIL<br />

L. Domaschuk, L. Franss<strong>on</strong> and DH. Shields<br />

CHOICE OF Parameters OF IMPACT BREAKAGE OF FROZEN SOILS<br />

AND ROCKS<br />

AJ. Fedulov and V... Labustin<br />

FROST HEAVE CHARACTERISTICS OF SALINE SOILS AND CANAL<br />

DAMAGE<br />

Feng, Ting<br />

MECHANICAL PROPERTIES OF FROZEN SALINE CLAYS<br />

T. Furuberg and A.-L. Berggren<br />

DECREASED SHEAR STRENGTH OF A Silty SAND Subjected TO FROST<br />

G.P. GiSford<br />

THEORETICAL Froblems OF CRYOGENIC GEOSYSTEM Modelling<br />

S.E. Grechishchev<br />

USE OF GEOTEXTILES TO MITIGATE FROST HEAVE IN SOILS<br />

K. Henry<br />

VOLUME OF FROZEN GROUND STRENGTH TESTING<br />

LN. Khrustalev and G.P. Pustovoit<br />

MECHANICAL FROZEN ROCK-FILL PROPERTIES AS SOIL STRUCTURE<br />

YaA. Kr<strong>on</strong>ik, AN. Gavrilov and VN. Shramkova<br />

A STUDY OF FROST HEAW IN LARGE U-SHAPED<br />

Li, Anguo<br />

CONCRETE CANALS<br />

FROST HEAVING FORCE ON THE FOUNDATION OF A HEATING BUILDING<br />

Liu, H<strong>on</strong>gxu<br />

FROST HEAVE IN SALINE-SATU'RATED FINE-GRAINED SOILS<br />

B.T.D. Lu, ML. Le<strong>on</strong>ard and L. Mahar<br />

EFFECT OF Variable THERMAL PROPERTIES ON FREEZING WITH AN<br />

UNFROZEN WATER CONTENT<br />

VJ. Lunardini<br />

DEVELOPMENT AND APPLICATION PRACTICE OF METHODS FOR<br />

PRELIMINARY THAWING OF PERMAFROST SOILS IN FOUNDATIONS<br />

E.S. Maksimenko<br />

1051<br />

1056<br />

1060<br />

1066<br />

1071<br />

1078<br />

1085<br />

1091<br />

1096<br />

1102<br />

1106<br />

1110<br />

1116<br />

1121<br />

1127<br />

1133

SECONDARY CREEP INTERPRETATIONS OF ICE RICH PERMAFROST<br />

E.C. McRoberts<br />

PHASE RELAXATION OF THE WATER IN FROZEN GROUND SAMPLES<br />

V.P. Melnikov, L.S. Podenko and A.G. Zavodovski<br />

STANDARD METHOD FOR PILE LOAD TESTS IN PERMAFROST<br />

R J. Neukirchner<br />

CRYOGENIC HEAVE UNDER FREEZING OF ROCKS<br />

VL. Nevecherya<br />

EFFECTIVE LIFE IN CREEP OF FROZEN SOILS<br />

KR . Parameswaran<br />

HORIZONTAL FROST HEAVE FORCE ACTING ON THE RETAINING<br />

WALL IN SEASONAL Frozen REGIONS<br />

Shui, Tieling and Na, Wenjie<br />

DYNAMIC LOAD EFFECT ON Settlement OF MODEL PILES IN<br />

FROZEN SAND<br />

D.L. Stelzer and OB. Andersland<br />

TANGENTIAL FROST-HEAVING FORCE OF THE REINFORCED CONCRETE<br />

PILE AND CALCULATION OF PREVENTING IT FROM PULLING UP DUE<br />

TO FROST HEAVE<br />

Sun, Yuiiang<br />

BEHAVIOUR OF LONG PILES IN PERMAFROST<br />

A. Theriault and B. Ludanyi<br />

INVESTIGATION ON TANGENTIAL FROST HEAVING FORCES<br />

T<strong>on</strong>g, Changiiang, Yu, Ch<strong>on</strong>gyun and Sun, Weimin<br />

STRESS-STRAIN BEHAVIOUR OF FROZEN SOILS<br />

S.S. Vyalov R.V. Maximyak, VN. Razbegin, M.E. Slepak and A.A. Chapayev<br />

FROST HEAVING FORCES ON FOUNDATIONS IN SEASONALLY<br />

FROZEN GROUND<br />

Xu, Shaoxin<br />

ON THE DISTRIBUTION OF FROST HEAVE WITH DEPTH<br />

Zhu, Qiang<br />

TRIAXIAL COMPRESSIVE STRENGTH OF FROZEN SOILS UNDER<br />

CONSTANT STRAIN RATES<br />

Zhu, Yuanlin and D.L. Carbee

\<br />

Geotechnical ENGINEERING, PIPELINE CONSTRUCTION<br />

LONG TERM Settlement TEST (3 YEARS) FOR CONCRETE PILES IN<br />

PERMAFROST<br />

B A. Bredesen, 0. Puschmann and 0. Gregersen<br />

TANGENTIAL FROST HEAVING FORCE ON REINFORCED CONCRETE<br />

PILES OFHIGHWAY BRIDGE<br />

Dai, Huimin and Tian, Deting<br />

PERFORMANCE OF TWO EARTHFILL DAMS AT LUPIN, N.W.T<br />

S. Dufour and I. Holubec<br />

ROADWAY EMBANKMENTS ON WARM <strong>Permafrost</strong> PROBLEMS AND<br />

REMEDIALTREATMENTS<br />

D. Esch<br />

REMEDIAL SOLUTIONS FOR Pipeline THAW SETTLEMENT<br />

J.E. Ferrell and H. P. Thomas<br />

A FROZEN FOUNDATION ABOVE A TECHNOGENIC TALK<br />

I.E. Guryanov<br />

ASSESSMENT OF KEY DESIGN ASPECTS OF A 150 FOOT HIGH EARTH<br />

DAM ON WARM PERMAFROST<br />

TA. Humme< T.G. Krzewinski and G.G. Booth<br />

PERMAFROST SLOPE DESIGN FOR A BURIED OIL PIPELINE<br />

A J. Hanna and E.C. McRoberts<br />

A METHOD FOR Calculating THE Minimum BURIED DEPTH OF<br />

BUILDING FOUNDATIONS<br />

Jiang, H<strong>on</strong>gju and Cheng, Enyuan<br />

PROTECTION OF WARM PERMAFROST USING CONTROLLED<br />

SUBSIDENCE AT NUNAPITCHUK Airport<br />

E.G. Johns<strong>on</strong> and G.P. Bradley<br />

THERMAL PERFORMANCE OF A SHALLOW UTILIDOR<br />

F.E. Kennedy, G. Phetteplace, N. Humist<strong>on</strong> and V. Prabhakar<br />

CONSTRUCTION OF HYDROS IN COLD CLIMATE: ACHIEVEMENTS AND<br />

PROBLEMS<br />

Ld. Kudoyarov and NF. Kriv<strong>on</strong>ogova<br />

1206<br />

1212<br />

1217<br />

1223<br />

1229<br />

1235<br />

1242<br />

1247<br />

1253<br />

1256<br />

1262<br />

1268<br />

STUDY OF SOME GEOTECHNICAL ASPECTS EFFECTING CONSTRUCTION<br />

IN GLACIAL REGIONS OF HIMALAYAS 127 1<br />

D.S. Laljii and R.C. Pathak<br />

A SUBGRADE COOLING AND ENERGY RECOVERY SYSTEM<br />

EL. L<strong>on</strong>g and E. Yarmak Jr.<br />

1277

LONG TERM PLATE LOAD TESTS ON MARINE CLAY IN SVEA. ~Z SVALBARD -<br />

1282<br />

T. Lunne and T. Eidsmoen<br />

MELIORATION OF SOILS OF CRYOLITHOZONE<br />

0.K Makeev<br />

EMBANKMENT FAILURE FROM CREEP OF PERMAFROST FOUNDATION<br />

SOIL<br />

R. McHattie and D. Esch<br />

1288<br />

1292<br />

CONSTRUCTION OF EARTH Structures IN PERMAFROST AREAS BY<br />

HYDRAULIC METHODS<br />

P.I. Melnikov, Chang, R.V. G.P. Kuzmin and A.V. Yakovlev<br />

STORAGE TANK FOUNDATION DESIGN, PRUDHOE BAY, ALASKA, U.S.A.<br />

B. Nidowicz, D. Bruggers and V. Manikian<br />

STUDIES OF PIPELINE INTERACTION WITH HEAVING SOILS<br />

S.Yu. Pamtuzin, AD. Perelimiter and I.Ye. Naidenok<br />

YUKON RIVER BANK STABILIZATION: A CASE STUDY<br />

CH. Riddle, J.W. Ro<strong>on</strong>ey and S.R. Bredthauer<br />

AIRPORT RUNWAY DEFORMATION AT NOME, ALASKA<br />

J.W. Ro<strong>on</strong>ey, J.F. Nix<strong>on</strong>, C.H. Riddle and E.G. Johns<strong>on</strong><br />

PHYSICAL MODEL STUDY OF ARCTIC PIPELINE SETTLEMENT<br />

T.S. Vins<strong>on</strong> and A.C. Palmer<br />

BETHEL AIRPORT, CTB PAVEMENT PERFORMANCE ANALYSIS<br />

CL. vita, J.W. Ro<strong>on</strong>ey and T.S. Vins<strong>on</strong><br />

A NEW METHOD FOR PILE TESTING AND DESIGN IN<br />

PERMANENTLY-FROZEN GROUNDS<br />

S.S. Vyalov and Yu.S. Mirenburg<br />

CLASSIFICATION OF FROZEN HEAVE OF GROUND FOR HYDRAULIC<br />

ENGINEERING IN SEASONAL FROZEN REGIONS<br />

Xie, Yinqi, Wung, Jianguo and Han, Weijun<br />

RETAINING WALL WITH ANCHOR SLABS USING IN COLD REGION<br />

Xu, Bomeng and Li, Changlin<br />

THAW STABILIZATION OF ROADWAY EMBANKMENTS<br />

J.P. Zarling, W.A. Braley and D.C. Esch<br />

METHOD FOR CALCULATING FROST HEAVE REACTION FORCE IN<br />

SEASONAL FROST REGION<br />

Zhou, Youcai<br />

1298<br />

1301<br />

1307<br />

1312<br />

1318<br />

1324<br />

1330<br />

1336<br />

1341<br />

1346<br />

1352<br />

1358

ENGINEERING, -PETROLEUM, -MINING, -MUNICIPAL<br />

COLD-MIX ASPHALT CURING AT LOW Termperatures<br />

ANS. Beaty and P.M. Jarrett<br />

PROGNOSIS OF SOIL TEMPERATURE AT THE AREA UNDER<br />

CONSTRUCTION<br />

AL. Chekhovskyi<br />

PRESSURE IN RELATION TO FREEZING OF WATER-CONTAINING<br />

MASSES IN A CONFINED SPACE<br />

M.M. Dubina<br />

ENVIRONMENT PROTECTION FOR MINING ENTERPRISES IN<br />

PERMAFROST REGIONS<br />

EA. Elchaninov<br />

ARCTIC MINING IN PERMAFROST<br />

H.M. Giegerich<br />

APPLIED STUDY OF PREVENTING STRUCTURES FROM FROST DAMAGE<br />

BY USING DYNAMIC CONSOLIDATION<br />

Han, Huaguang and Euo, Mingzhu<br />

EFFECT OF HEATING ON FROST DEPTH BENEATH FOUNDATIONS OF<br />

BUILDING<br />

H<strong>on</strong>g, Yuping and Jiang, H<strong>on</strong>gju<br />

PREDICTION OF PERMAFROST THAWING AROUND MINE WORKINGS<br />

VYu. Izaks<strong>on</strong>, E.E. Petrov and A.V. Samokhin<br />

EXPERIENCE IN CONSTRUCTION BY STABILIZATION METHOD<br />

LN. Khrustalm and V.V. Nikiforov<br />

GEOCRYOLOGICAL STUDIES FOR RAILWAY CONSTRUCTION<br />

(STATE, Primary TASKS)<br />

V.G. K<strong>on</strong>dratyev AA. Korolyev, MI. Karlinski, EM. Timopheev<br />

and PN. Lugovoy<br />

VENTILATED SURFACE FOUNDATIONS ON PERMAFROST SOILS<br />

NB. Kutvitskqa and MR. Gokhman<br />

Results OF RESEARCHES AND EXPERIENCE OF HYDRAULIC MINING<br />

OF FROZEN ROCKS<br />

N.P. Lavrov, G.Z. Perlshtein and V.K. Samyshin<br />

OFFSHORE SEAWATER TREATING PLANT FOR WATERFLOOD PROJECT,<br />

PRUDHOE BAY OIL FIELD, ALASKA, U.S.A.<br />

V. Manikian and J.L. Machemehl<br />

1363<br />

1368<br />

1372<br />

1377<br />

1382<br />

1388<br />

1393<br />

1397<br />

1403<br />

1407<br />

1413<br />

1417<br />

1422

DEVELOPING A THAWING MODEL FOR SLUDGE FREEZING BEDS<br />

C. J. Martel<br />

ROCK MECHANICS RELATED TO COAL MINING IN PERMAFROST ON<br />

SPITZBERGEN<br />

A.M. Myrvang<br />

SETTLEMENTS OF THE FOUNDATIONS ON SEASONALLY Freezing<br />

SOILS<br />

V.O. Orlov and V.V. Fwsov<br />

REGULARITIES OF THERMAL AND MECHANICAL INTERACTION<br />

BETWEEN Culverts AND EMBANKMENTS<br />

NA. Peretrukhin and AA. Topekha<br />

Methods OF QUANTITATIVE VALUATION OF REGIONAL HEAT<br />

RESOURCES FOR PREPARATION OF PERMAFROST PLACER Deposits<br />

TO MINING<br />

G.Z. Perlshtein and V.E. Kapranov<br />

Stability OF ROAD SUBGRADES IN THE NORTH OF WEST SIBERIA<br />

A.G. Polmvsky and Yu.M. Lyvovitch<br />

REFLECTION SEISMIC EXPLORATION AND DATA PROCESSING IN COLD<br />

REGIONS<br />

F. Parturas<br />

PROBLEMS OF ARCTIC ROAD CONSTRUCTION AND MAINTENANCE IN<br />

FINLAND<br />

S. Saarelainen and J. Vaskelainen<br />

SOME ASPECTS OF FREEZING THE ICE PLATFORMS<br />

BA. Suveliev and DA. Latalin<br />

SLOPE STABILlTY IN ARCTIC COAL MINES<br />

AX. Sinha, M. Sengupta and T.C. Kinney<br />

THE RESISTANCE TO FROST HEAVE OF VARIOUS CONCRETE CANAL<br />

LINING<br />

S<strong>on</strong>g, Baoqing, Fan, Xiuting and Sun, Kehan<br />

THE BARROW DIRECT BURY Utilities SYSTEM DESIGN<br />

J.E. Thomas, P.E.<br />

COLD CRACKING OF Asphalt PAVEMENT ON HIGHWAY<br />

Tian, Deting and Dai, Huimin<br />

AIRPORT Network AND HOUSING CONSTRUCTION PROGRAMMES<br />

IN NORTHERN QUEBEC, CANADA<br />

C. Tremblay and G. Dork

FROST DAMAGE OF ENCLOSURE AND ITS MEASURE FOR PREVENTING<br />

FROST HAZARD<br />

Wang, G<strong>on</strong>gshan<br />

APPLICATION OF LIME STABILIZATION ON HIGHWAY PERMAFROST<br />

REGION, QINGHAI-XIZANG PLATEAU<br />

Wang, Qing-tu,Wu, Jing-min and Liu, Jian-du<br />

INVESTIGATION AND TREATMENT FOR SLOPE-SLIDING OF RAILWAY<br />

CUTTING IN PERMAFROST AREA<br />

Wang, Wenbao<br />

MODEL TEST TO DETERMINE Thawing DEPTH OF EMBANKMENT IN<br />

PERMAFROST REGION<br />

Ye, Bayou, T<strong>on</strong>g, Zhiquan, Lou Anjin and Shang, Jih<strong>on</strong>g<br />

STUDIES ON THE PLASTIC-FILM-ENCLOSED FOUNDATION OF SLUICE<br />

GATES AND ITS APPLICATION<br />

Yu, Bofang, Qu, Xiangmin and Jin, Naicui<br />

GEOCRYOLOGICAL BLOCK OF OIL AND GAS PRODUCING AND<br />

TRANSPORTING GEOTECHNICAL SYSTEMS<br />

YF. Zakharov, Y.Y. Podborny and GJ. PUSH<br />

1507<br />

1511<br />

1515<br />

1520<br />

1526<br />

1531

BOREHOLE INVESTIGATIONS OF THE ELECTRICAL<br />

PROPERTIES OF FROZEN SILT<br />

S.A. Arc<strong>on</strong>e and AJ. Delaney<br />

U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering Laboratory<br />

SYNOPS IS<br />

The dielectric c<strong>on</strong>stant and attenuati<strong>on</strong> rate of short radiowave pulses in frozen<br />

Fairbanks silt have been measured between boreholes.12 m deep and spaced between 4.4 and 17.6<br />

m. The ranges for volumetric ice c<strong>on</strong>tent and temperature were 44 to 79% and -6.0 (surface, early<br />

April) to -0.7-C (bottom) respectively. The pulses lasted approximately 30 ns, had a power spectrum<br />

centered near 100 MHz, and were transmitted and received at the same depth. Dielectric<br />

c<strong>on</strong>stants were determined from the propagati<strong>on</strong> time delay of the leading edge and there was no<br />

significant dispersi<strong>on</strong>. Attenuati<strong>on</strong> rates (dB/m) were determined by comparing signal levels<br />

received between different borehole pairs and were adjusted €or geometric spreading losses. C<strong>on</strong>current<br />

borehole dc resistivity measurements allowed estimates of the separate c<strong>on</strong>tributi<strong>on</strong>s of<br />

various loss mechanisms. The results show the dielectric c<strong>on</strong>stant to vary between 4.3 and 7.0<br />

and to correlate well with the volumetric ice c<strong>on</strong>tent, but not with temperature Average attenuati<strong>on</strong><br />

rates at any particular depth varied between 1.4 and 4.0 dB/m. The lowest values occurred<br />

in the secti<strong>on</strong>s with the higher ice c<strong>on</strong>tent. No more than 0.8 dB/m could be ascribed to c<strong>on</strong>ductive<br />

absorpti<strong>on</strong> losses, suggesting that scattering is an important loss mechanism.<br />

INTRODUCTION<br />

Short-pulse radar operating between 50 and 500<br />

MHz is often used for explorati<strong>on</strong> in northern<br />

regi<strong>on</strong>s (e.g., Annan and Davis, 1976; Davis et<br />

al,, 1976; Arc<strong>on</strong>e and Delaney, 1984). The<br />

freezing of soil decreases the wave attenuati<strong>on</strong><br />

at these frequencies found in the same<br />

materials when thawed. Knowledge of the<br />

electrical properties of frozen soils, which<br />

determines wave velocity and attenuati<strong>on</strong> rate,<br />

is thus essential to the interpretati<strong>on</strong> of<br />

radar records in northern climates.<br />

The electrical resistivity p of frozen soils<br />

str<strong>on</strong>gly depends <strong>on</strong> the mobility of charge<br />

carriers al<strong>on</strong>g networks of unfrozen water,<br />

given poorly c<strong>on</strong>ducting minerals. Complex dielectric<br />

permittivity E* depends <strong>on</strong> the relative<br />

proporti<strong>on</strong>s and individual properties of<br />

mineral matter, air, ice and unfrozen water<br />

(e.g., Hoekstra and Delaney, 1974; Delaney and<br />

Arc<strong>on</strong>e, 1984). Grain size and temperature<br />

help determine the amount of unfrozen water,<br />

which exists near particle surfaces. The<br />

water c<strong>on</strong>tent determines how many channels<br />

form (usually a small volumetric percentage is<br />

needed to coat all soil particles) and how<br />

many voids can be filled with water or ice.<br />

Temperature mainly determines the percentage<br />

of interstitial water that forms ice; as<br />

temperature decreases below O’C the percentage<br />

of unfrozen water decreases (Tice et al.,<br />

1978). Electrical properties also depend <strong>on</strong><br />

frequency, which is c<strong>on</strong>trolled by several<br />

relaxati<strong>on</strong> processes alhoeft, 1977). In this<br />

research the bandwidth was sufficiently narrow<br />

to avoid such dependence.<br />

Field investigati<strong>on</strong>s of frozen soil properties<br />

in the 50- to 500”Hz range have not been<br />

91 0<br />

extensive. Arc<strong>on</strong>e and Delaney (1982a, 1984)<br />

and Delaney and Arc<strong>on</strong>e (1984) , using fixed<br />

frequency and pulse techniques, have found the<br />

dielectric c<strong>on</strong>stant E’ to vary between 3 and<br />

12 for silt between about -2 and -12’C, with<br />

volumetric ice c<strong>on</strong>tent varying from 0 to over<br />

80X. Annan and Davis (1 976) and Annan (1976)<br />

have calculated c’ from signal propagati<strong>on</strong><br />

times for clayey soils with high ice c<strong>on</strong>tent,<br />

and found some values less than 3.2, that of<br />

pure ice. N<strong>on</strong>e of the above works c<strong>on</strong>tains<br />

data <strong>on</strong> signal attenuati<strong>on</strong>. Indirect methods<br />

such as modeling or Low frequency resistivity<br />

measurements (e.g., Arc<strong>on</strong>e and Delaney, 1982a)<br />

can be employed to estimate attenuati<strong>on</strong> rates.<br />

The objective of this research was to<br />

measure in situ the dielectric permittivity of<br />

frozen silt and to correlate values with soil<br />

temperature and ice c<strong>on</strong>tent. High ice c<strong>on</strong>tent<br />

silt is comm<strong>on</strong> in interior Alaska. The time<br />

delays of pulses transmitted between boreholes<br />

at a site in Fairbanks. Alaska, and attenuati<strong>on</strong><br />

rates calculated from comparis<strong>on</strong>s of<br />

signal loss between different borehole pairs<br />

were used to compute the real part E’ of the<br />

dielectric permittivity. Measurements of dc<br />

resistivity allowed attenuati<strong>on</strong> mechanisms to<br />

be estimated. The data reported here are’from<br />

two years for late March - early April when<br />

the ground was entirely frozen.<br />

EQUIPMENT AND DATA PROCESSING<br />

Electromagnetic<br />

A c<strong>on</strong>trol unit manufactured by the Xadar<br />

Company (Electromagnetic Reflecti<strong>on</strong> Profiling<br />

System, model 1316) operated a pair of borehole<br />

antennas manufactured by the GSSI

Company. The unit is intended €or radar subsurface<br />

profiling with transmit and receive<br />

antennas close together, but may be used with<br />

the antennas at any separati<strong>on</strong>. The pulse<br />

repetiti<strong>on</strong> frequency was 50 kHz. The signals<br />

received are sequentially sampled to c<strong>on</strong>vert<br />

the VHF frequencies to the audio range for<br />

digital or analog recording over <strong>on</strong>e of severa1<br />

scan lengths, ranging from 43 to 2000 ns.<br />

The scans were linearly stacked to reduce incoherent<br />

noise and then stored <strong>on</strong> magnetic<br />

tape. An exp<strong>on</strong>ential gain was applied OVeK<br />

the first quarter of the scan, after which it<br />

remained c<strong>on</strong>stant. An overall system gain was<br />

also used. Data were later transferred to a<br />

computer for playback and graphic display.<br />

Fig. 1<br />

-3b ' Ib 20 io 40 ' 5b '<br />

Time (ns)<br />

Frequency (Hz)<br />

Typical transmitted 'wavelet (top)<br />

and its associated amplitude and<br />

phase spectra.<br />

A typical radiated pulse shape and its associated<br />

Fourier spectrm are ahown in Figure<br />

1. Both transmit and receive antennas do not<br />

radiate uniformly in the radial directi<strong>on</strong>, although<br />

pulse shape is maintained in all directi<strong>on</strong>s.<br />

Measurements made in air revealed that<br />

received amplitude could vary as much as 2.6<br />

dB, depending <strong>on</strong> the azimuthal orientati<strong>on</strong> of<br />

the antennas. However, this could cause <strong>on</strong>ly<br />

a small adjustment in the measured attenuati<strong>on</strong><br />

rate (in dB/m) when divided by the propagati<strong>on</strong><br />

distances. Antenna orientati<strong>on</strong> in the boreholes<br />

was inhibited by the attached ropes and<br />

cables, but was impossible to determine as the<br />

antennas would rotate when being lowered.<br />

Time delay was calibrated by recording pulse<br />

transmissi<strong>on</strong>s between antennas separated in<br />

air at measured distances. The absolute zero<br />

time reference for any borehole pair was<br />

determined by first measuring the time delay<br />

difference td between air transmissi<strong>on</strong>s over<br />

a distance equal to the borehole spacing, and<br />

that between the boreholes (both recordings<br />

within 1 minute) at the maximum depth of 11.5<br />

m. The borehole separati<strong>on</strong> divided by the<br />

free space velocity c = 30 cm/ns was then<br />

added to td to give the zero time refrrence.<br />

This procedure fixed the positi<strong>on</strong> of<br />

the absolute time reference <strong>on</strong> our recordings<br />

for both years of measurement. Temperatures<br />

recorded throughout the year at 11.5-m depth<br />

revealed no seas<strong>on</strong>al changes, thus verifying<br />

an assumpti<strong>on</strong> of no dielectric changes at the<br />

11.5-m depth. Yearly calibrati<strong>on</strong>s were<br />

required to compensate for drift in the zero<br />

time reference (approximately 1 ns/hour)<br />

because of changes in dc bias levels within<br />

the course of a day or between years.<br />

Signal amplitude calibrati<strong>on</strong> was determined by<br />

the gain settings and signal level recorded<br />

for each transmissi<strong>on</strong>. Attenuati<strong>on</strong> rates<br />

between a borehole pair were determined by<br />

comparing the amplitudes received between that<br />

pair with those measured between a closer<br />

reference pair, for which total attenuati<strong>on</strong><br />

was generally less; 13 combinati<strong>on</strong>s of pairs<br />

were utilized. The rates are therefore based<br />

<strong>on</strong> relative measurements to eliminate system<br />

losses. Absolute calibrati<strong>on</strong>s were impossible<br />

because of the unknown values of initial<br />

signal strength at the antennas.<br />

Resistivity<br />

A string of electrodes was attached to a 3.8-<br />

cm-diameter plastic (ABS) pipe and inserted<br />

darn a separate borehole, which was then backfilled<br />

with wet silt and allowed to refreeze.<br />

The electrodes were separated by 30 cm and an<br />

apparent resistivity pa was computed using<br />

the formula for a Wenner array embedded in a<br />

homogeneous earth<br />

pa = 4na V/I ,<br />

where a is the electrode spacing and V and I<br />

are the measured voltage and injected current,<br />

respectively. The quantity Pa is an integrati<strong>on</strong><br />

over a radius of about 0.7a and equals<br />

the real resistivity for homogeneous earth. A<br />

more complete descripti<strong>on</strong> of this experiment<br />

(including discussi<strong>on</strong>s of c<strong>on</strong>tact resistance<br />

and pipe effects) with data for 12 m<strong>on</strong>ths is<br />

given by Delaney et al. (in press).<br />

Temperature<br />

Temperature T was measured at 30-cm levels using<br />

a thermistor probe slowly lowered down a<br />

separate borehole filled with ethylene glycol.<br />

The thermistor (Omega 400 series) was<br />

calibrated to 0.01 "C. Readings were made <strong>on</strong> a<br />

battery-operated voltmeter after equilibrium<br />

was established at each level. The thermistor<br />

was weighted to facilitate lowering. An<br />

entire run lasted about 45 minutes.<br />

Electromagnetic Data Reducti<strong>on</strong><br />

The time delay and peak amplitude of each<br />

pulse transmissi<strong>on</strong> allowed computati<strong>on</strong> of the<br />

com lex index of refracti<strong>on</strong> n* = n' - in" (i =<br />

Jd) from which E* = E' - ic" = nX2 could be<br />

calculated. Time delays were measured at the<br />

leading edge of the wavelet and, witli the<br />

known borehole separati<strong>on</strong>, determined n'. The<br />

positi<strong>on</strong> of the Leading edge was determined<br />

visually to about f 0.5 ns, which generally<br />

91 1

gives an error of less than 0.1 in E' . The<br />

c<strong>on</strong>eistency in oscillati<strong>on</strong> periods for all<br />

wavelets precluded the presence of dispersi<strong>on</strong><br />

and the possibility that leading edge<br />

velocities were not characteristic of the<br />

str<strong>on</strong>gest: frequency of the wavelets. <strong>on</strong>ly the<br />

leading edge could be used because the wavelet<br />

1et)gth and specttm in the air reference<br />

(centered at approximately 140 MHz) was<br />

different than in the ground (100 MHz).<br />

The attenuati<strong>on</strong> rate 4 (dBfm) was computed by<br />

comparing the peak received signal strength A,<br />

for <strong>on</strong>e pair with that for a closer, reference<br />

hole pair A . After adjusting the ratio APIAI<br />

for geometric spreading losses, a is then<br />

found from the formula<br />

B - 20 log<br />

(A2fA1) f (2)<br />

Access Roud<br />

where AZ is the difference in separati<strong>on</strong><br />

between the two borehole pairs. The imaginary<br />

part of the refractive index is then<br />

n" = pcf (8.68.2sf) = 0.055 Rff (3)<br />

where f is,the str<strong>on</strong>gest frequency of transmissi<strong>on</strong><br />

(in hundreds of MHz). The comp<strong>on</strong>ents<br />

of. E* are then<br />

and<br />

E' = 7 2<br />

I (4)<br />

E" - 2n'n'' . (5)<br />

The quantity n" proved small enough to allow<br />

E' = nr2 to within + 0.04, which is within the<br />

error of the time measurement.<br />

Signal attenuati<strong>on</strong> other than geometric<br />

spreading is caused by resistive or dipolar<br />

dispetai<strong>on</strong>al losses, or scattering. Delaney<br />

and Arc<strong>on</strong>e (1984) have shown the dipolar<br />

comp<strong>on</strong>ent of E" to be in the range 0.1-0.2 for<br />

very high ice c<strong>on</strong>tent Fairbanks silt, which at<br />

100 MHz, gives 0.4-0.8 dBfm for an E' = 5.<br />

Attenuati<strong>on</strong> rates due to material resistivity<br />

p are computed from the formula<br />

H<br />

Fig. 2<br />

Borehole layout at the Farmer's Loop<br />

Road test facility. T and p are the<br />

temperature and resistivity electrode<br />

string boreholes.<br />

be obtained because freeze-back of the core<br />

barrel to the hole wall c<strong>on</strong>stantly occurred at<br />

the near 0°C temperature of the soil. C<strong>on</strong>sequently,<br />

<strong>on</strong>ly augered cuttings were obtained<br />

from which gravimetric water c<strong>on</strong>tent was<br />

measured. Massive ice was not encountered in<br />

any of the holes.<br />

0.0<br />

$, = 4.34icJe' b p = 1636foJ;' . (6)<br />

SITE DESCRIPTION AND PREPARATION<br />

The investigati<strong>on</strong> was c<strong>on</strong>ducted at the<br />

Farmer's Loop Road test facility of USACRREL<br />

in Fairbanks, Alaska. The soil type to several<br />

tens of meters depth is retransported<br />

eolian silt (PmC. 1958). Previous investigati<strong>on</strong>s<br />

here (Arc<strong>on</strong>e et al., 1978; Arc<strong>on</strong>e and<br />

Delaney. 1982b3) have reported values for<br />

ground resistivity and the active layer<br />

dielectric c<strong>on</strong>stant. Generally, volumetric<br />

ice c<strong>on</strong>tent (discussed later) exceeds 50% and<br />

active layer depth is 70-100 cm. An organic<br />

mat covers the surface. The highest and lowest<br />

ground temperatures occur in early spring<br />

and late summer respectively.<br />

Six holes (Fig. 2) were drilled to approximately<br />

12-m depth and cased with 3-in. (7.62-<br />

cm) diameter ABS plastic pipe, capped and<br />

sealed at the bottom. Core samples could not<br />

Fig. 3<br />

Calibrati<strong>on</strong> data for computing volumetric<br />

ice c<strong>on</strong>tent from gravimetric<br />

water c<strong>on</strong>tent.<br />

Equivalent volumetric ice c<strong>on</strong>tent was calculated<br />

using a cal.ibrati<strong>on</strong> curve (Fig. 3)<br />

matched to data from cores obtained at a'nearby<br />

site at Fox, Alaska. and from other studies<br />

at Fox and Farmer's Loop Road (Arc<strong>on</strong>e and<br />

Delaney, 1982b). The equati<strong>on</strong>s for the curves<br />

assumed a eilt density of 2.7 gfcm3, a porosity<br />

of 0.44 (Hoekstra and Delaney, 1974) and<br />

that Site f Rei1t + Bair = 1 where 8 is<br />

volumetric c<strong>on</strong>tent. Above saturati<strong>on</strong>, Sair<br />

= 0. The volumetric unfrozen water c<strong>on</strong>tent<br />

was not measured in the cores nor c<strong>on</strong>sidered<br />

in the theory. Thie causes an error of a few<br />

percent in the saturati<strong>on</strong> calculati<strong>on</strong>s because<br />

91 2

several grams of unfrozen water can exist per<br />

100 8 of silt (Tice et al., 1978) below<br />

-0.J C, the highest temperature encountered in<br />

the boreholes.<br />

E'<br />

4 5 6<br />

RESULTS AND DISCUSSION<br />

Pulse transmissi<strong>on</strong>s were recorded at 1-m depth<br />

intervals. The antennas were raised simultaneously<br />

from a bottom datum plane established<br />

by surface leveling. Nine borehole pairs<br />

were investigated for E' and Figure 4 shows a<br />

cy ical record. The two widest pairs (borehoyes<br />

2 to 6 and 2 to 3, Fig. 2) gave limited<br />

or no discernible signal above the noise<br />

level.. Generally, transmissi<strong>on</strong>s in the top<br />

3 m between each pair were severely affected<br />

by the noise generated by the sequential<br />

sampling (see Equipment and Data Processing)<br />

of nearby FM radio stati<strong>on</strong>s, as is evident in<br />

Figure 4. N<strong>on</strong>e of the inter-borehole paths<br />

crossed a third borehole and rarely was an<br />

event sec<strong>on</strong>dary to the dlrect transmissi<strong>on</strong><br />

observed for any pair but the closest. The<br />

correlati<strong>on</strong>s between propagati<strong>on</strong> characteristics<br />

and ice c<strong>on</strong>tent are created statistically<br />

because no soil samples were obtained between<br />

boreholes.<br />

x<br />

Cl t I<br />

Fig. 4<br />

I<br />

Depth (m)<br />

Typical inter-borehole pulse<br />

transmissi<strong>on</strong>s, in this case between<br />

holes 4 and 5.<br />

Figures 5a and b show the temperature and<br />

eice profiles. The temperature profile was<br />

d<strong>on</strong>e <strong>on</strong> April 4, 1986, with an approximate<br />

snow cover of 30 cm and before any extensive<br />

thaw periods had begun. Temperature was<br />

c<strong>on</strong>stant below 6 m at -0.75'C. ice varied<br />

between 48 and 78% and no formati<strong>on</strong>s of massive<br />

ice were found in any of the holes. The<br />

e ce profile for hole 6 shows the largest<br />

fluctuati<strong>on</strong>s. This profile will not be<br />

included in subsequent averaging and comparis<strong>on</strong>s<br />

as the hole was too distant to receive<br />

any transmissi<strong>on</strong>s.<br />

Ffgure 5c compares 1985-86 average values of<br />

E with the average Aice at each depth for<br />

holes 1 to 5. The lowest values of E' correlate<br />

with the highest ice c<strong>on</strong>tents and vice<br />

versa. At these high values of Aice, not<br />

:-<br />

E<br />

Y<br />

c<br />

c<br />

19<br />

0<br />

Fig. 5 Temperature (a), volumetric ice (b) ,<br />

and average dielectric c<strong>on</strong>stant<br />

(holes 1 to 5), and volumetric ice<br />

profiles (c) .<br />

<strong>on</strong>ly have all voids been filled with ice, but<br />

the ice volume exceeds tne porosity of dry<br />

silt. C<strong>on</strong>sequently, samples with gFeater silt<br />

c<strong>on</strong>tent have the higher values of E because<br />

of the unfrozen water between or adsorbed <strong>on</strong><br />

the silt particles. If the value of,eice<br />

were to decrease below saturati<strong>on</strong>, E wauLd<br />

again decrease because air would c<strong>on</strong>tinually<br />

replace water. C<strong>on</strong>sequently, there is a<br />

double-valued dependency of E' <strong>on</strong> @ice.<br />

This double-valued dependency of E' <strong>on</strong><br />

is illustrated in Figure 6, which superimposes<br />

the dielectric data of Figure 5c (al<strong>on</strong>g with<br />

data €or holes 4 to 5) <strong>on</strong> (revised) theoretical<br />

curves and other experimental data for<br />

frozen silt given by Delaney and Arc<strong>on</strong>e<br />

(1984). The solid curve is based <strong>on</strong> both<br />

laboratory and field data taken at temperatures<br />

near -JOG. The crossed data points are<br />

from Figure 5c and the dark triangles are the<br />

averages for just holes 4 and 5, both of which<br />

were sampled to calculate eice. Either the<br />

set of dark triangles or that of crosses<br />

agrees well with the previous observati<strong>on</strong>s,<br />

although the temperature range for the borehole<br />

data was -0.75 to -4.O"C. This temper.ature<br />

insensitivity must be related to the <strong>on</strong>ly<br />

temperature-sensitive comp<strong>on</strong>ent, the unfrozen<br />

water, either through a significant reducti<strong>on</strong><br />

in the volumetric fracti<strong>on</strong> of silt at high ice<br />

c<strong>on</strong>tents, or through a decrease in its own<br />

permittivity in the natural state.<br />

913

Fig. 6<br />

P<br />

0 20 40 60 80 IO0<br />

Water C<strong>on</strong>tent (%I<br />

(0) Laboratory (-7')<br />

(0) Tunnel (-7')<br />

(a) Pure Ice<br />

(at ter V<strong>on</strong> Hippel 1954)<br />

Dielectric c<strong>on</strong>stant vs. volumetric<br />

water c<strong>on</strong>tent data compared with previws<br />

investigati<strong>on</strong>s and theoretical<br />

results (dashed curves - explained in<br />

text).<br />

The hypothesis that the temperature insensitivity<br />

is due to the reduced volumetric fracti<strong>on</strong><br />

of silt at high ice c<strong>on</strong>tents is tested by the<br />

theoretical curves in Figure 6 which are<br />

derfved from a simple volumetrically based<br />

dielectric mixing formula:<br />

cause the temperature insensitivity that we<br />

observe from the data. An overestimate of E'<br />

for supercooled unfrozen water does not seem<br />

possible in view of the high permittivities<br />

measured <strong>on</strong> well-mixed Laboratory samples<br />

(Delaney and Arc<strong>on</strong>e, 1982). More sophisticated<br />

models based <strong>on</strong> structural c<strong>on</strong>siderati<strong>on</strong>s<br />

would give a better match to the data,<br />

but are not expected to alter the c<strong>on</strong>clusi<strong>on</strong><br />

of a theoretical temperature sensitivity.<br />

It seems, then. that the reduced temperature<br />

sensitivity is due to an inability of the silt<br />

to have reached its €ull capacity for retaining<br />

unfrozen water. It is unlikely that ice<br />

lens growth has occurred at the expense of the<br />

unfrozen water in the already frozen silt in<br />

view of the high degree of saturati<strong>on</strong> and the<br />

results of Tice et al. (in press). The possibility<br />

that not all silt particles ever came<br />

in c<strong>on</strong>tact with unfrozen water is also unlikely<br />

because it is probable that this retransported<br />

secti<strong>on</strong> originally formed as an aggrading<br />

saturated active layer. Therefore, at<br />

this time we can <strong>on</strong>ly speculate <strong>on</strong> the possibility<br />

of organics or molecular diffusi<strong>on</strong> as<br />

agents of reducti<strong>on</strong> in unfrozen water c<strong>on</strong>tent.<br />

Figure 7a plots resistivity versus depth. The<br />

values range from 1000 to over 12,000 ohm-m<br />

and are representative of silt to a radial<br />

distance of about 20 cm from the electrode<br />

string (Delaney et al,, in press). Also<br />

plotted are the equivalent attenuati<strong>on</strong> rates<br />

6, associated with these values. The lowest<br />

value (- 1000 ohm-m) gives a maximum pP of<br />

about 0.75 dB/m. Generally, however, most<br />

values below the 4-m depth are Less than about<br />

0.3 dB/m.<br />

p, x I0-j ohm-m<br />

4 8 I2<br />

0<br />

2<br />

4<br />

The index m is for the comp<strong>on</strong>ents: ice, unfrozen<br />

water, air and dry silt. The E' values<br />

of air, silt and ice are 1.0, 4.0 and 3.2,<br />

respectively, the dry sample porosity is 0.44<br />

and the silt density is 2.1 g/cm3. The unfrozen<br />

water is assigned an E' of 84 at -0.75"C<br />

and 60 at -7.O'C (Stogryn and Desargent,<br />

1985), values which alter the previous versi<strong>on</strong><br />

of this curve (Delaney and Arc<strong>on</strong>e, 1984) based<br />

<strong>on</strong> a value OE E' = 88. Curves (b) (-0.75'C)<br />

and (c) (-7.O"C) assume a capacity for unfrozen<br />

water c<strong>on</strong>tent of 4 g/100 g silt, while<br />

curve (a) (-0.75'C) assumes a value of 8.<br />

Recent data from Tice et al. (in press) based<br />

<strong>on</strong> nuclear magnetic res<strong>on</strong>ance nuggest that 8<br />

(-0.75'C) and 4 (-4 to -7'C) are more appropriate.<br />

Thus, the wide separati<strong>on</strong> of curves<br />

(a) and (c) near 60% water c<strong>on</strong>tent means that,<br />

theoretically, the reduced amount of silt in<br />

high ice c<strong>on</strong>tent secti<strong>on</strong>s is not sufficient to<br />

rr<br />

E 6<br />

Y<br />

f<br />

a<br />

B S<br />

IO<br />

14 I<br />

0 0.4 OB 1.2 0 2 . 4<br />

op (d B/m 1<br />

(dB/rn)<br />

Fig. 7<br />

Resistivity (dc) and its associated<br />

signal attenuati<strong>on</strong> rate (a), and<br />

average total attenuati<strong>on</strong> rates for<br />

two different years (b) ,<br />

914

Figure 7b plots the average propagati<strong>on</strong><br />

attenuati<strong>on</strong> rate measured at each depth for<br />

April 1985 and March 1986. Average rates are<br />

presented to give some compensati<strong>on</strong> for variati<strong>on</strong>s,due<br />

to changes in antenna orientati<strong>on</strong><br />

(0.23 dBJm at most) or to dielectric inhomoeneities<br />

near the antennas. Between 10 and<br />

f 3 comparis<strong>on</strong>s between borehole pairs were<br />

used to calculate each point. Averages above<br />

the 4-m depth are not given, either because of<br />

noise distorti<strong>on</strong>, or because too few signal<br />

levels could be read above the noise to give a<br />

meaningful average. The few values that could<br />

be calculated using borehole 6 are included in<br />

these averages. There is a general increase<br />

of attenuati<strong>on</strong> with depth, which correlates<br />

with the increase in T and E' with depth and<br />

the decreasing eic values below 8 m. The<br />

minimum average vafue of 1.40 dB/m is well<br />

above the maximum rate of 0.75 dBJm due to<br />

c<strong>on</strong>ductive losses (Fig. 7a). The lack of<br />

dispersi<strong>on</strong> seen in all waveforms (e.g. Fig. 4)<br />

suggests that dielectric relaxati<strong>on</strong>-is not a<br />

significant attenuati<strong>on</strong> mechanism. We are<br />

thus left with scattering as the important<br />

loss mechanism. The largest values of R seen<br />

below 8 rn may therefore indicate greater inhomogeneity,<br />

as would also the decrease in<br />

eicg from such high values at 4-6 m. The<br />

maximum value of 4 dB/m gives n" = 0.22, which<br />

supplies an insignificant correcti<strong>on</strong> to the<br />

caLculati<strong>on</strong> of E' as per eq 4.<br />

CONCLUSIONS<br />

Inter-borehole pulse propagati<strong>on</strong> can be an<br />

effective means of generally assessing volumetric<br />

ice c<strong>on</strong>tent. in frozen silt. Although<br />

E' does not seem sensitive to temperacure in<br />

the cases studied, such sensitivity could<br />

exisv in other silt deposits, depending<br />

probably <strong>on</strong> lithologic or historical factors<br />

not currently uyderstood. The double-valued<br />

dependency of E vs requires, however,<br />

other informati<strong>on</strong> to establish if Rice is<br />

greater OK less than about 40%. This can be<br />

d<strong>on</strong>e easily with a n<strong>on</strong>-c<strong>on</strong>tact surface or<br />

borehole resistivity technique such as double<br />

dipole magnetic inducti<strong>on</strong> (e.g., Arc<strong>on</strong>e et<br />

al., 1978). Values above 1000 ohm-m enerally<br />

indicate eice > 40%. It is not at alf clear<br />

that propagati<strong>on</strong> attenuati<strong>on</strong> rates could be<br />

used to diagnose the range of Aice because<br />

increasing losses caused by decreasing<br />

resistivity may be compensated for by less<br />

scattering due to increased homogeneity. The<br />

overall average of 2.3-2.6 dB/m found here<br />

means that separati<strong>on</strong>s greater than 20 m will<br />

need more power and more sophisticated signal<br />

processing than just stacking to assess ice<br />

c<strong>on</strong>tent with this technique.<br />

REFERENCES<br />

Annan, A P (1976).<br />

Density of ice samples from "Involuted Hill"<br />

test site, District of Mackenzie. Report of<br />

Activities, Part C, Geologic Survey of<br />

Canada, Paper 76-1C, 91-95.<br />

Annan, A P & Davis, J L (1976) . Impulse<br />

radar sounding in permafrost.<br />

Radio Science, (Il), 4, 383-394.<br />

91 5<br />

Arc<strong>on</strong>e, S A & Delaney, A J (1982a).<br />

ELectrical properties of frozen ground at<br />

VHF near Point Barrow, Alaska.<br />

IEEE Trans. <strong>on</strong> Geoscience and Remote<br />

Sensing, (GE-20), 4, 485-492.<br />

Arc<strong>on</strong>e, S A & Delaney, A J (1982b).<br />

Dielectric properties of thawed active<br />

layers overlying permafrost using radar at<br />

VHF .<br />

Radio Science, (1 7), 3, 618-626.<br />

Arc<strong>on</strong>e, S A & Delaney, A J (1984) .<br />

Radar investigati<strong>on</strong>s above the trans-Alaska<br />

pipeline near Fairbanks. CRREL Report<br />

84-27, U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and<br />

Engineering Laboratory, Hanover, NH, 1-15.<br />

Arc<strong>on</strong>e, S A, Sellmann, P V & Delaney, A J<br />

(1978).<br />

Shallow electromagnetic geophysical<br />

investigati<strong>on</strong>s of permafrost. Proc 111<br />

Inter C<strong>on</strong>f <strong>Permafrost</strong>, (I), 501-507,<br />

Edm<strong>on</strong>t<strong>on</strong>, Alberta.<br />

Davis, J L, Scott, W J, Morey, R M & Annan, A<br />

P (1976) , Impulse radar experiments <strong>on</strong><br />

permafrost: neat Tuktoyaktuk, N.W.T.<br />

Canadian Journal of Earth Sciences, (1 3) ,<br />

1584-1 590.<br />

Delaney, A J & Arc<strong>on</strong>e, S A (1 984) .<br />

Dielectric measurements of frozen silt using<br />

time domain reflectometry.<br />

Cold Regi<strong>on</strong>s Science and Technology, (9),<br />

39-46.<br />

Delaney, A J, Sellmann, P V & Arc<strong>on</strong>e, S A<br />

(in press).<br />

Seas<strong>on</strong>al variati<strong>on</strong>s in resistivity and<br />

temperature in disc<strong>on</strong>tinuous permafrost near<br />

Fairbanks, Alaska. Submitted to V Inter<br />

C<strong>on</strong>f <strong>Permafrost</strong>, Tr<strong>on</strong>dheim.<br />

Hoekstra, P & Delaney, A J (1974).<br />

Dielectric properties of soils at UHF and<br />

microwave frequencies.<br />

Journal of Geophysical <strong>Research</strong>, (75), 11<br />

1699-1 708.<br />

Olhoeft, G R (1977). Electrical properties<br />

of natural clay permafrost.<br />

Canadian Journal of Earth Sciences, 14, p.<br />

16-24.<br />

Pew&. T L (1958).<br />

Geology of the Fairbanks (D-2) Quadrangle,<br />

Alaska. U.S. Geological Survey geological<br />

quadrangle map GQ-I 10.<br />

ogryn, A & Desargent, G (1985) .<br />

The dielectric properties of brine in sea<br />

ice at microwave frequencies.<br />

IEEE Trans Geoscience and Remote Sensing,<br />

(AP-33), 5, 40-46.<br />

ce, A R, Burrows, C W & Anders<strong>on</strong>, D M<br />

(1978) .<br />

Phase compositi<strong>on</strong> measurements <strong>on</strong> soils at<br />

very high'watrr c<strong>on</strong>tents by the pulsed<br />

nuclear magnetic res<strong>on</strong>ance technique. In<br />

Moisture and Frost-Related Soil Properties,<br />

Transportati<strong>on</strong> <strong>Research</strong> Board, Nati<strong>on</strong>al<br />

Academy of Sciences,<br />

Tice, A R, Black, P & Berg, R (1988).<br />

Unfrozen water c<strong>on</strong>tents measurements of<br />

undisturbed and remolded soils from the<br />

Northwest Alaska Pipeline Company frost<br />

heave facility as determined by pulsed<br />

nuclear magnetic res<strong>on</strong>ance. CRKEL report<br />

(in press). U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong><br />

and Engineering Laboratory, Hanover, NH.<br />

V<strong>on</strong> Hippel, A R, Ed. (1954).<br />

Dielectric materials and applicati<strong>on</strong>s.<br />

J Wiley, New Pork.

PERMAFROST AND TERRAIN PRELIMINARY MONITORING RESULTS,<br />

- NORMAN WELLS PIPELINE, CANADA<br />

M.M. Burgess<br />

<strong>Permafrost</strong> <strong>Research</strong>, Geological Survey of Canada, Energy, Mines and Resources, Ottawa, Canada<br />

SYNOPSIS The 869 km Norman Wells oil pipeline, owned by Interprovincial Pipe Line (NW) ttd.<br />

(IPL). traverses the disc<strong>on</strong>tinuous permafrost z<strong>on</strong>e of Northwestern Canada. A fully buried, small<br />

diameter (324 mm) line transporting initially chilled oil was designed for operati<strong>on</strong> in the<br />

thaw-sensitive terrain al<strong>on</strong>g the route. Operati<strong>on</strong> began in April 1985. M<strong>on</strong>itoring of the thermal<br />

regime at thirteen locati<strong>on</strong>s al<strong>on</strong>g the route forms a major comp<strong>on</strong>ent of a l<strong>on</strong>g term cooperative<br />

government-IPL permafrost and terrain research and m<strong>on</strong>itoting program, Observati<strong>on</strong>s to the end of<br />

March I987 indicate that mean annual pipe tempetatures, which range from O°C to 5OC, are generally<br />

>O°C both within the widespread disc<strong>on</strong>tinuous permafrost terrain in the north and the sporadic<br />

disc<strong>on</strong>tinuous permafrost terrain in the south. Mean annual ground temperatures <strong>on</strong> the right-of-way<br />

(ROW) a.t 1 m depth, several metres from the trench, range from -2O to +Q0C and are <strong>on</strong> average 1.5<br />

degrees colder than mean annual pipe temperatures. Mean annual ground temperatures off-ROW at a<br />

depth of 1 m range from - 3 O to +3'C and are <strong>on</strong> average 1 degree colder than those <strong>on</strong>-ROW. Maximum<br />

surface settlement observed <strong>on</strong> the ROW at the sites has reached up to 80 cm outside the trench<br />

area, and over 100 cm in the vicinity of the trench.<br />

INTRODUCTION<br />

The Norman Wells pipeline. the Eirst completely<br />

buried oil pipeline in the disc<strong>on</strong>tinuous<br />

permafrost z<strong>on</strong>e of Canada. began operati<strong>on</strong> in<br />

April 1985. The 869 km l<strong>on</strong>g, 324 mm diameter,<br />

pipeline is owned by Interprovincial Pipe Line<br />

(NW) Ltd. (IPL) and carries oil south from Esso<br />

Resources' Norman Wells, N.W.T. oilfield to<br />

Zama, northwestern Alberta (Figure 1). The<br />

terrain c<strong>on</strong>diti<strong>on</strong>s encountered al<strong>on</strong>g the route<br />

(Kay et al.. 1983) necessitated the development<br />

of special design features and mitigative<br />

measures in order to minimize terrain impacts<br />

(Nati<strong>on</strong>al Energy Board, 1981: IPL, 1982) and to<br />

assure pipe integrity under possible c<strong>on</strong>diti<strong>on</strong>s<br />

of thaw settlement or frost heave. Details of<br />

the design are outlined by Nix<strong>on</strong> et al. (1984).<br />

Nix<strong>on</strong> and Pick (1986). McRoberts et al. (1985).<br />

and Wishart and Fooks (1986).<br />

Features selected to limit energy exchange with<br />

the surrounding terrain include 1). winter<br />

right-of-way (ROW) clearance, prlor to<br />

c<strong>on</strong>structi<strong>on</strong>. generally to 25 m. maximizing the<br />

use of previous cutlines, 2) c<strong>on</strong>structi<strong>on</strong> in<br />

winter, using temporary roads, 3) oil chilled<br />

to near O°C before delivery to fPL; no further<br />

refrigerati<strong>on</strong> in passing through three pump<br />

stati<strong>on</strong>s (kms 0. 336 and 585). 4) small<br />

diameter, shallow burial (average depth,<br />

excluding roach, 1 m) and generally uninsulated<br />

pipe, and 5) wood chip insulati<strong>on</strong> of thaw<br />

sensitive slopes. The Norman Wells pipeline<br />

was not expected to directly cause "significant<br />

thawing of the underlying permafrost" (Nix<strong>on</strong> et<br />

dl., 1984) compared to the slow thawing to<br />

depths of 6 m resulting from clearing and<br />

c<strong>on</strong>structi<strong>on</strong>. Hence its general descripti<strong>on</strong> as<br />

an "ambient" ground temperature pipeline.<br />

91 6<br />

Fig.1 Locati<strong>on</strong> o f Norman Wells Pipeline<br />

and M<strong>on</strong>itoring Sites<br />

The Norman Wells project provides an important<br />

opportunity to observe the behaviour of the<br />

pipeline and ROW and to assess the impact of<br />

c<strong>on</strong>structi<strong>on</strong> and operati<strong>on</strong> of the first. small<br />

diameter, buried oil pipeline in permafrost.

This paper discusses observati<strong>on</strong>s <strong>on</strong> 1) the<br />

pipe thermal regime. 2) the ground thermal<br />

reglme. and 3) the surface settlement recorded<br />

at 13 joint government and industry m<strong>on</strong>itoring<br />

sites from c<strong>on</strong>structi<strong>on</strong> to the end of the<br />

sec<strong>on</strong>d year of pipeline operati<strong>on</strong> (March 1987).<br />

PERMAFROST AND TERRAIN RESEARCH AND MONITORING<br />

The l<strong>on</strong>g term permafrost and terrain research<br />

and m<strong>on</strong>itoring (PTRM) program wae established<br />

under an Envir<strong>on</strong>mental Agreement signed in 1982<br />

between the federal department of Indian and<br />

Northern Affairs (INAC) and IPL. A major<br />

comp<strong>on</strong>ent of the PTRM program, developed in<br />

cooperati<strong>on</strong> with the federal department of<br />

Energy, Mines and Resources (EMR), involves the<br />

detailed quantificati<strong>on</strong> of changes in the<br />

ground thermal regime and geomorphic c<strong>on</strong>diti<strong>on</strong>s<br />

at instrumented sites.<br />

Table I<br />

Site Locati<strong>on</strong>s and Descripti<strong>on</strong>s<br />

84-1 Pump stati<strong>on</strong> 1 0.02 Ice-rich silty clay in widespeead permafrost<br />

BE-2 Cany<strong>on</strong> crset (previously cleared cut line from the 1960s)<br />

A 19.0 Level terrain. frozen till with low ice<br />

c<strong>on</strong>tent in widespread permafrost<br />

B 19.3<br />

C 19.6<br />

84-3 Great Bear River<br />

A 79.2<br />

B 79.4<br />

East-tacing permafrost slope with a 1 m<br />

insulating wood chip cover<br />

wart-eacing permaftost slope with erosi<strong>on</strong><br />

c<strong>on</strong>trol berms<br />

(Joint IPL site)<br />

Stratigraphically camplex ice-rich alluvial<br />

terrace deposits in widespread permafrost<br />

Cliff-Cop lacustrine deposits: aeallan<br />

veneer<br />

85-7 Table nountain<br />

(joint IPL site]<br />

A 271.2 loe-rich lacustrine plain (old seismic line)<br />

8 212.0 Icn-rich lacustrine vlain (recent helipad<br />

olearing at top of north-facing sLape)-<br />

C 271.3 Ice-rich lacustrine plain<br />

84-4 Trail River<br />

(unfrozen terrain aftor l<strong>on</strong>g frozen stretch)<br />

a 478.0 Unfrozen saturated sands ana silt# in duns<br />

hollow<br />

B<br />

478.1 Dry Bands and silts in dune crnst<br />

85-8 Manner's Creek (rapidly changing permafrost c<strong>on</strong>diti<strong>on</strong>s)<br />

A 557.8 Thin peat, thick (10 m) permafrost<br />

B 558.2 Thick peat (2.7 ml. thin (I m) permafroet<br />

C<br />

558.3 Thin peat (1 m). thin (1 m) petmaErosC<br />

85-9 Pump Stati<strong>on</strong> 3 583.3 Unfrozen granular soils after frozen secti<strong>on</strong><br />

85-10 M4ckenzie Highway South<br />

a 588.3 Translti<strong>on</strong> from tecent helipad clearing in<br />

Unfrozen terrain to<br />

B 588.7 Thin (3 n) pe~mafrost with 2 m peat cover<br />

85-11 Moraine South 597.4 Thin (4 a) Perma1roBt in recent helipad<br />

85-12 Jean Marie Creek<br />

& 608.6 Thin unfrozen pear plateau<br />

B<br />

608.7 Thick ice-rich peat plateau: 4 m permaltost<br />

85-13 aadknife Hills<br />

A 682.2 Frozen (6 o) terrain eurroundinq largo een<br />

B 682.1 Frozen (6 m) tertain at edge of fen<br />

C 182.6 Unfrozen terrain in fen<br />

84-5 Petitot Rivar North<br />

Ir 783.0 Ice-rich peat (3.5 m): 15-18 m permafroat<br />

B<br />

783.3 Very thick icy peat (7 m); 1'2 m permafrost<br />

84-6 Petitot River South<br />

819.1 Thlck (5 D) ice-rich peat: 7 m permafrost<br />

Rote: All fences. unless otherwise indicated. are located io terrain<br />

newly cleared for the pipeline Row. site 85-13 is the <strong>on</strong>ly site which has<br />

not been set up in the "thermal fence" c<strong>on</strong>figurati<strong>on</strong>.<br />

Thermal instrumentati<strong>on</strong> installed at the PTRM<br />

sites has been laid out al<strong>on</strong>g <strong>on</strong>e mor e<br />

"thermal fences". In total there Yr'e 23<br />

fences, each of which typically c<strong>on</strong>sists of 5<br />

thermistor sensors placed <strong>on</strong> the external Wall<br />

of the pipe and a series of 4 boreholes. cased<br />

with PVC and instrumented with multithermistor<br />

cables. Two 5 m cables (10 sensors. 50 cm<br />

spacing) are located within a few metres of the<br />

pipe. Two 20 m cables c<strong>on</strong>tain 11 sensors<br />

spaced every 1 m near the surface and every<br />

2-3 m at depth; <strong>on</strong>e cable is installed <strong>on</strong> the<br />

ROW several metres (4-9) from the pipe. the<br />

other is set in the adjacent terrain off-ROW.<br />

The establishment of the thermal fences, the<br />

instturnentati<strong>on</strong> and the measurement programs<br />

are described in detail by Burgess et. al.<br />

(1986). Burgess (1987) and Pil<strong>on</strong> et al. (in<br />

prep. ). Topographic surveys, c<strong>on</strong>ducted<br />

annually at most' fences, record vertical<br />

movements in the ground surface to an accuracy<br />

of 10 cm over a 20 m x 20 m grid, using 2-3<br />

local benchmarks per site and a 2 m stati<strong>on</strong><br />

spacing.<br />

M<strong>on</strong>thly field trips emphasize the manual<br />

acquisiti<strong>on</strong> of thermal data for most fences.<br />

Automatic loggers (SeaData) also installed at 5<br />

fences record ground temperature cable readings<br />

several times daily. The m<strong>on</strong>thly data are<br />

published regularly as EMR open file reports<br />

(Burgess, 1.986 and 1987). Thermal c<strong>on</strong>diti<strong>on</strong>s<br />

across the ROW are complex especially at sites<br />

with different ages and degrees of vegetati<strong>on</strong><br />

removal and of ground surface disturbance.<br />

C<strong>on</strong>diti<strong>on</strong>s are dynamic, and may include 1)<br />

maintenance activities , 2) stati<strong>on</strong>ary or<br />

flowing water, 3 ) changing vegetati<strong>on</strong> cover, as<br />

well as 4) variable climatic c<strong>on</strong>diti<strong>on</strong>s.<br />

PIPE THERMAL REGIME<br />

Northern secti<strong>on</strong> (fences from km 0 to 272)<br />

<strong>Permafrost</strong> underlies about 75% of the terrain<br />

(Kay et al. 1983) and all of the 9 thermal<br />

fences in this secti<strong>on</strong>. M<strong>on</strong>thly pipe<br />

temperature6 recorded over time at the fences<br />

from km 19 to 272 (data from the fence at<br />

km 0.02 will be discussed separately) fall<br />

within the ranges plotted in Figure 2.<br />

Thirteen principal m<strong>on</strong>itoring sites, shown in<br />

Figures 1 and briefly described in Table I,<br />

were selected to 1) investigate the terrain<br />

resp<strong>on</strong>se to particular pipeline design features<br />

and mitigative measures, including areas of<br />

thaw sensitive terrain, frozen/unfrozen<br />

interfaces and a wood chip insulated slope, and<br />

2) represent the soil and ground ice c<strong>on</strong>diti<strong>on</strong>s<br />

al<strong>on</strong>g the route. An IPL geotechnical<br />

m<strong>on</strong>itoring program involves the instrumentati<strong>on</strong><br />

of 26 slopes; 17 with wood chip insulati<strong>on</strong>.<br />

Joint industry- government sites emphasize the<br />

study of other terrain c<strong>on</strong>diti<strong>on</strong>s.<br />

91 7<br />

Fiq.2 Pipe Temperatures - Northern Secti<strong>on</strong>

~~<br />

~~<br />

30<br />

10<br />

Pre-flow pipe temperatures (from 5 fences<br />

establishedin 1984) show a wider rangeand<br />

larger annual amplitude than post-flow,<br />

reflecting the natural diversity of the<br />

adjacent ground thermal regime. Pipe<br />

temperatures before flow were generally at any<br />

time in close agreement (within 1 degree) at<br />

each fence with the temperatures recorded <strong>on</strong><br />

the ROW at a depth of 1 m several metres from<br />

the trench. Individual plots comparing pipe<br />

temperature and ROW 1 m ground temperature at<br />

each fence are presented in MacInnes et al.(in<br />

prep.).<br />

After the pipeline came into operati<strong>on</strong>,<br />

differehces of 2-4 degKeeS were comm<strong>on</strong>ly<br />

observed between pipe temperatures and<br />

ROW<br />

ground temperatures at 1 m depth. Pipe<br />

temperatures at sites with multiple fences.<br />

which before flow had differed at a given time<br />

by up to 8 degrees from <strong>on</strong>e fence to the next,<br />

generally differ by less than I degree after<br />

flow. Figure 2 also illustrates the warmer<br />

winter pipe temperatures observed since oil<br />

began flowing.<br />

Table I1<br />

Mean Annual Temperatures (Pipe and Ground) and<br />

Surface Settlement After 2 Years of Operati<strong>on</strong><br />

PENCK (km) TRENCH AREA ROV OUTSIDE TRENCH AREA OFF-ROW<br />

Wean<br />

Mean<br />

Wean Pipe Range of 1 q Ground Range of 1 m mound<br />

Temp. Settlmment Temp. Settlemmnt Tsmp.<br />

(fm) L.C) (em) (*C)<br />

84-1 (0.02) -0.2 0 60 -0.9- 0 BO -2.3<br />

81-2A (19.0) 0.2 0 30<br />

0.1 0 - 20 -1.1<br />

84-26 (19.3) 0.1 0 - 30 -0.2 0 40 -2.5<br />

81-2C (19.6) 0.4 0 20<br />

1.3 0<br />

84-3R (19.2) 1.2 10 30 -1.0<br />

50 -1.2 0 - 50 -2.8<br />

84-38 (79.4) 0.9 0 - 20 0.5 0 20 -2.1<br />

85-YA (271.2) 0.6 10 70<br />

0.0 0 - 50<br />

-1.ow<br />

85-78 (272.0) 0.1 10 80<br />

-0.9 0 50 -I. I'<br />

85-lf 1272.3) 0.6 20 60<br />

-1.6 30 -1.1*<br />

ai-rA iiG.oi 2.4 0 - 50<br />

2.6 0 - io I,O<br />

sa-4s (470.1) 2.3 0 ~ 2.9 0 - 30 0.9<br />

85-EA [ssl.~) 1.8 10 - 1.0 -0.3 0 - 30 -0.1<br />

85-11B (558.2) 2.5 10 - LOO+ -0.5 0 - 40 -1.1<br />

85-ec (550.3) 1.n 10 110 -0.4 0 - 60 -0.3<br />

85-9 (583.31 a.9 0 - 20 3.6 0 ~ 2.5<br />

81-IOA (518.3) 4.8 0 50<br />

2.4 0<br />

85-108 (588.7) be@ 0 - 30 1.5<br />

loo+ 1.2 0 40 -0.1<br />

85-11 (597.4) 3.9 backfilled 2.8 0 a0<br />

0.1<br />

85-1ZA (608.6) 3.1 0 - 70 1.7 0 20 0.3<br />

115-128 (b011.7) 3.7 0 - loo* -0.8 0 - 50 -1.1<br />

84-5A (783.0) 1.9<br />

NIA<br />

0.4 N/A<br />

0.0<br />

84-58 (783.3) 1.9 NIA<br />

-0.1<br />

NIA -0.1<br />

81-6 (819.5) 1.8 NI4<br />

-0.2<br />

N/R 0.0<br />

NOTES :<br />

1) The Trench Area includes the trmnch and 2 m <strong>on</strong> either side of the pip.<br />

cantrelina. The BOW AT04 is thm reraindec Of the surveyed right-of-way.<br />

2) The range of settlement (en) decmrmined from the surface elevati<strong>on</strong><br />

SUKveys is dafinrd by the minimum and maximum amount obeerved. The<br />

OFF-BMI is not Covernd by thm nuKvey. 3) Pips tmaperatures shown are<br />

man annuals (average of the 5 pip. Sensors) calculated for the sec<strong>on</strong>d<br />

ycrf of oparati<strong>on</strong>, 1.e. April 1986 to mrch 1997. CaiC1Ilati<strong>on</strong>s were<br />

pmrrormed by curve fittinq to the approximate m<strong>on</strong>thly values.<br />

Interpolating weekly values and datermining 52 wesk mean^. 4) noan<br />

annual ground tbmpetaturms a ~ e the calculated values (sanm method of<br />

Ca1cUlati<strong>on</strong> as above) for the smc<strong>on</strong>d year of operati<strong>on</strong>. for the sensor at<br />

a nominal depth of 1 m (which is thm averaqe dapth of covmr oves the<br />

pipe). y N/A: not available since 4 sec<strong>on</strong>d survey from which ssZtlemmnt<br />

oould be calculatad hae nat yet been undertaksn. b) * : avmraqs of two<br />

cables: elmuhare <strong>on</strong>ly <strong>on</strong>e ground campecature Cable.<br />

Table I1 presents the calculated mean annual<br />

pipe temperatures (using the average of the 5<br />

sensors <strong>on</strong> the pipe) for each fence during the<br />

sec<strong>on</strong>d year of operati<strong>on</strong>. The calculated mean<br />

annual ground temperatures <strong>on</strong> the ROW, using<br />

the 1 m sensor at the deep borehole' several<br />

metres distant from the pipe. for the same time<br />

period, are included in Table 11. The 1 m<br />

sensor was selected for comparis<strong>on</strong> since this<br />

is the average depth of cover over the pipe.<br />

(Note: Since the ground temperature cables are<br />

in anchored PVC tubes, the absolute depth of<br />

91 8<br />

the 6enaors may change as the grouhd surface<br />

heaves or settles; the sensor spacing is<br />

however fixed. All references in this paper to<br />

L m sensor of 1 m depth are thus to ground<br />

temperatures at a nominal depth of 1 m.) Mean<br />

annual pipe temperatures are between Oo and<br />

+l0C at fences al<strong>on</strong>g the northern porti<strong>on</strong> of<br />

the route. The mean ROW ground temperatures,<br />

which are between -2- and +1OC, are <strong>on</strong> average<br />

about 1 degree colder.<br />

Pipe temperatures recorded at the Pump Stati<strong>on</strong><br />

site, km 0.02, were variable after start-up.<br />

During the first year of operati<strong>on</strong>, when the<br />

oil was chilled to about -2OC (Pick, 1986). the<br />

mean annual pipe temperature at the fence wa0<br />

about 0.6OC. The delivery temperature has<br />

since been -5OC and the mean annual pipe<br />

temperatur,e at the fence has dropped to -0.2OC.<br />

Southern secti<strong>on</strong> (fences from km 477 t o 820)<br />

In this secti<strong>on</strong> permafrost underlies<br />

approximately 25% of the terrain with numerous<br />

frozen/unfrozen interfaces. teaching a8 many as<br />

15/km (Kay et 81. 1983). The range of pipe<br />

temperatures recorded over time at the 14<br />

fences located in this porti<strong>on</strong> of the route are<br />

plotted in Figure 3. Pre-flow temperatures are<br />

not shown since most sites were established in<br />

1985 and <strong>on</strong>ly sparse data was gathered at the<br />

few 1984 sites.<br />

1985 1986<br />

J<br />

1987<br />

1 1 ,SI IJ, I 1 ,SI<br />

I<br />

1<br />

Fig.3<br />

Observed range of pipe temperatures<br />

a at m<strong>on</strong>itoring sltes from km 477 to 818<br />

Pipe Temperatures - Southern Secti<strong>on</strong><br />

Winter pipe temperatures have again been<br />

c<strong>on</strong>spicuously warmer since the pipeline has<br />

been in operati<strong>on</strong>. Table I1 indicates that all<br />

of the m<strong>on</strong>itoring fences, nine of which were<br />

originally underlain by permafrost, now have<br />

mean annual pipe temperatures well above O°C<br />

and between +a0 and +5OC. Mean annual ground<br />

temperatures recorded <strong>on</strong> the ROW several metres<br />

from the pipe, and listed in Table 11, range<br />

from -1 to +4OC. At the permafrost fences mean<br />

pipetemperatures are from 1.5 to 5 degrees<br />

warmer (average about 2.5) than the mean ROW<br />

ground temperatures.<br />

Pipe temperatures at any time are c<strong>on</strong>sistently<br />

2-3 degrees warmer at fence 10A (km 588.3) than<br />

at fence 9 (km 583.3); mean annual ptpe<br />

temperatures during the sec<strong>on</strong>d year of operati<strong>on</strong>

uere 2.5OC at fence 9 and 5.0°C at fence 10A.<br />

This increase may reflect the increase in oil<br />

temperature during pumping at Pump Stati<strong>on</strong> 3<br />

which is located between the two fences.<br />

General comments<br />

The mean annual pipe temperatures, in both<br />

secti<strong>on</strong>s. are <strong>on</strong> average 1.5 degrees warmer<br />

than mean annual ground temperatures at a<br />

similar depth <strong>on</strong> the ROW, several metres from<br />

the trench. This temperature difference<br />

probably largely reflects the more disturbed<br />

terrain c<strong>on</strong>diti<strong>on</strong>s in the vicinity of the<br />

trench as compared to the rest of the ROW.<br />

Depending <strong>on</strong> the site, the trench may be filled<br />

with local or select backfill. Post<br />

c<strong>on</strong>structi<strong>on</strong> changes have resulted in ditchline<br />

depressi<strong>on</strong> al<strong>on</strong>g a third of the pipeline (IPL,<br />

1986). The subsided ditch may be filled with<br />

p<strong>on</strong>ded. or occasi<strong>on</strong>ally flowing, water (Wishart<br />

and Fooks, 1986). Backfilling of 80 km of<br />

trench, with subsidence >20 cm. occurred<br />

during winter remedial work in 1986 and 1987.<br />

GROUND THERMAL REGIME<br />

Winter c<strong>on</strong>structi<strong>on</strong> generally caused a short<br />

term cooling of the ground beneath the ROW.<br />

This effect can be seen in the ground<br />

temperature isotherms c<strong>on</strong>toured at site 84-1<br />

for September 1984 in Figure 4; temperatures<br />

seen at depths below 2 m <strong>on</strong>-ROW are about 1<br />

degree colder than those off-ROW. The cooling<br />

effect can no l<strong>on</strong>ger be seen in c<strong>on</strong>tours for<br />

September 1986 where <strong>on</strong>-BOW tempecatures have<br />

gradually increased by up to 2 degrees and are<br />

now about 1 degree warmer than off-ROW.<br />

- 1.0<br />

-I<br />

;ROUND TEMPERATURES<br />

ITE 8 4 - 1<br />

m 0.02<br />

metres<br />

=D<br />

Ternperature sensor SURVEYED GROUND SURFACE ISOTHERMS ( " 0<br />

@ Pipe -August 1984<br />

-3eptemher 18 1984<br />

E Pipe centretine --September 1986<br />

I<br />

-.-September 25 198E<br />

i --Unsurveyed ground surface<br />

Fig.4 Isothermal Cross-secti<strong>on</strong>s for Site 84-1.<br />

km 0.02, September 1984 and 1986<br />

Table fI also includes the calculated mean<br />

annual off-ROW ground temperatures from the 1 m<br />

sensor during the sec<strong>on</strong>d year<br />

of operati<strong>on</strong>.<br />

The off-ROW temperatures are generally coldet<br />

E<br />

91 9<br />

(<strong>on</strong> average by I degree but by as much as 3<br />

degrees) than the ROW temperatures.<br />

At thermal fences in new clearings, whether<br />

underlain by permafrost or unfrozen terrain,<br />

the ground thermal regime <strong>on</strong> the ROW after the<br />

initial c<strong>on</strong>structi<strong>on</strong> cooling has been gradually<br />

warming. Increases (up to 2.5 degrees but<br />

generally less than 1 degree) in mean annual<br />

ground temperatures have been recorded <strong>on</strong> the<br />

ROW from the first year of operati<strong>on</strong> to the<br />

sec<strong>on</strong>d. Ground temperatures at depths below<br />

1 m have generally not reached equilibrium with<br />

present near surface c<strong>on</strong>diti<strong>on</strong>s.<br />

The ground thermal resp<strong>on</strong>se in ice-rich terrain<br />

and thick ice-rich peat covered sites has been<br />

slow due to latent heat effects: mean annual<br />

ground temperatures (ROW, 1 m sensor) have<br />

generally changed by less than 0.5 degree.<br />

Little or no change in permafrost temperatures<br />

at depth below 2 m has been observed at these<br />

sites (e.g.lZB, 5A. 5B and 6). Increases in<br />

active layer thickness have been observed; for<br />

example, from 1.5 m <strong>on</strong>-ROW at<br />

85-12B. Visual observati<strong>on</strong>s indicated that the<br />

surface organic soils at 85-12B had underg<strong>on</strong>e<br />

c<strong>on</strong>siderable scraping and blading during<br />

c<strong>on</strong>structi<strong>on</strong> and subsequent remedial activities.<br />

Warm thin (1-2 m) permafrost at two southern<br />

fences (85-10Band85-11),both underlain by<br />

eoile with low ice c<strong>on</strong>tents, has disappeared<br />

within 2 years of ROW clearance. The thermal<br />

regime of two thick permafrost fences in the<br />

north. 84-ZA and ZC, both underlain by coarse<br />

grained till and located in a previous cutline,<br />

has been fairly stable since observati<strong>on</strong>s<br />

began, with active layers ranging from 2 to<br />

6 m. The deeper active layer is observed <strong>on</strong><br />

the ROW of the west facing slope at fence 2C.<br />

Active layers <strong>on</strong> the ROW at the end of the 1986<br />

thaw seas<strong>on</strong> at newly cleared sites with thick<br />

organic soils (greater than<br />

2 m) varied from<br />

C0.5 to 2 m, and elsewhere from C0.5 to<br />

2.5 m. Active layers off-ROW at the end of the<br />

1986 thaw seas<strong>on</strong> were generally (1 m. Active<br />

layers <strong>on</strong>-ROW have increased (by up to 1 m)<br />

since observati<strong>on</strong>s began; off-ROW active layers<br />

by comparis<strong>on</strong> have generally stayed the same<br />

over this period. The active layer6 quoted<br />

here are defined by the maximum depth of<br />

penetrati<strong>on</strong> of the O°C isotherm, a6 measured by<br />

the ground temperature cables (may involve<br />

interpolati<strong>on</strong> between the 50 or LOO cm sensor<br />

spacing and takes any surface settlement into<br />

account). The actual thickness of unfrozen<br />

material may be greater particularly at sites<br />

with Eine-grained soil, due to the freezing<br />

point depres6i<strong>on</strong>.<br />

One thermal m<strong>on</strong>itoring fence (84-ZB, km 19.3)<br />

is located <strong>on</strong> an east-facing slope insulated<br />

with a 1 m cover of wood chips. Data from<br />

IPt's instrumented wood chip slopes are also<br />

stored <strong>on</strong> the government data file, but remain<br />

proprietary until Jan. 1990 at IPL's request.<br />

During the first summer thaw period following<br />

c<strong>on</strong>structi<strong>on</strong>, the wood Chip6 at 84-ZB underwent<br />

a self-heating cycle, with temperatures of up<br />

to 159C Pecorded at a depth of 0.5 m in the<br />

chips. This heat generati<strong>on</strong>, due to microbial<br />

decompositi<strong>on</strong>, has been noted in all wood chip

~ ~ ~ .~<br />

layers during the first summet after placement<br />

(McRoberts et dl.. 1986). This initial selfheating<br />

at 84-2B coupled with a winter<br />

insulating effect (note in Figure 5, which<br />

compares the ground temperature envelope from<br />

the uninsulated off-ROW with the envelope from<br />

the wood chip covered ROW, the absence of<br />

winter cooling beneath .the chips), has resulted<br />

in an increase in mean annual ground<br />

temperature beneath the chips. Current wood<br />

chip/ground surface interface temperatures at<br />

84-28 are near 0°C. Ground temperatures<br />

beneath the wood chips are not in thermal<br />

equilibrium with this interface temperature and<br />

are gradually increasing. Mean annual ground<br />

temperatures at a depth of 1 m below the chips<br />

have increased from -1.5 to -0.5OC during the<br />

observati<strong>on</strong> period. Mean annual 1 m off-ROW<br />

ground temperatures <strong>on</strong> this slope by comparis<strong>on</strong><br />

are -2.5OC.<br />

TEMPERATURE (OC 1<br />

-6 -4 2 0 2<br />

<strong>on</strong><br />

ROW<br />

the 20 surveyed fences. A few sites, notably<br />

km 0.02 and 79.2, where the originally hummocky<br />

terrain was leveled <strong>on</strong> the ROW and much of the<br />

surface organic layer removed across the BOW<br />

during c<strong>on</strong>structi<strong>on</strong>. have again developed a<br />

noticeable hummocky relief (over 50 cm). A<br />

c<strong>on</strong>tour map of settlement at km 0.02, site<br />

84-1. is shown in Fiaure 6 .<br />

. ..<br />

SURFACE ELEVATION CHANGE<br />

LEGEND<br />

Pipe thermistor<br />

Geophysical<br />

access hale<br />

0 Thermistor cab11<br />

Installati<strong>on</strong><br />

I Pipe centreline<br />

y Dlrectl<strong>on</strong> of flou<br />

LEGENO<br />

Woodchips<br />

SITE 84-28<br />

GROUND TEMPERATURE ENVELOPES<br />

MARCH 1985 - MARCH 1986<br />

e Clw,silty<br />

Shale<br />

Fig.5 Ground Temperature Envelopes Beneath<br />

Wood Chips and Off-ROW at 84-2B. km 19.3.<br />

TKAW SETTi.EMENT<br />

Surface settlements recorded by the elevati<strong>on</strong><br />

surveys at the thermal fences represent minimum<br />

settlements <strong>on</strong> the ROW, since in all cases the<br />

baseline survey was taken following the first<br />

thaw seas<strong>on</strong> after ROW tree clearance. The<br />

range of settlement observed at each site is<br />

given in Table 11.<br />

In the trench vicinity (2 m <strong>on</strong> either side of<br />

the pipe), the maximum recorded Settlement<br />

during the limited observati<strong>on</strong> period ranged<br />

from 60 to greater than 100 cm in 9 of 20<br />

surveyed fences. Some of this change is likely<br />

a result of settlement of the trench backfill<br />

which was placed as a frozen and uncompacted<br />

berm over the pipe during the winter. Remedial<br />

backfill has since been placed in the trench at<br />

two fences (85-8C and 85-11) and between fences<br />

85- 10A and 10B.<br />

Ma x imum recorded settlement <strong>on</strong> the ROW outside<br />

the trench area ranged from 50 to 80 crn at 6 of<br />

920<br />

Site 841 - Norman Wells<br />

June 20 1984 - September 17 1986<br />

0-4 7<br />

metres<br />

~<br />

Fig.6 Site 84-1. km 0.02: C<strong>on</strong>toured Surface<br />

Settlement from June 1984 to September 1986.<br />

Only surface settlements are recorded by the<br />

PTRM program: m<strong>on</strong>itoring of pipe movements is<br />

not included. During the establishment of<br />

IPL's georechnical m<strong>on</strong>itoring program 7 sites<br />

were initially selected for thaw settlement<br />

m<strong>on</strong>itoring (IPL, 1984). These locati<strong>on</strong>s<br />

represent worst case situati<strong>on</strong>s where thaw<br />

settlement beneath the pipe, over a short<br />

distance. greater than tho design differential<br />

thaw settlement (established as up to 0.8 m in<br />

mineral soils and up to 1.0 m in thick organics<br />

(Nix<strong>on</strong> and Pick, 1986)) was possible. IPL's<br />

visual m<strong>on</strong>itoring program, an integral part of<br />

their geotechnical m<strong>on</strong>itoring, had identified<br />

an additi<strong>on</strong>al 18 locati<strong>on</strong>s for detailed thaw<br />

settlement investigati<strong>on</strong> by the end of 1986<br />

(IPL, 1986). These areas encompass three<br />

thermal fences (84-1, 85-7B and 85-12B) where<br />

surface settlements of over 60 cm have been<br />

recorded in the trench area and of over 50 cm<br />

elsewhere <strong>on</strong> the ROW. Additi<strong>on</strong>al ground<br />

temperature instrumentati<strong>on</strong> has been installed<br />

by the PTRM program at 5 of these locati<strong>on</strong>s.<br />

CONCLUSIONS<br />

The general results summarized below are based<br />

<strong>on</strong> observati<strong>on</strong>s gathered at the instrumented<br />

thernlal fences following two years of pipeline<br />

operati<strong>on</strong>. The PTBM is proposed to c<strong>on</strong>tinue<br />

for 5-10 years or until c<strong>on</strong>diti<strong>on</strong>s stabilize.<br />

The "ambient" pipeline operates with mean<br />

annual pipe temperatures generally above 0-C<br />

within both predominantly frozen terrain and<br />

unfrozen terrain. Mean pipe temperatures

du ring the sec<strong>on</strong>d year of operati<strong>on</strong> ranged f r om<br />

0 to -+5OC. The mean annual pipe temperatures<br />

are generally warmer (<strong>on</strong> average by 1.5 degree)<br />

than mean annual ground temperature6 <strong>on</strong> the ROW<br />

outside the trench area at a similar depth.<br />

Mean annual ground temperatures <strong>on</strong>-ROW, at a<br />

depth of 1 m several metres from the trench,<br />

ranged from -2 to +4OC during the sec<strong>on</strong>d year<br />

of pipeline operati<strong>on</strong>. Mean annual 1 m ground<br />

temperarures off-ROW during this period ranged<br />

from -3 to +3OC. The mean off-ROW ground<br />

temperatures are generally colder than <strong>on</strong>-ROW,<br />

by 1 degree <strong>on</strong> average. The ground thermal<br />

regime <strong>on</strong> the ROW is generally not in thermal<br />

equilibrium with present surface c<strong>on</strong>diti<strong>on</strong>s. A<br />

warming trend has been observed at most sites<br />

from the first to the sec<strong>on</strong>d year of<br />

operati<strong>on</strong>. The thermal resp<strong>on</strong>se in ice-rich<br />

terrain is slow due to latent heat effects.<br />

Active layers <strong>on</strong>-ROW, which currently range<br />

from (0.5 m to 2.5 m. have generally<br />

increased (by up to 1 m) during the observati<strong>on</strong><br />

period. Off-BOW active layers, generally less<br />

than 1 m. have changed relatively little.<br />

At the thermal fence located <strong>on</strong> a wood chip<br />

insulated slope the mean annual wood<br />

chip/ground surface interface temperature is<br />

currently -0.2-C. Mean annual ground<br />

temperatures have increased, e.g. from -1.5 to<br />

-0.5OC at 1 m below the interface.<br />

Maximum recorded surface settlement ranged from<br />

60 to over 100 cm in the trench vicinity at 9<br />

of 20 surveyed thermal fences and from 50 to<br />

80 cm <strong>on</strong> the ROW outside the trench area at 6<br />

of 20 surveyed thermal fences.<br />

ACKNOWLEDGMENTS<br />

The efforts of Kaye MacInnes (INAC) in<br />

organizing and coordinating this program<br />

require special menti<strong>on</strong>. Many other<br />

individuals within INAC, EMR and IPL have<br />

provided cooperati<strong>on</strong>, support and assistance:<br />

in particular, A. Judge, J. Pil<strong>on</strong>, V. Allen,<br />

W. Pearce. A. Pick, D. Wishart, J. Smith,<br />

M. Yerichuk, W. Dunlop, F. Adlem, and<br />

B. Gauthier. The PTRM program has been<br />

primarily funded by INAC's Northern Affairs<br />

program. with c<strong>on</strong>tributi<strong>on</strong>s from the Northern<br />

Oil and Gas Acti<strong>on</strong> Program (NOGAP). Additi<strong>on</strong>al<br />

funding and assistance has been provided by<br />

EMR's former Earth Physics Branch, the<br />

Geological Survey of Canada and the Federal<br />

Panel <strong>on</strong> Energy <strong>Research</strong> and Development, IPL<br />

Ltd, and the N.W.T. Regi<strong>on</strong>al Surveyor's Office.<br />

REFERENCES<br />

Burgess. M M (1986)<br />

Norman Wells pipeline m<strong>on</strong>itoring sites ground<br />

temperature data file: 1984-1985. Energy,<br />

Mines and Resources Canada, Earth Physics<br />

Branch Open File 86-6. 21 pp + app.<br />

Burgess, M M (1987)<br />

Norman Wells pipeline m<strong>on</strong>itoring sites ground<br />

temperature data file: 1986. Energy. Mines<br />

and Resources Canada, Geological survey of<br />

Canada, open File 1621, 24 pp + app.<br />

921<br />

Burgess. M M, Pil<strong>on</strong>. J A & MacInnes, K L (1986)<br />

<strong>Permafrost</strong> thermal m<strong>on</strong>itoring program. Norman<br />

Wells to Zama oil pipeline. 1ntl.Soc.Pet.Ind.<br />

Bio., Proc.North.Hydrocarb.Dev.Env.Prob.Solv.<br />

C<strong>on</strong>f.. Sept. 1985, Banff. Canada. 248-257.<br />

Interprovincial Pipe Line (NW) Ltd. (1982).<br />

Reassessment of plans to minimize terrain<br />

damage al<strong>on</strong>g the Interprovincial Pipe Line(NW)<br />

Ltd. oil pipeline from Norman Wells to Zama.<br />

Report to Nat. Energy Board of Canada, 25pp.<br />

Interprovincial Pipe Line (NW) Ltd. (1984).<br />

Post c<strong>on</strong>structi<strong>on</strong> m<strong>on</strong>itoring programs for the<br />

Norman Wells to Zama pipeline. Report to the<br />

Nati<strong>on</strong>al Energy Board of Canada, 29pp + app.<br />

Interprovincial Pipe Line (NW) Ltd. (1986).<br />

Norman Wells Pipeline project. 1986 report<br />

<strong>on</strong> m<strong>on</strong>itoring of c<strong>on</strong>structi<strong>on</strong> and operati<strong>on</strong>.<br />

Report to Nat. Energy Board of Canada, 107pp.<br />

Kay. A E, Allis<strong>on</strong>, A M, Botha, W 3 6 Scott, W J<br />

(1983).<br />

c<strong>on</strong>tinuous geophysical investigati<strong>on</strong> for<br />

mapping permafrost distributi<strong>on</strong>, Mackenzie<br />

Valley, N.W.T.. Canada. Proc.4th Intl.<br />

Perm.c<strong>on</strong>f., Fairbanks, Alaska, July 1983,<br />

578-583.<br />

MacInnes, K. Burgess, M, Harry, D, Baker, H.<br />

Tarnocai. C. Pil<strong>on</strong>. J b Judge. A (in prep).<br />

Norman Wells to Zama Pipeline <strong>Permafrost</strong><br />

and Terrain M<strong>on</strong>itoring Program: Progress<br />

Report 1983-1986.<br />

McRoberta, E C, Nix<strong>on</strong>, J F, Hanna, A J & Pick.<br />

A R (1985).<br />

Geothermal c<strong>on</strong>siderati<strong>on</strong>s for wood chips used<br />

as permafrost slope insulati<strong>on</strong>. Proc.Int1.<br />

Symp.Gr.Freez.. Japan, Aug. 1985, Vol.1,<br />

305-312.<br />

McRoberts, E C, Hanna, A J and Smith. J (1986).<br />

M<strong>on</strong>itoring of thawing permafrost slopes:<br />

Interprovincial Pipe Line. Nat. Res. COunC.<br />

Canada, Proc. Workshops.<strong>on</strong> Subsea.Perm. and<br />

Pipelines in Perm., Nov. 1985, Tech. Memo 139,<br />

133-151.<br />

Nati<strong>on</strong>al Energy Board Canada (1981).<br />

Reas<strong>on</strong>s for decisi<strong>on</strong> in the matter of an<br />

applicati<strong>on</strong> under the Nati<strong>on</strong>al Energy Board<br />

Act of Interprovincial Pipe Line (NW) Ltd.,<br />

Supply and Services Canada Cat. No. NE<br />

22-1/1981-1E, 173pp t app.<br />

Nix<strong>on</strong>, J F & Pick. A R (1986).<br />

Design of Norman Wells pipeline for frost<br />

heave and thaw settlement. Nat.Res.Counc.Can.<br />

P~oc.Workshops Subsea Perm.&Pipelines in Perm.<br />

NOV. 1985, Tech.Memo. No. 139, 67-85.<br />

Nix<strong>on</strong>, J F, Stuchly, J & Pick, A R (1984).<br />

Design of Norman Wells pipeline for frost<br />

heave and thaw settlement. Am.Soc.Mech.Eng.,<br />

Proc.3rd Intl.Offshore Mech. and Arctic Eng.<br />

Symp., New Orleans, La., Feb. 12-16, 1984.<br />

Pick, A B (1986).<br />

Norman Wells pipeline project. Nat. Res.<br />

Count. Canada, PIOC. Workshops <strong>on</strong> subsea<br />

permafrost and pipelines in permafrost, Nov.<br />

1985, Tech. Memo. No. 139, 61-66.<br />

Pil<strong>on</strong>. J A, Burgess. M M, Judge. A S, Allen, V<br />

S, MacInnes. K L. Harry, D G, Tarnocai. C and<br />

Baker. H (in prep).<br />

Norman Wells to Zama pipeline permafrost and<br />

terrain research and m<strong>on</strong>itoring program: site<br />

establishment report.<br />

Wishart, D M & Fooks, c E (1986).<br />

Norman Wells pipeline project right-of-way<br />

drainage c<strong>on</strong>trol - problem6 and soluti<strong>on</strong>s.<br />

1ntl.Soc.Pet.Ind.Bio.. Proc.North.Hydrocarb.<br />

Dev.Env.Problem Solv.C<strong>on</strong>f., Banff. Canada,<br />

Sept. 1985, 209-218.

CONTRIBUTION TO THE STUDY OF THE ACTIVE LAYER IN THE AREA<br />

AROUND CENTRUM LAKE, NORTH EAST GREENLAND<br />

M. Chir<strong>on</strong> and J.4 Loubiere<br />

Dipartement de CQdynamique des milieux c<strong>on</strong>tinentaux Universitb Pierre et Marie Curie, Paris, France<br />

SYNOPSIS The objective of an expediti<strong>on</strong> to northeastern Greenland was to c<strong>on</strong>duct a<br />

preliminary study of <strong>on</strong>e of the northernmost karsts In the world. It is located in Komprins<br />

Chrlstian Land. We thought It would be interesting to observe the importance of the active layer<br />

(mollisol) at the end of the m<strong>on</strong>th of July 1983, <strong>on</strong> a terrace <strong>on</strong> the west bank of Lake Centrum.<br />

INTRODUCTION<br />

In the summer, at a latitude of EO' north,<br />

there is sunlight allthe time and the<br />

temperatures are above zero. We noted that<br />

between July 10th and August 6th 1983 there<br />

was a mlnimum of +lo and a maximum of +14".<br />

There was virtually no rainfall. However the<br />

regi<strong>on</strong> was swept by extremely high winds. The<br />

ground has thawed about several dozen<br />

centimeters and this thickness represents the<br />

active layer which is a good climatic<br />

indicater of the extreme envir<strong>on</strong>ment. To the<br />

best of our knowledge, the <strong>on</strong>ly (and very<br />

interesting) measurements performed in the<br />

area are those c<strong>on</strong>ducted by W. Davies during<br />

his voyage of June 1960.<br />

Our c<strong>on</strong>tributi<strong>on</strong>, comprising several<br />

additl<strong>on</strong>al measurements, wlll trace 3 secti<strong>on</strong>s<br />

which cut through the terraces, the river and<br />

the lake.<br />

LOCATION<br />

Our soundings were performed <strong>on</strong>. a large<br />

ice-free terrace bordered by two rlvers<br />

(the Saefaxi Elv to the north and the Clear<br />

Water). The source of the two rlvers is<br />

located in the large inlandsls situated some<br />

40 km upstream to the west. They flow lnto<br />

Centrum Lake down further. The soil, which is<br />

composed of polyg<strong>on</strong>s of tundra 2 to 15 meters<br />

in dlameter, c<strong>on</strong>slsts of about 80% of sand of<br />

fluviatile and aeolian origln, while the<br />

remaining 20% c<strong>on</strong>slsts of flne gravel. ThLs<br />

surface is situated at an alt.itude of between<br />

0 and 6 meters above sea level. Hekla Fjord<br />

is about 60 km avay.<br />

METHODOLOGY<br />

Two types of soundings were performed :<br />

firstly al<strong>on</strong>g an axis A, located entirely <strong>on</strong><br />

the upper t:errace, 1700 m in length, in an<br />

east-west directi<strong>on</strong>; using shovels we dug<br />

four circular holes 60 cm In dlameter, 565 m<br />

from each other.<br />

Sec<strong>on</strong>dly, using a sledge hammer, we drove<br />

a round metal bar 2 cm in diameter, 2 m apart<br />

al<strong>on</strong>g an axis B (74 m in Length) and then<br />

45 m apart al<strong>on</strong>g an axis C 11125 m in length)<br />

until we reached the permafrost.<br />

The first sounding of the cross-secti<strong>on</strong><br />

(B axis) was performed in the emerged bed<br />

(after the summer flood) of the Clear Water<br />

River. The first sounding al<strong>on</strong>g the<br />

l<strong>on</strong>gitudinal secti<strong>on</strong> (C axis) was performed<br />

below the water level of Lake Centrum.<br />

Observati<strong>on</strong>s<br />

On the sandy terrace, 2.5 to 5 m above the<br />

lake, the depth of permafrost was found to<br />

be 76 cm (soundings 1 and 2 <strong>on</strong> A axis) and to<br />

be 83 cm (soundings 3 and 4 <strong>on</strong> A axis) .<br />

Soundings 1 and 2 found that water collected<br />

very rapidly, suggesting a badly drained<br />

mollisol. Soundings 3 and 4 <strong>on</strong>, the other<br />

hand, carried out at a slightly higher<br />

altitude, remained dry.<br />

(i) In the permanent river Bed, the water<br />

had acted as a shield and so the<br />

frozen ground was closer to the<br />

surface (39 to 40 cm). We believe that<br />

the calories supplied by the watex<br />

(temperature 8.2 <strong>on</strong> July 13)<br />

c<strong>on</strong>tributed to the thaw and the<br />

formati<strong>on</strong> of mollisol.<br />

(il)<br />

Below the surface of the lake, the<br />

ground had thawed over 16 cm (sounding<br />

al<strong>on</strong>g C axis). The temperature of the<br />

water therefore seems sufficient to be<br />

able to push back the permafrost at<br />

this level, with the formati<strong>on</strong> of a<br />

submerged mollisol just below the<br />

surface of the river.<br />

(lii) However, the fact that the water is not<br />

very deep in the intermittent branch of<br />

the river means it: does not. c<strong>on</strong>st.itul.c<br />

an insulati<strong>on</strong> layer sufficient t.0<br />

protect the permafrost which is thus<br />

pushed back to 60 cm from the surface<br />

which is <strong>on</strong>ly slightly submerged.<br />

922

The terrace presented an exposed hill slope<br />

to the south (with a slope of 40"). In spite<br />

of this exposure, which would have been<br />

favourable to a pr<strong>on</strong>ounced thaw, we noted that<br />

the mollisol was relatively thin over the<br />

whole of the hill slope. It was <strong>on</strong>ly <strong>on</strong> the<br />

edge of the talus that the mollisol became at<br />

all Significant, growing from 64 to 112 cm,<br />

the largest that we were able to observe in<br />

the regi<strong>on</strong> (see Figure 4. transverse cut,<br />

B axis, sounding 33). This z<strong>on</strong>e has benefitted<br />

from the maximum solar radiati<strong>on</strong> in July.<br />

We know that the albedo, i.e. the capacity<br />

of reflecti<strong>on</strong> with regard to solar radiati<strong>on</strong>,<br />

varies with the nature of the envir<strong>on</strong>ment<br />

affected by it. ,During the summer m<strong>on</strong>ths,<br />

as the thin layer of snow has melted, the<br />

sandy substratum, which is dark brown in<br />

colour, absorbs the heat. This weakness in<br />

the acti<strong>on</strong> of the albedo synergizes with the<br />

exposure and the gradient factors..of the<br />

site.<br />

CONCLUSION<br />

In this brief note, am<strong>on</strong>g the different<br />

factors of the geographic milieu influencing<br />

the freeze-thaw cycle of the soil, arethe part<br />

played by the climate of the locality, the<br />

vegetati<strong>on</strong> and snow coverage, the nature of<br />

the soil and its temporary degree of<br />

humidity with without water being present.<br />

The importance of another factor is c<strong>on</strong>firmed:<br />

the exposure ef the site.<br />

We observed this in July 1983. This liquid<br />

mass delays the warming and the thawing of<br />

the submerged soil. According to Our<br />

observati<strong>on</strong>s, it would seem that the level<br />

of water covering the permanenily or<br />

temporarily submerged mollisol is decisive :<br />

the greater the layer of water, the smaller<br />

the thickness of the mollisol. For this to<br />

be c<strong>on</strong>firmed, additi<strong>on</strong>al measurements would<br />

have to be made in both summer and winter<br />

at different depths in Lake Centrum. Even<br />

though quaternary c<strong>on</strong>tinental carb<strong>on</strong>ate<br />

formati<strong>on</strong>s of north Greenland are better<br />

understood ( Adolphe, Loubihre 1986), no study<br />

has been yet carried out to our knowledge <strong>on</strong><br />

the lake sedimentati<strong>on</strong> in this regi<strong>on</strong>.<br />

f<br />

REFERENCES<br />

Adolphe, J-P, Loubihre, J-F (1987). Etude<br />

preliminaire sur les calcins du Nord Est<br />

Groenland. Symp<strong>on</strong>ium Caen Aout Bb. Pecsi M.,Prench<br />

H.M (Eds): Loess and Periglacial phenomena,<br />

Akademia-Kiaddo, Wldapest 1887<br />

Davies, E.W. (1964). Surface Features of<br />

<strong>Permafrost</strong> in arid areas. US Geological<br />

Survey, Washingt<strong>on</strong> D.C. USA.<br />

Davies, E.W. (1972). Landscape of Northern<br />

Greenland. Special Report 164. Cold regl<strong>on</strong>s<br />

research and engineering laboratory,<br />

Hanover, New Hampshire, USA.<br />

Geographical situati<strong>on</strong><br />

FAROYELL<br />

923

I<br />

N<br />

-<br />

1 km<br />

i I<br />

i<br />

,Gloom<br />

L<br />

Fig. 3<br />

Schematic showing the locati<strong>on</strong> of the soundings g2, E,,<br />

72 and 73 parallel to the Clear Water river and<br />

perpendicular to the C axis. The soundings 73 and g2<br />

were performed below the 18 cm of water of the river.<br />

.+<br />

'Clear dater River<br />

I<br />

Fig. 2<br />

Locati<strong>on</strong> of the soundings<br />

nord<br />

NORTn<br />

aa 34<br />

1<br />

*I<br />

1 1<br />

sud<br />

SOUTH<br />

t<br />

1<br />

4<br />

4<br />

-" 54 bI<br />

-"<br />

Fig. 4<br />

Cross-secti<strong>on</strong> of the edge of the river of the first terrace showing the<br />

thickness of the rnollisol<br />

924

83<br />

TABLE I<br />

N" of soundings Depth of istance between<br />

water, in he surface and Observati<strong>on</strong>s<br />

cm ithe permafrost,<br />

I in cm<br />

1 76<br />

no water<br />

2 I 16<br />

3 surf ace ~<br />

4<br />

I<br />

<strong>on</strong> the 1 and 2<br />

I<br />

I<br />

83<br />

After 3 to 4 minutes<br />

2 to 3 cm of water collected<br />

in the bottom of soundings<br />

Soundings remained dry<br />

TABLE I1<br />

1" of soundings<br />

Depth of<br />

water, in<br />

cm<br />

istance between<br />

he surface and<br />

he permafrost,<br />

in cm<br />

Observati<strong>on</strong>s<br />

1<br />

2<br />

3<br />

4<br />

5<br />

6<br />

7<br />

8<br />

9<br />

10<br />

11<br />

12<br />

13<br />

14<br />

15<br />

16<br />

17<br />

18<br />

19<br />

20<br />

21<br />

22<br />

23<br />

24<br />

25<br />

26<br />

21<br />

28<br />

29<br />

30<br />

31<br />

32<br />

33<br />

34<br />

35<br />

36<br />

37<br />

38<br />

30<br />

32<br />

"<br />

39<br />

30<br />

54<br />

68<br />

72<br />

70<br />

70<br />

71<br />

69<br />

69<br />

74<br />

72<br />

74<br />

73<br />

73<br />

74<br />

75<br />

76<br />

73<br />

70<br />

73<br />

72<br />

72<br />

69<br />

69<br />

68<br />

67<br />

71<br />

76<br />

60<br />

60<br />

64<br />

112<br />

97<br />

89<br />

88<br />

84<br />

83<br />

The 2 soundings were performed<br />

below the waters in the bed of<br />

the Clear Water river.<br />

Sounding performed in an<br />

intermittent branch of the<br />

Clear Water river (see<br />

schematic 1)<br />

The B axis, oriented south-north, was 74 m in length. The 38 soundings were 2 m from each other<br />

(see locati<strong>on</strong> map).<br />

925

N" of soundings<br />

Depth o f<br />

b-ater, ~n<br />

crn<br />

Distance between<br />

the surface and<br />

the permafrost,<br />

In cm<br />

t<br />

Observati<strong>on</strong>s<br />

1<br />

1<br />

2<br />

3<br />

4<br />

5<br />

6<br />

71<br />

'2<br />

73<br />

81<br />

82<br />

91<br />

92<br />

10<br />

11<br />

12<br />

13<br />

14<br />

15<br />

16<br />

17<br />

18<br />

19<br />

20<br />

21<br />

22<br />

23<br />

24<br />

25<br />

30<br />

18<br />

0<br />

18<br />

46<br />

68<br />

65<br />

70<br />

68<br />

66<br />

76<br />

63<br />

55<br />

71<br />

76<br />

63 1<br />

j<br />

The first sounding was<br />

performed below the<br />

waters of Lake Centrum<br />

Soundings tangential to t-he<br />

Clear Water river (see<br />

schematic 1)<br />

57<br />

62<br />

64<br />

68<br />

1<br />

64<br />

68<br />

1<br />

68<br />

61<br />

69<br />

69<br />

68<br />

70<br />

69<br />

Sounding performed in an<br />

73<br />

intermittent branch of<br />

65<br />

the Clear Water river.<br />

70<br />

76<br />

1<br />

The C axis, oriented east-north-east / west-south-west, was 1125 rn<br />

25 soundings were 45 rn from each other (see locati<strong>on</strong> map).<br />

in length. The<br />

926

SEASONAL VARIATIONS IN RESISTIVITY AND TEMPERATURE<br />

IN DISCONTINUOUS PERMAFROST<br />

A. Delaney, P.Sellmann and S. Arc<strong>on</strong>e<br />

U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering Laboratory, Hanover, N.H. 03755-1290 USA<br />

SYNOPSIS Electrical resistivity and temperature were measured in two 12.2-m-deep<br />

boreholes in interior Alaska in perennially frozen ice-rich silt and in coarse-grained alluvium.<br />

Seas<strong>on</strong>al temperature and resistivity changes were most noticeable in the upper 6 m at both<br />

sites, with resistivity varying more than several thousand ohm-m during the year. Resistivity<br />

profiles were compared with lithology, temperature and moisture c<strong>on</strong>tent. At the alluvium site<br />

resistivity and grain size str<strong>on</strong>gly correlated. Values ranging over 10.000 ohm-m occurred with<br />

coarse-grained material and values an order of magnitude lower occurred in the fine-grained<br />

material secti<strong>on</strong>. At the ice-rich silt site, resistivity values were generally lower, but in<br />

agreement with values for the fine-grained part of the alluvial secti<strong>on</strong>. Lithologic variati<strong>on</strong>s<br />

in the disc<strong>on</strong>tinuous permafrost 20ne can be as important as the high permafrost temperatures and<br />

corresp<strong>on</strong>dingly large unfrozen water c<strong>on</strong>tents in accounting for significant seas<strong>on</strong>al resistivity<br />

changes in fine-grained sediment.<br />

INTRODUCTION<br />

The electrical resistivity of perennially<br />

frozen materials can be a direct indicati<strong>on</strong> of<br />

material type, permeability, volumetric water<br />

or ice c<strong>on</strong>tent and temperature. Resistivity<br />

is usually interpreted from meaaurements of<br />

apparent resistivity using multi-electrode<br />

galvanic arrsp (Wenner, 1915)~ low frequency<br />

magnrtotelluric, wavetilt or surface impedance<br />

plans wave method$ (ems., Hoekstra et al.,<br />

1974; Are<strong>on</strong>e et al., 1978, 1979; Koziar and<br />

Strangway, 1978) pr by magnetic inducti<strong>on</strong> and<br />

induced polarizati<strong>on</strong> techniques (e.g. Sinha,<br />

1976; Hoekatra, 1978). The transient electromagnetic<br />

technique has proven useful for studies<br />

of thick permafrost (Ehrenbard et al.,<br />

1983). It was our intenti<strong>on</strong> to observe directly<br />

sessi<strong>on</strong>al variati<strong>on</strong>s in ground resistivity<br />

using a permanent vertical electrode array and<br />

to compare the results with temperature and<br />

material characteriatics.<br />

Vertiaal. arrays were installed at sites,o€<br />

previous geophysical investigati<strong>on</strong>s (e.g.,<br />

Arc<strong>on</strong>e et al., 1978: Arc<strong>on</strong>e and Delaney,<br />

1985). In early April 1985, strings of electrodes,<br />

11.2 m l<strong>on</strong>g, were placed in boreholes<br />

in gravelly alluvium and in Fairbanks silt<br />

where soil type and ice c<strong>on</strong>tent had been<br />

logged. The electrodes were at 30 cm intervals,<br />

which allowed vertical profiling at<br />

various electrode separati<strong>on</strong>s. The temperature<br />

holes were within 3 m of the resistivity<br />

holes and data were recorded throughout the<br />

year.<br />

RESISTIVITY OF EARTH MATERIALS<br />

The resistivity of most earth materials usual- from<br />

ly falls between 10 and 10,000 ohm-m. The<br />

927<br />

factors that most influence the resistivity of<br />

unfrozen earth materials c<strong>on</strong>taining n<strong>on</strong>c<strong>on</strong>ductive<br />

(i.e., n<strong>on</strong>metallic) minerals are free<br />

water c<strong>on</strong>tent, i<strong>on</strong>ic c<strong>on</strong>centrati<strong>on</strong>, pemeability,<br />

porosity and grain size. C<strong>on</strong>ducti<strong>on</strong> is<br />

mainly electrolytic al<strong>on</strong>g c<strong>on</strong>tinuous films of<br />

water adsorbed <strong>on</strong> grain boundaries, and<br />

through water in pore spaces (Parkhomenkho,<br />

1967). C<strong>on</strong>ductivity (the inverse of resistivity)<br />

is proporti<strong>on</strong>al to the i<strong>on</strong>ic c<strong>on</strong>centrati<strong>on</strong><br />

of the water and the i<strong>on</strong>ic mobility,<br />

i.e., the c<strong>on</strong>centrati<strong>on</strong> and quality of c<strong>on</strong>ducting<br />

paths, determined by material textural<br />

properties. As temperature drops below<br />

O'C, the resistivity increases as the amount<br />

of unfrozen water decreases. This unfrozen<br />

water exists in an adsorbed state <strong>on</strong> the grain<br />

surfaces and in a saline c<strong>on</strong>diti<strong>on</strong> in the pore<br />

spaces (hndersen et al., 1973). C<strong>on</strong>sequently,<br />

the amount of fine-grained material in a secti<strong>on</strong><br />

and the temperature will str<strong>on</strong>gly c<strong>on</strong>trol<br />

the unfrozen water c<strong>on</strong>tent. Resistivities<br />

greater than 10' ohm-m have been encountered<br />

when the ground ice c<strong>on</strong>tent is far in excess<br />

of saturati<strong>on</strong> (Hoekstra et al., 1974).<br />

METHODS AND MEASUREMENT TECHNIQUES<br />

Rssistivitv<br />

Weawrements of apparent resistivity were made<br />

in vertical boreholes using the Wenner c<strong>on</strong>figurati<strong>on</strong>.<br />

A Wenner array c<strong>on</strong>sists of four<br />

colinear, equispaced electrodes. A current I<br />

is delivered and received between the outer<br />

electrodes, and the resulting potential difference<br />

V is measured between the inner electrodes.<br />

For this array <strong>on</strong> the ground surface<br />

an apparent ground resistivity pa is computed

where g is the inter-electrode separati<strong>on</strong>. If<br />

the array is within the ground (Fig. 1)<br />

Pa = 4WBI<br />

Y<br />

*<br />

This separati<strong>on</strong> is varied to sound into the<br />

earth, or held c<strong>on</strong>stant to profile. If the<br />

ground is homogeneous, pa is the actual ground<br />

The transmitter used was a Huntec LOW E"3,<br />

which has a selectable output impedance to<br />

match electrode resistance as variati<strong>on</strong>s in<br />

ground c<strong>on</strong>diti<strong>on</strong>s occur throughout the year.<br />

Maximum output current was selected (generally<br />

0.2 to 1.5 A) and recorded for each data stati<strong>on</strong>.<br />

Potential was measured with Dc a diqital<br />

voltmeter (Fluke 8600A). Potentials were<br />

recorded for both cycles of the transmitter<br />

output and, during the off-cycle, to check for<br />

spurious self-potential readings that may<br />

indicate high c<strong>on</strong>tact resistance. The average<br />

voltage level was used to compute pa for each<br />

stati<strong>on</strong>. ,<br />

tt"<br />

H<br />

1<br />

Apparent<br />

Resistivity * 47r of<br />

Fig. 1 A schematic drawing of the buried<br />

Wenner array.<br />

The electrodes were placed at 30-cm intervals<br />

from the ground surface to depth a of 12.2 m<br />

and c<strong>on</strong>nected to a juncti<strong>on</strong> black at the<br />

ground surface. Each electrode was made up<br />

from several strands of tinned copper wire<br />

wrapped around the cable bundle. The cable<br />

bundles were armored with spiral wrap polyethylene<br />

to prevent damage both during instal-<br />

-<br />

lati<strong>on</strong> and from frost acti<strong>on</strong> in the active<br />

layer. This bundle was then taped to the outside<br />

of a 3.8-cm-diameter (1-1/2-in.) ABS pipe<br />

for inserti<strong>on</strong> into the drilled holes. This<br />

assured a straight cable array and accurate<br />

podti<strong>on</strong>ing of the electrodes.<br />

vertical temperature profiles were recorded<br />

coincidentally with the resistivity measurements<br />

in a 3.8-m-diameter cased hole filled<br />

with ethylene glycol. A thermistor calibrated<br />

resistivity p. Complicated integral formulati<strong>on</strong>s<br />

are required to relate layer parameters<br />

to pa in the usual case of a horiz<strong>on</strong>tally<br />

layered earthl and interactive computer programs<br />

now facilitate intarpretati<strong>on</strong> of ,soundings<br />

made from the surface. Procedures are<br />

to O.0loC was attached to 15.2-m a cable and<br />

not available to interpret data for subsurface<br />

resistance was recorded with a Fluke 8600A<br />

arrays. close a separati<strong>on</strong>s were used to give<br />

digital multimeter as the thermistor was<br />

readings indicative of the immediate surroundlowered<br />

down the glycol filled hole. Readings<br />

ings: the radius of the z<strong>on</strong>e of influence of a<br />

were made when the ohm-meter indicated thermal<br />

particular separati<strong>on</strong> is generally asmmed to equilibrium at stati<strong>on</strong>s every 30 cm for the<br />

be about.0.7 g. However, high-resistivity<br />

top 5 m and at 1.5-m increments below that<br />

materials may force the current close to the<br />

level.<br />

borehole and reduce the depth of investigati<strong>on</strong><br />

(Labo, 1987).<br />

SITES<br />

The study sites c<strong>on</strong>tained soils comm<strong>on</strong> in- to<br />

terior Alaska <strong>on</strong> much of the Yuk<strong>on</strong>-Tanana<br />

uplands and <strong>on</strong> the broad Tanana floodplain.<br />

The silt site is at the USACRREL field stati<strong>on</strong><br />

located off Farmers Loop Road near Fairbanks.<br />

It is an area of undisturbed permafrost with a<br />

natural black spruce forest and an organic<br />

ground cover. The active layer thickness is<br />

usually less than 1.0 m. The soil is retransported<br />

Fairbanks silt and is frozen deeper<br />

than 33 m (Pbwe', 1958). Holes for casing installati<strong>on</strong><br />

at the silt site were rotary<br />

drilled using compressed air for circulati<strong>on</strong>.<br />

Grab samples were obtained during drilling and<br />

the casing was backfilled with silt a slurry.<br />

Gravimetric water c<strong>on</strong>tent was measured and<br />

c<strong>on</strong>verted to volumetric ice c<strong>on</strong>tent using the<br />

calibrati<strong>on</strong> discussed by Arc<strong>on</strong>e and Delaney<br />

(this volume)<br />

.<br />

The alluvium site is located near the Chena<br />

River <strong>on</strong> Ft. Wainwright in an area mapped ,as<br />

flood plain sand and gravel (~ewc', 1958). The<br />

annual active layer thickness is usually about<br />

1.5 m and the soils are c<strong>on</strong>tinuously frozen to<br />

at least 12.2 m. The 20.3-m-diameter holes<br />

for casing installatiorl were,augered to 12.2<br />

m.<br />

RESULTS<br />

Eighteen resistivity and temperature profiles<br />

were recorded betwean July 1985 and September<br />

1986 at both the Ft. Wainwright and Farmers<br />

Loop sites. Apparent resistivity was recorded<br />

at 38 vertical locati<strong>on</strong>s <strong>on</strong> each recording<br />

sessi<strong>on</strong>. Apparent resistivity results are €or<br />

an 1 separati<strong>on</strong> of 30 cm, and we assume that<br />

928

E<br />

v<br />

f<br />

CL<br />

W<br />

0<br />

a. Temperature. b. Apparent resistivity.<br />

Fig. 2 Temperature and apparent resistivity c<strong>on</strong>tours as a functi<strong>on</strong> of depth for the alluvium site '<br />

recorded between July 1985 and September 1986.<br />

Average Ground Temperature @)<br />

Average Apparent Resistivity<br />

Measured Gravimetric<br />

Water C<strong>on</strong>tent (X)<br />

41<br />

10..<br />

41<br />

*12-<br />

Fig. 3 The average apparent resistivity compared with the average<br />

ground temperature and gravimetric Soil moisture c<strong>on</strong>tent as a functi<strong>on</strong> of<br />

depth at the alluvium site. ,<br />

material within a radius of 20 cm primarily<br />

rIot return to the 1985 summer values. This<br />

influences the resistivity data.<br />

z<strong>on</strong>e of lower resistivity<br />

shown by the<br />

1000-ohm-rp closed c<strong>on</strong>tour <strong>on</strong> Figure 2b. This<br />

Flluvium Site<br />

may seem unusual in view of the lobe of low<br />

temperatures seen at this positi<strong>on</strong> in Figure<br />

C<strong>on</strong>toured temperature data are shown in Figure Za; however, what is actually unusual are the<br />

2a. The zero degree c<strong>on</strong>tour defines the limit high values seen beneath July-October at 3-6 m<br />

of seas<strong>on</strong>al thaw, which reaches 1.5 m by mid- depth. This z<strong>on</strong>e is associated with the silt<br />

September. The average temperature at 12.2 m secti<strong>on</strong> shown in Figure 3, and at this time no<br />

is -0.36T. All of the temperatures are very logical explanati<strong>on</strong> has been developed to<br />

c<strong>on</strong>sistent at depth. The pa values for the<br />

clarify this unusual pattern.<br />

alluvial site are shown c<strong>on</strong>toured in Figure<br />

2b. Apparent resistivity is generally high<br />

Figure 3 compares the computed average apparthroughout<br />

the year, with most values between ent resistivity (5,) from all recorded<br />

8,000-15,000 ohm-m at depths greater than 3 m. measurements with gravimetric water c<strong>on</strong>tent,<br />

The widest range (92-25,000 ohm-m) occurs .in with the lithology of samples from a hole<br />

the active layer, which experiences thi most drilled near the resistivity string and with<br />

variati<strong>on</strong> in moisture c<strong>on</strong>tent and ground tem- average ground temperature. The subfreezing<br />

perature. Values of 3,000-10,000 ohm-m re-<br />

temperatures imply that nearly all the water<br />

corded at 2-5 m depth in early December de-<br />

was frozen except in the silt secti<strong>on</strong>s where<br />

creased to 700 ohm-m by late February, but did the fine-grained nature of the soil pro- can<br />

929

0<br />

c<br />

-<br />

E<br />

E4<br />

Q<br />

0<br />

-060 .PO0 -020 -010 .OlO -010 .a70 -010 -010 -0 10<br />

Fig. 4<br />

a. 1947-48.<br />

Temperature c<strong>on</strong>tours as<br />

b. 1985-86.<br />

functi<strong>on</strong> of depth for the silt site.<br />

vide a network of unfrozen water near the<br />

grain surfaces. The low Fa values at the sur-<br />

face are ascribable to the higher temperatures<br />

experienced during the summer to and the<br />

c<strong>on</strong>ductive active layer. The increase of pa<br />

at the base of the active layer reflects the<br />

sharp decrease in average temperature and<br />

decrease in silt c<strong>on</strong>tent. The sharp decrease<br />

below 3 m corresp<strong>on</strong>ds to the change in lithology<br />

back to silt. Below 4 m pa gradually increases<br />

as the silt c<strong>on</strong>tent progressively<br />

decreased with depth to less than 20% by<br />

weight of mineral c<strong>on</strong>tent at 12 m depth.<br />

Arc<strong>on</strong>e and Delaney (in press) have<br />

shown organic c<strong>on</strong>tent generally to be less<br />

than 1% of dry weight.<br />

Silt site<br />

Figure 4 shows temperature data recorded at<br />

the silt site for two recording periods. The<br />

1947-48 data were recorded within 60 m of the<br />

present installati<strong>on</strong>. Both sets show the<br />

average ground temperature to be less than<br />

-0.5S'c at a depth of 9.14 m. Both the average<br />

value and the c<strong>on</strong>tours indicate no warming<br />

of the permafrost at this site after 38 years.<br />

The minimum surface temperature recorded during<br />

this study was -6.O'C, recorded <strong>on</strong> 26<br />

February, and temperatures within 1.O'C of<br />

this value occurred within 1 m of the surface<br />

through 4 April. This period saw the highest<br />

resistivities occurring at the surface.<br />

The pa data are c<strong>on</strong>toured in Figure 5. Lower<br />

resistivities of the active layer above 1.5 m<br />

are c<strong>on</strong>sistent with the higher ground temperatures.<br />

Values of 200-500 ohm-m occurred in the<br />

active layer at the time of maximum seas<strong>on</strong>al<br />

thaw, and values greater than 10,000 ohm-m<br />

occurred at the time of minimum ground temperatures.<br />

Below 2 m the readings at any<br />

depth show little change with time. Layering<br />

can be seen by the c<strong>on</strong>touring, which reveals<br />

distinct z<strong>on</strong>es where values less than 3,000<br />

ohm-m occur.<br />

Figure 6 compares average apparent resistivity<br />

(p ) with average ground temperature and<br />

vofumetric ice c<strong>on</strong>tent Bv. The lowest values<br />

1<br />

930<br />

of Fa occur above 4 m depth where summer<br />

resistivities bring Pa down to about 1000 ohmm.<br />

Between 4 and 6 m, Bv is high and Pa nears<br />

10,000 ohm-m. Despite no significant change<br />

in Bv ox T (seas<strong>on</strong>ally as well), between 6 and<br />

10 m, pa decreases to around 2000 ohm-m. pa<br />

then increases near the bottom as ev decreas-<br />

es. Previous field studies at this site by<br />

Arc<strong>on</strong>e et al. (1978) c<strong>on</strong>firm that values in<br />

the 1000 to 3000-ohm-m range are characteristic<br />

of this material beneath the active layer.<br />

However, laboratory studies of Hoekstra et al.<br />

(1974) have shown that Fairbanks silt with<br />

varying organic c<strong>on</strong>tent (up to 10% of dry<br />

weight) can range several thousand ohm-m higher<br />

than silt without organics. Therefore, it<br />

is speculated that the z<strong>on</strong>es of highest resistivity<br />

may be z<strong>on</strong>es of higher organic c<strong>on</strong>tent.<br />

I 1985 1 1986 I<br />

r '1<br />

''OOOd<br />

r 1<br />

3,000<br />

-<br />

5,000<br />

- 7<br />

Fig. 5 Apparent resistivity c<strong>on</strong>tours as a<br />

functi<strong>on</strong> of depth for the silt: site recorded<br />

between July 1985 and September 1986.

Averme Aaoarent Resistivitv Measured<br />

Volumetric<br />

Fig. 6 The average apparent resistivity compared with the average<br />

ground temperature and volumetric ice c<strong>on</strong>tent as a functi<strong>on</strong> of depth at<br />

the silt site.<br />

DISCUSSION OF ERRORS<br />

C<strong>on</strong>tact+&sistance<br />

TWO sources of error in determining pa are<br />

c<strong>on</strong>tact resistance and effects of the borehole<br />

itself. C<strong>on</strong>tact resistance results from poor<br />

c<strong>on</strong>tact between the electrodes and the ground;<br />

thus causing intense electric fields around<br />

the c<strong>on</strong>tact points as current is impeded. The<br />

result is an increase in pa as c<strong>on</strong>tact resistance<br />

adds in series to the ground resistance.<br />

Borehole effects are caused by the<br />

presence of the borehole itself, which, in<br />

this case, is a highly resistive cylindrical<br />

column that must be accounted for in the computati<strong>on</strong><br />

of pa.<br />

c<br />

t<br />

x<br />

a<br />

4<br />

30cm<br />

o 60cm<br />

After the ABS pipe was inserted into the borehole,<br />

a thawed silt (or sand) slurry was<br />

poured into the annulus between the pipe and<br />

the hole wall. The pipe was then rotated and<br />

tamped to enforce settling. Since measurements<br />

did not commence until midduly (90 days after<br />

installati<strong>on</strong>), we are c<strong>on</strong>fident of complete<br />

freezeback. If c<strong>on</strong>tact resistance is a serious<br />

problem throughout the array, then log- a<br />

log plot of pa vs 3 separati,<strong>on</strong> will have a<br />

slope greater than 1. This was not seen-in<br />

the data recorded using telescoping up-hole<br />

and down-hole soundings. Furthermore, general<br />

agreement between 30- and 60-cm a separati<strong>on</strong><br />

profiles, recorded at the silt site and shown<br />

in Figure 7, implies no c<strong>on</strong>tact resistance<br />

problems.-The exact effect of the borehole<br />

itself is almost impossible to compute because<br />

of the asymmetrical placing of the electrodes<br />

(the string of electrodes may not be centered<br />

exactly in the hole). Nevertheless, an error<br />

was estimated using a theoretical model in<br />

which the electrodes are placed at the surface<br />

of a two-layer medium, the upper layer of<br />

which is infinitely resistive and equal to the<br />

pipe column radius (1.9 cm) in thickness,<br />

while the lower layer is of resistivity p .<br />

The computati<strong>on</strong>s revealed that<br />

a = 30 cm<br />

the error is 8.4% at p = 500 ohm-m and c<strong>on</strong>-<br />

93 1<br />

100 0 4 8 12<br />

Dtpth (m)<br />

Fig. 7 Resistivity profiles recorded at the<br />

silt site using separati<strong>on</strong>s of 30 and 60 cm.<br />

tinually decreases to 0.24% at 15,000 ohm-m.<br />

At values less than 500 ohm-m, the error is<br />

much more appreciable although within the correct<br />

order of magnitude. Such low values<br />

of pa were recorded near the surface where<br />

surface effect may be more significant than<br />

that of the borehole. In any case <strong>on</strong>e may<br />

argue that the effect of the borehole must be<br />

insignificant because the electrode spacing<br />

was so much greater than the borehole radius.<br />

SUMMARY AND CONCLUSIONS<br />

The observati<strong>on</strong>s provide a good quantitative<br />

record of seas<strong>on</strong>al variati<strong>on</strong>s in resistivity<br />

and temperature at two sites in the disc<strong>on</strong>tinuous<br />

permafrost z<strong>on</strong>e. The results also<br />

show that apparent ground resistivity can be

measured in situ with permanently installed<br />

arrays in perennially frozen soils without<br />

significant effects from c<strong>on</strong>tact resistance or<br />

the presence of the electrode installati<strong>on</strong>.<br />

The values obtained correlated well with the<br />

lithology at the alluvium site, and showed<br />

some unexpectedly high values at the ice-rich<br />

silt site in view of the relatively high (> -<br />

1.0'C) in-situ temperatures at depth. The<br />

general resistivity range at the silt site<br />

agrees well with previous research there,<br />

which used surface based methods, while the<br />

higher values obtained may be indicative of<br />

higher organic c<strong>on</strong>tent. In c<strong>on</strong>trast with the<br />

data recorded at the alluvium site, the silt<br />

site shows distinct values more c<strong>on</strong>sistent<br />

with temperature changes below the active<br />

layer and greater seas<strong>on</strong>al variati<strong>on</strong> in the<br />

active layer resistivity. The results thus<br />

dem<strong>on</strong>strate that ground based resistivity SUKveys<br />

in interior Alaska can be str<strong>on</strong>gly<br />

affected by seas<strong>on</strong>al variati<strong>on</strong>s and large<br />

variati<strong>on</strong>s in properties and distributi<strong>on</strong> of<br />

fine-grained soils.<br />

REFERENCES<br />

ACFEL (1950).<br />

Investigati<strong>on</strong> of military c<strong>on</strong>structi<strong>on</strong> in<br />

arctic and subarctic regi<strong>on</strong>s, comprehensive<br />

report 1945-48; Main report and appendix<br />

111-Design and c<strong>on</strong>structi<strong>on</strong> studies at Fairbanks<br />

research area. Tech. Rep. 28, <strong>Permafrost</strong><br />

Divisi<strong>on</strong>, U.S. Amy Corps of Engineers,<br />

U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and<br />

Engineering Laboratory, Hanover, New<br />

Hampshire.<br />

Andersen, D M, Tice, A R ti McKim, H L (1973).<br />

The unfrozen water in frozen soils. <strong>Permafrost</strong>:<br />

Proceedings of an <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, 257-288, Nati<strong>on</strong>al Academy of<br />

Sciences, Nati<strong>on</strong>al <strong>Research</strong> Council,<br />

Washingt<strong>on</strong>, D.C.<br />

Arc<strong>on</strong>e, S A & Delaney, A J (this volume) .<br />

Borehole investigati<strong>on</strong>s of the electrical<br />

properties of frozen silt. Proc. V <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>,<br />

Tr<strong>on</strong>dheim, Norway.<br />

Arc<strong>on</strong>e, S A & Delaney, A J (in press).<br />

Investigati<strong>on</strong>s of dielectric properties of<br />

some frozen materials using cross borehole<br />

radiowave pulse transmissi<strong>on</strong>s. CRREL<br />

report. U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and<br />

:Engineering Laboratory, Wanover, New<br />

Hampshire.<br />

Arc<strong>on</strong>e, S A & Delaney, A J (1985).<br />

Dielectric studies of permafrost using<br />

cross-borehole VHF pulse propagati<strong>on</strong>. Proc.<br />

Workshop <strong>on</strong> <strong>Permafrost</strong> Geophysics, Golden,<br />

Colo., CRREL Special Report 85-5, 3-5, U.S.<br />

Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering<br />

Laboratory, Hanover, New Hampshire.<br />

Arc<strong>on</strong>e. S A, Sellmann, P V & Delaney, A J<br />

(1978).<br />

Shallow electromagnetic investigati<strong>on</strong>s-of<br />

permafrost. Proc. 111 <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g><br />

<strong>on</strong> <strong>Permafrost</strong>, (l), 501-507, Edm<strong>on</strong>t<strong>on</strong>,<br />

Alberta.<br />

Arc<strong>on</strong>e, S A, Sellmann, P V & Delaney, A J<br />

(1979).<br />

Effects of seas<strong>on</strong>al changes and ground ice<br />

<strong>on</strong> electromagnetic surveys of permafrost.<br />

CRREL Report 79-23, U.S. Amy Cold Regi<strong>on</strong>s<br />

<strong>Research</strong> and Engineering Laboratory,<br />

Hanover, New Hampshire.<br />

Ehrenbard, R L, Hoekstra, P L Rozenberg, G<br />

(1983).<br />

Transient electromagnetic soundings for<br />

permafrost mapping. Proc. 111 <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>, (I), 272-277,<br />

Edm<strong>on</strong>t<strong>on</strong>, Alberta.<br />

Hoekstra, P (1978). Electromagnetic methods<br />

for mapping shallow permafrost.<br />

Geophysics, (43), 4, 782-787.<br />

Boekstra, P, Sellmann, P V & Delaney, A<br />

(1974).<br />

Airborne resistivity mapping of permafrost<br />

near Fairbanks, Alaska. CRREL <strong>Research</strong><br />

Report 324, U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong><br />

and Engineering Laboratory, Hanover, New<br />

Hampshire.<br />

Koziar, A, & Strangway, D W (1978). <strong>Permafrost</strong><br />

mapping by audiofrequency magnetotellurics.<br />

Canadian Journal of Earth Sciences, (15),<br />

10, 1539-1546.<br />

Labo, J (1987).<br />

A practica1,introducti<strong>on</strong> to borehole geophysics,<br />

Geophysical References, (2), 70,<br />

Norman Crook, Editor. Society of Explorati<strong>on</strong><br />

Geophysicists, Tulsa, Oklahoma.<br />

Parkhomenko, E I (1967).<br />

Electrical properties of rock. Translated<br />

from Russian by G.V. Keller, Plenum Press,<br />

New York.<br />

P&d, T L (1958).<br />

Geology of the Fairbanks (D-2) Quadrangle,<br />

Alaska, U.S. Geological Survey Geological<br />

Quadrangle Map 64-110.<br />

Sinha, A K (1976). Determinati<strong>on</strong> of ground<br />

c<strong>on</strong>stants of permafrost terrains by an electromagnetic<br />

method.<br />

Canadian Journal of Earth Sciences, (13),<br />

429.<br />

Wenner, F (1915).<br />

A method of measuring earth resistivity,<br />

U.S. Bureau of Standards Bulletin 12.<br />

932

PERMAFROST CONDITIONS IN THE SHORE AREA AT SVALBARD<br />

0. Gregersenl and T. Eidsmoen2<br />

1Norwegian Geotechnical Institute, Oslo, Norway<br />

2Norwegian State Railways, Drammen, Noway (formerly of NGI)<br />

ABSTRACT. <strong>Permafrost</strong> registrati<strong>on</strong>s at Svalbard are few, and have so far been restricted to inland<br />

areas. This article describes a recent project which has studied permafrost c<strong>on</strong>diti<strong>on</strong>s in the shore<br />

area of Svalbard. Two representative sites, L<strong>on</strong>gyearbyen and Svea, were chosen for the project. At<br />

both sites thermistors were permanently installed in 100 m deep drillholes. The data c<strong>on</strong>firm the<br />

previous assumpti<strong>on</strong>s of no offshore permafrost and indicate the shore area to be a z<strong>on</strong>e of "warm"<br />

permafrost. The data also give some interesting informati<strong>on</strong> <strong>on</strong> the geological history.<br />

INTRODUCTXON<br />

$5<br />

With a mean annual temperature- of about -6OC.<br />

the permafrost in central parts of Svalbard is<br />

classified as "cold permafrost". The geological<br />

history of Svalbard, however, makes the<br />

existence of offshore permafrost unlikely.<br />

Therefore, the shore area ir believed to form a<br />

transiti<strong>on</strong> z<strong>on</strong>e between frozen and unfrozen<br />

ground. a z<strong>on</strong>e of "warm permafrost". As "warm<br />

permafrost" very often presents difficult foundati<strong>on</strong><br />

c<strong>on</strong>diti<strong>on</strong>s, it ia important to have this<br />

problem investigated prior to design of<br />

c<strong>on</strong>structi<strong>on</strong>s in the shore area.<br />

Previously no observati<strong>on</strong>s or analysis have been<br />

carried out to investigate this phenomen<strong>on</strong>.<br />

Neither have the few existing shore area<br />

c<strong>on</strong>structi<strong>on</strong>s given any reliable informati<strong>on</strong> <strong>on</strong><br />

this questi<strong>on</strong>.<br />

During the period December 1986 to December 1987<br />

this problem was given c<strong>on</strong>siderable attenti<strong>on</strong> by<br />

NGI, and a project includlng both temperature<br />

measurements and a theoretical analysis was<br />

carried out. Recent interest in this problem<br />

has grown from increased activity aasociated<br />

with reeourca prospecting both <strong>on</strong> Svalbard and<br />

ita near-shore areas. The possible exploiting of<br />

new resources in the Svalbard regi<strong>on</strong> will make<br />

the shore area a very important z<strong>on</strong>e for the<br />

locati<strong>on</strong> of different types of c<strong>on</strong>structi<strong>on</strong>s<br />

such ae docks, storage buildings and supply<br />

facilities. Aha, the shore area is an important<br />

regi<strong>on</strong> for pipeline crossings.<br />

TEST SITES AND INSTALLATIONS<br />

Two Locati<strong>on</strong>s were chosen for measurements of<br />

temperatures in the ground, L<strong>on</strong>gyearbyen and<br />

Svea, see Figure 1. The climatic c<strong>on</strong>diti<strong>on</strong>s are<br />

much the same at the two locati<strong>on</strong>s, with a mean<br />

annual temperature of about -6OC. However, the<br />

recent geological history is very different at<br />

the two locati<strong>on</strong>s. At L<strong>on</strong>gyearbyen the shore<br />

area is "old land", raised about sea level after<br />

the last glaciati<strong>on</strong>, probably a few thousand<br />

933<br />

Figure 1<br />

Map of Svalbard showing locati<strong>on</strong> of<br />

test sites L<strong>on</strong>gyearbyen and Svea.<br />

years ago. The soil profile is <strong>on</strong>e of marine<br />

clay and silt overlain by fluvioglacial dcposits.<br />

The Svea Lowland is "new land", about 700<br />

years old. The area was submerged until surges<br />

of the Paula glacier across the van Mijen fjord<br />

compressed the seabed sediments and lifted them<br />

above sea level, Haga (1978) and P&w& (1981). The<br />

locati<strong>on</strong>s are shown in more detail in Figure 2.<br />

The temperature measurement programme was based<br />

<strong>on</strong> preliminary theoretical calculati<strong>on</strong>s of the<br />

thermal c<strong>on</strong>diti<strong>on</strong>s. The surface and water temgeratures<br />

Were assumed to be -6OC and +I°C respsctively,<br />

and the temperature gradient to be<br />

50 m/OC. Thermal c<strong>on</strong>ductivities were varied<br />

from 1.7 to 1.9 W/mK for clay and from 2.5 to<br />

3.5 W/mK for bedrock. The results of these<br />

calculati<strong>on</strong>s are presented in Figure 3. The<br />

calculati<strong>on</strong>s show clearly that temperature<br />

measurements must be taken to c<strong>on</strong>siderable<br />

depths to give the necessary informati<strong>on</strong>. For<br />

practical reas<strong>on</strong>s the depth was limited to 100 m.<br />

The figure also shows that the sea influences<br />

the ground temperatures to some 200 m from<br />

0

L<br />

Fiqure 2<br />

Test sites L<strong>on</strong>gyearbyen (a) and Svea (b) showing locati<strong>on</strong>s of thermistor strings.<br />

the shore-line. Reference temperature measurements<br />

must therefore be recorded at a distance<br />

of 200 m or further away from the shore-line.<br />

At Svea the reference measurements were taken<br />

same 200 m from the ahore-line, and at L<strong>on</strong>gyearbyen<br />

some 500 I. The thermiBtor strings are<br />

ahown in Figure 3. Four 100 m strings were prepared<br />

with thermistors at 10, 18, 20, 30, 40,<br />

50, 15 and 100 m depths. In additi<strong>on</strong>, to obtain<br />

a detailed profile of temperatures within the<br />

depth interval influenced by annual variati<strong>on</strong>s<br />

in temperatures and surface c<strong>on</strong>diti<strong>on</strong>e, meparate<br />

10 m l<strong>on</strong>g thermistor strings were prepared for<br />

installati<strong>on</strong> in the shore-line at Svea and<br />

L<strong>on</strong>gyearbyen, with thermiators placed at depths<br />

of 1, 2, 3, 4, 5, 6, 8 and 10 m.<br />

mstmt.<br />

shore-line hole in L<strong>on</strong>gyearbyen which was<br />

stopped at a depth of 10.5 m instead of 100 m.<br />

0 o ,,<br />

25<br />

E<br />

$ 50<br />

lime for tempwature to stabilize, days<br />

50 100 150 200 250<br />

2.C €;cess tomperdture<br />

I 1<br />

I5<br />

tlM<br />

i .lY<br />

-Tmpwature grad#dL"'"<br />

ZOmPC<br />

250<br />

Fioura 3<br />

0-c /<br />

"+<br />

I L= '<br />

T1-Tl thermistors<br />

General profile showing results of<br />

thermal calculati<strong>on</strong>s and locati<strong>on</strong><br />

of thermistor strings.<br />

The thermistor strings were installed<br />

predrilled holes. Drilling was performed during<br />

the period October to December 1986, using<br />

diam<strong>on</strong>d core drill bits of internal diameter<br />

42.5 mm and saline water as a drilling fluid.<br />

The temperature of the fluid varied from O°C to<br />

5OC. The depth to bedrock at Svea was 40 m at<br />

the share-line locati<strong>on</strong> and 30 m at the <strong>on</strong>-land<br />

locati<strong>on</strong>; at L<strong>on</strong>gyearbyen the depths were > 70 m<br />

and 10 m respectively. Drilling of a 100 m deep<br />

hole took between 2 and 3 days; all drilling was<br />

carried out according to plan, except for the<br />

934<br />

100<br />

Piaura 4<br />

Diagram showing the time for temperature<br />

to stabilize after drilling<br />

a 100 m deep hole at Svea.<br />

GROUND TEMPERATURE INCREASE DUE TO HEAT FROM<br />

DRILLING<br />

The ground temperature around the boFings<br />

increased during drilling, and measurements ware<br />

taken to study the temperature stabilizati<strong>on</strong><br />

procaas over the depth profile. Figure 4<br />

Illustrates this process for the 100 m deep<br />

"<strong>on</strong>-land" drill hole at Sveu. The figure shows<br />

temperature increase that are highest near the<br />

surface and which diminish rapidly with depth.<br />

C<strong>on</strong>seQuently dissipati<strong>on</strong> of excess heat takes<br />

lese time in the lower part of the profile than<br />

in the upper part. For example, at a depth of<br />

100 m the excess temperature is equalized 8 days

~<br />

after completi<strong>on</strong> of drilling, while at a depth<br />

of 10 m the time tgken is 200 days; an excess<br />

temperature of 0.2 C is reached after 3 days at<br />

a depth of 100 m and after 100 days at a depth<br />

of 10 m. The observati<strong>on</strong>s dem<strong>on</strong>strate clearly<br />

that stabilizati<strong>on</strong> of temperatures in drill<br />

holes takes c<strong>on</strong>siderable time (m<strong>on</strong>ths) and indicate<br />

measurements of ground temperature taken<br />

shortly after completi<strong>on</strong> of drilling (days or<br />

weeks) may not be reliable.<br />

REFERENCE TEMPERATURE PROFILES.<br />

Figure 5 shows the measured temperature profiles<br />

at L<strong>on</strong>gyearbyen and Sveagruva. While the<br />

refe ence profiles give a mean temperature of<br />

-6.1<br />

ti<br />

C <strong>on</strong> the surface. the temperature gradients<br />

are very different for the two sftgs. At<br />

L<strong>on</strong>gyearbyen the gradient is 30 m/ C while at<br />

Svea it is 20 m/OC. Extrapolati<strong>on</strong> of the temperature<br />

profiles with depth gives 190 m of permafrost<br />

at L<strong>on</strong>gyearbyen and 128 m .at Svea. The<br />

temperature profile from L<strong>on</strong>gyearbyen shows c<strong>on</strong>siderable<br />

irregulatities in the upper 30 to 40 m.<br />

and a c<strong>on</strong>stant average temperature distributi<strong>on</strong>.<br />

This is not found at Svea where the profile<br />

shows a linear increase with depth. Lisstrrrl<br />

(1980) xegorts typically vertical greclients in<br />

prsvioua measurements which he attributes to the<br />

warm climatic period between 1920 and 1960.<br />

Thermal gradients of 30 m/OC m a 20 m/OC are<br />

steep compared to previous measurements at<br />

Svalbard, where Liestrl (1960) reports thermal<br />

gradients between 130 m/'C and 40 m/'C. The<br />

extreme steep thermal gradient at Svea indicates<br />

that the thermal regime in this area is<br />

not in equilibrium. but in a state of permafrost<br />

growth. The likely explanati<strong>on</strong> for thie is that<br />

the flat area, where the temperature profile is<br />

located, was originally submerged. Haga (1978)<br />

and Pew& (1981) proposed that surges of the<br />

Paula glacier across the van Mijen fjord compressed<br />

seabed sediments and lifted them above<br />

sea-level to form the preeent Svea Lowland. The<br />

last surge is dated to some 700 yerra ago.<br />

Temperature, .C<br />

-IO -9 -8 -1 -6 -5 4 -3 -2 -1 0<br />

0<br />

10<br />

20<br />

30<br />

I 40<br />

d<br />

0 so<br />

0<br />

60<br />

70<br />

80<br />

90<br />

100<br />

Fiuure I<br />

Measured temperature profiles<br />

L<strong>on</strong>gyearbyan and Svea.<br />

Simple thermal calculati<strong>on</strong>s have been carried<br />

out to test out this theory. The analysis assumes<br />

that the original surface temperature was<br />

o0C, the temperature gradient is equal to the<br />

gradient in L<strong>on</strong>gyearbyen (40 doc) and the surface<br />

was sudclenlg exposed to a surface temperature<br />

of -6.1 C. Results of the exercise,<br />

together with the measured temperature profile,-<br />

are presented in Figure 6. Theoretically, ana<br />

for these assumpti<strong>on</strong>s, the present thermal gradisnt<br />

is reached 500 years after llfting the<br />

area above sea level; however the actual<br />

measured temperatures are reached about 1000<br />

years after the uplift of the land. While the<br />

calculati<strong>on</strong>s do not give full agreement with the<br />

measured temperatures, the simplicity of the<br />

exercise 18 such that it is fair to say the<br />

calculati<strong>on</strong>s fit surprisingly well with the<br />

theory.<br />

Temperature, 'C<br />

Blcrure 6<br />

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5<br />

0 1 , i ! b , , , 7 ~ \ m , ' ' 1<br />

I>""<br />

Calculated permafrost penetrati<strong>on</strong><br />

for newly expoeed land in Svea, as a<br />

functi<strong>on</strong> with time. Measured<br />

temperature profiles (700 years).<br />

TEMPERATURE PROFILES AT THE SWORE LINE<br />

Measured temperature profiles at the shoreline<br />

are also presented in Figure 6. Comparing the<br />

data from L<strong>on</strong>gyearbyan and Svea, the temperatures<br />

reflect the same situati<strong>on</strong> that was<br />

observed for the reference profiles. Temperatures<br />

at L<strong>on</strong>gyearbyen are c<strong>on</strong>siderably lower<br />

than those at Svea and, as discussed above,<br />

result from the difference in geological history<br />

of tho two locati<strong>on</strong>s. It should also be noted<br />

that, as expected, temperatures at the shoreline<br />

are much influenced by the heat resource of<br />

the sea. At a given depth the shore-line tamperaturc<br />

is about 2OC higher than the reference<br />

temperature at the same site.<br />

Isotherms are drawn from the measurements of<br />

temperature and are presented in Figure 7. The<br />

figure shows the shore area to be a z<strong>on</strong>e of permafrost<br />

temperatures close to zero. At both<br />

sites the permafrost probably extends 30 to 40 m<br />

out from the shore-line. It also seems likely<br />

that the temperatures at ,shallow depths (10 to<br />

20 m) are not significantly different for the

DistmtR <strong>on</strong> land, m<br />

Oirtmrc<br />

offrhorc. m<br />

500 450 (00 350 300 250 200 150 100 50 0 50 100<br />

Fimre 7 Isotherms, based <strong>on</strong> measured tempe- '<br />

ratures and theoretical calculati<strong>on</strong>s.<br />

two sites, indicating that at shallow depths the<br />

temperature is mainly dependent <strong>on</strong> local surface<br />

c<strong>on</strong>diti<strong>on</strong>s such as currents, ice c<strong>on</strong>diti<strong>on</strong>s, and<br />

shore-line topography.<br />

Results of preliminary calculati<strong>on</strong>s of the thermal<br />

c<strong>on</strong>diti<strong>on</strong>s are included in Bigure 7. In the<br />

shore area there is a reas<strong>on</strong>able fit between<br />

calculated and measured isotherms. The<br />

increasing discrepancy away from the shore-line<br />

is due to the incorrect assumpti<strong>on</strong> for the<br />

reference thermal gradient, 50 m/%. compared to<br />

meaeured values of 30 m/OC and 20 m/OC. Revised<br />

calculati<strong>on</strong>s using the corruct reference thermal<br />

gradient would give a good fit with the<br />

isotherms based <strong>on</strong> measured data.<br />

DISCUSSION<br />

The field observati<strong>on</strong>s c<strong>on</strong>firm that the shore<br />

area is a z<strong>on</strong>e of warm permafrost. Inside the<br />

shore-line the mean temperature is 1-2OC below<br />

zero, while outside the shore-line the surface<br />

temperature is above zero with transiti<strong>on</strong> to<br />

permafrost c<strong>on</strong>diti<strong>on</strong>s at a fsw meters depth. It<br />

is probable that these c<strong>on</strong>diti<strong>on</strong>s are largely<br />

representative of the shore z<strong>on</strong>e al<strong>on</strong>g entire<br />

southern an& western coastal areas of Svalbard.<br />

However local c<strong>on</strong>diti<strong>on</strong>s will have a significant<br />

influence <strong>on</strong> the temperature c<strong>on</strong>diti<strong>on</strong>s et<br />

shallow dsptha, the most important z<strong>on</strong>e for<br />

engineering c<strong>on</strong>structi<strong>on</strong>. These c<strong>on</strong>diti<strong>on</strong>s are<br />

currents, ice c<strong>on</strong>diti<strong>on</strong>s and shore-line<br />

topography. Another important factor<br />

influencing the foundati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s is the<br />

soil. At temperatures close to zero apscisl<br />

emphasis must also be given to the aalinity:<br />

With a high salinity the soil can.be virtually<br />

unfrozen even at temperatures of -2 to -3'~.<br />

Oregersen (1983).<br />

The study has shown that geotechnical investigati<strong>on</strong>s<br />

of a c<strong>on</strong>structi<strong>on</strong> site may be restricted<br />

to analysis of the local climatic c<strong>on</strong>diti<strong>on</strong>s,<br />

measurement of the temperatures at shallow depth<br />

and analysis of the soil c<strong>on</strong>diti<strong>on</strong>s. Such<br />

informati<strong>on</strong> would be sufficient for foundati<strong>on</strong><br />

design of most c<strong>on</strong>structi<strong>on</strong>s when supplemented<br />

with the data from the present study. One<br />

should, however, bear in mind that thermal c<strong>on</strong>diti<strong>on</strong>s,<br />

as revealed in the Svalbard shore-line<br />

area, are very unfavaurable f o ~ foundati<strong>on</strong> engineering.<br />

It is therefore essential that sufficient<br />

and appropriate local investigati<strong>on</strong>s be<br />

carried aut.<br />

936<br />

CONCLUSIONS<br />

1. Heat accumulati<strong>on</strong> from drilling in permafrost<br />

ground can be c<strong>on</strong>miderble and may<br />

take m<strong>on</strong>ths to dissipate. Reliable ground<br />

temperature profiles are obtained 6-6 m<strong>on</strong>ths<br />

after completi<strong>on</strong> of the drilling operati<strong>on</strong>.<br />

2. Ground temperature profiles reflect the<br />

recent geological history of the two areas.<br />

Temperature profiles at the 700 year old<br />

Svea Lowland are markedly warmer than at the<br />

much older land at L<strong>on</strong>gyearbyen. At Svea<br />

the thermal c<strong>on</strong>dit<strong>on</strong>s in the ground have not<br />

yet stabilized. A state of active germafrost<br />

growth has been documented.<br />

3. Observati<strong>on</strong>s c<strong>on</strong>firm that the shore-line is<br />

a z<strong>on</strong>e of warm permafrast, and that with<br />

mean temperatures between +1 and -2OC the<br />

thermal stability is delicate. From a faundati<strong>on</strong><br />

engineering point of view the shore<br />

area can be a difficult z<strong>on</strong>e.<br />

4. Thermal c<strong>on</strong>diti<strong>on</strong>s of a land area are primarily<br />

a functi<strong>on</strong> of the overall climatic<br />

situati<strong>on</strong>. Tha recorded temperature profiles<br />

are therefore in general regreaentative<br />

of the entire shore z<strong>on</strong>e of the southern and<br />

western coastal areas of Svalbard. However<br />

local c<strong>on</strong>diti<strong>on</strong>s will have a significant<br />

influence <strong>on</strong> tha c<strong>on</strong>diti<strong>on</strong>e at shallow<br />

depth. When evaluating the thermal c<strong>on</strong>diti<strong>on</strong>s<br />

of an area with respect to foundati<strong>on</strong><br />

engineering, both general knowledge<br />

representative of the regi<strong>on</strong> and data from a<br />

study of local c<strong>on</strong>diti<strong>on</strong>s should be used.<br />

Such data are for example the local climate,<br />

currents, ice c<strong>on</strong>diti<strong>on</strong>s, shore-line<br />

topography and soil c<strong>on</strong>diti<strong>on</strong>s.<br />

ACKNOWLEDGEMENTS<br />

The authors are very grateful to Store Norske<br />

Spitsbergrn Kulkompani, Svalbard, for their<br />

valuable assistance during installati<strong>on</strong> wark in<br />

the field. The project is supported by Statoil.<br />

LIST OF REBERENCES<br />

Gregersen, 0.. A. Phukan and T. Johansen (1983)<br />

Engineering properties and foundati<strong>on</strong> design<br />

alternatives in marine Svea clay, Svalbard.<br />

Intsrnati<strong>on</strong>al <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> '<strong>Permafrost</strong>. 4.<br />

Rairbanks, Alaska 1983. Proceedings. pp.<br />

384-388. Ale0 publ. in: Norwegian Qeotechnical<br />

Institute, Oslo. Publ. No. 159, 1985.<br />

Hap, 0. (1978)<br />

A study of the effect of the Paula glaciar<br />

<strong>on</strong> the sediments in the inner part of van<br />

Mijsn fjord. Thesis (in Norwegian). University<br />

of Oslo.<br />

Liestd, 0. (1980)<br />

<strong>Permafrost</strong> c<strong>on</strong>diti<strong>on</strong>s in Spitrbergen.<br />

Frost Acti<strong>on</strong> in Soils, Oslo. Publ. No. 21.<br />

Plwl, T.L., D.E. Rowan and R.H. Few& (1981)<br />

Engineering geology of the Svea Lowland,<br />

Spitsbergen, Svalbard. Frost Acti<strong>on</strong> in<br />

Soils, Oslo. Publ. No. 23.

CORE DRILLING THROUGH ROCK GLACIER-PERMAFROST<br />

W. Haeberli, J. Huder, H.-R. Keusen, J. Pika and H. Rathlisberger<br />

Versuchsanstalt fur Wasserbau, Hydrologie und Glaziologie, ETH Zurich, Switzerland<br />

SYNOPSIS: Rock glaciers are perennially frozen debris masses which slowly creep down mountain slopes.<br />

Their ice c<strong>on</strong>tains undeciphered informati<strong>on</strong> about the evoluti<strong>on</strong> of periglacial envir<strong>on</strong>ments since the<br />

last Ice Age. In additi<strong>on</strong>, creep of rock glacier permafrost takes place under practically c<strong>on</strong>stant<br />

temperatures, stresses and strain rates. Rock glacier flow is therefore a natural large-scale/<br />

l<strong>on</strong>gterm experiment <strong>on</strong> the steady state creep of ice-rock mixtures. In order to study these aspects,<br />

a core drilling project has been started <strong>on</strong> the active rock glacier Murtil I, Piz Corvatsch, Engadin,<br />

Swiss Alps. The drilling operati<strong>on</strong> took place in spring 1987. Borehole temperature at 15m depth is<br />

close to -2OC. <strong>Permafrost</strong> reaches down to the severely fissured and highly permeable bedrock at about:<br />

50m depth. Beneath a 3m-active layer, it c<strong>on</strong>tains (with increasing depth) pure and massive ice (12m),<br />

supersaturated frozen sands with ice lenses (17m), and ice-bearing blocks (18m).<br />

INTRODUCTION<br />

In mountain regi<strong>on</strong>s, ice-rich permafrost often<br />

occurs within steep, debris covered slopes. With<br />

increasing thickness of the ice bearing debris,<br />

stresses can build up which trigger the creep of<br />

the permafrost. During the process of permafrost<br />

creep, the original debris accumulati<strong>on</strong> - for<br />

instance a scree slope or a moraine - is slowly<br />

deformed. The product of this deformati<strong>on</strong>al<br />

process is the rock glacier, certainly the most<br />

striking phenomen<strong>on</strong> of mountain permafrost.<br />

Based <strong>on</strong> the evidence now accumulated from<br />

geomorphological observati<strong>on</strong>s, geophysical<br />

soundings, and from geodetic and photogrammetric<br />

measurements, rock glaciers can be assumed to<br />

flow in a steady-state creep mode under fairly<br />

c<strong>on</strong>stant strqsses, strain rates and temgeratures.<br />

They k<strong>on</strong>tain large amounts of various<br />

kinds of c<strong>on</strong>gelati<strong>on</strong> ice (Shumskii 1964) -<br />

interstitial ice, ice lenses and massive ice -<br />

as well as sometimes also buried sedimentary ice<br />

from avalanche c<strong>on</strong>es and glacierets. First attempts<br />

to model rock glacier flow indicate that<br />

the age of most rock glacier permafrost is in<br />

the order of I O3 to 1 O4years, i.e. comparable to<br />

the durati<strong>on</strong> of the Holocene time period (Wahrhaftig<br />

ana Cox 1959, Olyphant 1983, Haeberli<br />

1985, Vitek and Giardino 1987). In'order to gain<br />

more insight into these aspects, a core drilling<br />

project has been recently started in the Swiss<br />

Alps. The present c<strong>on</strong>tributi<strong>on</strong> briefly describes<br />

the c<strong>on</strong>cept of the project, the investigated<br />

site, the drilling operati<strong>on</strong> and some first<br />

results.<br />

CONCEPT OF THE PROJECT<br />

Flow of rock glacier permafrost can be c<strong>on</strong>sidered<br />

to be a natural large-scale and l<strong>on</strong>g-term<br />

experiment <strong>on</strong> the creep of rock-ice mixtures.<br />

937<br />

Compared to laboratory tests, this natural experiment<br />

has great advantages as well as severe<br />

limitati<strong>on</strong>s. The greatest advantage is given by<br />

the fact that steady state creep obviously takes<br />

place; and that boundary c<strong>on</strong>diti<strong>on</strong>s vary little<br />

over extended time periods, mainly due to the<br />

thermal inertia of ice-rich permafrost. It is,<br />

however, very difficult to exactly define these<br />

boundary c<strong>on</strong>diti<strong>on</strong>s; the 3-dimensi<strong>on</strong>al distributi<strong>on</strong><br />

of ice c<strong>on</strong>tent, temperature, stress and<br />

strain rate cannot be accurately studied by surface<br />

observati<strong>on</strong>s and geophysical prospecting<br />

techniques al<strong>on</strong>e (Haeberli 1985). As an important<br />

step towards at least partially overcoming<br />

these problems, it was decided to drill through<br />

the permafrost of an active rock glacier, to<br />

take core samples from the permafrost table down<br />

to bedrock, and to prepare the borehole for<br />

l<strong>on</strong>g-term m<strong>on</strong>itoring of temperature and deformati<strong>on</strong>.<br />

The results of core analysis and borehole<br />

observati<strong>on</strong>s are expected to furnish basic input<br />

data for modelling large-scale permafrost creep<br />

(cf. Sayles 1968, Hooke et al. 1972, Haynes<br />

1978, Vyalov 1978, Echelmeyer and Wang 1987).<br />

The ice within rock glacier permafrost is assumed<br />

to have farmed within n<strong>on</strong>c<strong>on</strong>solidated sediments.<br />

In c<strong>on</strong>trast to high-mountain firn and<br />

glacier ice, it probably originates from frozen<br />

groundwater rather than from directly-accumulated<br />

layers of atmospheric precipitati<strong>on</strong>. Rockglacier<br />

permafrost could c<strong>on</strong>tain informati<strong>on</strong> <strong>on</strong><br />

the evoluti<strong>on</strong> of the Alpine envir<strong>on</strong>ment and so<br />

be complementary to the informati<strong>on</strong> extracted<br />

from high-altitude glacier cores (cf, Oeschger<br />

et al. 1978, Wagenbach et al., in press). A number<br />

of analyses are therefore planned <strong>on</strong> the xecovered<br />

cores in order to investigate- the possibilities<br />

of rec<strong>on</strong>structing the past evoluti<strong>on</strong> of<br />

high-altitude permafrost; as well as of finding<br />

paLeoenvir<strong>on</strong>mental informati<strong>on</strong> <strong>on</strong> climate,<br />

hydrological processes or rock-wall weathering.<br />

These analyses will include studies of ice crystals<br />

(size and orientati<strong>on</strong>) , impurities in the<br />

ice (dust, pollen, air bubbles) and isotopes

Fig. 1: ;ositi<strong>on</strong> of the investigated site <strong>on</strong> tbe<br />

Topog,faphischer Atlas der Schweiz ,<br />

sheet Bernina”, compiled by Coaz (18501<br />

51 ). Arrow points to rock glacier Murtsl<br />

I, the fr<strong>on</strong>t of which is already clearly<br />

defined. Note that the rock-glacier surface<br />

was not covered by remarkable extents<br />

of perennial surface ice at the<br />

time of maximum glacier extent during<br />

the Little Ice Age.<br />

( 180,3H). Attempts will also be made to date the<br />

permafrost core, using measurements <strong>on</strong> organic<br />

remains and flow models.<br />

As a geothermal phenomen<strong>on</strong>, rock glacier permafrost<br />

is closely related to climate and the<br />

energy balance at the surface. Thermal c<strong>on</strong>diti<strong>on</strong>s<br />

within rock-glacier permafrost are governed<br />

by climatic influences, as well as by geothermal<br />

and fricti<strong>on</strong>al heating. Climatic c<strong>on</strong>diti<strong>on</strong>s<br />

have changed c<strong>on</strong>siderably during the past<br />

century. It is hoped that the l<strong>on</strong>g-term m<strong>on</strong>itoring<br />

of borehole temperatures foreseen in this<br />

project will provide informati<strong>on</strong> <strong>on</strong> possible<br />

warming trends, and <strong>on</strong> what a future increase in<br />

temperature could mean for the thermal and mechanical<br />

stability of relatively warm and icerich<br />

mountain permafrost. General degradati<strong>on</strong> of<br />

high-altitude permafrost could cause numerous<br />

problems to buildings recently c<strong>on</strong>structed in<br />

ice-bearing permafrost (cf. Keusen and Haeberli<br />

1983).<br />

SITE DESCRIPTION<br />

The active rock glacier Murtsl I near Piz Corvatsch,<br />

Upper Engadin, Gris<strong>on</strong>s, was chosen as<br />

the drill site (Fig. 1). The place is easily accessible<br />

from the Corvatsch cable car. The rock<br />

glacier itself has developed within a former<br />

cirque from north-westerly-exposed scree slopes<br />

between 2850 and 2620 m.a.s.1. and shows very<br />

pr<strong>on</strong>ounced ogive-like transverse ridges (Fig.<br />

2). The steep and approximately 2Om-high fr<strong>on</strong>t<br />

is largely free of vegetati<strong>on</strong> and rests <strong>on</strong><br />

granodiorite bedrock.When first accurately mapped<br />

in 1850/51 by Coaz,, the rock glacier fr<strong>on</strong>t<br />

and the streamlet emerging from it were very<br />

close to where they are today. In additi<strong>on</strong>, the<br />

rock glacier surface was portrayed to be completely<br />

ice free. Small ice patches from avalanche<br />

c<strong>on</strong>es exist today <strong>on</strong> the scree slopes at<br />

the head of the rock glacier.<br />

A number of measprements have been carried out<br />

<strong>on</strong> the investigated rock glacier Murtgl I. Using<br />

shallow seismic refracti<strong>on</strong>, Barsch (1973) showed<br />

the active layer thickness .to be about 2 .to 4m<br />

with a tendency towards higher values near the<br />

fr<strong>on</strong>t. On the basis of snow temperature measurements,<br />

Haeberli (1973) indicated that permafrost<br />

is absent in the granodiorite rocks in fr<strong>on</strong>t of<br />

the perennially frozen rock glacier. Barsch and<br />

Hell (1976) analysed displacements of surface<br />

boulders from aerial photographs taken in 1932,<br />

1955 and 1971. They showed that surface flow is<br />

str<strong>on</strong>gly compressing towards the fr<strong>on</strong>t with average<br />

annual displacements being in the order of<br />

a few centimeters. Barsch (1977) has already<br />

carried out a shallow core drilling to 10.4111<br />

depth and he described the recovered material as<br />

mostly frozen silty sand with ice lenses. King<br />

et al. (1987) have obtained results from geoelectrical<br />

resistivity and radio-echo soundings,<br />

which agree surprisingly well with those from<br />

earlier deep seismic soundings (Barsch and Hell<br />

1976), c<strong>on</strong>firming that the bedrock beneath the<br />

rock glacier is overdeepened. From a comparis<strong>on</strong><br />

of the results from the three different sounding<br />

techniques applied, it was c<strong>on</strong>cluded that the<br />

rock glacier permafrost must be very rich in, ice<br />

and that permafrost thickness should be compara-<br />

ble to bedrock depth which was expected to be<br />

around 50m at the drill site.<br />

9 #38

DRILLING OPERATION<br />

Field work started in late April, 1987. In order<br />

to recover unc<strong>on</strong>taminated cores and to minimize<br />

thermal disturbance of the borehole, it had been<br />

decided to use a triple core-tube system in combinati<strong>on</strong><br />

with air cooling (cf. Lange 1973). An<br />

Atlas 12-bar screw compressor was therefore installed<br />

to deliver air at a rate of 13 m3/minute<br />

through a snow-buried 2-inch tube (cooling) to<br />

an air tank for removal of c<strong>on</strong>densed water and<br />

then to the heavy hydraulic L<strong>on</strong>gyear-34<br />

rotati<strong>on</strong>al core drilling machine. The core material<br />

was automatically filled into transparent<br />

plastic liners which remained insulated from the<br />

cold air circulating between the outer two tubes<br />

of the core barrel. The full plastic liners were<br />

cut to the appropriate size, closed, marked,<br />

packed into plastic bags, stored in a cooler box<br />

at -6'C and finally taken down to a deep-freeze<br />

facility (-30°C) by helicopter. During the whole<br />

drilling operati<strong>on</strong>, mean snow cover thickness <strong>on</strong><br />

the rock glacier surface slowly decreased from<br />

about Im to a few decimeters.<br />

A shallow experimental hole was first drilled to<br />

test the procequre. The boulders of the active<br />

layer were fienetrated without coring providing<br />

air in the borehole could escape and the material<br />

was highly porous and permeable. A 6rn-casing<br />

was installed (Odex-system) at the top of the<br />

borehole in order to stabilise the borehole<br />

walls at the permafrost table and within the active<br />

layer. Cores were taken from immediatly beneath<br />

the permafrost table at about 3m depth.<br />

Core diameter was 70mm and the outer diameter of<br />

the drill was 106mm. The samples came out completely<br />

dry, indicating that no melting had<br />

taken place during drilling and that the air<br />

cooling worked efficiently. The ice was quite<br />

heavily broken, however, probably as a result of<br />

stress relief. A hard-metal drilling bit was<br />

used in ice and ice-rich material. The last 10cm<br />

of each individual run were d<strong>on</strong>e without air<br />

cooling. This allowed the lower end of the core<br />

to melt slightly at the periphery, to freeze<br />

back to the core catcher (Fig. 3 ) and, hence, to<br />

hold chips of the core material within the plastic<br />

liner. A total of about 6m of ice-rich cores<br />

were taken in the experimental hole which reached<br />

a depth of 21.7m. The samples will be used<br />

for pilot analyses of the core material. A plastic<br />

tube was inserted to case the hole and.a<br />

temperature of -1.7'C was measured at the bottom<br />

of the hole after thermal stabilizati<strong>on</strong>.<br />

At the same time, the machine was moved by some<br />

2m and drilling of the deep hole was begun.<br />

Cores were taken beneath 3.6m depth, large boulders<br />

usually had to be penetrated by percussi<strong>on</strong><br />

boring, and ice-c<strong>on</strong>taining rock was cored using<br />

a diam<strong>on</strong>d crown in combinati<strong>on</strong> with a double<br />

core-barrel since rock cores tended to deform<br />

the plastic liners. No casing was used within<br />

the well ice-b<strong>on</strong>ded material. Below about 4%<br />

however, the borehole became increasingly unstable.<br />

The last piece of ice was recovered at<br />

51m within large boulders or severely-fissured<br />

rock, the transiti<strong>on</strong> between the two appearing<br />

to be gradual. Problems with unstable borehole<br />

walls c<strong>on</strong>tinued in bedrock at greater depths. An<br />

attempt to inject c<strong>on</strong>crete for stabilisati<strong>on</strong> was<br />

not successful, because the injected mass disappeared<br />

into what was obviously highly permeable<br />

rock. Borehole televisi<strong>on</strong> and caliper logging<br />

indicated that Large cavities had formed in the<br />

lower part of the hole (Figures 4 and 5). No<br />

pressurized water was encountered. At 62.5mIthe<br />

drilling was stopped within solid bedrock. A<br />

complete set of borehole logs was run in the<br />

temporarily water-filled experimental hole. However,<br />

the high permeability of the subpermafrost<br />

rocks made it impossible to fill the deep hole<br />

with water for borehole logging. Therefore, the<br />

experimental hole was deepened to 40m. Here<br />

again, unfortunately; air and water were lost at<br />

32m depth, where a c<strong>on</strong>necti<strong>on</strong> with the deep hole<br />

had developed in the meantime (air loss occurring<br />

from the experimental hole to the deep<br />

hole). 84mm diameter plastic tubes for horiz<strong>on</strong>tal<br />

and vertical deformati<strong>on</strong> measurements were<br />

now introduced into the deep borehole down to a<br />

depth of 58m, where loose material had obstructed<br />

the hole. The inclinometry tubes were firmly<br />

anchored in bedrock with c<strong>on</strong>crete; they had been<br />

put into a mantle of synthetic tissue in order<br />

to prevent loss of injected c<strong>on</strong>crete in the permeable<br />

rocks. The upper part of the hole around<br />

the inclinometry tubes was filled with water<br />

which completely froze in the course of the<br />

first night. Thermistors and magnetic rings havebeen<br />

mounted around the tubes. The experimental<br />

hole has been equipped with a string of l-comp<strong>on</strong>ent<br />

seisrnometers and precisi<strong>on</strong> thermistors down<br />

to a depth of 32m. The drilling operati<strong>on</strong> finished<br />

in early July.

FIRST RESULTS AND CONCLUSIONS<br />

Figure 5 summarises a few preliminary results.<br />

Borehole diameter after drilling is from caliper<br />

logging and gives an indicati<strong>on</strong> of relative erosi<strong>on</strong>al<br />

stability. Temperature from borehole<br />

measurements in the fall of 1987 has been roughly<br />

corrected €or thermal disturbances arising<br />

during drilling and is assumed to be within less<br />

than +0.Z0C of the undisturbed temperature.<br />

Stsatigraphy is based <strong>on</strong> a visual, generalised<br />

descripti<strong>on</strong> of the cores. Density was determined<br />

by weighing the cores and estimating the amounts<br />

of lost matesial where the samples are c<strong>on</strong>tained<br />

in plastic liners; from'.comparis<strong>on</strong> with pure ic&<br />

and rock samples, it is estimated to be correct<br />

within lo% of the given value. Ice c<strong>on</strong>tent by<br />

volume is from density. Finally, shear stress<br />

was calculated as the product of density, accelerati<strong>on</strong><br />

due to gravity, depth and the sine af<br />

the average surface slope (10') measured over a<br />

length of 250m, i.e. five times the rock glacier<br />

thickness and about half of the total rockglacie<br />

length.<br />

Five main z<strong>on</strong>es can be discerned beneath the active<br />

layer:<br />

(1) to a depth of 15m, very pure ice predomi-<br />

. nates. Average temperature is -2 to -3OC<br />

and varies seas<strong>on</strong>ally, density is close to<br />

1 Mg/m3 and ahear stresses increase with<br />

increasing depth to a maximum of about 25<br />

@a.<br />

(2) From 15 to 28m, layers of frozen and highly<br />

supersaturated silt, sand and gravel alternate<br />

with thick ice lenses. Average temperature<br />

is between -1 and -Z0C, density is 1<br />

to 1.5 Mg/m3 and shear stress reaches a<br />

maximum of about 50 kPa.<br />

3) From 28 to 32m, the same material is encountered<br />

blpt without thick ice lenses.<br />

Temperature is slightly below -loC, density<br />

increases to nearly 2 Mg/m3 and shear<br />

stress is about 60 kPa.<br />

4) Fxom 32 to 50m, coarse and saturated' frozen<br />

rock debris c<strong>on</strong>taining layers of frozen<br />

sand in places extend down to bedrock at<br />

about 50m. Temperature increases towards<br />

the melting point at the bottom, where<br />

940<br />

shear stress comes close to 150 kea due to<br />

the high density ( 2 to 2.5 Mg/m3) of the<br />

material.<br />

(5) In c<strong>on</strong>trast to what can be seen in fr<strong>on</strong>t of<br />

the rock glacier, the bedrock immediately<br />

beneath the perennially frozen sediments is<br />

highly fissured and permeable. The<br />

permafrost base appears to coincide with<br />

the uppermost part of the heavily weathered<br />

bedrock. At about 54m, moxe solid and less<br />

permeable bedrock exists.<br />

Much refinement of this informati<strong>on</strong> can be expected<br />

from more detailed measurements and"analyses.<br />

However, a few general c<strong>on</strong>clusi<strong>on</strong>s can be<br />

drawn already now. With respect to the fact that<br />

there are permafrost-free areas close to the<br />

drill site, the borehole temperature at the<br />

depth of zero annual amplitude is rather low.<br />

<strong>Permafrost</strong> thickness - as expected from geophysical<br />

soundings - is about 50m and the temperature<br />

gradient is surprisingly high. This may<br />

possibly be due to subpermafrost groundwater<br />

flow in permeable rock (cf . Echelmeyer 1987).<br />

Ice c<strong>on</strong>tent decreases systematically with depth<br />

as expected, probably leading to the anticipated<br />

change in viscosity with depth (cf. Haeberli<br />

1985). The amount of near-nurface ice is, however,<br />

extremely high. In the upper half of the<br />

rock-glacier permafrost, the av.erage ice c<strong>on</strong>tent<br />

by volume is about 80 to 90%, figures comparab-<br />

le. to what has been observed in basal layers of<br />

(ice) glaciers. It can be assumed that primary<br />

and sec<strong>on</strong>dary frost heave play an important role<br />

in the ice foqmati<strong>on</strong> within the upper rock glacier<br />

Layers and therefore largely influence the<br />

geometry of talus c<strong>on</strong>es and scree slopes in general.<br />

SelE-purificati<strong>on</strong> effects occurring at the<br />

freezing fr<strong>on</strong>t may have displaced or even eliminated<br />

part of the envir<strong>on</strong>mental informati<strong>on</strong><br />

usually c<strong>on</strong>tained in the inclusi<strong>on</strong>s and impurities<br />

of sedimentary ice. The pr<strong>on</strong>ounced layering<br />

of the rock glacier permafrost opens up the possibility<br />

of investigating the mechanical bqhav-<br />

iour of various materials; these materials obviously<br />

deform under slightly different stresses<br />

and temperatures.

core material stratigraphy density hole diameter<br />

temperature<br />

fl 100% *<br />

U<br />

I<br />

I<br />

ice<br />

.........<br />

.......<br />

.....<br />

frozen<br />

\;;;<br />

sand<br />

frozen<br />

blocks<br />

rock<br />

ice<br />

i '1!<br />

\<br />

\i I<br />

:<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

<br />

-<br />

I<br />

I<br />

100% 0%<br />

c<strong>on</strong>tent by volume<br />

I<br />

I<br />

I<br />

1<br />

....<br />

at..<br />

1<br />

L.<br />

.:<br />

1<br />

I<br />

Fig. 5: Recovered core material, core stratigraphy, density and ice c<strong>on</strong>tent by volume, borehole<br />

diameter immediately after drilling, and borehole temperature. M = z<strong>on</strong>es penetrated by<br />

hammer ("martello"), dashed lines indicate rough and highly uncertain estimates.<br />

941

ACKNOWLEDGEMENTS<br />

The drilling work was carried out by Stump Bohr<br />

AG, Ziirich, with substantial cooperati<strong>on</strong> from<br />

the Cable Car Company Surlej - Silvaplana -<br />

Corvatsch. The project is being supported by a<br />

research fund from ETH Ziirich. Bernhard Etter,<br />

Paul Gnos, Wernes Nobs, Willy Schmid, Daniel<br />

V<strong>on</strong>der Miihll and a number of other colleagues<br />

helped with the planning of the project and the<br />

field work. Pamela Alean edited the English of<br />

the manuscript. Special thanks are due to Prof.<br />

Dr. D. Vischer, director of VAW/ETH, for his<br />

c<strong>on</strong>stant encouragement and assistance.<br />

REFERENCES<br />

Barsch, D (1973). Refrakti<strong>on</strong>sseismische Bestimmung<br />

der Obergrenze des gefrorenen<br />

Schuttksrpers in verschiedenen Blockgletschern<br />

Graubiindens, Schweizer<br />

Alpen. Zeitschrift fiir Gletscherkunde<br />

und Glazialgeologie (9), 1 - 2, 143 -<br />

167.<br />

Barsch, D (1977). Ein <strong>Permafrost</strong>profil aus Graubiinden,<br />

Schweizer Alpen. Zeitschrift<br />

fiir Geomorphologie NF (211, 79 - 86.<br />

Barsch, D and Hell, G (1976). Photogrammetrische<br />

Bewecpngsmessungen am Blockgletscher<br />

Murtel I, Oberengadin, Schweizer<br />

Alpen. Zeitschrift fiir Gletscherkunde<br />

una Glazialgeologie (11 ), 2, 1 1 1 -<br />

142.<br />

Echelmeyer, K (1987). Anomalous heat flow and<br />

temperatures associated with subglacial<br />

water flow. IAHS Publicati<strong>on</strong><br />

(170), 93 - 104.<br />

Echelmeyer, K and Wang, 2 (1987). Direct observati<strong>on</strong><br />

of basal sliding and deformati<strong>on</strong><br />

of basal drift at subfreezing<br />

temperatures. Journal of Glaciology<br />

(33), 113, 83 - 98.<br />

Haeberli, W (1 973). Die Basis-Temperatur der<br />

winterlichen Schneedecke als mtiglicher<br />

Indikator fiir die Verbreitung v<strong>on</strong> <strong>Permafrost</strong><br />

in den Alpen. Zeitschrift fiir<br />

Gletscherkunde und Glazialgeologie<br />

(9), 1 - 2, 221 - 227.<br />

Haeberli, W (19 85). Creep of mountain permafrost:<br />

internal structure and flow of<br />

Alpine rock glaciers. Mitteilungen der<br />

Versuchsanstalt fiir Wasserbau , Hydrologic<br />

und Glaziologie der ETH Ziirich<br />

(77) I 142~~.<br />

Haynes, FD (1978). Strength and deformati<strong>on</strong> of<br />

frozen silt. Third <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g><br />

<strong>on</strong> <strong>Permafrost</strong>, NRC-Ottawa,<br />

(I), 656 - 661.<br />

Hooke, RL, Dahlin, i3B and Kauper, MT (1972).<br />

Creep of ice c<strong>on</strong>taining dispersed fine<br />

sand. Journal of Glaciology (1 1 ) , 63,<br />

327 - 336.<br />

Keusen, HR and Haeberli, W (1903). Site inveatigati<strong>on</strong><br />

and foundati<strong>on</strong> design asopects<br />

of cable car c<strong>on</strong>structi<strong>on</strong> in Alpine<br />

permafrost at the “Chli Matterhorn”,<br />

Wallis, Swiss Alps. Fourth <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> Permafrbst, NAP-<br />

Washingt<strong>on</strong>, Proc., 601 - 605.<br />

Xing, L, Fisch, W, Haeberli, W and Waechter, HP<br />

(1987). Comparis<strong>on</strong> of resistivity and<br />

radio-echo soundings <strong>on</strong> rock glacier<br />

permafrodt. Zeitschrift fiir Glet-<br />

scherkunde und Glazialgeologie (23),<br />

1 , 77 - 97.<br />

Lange, GR (1973). Investigati<strong>on</strong> of sampling per-.<br />

ennially frozen allpvial gravel by<br />

core drilling. <strong>Permafrost</strong> Sec<strong>on</strong>d <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, North American<br />

C<strong>on</strong>tributi<strong>on</strong>, NAS-Washingt<strong>on</strong> D.C., 535<br />

- 541.<br />

Oeschger, H, Schotterer, U, Stauf fer, B,<br />

Haeberli, W and R6thlisberger, H<br />

(1978). First results from Alpine core<br />

drilling projects. Zeitschrift fiir<br />

Gletscherkunde und GlaziaLgeologie<br />

(13), 193 - 208.<br />

Olyphant, GA (1983). Computer simulati<strong>on</strong> of<br />

rock-glacier development under viscous<br />

and pseudoplastic flow. Geological<br />

Sticiety of America Bulletin (941, 499<br />

- 505.<br />

Sayles, FB (1 968). Creep of frozen sand. USA<br />

CRREL Technical report (190), 54pp.<br />

Shumskii, PA (1964). Principles uf structural<br />

glaciology. Transl. D. Ksaus. Dover,<br />

New York, 437pp.<br />

Vitek, JD and Giardino, JR (2987). A bibliography<br />

<strong>on</strong> rock glaciers. Oklahoma State<br />

Urliversity and Texas A r4r M University,<br />

48pp.<br />

Vyalov, SS (1978). Kinetic theory of deformati<strong>on</strong><br />

of frozen1 soils .. Third <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong> , NRC-Ot tawa ,<br />

(I), 750 - 755.<br />

Wagenbach, D, Miinnich, KO, Schotterer, U and<br />

Oeschger, H (in press). The anthropogenic<br />

impact <strong>on</strong> snow chemistry at Colle<br />

Cnifetti, Swiss Alps. Annals of<br />

Glaciology.<br />

Wahrhaftig, C and Cox , A ( 1959). Rock glaciers<br />

in the Alhska Range. Geological Socie-<br />

ty of America Bulletin (70) , 383 -<br />

435,<br />

942

REMOTE SENSING LINEAMENT STUDY IN NORTHWESTERN ALASKA<br />

Hump, S.L.1 and N. Loq~nd<br />

Wniversity of Alaska, Fairbanks<br />

Wniversity of Mississippi<br />

SYNOPSIS: Landsat images have proven valuable in mapping of regi<strong>on</strong>al and local lineaments that<br />

c<strong>on</strong>trol mineral occurrences. An investigati<strong>on</strong> was c<strong>on</strong>ducted oh Landsat MSS image to explore the<br />

feasibility of using spatial filtering techniques for geological sttucture studies in the Red Dog<br />

deposit area. The Red Dog deposit, located in northwestern Alaska, is <strong>on</strong>e of the world's largest<br />

zinc deposits. The test Landsat image was processed with aevefal 3-by-3 matheniaticel filters.<br />

Examinati<strong>on</strong> of the prbcessed images revealed that a low-pass filter enhanced the subtle linear<br />

features in the area best. Major lineaments were traced <strong>on</strong> the filtered image and the result was<br />

compared with existing maps and reports. Not <strong>on</strong>ly were the mapped structures comparable to the<br />

field observati<strong>on</strong>s, but the resulting informati<strong>on</strong> also revealed two sets of major structural trends<br />

which had not been documented previously.<br />

INTRODUCTION<br />

Remote sensing techniques have been widely<br />

utilized to locate geological structures<br />

associated with major mineral occurrences.<br />

These techniques reduce the size of potential<br />

target areas, decrease explorati<strong>on</strong> costs, and<br />

furthermore, increase the mineral discoveries.<br />

The identificati<strong>on</strong> of lineaments <strong>on</strong> images has<br />

an important implicati<strong>on</strong> in ec<strong>on</strong>omic geology.<br />

Many mining districts occur al<strong>on</strong>g linear<br />

trends extending hundreds of kilometers in<br />

length. Within the mineralized z<strong>on</strong>es,<br />

individual mines are comm<strong>on</strong>ly localized by<br />

intersecting fracture systems. Landsat<br />

imagery is useful for locating both regi<strong>on</strong>al<br />

structure and local lineaments.<br />

Albert and Steele (1976) dem<strong>on</strong>strated that<br />

there was str<strong>on</strong>g correlati<strong>on</strong> between densities<br />

of linear structures and mineral occurrences,<br />

such as those found in the McCarthy<br />

quadrangle, with approximately lplB mineral<br />

occurrences. Metz (1983) c<strong>on</strong>ducted a study in<br />

the interpretati<strong>on</strong> of linear features of<br />

Landsat coverage of Alaska and ratio image<br />

analysis of major mineral occurrences to<br />

determine characteristics of the alterati<strong>on</strong><br />

z<strong>on</strong>es and local structures. Metz c<strong>on</strong>cluded<br />

that ' ratio image analysis could be an<br />

effective method of locating alterati<strong>on</strong> z<strong>on</strong>es<br />

associated with major mineral occurrences,<br />

however, no distincti<strong>on</strong> between types of ore<br />

deposits could be made.<br />

In this study, the authors applied a series of<br />

mathematical filters to a Landsat<br />

multispectral scanner (MSS) image to enhance<br />

and identify geological structures in the Red<br />

Dog deposit area. The enhancement methods<br />

used were of a simple, practical nature and<br />

allowed the authors to obtain preliminary<br />

informati<strong>on</strong> <strong>on</strong> the linear features which might<br />

be related to mineral occurrences.<br />

943<br />

REGIONAL GEOLOGY OB STUDY AREA<br />

The Red Dog mineral deposit is located in<br />

northwestern Alaska (Fig. 1) , about 960 km by<br />

air from Anchorage, Alaska. Kotzebue, the<br />

largest village near the mine, is located 144<br />

km southwest of the deposit. The topography<br />

around the mine c<strong>on</strong>sists of rol Ling hills,<br />

leading into mountains to the north and the<br />

east. The elevati<strong>on</strong> of the mine is 305 m<br />

above sea level and the area is within the<br />

c<strong>on</strong>tinuous permafrost z<strong>on</strong>e.<br />

The present mine reserve is estimatedtobe 77<br />

milli<strong>on</strong> metric t<strong>on</strong>s at a grade of 17.1% zinc,<br />

5% lead and 82 grams per t<strong>on</strong> of silver. The<br />

mine life is estimated at nearly 50 years<br />

(Giegerich, 1987). At full producti<strong>on</strong>, this<br />

mine will be the largest zinc mine and <strong>on</strong>e of<br />

the lowest cost producers in the westexn<br />

world 6<br />

The western. Brooks Range and adjacent areas<br />

are divided by Mayfield et al. (1983) into<br />

four geologic provinces: 1) the DeL<strong>on</strong>g<br />

Mountains allochth<strong>on</strong> belt; 2) the Colville<br />

basin; 3) the Schwatka Mountains province;<br />

and 4) the Yuk<strong>on</strong>-Koyukuk province. The DeL<strong>on</strong>g<br />

Mountains allochth<strong>on</strong> belt c<strong>on</strong>sists of the<br />

Endicott Mountains, DeL<strong>on</strong>g Mountains, Lisburne<br />

hills, and northern and western parts of the<br />

Baird Mountains. In this province the bedrock<br />

is coinposed of sedimentary and, to a lesser<br />

extent, igneous tocks that range in age from<br />

Ordovician to Early Cretaceous. The rocks<br />

occur in a seties of stacked thtust sheets,<br />

the smallest divisi<strong>on</strong> of a structural level.<br />

The thrust sheets that exist in the CleL<strong>on</strong>g<br />

Mountains allochth<strong>on</strong> belt c<strong>on</strong>tain parts of<br />

structurally overlapping sequences. These<br />

sequences are compbsed of sedimentary,<br />

metasedimentary and/or igneous rocks. This

18<br />

12 1:<br />

CH 1<br />

1<br />

I . i. PI<br />

I K )<br />

Y<br />

CH 3<br />

Fig. 1. Locati<strong>on</strong> Of Red Dog Mineral Deposit<br />

(Giegerich, 1987).<br />

regi<strong>on</strong> is thought to make up a large<br />

syncl<strong>on</strong>orium with strata that dip south or<br />

southwest al<strong>on</strong>g the north fr<strong>on</strong>t of the DeL<strong>on</strong>g<br />

and Endicott Mountains, and north or northwest<br />

al<strong>on</strong>g the southern boundary. While many Eolds<br />

have diverse orientati<strong>on</strong>s, most axes in the<br />

DeL<strong>on</strong>g Mountains generally para1 le1 the<br />

westerly or southwesterly physiographic trend<br />

of the mountain range and are thought to be at<br />

right angles to the principle thrust<br />

directi<strong>on</strong>.<br />

The differentiated allochth<strong>on</strong>s in the DeL<strong>on</strong>g<br />

Mountains allochth<strong>on</strong> belt include the Brooks<br />

Range allochth<strong>on</strong> and six other allochth<strong>on</strong>s.<br />

The Red Dog deposit is within the Brooks Range<br />

allocth<strong>on</strong>. The host rock c<strong>on</strong>sists of black<br />

shale, siltst<strong>on</strong>e, and schist of the Early<br />

Mississippian to Early Middle Pennsylvanian<br />

Kuna formati<strong>on</strong> (Cueck, 1983). The ore is<br />

'found as sulfide disseminati<strong>on</strong>s in the host<br />

rock; discordant quartz-rich sulfide veins and<br />

stockwork fillings; massive, fine grained,<br />

c<strong>on</strong>formable podiform bodies; and barite veins,<br />

some of which c<strong>on</strong>tain variable amount of zinc,<br />

lead, and ir<strong>on</strong> sulfides. The mineralized<br />

horiz<strong>on</strong> is overlain by rocks of the<br />

Pennsylvanian to Early Triassic Etivluk Group<br />

that c<strong>on</strong>sist mainly of unsilicified gray,<br />

green and red argillites interbedded with<br />

radiolarian cherts and thin barite layers of<br />

the Permian Siksikpuk format i<strong>on</strong>.<br />

IMAGE ANALYSIS METHODOLOGY<br />

Landsat Data<br />

"<br />

The satellite image (scene ID 1387-22090)<br />

sensed by Landsat 1 <strong>on</strong> August 14, 1973 was<br />

obtained to study the regi<strong>on</strong>al qeological<br />

structures. Multispectral scanners (MSS), the<br />

primary sensors aboard Landsats 1 to 3,<br />

provided an entire ground coverage of 185-by-<br />

185 km square per scene with a ground<br />

resoluti<strong>on</strong> of 79 m. Reflectance from the<br />

Fig. 2<br />

BRIC3HTNESS VALUE<br />

0 ) . . . . . . .<br />

0 63 i11 191 :<br />

Histograms of pixel brightness of<br />

the target image at four spectral<br />

ranges<br />

terrain was separated into four spectral<br />

channels. Band numbers 1 to 4 designated<br />

images from the MSS system and separated the<br />

reflectance in spectral ranges of 0.5 to 0.6<br />

micrometer (green) 0.6 to 0.7 micrometer<br />

(red), 0.7 to 0.8 micrometer (near IR) and 0.8<br />

to 1.1 micrometer (near IR) , respectively. A<br />

subimage of 40.5-by-40.5 km square<br />

corresp<strong>on</strong>ding to a subscene of 512-by-512 MSS<br />

pixels was used in the investigati<strong>on</strong>.<br />

C<strong>on</strong>trast Stretch<br />

Image processing of the study was performed <strong>on</strong><br />

a Comtal/3M Visi<strong>on</strong> <strong>on</strong>e/20 image processor,<br />

with a VAX 11/750 as the host computer. ELAS<br />

(Earth Resources Laboratory Applicati<strong>on</strong><br />

Software), a geobased informati<strong>on</strong> computer<br />

program package, was used in c<strong>on</strong>juncti<strong>on</strong> with<br />

the Comtal processing functi<strong>on</strong>s to extract<br />

data from Landsat image.<br />

The initial attempt was to enhance the<br />

c<strong>on</strong>trast of the original Landsat image. Fig.<br />

2 shows the spectral radiance (brightness<br />

value) distributi<strong>on</strong>s of the target image at<br />

four spectral ranges. Statistical data<br />

indicated that the mean brightness values of<br />

the study images ranged between 18 and 32. In<br />

order to produce the optimun c<strong>on</strong>trast, the<br />

original brightness values of four band images<br />

were stretched over the entire range of 256<br />

gray levels according to the normal<br />

distributi<strong>on</strong> curves. Xn the study a false<br />

color composite image of the Red Dog deposit<br />

area was generated by combining bands 1, 2,<br />

and 3 with blue, green, and red as the primary<br />

color for each corresp<strong>on</strong>ding image.<br />

944

Lineament Enhancement<br />

Landsat MSS sensors scan reflected<br />

electromagnetic waves from the terrain and<br />

record the radiance in a digital form. The<br />

complex wave of a Landsat image can be<br />

separated into its comp<strong>on</strong>ent wavelengths by a<br />

mathematical process known as spatial<br />

frequency filtering. Filters can be designed<br />

to transmit the waves depending <strong>on</strong> spatial<br />

frequency and directi<strong>on</strong>. The comm<strong>on</strong> frequency<br />

filters applicable are high-pass,<br />

intermediate-pass, and low-pass. Low-pass<br />

filters are designed to emphasize large area<br />

changes in brightness and de-emphasize the<br />

local detail <strong>on</strong> the image. High-pass filters<br />

operate just the opposite. For example, a<br />

low-pass filter may be implemented<br />

by<br />

averaging the original brightness values of<br />

pixels within the filtered area, and a highpass<br />

Eilter may be applied by subtracting a<br />

low-pass filtered image from the original<br />

image (Lil lesand and Kiefler, 1987). The<br />

directi<strong>on</strong> in which the filter is passed across<br />

the image also determines which linear<br />

features are enhanced. Lineaments normal to<br />

the filter directi<strong>on</strong> are enhanced while those<br />

parallel to the filter directi<strong>on</strong> are<br />

suppressed.<br />

The imageof Red Dog deposit areawas filtered<br />

using the Comtal's c<strong>on</strong>volver functi<strong>on</strong>s at<br />

different frequency levels. The c<strong>on</strong>voluti<strong>on</strong><br />

process, <strong>on</strong>e of the filtering techniques, has<br />

been successful in enhancing the lineaments<br />

for geological structure studies. The<br />

c<strong>on</strong>voluti<strong>on</strong> can be described as follows:<br />

+a +b<br />

O(X,Y) =c c f I (x+u,ytv)f (u,v) (1)<br />

u = -a v = -b<br />

where<br />

O(x,y): the output pixel value at (x,y)<br />

after f i 1 ter ing ;<br />

I(x+u,y+v): the input pixel values<br />

surrounding the (x,y),;<br />

f (u, v) : the filter coefficient.<br />

The sum of a1 1 the filter coefficients is<br />

generally set to equal unity to avoid shif,ts<br />

in the average value of the image radiance.<br />

Filtering is performed with v lines of the<br />

image simultaneously. The influence<br />

c<strong>on</strong>voluti<strong>on</strong> filter may have <strong>on</strong> an image<br />

depends up<strong>on</strong> the size of the filter and the<br />

values of filter coefficients (Lillesand and<br />

Kiefer, 1987). In the study, several 3-by-3<br />

c<strong>on</strong>voluti<strong>on</strong> filters were implemented to<br />

enhance linear features <strong>on</strong> the images.<br />

The Comtal's c<strong>on</strong>voluti<strong>on</strong> routine provided the<br />

authors with a real-time filtering process.<br />

The standard procedure invoking the<br />

c<strong>on</strong>voluti<strong>on</strong> routine included the following:<br />

(i) generating a color-composite image;<br />

945<br />

(ii) determining a c<strong>on</strong>volver input image from<br />

the color image;<br />

(iii)activating the c<strong>on</strong>volver filter with a<br />

3-by-3 matrix as shown:<br />

a b a<br />

b c b<br />

a b a<br />

(iv) specifying the filter coefficients<br />

interactively by depressing a. special<br />

functi<strong>on</strong> key and rolling the trackball<br />

device to relocate the target positi<strong>on</strong>s.<br />

Initially, the coefficients a,b, and c were<br />

set as 0, 0, and 1, and the target was moved<br />

to screen center (255, 255). While the<br />

interactivity was enabled, new values of a, b<br />

and c were generated, based <strong>on</strong> the following<br />

algorithms:<br />

where<br />

a - 1 - 255<br />

"<br />

b 255<br />

x, y: the target coordinates ( 0 x, y 5511).<br />

The Comtal's low-pass filter was implemented<br />

as the target was moved into the lower righ<br />

corner of the image. The low-pass c<strong>on</strong>voluti<strong>on</strong><br />

produced relatively c<strong>on</strong>stant filter<br />

coefficients. As the target was moved into<br />

the upper left corner, a high-pass filter with<br />

large variati<strong>on</strong> in coefficients was generated.<br />

In the study, four types of c<strong>on</strong>voluti<strong>on</strong><br />

filters were used to enhance linear features<br />

<strong>on</strong> images of bands 2 and 3. The analysis<br />

involved processing images through a set of<br />

filters at various frequency levels. The<br />

filter, which emphasized linar features best<br />

at each frequency level, was chosen<br />

interactively while'vi'ewiny the texture<br />

changes of the image. In general, the<br />

filtered band 2 image revealed geological<br />

structures in greater detail and the processed<br />

band 3 image enhanced the stream patterns and<br />

terrain features of the area.<br />

The high-pass filter [1.43, -1.67, 1.43, -<br />

1.67, 1.94, -1.67, 1-43, -1.,67, 1.431 was able<br />

to reveal the fine detail of terrain texture,<br />

although it suppressed the c<strong>on</strong>trast between<br />

the main streams and the tributaries. The<br />

low-pass filter 10.10, 0.12, 0.10, 0.12, 0.14,<br />

0.12, 0.10, 0.12, 0,101 was also activated to<br />

observe the effect <strong>on</strong> the image. The result<br />

of this low-pass filtering did not indicate<br />

any significant improvement. Am<strong>on</strong>g the<br />

filters tested, an intermediate-frequency<br />

filter 1-0.01, 0.04, -0.01, 0.04, 0.88, 0.04,<br />

-0.01, 0.04, -0.011 was found to best show<br />

the linear features. An example of the<br />

filtered image is shown in Fig. 3. The<br />

filtered image, as compared with the color<br />

composite image, shows a better linear trends<br />

and less subtle brightness variati<strong>on</strong>s.

Ratio images were also prepared by dividing<br />

the pixel brightness value in <strong>on</strong>e band by the<br />

corresp<strong>on</strong>ding pixel brightness value in<br />

another band and the divisi<strong>on</strong>s were multiplied<br />

by a factor based <strong>on</strong> a look-up table. The<br />

c<strong>on</strong>trast of ratio images was then enhanced by<br />

normal c<strong>on</strong>trast enhancement techniques. The<br />

rati<strong>on</strong>ale for using the ratioing process was<br />

to remove the shadowing effect <strong>on</strong> terrain<br />

features. The process provided the authors<br />

with a better understanding of the<br />

distributian of linear topographic features,<br />

such as drainage patterns in the area. In the<br />

study, the ratio image of band 4 to band 1 was<br />

used to illustrate this advantage. The ratio<br />

image, as shown in Fig. 4, enhances the stream<br />

pattern and topographic highs.<br />

RESULTS AND ANALYSIS<br />

According to the palinspasJic model proposed<br />

by Mayfield et al. (1983)' the thrust sheets<br />

moved northward and collided with the Arctic<br />

Alaska plate, which has moved southward, out<br />

of the Beaufort Sea, in a counterclockwise<br />

moti<strong>on</strong> relative to the North American crat<strong>on</strong>.<br />

The Brooks Range was created in the Early<br />

Cretaceous period during an orogeny that<br />

produced numerous thrust faults with as much<br />

as tens of k'ihyeters of displacement.<br />

From the filtered image shown in Fig. 3 and a<br />

comparis<strong>on</strong> with the ratio image (Fig. 41, two<br />

major 1-iriear trends were seen <strong>on</strong> the satellite<br />

image. Fig. 5A summerizes the major<br />

lineaments/thrust faults identified <strong>on</strong> the<br />

processed Landsat image. The major thrust<br />

faults mapped by Mayfield et al. (1983) are<br />

also reproduced and shown in Fig. 5R.<br />

The east-west trend c<strong>on</strong>sists of linear<br />

features labelled as E, G and I <strong>on</strong> Fig. 5A and<br />

the north-south faults are composed of<br />

lineaments of A, B, C and D. The remainder of<br />

the thrust faults documented by Mayfield et<br />

al. (1983) are not identifiable from the<br />

satellite image. These traced lineaments, in<br />

general, coincide with the stream courses<br />

which tend to follow the weak z<strong>on</strong>es. A less<br />

exposed lineament, A, is found <strong>on</strong> the right<br />

edge of the figure. This Lineament, when<br />

overlapped over a topographic map, shows that<br />

it follows <strong>on</strong>e of the tributaries o€ Wrench<br />

Creek. Al<strong>on</strong>g the lineament are ridges which<br />

parallel this linear feature until it<br />

intersects a thrust fault. This lineament<br />

appears to c<strong>on</strong>tinue southward but shifts<br />

towards the east.<br />

The north-south lineaments (B and D) also<br />

follow stream courses and c<strong>on</strong>nect to known<br />

mapped, thrust faults. The other major northsouth<br />

lineament (C) starts at the juncti<strong>on</strong> of<br />

an east-west lineament and follows a known<br />

thrust fault until it reaches a tributary of<br />

the WuJ ik River.<br />

The east-west lineaments were detected and<br />

they too follow stream courses. The lineament<br />

(E) at the bottom of the map (Fig. 5A) has<br />

been mapped as a thrust fault by Mayfield's<br />

team, but the other lineaments (F, E, and a<br />

branch of H) were not documented. The sec<strong>on</strong>d<br />

east-west lineament (G) follows a stream ,<br />

course <strong>on</strong> the right edge of the map and<br />

c<strong>on</strong>tinues westward, parallel to a set of<br />

ridges. The third 'east-west lineament (I)<br />

hegins as a mapped thrust fault, but c<strong>on</strong>tinues<br />

westward, following stream courses and saddles<br />

946

I<br />

m<br />

B<br />

i<br />

II<br />

r<br />

Fig. 5 (A) Major lineaments identified <strong>on</strong> Landsat image of Red Dog deposit area.<br />

(B) Regi<strong>on</strong>al geological structures mapeed by Mayfield et. al. in 1983.<br />

until it reaches the Wulik River. This<br />

lineament branches out and <strong>on</strong>e of the branches<br />

follows a mapped north-west thrust fault. The<br />

other follows a stream course which intersects<br />

with the Wulik River and is c<strong>on</strong>cealed by the<br />

alluvial. deposit of the Wulik River.<br />

CONCLUSIONS<br />

In summary, c<strong>on</strong>clusi<strong>on</strong>s drawn from this study<br />

are:<br />

(i) The Low-pass filter is most valuable<br />

in the enhancement of linear<br />

geological features in the Red Dog<br />

deposit area, Alaska;<br />

(ii) The filtered band 2 (near IR) image<br />

reveals structural lineaments in<br />

greater detail while band 3 image<br />

enhances stream pattern; and<br />

(iii) Most of the lineaments identified<br />

<strong>on</strong> the image follow stream courses<br />

and appear to coincide with a<br />

number of the mapped major thrust<br />

faults in the regi<strong>on</strong>.<br />

ACKNOWLEDGEMENTS<br />

The authors wish to express their gratitude to<br />

MKS. Alice Baergen for her assistance in<br />

typing this manuscript and to Mrs. Cathy<br />

Farmer for her review of the article.<br />

REFERENCES<br />

Albert, N.R.D. & Steele, W.C. (1976).<br />

Interpretati<strong>on</strong> of Landsat imagery of the<br />

McCarthy quadrangle, Alaska, U.S.<br />

Geological Survey Misc. Field Studies Map<br />

MF-773NI Scale 1:250,000, 3 sheets.<br />

ELAS (1984). Earth Resource Laboratory<br />

Applicati<strong>on</strong>s Software - ELAS user's<br />

guide, NASA, Nati<strong>on</strong>al Space Technology<br />

Laboratories, Earth Resources Laboratory.<br />

Giegerich, H.M. (1987). Progress report <strong>on</strong><br />

Cominco's Red Dog Project in Alaska,<br />

sec<strong>on</strong>d largest zinc deposit ever<br />

discovered: Mining Engineering.<br />

947

tillesand, T.M. & Kiefer, R.W. (1987). Remote<br />

sensing and image interpretati<strong>on</strong>, 721p,<br />

John Wiley and S<strong>on</strong>s, 2nd Editi<strong>on</strong>, New<br />

York<br />

Lueck, L. (1983). Petrologic and geochemical<br />

characterizati<strong>on</strong> of the Red Dog and other<br />

base-metal sulfide and barite deposits in<br />

the DeL<strong>on</strong>g Mountaina, Western Brooks<br />

Range, Alaska, in Master thesis,<br />

University of Alaska.<br />

Mayfield, C.F., Tailleur, I.L., h Ellesiek, I.<br />

(1983). Stratigraphy, structure, and<br />

palinspastic synthesis of the western<br />

Brooks Range, northwestern Alaska. U.S.<br />

Geological Survey, Open-File Report OF<br />

83-779.<br />

Metz, P.A. (1983). Landsat linear features<br />

and mineral occurrences In Alaska. MIRL<br />

Report No. 66, University of Alaska-<br />

Fairbanks, Alaska.<br />

,948

THERMAL EVIDENCE FOR AN ACTIVE LAYER ON THE SEABOTTOM<br />

OF THE CANADIAN BEAUFORT SEA SHELF<br />

J.A. Hunter, H.A. MacAulay, S.E. Pullan. R.M. GagnC, R.A. Burns and BL. Good<br />

Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada, K1A O M<br />

SYNOPSIS Thick permafrost occurs widely beneath the Canadian Beaufort Sea c<strong>on</strong>tinental shelf.<br />

Over much of the seafloor, the water temperatures are below OOC. However, in nearshore regi<strong>on</strong>s,<br />

out to 25 km offshore, seas<strong>on</strong>al changes in water temperatures occur due to variati<strong>on</strong>s in the<br />

Mackenzie River outflow. During summer m<strong>on</strong>ths, warm river water (above O°C) flows <strong>on</strong> to' the<br />

shelf and is in c<strong>on</strong>tact with the bottom to water depths of up to 20 m. During winter m<strong>on</strong>ths, the<br />

flow is reduced and the effects of the upwelling of Arctic seawater (below O°C> <strong>on</strong> the shelf can<br />

be observed in water depths as shallow as 2 m. An active layer at the seabottom is produced by<br />

these seas<strong>on</strong>al changes and the thermal effects reach bey<strong>on</strong>d 10 m sub-bottom.<br />

Between 1977 and 1986, six regi<strong>on</strong>al temperature profiles were compiled from the readings of<br />

thermistor cables installed in 80 drill-holes <strong>on</strong> the Beaufort shelf. These data, whioh were<br />

obtained at the end of the winter period, showed the previous summer's warming effect to be at a<br />

depth of 7 to 10 m below bottom, with the thermal anomalies attenuating seaward. At <strong>on</strong>e<br />

additi<strong>on</strong>al shoreline site, both summer and winter sub-seabottom temperature profiles show large<br />

Seas<strong>on</strong>ally reversing thermal gradients of up to 2OC per metre within the first kilometre<br />

offshore. The Dresence of an active laver should be a c<strong>on</strong>siderati<strong>on</strong> in seabottom engineering<br />

design in a permafrost regime.<br />

INTRODUCTION<br />

The Canadian Beaufort Sea c<strong>on</strong>tinental shelf<br />

has recently become an area of intense oil<br />

explorati<strong>on</strong> activity. Sufficient oil reserves<br />

have been established to warrant c<strong>on</strong>siderati<strong>on</strong><br />

of plans for future development from offshore<br />

wells. Designs for well completi<strong>on</strong>s and<br />

pipelines are not without technical<br />

difficulties due to the presence of icebearing<br />

permafrost at shallow depths.<br />

The Beaufort Sea shelf is relatively shallow,<br />

extending 120km offshore to a shelf break<br />

between 90 and 110 m water depth. Since the<br />

shelf was thought not to have been glaciated<br />

during the late stage Pleistocene ice advance,<br />

Mackay (1972) suggested that extensive<br />

permafrost could have accreted beneath the<br />

seafloor which, because of sea-level lowerin<br />

was exposed as dry land. Hunter et al. ( 197f:<br />

1978) provided geophysical evidence that<br />

indicated the widespread occurrence of icebearing<br />

permafrost under the Canadian Beaufort<br />

Sea shelf, and this has been subsequently<br />

c<strong>on</strong>firmed by industry drilling (O'C<strong>on</strong>nor,<br />

1984). Taylor and Allen ( 1987) have shown,<br />

from seabottom temperature measurements<br />

deaward of the 25 m isobath, that permafrost<br />

c<strong>on</strong>diti<strong>on</strong>s presently occur at the seabed over<br />

almost the entire outer shelf z<strong>on</strong>e, where the<br />

measured seabottom temperatures range from<br />

-0.41 to -1.92'C.<br />

The heat transport of the Mackenzie River has<br />

a str<strong>on</strong>g influence <strong>on</strong> the inshore water<br />

temperatures <strong>on</strong> the Canadian Beaufort shelf<br />

(Fig. I ), and this in turn affects the<br />

949<br />

distributi<strong>on</strong> of offshore permafrost (Mackay<br />

and Mackay, 1974). The Mackenzie factor makes<br />

the c<strong>on</strong>figurati<strong>on</strong> and thermal history of subseabottom<br />

permafrost in this regi<strong>on</strong> very<br />

different from that of offshore permafrost<br />

beneath the Alaskan Beaufort Sea shelf (e.g.<br />

Swift et al., 1983). This present study<br />

focusses <strong>on</strong> the influence of the Mackenzie<br />

River discharge as it affects the nearshore<br />

sub-seabottom permafrost c<strong>on</strong>figurati<strong>on</strong> out to<br />

water depths of 20 m. Studies of this nature<br />

may be a necessary c<strong>on</strong>siderati<strong>on</strong> in designing<br />

nearshore pipeline approaches and shoreline<br />

crossings.<br />

The Mackenzie River discharge has a str<strong>on</strong>gly<br />

seas<strong>on</strong>al character. Figure 2 is a generalized<br />

flow-rate curve based <strong>on</strong> an average of four<br />

years (1980-1983) observati<strong>on</strong>s at Arctic Red<br />

River, which is at the apex of the Mackenzie<br />

Delta (e.g. Envir<strong>on</strong>ment Canada, 1982).<br />

Characteristically, an abrupt increase in<br />

discharge rate occurs in late May or early<br />

June, when flow rates can reach ten times that<br />

of the winter low. The rate drops off rapidly<br />

to about half its maximum during June, and<br />

then decreases uniformly throughout the<br />

summer. By the end of November the Mackenzie<br />

discharge is back to its low winter value.<br />

Although no discharge records are available at<br />

the mouths of any of the delta channels, it is<br />

suggested that the discharge at the seacoast<br />

follows the general trend of the curve shown<br />

in Figure 2 , with perhaps a time delay of' some<br />

days.<br />

Between 1977 and 1986, a series of end-ofwinter<br />

temperature measurements of both

Fig. 1<br />

- Generalized bathymetry of the southern Canadian Beaufort Sea and locati<strong>on</strong> of<br />

temperature lines.<br />

seawater and the sub-seabottom sediments were<br />

made during the m<strong>on</strong>th of April. These<br />

measurements were made al<strong>on</strong>g six regi<strong>on</strong>al<br />

nearshore to offshore lines in water depths of<br />

up to 12 m. Additi<strong>on</strong>ally, seawater column<br />

temperature measurements were made al<strong>on</strong>g these<br />

same regi<strong>on</strong>al lines in early September 1986.<br />

Although the September measurements were not<br />

taken at peak discharge (see Fig. 21, these<br />

data probably represent the average summertime<br />

water temperature secti<strong>on</strong>s, and provide a<br />

guide as to the range of seabottom<br />

temperatures and the temperature structure of<br />

the freshwater layer of the inshore area which<br />

prevails in the summertime m<strong>on</strong>ths.<br />

SUB-SEABOTTOM TEMPERATURE MEASUREMENTS<br />

The locati<strong>on</strong>s of the temperature lines are<br />

shown in Figure 1. Each line c<strong>on</strong>sisted of at<br />

least ten thermistor cable installati<strong>on</strong>s to<br />

depths as much as 40 rn below seabottom. Most<br />

Of the holes drilled for temperature<br />

measurements used an hydraulic Jet drilling<br />

technique (Judge et al. 19761, and thermistor<br />

cables were installed in 2.5 cm diameter steel<br />

casing. Cables c<strong>on</strong>sisted of 12 to 24<br />

thermistors with spacings ranging between 0.75<br />

m and 5 m, resulting in relatively detailed<br />

temperature profiles of the immediate subbottom.<br />

Since hydraulic jet drilling<br />

introduces a thermal disturbance into the<br />

seabottom, the temperature cables were<br />

m<strong>on</strong>itored c<strong>on</strong>tinually after installati<strong>on</strong> to<br />

obtain equilibrium temperature c<strong>on</strong>diti<strong>on</strong>s.<br />

Depending up<strong>on</strong> the amount of thermal<br />

disturbance, andthe nature of the seafloor<br />

materials, return to equilibrium (to within<br />

Q.IoC, the accuracy of the thermistors) 'was<br />

achieved in time periods between three days<br />

and several weeks.<br />

The seafloor materials encountered during<br />

drilling c<strong>on</strong>sisted of sand, silt and clays of<br />

recent and Pleistocene age (O'C<strong>on</strong>nor, 1983).<br />

Drilling c<strong>on</strong>diti<strong>on</strong>s varied with the type of<br />

material, with poorest penetrati<strong>on</strong> and hole<br />

collapse in loose sand and best drilling in<br />

clays, silt and ice-bearing sands.<br />

Wherever possible, temperature profiles of the<br />

Fig. 2 - A generalized annual discharge curve seawater column were measured; either through<br />

for the Mackenzie River showing the locati<strong>on</strong> the casing or from separate measurements with<br />

in time of' winter and summer temperature thermistor cables deployed beneath the seameasurements<br />

in the Beaufort Sea.<br />

ice.<br />

950

Fig. 3<br />

- Sub-seabottom thermal secti<strong>on</strong> for the Pullen line end-of-winter measurements.<br />

Figure 3 shows a representative secti<strong>on</strong> of<br />

sub-bottom temperatures measured during April<br />

for a line near Pullen Island (see Fig. 1 for<br />

locati<strong>on</strong>). The isotherms are c<strong>on</strong>toured in<br />

0.5OC intervals with a thermistor calibrati<strong>on</strong><br />

accuracy of 0.1OC.<br />

In the shoreline area, Large vertical and<br />

horiz<strong>on</strong>tal temperature gradients exist. This<br />

area is str<strong>on</strong>gly under the influence of<br />

Mackenzie River water since this water is<br />

resident <strong>on</strong> the bottom for the l<strong>on</strong>gest period<br />

during the summer m<strong>on</strong>ths. The net effect is<br />

shown by the warm bulb enclosed by the 4I0C<br />

isotherm. Landward, the horiz<strong>on</strong>tal gradient<br />

at depth indicates the influence of the<br />

relatively cold (-8OC) permafrost <strong>on</strong> shore.<br />

The vertical gradient near the seafloor<br />

suggests that cold seawater invades the<br />

nearshore regi<strong>on</strong> in winter-time, mixing with<br />

the reduced flow of Mackenzie River water and<br />

giving rise topockets of cold water (even<br />

below OOC) in some areas.<br />

In water depths between 4 and 8 m, isotherms<br />

immediately below seabottom are pulled back<br />

shoreward, showing the effect of cold water<br />

invasi<strong>on</strong> <strong>on</strong> the seafloor during winter m<strong>on</strong>ths.<br />

The previous summer's warming effect from<br />

Mackenzie River water is shown as temperature<br />

maxima between 7 and 10 m below bottom. These<br />

maxima probably also reflect a cumulative<br />

effect of many winter-summer temperature<br />

cycles, as well as other less well-known<br />

factors such as l<strong>on</strong>g-term warming effects or<br />

degradati<strong>on</strong> of permafrost at depth, and the<br />

rate of coastal erosi<strong>on</strong> and sea-level rise<br />

since the last glaciati<strong>on</strong>.<br />

The sub-bottom temperature maxima attenuate<br />

with water-depth and distance offshore.<br />

Hence, the sub-bottom temperatures at 12 m<br />

water depth are almost isothermal.<br />

The nature of the sub-bottom temperature<br />

maxima can be seen in Figure 4, which is a<br />

compilati<strong>on</strong> of data from all installati<strong>on</strong>s <strong>on</strong><br />

all lines from April observati<strong>on</strong>s. In this<br />

figure, the maximum observed sub-seabottom<br />

temperature is plotted with respect to the<br />

water depth at the installati<strong>on</strong> locati<strong>on</strong>.<br />

Although these data come from widely separated<br />

areas of the Beaufort nearshore shelf, a<br />

definite trend can be seen. In water depths<br />

less than 6.5 m, positive sub-seabottom<br />

temperature maxima are obaerved, usually<br />

occurring between 6 and 10 m below seabottom.<br />

At these water depths, Mackenzie River water<br />

is resident for the l<strong>on</strong>gest time during summer<br />

m<strong>on</strong>ths. At water depths bey<strong>on</strong>d 6.5 m, the<br />

temperature maxima are below QOC, indicating a<br />

lesser effect of warm Mackenzie River water.<br />

Extrapolating the trend line to -1.8OC, cold<br />

seawater would be the limiting c<strong>on</strong>diti<strong>on</strong> where<br />

no thermal maximum would be observed , (i .e. no<br />

mixed Mackenzie River water reaches the<br />

seabed).<br />

It is unfortunate that no similar aubseabottom<br />

temperature data are available for<br />

these water depths for the end-of-summer<br />

't<br />

SUB-BOTTOM<br />

TEMPERATURE PC)<br />

-8 -1 0 1 P S<br />

1 " ' l " " " '<br />

I ..': .<br />

Fig. 4 - A compilati<strong>on</strong> of maximum observed subseabottom<br />

temperatures vs. water depth for<br />

all temperature holes drilled during the<br />

end-of-winter period in the Beaufort Sea,<br />

95 1

ITYOK<br />

Fig, 5 - A comparis<strong>on</strong> of seawater temperature distributi<strong>on</strong> from <strong>on</strong>shore to offshore for<br />

end-of-summer (upper secti<strong>on</strong>) and end-of-winter (lower secti<strong>on</strong>) measurements.<br />

period. It is suggested that temperature<br />

minima would probably exist beneath the<br />

seabottom instead of the temperature maxima<br />

observed at the end of winter. Some<br />

indicati<strong>on</strong>s of such a seas<strong>on</strong>al effect have<br />

been observed within a couple of metres of the<br />

SEAWATER TEMPERATURE HEASURGMENTS<br />

Measurements of seawater column temperatures<br />

have been made for both April and September<br />

time periods. A comparis<strong>on</strong> of summer and<br />

winter water temperatures is shown in Figure 5<br />

for the Ityok line, The upper secti<strong>on</strong> in this<br />

figure shows the affect of Mackenzie River<br />

water in September. This warm water, at<br />

temperatures between +5OC and +7.5aC, forms an<br />

upper layer approximately 8 m thick. The<br />

river water cools to seaward with a gradient<br />

of approximately lac per 7.5 km. Between<br />

water depths of 8 and 15 m str<strong>on</strong>g vertical<br />

temperature gradients exist, probably<br />

indicating mixing with cold seawater. From<br />

this figure, it is apparent that the<br />

seabottom, at water depths less than 8 m, is<br />

under the full thermal effect of the Mackenzie<br />

River discharge, whereas at water depths<br />

between 8 and 20 m, it experiences lower<br />

temperatures. It is suggested that this<br />

example may be close to the average<br />

temperature distributi<strong>on</strong> al<strong>on</strong>g the Mackenzie<br />

Delta fr<strong>on</strong>t for the summer period; similar<br />

observati<strong>on</strong>s and c<strong>on</strong>clusi<strong>on</strong>s have also been<br />

made by Burgess and Judge (1977). During peak<br />

flooding in June the warm fresh-water layer<br />

may inereaae substantially, but in turn this<br />

layer is probably much thinner during October<br />

and November.<br />

952<br />

Figure 6 is a compilati<strong>on</strong> of water temperature<br />

measurements made at the seabottom al<strong>on</strong>g all<br />

survey lines for both winter time (April) and<br />

summer time (September) c<strong>on</strong>diti<strong>on</strong>s for water<br />

depths between 2 m and 24 m. The September<br />

suite of data clearly shows the thick warm<br />

fresh-water layer. Although the temperatures<br />

for April are almost entirely below O°C, a<br />

similar trend .can be seen with mixed<br />

Mackenzie River water extending, as a surface<br />

layer, out to 5 m Water depth. While the<br />

September measurements indicate mixed water at<br />

-2 0 2 4 I<br />

SEAEOTTOM TEMPERATURE (‘C)<br />

SEPTEMBER<br />

Fig. 6 - A compilati<strong>on</strong> from all survey lines of<br />

water temperature measurements made at the<br />

seabottom vs. water depth for end-of-winter<br />

(April) and end-of-summer (September).

the seabottom to. water depths of at least<br />

20 m, the April measurements show that<br />

essentially unmixed cold sea water at -1.6 to<br />

-1.8OC exists at the seabottom in water depths<br />

bey<strong>on</strong>d 8 m. This figure illustrates that a<br />

large extent of the nearshore z<strong>on</strong>e is<br />

characterized by a layer immediately beneath<br />

the seabed experiencing an annual cycle<br />

of<br />

temperatures above and below O°C - an active<br />

layer.<br />

SHORELINE STUDIES: NORTH HEAD, RICHARDS ISLAND<br />

In an attempt to understand the seas<strong>on</strong>al<br />

variati<strong>on</strong> of permafrost temperatures in the<br />

shoreline z<strong>on</strong>e, a survey was carried out at<br />

North Head, Richards Island (see Fig, 1) in an<br />

area where pipelines may be brought ashore in<br />

future oil and gas development.<br />

During the summer of 1985, a series of 10<br />

boreholes were drilled al<strong>on</strong>g a line from the<br />

shore to 000 m offshore. Thermistor cables<br />

were installed and equilibrium temperatures<br />

for early September were measured. The site<br />

was reoccupied in April of 1986 when 11 holes<br />

were d,rilled al<strong>on</strong>g the same line and<br />

thermistor cables were re-installed to obtain<br />

late winter equilibrium sub-bottom temperatures.<br />

The temperature results are shown as thermal<br />

secti<strong>on</strong>s in Figure 7.<br />

The summertime temperature c<strong>on</strong>figurati<strong>on</strong> shown<br />

in Figure 7(a) indicates a thin thaw z<strong>on</strong>e<br />

above O°C al<strong>on</strong>g the entire secti<strong>on</strong> out to<br />

800 m offshore. In the inshore area, at water<br />

depths less than 1 m, the thaw z<strong>on</strong>e is less<br />

than 0.5 m thick. In deeper water areas<br />

(r2 m), the thaw z<strong>on</strong>e increases to 8 m<br />

thickness. At the shoreline, across the beach<br />

or intertidal z<strong>on</strong>e, the thaw z<strong>on</strong>e is<br />

approximately 1 m thick. Between 30 m and<br />

350 m offshore, a large temperature gradient,<br />

exceeding 1°C/m, occurs in the first 6 m below<br />

bottom. The coldest permafrost ( < -7OC)<br />

occurs at a depth of 8 m below seabottom in<br />

this area while the permafrost at the<br />

same depth at the shoreline is relatively warm<br />

(-3OC to -4OC).<br />

The c<strong>on</strong>figurati<strong>on</strong> of the summertime permafrost<br />

temperature regime can be explained by<br />

examining the temperature regime in late<br />

winter shown in Figure 7(b). In wintertime,<br />

1.5 to 2 m of sea-ice is formed, and at<br />

freeze-up the ice freezes to the bottom in the<br />

shallowest water areas first. Th8refOre the<br />

nearshore seabottom z<strong>on</strong>e experiences cold<br />

temperatures in wintertime for a much L<strong>on</strong>ger<br />

period than the offshore z<strong>on</strong>e. In the<br />

offshore z<strong>on</strong>e, the warm Mackenzie River water<br />

(above O°C) is slowly replaced with mixed<br />

fresh and salt water at temperatures slightly<br />

below O°C. Hence, as Figure 7(b) shows, the<br />

winter subseafloor temperature gradient in the<br />

nearshore z<strong>on</strong>e is as large as the summer<br />

gradient ( t 1°/m), but the gradient has<br />

reversed directi<strong>on</strong>. At distances bey<strong>on</strong>d 200 m<br />

offshore the residual summer heating pulse<br />

from the warm Mackenzie River water is found<br />

at a depth of 10 m below bottom and is<br />

indicated by the shoreward bending back of the<br />

isotherms. A residual pocket, above, O°C, is<br />

indicated at the offshore end of this line.<br />

From previous work, this z<strong>on</strong>e<br />

is known to<br />

extend seaward, as shown in Figure 3.<br />

, "i 32<br />

:.6:,<br />

A<br />

y,:<br />

, , ,/<br />

, , , ,:, , , , , , , ,<br />

P '<br />

I , ,<br />

lp' \ , , , , ,'\,,\,\ j ,,,, I ,,,, , , , , ,,,,(,,,,,,,,,<br />

100 200 aoo 400 600 eo0 roo<br />

b)<br />

lhorallns APRIL 1908<br />

1 1 1 1 1 1 ~ 1 1 , 1 1 1 1 , 1 . . 1 , 1 , , , , 1 , , , , 1 1 , , . 1 1 , , . l . , r , l , , , l l , , l l l , . . , I . I I , I . I I , ~ . ~ , , ~ , , , . ~ . . ,<br />

0 100 200 500 400 500 800 700<br />

DISTANCE FROM SHORELINE (m)<br />

Fig. 7<br />

- Thermal secti<strong>on</strong>s at the North Head nearshore test site; (a) end-of-summer and<br />

(b) end-.of -winter.<br />

953

In Figure 7 it can be seen that the shoreline<br />

permafrost temperatures at depths below 8 m<br />

are warmer than those occurring in the<br />

nearshore. The shoreline beach and cliff<br />

areas characteristically are covered by thick<br />

drifts of snow (' 2 m in places) which act as<br />

a thermal blanket. This effect is clearly<br />

seen in the horiz<strong>on</strong>tal gradients at shallow<br />

depths which occur across the shoreline area.<br />

Terrain geological studies in these, areas have<br />

indicated that this particular test site has a<br />

relatively stable coastline; that is, no<br />

measurable coastal erosi<strong>on</strong> has taken place in<br />

the last 30 years (Dallimore et al., 1988).<br />

Hence, the thermal effects shown in the<br />

nearshore sub-seabottom are probably not<br />

indicative of relict permafrost. The major<br />

factor appears to be the relatively broad<br />

inshore z<strong>on</strong>e of shallow water that freezes to<br />

the bottom early in the winter seas<strong>on</strong>. This<br />

area has the thinnest thaw layer in summer and<br />

the largest vertical thermal gradi-ents. It is<br />

interesting to speculate <strong>on</strong> the origin of this<br />

z<strong>on</strong>e - do frost heave and ice-lense formati<strong>on</strong><br />

c<strong>on</strong>tribute substantially to the development of<br />

the shallow water z<strong>on</strong>e Such a questi<strong>on</strong> can<br />

be answered <strong>on</strong>ly by further detailed studies<br />

of ice c<strong>on</strong>tent and soil type in the first 8 m<br />

below seabottom.<br />

'It is thought that similar winter and summer<br />

c<strong>on</strong>diti<strong>on</strong>s prevail in many areas of the<br />

Beaufort sea coast where stable shorelines<br />

exist. Hence, pipeline landfall designs which<br />

interact with, or may. cause to change,<br />

*existing permafrost c<strong>on</strong>dlti<strong>on</strong>s, must c<strong>on</strong>sider<br />

horiz<strong>on</strong>tal temperature gradients exceeding 15O<br />

per kilometre and seas<strong>on</strong>ally reversing<br />

vertical seabottom gradients exceeding I0C/m.<br />

SWARY<br />

The seafloor of the nearshore Canadian<br />

Beaufort Sea is subjected to annual<br />

temperature cycles above and below O°C as a<br />

result of the fluctuating warm freshwater<br />

levels of the Mackenzie River. The resulting<br />

temperature distributi<strong>on</strong> in the sub-bottom<br />

indicates an "active layer" above permafrost<br />

which extends out to the 20 m isobath. This<br />

active layer effect is most pr<strong>on</strong>ounced in<br />

shallow water areas and attenuates seaward.<br />

At the coastline, where seawater freezes to<br />

bottom in winter, large temperature gradients<br />

are developed in the immediate seabottom.<br />

During summer m<strong>on</strong>ths the gradients are<br />

reversed. Both summer and winter gradients<br />

may be in excess of l0C per metre.<br />

C<strong>on</strong>structi<strong>on</strong> engineering of bottom-founded<br />

structures and pipelines should c<strong>on</strong>sider the<br />

widespread occurrence of the sub-seabottom<br />

active z<strong>on</strong>e.<br />

REFERENCES<br />

Burgess, M. and Judge, A.S. (1977). Thermal<br />

observati<strong>on</strong>s c<strong>on</strong>ducted as part of Beaufort<br />

Delta Oil Project Limited's sampling<br />

cruise <strong>on</strong> the M.S. Norwerta, Beaufort Sea,<br />

1976. Geothermal Service of Canada, Earth<br />

Physics Branch, Internal Report 77-1.<br />

Dallimore, S.R., Kurfurst, P.J. and Hunter,<br />

J.A.M. (1988). Geotechnical and geothermal<br />

c<strong>on</strong>diti<strong>on</strong>s of nearshore sediments,<br />

Southern Beaufort Sea, Northwest<br />

Territories, Canada. % Proceedings, Fifth<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>,<br />

Aug. 2-5, 1988, Tr<strong>on</strong>dheirn, Norway.<br />

Envir<strong>on</strong>ment Canada. (1982). Sediment data,<br />

Canadian rivers 1980. Inland Water<br />

Directorate, Water Survey of Canada, 167-<br />

168.<br />

Hunter, J.A., Judge, A.S., MacAulay, H.A.,<br />

Good, R.L., Gagnk, R.M. and Burns, R.A.<br />

(1976). <strong>Permafrost</strong> and frozen sub-bottom<br />

materials in the Southern Beaufort Sea.<br />

Beaufort Sea Project, Technical Report No.<br />

22, Dept. Envir<strong>on</strong>ment Canada, 174 pp.<br />

Hunter , J .A. , Neave, K.G., MacAulay, H.A. and<br />

Hobs<strong>on</strong>, G.D. (1978). Interpretati<strong>on</strong> of<br />

sub-seabottom permafrost in the Beaufort<br />

Sea by seismic methods. Part I. Seismic<br />

refracti<strong>on</strong> methods. in Proceedings, Third<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>,<br />

July 10-13, 1978, Edm<strong>on</strong>t<strong>on</strong>, Alberta,<br />

Canada, 514-520.<br />

Judge, A.S., MacAulay, H.A. and Hunter, J.A.<br />

(1976). An applicati<strong>on</strong> of hydraulic jet<br />

drilling techniques to mapping of subseabottom<br />

permafrost. Geological Survey of<br />

Canada, Paper 76-1C, 75-78.<br />

Mackay, J.R. (1972). Offshore permafrostand<br />

ground ice, Southern Beaufort Sea, Canada.<br />

Canadian Journal of Earth Sciences, 9,<br />

1550-1561.<br />

Mackay, D.K. and Mackay, J.R. (1974). Heat<br />

energy of the .Mackenzie River. Further<br />

Hydrologic Studies in the Mackenzie<br />

Valley, Dept. Envir<strong>on</strong>ment Canada,<br />

Envir<strong>on</strong>mental-Social Program, Northern<br />

Pipelines, Report 74-35, 1-24.<br />

O'C<strong>on</strong>nor, M.J. (1983). Development of a<br />

proposed model to account for the<br />

surficial geology of the Southern Beaufort<br />

Sea. Geological Survey of Canada, Open<br />

File 954, 128 pp.<br />

"-""* (1984). Distributi<strong>on</strong> and occurrence<br />

of frozen sub-seabottom sediments: A<br />

comparis<strong>on</strong> of geotechnical and shallow<br />

seismic evidence from the Canadian<br />

Beaufort Sea. Report prepared for the<br />

Geological Survey of Canada, 106 pp.<br />

Swift, D.W., Harris<strong>on</strong>, W.D. and Osterkarnp,<br />

T.E. (1983). Heat and salt transport<br />

processes in thawing subsea permafrost at<br />

Prudhoe Bay, Alaska. &I Proceedings,<br />

Fourth <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong><br />

<strong>Permafrost</strong>, July 17-22, 1983, Fairbanks,<br />

Alaska, 1221-1226.<br />

Taylor, A.E. and Allen, V. (1987). Shallow<br />

sediment temperature perturbati<strong>on</strong>s and<br />

sediment thermal c<strong>on</strong>ductivities, Canadian<br />

Beaufort Shelf. Canadian Journal of Earth<br />

Sciences, 24, 2223-2234.<br />

954

FOUNDATION CONSIDERATIONS FOR SITING AND DESIGNING<br />

THE RED DOG MINE MILL FACILITIES ON PERMAFROST<br />

T.G. Knewinski', T.A. Hammer2 and G.G. Booth3<br />

'Lakehead Testing Laboratory, Duluth, MN<br />

2Dames & Moore, Portland, OR<br />

3Cominco Alaska, Anchorage, AK<br />

SYNOPSIS The Red Dog Mine (zinc/lead) project is being advanced by Cominco Alaska Incorporated<br />

(CAI) and c<strong>on</strong>structi<strong>on</strong> at the mine site began in the winter of 1988. The mil facility for processing<br />

the ore into c<strong>on</strong>centrate will be located adjacent to the open pit mine <strong>on</strong> relatively warm permafrost<br />

soil and rock. This paper will summarize the site characteristics and describe the analytical<br />

and desiqn techniques utilized to found the various comp<strong>on</strong>ents of the mil facility. The more sensitive<br />

facilities will be m<strong>on</strong>itored during the early years of operati<strong>on</strong>s to verify that the foundati<strong>on</strong><br />

schemes selected are performing as designed.<br />

INTRODUCTION<br />

Develooment of the Red Doa Mine will reauire a<br />

tai 1 ings dam, water supply dam, mill site, dump<br />

areas for was t e fill and a series of diversi<strong>on</strong><br />

ditches. The mine and mill facilities are located<br />

at L<strong>on</strong>g i tude 162' 58' west and Latitude<br />

67" 66' north in northwestern Alaska. During<br />

the summers o f 1984 and 1985, and the winter of<br />

1987, Dames & Moore carried out geotechnical<br />

investigati<strong>on</strong> S at the sites and site alternatives<br />

for these fac<br />

geotechnical<br />

i lities. This paper summarizes the<br />

i nvestigati<strong>on</strong>s c<strong>on</strong>ducted to explore<br />

foundati<strong>on</strong> and thermal c<strong>on</strong>diti<strong>on</strong>s at the mil<br />

site locati<strong>on</strong> and provides the foundati<strong>on</strong> design<br />

c<strong>on</strong>cepts developed to support the mill facilities.<br />

The geotechnical investigati<strong>on</strong>s carried<br />

out are detailed in a previous paper by the<br />

author (Krezewinski, Stanley & Moore, 1986).<br />

The investigati<strong>on</strong>s were c<strong>on</strong>ducted during five<br />

separate field explorati<strong>on</strong>s, the first being<br />

c<strong>on</strong>ducted between June 19 and June 30, 1984, the<br />

sec<strong>on</strong>d between August 10 and September 2, 1984,<br />

the third between August 7 and August 16, 1985,<br />

the fourth <strong>on</strong> September 19, 1985, and the last<br />

being c<strong>on</strong>ducted between March 25 and April 1,<br />

1987. Twenty-nine borings were drilled in the<br />

vicinity of the mill site. Figure 1 is a Site<br />

Plan o,f the Mill Site which shows the locati<strong>on</strong>s<br />

of these borings. The boreholes were augered<br />

and/or cored to depths ranging from 8 to 113 feet<br />

(3 to 38 meters) for the purpose of logging subsurface<br />

soil and thermal c<strong>on</strong>diti<strong>on</strong>s and obtaining<br />

undisturbed soil and rock samples for identificati<strong>on</strong><br />

and laboratory testing.<br />

PROJECT DESCRIPT ION<br />

fuel storage, a power plant, roads, retaining<br />

walls and various other support facilities.<br />

Prior to c<strong>on</strong>stru ti<strong>on</strong> of facilities, the mill<br />

site will be exc<br />

ing from 967 to<br />

vated down to elevati<strong>on</strong>s rang-<br />

85 feet (original ground elevati<strong>on</strong>s<br />

shown <strong>on</strong> Figure 1). This will place<br />

most of the faci ities directly <strong>on</strong> bedrock. However,<br />

several of the facilities wil be located<br />

above bedrock <strong>on</strong> overburden soils and special<br />

design c<strong>on</strong>diti<strong>on</strong> S wil be required to ensure<br />

adequate foundat i <strong>on</strong> performance,<br />

FIELDWORK<br />

The field program utilized Central Mine Equipment<br />

Company (CME) -55 drill rigs which were<br />

transported to the various drill sites by a Bell<br />

205 helicopter. The CME-55's were equipped with<br />

both hollow stem auger for ,drilling and drive<br />

sampling overburden soils and wire-lin-e diam<strong>on</strong>d<br />

core drilling equipment with an opti<strong>on</strong>al refrigerated<br />

drilling-fluid unit for coring permafrost<br />

and maintaining the core in a frozen state.<br />

Nine of the twenty-nine holes were drilled<br />

utilizing refrigerated coring techniques. In<br />

ice-rich and ice-b<strong>on</strong>ded permafrost z<strong>on</strong>es, the<br />

<strong>on</strong>ly way to retrieve undisturbed core samples<br />

maintained at their in-situ densities is through<br />

the use of refrigerated coring techniques., The<br />

recovered core was protected from thawing in the<br />

field and the core was transported periodically<br />

to Anchorage for frozen storage.<br />

Thermistor strings were installed in 11 of the<br />

boreholes to permit future observati<strong>on</strong>s of the<br />

thermal c<strong>on</strong>diti<strong>on</strong> of the soil/rock at boring<br />

locati<strong>on</strong>s. Each thermistor string was placed in<br />

1.25 inch (3.2 centimeter) 1.0. PVC pipe install-<br />

A total of 25 bu ildinqs and support faci lities<br />

ed to the full depth and filled with a 50/50 mixhave<br />

been identi fied h y the designers as struc- ture of propylene glycol and water. The strings<br />

tures to be c<strong>on</strong>s tructe d in the mill site area at were installed to the bottom of the PVC pipe and<br />

the locati<strong>on</strong>s shown <strong>on</strong> Figure 1. The facilities the annular space between the PVC pipe and the<br />

include ore processing and storage facilities,<br />

borehole wall was backfilled with sand. A t the<br />

process water treatmen t facilities, accomodati<strong>on</strong>s, ground surface, a I ihort 5 ; ecti<strong>on</strong> of 3 or 4- inch<br />

955

(7.6 or 10.2-centimeter) diameter PVC pipe with materials encountered and determine their physia<br />

cap was placed over the 1.25 inch (3.2 cm) PVC cal and engineering characteristic. The laboracasing<br />

for protecti<strong>on</strong> of the thermistor string tory testing program included sample inspecti<strong>on</strong>,<br />

lead and c<strong>on</strong>necti<strong>on</strong>,<br />

sample photography, soil classificati<strong>on</strong>, moisture<br />

density measurements, gra.in-size analyses,<br />

Atterberg limits tests, c<strong>on</strong>stant head permeability<br />

tests, thaw c<strong>on</strong>solidatian tests and direct<br />

LABORATORY TESTING<br />

shear and triaxial shear strength tests.<br />

Soil and rock samples were tested in the Dames &<br />

Moore Anchorage laboratory to classify the<br />

FIG. 1<br />

RED DOG MILL SITE PLAN AND MONITORING LOCATIONS<br />

956

SITE CONDITIONS<br />

The millsite is located adjacent to both the ore<br />

deposit and the tailings dam. The entire site<br />

is covered with a low-growing tundra mat, The<br />

overburden Soils, which appear to be colluvial<br />

deposits capped with a thin layer of surficial<br />

silts and peat, vary in thickness from 0 to 13<br />

feet (0 to 4.3 meters). The underlying bedrock<br />

occurs as two distinct rock formati<strong>on</strong>s and appears<br />

to be separated by a thrust fault extending<br />

through the site. Bedrock to the west of<br />

the fault is chert-carb<strong>on</strong>ate while shales and ~<br />

sandst<strong>on</strong>es were logged to the east of the fault.<br />

The chert-carb<strong>on</strong>ate i s relatively competent,<br />

hard, dense, moderately-fractured chert and<br />

dolomite.<br />

The shale and sandst<strong>on</strong>e deposits c<strong>on</strong>tained numerous<br />

clay gouge z<strong>on</strong>es and excess ice down to<br />

depths of 20 to 30 feet (6.7 to 10 meters). The<br />

fractures and bedding within the chert deposit<br />

c<strong>on</strong>tained vitr<strong>on</strong>ite while vitr<strong>on</strong>ite was not<br />

logged within the shale and sandst<strong>on</strong>e deposit.<br />

The thermistor data at the mill site indicates<br />

permafrost temperatures in the 27 to 30°F<br />

(-2.8 to -1.IOC) range.<br />

DESIGN CONCEPTS<br />

The present plan at the mil site calls for excavati<strong>on</strong><br />

of 30 to 40 feet (IO to 13 meters) of<br />

material from the site for use as borrow in other<br />

areas and the founding of the heavier comp<strong>on</strong>ents<br />

of the mil <strong>on</strong> the more competent chert bedrock<br />

within the excavated site area.<br />

SITE EXCAVATION AND CONSTRUCTION MATERIALS<br />

Material to be excavated during site grading<br />

can be classified into 4 groups, depending <strong>on</strong><br />

soil c<strong>on</strong>stituents and ice c<strong>on</strong>tent. Table 1<br />

presents the 4 material classificati<strong>on</strong>s and<br />

characteristics used for categorizing the<br />

excavati<strong>on</strong> material.<br />

TABLE 1<br />

THERMAL ANALYSES FOR SITE EXCAVATION<br />

Thermal analyses using a computer soluti<strong>on</strong> of<br />

the Modified Berggren equati<strong>on</strong> (Braley 1984)<br />

were performed to evaluate the effect of excavating<br />

the site down to design grade. The required<br />

parameters for this method of analysis include:<br />

local climatological data, thermal properties<br />

of the in-situ soil and rock, and surface<br />

characteristics which are expressed in terms of<br />

an "n" factor. The climatological data includes<br />

the mean annual temperature, thaw degree-days<br />

and the number of thaw days annually. This informati<strong>on</strong><br />

was collected from a variety of<br />

sources including previous experience at the<br />

mill site. Physical properties of the in-situ<br />

soil and rock were determined by laboratory<br />

testing of relatively undisturbed samples obtained<br />

from subsurface explorati<strong>on</strong>s. Table 2<br />

c<strong>on</strong>tains a tabulati<strong>on</strong> of the input parameters<br />

used in our analysis:<br />

TABLE 2<br />

THERMAL ANALYSIS INPUT PARAMETERS<br />

Envir<strong>on</strong>mental Parameters<br />

Mean Annual Temperature (OF) 18 (-7.8'C)<br />

Thaw Degree Days ( O F days) 1400 (778'C days)<br />

Thaw Seas<strong>on</strong> Length (days) 140<br />

Material Classificati<strong>on</strong><br />

Restricted<br />

Use and<br />

Special Select<br />

Material Properties Waste Handling Material<br />

Thaw n 1.7 1.81.4<br />

Dry Density(lb/cu ft) 70-90 105-125 146<br />

Moisture (%) 20-30 2-15 2-4<br />

Heat Capacity<br />

(BTU/CU<br />

ft-OF) 29 27 28<br />

C<strong>on</strong>ductivity<br />

(BTU/ft-hr-'F) 0.7 1.1 1.7<br />

Latent Heat<br />

( BTUICU ft 2600-3000 400-2300 400-850<br />

NOTE: 1 gram/cu cm = 62.4 lb/cu ft<br />

1 BTU = 252.2 gr cal<br />

1 cu ft = 28317 cu cm<br />

1'C = 1.8'F<br />

CLASSIFICATION CATEGORIES FOR EXCAVATED MATERIAL<br />

The analysis was directed at evaluating the<br />

Materi a1 Group Material Characteristics<br />

thermal resp<strong>on</strong>se of the site to excavati<strong>on</strong> to<br />

Waste<br />

design grade and the beneficial effect <strong>on</strong> the<br />

Surficial/colluvium; high ice<br />

proposed foundati<strong>on</strong>s in areas of cut due to<br />

and/or organic c<strong>on</strong>tent; fine<br />

thawing and draining of excess ice from the<br />

grained with littl'e or no rock<br />

subsurface Soil and rock. The analyses included<br />

Restricted Use Typically directly beneath<br />

c<strong>on</strong>siderati<strong>on</strong> of the extent of the thaw resultwaste<br />

material; high ice c<strong>on</strong>- ing from exposure to both <strong>on</strong>e and two thaw<br />

tent (10% to 30% by volume);<br />

seas<strong>on</strong>s. The two thaw seas<strong>on</strong> scenario assumed<br />

significant gravel c<strong>on</strong>'tent<br />

that significant drainage would occur during<br />

(GM) with little organics<br />

the initial thaw seas<strong>on</strong>. Although total feeeze-<br />

Special Handling<br />

back would then occur during the intervening<br />

Relatively competent rock c<strong>on</strong>winter<br />

freeze seas<strong>on</strong>, the following summer thaw<br />

taining significant ice (5% to<br />

would produce greater thaw depths due to the<br />

10% by volume); less than 20%<br />

reduced moisture c<strong>on</strong>tent (and reduced latent<br />

fines<br />

heat) of the previously thawed and drained r<strong>on</strong>e.<br />

Select Material Re latively competent rock c<strong>on</strong>ta<br />

ining less than 5% ice by<br />

A summary of the analyses is presented below.<br />

vo lume; less than 20% fines<br />

957

THAW DEPTHS<br />

FOR EXCAVATED AREAS<br />

Material Thaw Depth(ft) Thaw Depth(ft)<br />

Classificati<strong>on</strong> 1 Thaw Seas<strong>on</strong> 2 Thaw Seas<strong>on</strong>s<br />

Waste Material 4-5(1.3-1.7 M) 5-6(1.7-2 M)<br />

Restricted Use &<br />

Special Handling 7-g(2.3-3 M) 9-lO(3-3.3 M)<br />

Select Material 9-lO(3-3.3 M) 9-lO(3-3.3 M)<br />

fOUNDATlONl ON HlQnlY<br />

1 FT EMBEDOYENT)<br />

FOUNDATION<br />

As the table indicates, allowing the site to<br />

thaw prior to c<strong>on</strong>structi<strong>on</strong> of facilities is<br />

beneficial, since the resulting reducti<strong>on</strong> of<br />

excess ice due to t4aw and drainage w i l l reduce<br />

settlement associated with thaw S train and creep.<br />

FOUNDATION DESIGNS<br />

Several of the mill facilities w i 11 be placed <strong>on</strong><br />

relatively unweathered to slight 1 y weathered<br />

bedrock while others will be founded <strong>on</strong> highly<br />

weathered bedrock. Foundati<strong>on</strong> loadings range<br />

from lightly loaded prefabricated structures to<br />

almost 500 kips (226,799 Kg)/footing and a<br />

100,000 kip (4,535,970 Kg) ore stockpile.<br />

Bujlding temperatures range from unheated to a<br />

60°F (15.6OC) heated floor slab with some<br />

facilities classified as highly sensitive to<br />

settlement.<br />

UNWCATHERLO<br />

INTACT LEDROCK<br />

0 io0 PO0 DO0 400 801<br />

ALLOWABLE 4OAD (KIP$)<br />

NOTE: 1 meter = 3 feet; 1 kip = 453.6 Kg.<br />

FIG. 2<br />

ALLOWABLE LOAD FOR SPREAD FOOTINGS<br />

FOUNDED ON BEDROCK<br />

FOUNDATIONS ON BEDROCK<br />

Based <strong>on</strong> informati<strong>on</strong> obtained<br />

face explorati<strong>on</strong>s, the follow<br />

likely be founded <strong>on</strong> relative<br />

rock:<br />

from the s U bsurng<br />

facilit i es will<br />

y competen t bed-<br />

Accomodati<strong>on</strong>s<br />

Primary crusher module<br />

Primary grinding and mil shop modul<br />

Primary and sec<strong>on</strong>dary gr nding modul<br />

Tertiarv arlndina module<br />

Zinc and iead flotati<strong>on</strong> module<br />

Lead and zinc dewatering module<br />

Mill feed thickener/claritier<br />

Water treatment module<br />

Most of the above facilities will be supported<br />

<strong>on</strong> spread footings. The bearing capacity<br />

analyses c<strong>on</strong>sidered foundati<strong>on</strong>s placed both <strong>on</strong><br />

relatively level undisturbed foundati<strong>on</strong> rock,<br />

and highly fractured rock caused by excavatian<br />

disturbance. Figure 2 presents curves for general<br />

sizing of spread footings, where facilities<br />

are to be founded <strong>on</strong> unweathered to slightly<br />

weathered bedrock (Bowles, 1977 and NAVFAC DM-<br />

7.2, 1982).<br />

Lateral capacity will be developed by a combinati<strong>on</strong><br />

of passive resistance and base frictian.<br />

Foundati<strong>on</strong>s embedded in competent rock and<br />

poured neat against the sides of the excavati<strong>on</strong><br />

will develop an allowable equivalent fluid<br />

pressure of 700 pounds per cubic foot (11.2 gr<br />

per cu cm) . If comva cted '2-inch (5.1-cm) minus<br />

crushed ro ck is installed adjacent to the footing,<br />

an a1 lowable equivalent fluid pressure of<br />

500 pounds per cubic foot (8.0 gr per cu cm) can<br />

e<br />

e<br />

be achieved. In additi<strong>on</strong>, base fricti<strong>on</strong> of <strong>on</strong>ehalf<br />

times the total vertical dead load is<br />

avallable provided 'the bottoms of the footing<br />

excavati<strong>on</strong>s are clean and free of loose rock and<br />

soil.<br />

The refrigerated coring performed during the<br />

first 1985 inyestigati<strong>on</strong> revealed that ice is<br />

present in the intact bedrock to c<strong>on</strong>siderable<br />

depth. The occurrence of ice was not comm<strong>on</strong>,<br />

however, and it appeared to be limited to fillings<br />

with'jn joints and fractures. In additi<strong>on</strong>,<br />

thermal analysis indicates that allowing the<br />

site to thaw prior to c<strong>on</strong>structi<strong>on</strong> of the PacJ1-<br />

ities will reduce the amount of excess ice to<br />

the depth of thaw as discussed in the previous<br />

secti<strong>on</strong>. Cansequently, we feel that thaw and<br />

creep settlement of foundati<strong>on</strong>s <strong>on</strong> rock will<br />

generally be less than I-inch (2.54 cm).<br />

FOUNDATION ON WEATHERED BEDROCK<br />

Based <strong>on</strong> available subsurface informati<strong>on</strong>,<br />

following facilities will be founded partly<br />

wholly <strong>on</strong> "restricted use" or "special hand<br />

weathered bedrock material:<br />

the<br />

or<br />

1 i ng"<br />

Coarse ore stockpile and feeder enclosures<br />

C<strong>on</strong>centrate storage building<br />

Freshwater tank and pump house<br />

Fuel oil storage and pump stati<strong>on</strong><br />

Mill site services complex<br />

Power house module<br />

The foundati<strong>on</strong>s for these<br />

ed to either maintain the<br />

facilities are designpermafrost<br />

in a frozen<br />

958

state or transmit the loads to the bedrock level<br />

or both. Heated and unheated buildings will be<br />

founded <strong>on</strong> spread footings within an insulated<br />

pad or <strong>on</strong> piles, when the buildings can be elevated<br />

to allow ambient air flow beneath the<br />

structure. In those areas where bedrock is not<br />

excessively deep, facilities will either be<br />

founded <strong>on</strong> tip end bearing piles or excavati<strong>on</strong><br />

replacement techniques wil be used to transmit<br />

loads to the bedrock strata. Examples of facilities<br />

with foundati<strong>on</strong>s that occur above the<br />

level of unweathered bedrock are discussed in<br />

the following paragraphs.<br />

Coarse Ore Stockpile and Feeder Enclosures:<br />

This facility c<strong>on</strong>sists of an 84-foot (28-meter)<br />

high c<strong>on</strong>ical pile of coarse ore overlying a<br />

double hopper/c<strong>on</strong>veyor system which supplies ore<br />

to the mil facilities. The hopper feeders and<br />

c<strong>on</strong>veyor system are enclosed beneath the ore<br />

pile in a horseshoe arch tunnel gallery c<strong>on</strong>structed<br />

of corrugated steel plate with rigid framing<br />

which is supported <strong>on</strong> reinforced c<strong>on</strong>crete footings,<br />

The c<strong>on</strong>veyor system wil be housed in<br />

two 9-foot (3-meter) diameter steel pipes. The<br />

ore stockpile is supplied via an overhead c<strong>on</strong>veyor<br />

system housed in a 9-foot diameter steel<br />

pipe. The overhead system is supported by guyed<br />

vertical supports which in turn are supported <strong>on</strong><br />

spread footings. The vertical columns wil support<br />

an approximate 100-foot (33.3 meter) span<br />

of the c<strong>on</strong>veyor system at about 400 pounds per<br />

foot (540 Kg per meter), resulting in a vertical<br />

downward load <strong>on</strong> the order of 40 kips (18,140 Kg)<br />

for each support, A protective umbrella wil<br />

also be supported over the stockpile to reduce<br />

dust. A total storage capacity of the coarse<br />

ore pile will be approximately 50,000 t<strong>on</strong>s<br />

(4,535,970 Kg).<br />

Based <strong>on</strong> informati<strong>on</strong> obtained from subsurface<br />

explo r ati<strong>on</strong>s, the proposed facility site i s<br />

under 1 ain by approximately 12 feet (4 meters) of<br />

ice-r i ch colluvium which, in turn, is underlain<br />

by sl i ghtly to severely weathered carb<strong>on</strong>aceous<br />

shale with occasi<strong>on</strong>al to frequent 1/8 to 1/4<br />

inch 0.3 to 0.6 cm) ice filled fractures to the<br />

total depth of the boring (50 feet/16.7 meters).<br />

General site excavati<strong>on</strong> wil remove the colluvium<br />

and about 9 feet (3 meters) <strong>on</strong> average of<br />

the ice-rich bedrock. In additi<strong>on</strong>, thermal<br />

analysis indicates that allowing the site to<br />

thaw after site excavati<strong>on</strong> and prior to c<strong>on</strong>structi<strong>on</strong><br />

wil eliminate the excess ice in the bedrock<br />

to a depth of 7 to 9 feet (2.3 to 3 meters)<br />

and 9 to 10 feet (3 to 3.3 meters) for <strong>on</strong>e and<br />

two 'thaw seas<strong>on</strong>s, respectively.<br />

C<strong>on</strong>sidering the beneficial effects of removing<br />

the upper ice-rich colluvium and bedrock and the<br />

reducti<strong>on</strong> of excess ice due to two thaw seas<strong>on</strong>s,<br />

the analysis indicates that the coarse ore pile<br />

and the underlying facilities will settle up to<br />

6 inches (15.2 cm) due to creep. This settlement<br />

wil be greatest at the center of the ore<br />

pile and diminish to less than 1 inch (2,s cm)<br />

at the pile edge. The total settlement should<br />

occur at an estimated rate of <strong>on</strong>e-half inch<br />

(1.3 cm) per year. The analysis assumes that<br />

the gallery is supported <strong>on</strong> spread footings with<br />

c<strong>on</strong>tact pressures of 10 ksf<br />

(4.9 Kg per sq cm)<br />

and that subsurfa ce c<strong>on</strong>diti<strong>on</strong>s do not vary significantly<br />

across the area of the ore pile. Due<br />

to the uncertaint ies associated with the analy-<br />

959<br />

sis, greater settlements (in excess of 6 inches/<br />

15.2 cm) may occur. Therefore, the structures<br />

underlying the ore pile will be m<strong>on</strong>itored for<br />

settlement by periodic level surveys at selected<br />

points al<strong>on</strong>g the c<strong>on</strong>veyor and hopper galleries,<br />

In additi<strong>on</strong>, a thermistor string will be installed<br />

to the west of the c<strong>on</strong>centrate pile between<br />

the below ground c<strong>on</strong>veyor galleries. It is anticipated<br />

that moderate settlement of the hopper<br />

and c<strong>on</strong>veyor systems can be compensated for by<br />

periodic adjustment utilizing jacking or shimming<br />

methods. Excessive settlement, although unlikely,<br />

may require that the galleries be releveled after<br />

several years of use.<br />

The vertical columns supporting the overhead<br />

c<strong>on</strong>veyor system wil be founded <strong>on</strong> spread footings<br />

embedded 5 feet (1.7 meters) into the exposed<br />

weathered bedrock (.special handling material).<br />

As stpted previously, the weathered bedrock<br />

should experience about 9 feet (3 meters) of thaw<br />

if exposed to two thaw seas<strong>on</strong>s. Settlement due<br />

to creep can be reduced to tolemble levels if<br />

the bearing stresses acting <strong>on</strong> the lower boundary<br />

of the previously thawed z<strong>on</strong>e (9 feet-3 meters)<br />

are limited to 2 ksf (1.0 Kg per sq cm). Accordingly,<br />

allowable bearing stresses imposed by the<br />

sp.read footing embedded to a 5-fOOt (1.7 meters)<br />

depth wil be limjted to about 5.5 ksf (2.1 Kg<br />

per sq cm). Foundati<strong>on</strong>s designed accordin ly<br />

should experience less than 2 inches (5 cm total<br />

settlement,<br />

Power House Module:<br />

The power house module is located at the southwestern<br />

porti<strong>on</strong> of the Process Facility Complex.<br />

The power house is c<strong>on</strong>sidered very sensitive to<br />

settlement and wil be supported <strong>on</strong> individual<br />

spread footings with a maximum vertical load of<br />

about 240 kios (108,860 Kq).<br />

ExtensSve c uts<br />

ranging from'about 30 to 40 feet (IO to<br />

13<br />

meters) in thickness wil be required at the<br />

site. As a result, the finished floor o f the<br />

module wil be primarily in bedrock, but the far<br />

western porti<strong>on</strong> may lie in special hand1 i ng<br />

materi a1<br />

.<br />

The excavati<strong>on</strong> for the Dower house modul e will<br />

be.lEft open for at least <strong>on</strong>e thaw seas<strong>on</strong> prior<br />

to c<strong>on</strong>structi<strong>on</strong>. This should induce thaw well<br />

into the select material, Since the power house<br />

module has been classified as very sensitive to<br />

movement and since sloping rock strata are present<br />

beneath the facility, the structure wil be<br />

designed for a low allowable bearing value.<br />

Footings embedded at least 3 feet (1 meter) below<br />

finished grade wil be designed using an<br />

allowable bearing capacity of 6 ksf (2.9 Kg per<br />

sq cm). Foundati<strong>on</strong> c<strong>on</strong>structed as described<br />

above will undergo estimated total thaw and<br />

creep settlement of less than 1 inch (2.5 cm).<br />

INSPECTION AND MONITORING<br />

Variati<strong>on</strong>s in subsurface c<strong>on</strong>diti<strong>on</strong>s wil probably<br />

be encountered during c<strong>on</strong>structi<strong>on</strong>. In order<br />

to permit correlati<strong>on</strong>s between the foundati<strong>on</strong><br />

utilized and the actual c<strong>on</strong>diti<strong>on</strong>s encountered<br />

with the plans and specificati<strong>on</strong>s, a qualifi ed<br />

geotechnical engineer wil perform daily c<strong>on</strong><br />

structi<strong>on</strong> inspecti<strong>on</strong>s. Observati<strong>on</strong>s made du ring<br />

these inspecti<strong>on</strong>s will include, but not be 1 i mi ted<br />

to, the following:

1.<br />

2,<br />

3.<br />

4.<br />

5.<br />

6.<br />

7.<br />

Delineating and categorizing excavati<strong>on</strong><br />

material as waste, restricted use, special<br />

handling, and select.<br />

Proper ground preparati<strong>on</strong> for fill<br />

placement. Determining ice-rich z<strong>on</strong>es<br />

and/or waste material z<strong>on</strong>es where over<br />

excavati<strong>on</strong> will be required.<br />

Fill placement procedures and fill<br />

density testing.<br />

Fill gradati<strong>on</strong> and quality m<strong>on</strong>itoring<br />

and testing.<br />

Foundati<strong>on</strong> excavati<strong>on</strong>s.<br />

Installati<strong>on</strong> and initial reading of<br />

m<strong>on</strong>itoring instrumentati<strong>on</strong>.<br />

Stability of'cut slopes, retaining<br />

structures and drainage structures.<br />

A m<strong>on</strong>itoring scheme has been developed for several<br />

of the mill site facilities, where foundati<strong>on</strong><br />

c<strong>on</strong>diti<strong>on</strong>s are difficult and/or sensitive<br />

structures are located. Figure 1 includes a<br />

site plan showing where thermistor strings and<br />

vertical c<strong>on</strong>trol survey pegs will be installed.<br />

The number of m<strong>on</strong>itoring locati<strong>on</strong>s shown <strong>on</strong> the<br />

figure are c<strong>on</strong>sidered to be a minimum; additi<strong>on</strong>al<br />

survey pegs may also be placed <strong>on</strong> any of the<br />

heated facilities founded above bedrock. In<br />

additi<strong>on</strong> to the m<strong>on</strong>itoring points, periodic site<br />

inspecti<strong>on</strong>s will be performed to assess the performance<br />

of cut slopes, retaining structures,<br />

drainage structures and fill secti<strong>on</strong>s. Site<br />

inspecti<strong>on</strong>s duri.ng the early and late summer<br />

periods (June and September) would provide the<br />

most relevant informati<strong>on</strong>. All thermistor<br />

strings and settlement points will be m<strong>on</strong>itored<br />

<strong>on</strong> a regular basis. The following reading schedule<br />

has been recommended for the first two<br />

years after installati<strong>on</strong>:<br />

Once in early May, just before breakup<br />

June through September, <strong>on</strong>ce each m<strong>on</strong>th<br />

Once each in.November, January and March<br />

The data will be analyzed as so<strong>on</strong> as possible<br />

after reading during the early stages. Where<br />

signs of movement or thermal degradati<strong>on</strong> are<br />

detected, the m<strong>on</strong>itoring schedule will be accelerated<br />

to refine definiti<strong>on</strong> of performance. In<br />

this way, remedial measures can be instigated<br />

before damage to facilities occurs.<br />

After 2 years, if performance of facilities is<br />

satisfactory, the m<strong>on</strong>itoring schedule will be<br />

reduced to just a few readings per year,<br />

n<strong>on</strong>-existent and a well planned system for m<strong>on</strong>itoring<br />

short and l<strong>on</strong>g term performance is an<br />

important part of design process,<br />

REFERENCES<br />

Braley, W.A. (1984). A Pers<strong>on</strong>al Computer<br />

Soluti<strong>on</strong> to the Modified Beraaren Eauati<strong>on</strong>.<br />

Alaska DOT/PF Report No. AK-ib-85-19,<br />

Fairbanks, Alaska<br />

Bowles, J.E. (1977). Foundat i <strong>on</strong> Analysis and<br />

Design, 2nd Editi<strong>on</strong>, 750 pp. McGraw-Hill,<br />

Inc.<br />

Krtewinski, T.G., Stanley, J.M., & Moore, D.W.<br />

(1986). Geotechnical Investigati<strong>on</strong> -<br />

Cominco's Red Dog Mine Facilities.<br />

Proc, Fourth <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Cold Regi<strong>on</strong>s<br />

Engineering Specialty <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> (ASCE),<br />

Anchorage, Alaska.<br />

NAVFAC DM - 7.2 (1982). Foundati<strong>on</strong>s And Earth<br />

Structures - Design Manual, Department of<br />

The Navy.<br />

ACKNOWLEDGEMENTS<br />

Acknowledgement is made to Cominco Alaska, Incorporated,<br />

for their support during this design<br />

effort and for their permissi<strong>on</strong> to publish this<br />

paper.<br />

CONCLUSIONS<br />

The founding of a world class mine's mill<br />

facility <strong>on</strong> relatively warm permafrost soil and<br />

rock is within the capabilities of the current<br />

state of the practice in arctic geotechnical<br />

engineering. Utilizing standard geotechnical<br />

analysis techniques and current understanding<br />

of the creep phenomen<strong>on</strong>, buildable foundati<strong>on</strong>s<br />

for large, heavily loaded facilities <strong>on</strong> permafrost<br />

rock can be designed. The performance<br />

data for similar structures is, however, nearly

ELECTRIC PROSPECTING OF INHOMOGENEOUS FROZEN MEDIA<br />

V.V. Kuskov<br />

Faculty of Geology, Moscow State University, M~scow, USSR<br />

SYNOPSIS<br />

To attain tbe increased efficiency of electrical prospecting of inhomogeneous<br />

media it ia necesealy to develop two- and three-dbensi<strong>on</strong>al interpretati<strong>on</strong> apparatus including: a<br />

body of mathematics for the soluti<strong>on</strong> of direct pmblems; library of typical models of inhomogeneous<br />

media; methodology of experimental work; and interpretati<strong>on</strong> methods. Two-dimensi<strong>on</strong>al b-<br />

terpretati<strong>on</strong> procedures for gome classes of two-dimensi<strong>on</strong>al models are discussed. The principles<br />

of interpreting the<br />

formulated.<br />

data 09 electrical sounding of horiz<strong>on</strong>tally-inhomogeneous media have been<br />

In engineering-geological studies of frosen<br />

grounds great role is played by field geophysical<br />

methods enabling to promptly survey an area<br />

to a required depth. The dependence aP SpeCific<br />

electrical resistivity of gmunds <strong>on</strong> their<br />

lithology , f racturjng, moisture c<strong>on</strong>tent, and<br />

temperature makes it possible to apply electrometric<br />

prospecting methods to obtain data needed<br />

for compilbg maps of the permafrost z<strong>on</strong>e.<br />

Electric prospecting by the msistlvity method<br />

is of prime importance in such studies<br />

due to its sufficient efficiency and sfmplicity.<br />

The existbg interpretati<strong>on</strong> apparatus of electric<br />

pmspectk rsets <strong>on</strong> the analytical SoLuti<strong>on</strong>a<br />

obtained Box hol-iz<strong>on</strong>tallg and verticallylayerad<br />

geoelectric models. <strong>Permafrost</strong> geoelectric<br />

profilea are distinguished by their<br />

great spatial variability, therefore, actual<br />

media cannot often be satisfactorily approximated<br />

by such mode16. Practice has shown that<br />

the formalistic use of the <strong>on</strong>e-dhensi<strong>on</strong>al interpretati<strong>on</strong><br />

apparatus may lead to grave errom.<br />

Two- and three-dimensi<strong>on</strong>al interpretati<strong>on</strong> of<br />

the ERM is needed to study horiz<strong>on</strong>tally inhomogeneous<br />

media. The main problems here are:<br />

modeling of electric fields In inhomogeneous<br />

media such a8 methods of fintte differences,<br />

finite elements , and integral equati<strong>on</strong>s are<br />

oomm<strong>on</strong>ly employed. The most simple and universal<br />

is the finite deference method. It<br />

a88umes quantizati<strong>on</strong> of the model under study<br />

and approximake soluti<strong>on</strong> of respective boundary<br />

problem.<br />

We have developed a body of mathematics and a<br />

package of programs for finite-difference simulati<strong>on</strong><br />

of direct ERM problems for two-dimensi<strong>on</strong>al<br />

models (Baatis and Kuskov , 1985; Kuskov,<br />

"1985 1986). At- present, a Library of two-dimensi<strong>on</strong>al<br />

geoelectrical madelm, most typical OP<br />

the permafrost regi<strong>on</strong>s, is being established.<br />

Thus for hstmce, very many estimati<strong>on</strong>s of<br />

l<strong>on</strong>ghxdinal and transverse ,curves of vediical<br />

electrical soundbg (VES) for 811 escarpment,<br />

horst, graben, cylindrical hsert of a rectaagular<br />

cross-secti<strong>on</strong>, semi-c<strong>on</strong>fined horiz<strong>on</strong> etc,<br />

have been made. We have c<strong>on</strong>sidered several<br />

geometric patterns of these models for various<br />

combinati<strong>on</strong>s of specific resistivity, The estlnati<strong>on</strong><br />

results have been ueed to com iLe an<br />

album of master curves<br />

(Ruskov , .lSd.<br />

(11 development of interpretati<strong>on</strong> apparatus A.n analysis of the estimated data and practicaJ<br />

permitting soluti<strong>on</strong> of direct problems experience of the ERM applicati<strong>on</strong> in inhomogeof<br />

ERM for horiz<strong>on</strong>tally hhomogeneoue neous media led to the development of principles<br />

models;<br />

underlying the interpretati<strong>on</strong> of the resist iviQ<br />

method data.<br />

(2) establishment of a library of typical<br />

models of inhomogeneous media;<br />

While studying two- and three-dimensi<strong>on</strong>al Fnho-<br />

(3) validati<strong>on</strong> 09 field work methodology; mogeneous media, a problem arises of choosing<br />

(4) development of the principles undeefficient<br />

observati<strong>on</strong> systems to assist inoblying<br />

the ERM data interpretati<strong>on</strong> for taining informati<strong>on</strong> adequate for an unambiguous<br />

inhomogeneous media.<br />

soluti<strong>on</strong> of the inverse problem. We believe<br />

that an unambiguous determinati<strong>on</strong> of the elect-<br />

These problems have been studied for several ric c<strong>on</strong>ductivity of a medium necessitates the<br />

years at the Department of Geocryology, Moscow cohcidence of the dimensi<strong>on</strong>s of experimental<br />

State University.<br />

data and the object under study. In other<br />

words, in <strong>on</strong>e- two- and three-dimensi<strong>on</strong>al cas-<br />

Potentialities of analytical methods for solving we should ob& <strong>on</strong>e-, two- and three-dimendirect<br />

problems of the ERNI are limited to stu- si<strong>on</strong>al functi<strong>on</strong>s of appweni* resutivity :<br />

dying models with <strong>on</strong>ly inhomogeneous electrical<br />

pa(r,x) , and p,(r,x,y) , respectic<strong>on</strong>ductivity,<br />

Numerical methods of mathematical<br />

961

. - - ""<br />

_"" _"_<br />

souidiniag-BtatioiiE bn the gmund surface with<br />

the y axis directed al<strong>on</strong>g the extensi<strong>on</strong> of the<br />

two-dimensi<strong>on</strong>al models, Unfortunatelyt this<br />

assumpti<strong>on</strong> has so Tar been proved <strong>on</strong>ly for the<br />

<strong>on</strong>e-dimensi<strong>on</strong>al case (the Tikh<strong>on</strong>ov's theorem),<br />

but the physical sense of soundings allows UB<br />

to believe in its validity.<br />

Let ua c<strong>on</strong>sider a case of two-dimensi<strong>on</strong>al media.<br />

The general principle of SolvFng bverse problems<br />

is the minfmizati<strong>on</strong> of the BiBCrepancy<br />

between the observed and estimated data:<br />

"<br />

where, P and P E are, respectively, the<br />

. . . , n; j=l ,.. . , m; n i s a number<br />

observed and estimated characteristics of a<br />

field; i=l,<br />

of quantizati<strong>on</strong> points in sounding curves; m<br />

is a number of sounding atati<strong>on</strong>s; and 'p is<br />

the vector of the selected model parameters.<br />

Commensurability of functi<strong>on</strong>al values P@) with<br />

the data accuracy is regarded as a criteri<strong>on</strong><br />

of the terminati<strong>on</strong> o$ the interpretati<strong>on</strong> process.<br />

Since the direct problem soluti<strong>on</strong> st111 requires<br />

great computing resources, it is necessar to<br />

develop methods producing adequate Fnitiai approxhati<strong>on</strong>s<br />

for the SQkCtiOn procedure.<br />

Interpretati<strong>on</strong> of soulldhg data should be carried<br />

out Fn the classes of simplified models.<br />

Hence, there is a need to typify the whole<br />

wealth. of geoelectrical inhomogeneities and to<br />

select such classes of models, which, <strong>on</strong> the<br />

<strong>on</strong>e hand easily approxbnate real situati<strong>on</strong>s,<br />

and, <strong>on</strong> ihe other, could be described by few<br />

parameters. An analysis of.the soluti<strong>on</strong>s of<br />

diPect problems makes it possible to develop a<br />

system of diagnostic criteria for the selecti<strong>on</strong><br />

of the required class of models. A cbaracteristic<br />

behavior of some sounding curves usually<br />

lays the basis for diagnostics. In our ophi<strong>on</strong>,<br />

apparent res irt iv ity ( pa (r, x) ) profiles<br />

should be used to this end.<br />

We have studied apparent resistivity profiles<br />

for typical two-dinensi<strong>on</strong>al structures. TheLr<br />

analysis has shown that: (I) isolhes of apparent<br />

resistivities easily approximate the real<br />

geometry of a structure; and (2) correlati<strong>on</strong><br />

of resistivities of a node1 does not practicallg<br />

affect the specific features of structures un-<br />

der study. Here are some f=mPles- Figs.1,<br />

2 and 3 show the pa profiles f or the models<br />

of an escarpment and an insert. Sounding was<br />

carried out in a VEj modificati<strong>on</strong>.<br />

While comparing Figs. I and 2, it becomes obviom<br />

that l<strong>on</strong>gitudinal V B (9' (r,x)) reflect a model<br />

geometry better. Propile p', (r,x), un-<br />

4<br />

like transverse soundinngs ( fa(r,x)) does not<br />

inherit specific features of an escarpment in<br />

an area of expanded arrays r. This property<br />

of l<strong>on</strong>gitudinal soundings should be taken into<br />

account in planning field work.<br />

Fig.1 The p(r,X) profile for tba<br />

model of an escgrpment with a highresistance<br />

basement<br />

f<br />

3<br />

H<br />

Fig.2 The P' (r,x) profile for the<br />

model or an esc8rpmen.t; with a highresistance<br />

basement<br />

2M<br />

- - -f,O<br />

Fig.7 The ff profile for the model<br />

of a high-resisthe insert of rectangular<br />

crosa-secti<strong>on</strong> (top)<br />

962

Wben interpreting, <strong>on</strong>e ,should make the best An analyeis of the estimated curves fox inhomouse<br />

of a well-developed <strong>on</strong>e-dimenei<strong>on</strong>al body geneous models has allawed us to make ph~ysLcal.<br />

of mathematics for soLv& the invsree problem. classificati<strong>on</strong> of distorting effects based <strong>on</strong><br />

With this in viewt the need is to evolve a the attem of dlveergeaoies of nomsi curves<br />

theom of distorti<strong>on</strong>s. Manifestati<strong>on</strong>s of hori- ( 9 P -1. obtabed above a boriz<strong>on</strong>taLl.y-layersd<br />

del-class, are distorted withii a limited range<br />

of arrays (Fig.4). We called this effect a<br />

-.<br />

"<br />

t<br />

z-<br />

~""" I

L<strong>on</strong>gitudinal local. effect. TraneverBe soundings<br />

are fraught with more complicated diatorti<strong>on</strong>s<br />

that are of similar type in various models.<br />

The following two distorting effects can be<br />

distiguishedt (a) 89 effect produced by current<br />

electrodeswhen they cross the vertical bowdarg<br />

of the structure being studied. This<br />

effect which manifests itself locally <strong>on</strong> the<br />

VFS curves has been termed by us as transverse<br />

local effect; and (b) an effect, diatorting<br />

the right branch of the vp;6 curve (we call it<br />

asymptotic effect), associated with the occurrence<br />

of an inhomogeneity near a maasurbg<br />

electrode.<br />

In the coume<br />

of interpretati<strong>on</strong> by a <strong>on</strong>e-<br />

dimensi<strong>on</strong>al scheme the identified distorting<br />

effects led to normal errors. Thus the appearance<br />

of <strong>on</strong>e, more seldom, two fictitious<br />

layers in a geoelectrical profile is due to 10-<br />

cal effects, whXle errors in determinati<strong>on</strong> of<br />

electrical c<strong>on</strong>ductivity of a structure base<br />

are associated with an asymptotic effect (Kuskov<br />

1986) These regularities may be useful<br />

in the inteqret.ati<strong>on</strong> practice.<br />

In practice it is important to identify infoamati<strong>on</strong><br />

a fortiori suitable for <strong>on</strong>e-dimensi<strong>on</strong>al<br />

Fnterpret,ati<strong>on</strong>. Hence, profiles of apparent<br />

resistivities Shdd be used Areas where 9,<br />

isolines differ from the horiz<strong>on</strong>tal <strong>on</strong>es are<br />

Fadicative of the distortbg effect of inhomogeneities.<br />

Waving specified the locati<strong>on</strong> of m<br />

excitati<strong>on</strong> boundarg in the profile and follo-<br />

While plan-<br />

determined from %he formula r =<br />

where, x Js a distance from the sounding point<br />

to an inhomogeneity; and h is a depth to ita<br />

upper edge. In Figs.1 and 2 these mays are<br />

divided by a broken line.<br />

In the cases when the applicati<strong>on</strong> of traditi<strong>on</strong>al<br />

Fnterpretatioa methods is impossible, the<br />

use should be made of two-dimensi<strong>on</strong>al. apparatus<br />

of Fntemretati<strong>on</strong>. Therefore. the nrin-<br />

- identificati<strong>on</strong> of the type of Fnhomogemeitties<br />

by using profiles o f apparent<br />

resistivities;<br />

- analysis of distorti<strong>on</strong>s to make the best<br />

use of the sunsratus of <strong>on</strong>e-dhensi<strong>on</strong>al<br />

- soluti<strong>on</strong> of the inverse problem by the<br />

method of selecti<strong>on</strong> using the estimated<br />

master Curves or numerical modeling.<br />

The methodology described remains quite valid<br />

for three-dhensi<strong>on</strong>al cases.<br />

REFERENCES<br />

Bastis, A.Iy 80 KUSkOV, V.V. (I 985). 0 chislmnom<br />

resheniF dvumerno-neodnorodnvkh<br />

Uoskva,<br />

'.<br />

Kuskov, V.V. (1985). Chislennoe modelirovanie<br />

vertikalagkh electricheskikh z<strong>on</strong>diro;raniy<br />

v dvumsrno-neodnorodnykh sredalth. - Vest-<br />

nik Moskovako o universiteta, ser.4 -<br />

geologiya, ('If, 82-88, i;ioskva.<br />

Kuskov, V.V. (19%) Matenaticheskoe modelirovanie<br />

pri izuchenii dvumexno-neodnorodny&<br />

sred metodom VES. Kand.diss., 1% pp.<br />

Moskva.<br />

964

SYNOPSIS Presented in this paper is a new method which will allow <strong>on</strong>e to predict the<br />

permafrost thickness <strong>on</strong> the basis of temperature measurements in deep wells made<br />

after a relatively short shut-in time. This method employs four transient temperature<br />

measurements taken at two depths (below the permafrost base) with two<br />

calculated,static (undisturbed) temperatures at these depth&. The geothermal<br />

gradient 1s determined and the politi<strong>on</strong> of the permafrost base is estimated.<br />

Values of permafrost thickness for 15 Northern Canadian wells have been used to<br />

verify the- suggested method.<br />

INTRODUCTION<br />

The development of rapid methods of predicting<br />

permafrost temperatures and thicknesses<br />

is essential to progress in the areas<br />

of geophysics, well drilling, oil/gas producti<strong>on</strong>,<br />

and mining. - In some cases, the thickness<br />

of the permafrost can be estimated from<br />

resistivity, s<strong>on</strong>ic, and surface seismic<br />

velocity logs * The permafrost properties<br />

sought by borehole logging measurements include<br />

the depth of the permafrost base, the<br />

type of soil , and the type and amount of<br />

material in the pore space. Because deep<br />

wells in permafrost areas are usually drilled<br />

with a warm mud, there is some unknown degree<br />

of melting around the well * Thus, the<br />

borehole correcti<strong>on</strong> required for log interpretati<strong>on</strong><br />

can become quite large and is often<br />

indeterminate. The base of the permafrost<br />

can be detected with resistivity and s<strong>on</strong>ic<br />

logs. The transiti<strong>on</strong> from higher resistivity<br />

and velocity readings to lower values can be<br />

c<strong>on</strong>sidered as the base of the permafrost.<br />

The electrical resistivities of frozen sediments<br />

are affected to a greater extent than<br />

are. seismic velocities. Seismic velocities<br />

may increase by 2 to 10 times in transiti<strong>on</strong><br />

to a frozen state, whereas the electrical<br />

resistivity may increase by 30 to 300 times<br />

in the same temperature interval (Hnatiuk and<br />

Randall, 1977). Laboratory data for the<br />

electric and acoustic resp<strong>on</strong>se of frozen<br />

soils have shown that the significant variables<br />

affecting these parameters are<br />

salinity, surface area of soils per unit of<br />

volume, temperature, and water c<strong>on</strong>tent.<br />

Thus, the laboratory data should be used to<br />

interpret the log resp<strong>on</strong>se. Since it is difficult<br />

to perform such laboratory studies,<br />

the temperature logs are comm<strong>on</strong>ly used to<br />

determine the permafrost temperature and<br />

thickness.<br />

When wells are drilled through<br />

permafrost,<br />

the natural temperature field of the<br />

formati<strong>on</strong>s (in the vicinity of the borehole)<br />

is disturbed and the frozen rocks thaw for<br />

some distance from the borehole axis. To<br />

determine the static temperature of the formati<strong>on</strong><br />

and permafrost thickness, <strong>on</strong>e must<br />

wait for some period after completi<strong>on</strong> of<br />

drilling before making geothermal measurementa.<br />

This is the so-called restorati<strong>on</strong><br />

time, after which the difference between the<br />

temperature of the formati<strong>on</strong> and that of the<br />

fluid is leas than -the needed measurement accuracy.<br />

The presence of permafrost has a<br />

marked effect <strong>on</strong> the time required for tho<br />

near-well-bore formati<strong>on</strong>s to recover their<br />

static temperatures. The durati<strong>on</strong> of<br />

refreezing of the layer thawed during drilling<br />

is very dependent <strong>on</strong> the natural temperature<br />

of the formati<strong>on</strong>: therefore, the rocks<br />

at the bottom of the permafrost refreeze<br />

slowly. A lengthy restorati<strong>on</strong> period of up<br />

to ten years or more is required to determine<br />

the temperature and thickness of permafrost<br />

with sufficient accuracy (Lachenbruch and<br />

Brewer 1959; Judge 1973: Melinkov et al.<br />

1974; Taylor et al. 1977; Judge et al. 1979;<br />

Taylor et al. 1982).<br />

The objective of this<br />

present a new "two point" paper<br />

is to<br />

method which will<br />

permit <strong>on</strong>e to determine the permafrost thickness<br />

from short-term (in comparis<strong>on</strong> with the<br />

time required for temperature restorati<strong>on</strong>)<br />

downhole temperature logs.<br />

PHYS IChL MODEL<br />

The slow return to thermal equilibrium<br />

in the secti<strong>on</strong> of the well within the permafrost<br />

creates serxous difficulties in<br />

determining the permafrost temperature and<br />

965

thickness. It io clear that in the secti<strong>on</strong>s<br />

of the borehole below the permafrost, the<br />

static (undisturbed) formati<strong>on</strong> temperatures<br />

can be predicted from temperature logs taken<br />

at relatively short shut-in times. The<br />

proposed "two point" method of predicting the<br />

permafrost thickness is based <strong>on</strong> determining<br />

the geothermal gradient in a uniform layer<br />

below the permafrost z<strong>on</strong>e (Figure 1).<br />

Therefore. a lithological profile for the<br />

h -h secti<strong>on</strong> of the well must be available.<br />

2 P<br />

Only four temperature measurements ( T1 ,T2)<br />

for two depths hl,hz) are needed to determine<br />

the geothermal gradient. The positi<strong>on</strong> of the<br />

permafrost base is predicted by the extrapolati<strong>on</strong><br />

of the static formati<strong>on</strong> temperature<br />

- depth curve to O°C (Figure 1). It<br />

should be noted that in this paper the permafrost<br />

base is deffned as the O°C isotherm.<br />

The existence of a more severe climate in the<br />

past or the transgressi<strong>on</strong> of the Arctic<br />

Shoreline results in warming and thinning of<br />

the permafrost (Balobaev et al. 1973;<br />

Lnchenbruch et al. 1982). Due to slow movement<br />

of. the permafrost base, the temperature<br />

field in the secti<strong>on</strong> of the well below the<br />

permafrost is also disturbed. An approximate<br />

equati<strong>on</strong> which permits <strong>on</strong>e to estimate the<br />

thickness of the disturbed z<strong>on</strong>e (it the, rate<br />

of permafrost thinning is . known) was<br />

presented by Melnikov et al. (1974). Thus<br />

the accurate value of geothermal gradient can<br />

be determined <strong>on</strong>ly from temperature measurements<br />

below this disturbed z<strong>on</strong>e. Our experience<br />

ha0 shown that if the c<strong>on</strong>diti<strong>on</strong><br />

h -h > 20m (Figure 1) i5 satisfied, the geo-<br />

1 P<br />

thermal gradient can be estimated with good<br />

accuracy.<br />

WRKING FORMULAS<br />

The mathematical model of the "two<br />

point" method is based <strong>on</strong> the assumpti<strong>on</strong> that<br />

in deep wells the temperature of drilling mud<br />

at a given depth is practically c<strong>on</strong>stant<br />

during the drilling process (Kutasov 1968:<br />

Kutasov 1976). The results of temperature<br />

surveys in deep wells have shown that this<br />

assumpti<strong>on</strong> is valid (Bullnrd 1947:<br />

Lachenbruch and Brewer 1959: Jaeger 1961:<br />

Kutasov et al. 1966).<br />

Fluctuati<strong>on</strong>s in the formati<strong>on</strong> temperature<br />

near the well must first be determined,<br />

allowing for the circulati<strong>on</strong> of drilling<br />

fluid with a temperature Tm. The following<br />

values are given: rw, the radius of the well:<br />

tl, the Circulati<strong>on</strong> time (disturbance time)<br />

of the drilling fluid at a given depth: Tf,<br />

the formati<strong>on</strong> static temperature; and a. the<br />

thermal diffusivity of the formati<strong>on</strong>.<br />

It is well known that the appropriate<br />

thermal c<strong>on</strong>ducti<strong>on</strong> equati<strong>on</strong> ha5 a soluti<strong>on</strong> in<br />

integral form, the integral being solvable<br />

<strong>on</strong>ly by numerical means (Jaeger I956 1. We<br />

have found that, for moderate and large<br />

h<br />

I-r<br />

ooc<br />

-\ \<br />

Fig. 1. <strong>Permafrost</strong> base predicti<strong>on</strong> -<br />

- a Schematic Model<br />

values of the dimensi<strong>on</strong>less circulati<strong>on</strong><br />

time ( tD>5), the temperature distributi<strong>on</strong><br />

functi<strong>on</strong> TC(r, t,) in the vicinity of the well<br />

can be described by the relati<strong>on</strong>:<br />

where<br />

TC(r,tl) - Tf<br />

In rD<br />

= 1 - - (1)<br />

Tm - Tf In %<br />

R<br />

r<br />

R D = - : rD = -<br />

r<br />

W r"<br />

at 1<br />

= ',2<br />

R is the radius of thermal influence and r is<br />

the radial distance (the vertical coordinate<br />

coincides with the axis of the well). Thus<br />

the dimensi<strong>on</strong>lese temperature in the wellDora<br />

and in formati<strong>on</strong>s at the end of mud circulati<strong>on</strong><br />

(at a given depth) can be expressed as:

I_<br />

OCrDil<br />

- In rD/ln RD: 15 rD 5 RD (2)<br />

I explbx)<br />

dx = Ei(bx)<br />

where<br />

TCD(rD, tal -<br />

TC(r,tl) - Tf<br />

Tm * Tf<br />

"D ' RD<br />

To determine the temperature al<strong>on</strong>g the well<br />

axis T(O,tZ) after circulati<strong>on</strong> of drilling<br />

fluid has ceased, we used the soluti<strong>on</strong> of the<br />

thermal diffusi<strong>on</strong> equati<strong>on</strong> that describes<br />

cooling al<strong>on</strong>g the axis of a cylindrical body<br />

with known initial distributi<strong>on</strong>, placed in an<br />

infinite medium at c<strong>on</strong>stant temperature<br />

(Carslaw and Jaeger<br />

r<br />

,1959).<br />

2<br />

TD(tD,n) = 2p rTCD(,tD) exp(-p 1 d.r (3)<br />

0<br />

where T is a variable of integrati<strong>on</strong>, t2 is<br />

the Bhut-in time (time between the log and<br />

well completi<strong>on</strong>) and<br />

TD(tD,n) =<br />

T(O,tZ) - Tf<br />

=m - *f<br />

wa obtain<br />

I2 =<br />

- axp ( 'PRD L<br />

2P<br />

Where Ei is the<br />

tabulated functi<strong>on</strong>)<br />

12, and TD into Equ<br />

-<br />

Ei(-pRi) - Ei(-p)<br />

4p In RD<br />

exp<strong>on</strong>ential integral (a<br />

Inserting valuas of 11,<br />

ti<strong>on</strong> 4, we obtain:<br />

5<br />

In practice, for deep wells (large tD<br />

and small p) we can assume that:<br />

4ere we asaume that, for deep wells, the<br />

radius of thermal influence is much larger<br />

hhan the well radius and, therefore, the<br />

difference in thermal properties of drilling<br />

muds and formati<strong>on</strong>s can be neglected. By<br />

inserting TCD into Equati<strong>on</strong> 3, we obtain<br />

Introducti<strong>on</strong> of equati<strong>on</strong>s 6 and 7 into<br />

Formula 5 yields:<br />

~(0,t~)<br />

Tm - Tf<br />

D<br />

Ei(- -) + In n - D<br />

- 1<br />

Tt n<br />

"<br />

In tD + 2 In Do<br />

where<br />

4<br />

Dl = 0.5772 + In D = 0.7532<br />

and<br />

I.<br />

1 1<br />

2<br />

-- exp(-p% 1 + - exp(-p)<br />

2P<br />

2P<br />

1 RD<br />

I2 = - - I;exp(-pT 2 ) In TdT<br />

In RD<br />

Integrating by part and using<br />

substituti<strong>on</strong> u = T2, and noting that:<br />

the<br />

If two measured temperatures (T1,T2) are<br />

available for the given depth with t2 = t2*1<br />

and t2 * t2.2, we obtain:<br />

967

where<br />

Finally, the positi<strong>on</strong> of the permafrost<br />

base (hp) is estimated by extrapolati<strong>on</strong><br />

(Figure 1)<br />

Tfl<br />

hp hl --<br />

A<br />

FIELD DATA<br />

i<br />

Thus the well radius and thermal diffusivity<br />

of the formati<strong>on</strong> have no influence <strong>on</strong> Tf, as<br />

the unknown parameter6 T and tD have been<br />

m<br />

eliminated. The quantities rw and a, however,<br />

affect the value of Tf through TI and T2.<br />

We have given the name "two-point''<br />

method to the procedure just described for<br />

determining the natural formati<strong>on</strong> temperature.<br />

In order for this method to be employed,<br />

the temperature logs must be performed<br />

in a well under unsteady-state thermal<br />

c<strong>on</strong>diti<strong>on</strong>s.<br />

The disturbance<br />

I<br />

time at given depth isz<br />

tl = td - th<br />

Where ta is the total drilling time, th is<br />

the period of time needed to reach the given<br />

depth. The values of th can be determined<br />

from drilling records. In our ca6eI the<br />

drilling records were not available and the<br />

following formula was used:<br />

h<br />

tl = td(l - -1 (111<br />

H<br />

where h is the given depth,<br />

vertical depth of the well.<br />

H is the total<br />

To determine the geothermal gradient,<br />

<strong>on</strong>e, should calculate the static formati<strong>on</strong><br />

temperature at two different depths (Figure<br />

1). From formulas 8-11, <strong>on</strong>e obtains:<br />

For h = h2<br />

; Tf = TfZ<br />

Thus the geothermal gradient<br />

A =<br />

Tf2 - Tfl<br />

h2 - hl<br />

ist<br />

Precise temperature measurements taken<br />

in 15 deep wells located in Northern Canada<br />

(Arctic Islands and Mackenzie Delta) were<br />

used to verify the proposed method (Taylor<br />

and Judge 1977: Judge et aL. 1979). The<br />

total depth of the wells (H), drilling time<br />

(td), shut-in time (time between terminati<strong>on</strong><br />

of: drilling and logging) for two temperature<br />

surveys ( t2. and t2 and two randomly<br />

selected depths (hl and h2) are presented in<br />

Table I. The transient temperatures for<br />

depths h = hl and h = hz at shut-in times t2<br />

= tZ.l and t2 = t2. were taken from the<br />

previously menti<strong>on</strong>ed references and are also<br />

presented in Table I. It should be noted<br />

that interpolati<strong>on</strong> was often used to get<br />

values of temperature at the same depth for<br />

two different shut-in times.<br />

DATA PROCESSING AND DISCUSSION<br />

From Formula 11 and Table I (at h .I hl<br />

or h - h2) the parameter tl was calculated<br />

with an IBM PC and program utilizing the Eifuncti<strong>on</strong><br />

for calculati<strong>on</strong> of y in Formula 9.<br />

The formati<strong>on</strong> static temperaturea for two<br />

depths are determined from Formula 8. A<br />

general computer program was prepared to<br />

calcu1ak.e the permafrost thickness from<br />

Formulas 8-13 : The results of the<br />

calculati<strong>on</strong>s are presented in Table 11. The<br />

predicted formati<strong>on</strong> static temperatures<br />

(Tfl1TfZ) for two depths (hlIh2) are also<br />

presented in Table 11. <strong>Permafrost</strong><br />

thicknesses (hp*) obtained from temperature<br />

logs after l<strong>on</strong>g shut-in times (tz*) were<br />

compared to those determined by the "two<br />

point" method (Table 11). Comparis<strong>on</strong><br />

indicates that the proposed "two point"<br />

method can be used to predict the permafrost<br />

thickness with good accuracy. The accuracy<br />

of the suggested method can be improved if<br />

mre than two depths are selected in the<br />

secti<strong>on</strong> of the well below the permafrost. In<br />

Table 111, the values of h are presented for<br />

P<br />

six combinati<strong>on</strong>s of hl and h2 (four depths).<br />

The average value of permafrytit thickness is<br />

276.3 m. If <strong>on</strong>e assumes the exact" value of<br />

permafrost thickness (h *) for this well is<br />

P<br />

259 m as determined by the l<strong>on</strong>g-time method<br />

of Taylor, et a3.. , a (Table II ) then the<br />

proposed short-time method provides a value<br />

968

~ " ~~<br />

with a relative accuracy of 6.5% (compare t2. 2/ta = 158/53 = 3 and the exact value of<br />

with 12%. Table 11). h *, = 259 m is obtained at tZx/td = 31,<br />

P<br />

It should be noted that. in this (Table 11). ft is also clear that the<br />

example, temperature Logs with relatively predicted values of the permafrost thickness<br />

short: shut-in times and drilling time ratios are very dependent <strong>on</strong> the accuracy of the<br />

were used. Indeed, for Well 272 the value Of temperature logs in deep wells (Table 111).<br />

Table I Input data (Taylor and Judge, 1977; Judge, et al.. 1979)<br />

86 3375 240 265 634<br />

155 3925 119 190 431<br />

158 3177 73 82 320<br />

167 4361 179 26 106<br />

168 4000 91 99 491<br />

169 2281 65 104 479<br />

170 1829 28 132 312<br />

175 "_ 3845 -_ .. 145 53 440<br />

1711 3205 94 23 250<br />

192 3689 188 35 321<br />

193 4704 237 16 62<br />

196 ~- 4383 133 41 395<br />

~<br />

272 3305 53 83 158<br />

274 3295 61 60 135<br />

275 3295 116 8 88<br />

355.0<br />

475.0<br />

450.0<br />

152.4<br />

613.0<br />

275.0<br />

381.8<br />

550.0<br />

315.0<br />

149.4<br />

375.0<br />

785.0<br />

335.0<br />

411.2<br />

396.2<br />

350.0<br />

500.0<br />

500.0<br />

213.4<br />

652.6<br />

300.0<br />

427.6<br />

575.0<br />

400 * 0<br />

195.1<br />

400.0<br />

814.7<br />

365.8<br />

456.9<br />

457.2<br />

3.38<br />

4.69<br />

3.33<br />

9.88<br />

3.91<br />

3.84<br />

3.77<br />

9.35<br />

5.15<br />

9.56<br />

7.74<br />

3.49<br />

4.93<br />

4.36<br />

9.24<br />

2.53 4.45<br />

2.97<br />

5.71<br />

I .69<br />

5.98<br />

6.56<br />

11.87<br />

2.42<br />

5.21<br />

2.31<br />

5.21<br />

3.05 6.27 . ._.<br />

3.98 10.13<br />

1.70<br />

5.13<br />

4.27<br />

il.11<br />

5.09<br />

0.52<br />

2.13<br />

4.10<br />

3.43<br />

5.73<br />

2.97 5.96<br />

4.48 11.03<br />

3.67<br />

4.32<br />

4.60<br />

9.07<br />

3.82<br />

3.69<br />

5.45<br />

5.41<br />

2.43<br />

6.04<br />

6.12<br />

2.93<br />

4.33<br />

4.53<br />

6.35<br />

NOTE: Well NO. is the Earth Physics Branch (Department of Energy, Mines and Resources, Ottawa, Canada)<br />

file number used throughaut this paper.<br />

Table11 <strong>Permafrost</strong> thicknesses for 15 Northern Canadian Wells<br />

Well<br />

No.<br />

Tf 1<br />

OC<br />

Tf 2<br />

OC<br />

hP<br />

m<br />

t9,<br />

'd<br />

86 1.78 2.97 288 306 8.7<br />

5.9<br />

155 1-41 3.06 454 445 25<br />

2.0<br />

I58<br />

1 .uil 4.02 433 429 24<br />

0.9<br />

167<br />

3.44 6.47 83 8b 17<br />

3.5<br />

168<br />

1 .Y5 3.38 559 571 28<br />

3.1<br />

169 1.78 3.15 242 256 19 5.5<br />

1 lU<br />

2.64<br />

4.90<br />

330 336 105<br />

1.8<br />

175<br />

2.72<br />

4.18<br />

503 502 18<br />

0.2<br />

I78<br />

O,Y8<br />

1.71<br />

34 1 354 29<br />

3.7<br />

192<br />

2.18<br />

4.12<br />

98 9!l 15<br />

3.2<br />

193<br />

1.21<br />

2.61<br />

353 34 1<br />

I2<br />

3.5<br />

196<br />

1.85<br />

2.68<br />

719<br />

720 14<br />

1.6<br />

272<br />

1.49<br />

2.51<br />

290 2 59<br />

31<br />

12.0<br />

274<br />

1.43<br />

3.09<br />

372<br />

358 26<br />

3.9<br />

275<br />

2.40<br />

4.33<br />

32U 320 10<br />

0.0<br />

NOTE: (a)tj$ is the time becueen drilling completi<strong>on</strong> and latest log.<br />

(b<br />

969

Table 111<br />

Perm laf r ost thickness. I<br />

335.0 365.8 4.93 3.43 5.73<br />

335.0 396.2 4.93<br />

3.43 6.71<br />

335.0 426.7 4.93<br />

3.43<br />

7.71<br />

365.8 396.2 5.73<br />

4.33 6.71<br />

365.8 426.7 5.73<br />

4.33 7.71<br />

396.2 426.7 6.71 5.26 7.71<br />

4.33<br />

5.26<br />

6.13<br />

5.26<br />

6.13<br />

6.13<br />

1.49<br />

1,49<br />

1.49<br />

2.51<br />

2.51<br />

3.38<br />

2.51<br />

3.38<br />

4.09<br />

3.38<br />

4.09<br />

4,09<br />

3-31<br />

3.09<br />

2.84<br />

2.86<br />

2.59<br />

2.33<br />

290.0<br />

286.8<br />

282.5<br />

278.0<br />

268.9<br />

251.4<br />

CONCLUSIONS<br />

A new method for predicting the<br />

permafrost thickness is described. Only two<br />

temperature logs taken at relatively short<br />

shut-in times are needed to apply this<br />

method. Values of <strong>Permafrost</strong> thickness for<br />

15 Northern Canadian wells have been used to<br />

verify the "two point" method. Applicati<strong>on</strong><br />

of the suggested method may reduce the time<br />

and cost of permafrost surveys in Arctic<br />

areas<br />

ACKNOWLEDGMENTS<br />

The author wishes to thank Dr. Robert M.<br />

Caruthers for his valuable suggesti<strong>on</strong>s and<br />

Mr. Cu<strong>on</strong>g T. Nguyen for assistance with the<br />

calculati<strong>on</strong>s e<br />

REFERENCES<br />

Balobaev, V.T., Devyatkin. V.N. and Kutasov.<br />

I.M. (1973). C<strong>on</strong>temporary Geothermal<br />

C<strong>on</strong>diti<strong>on</strong>s of the Existence and Development<br />

of <strong>Permafrost</strong>, In Proceedings of the Sec<strong>on</strong>d<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>,<br />

Yakutek, Soviet C<strong>on</strong>tributian Washingt<strong>on</strong>,<br />

D.C., Nati<strong>on</strong>al Academy of Science, 8-12.<br />

Bullard, E.C. (1947). The Time Necessary for<br />

a Borehole to Attain Temperature<br />

Equilibrium, M<strong>on</strong>. Not. R. hstr<strong>on</strong>. SOC.<br />

Geophys. SuppL. 5. 127-130.<br />

Carslaw, H.C. and Jaeger. J.C. (1959).<br />

C<strong>on</strong>ducti<strong>on</strong> of Heat in Solids, 2nd Editi<strong>on</strong>,<br />

Oxford University Press, L<strong>on</strong>d<strong>on</strong>, 207.<br />

Jaeger, J.C. (1956). C<strong>on</strong>ducti<strong>on</strong> of heat in<br />

an infinite regi<strong>on</strong> bounded internally by a<br />

circular cylinder of a perfect c<strong>on</strong>ductor.<br />

Aust. Y. Phys. 9, 167-169.<br />

Jaeger, J.C. (1961). The Effect of the<br />

Drilling Fluid <strong>on</strong> Temperatures Measured in<br />

Boreholes, J. Geophys. Res. 66, 563-569.<br />

Judge, A.S. (1973) Deep Temperature<br />

Observati<strong>on</strong>s in the Canadian North, In<br />

<strong>Permafrost</strong> - The North American<br />

C<strong>on</strong>tributi<strong>on</strong> to the Sec<strong>on</strong>d <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

C<strong>on</strong>fqrence, Yakutsk, Washingt<strong>on</strong>, D.C.,<br />

Nati<strong>on</strong>al Academy aE Science, 35-40.<br />

Judge, A.S., Taylor, A.E. and BUrqess, M.<br />

(1979)* Canadian Geothermal Data<br />

Collecti<strong>on</strong>--Northern Wells 1977-78,<br />

Geothermal Series Number 11, Earth Physics'<br />

Branch, Energy, Mines, and Reaources,<br />

Ottawa, 187 pp.<br />

Kutasov, I.M., Lyubimova, E.A. and FirBOv.<br />

F.V. (1966). Rate of Recovery Of the<br />

Temperature Field in Wells <strong>on</strong> the Kola<br />

peninsula, in the collecti<strong>on</strong> of papers<br />

"Problemy glubinnogo teplovogo potoka"<br />

(Problems in the Heat Flux at Depth) I<br />

Nauka, Moscow, 74-87.<br />

Kutasov, I.M. (1968). Determinati<strong>on</strong> of Time<br />

Required for the Attainment of Temperature<br />

Equilibrium and Geothermal Gradient in Deep<br />

Boreholes. Freiberger Porechungshefte.<br />

C238, 55-61.<br />

Kutasov, 1.M. (1976). Thermal Parameters of<br />

Wells Drilled in <strong>Permafrost</strong> Regi<strong>on</strong>s, Nedra,<br />

Moscow. 119 pp.<br />

Lachenbruch, A.H. and Brewer , M. C - ( 1959 1.<br />

Dissipati<strong>on</strong> of the Temperature Effect of<br />

Drilling a Well in Arctic Alaska, U.S.<br />

Geol. Surv. Bull. 10834, 74-109.<br />

Lachenbruch. A.H., Sass, J.H., Marshall, B.V.<br />

and Moses, T.H. (1982). <strong>Permafrost</strong>, Heat<br />

Flow and the Geothermal Regime at Prudhoe<br />

Bay Alaska. Journal of Geophysical<br />

<strong>Research</strong>, 87, 9301-9316.<br />

Melnikov, P.I., Balobaev, V.T., Kutasov, 1.M.<br />

and Devyatkin, V.N. (1974). Geothermal<br />

Studies in Central Yakutia, <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

Geology Review. May, 363-368.<br />

Taylor, A.E. and Judge, A.S. (1977).<br />

Canadian Geothermal Data Collecti<strong>on</strong><br />

Northern Wells, 1976-77, Geothermal Series<br />

Number 10 Earth Physics Branch. Energy,<br />

Mines and Resources, Ottawa, 194 pp.<br />

TayLor , A.E., Burgess, M., Judge, A.S. and<br />

Allen, V.S. (1982). Canadian Geothermal<br />

Data Collecti<strong>on</strong>--Northern Wells 1981,<br />

Geothermal Seriea, Number 13, Earth Physics<br />

Branch, Energy, Mines and Resources,<br />

Ottawa, 153 pp.<br />

970

THE USE OF GROUND PROBING RADAR IN THE DESIGN AND MONITORING<br />

OF WATER RETAINING EMBANKMENTS IN PERMAFROST<br />

P.T. Lafleche, A.S. Judge and J.A. Pil<strong>on</strong><br />

Terrain Scienca Divisi<strong>on</strong>, Geological Survey of Canada, Ottawa, Canada<br />

SYNOPSIS<br />

The c<strong>on</strong>structi<strong>on</strong> of frozen earth c<strong>on</strong>tainment dams is becoming an increasingly<br />

important element in the development of northern regi<strong>on</strong>s. The availability of local materials. a<br />

relatively impermeable frozen overburden and naturally low year-round temperatures make the c<strong>on</strong>-,<br />

structi<strong>on</strong> of frozen embankments a cost effective technique in permafrost areas. Several such<br />

structures, however, have suffered failures in the past. The development of an active layer during<br />

the summer seas<strong>on</strong> can degrade a dam's ability to retain water. Additi<strong>on</strong>ally. sub-dam fluid transport<br />

can occur through unfrozen natural topsoil or poor quality bedrock. Degradati<strong>on</strong> of included<br />

ice within the dam fill matrix or topsoil can also result in leakage.<br />

The <strong>Permafrost</strong> <strong>Research</strong> Group has m<strong>on</strong>itored the performance of several naturally frozen earth dams<br />

at the Echo Bay Mines Ltd. Lupin mine, near C<strong>on</strong>twoyto Lake N.W.T. since 1982. The dams are used<br />

to enclose a small watershed which serves a8 a mine-tailings p<strong>on</strong>d. Initial investigati<strong>on</strong>s were<br />

undertaken with the use of thermistor strings in short drillholes. More recently, the use of ground<br />

probing radar (GPR) has been instrumental in c<strong>on</strong>firming and locating possible z<strong>on</strong>es of c<strong>on</strong>tainment<br />

failure within the dams. The ability of GPR to image the subsurface to depths of several tens of<br />

metres is sufficient to resolve the dam structure including voids, sub-dam overburden, bedrock<br />

topography. active layer depth and to discriminate between frozen and unfrozen z<strong>on</strong>es within the<br />

subsurface. The thermal regime of the dams and underlying natural materials will change c<strong>on</strong>siderably<br />

over the initial few years after c<strong>on</strong>structi<strong>on</strong>. Through comparis<strong>on</strong> of the thermal data and<br />

seas<strong>on</strong>al radar profiles a history for such structures has been developed that will be important for<br />

performance evaluati<strong>on</strong> and design of future facilities.<br />

The ground probing radar technique has shown itself to be a viable tool for poet-c<strong>on</strong>structi<strong>on</strong><br />

m<strong>on</strong>itoring. Similarly, radar surveys can aid in pre-c<strong>on</strong>structi<strong>on</strong> site-selecti<strong>on</strong> and in establishing<br />

dam design requirements.<br />

INTRODUCTION<br />

During late June and September 1986 and April were elevated and broadened by the additi<strong>on</strong> of<br />

1987 several around probing radar (GPR) surveys gravelly-sand in 1984.<br />

were undertaken across tailings p<strong>on</strong>d dams at<br />

the Lupin Wine site of Echo Bay Mines Ltd. The<br />

Lupin site is located in the Northwest Territories,<br />

<strong>on</strong> the northwest side of C<strong>on</strong>twoyto Lake.<br />

about 480 km east of Great Bear Lake, The area<br />

is underlain by several hundred metres of permafrost:<br />

over five hundred metres of frozen<br />

ground was intersected in the development of<br />

the mine shaft. The tailing6 disposal p<strong>on</strong>d at<br />

the site (Figure 1) was created by damming a<br />

small watershed to create an enclosed storage \<br />

basin. This basin was designed to hold the<br />

tailings output of the mine for several years.<br />

Decantati<strong>on</strong> into the natural envir<strong>on</strong>ment would<br />

occur after treatment has<br />

reduced the c<strong>on</strong>tami- \<br />

nant c<strong>on</strong>tent to an acceptable level. These j 0 , d<br />

c<strong>on</strong>tainment dams were c<strong>on</strong>structed from locally<br />

x, <br />

sand. Several of the dams were lined with an<br />

impermeable liner. Typically each dam site was<br />

scraped clean of organic material prior to c<strong>on</strong>structi<strong>on</strong><br />

of the dams. The frozen nature of the Fig.1. The Lupin Mine tailing8 facility.<br />

dams and the underlying overburden and bedrock<br />

should preclude any fluid transport through or<br />

beneath the structures. Several of the dams<br />

97 1<br />

.\<br />

\\

Despite the precauti<strong>on</strong>s taken in the design and<br />

c<strong>on</strong>structi<strong>on</strong> of the dams. leakage of tailing6<br />

water has been known to occur during the thaw<br />

seas<strong>on</strong> through or around several of the dams.<br />

The purpose of the GPR surveys was to establish<br />

if a high resoluti<strong>on</strong> geophysical technique, such<br />

as GPR , could detect unfrozen z<strong>on</strong>es (taliks)<br />

within or below the dams and so reveal a picture<br />

of the dam and overburden c<strong>on</strong>diti<strong>on</strong>s. Unfrozen<br />

z<strong>on</strong>es were thought to be the cause of fluid<br />

transport from the tailings p<strong>on</strong>d into the surrounding<br />

envir<strong>on</strong>ment. In additi<strong>on</strong> to the radar<br />

surveys, a ground temperature m<strong>on</strong>itoring program<br />

has been carried out at the site since 1982.<br />

Thermistors are ,installed in boreholeg through<br />

four of the dams. Early temperature measuring<br />

cables suffered failures but reliable ground<br />

temperature data are available from June 1, 1985<br />

to the present date. Temperature data normally<br />

are collected several times per m<strong>on</strong>th.<br />

The ability of GPR to image the ground to 50 m<br />

in some casea allows resoluti<strong>on</strong> of the dam<br />

structures, sub-dam overburden c<strong>on</strong>diti<strong>on</strong>s, bedrock<br />

topography and depth of thaw: and to locate<br />

un€rozen z<strong>on</strong>es (taliks) within the overburden<br />

and uppermost bedrock.<br />

FROZEN CORE CONTAINMENT DAMS<br />

Frozen core c<strong>on</strong>tainment dams have been used<br />

extensively in the Soviet Uni<strong>on</strong> for a number of<br />

years. The main advantage of these structures<br />

is that they are impermeable to fluid flow due<br />

to their frozen nature and ate relatively cheap<br />

to c<strong>on</strong>struct as materials can be found locally.<br />

Typically the structures are built up<strong>on</strong> the<br />

natural Overburden and are less than 50 m in<br />

height [Sayles, 1983). Such dams are maintained<br />

in an impermeable state either by naturally low<br />

local temperatures or through active refrigerati<strong>on</strong><br />

techniques such as the installati<strong>on</strong> of<br />

cold air or liquid refrigerant piping. Several<br />

instances of dam failure have occurred in the<br />

Soviet Uni<strong>on</strong>. These usually involve a small<br />

area of leakage which rapidly expands due to<br />

local melting around the leak site. Causes of<br />

potentia1 leakage are insufficient freezing of<br />

the dam during c<strong>on</strong>structi<strong>on</strong>, degradati<strong>on</strong> of the<br />

dam base due to thermal heating by the retained<br />

fluid which eventually results in a sub-dam<br />

talik, thaw desradati<strong>on</strong> o€ the reservoir side<br />

of the dam embankment. melting arising from h<br />

fluid flows at outlet structures or the creat<br />

of voids within the dam arising from the melt<br />

of large ice pockets inadvertently included<br />

the dam during c<strong>on</strong>structi<strong>on</strong>.<br />

GROUND PROBING RADAR (GPR)<br />

The GPR is a fairly new geophysical tool, the<br />

fjrst models being commercially available in<br />

the mid 1970's. GPR is similar in principle to<br />

the reflecti<strong>on</strong> seismic method in that a pulse<br />

of energy is directed into the ground and the<br />

arrival times of reflecti<strong>on</strong>s from subsurface<br />

interfaces are recorded. The main difference<br />

between the techniques is that radar uses an<br />

electromagnetic as opposed to an acoustic energy<br />

source. Radar possesses a much more limited<br />

depth of penetrati<strong>on</strong> than seismic, typically of<br />

the order of 50 m or less, but provides a s'ignificant<br />

increase in resoluti<strong>on</strong>. Subsurface<br />

resoluti<strong>on</strong> is dependant up<strong>on</strong> the puIse length<br />

and, as such, can be as low as <strong>on</strong>e half a metre.<br />

This high spatial resoluti<strong>on</strong> can be important<br />

in the soluti<strong>on</strong> of complex near surface problems.<br />

GPR has been found to be host usefvl in<br />

engineering geophysical applicati<strong>on</strong>s s.uch as<br />

the delineati<strong>on</strong> of overburden thic'kness, permafrost<br />

extent and depth (LaFleche and Judge.<br />

1987a). water table depth and ice thickness<br />

(Annan and Davis, 1977) or for locating buried<br />

cables, pipes (Morey. 1974). fractures (Olhoeft,<br />

1978). voids (Owen and Suhler. 1980). gravels<br />

(Davis et al.. 1984) and tunnels (Dolphin et<br />

al., 1978).<br />

-.<br />

Radar reflecti<strong>on</strong>s are produced by interfaces<br />

between materials of c<strong>on</strong>trasting electrical<br />

properties. specifically the dielectric permittivity<br />

or electrical c<strong>on</strong>ductivity. Comm<strong>on</strong><br />

causes of subsurface reflecti<strong>on</strong>s are material<br />

interfaces (overburden-rock, gravel-sand), top<br />

of the water table, boundaries between frozen<br />

and unfrozen water, voids, fracturesandice<br />

lenses. Within the radio frequency band, a<br />

large dielectric and c<strong>on</strong>ductivity c<strong>on</strong>trast<br />

exists between water and most natural geologic<br />

materials (Morey, 1974). The ability of a<br />

material to retain water within its pore spaces<br />

is an important factor for the deterrhinati<strong>on</strong> of<br />

its bulk electrical properties. As such. the<br />

presence or absence of water and its chemistry<br />

c<strong>on</strong>trols, to a large degree, the subsurface<br />

propagati<strong>on</strong> characteristics of the radar pulse.<br />

Distinct variati<strong>on</strong>s in grain size or rock<br />

porosity. and the associated changes<br />

in the<br />

volume percentage of retaiped water, will produce<br />

radar reflecti<strong>on</strong>s.<br />

The depth to which a radar pulse will effectively<br />

"penetrate" is dependant up<strong>on</strong> the<br />

electromagnetic absorpti<strong>on</strong> characteristics of<br />

the ground and the amount of energy lost due to<br />

reflecti<strong>on</strong>. refracti<strong>on</strong> and diffracti<strong>on</strong> effects.<br />

In a general sense, the depth of penetrati<strong>on</strong><br />

will decrease with increasing water c<strong>on</strong>tent.<br />

Dry, homogenous or frozen materials will offer<br />

the greatest potential depth penetrati<strong>on</strong>.<br />

The depths to specific reflectors are calculated<br />

from a knowledge of the subsurface radar velocicy<br />

distributi<strong>on</strong>. In air, the radar pulse,<br />

typically in the MHz or GHz frequency range,<br />

travels with the speed of light (0.3 m/ns). In<br />

the ground the pulse travels with a velocity<br />

(typically 10 to 50% of the speed of light)<br />

which is dependent up<strong>on</strong> the electrical properties<br />

of the material traversed. The radar<br />

velocity distributi<strong>on</strong> in the ground can be<br />

determined, as in the case of seismic surveys,<br />

by a comm<strong>on</strong> depth point sounding (CDP).<br />

The low c<strong>on</strong>ductivity and low dielectric losses<br />

of very high frequency (VAF) electromagnetic<br />

wave6 in frozen ground allow c<strong>on</strong>siderable penetrati<strong>on</strong><br />

in permafrost. The extent of taliks<br />

can be mapped a6 the sharp c<strong>on</strong>trasts in c<strong>on</strong>ductivity<br />

and permittivity between frozen and unfrozen<br />

z<strong>on</strong>es result in str<strong>on</strong>g reflecti<strong>on</strong>s from<br />

these boundaries.<br />

972

DAM SITE XNVESTXGATIONS<br />

Two dam sites were initially surveyed in June<br />

of 1986: Dams 2 and J (Figure 1). Dam J was<br />

resurveyed in April of 1987. Both of these dams<br />

currently have or have experienced associated<br />

tailings water seepage. Borehole temperature<br />

data are available for Dam 2. Dam J was Only<br />

recently c<strong>on</strong>structed in 1985, thus <strong>on</strong>ly the<br />

details of the c<strong>on</strong>structi<strong>on</strong> plans are available.<br />

It was built to seal off the primary tailings<br />

p<strong>on</strong>d. P<strong>on</strong>d 1, from the decantati<strong>on</strong> p<strong>on</strong>d, P<strong>on</strong>d<br />

2, shown in Figure 1. P<strong>on</strong>d 2 serves as a temporary<br />

holding basin before decantati<strong>on</strong> into<br />

the envir<strong>on</strong>ment. The water is treated to remove<br />

c<strong>on</strong>taminants during decantati<strong>on</strong> from P<strong>on</strong>d 1 to<br />

P<strong>on</strong>d 2.<br />

A third site, Dam 1A (Figure 1) was surveyed in<br />

late September of 1986 and Ke8UrVeyed in April<br />

of 1987. Borehole temperature readings indicate<br />

that a thaw bulb may exist at depth beneath the<br />

dam.<br />

Dam 2<br />

Dam 2 (Figure 2) was surveyed with the object<br />

of mapping the sub-dam bedrock and overburden<br />

competency. Seepagehad been observed to occur<br />

around the south end of the dam abutment, near<br />

the stati<strong>on</strong> at 310 m <strong>on</strong> the radar profile<br />

(Figure 3). during previous summer seas<strong>on</strong>s.<br />

The core extracted from a drillhole at locati<strong>on</strong><br />

356 m, bey<strong>on</strong>d the end of the profile, had shown<br />

indicari<strong>on</strong> of substantial fracturing through<br />

the first 5 m of bedrock. The source of water<br />

transport was thought to be due to the melting,<br />

during the thaw seas<strong>on</strong>. of ice infilling these<br />

fractures. Temperature data indicate that the<br />

ground temperature could rise as high as O'C<br />

even at 7 m depth during the period of maximum<br />

thaw.<br />

"-1"""-<br />

Fig.2. Cross-secti<strong>on</strong> of Dam 2.<br />

The dam was profiled from north to south using<br />

an A-Cubed fnc. PulseEKKO I11 radar equipped<br />

with 50 MHz antennas. The transmitting and receiving<br />

antennas were separated by 4 m and the<br />

stati<strong>on</strong> spacing was 4 m. The horiz<strong>on</strong>tal axis On<br />

the radar profiles represents the distance al<strong>on</strong>g<br />

the dam, while the vertical axis represents<br />

travel time (nanosec<strong>on</strong>ds) to a particular reflecti<strong>on</strong><br />

event.<br />

The interpretated ground secti<strong>on</strong> is shown in<br />

Figure 3. The velocity (0.11 m/ns). determined<br />

from CDP soundings, can be used to calculate the<br />

depths to reflectors 1. 2 and 3 indicated <strong>on</strong><br />

Fig. 3 (LaFleche et al., 1987b).<br />

973<br />

Fig.3. A 50 MHz radar profile and interpreted<br />

secti<strong>on</strong> for Dam 2 in June of 1986.<br />

Reflector 1 is at a depth of about 2 m appearing<br />

to combine the boundary between the new and old<br />

dam material and the depth of the active layer.<br />

Temperature data from thermistors D-5 and D-6<br />

indicate that the latter should reside between<br />

2 and 3 m. Since both interfaces could be<br />

roughly coincident at this time of year it would<br />

be difficult to resolve them as separate events.<br />

It can however be observed that in many places<br />

reflector 1 is represented by a broad double<br />

pulse indicative of a complex boundary. The new<br />

dam fill which is believed to be gravelly sand<br />

should retain much less moisture than the<br />

original silty sand. Such an interface should<br />

provide a good electrical c<strong>on</strong>trast as indicated<br />

by reflector 1.<br />

Ref lector 2 is at a depth of about 4.2 m and<br />

represents the interface of the silty sand dam<br />

fill with the natural silty sand overburden.<br />

The natural overburden should c<strong>on</strong>tain c<strong>on</strong>siderably<br />

more frozen water than the dam fill resulting<br />

in a str<strong>on</strong>g electrical c<strong>on</strong>trast. The dam<br />

fill material was obtained by drying excavated<br />

natural overburden material to substantially<br />

reduce its water c<strong>on</strong>tent.<br />

Reflector 3 varies c<strong>on</strong>siderably in depth al<strong>on</strong>g<br />

the profile. It represents the top of the bedrock.<br />

A substantial (5 m) dip in the bedrock<br />

topography is observed near the middle of the<br />

dam (at distance al<strong>on</strong>g the profile of 110 to<br />

222 m). prillholes D-6 and D-7 (Figure 3) indicate<br />

bedrock depths of 4.1 and 10.4 m respectively.<br />

The depths calculated at D-6 and D-7<br />

from the radar profile are 5.9 and 9.5 m respectively.<br />

The discrepency arises from an Uncertainty<br />

,of the true Velocity profile. Each layer<br />

of dam fill possesses its own radar velocity<br />

and thickness and these should be taken into<br />

account when calculating the true depth to bedrock.<br />

Str<strong>on</strong>g reflecti<strong>on</strong>s are observed within the bedrock.<br />

These most likely represent included ice<br />

within the phyllite: the ice could be present<br />

either al<strong>on</strong>g cleavage planes or In fractures<br />

and joints, The limit of the reflecti<strong>on</strong>s at<br />

depth (Figure 3) is a functi<strong>on</strong> of several<br />

factors including the gain level, the detecti<strong>on</strong><br />

threshold of the instrument and the absorptive<br />

characteristics of the subsurface materials.<br />

Increasing or decreasing the gain during pro-

cessing will move this apparent boundary either<br />

downward OK upward. The apparent dip in the<br />

base of these reflecti<strong>on</strong>s is an artifact of the<br />

increased thickness of overbucden in the central<br />

area of the dam. The bedrock material should<br />

possess a higher radar velocity than the natural<br />

silty sand overburden: the additi<strong>on</strong> of an increased<br />

thickness of lower velocity material<br />

stretches out the traces in this area yielding<br />

a distorted image of the deep structure.<br />

Dam J<br />

Dam J was surveyed with the object of detecting<br />

a possible area of Beepage through either the<br />

dam itself or its base. The dam was originally<br />

filled ,with run of mill (ROM) material to the<br />

original land surface (Golder Associates,<br />

1986). This means we should not expect to<br />

encounter any layering or large reflectors<br />

within the dam itself. An impermeable sand<br />

liner was placed <strong>on</strong> the upstream side. The ROM<br />

material is relatively permeable and is unable<br />

to SUppOKt a fluid head across the dam for any<br />

period of time. Little permafrost existed<br />

naturally at the site as most of the central<br />

porti<strong>on</strong> of the dam foundati<strong>on</strong> was o~iginally<br />

covered by water in a pre-existing stream bed.<br />

This resulted in the material immediately under<br />

the central porti<strong>on</strong> of the dam being initially<br />

unf cozen.<br />

METRE8<br />

40 e0 83 100 120 id0 Id0 180 200 120<br />

..Ri ..R2 ..e3 +.awIIWI1(1w."C<br />

Fig.4. A 50 MHz radar profile al<strong>on</strong>g Dam J in<br />

June of 1986.<br />

and April of 1987. The transmitter-receiver<br />

separati<strong>on</strong> and the stati<strong>on</strong> spacing were 4 m for<br />

the June 1986 survey and 2 m for the 1987 survey<br />

respectively. A CDP sounding was taken near<br />

the north end of the dam. The radar profiles<br />

over the dam are shown in Figures 4 and 5. CDP<br />

soundings taken in September 1986 and April<br />

1987 indicate that the top layer velocity is<br />

0.14 m/ns.<br />

In the initial survey (Figure 4) the depth of<br />

penetrati<strong>on</strong> of the radar is quite limited over<br />

the dam itself. This is evidenced by the lack<br />

of returns at mid to late times at locati<strong>on</strong>s<br />

40 m to 200 m al<strong>on</strong>g the profile. The high water<br />

c<strong>on</strong>tent and unfrozen nature of the overburden<br />

under Dam J limits the penetrati<strong>on</strong> of the radar<br />

pulse. Note that the rather clean radar traces<br />

directly under Dam J are in direct c<strong>on</strong>trast to<br />

the profile presented under Dam 2 (Figure 3)<br />

where str<strong>on</strong>g reflecti<strong>on</strong>s are indicated to depth,<br />

The traces at either end of Dam Y, that is in<br />

the areas not originally submerged, exhibit the<br />

latter character.<br />

Given these initial survey results, several possible<br />

causes of leakage from P<strong>on</strong>d 1 to P<strong>on</strong>d 2<br />

wer@ envisaged. These are:<br />

1. Leakage could be occurring directly thiough<br />

the rathex thin tailings sand liner.<br />

2. Leakage could be aided by the melting of<br />

lake ice included with the ROM material<br />

during winter dam c<strong>on</strong>structi<strong>on</strong> period.<br />

3. Fluid could be transported through the<br />

natural overburden or lake-bottom base which<br />

seems to be unfrozen.<br />

Subsequently, the dam was widened and raised in<br />

the fall of 1986. The effect of this was to<br />

present a widet surface over which to promote<br />

freezing. The results of the April 1987 survey<br />

(Figure 5) show that radar penetrati<strong>on</strong> has increased<br />

significantly under the dam itself,<br />

suggesting that the ground has frozen c<strong>on</strong>siderably<br />

over the winter of 1986/87. Figure 6 shows.<br />

for comparis<strong>on</strong>, the interpretated secti<strong>on</strong> for<br />

the September 1987 survey. The interface between<br />

the old dam fill and the new fill is<br />

clearly Visible in the radar profile. The base<br />

of the dam can be traced accoss the old river<br />

bed e<br />

Dam 1A<br />

The dam was profiled with the PulseEKKO III Dam 1A was surveyed with the object of mapping<br />

rada-r using the 50 MHz antennas in June of 1986 <strong>on</strong>e or more large unfrozen z<strong>on</strong>es (talik8) which

Fig.6. Interpreted secti<strong>on</strong> for the profile in<br />

Fig. 5.<br />

were thought to exist below the dam's base. A<br />

small stream originally cut across the middle<br />

of the area spanned by the dam. This resulted<br />

in the formati<strong>on</strong> of a small floodplain valley<br />

and possibly year-round unfrozen z<strong>on</strong>es UndeL<br />

the rivet bed. Thermistors were installed in<br />

five drillholes, D1A-1, 10, 11, 12 and 13<br />

(Figure 7). The temperature data fOK drillhole<br />

D1A-13 show that the subsurface remains frozen<br />

below a depth of 4 m year-round. Thermistor<br />

string D1A-1 indicates a potential thaw depth<br />

of 4.3 m. The thermistors in drillholes D1A-11<br />

and D1A-12 indicate that the subsurface material<br />

remains unfrozen down to 10 m during the seas<strong>on</strong><br />

of: maximum thaw and can remain above -2-C down<br />

to at least 24 m depth. The thermistors in<br />

drillhole D1A-10 indicate that the subsurface<br />

can thaw down to about 5 m depth. The tempetature<br />

data thus show the presence of a talik in<br />

the natural overburden beneath the dam at the<br />

positi<strong>on</strong> of thermistor strings D1A-10. D1A-11<br />

and D1A-12. This dam was surveyed using the<br />

100 MHz antennas in September of 1907 in order<br />

to provide the best subsurface resoluti<strong>on</strong>. The<br />

April 1987 survey employed the 50 MHz antennas.<br />

The stati<strong>on</strong> interval was 2 m.<br />

The profile al<strong>on</strong>g the top of the dam shows<br />

str<strong>on</strong>g reflecti<strong>on</strong>s from the interface between<br />

the original silty-sand fill derived from dried<br />

overburden material and the gravel-sand material<br />

used in elevating- the dams. The interface between<br />

the dam fill and the original overburden<br />

is also evident. The bedrock/overburden interface<br />

is not obvioue <strong>on</strong> this profile. The hole6<br />

drilled from the top of the dam, D1A-11. and<br />

D1A-12, indicate that bedrock is at least ten<br />

metres deep. This corresp<strong>on</strong>ds to a minimum of<br />

220 ns in radar pulse travel time.<br />

The profile al<strong>on</strong>q the dam accesB road (Figure<br />

7) shows three str<strong>on</strong>g reflectors (Figure 8).<br />

ReflectOK R1 represents the interface between<br />

the gravelly-sand and dam fill and the original<br />

silty-sand dam fill. Reflector R2 represents<br />

the interface between the dam fill and the<br />

natural overburden. ReflectOK R3 represents<br />

the bedrock interface. Drillhole D1A-10 intersect6<br />

the bedrock at 5.2 m. The depth to bedrock<br />

at D1A-10 as calculated from the radar<br />

profile i6 5.1 m. Drillhole D1A-1 was uniortunately<br />

not logged. The radar profile shows a<br />

pr<strong>on</strong>ounced dip in the bedrock topography between<br />

locati<strong>on</strong>s 130 m and 210 m al<strong>on</strong>g the profile.<br />

This agrees with the drillhole data which indicates<br />

that the bedrock interface is substantially<br />

deeper. below 10 m, at 166 m.<br />

Generally, returns are recorded to depth al<strong>on</strong>g<br />

the length of the profile. Two z<strong>on</strong>es showing<br />

an absence of deeper reflecti<strong>on</strong>s are marked <strong>on</strong><br />

the profile. These are area6 of high electromagnetic<br />

attenuati<strong>on</strong> which are probably<br />

partially<br />

to substantially unfrozen. The absorpti<strong>on</strong><br />

of electromagnetic energy in the central<br />

unfrozen z<strong>on</strong>e has resulted in an extremely weak<br />

reflecti<strong>on</strong> from the bedrock interface between<br />

170 m and 195 m (a6 indicated by the dashed<br />

line). Furthermore the lower radar pulse<br />

velocity associated with this z<strong>on</strong>e has depressed<br />

that porti<strong>on</strong> of the bedrock reflector which is<br />

visible. The bedrock interface thus appears<br />

Fig-7. A 100 MHz radar profile al<strong>on</strong>g the Dam 1A access road in September of 1986.<br />

Two radar profiles were run at this site. <strong>on</strong>e<br />

al<strong>on</strong>g the top of the dam and <strong>on</strong>e at a lower<br />

elevati<strong>on</strong> al<strong>on</strong>g the dam access road c<strong>on</strong>taining<br />

thermistor strings DTA-1 and D1A-10. The latter<br />

profile is shown in Figure 8. Comm<strong>on</strong> depth<br />

point soundings were taken in both cases. The<br />

ground wave velocities at the top of the dam<br />

ana <strong>on</strong> the access road are 0.094 and 0.081 m/ns<br />

respectively. These are quite similar to the<br />

velocity calculated for Dam 2 which is similar<br />

in c<strong>on</strong>structi<strong>on</strong> to Dam 1A.<br />

975<br />

slightly deeper<br />

regi<strong>on</strong>.<br />

than it actually is in this<br />

The central thaw z<strong>on</strong>e corresp<strong>on</strong>ds with<br />

the<br />

stream bed leading out of the original watershed,<br />

suggesting that a talik existed prior to<br />

dam c<strong>on</strong>structi<strong>on</strong>. The top of the z<strong>on</strong>e lies at<br />

a depth of about 5 m. Thawing of the overlying<br />

overburden and dam fill has occurred under<br />

locati<strong>on</strong>s 180 m to 190 m, The bedrock in drill-

hole D1A-11 was found to be highly fractured<br />

and of generally poor quality for the top two<br />

metres. Drillhole D1A-12 intersected poor to<br />

fair quality bedrock down to 15 m. There exists<br />

a potential for fluid transport through the<br />

upper porti<strong>on</strong> of the bedrock as in the case of<br />

Dam 2.<br />

assistance; in particular. Bob Gilroy, Hugh<br />

Wils<strong>on</strong> and Ed W<strong>on</strong>g. The thermal m<strong>on</strong>itoring<br />

program is c<strong>on</strong>ducted under c<strong>on</strong>tract to<br />

EMR-<br />

Canada by Geoc<strong>on</strong> Inc. Funding assistance has<br />

been provided by the Nocthern Envir<strong>on</strong>mental<br />

Directorate of Indian and Northern Affairs<br />

Canada.<br />

Fig.8. Interpreted secti<strong>on</strong> for the profile in<br />

Fig.7.<br />

The more northerly thaw z<strong>on</strong>e corresp<strong>on</strong>ds to the<br />

locati<strong>on</strong> where seepage was observed to occur<br />

immediately after the dam c<strong>on</strong>structi<strong>on</strong> in the<br />

fall of 1981.<br />

CONCLUSION<br />

Frozen earth-Eilled dams and embankments have<br />

c<strong>on</strong>siderable applicati<strong>on</strong> in the permafrost<br />

regi<strong>on</strong>s of the world. The ground probing radar<br />

surveys were able to yield c<strong>on</strong>siderable informati<strong>on</strong><br />

<strong>on</strong> the dam and sub-dam c<strong>on</strong>diti<strong>on</strong>s and<br />

performance. This informati<strong>on</strong> corresp<strong>on</strong>ded well<br />

to the subsurface c<strong>on</strong>diti<strong>on</strong>s as determined by<br />

the dam c<strong>on</strong>structi<strong>on</strong> procedures and subsequent<br />

drill-coring. The radar has also served to<br />

extend our knowledge of the subaurface to areas<br />

where little was previously known. Radar surveys<br />

should be a powerful technique for pre-c<strong>on</strong>structi<strong>on</strong><br />

site investigati<strong>on</strong> and for m<strong>on</strong>itoring both<br />

before and after dam c<strong>on</strong>structi<strong>on</strong>. Problems,<br />

such as those encountered at Dam 2 with the poor<br />

quality of bedtock. could be detected in advance<br />

and designed around in the c<strong>on</strong>structi<strong>on</strong> phase.<br />

Two probable thaw z<strong>on</strong>es under Dam 1A were detected<br />

in the radar profile. These corresp<strong>on</strong>d<br />

well with the existing downhole temperature informati<strong>on</strong>.<br />

Likewise the radar was able to<br />

detect the unfrozen nature of Dam J and Iollow<br />

its freezing Over time. The major advantage of<br />

the radar is that it is able to map the total<br />

extent of the thaw z<strong>on</strong>es between drillholes.<br />

Given the changing ground c<strong>on</strong>diti<strong>on</strong>s associated<br />

with the yearly freeze-thaw cycle, it would be<br />

advantageous to m<strong>on</strong>itor the dam c<strong>on</strong>diti<strong>on</strong>s with<br />

theradarat several times during the year.<br />

This, in c<strong>on</strong>juncti<strong>on</strong> with the <strong>on</strong>-going temperature<br />

m<strong>on</strong>itoring program. would allow us to<br />

determine the nature of any l<strong>on</strong>y term changes<br />

at the site. A combined geophysical and thermal<br />

history of these sites will be important when<br />

c<strong>on</strong>sidering future developments of this type <strong>on</strong><br />

permafrost.<br />

ACKNOWLEDGEMENTS<br />

The authors wish to express their gratitude to<br />

Echo Bay Mines Ltd. €or providing logistic<br />

976<br />

REFEKENCES<br />

Annan, A!, Davis, JL (1977). Impulse radar<br />

applied to ice thickness measurements and fresh<br />

water bathymetry. Geol. Sur. of Can. Paper<br />

77-1B. 63-65.<br />

Davis, JL, Annan, AP, Vaughan, C (1984). Placer<br />

explorati<strong>on</strong> using radar ana seismic methods.<br />

Expanded abstracts of the 54th Ann. Int. S.E.G.<br />

Meeting.<br />

Dolphin, LT, Beaty, WE. Tanzi. JD (1978).<br />

probing of Vitorio Peak, New Mexico.<br />

physics. 43, 1441-1448.<br />

Radar<br />

Geo-<br />

Fowler, JC (1981). Subsurface reflecti<strong>on</strong> profiling<br />

using ground pEobing radar. Mining<br />

Engineering, 33, 1266-1270.<br />

Geoc<strong>on</strong>. Inc. (1986). Interim Data Report No.<br />

40906-1-04, submitted to the Terrain Sciences<br />

Divisi<strong>on</strong>, Geol. Sur. of Can.<br />

Goldet Associates (1986). Draft report <strong>on</strong><br />

tailings impoundment area, C<strong>on</strong>twoyto Lake,<br />

N.W.T., submitted to Echo Bay Mines Ltd.<br />

Kovacs. A, and Morey, RM (1985). Impulse radar<br />

sounding of frozen ground. US Army Corps of<br />

Ens. C.R.R.E.L., Spec. Rep. 85-5. 28-40.<br />

LaFleche, PT, Judge, AS, Taylor, AE (1987a).<br />

Applicati<strong>on</strong>s of geophysical methods to resource<br />

development in northern Canada. CIM Bulletin,<br />

80, 78-87.<br />

LaFleche. PT, Judge, AS, Pil<strong>on</strong>, JA (1987b).<br />

Ground probing radar in the investigati<strong>on</strong> of<br />

the competancy of frozen tailings p<strong>on</strong>d dams.<br />

Current <strong>Research</strong>, Part A, Geol. Sur. of Can.,<br />

Paper 87-1A. 191-197,<br />

MOKey, RM (1974). C<strong>on</strong>tinuous subsurface profiling<br />

by impulse radar: Proceedings of the<br />

Engineering Foundati<strong>on</strong> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> Subsurface<br />

Explorati<strong>on</strong> for Underground Excavati<strong>on</strong> ana Heavy<br />

C<strong>on</strong>structi<strong>on</strong>, Am. SOC. Civ. Eng.<br />

Olhoeft. GR (1978). Surficial mapping and in<br />

situ electrical measurements by impulse radar:<br />

Am. Geophy. Uni<strong>on</strong>. Trans., 59, 1095.<br />

Owen, TE, Suhler. SA (1980). Subsurface Void<br />

detecti<strong>on</strong> using surface resistivity and borehole<br />

electromagnetic techniques: Expanded abstracts<br />

of the 50th Ann. Int. S.E.G. Meeting.<br />

Sayles. FH (1984). Design and performance of<br />

water-retaining embankments in permafrost.<br />

Final Proceedings of the 4th fnt. C<strong>on</strong>f. <strong>Permafrost</strong>.<br />

Fairbanks. Alaska. 31-42.

PEAT FORMATION IN SVALBARD<br />

J. LPg<br />

Agricultural University of Norway, 1432 As-NLH, Norway<br />

SYNOPSIS For a l<strong>on</strong>g time it has been a comm<strong>on</strong> testbook declarati<strong>on</strong> that no peatland exists in<br />

Svalbard. This statement is, however, not quite correct. In Svalbard many moss species occur<br />

which give possibilities fox peat accumulati<strong>on</strong> where the growing c<strong>on</strong>diti<strong>on</strong>s are sufficient. Peat<br />

deposits more than 1.m deep have been found in scattered places. The most remarkable peatlands<br />

occur <strong>on</strong> steep ground. The water released by thawing of the superficial permafrost layer has here<br />

percolated downwards <strong>on</strong> the surface of the still frozen soil, giving bases for a luxuriant growth of<br />

mosses. Peatlands occur in the neighbourhood of Grumantbyen at Isfjorden with a gradient of up to<br />

1: 1.1, and depths of the peat stratum up to 3 m.<br />

INTRODUCTION<br />

The primary c<strong>on</strong>diti<strong>on</strong> for development of peat<br />

is a certain producti<strong>on</strong> of organic material.<br />

Further the decompositi<strong>on</strong> has to go comparatively<br />

slowly. SvaLbard has an extremely cold<br />

climate. <strong>Permafrost</strong> has been registered down<br />

to a depth af 450 m (LiestaL 1977). The rate<br />

of decompositi<strong>on</strong> of humus, under these circumstances,<br />

is of course very slow.<br />

For a l<strong>on</strong>g time it has been a general saying<br />

in textbooks that svalbard has no peatland.<br />

This statement is, however, not quite correct.<br />

Many of the moss species growing here, produce<br />

peat at more southern latitudes. A questi<strong>on</strong><br />

now is where in Svalbard we can find sufficient<br />

growing c<strong>on</strong>diti<strong>on</strong>s for these plants.<br />

According to an internati<strong>on</strong>al definiti<strong>on</strong> the<br />

term peatland is used for areas with a surface<br />

organic layer of at least 30 cm depth.<br />

PEAT FORMATION IN STEEP SLOPES<br />

landscapes slips and Landslides often occur,<br />

giving new cuttings in the soil material.<br />

In the neighbourhood of Grumantbyen a peat<br />

depth of 3 m was measured in 1987.<br />

The water set free by melting of a surface<br />

layer of the soil during summer time moves<br />

downwards <strong>on</strong> the surface of the permafrost in<br />

sloping areas. This moving water is as a rule<br />

favourable for the vegetati<strong>on</strong> owink to a<br />

relatively large c<strong>on</strong>tent of oxygen and nutrients.<br />

In slopes with a good local climate, and<br />

with an extra supply of nutrients from dropping<br />

of sea birds, the growing c<strong>on</strong>diti<strong>on</strong>s can be<br />

especially advantageous. After systematically<br />

searcing for such localities, peat deposits<br />

were found in steep slopes between the outlet<br />

of BjQrndalen river and Grumantbyen at Isfjorden.<br />

In the years 1977-1979 investigati<strong>on</strong>s<br />

were carried out. Depth up to 1.1 m, and<br />

gradient up to 1:l.l Were noted (Lbg 19801.<br />

The study of such curious peatlands has been<br />

c<strong>on</strong>tinued. Because the heat c<strong>on</strong>ductivity power<br />

is Low in the thawed peat, this layer is<br />

shallow, and the measurement of the total peat<br />

depth is not easy. However, in these<br />

Fig. 1. A newly exposed peat wall, due to a<br />

small landslide, NE of Grumantbyen, Spitsbergen.<br />

mto J. Llg, 01.oa.19a7.<br />

In several other places peat with a steep<br />

surface has been found. At Sassenfjorden, in a<br />

slope to the northeast of Fredheim, I have<br />

measured peat depth of a littie more than 1 m.<br />

In many places, e.g. at Recherfjorden, Vdrsolbukta,<br />

Hornsund, and Skansen peat with a depth<br />

of 0.3-0.6 m has been discovered.<br />

There is no reas<strong>on</strong> to assume that peat formati<strong>on</strong><br />

in steep slopes occurs <strong>on</strong>ly in Svalbard.<br />

similar natural c<strong>on</strong>diti<strong>on</strong>s can be found in other<br />

places in the permafrost regi<strong>on</strong>s. Under a short<br />

977

stay in Greenland f have noticed such phenomena in Nordenskialds Land. An age determinati<strong>on</strong><br />

there (LAg 1981). A Canadian lady, Catherine showed approximately 4500 years B.P.<br />

LaFarge-England, has in a private letter dated<br />

09.06.1987, told that she has found 4 m deep Mires with depths of peat less than 30 cm a m<br />

pegt, sloping 34', in Ellesmere Island, around of coufce quite comm<strong>on</strong> (see e.g. Eurola 1971,<br />

82 N.<br />

Plichta 1977).<br />

PEATLANDS WITH NEARLY HORIZONTAL SURFACE<br />

Scattered small peatlands are not seldom.<br />

The Swede Nathorst (1910) tells that in 1882 he<br />

discovered peat with a depth of 2 m in Kapp<br />

Thords<strong>on</strong> Peninsula. He menti<strong>on</strong>s 4 other places<br />

where he has seen peat., and says that such soil<br />

material is not seldom in Spitsbergen. At last<br />

he quotes the opini<strong>on</strong> of another Swede (Gunnar<br />

Anderss<strong>on</strong>) that peat formati<strong>on</strong> is not going <strong>on</strong><br />

any l<strong>on</strong>ger here, and c<strong>on</strong>sequently that the<br />

deposits menti<strong>on</strong>ed are relics.<br />

In Sauridalen, Kapp Thordsen, I have seen a<br />

2 m deep peat deposit at the eastern side of<br />

the river. This seems to be the locality<br />

reported by Nathorst, (He used the name<br />

Renntier-Tal.) The surface was nearly horiz<strong>on</strong>tal<br />

and had a luxuriant growing moss carpet.<br />

The publicati<strong>on</strong> of Nathorst seems to be unknown<br />

for most of the scientists studying soil<br />

c<strong>on</strong>diti<strong>on</strong>s in Svalbard.<br />

In the Midterhuken area well decomposed peat NEW REPORTS ON PEAT DEPOSITS IN SVALBARD<br />

rich in nitrogen occurs (LBg 1980). Mventdalen<br />

has peat deposits (LZig 1979, Gottlich E. When I had discovered the curious peat deposits<br />

Hornburg 1982). The last menti<strong>on</strong>ed authors<br />

in steep slopes, I asked scientists who use to<br />

have performed an age determinati<strong>on</strong>, showing travel in the Svalbard regi<strong>on</strong> to look for such<br />

the result 4615 'I 45 years. Serebryannyy et al. deposits. Three employees at the Norwegian<br />

(1985) have described a 1.7 rn thick peat layer Polar <strong>Research</strong> Institute (T. Siggerud,<br />

978

0. Salviqsen, and T.S. Winsnes) have told about<br />

small peatland areas in Karl XI1 Islands and<br />

Herman's Island. Mr. Asbjdrn Berset has lqer<br />

visited Karl XI1 Islands situated around 80<br />

40'N, and observed peat deposits both there<br />

and in the near Bxoch's Island. So far I have<br />

not had the opportunity to visit these places.<br />

REFERENCES<br />

Eurola, S. ( 1971). The middle artic mire<br />

vegetat .i<strong>on</strong> in Spitsbergen. Acta Agral.<br />

Fennica . 123, 87-107.<br />

Gottlich. K. & Hornburg, P. (1982). Ein Zeuge<br />

warmeze iitlicher Moore in Adventdalen auf<br />

Spitzbergen (Svalbard-Archipel).<br />

Telma. 12, 253-260.<br />

Liestdl, 0. (1977). -Pingos, springs, and<br />

permafrost in Spitsbergen. Norsk palarinstitutt.<br />

Arbok 1975, 7-29.<br />

LAg, J. (1979). Litt om jordbunnsfosholdene pH<br />

Svalbard. (English summary.<br />

Jord og Myr. 3, 99-110.<br />

Lbg, J. (1980). Special peat formati<strong>on</strong> in<br />

Svalbard. Acta Agric. Scand. 30, 205-210.<br />

Lhg, J. (1981). Humus accumulati<strong>on</strong> In steep<br />

slopes at the inner part of Sandre StrQmfjord,<br />

Greenland. Acta Agric. Scand. 31,<br />

242-244.<br />

Nathorst, A.G. (1910). Beitrage zur Geologie<br />

der Biiren-Insel, Spitzberqens una des<br />

K8nig-Karl-Landes. Bull. Geol. Inst.....<br />

Uppsala. 10, 261-415.<br />

Plichta, W. (1977). Systematics of soils Of<br />

the Hornsund regi<strong>on</strong> West Spitsbergen.<br />

Acta Universitatis Nicolai Copernici.<br />

Geografia. 13, 175-180.<br />

Serebryannyy, L.P., Tishkov, A.A,, Malyasova,<br />

Ye. S., Solomina, O.N. & IL'ves, E.O.<br />

(1985). Rec<strong>on</strong>structi<strong>on</strong> of the development<br />

of vegetati<strong>on</strong> in arctic high latitudes.<br />

Polar Geography and Geology. 9, 308-320.<br />

979

PERMAFROST GEOPHYSICAL INVESTIGATION AT THE NEW AIRPORT<br />

SITE OF KANGIQSUALUJJUAQ, NORTHERN QUEBEC, CANADA<br />

M.-K. Seguin, E. Gahe, M. Allard and K. Ben-Mikoud<br />

Centre D'etudes Nordiques, Cite Universitaire, Quebec, GIK 7P4 UniversitC Lava!, Canada<br />

SYNOPSIS The study area is located in the southeastern part of Ungava Bay. The airport site lies in a valley<br />

oriented: NW-SE, flanked by steep bedrock ridges partly filled with glacial and marine deposits. Recent governmental<br />

policy required the c<strong>on</strong>structi<strong>on</strong> of new airports for Inuitian communities of northern Quebec. C<strong>on</strong>structi<strong>on</strong> in a<br />

c<strong>on</strong>tinuous permafrost envir<strong>on</strong>ment requires knowledge of active layer thicknesses as well as lateral and vertical d<br />

tributiorl of permafrost, bedrock topography and groundwater regime. With these objectives in mind, five geophysical<br />

methods were used to investigate the spatial dlstributi<strong>on</strong> of permafrost <strong>on</strong> the airport site. Four methods (electrical<br />

resistivity, induced polarizati<strong>on</strong>, electromagnetism and refracti<strong>on</strong> seismic) were useful to determine the of thickness<br />

the active layer and permafrost and three others (electrical resistivity, refracti<strong>on</strong> seismic and gravimetric) to d<br />

neate bedrock topography. Combining the geophysical data, the following results were obtained. The thickness of the<br />

active layer ranges from 0.5 to 2.8 m (mean: 1.2), that of permafrost from 1.5 to 20 m (mean: 8), that of the unfrozen<br />

layer beneath permafrost 3 to 52 m (mean: 15) and the depth to bedrock from 9 to 66 m (mean: 27). The permafrost underlies<br />

40% of the study area. The physical properties (electrical resistivity, chargeability and density) are Obtained<br />

for different geological units.<br />

INTRODUCTION<br />

The investigated site is located some 160 km northeast<br />

of Kuuiiuaq at l<strong>on</strong>gitude 66OW and latitude 58°30*N (Fig.1)<br />

SO0-<br />

980

Picture sfill made more complex by the disc<strong>on</strong>tinuous na- are located outside the current'electrode pair. The exture<br />

of permafrost. Topography, drainage partern. vege- panding spread is an integer number of the c<strong>on</strong>stant sepatati<strong>on</strong><br />

and climatic c<strong>on</strong>diti<strong>on</strong>s are described by Ben- rati<strong>on</strong> of the electrode pairs. Pseudo-secti<strong>on</strong> plots of<br />

Miloud and Seguin (1987). The fine-grained sediments are apparent chargeabilities which are a measure of the undispersed<br />

<strong>on</strong> the site but are not always visible On sur- derground induced currents and apparent resistivities<br />

face. Four mnin types of surficial deposits are observed lead to the recogniti<strong>on</strong> of soil layers characterized by<br />

in the valley: typical marine deposits of variable grain differing electrical properties wlth depth.<br />

sire and compositi<strong>on</strong>, terrestrial deposits (peat) <strong>on</strong> palsa<br />

plateaus and fens, a S shaped glacial marine shoreline<br />

and a silty clay permafrost mound. Mean annual air The electromagnetic method works <strong>on</strong> the principle that<br />

temperature of the nearby village is -5.6'.<br />

the magnetic comp<strong>on</strong>ent of an electromagnetic wave penetrating<br />

the ground induces sec<strong>on</strong>dary currents in c<strong>on</strong>ducting<br />

bodies. The currents cause a sec<strong>on</strong>dary magnetic<br />

Many different aspects were c<strong>on</strong>sidered in the c<strong>on</strong>struc- field which is detected <strong>on</strong> surface. Using multiple sepati<strong>on</strong><br />

of the airport (Lupien et al., 1984). The main rati<strong>on</strong>s: emitter-receiver and multiple frequencies of<br />

objective wag to minimize the impact of permfrost occur- emissi<strong>on</strong>, the space field distributi<strong>on</strong> measured <strong>on</strong> surfarence<br />

at the site. Hence, a knowledge of the active ce yields informati<strong>on</strong> <strong>on</strong> the geometry and nature of the<br />

layer thickness, lateral and vertical distributi<strong>on</strong> of<br />

c<strong>on</strong>ductors at depth. The apparent c<strong>on</strong>ductivities measured<br />

permafrost, bedrock topography, groundwater regime, local provide some indicati<strong>on</strong>s <strong>on</strong> the distributi<strong>on</strong> of permastratigraphy<br />

of the unc<strong>on</strong>solidated sediments is needed. frost at depth (Annan and Davis, 1976). The seismic re-<br />

To achieve these goals, geomorphological investigati<strong>on</strong><br />

fracti<strong>on</strong> (SR) method is also used to detect underground<br />

and mapping of surficial deposits, drainage pattern and layers which are characterized by their specific seismic<br />

vegetati<strong>on</strong> covqr were first undertaken (Gahi. 1988). velocities. In order to detect the refracted wave <strong>on</strong><br />

A detailed study of the surficial sediments <strong>on</strong> the air- surface, an increase o€ velocity with depth is required.<br />

port site was carried out in 1986 and 1987 by Ben-Miloud Seismic refracti<strong>on</strong> can locate precisely the active layer<br />

and Seguin (1987) and is illustrated in Figure 3. Geo- but is unable to determine the base of permafrost due to<br />

physical applicati<strong>on</strong>s to permafrost problems <strong>on</strong> airport<br />

a velocity inversi<strong>on</strong>. After correcting for the hidden<br />

sites are scarce. Kawaski et al. (1983) menti<strong>on</strong> briefly (low velocity) layers the depth to bedrock can be estlmathe<br />

use of geophysical methods <strong>on</strong> permafrost airport si- ted. In the past, the SR method was used with success<br />

tes in Alaska. to determine the permafrost extent (Roethlisberger, 1961)<br />

SCALE<br />

sR*p<br />

omao e-<br />

Fie. 3- Detailed geomorpholqgical map of the Ungiqsualuj juaq valley including the locati<strong>on</strong> of the<br />

future airport site and geophysical surveys<br />

Four geophysical methods were used to delineate the boundartes<br />

of permafrost: 1) electrical resistivity. soundings<br />

(ERS) with a Schlumberger array, 2) induced polerizatl<strong>on</strong><br />

(IP) in the dipole-dipole c<strong>on</strong>figurati<strong>on</strong>, 3) e-<br />

lectromagnetic (EM) soundings, and 4) seismic refracti<strong>on</strong><br />

(SR). EBS were used for permafrost investigati<strong>on</strong>s in the<br />

1940s (Dostovalov, 1947, Ananyan, 1950, Akinov, 1951).<br />

The current is circulated in the ground wlth two electrodes<br />

and the potential measured with two others. A graph<br />

of the apparent resistivity ys the half separati<strong>on</strong> of<br />

the expanding current electrodes allows a quantitative<br />

interpreee&i<strong>on</strong> of the layered media with depth. In the<br />

IP method, a current is also injected in the ground<br />

with current electrodes, but in additi<strong>on</strong> to the primary<br />

potential, a sec<strong>on</strong>dary potential drop resulting from<br />

induced currents is.measured as a functi<strong>on</strong> of time.<br />

Until recently, the fP method has not been used c<strong>on</strong>m<strong>on</strong>ly<br />

for permafrost mapping (Brown et al., 1985). When using<br />

a dipole-dipole c<strong>on</strong>figurati<strong>on</strong>, the potential electrodes<br />

981<br />

Finally, gravimetry was used as a complementary technique<br />

to estimate the depth to bedrock c<strong>on</strong>sidering the large<br />

density c<strong>on</strong>trast between the soils (1.92 g cK3) and bedrock<br />

units (2.65 g cm-3). The integrated geophysical results<br />

provide a two dimensi<strong>on</strong>al and occasi<strong>on</strong>ally three<br />

dimensi<strong>on</strong>al picture of permafrost masses characterized<br />

by a variable ice c<strong>on</strong>tent as well as taliks. In this<br />

manner, the top and base of permafrost are accurately<br />

outlined underneath the planned airport site. All the<br />

specificati<strong>on</strong>s to the geophysical equipment uBed are '<br />

shown in Table 1.<br />

DEPTH OF THE THAWING FRONT<br />

Some 52 soundings (mainly trenches) were carried out in<br />

July 1983 <strong>on</strong> diferent types of deposits using manual and<br />

motorized methods (Lupien et al., 1984) to determine the<br />

thaw depth (Table 2). 10 soundings were made at 120 m

500<br />

TABLE 1<br />

IiEWPwVSlUL IWSTRUIEYTATIOII USED<br />

ELECTRICAL RESlPllVlfT IYWCEO PCtIlUflDW ELECTRRUQYET(IIETRY SEISMIC REFRACTIOW<br />

Aeslrtfvlty Iter: ABEM dlpitml US 300<br />

rr-y<br />

m 4 nr<br />

Chnractmricr: the rnirter circulatn I<br />

pre.ne1oct.d currmt (0.2 to ZO II A) wd<br />

thm rKolYCr c0rpl.d to m mfcwrocnror<br />

mwWJru tha voltape {* or - 1 or f V).<br />

lhe mlcroprocnror e<strong>on</strong>troln the m<strong>on</strong>wc.<br />

m 8 h-d cnltulmtn WtartlcIlly sol1<br />

rrslrturrF (Ra VII) *lch mn trm.<br />

f o d digltmlly In W,nor Hi. ThR<br />

el~ttrlenl rtriat<strong>on</strong>cr Is red dlrmetly.<br />

ECLG bamtrics (del ES.1225)<br />

Yfth 12 chsmoh. R.cord tim:<br />

5 - 2000 m. Record sixe: I bits<br />

bv 1000 swld pints for mech<br />

ch-1. Dmlay ttm: 0.50 e in<br />

fncrmte of 1 ms. 1-t 1-c.<br />

dust: D ODOll . Frwncy<br />

ruprmt: 1.1000 Hz; pw wly:<br />

11.14 WC; uxtnrm nutplt rlml:<br />

0.35 V; prewlifler prln: 33 e;<br />

aqaHfltr saln: 0.6, 12 ..A &.<br />

TABLE 2<br />

Active layer (At) thickness determined by<br />

mechanical soundings<br />

GEOPHYSICAL DETERMINATION OF ACTIVE LAYER AND PERMAFROST<br />

EXTENT<br />

-<br />

a- Electrical resistivity soundings (EPS)<br />

Site no. soun- AI thik- w.t. depth W.C. soil type<br />

dings ness<br />

47 EBS measurements were carried out <strong>on</strong> the airstrip si-<br />

(d (m) (X)<br />

te. The interpretati<strong>on</strong> of the EBS results is carried<br />

A 28 0.3-1.8 31.7 4.6-24.8 ~g + b<br />

out with the help of master curves (Compagnie Ginirale<br />

de Ghophysique, 1955, 1963, The Rijkswaterstaat. 1969,<br />

B 2 0.7-1.2 0.3-0.6 12-31.2 ss Seguin and Allard, 1984a, b) or by inversi<strong>on</strong> techntques<br />

using a computer program (Zohdp, 1975). Active layer<br />

C 2 0.3-0.6 0-2-0.4 14.4-16.8 Sg<br />

thicknesses determined with the ERS range from 0.5 to<br />

2.8 ut (average: 1.2 m) as ccmpared with 0.3 to 3'm with<br />

D 2 0.7-1.1 1.5-1.8 11.1-33.3 ss<br />

the mechanical soundings. In the active layer. the corresp<strong>on</strong>ding<br />

resistivity values vary from 400 to 40 OOOQ<br />

e 4 1.5-1-8 0-6-1.1 15-7-19.7 5s + Sg -m (average: 10 000). According to Lupien et aL (1984)<br />

the variati<strong>on</strong> in the thickness is related to the grain<br />

F 1 >3 >3 14.2-26-9 ~g size, the finer grained sediments having smaller thaw<br />

G 9<br />

fr<strong>on</strong>t depths (Table 2). The thermal properties (c<strong>on</strong>duc-<br />

1.5->3 33 1.4-20.4 sg + b tivity) is..apparenCly a functi<strong>on</strong> of grain size. A com-<br />

H<br />

paris<strong>on</strong> of the individual thaw fr<strong>on</strong>t depths obtained with<br />

3 1.643 "<br />

-<br />

2.8 sg mechanical and ER soundings is generally good c<strong>on</strong>sidering<br />

52<br />

the fact that the measurements were at slightly different<br />

A= airstrip, E- apr<strong>on</strong> and surrounding roads, periods of time and that local Variati<strong>on</strong>s of terrain c<strong>on</strong>-<br />

C= buildings, O= communicati<strong>on</strong> tower, E= antenna diti<strong>on</strong>s ought to be c<strong>on</strong>sidered.<br />

tower, F= meteorological stati<strong>on</strong>, G= gravel pit,<br />

lb access road, sg= sand and gravel, ss= silty sand,<br />

The ERS investigati<strong>on</strong> has indicated that the,permafrost<br />

b= blocks, w.t.= water table, w.c.= water c<strong>on</strong>tent is thicker when the sediments are finer grained. The<br />

permafrost thickness is 11.5 m in areas overlain by a<br />

spacings al<strong>on</strong>g the central line of the airstrip and 18 peat cover. It is 15 m or more underneath a clayey silt<br />

others al<strong>on</strong>g two parallel lines located at a distance of permafrost mound. The values of ER are located in the<br />

30 m <strong>on</strong> each side. The depth of the soundings varied range 35 000 - 150 000 (average 58 000n-m) for these<br />

between 0.6 and 3 m, some of them reached the thaw fr<strong>on</strong>t different types of terrain. In additi<strong>on</strong> to the detemiwhile<br />

others were hampered by the presence of boulders<br />

nati<strong>on</strong> of the active layer and permafrost thickness, the<br />

or the collapse of the walls caused by a neat surface<br />

depth to bedrock and the stratigraphy of the unc<strong>on</strong>solidawater<br />

table. The number of soundings, the thaw depth, ted deposits are also assessed (Seguin, 1974, 1976,<br />

the water table depth, the gravimetric water c<strong>on</strong>tent and Seguin and Allard, 1987, Cah6 et al., 1987).<br />

the soil type for the sectors c<strong>on</strong>sidered are shown in<br />

Table 2. The general stratigraphical setting is known<br />

from surficial geology mapping of the broader surrounding An example is shown in fine-grained sediments. The ERS<br />

regi<strong>on</strong>, including secti<strong>on</strong>s in a nearby gravel pit and in curve (Pig. 4b) shows the stratigraphy obtained through<br />

sea cliffs. The ground layers detected by the geophysi- its interpretati<strong>on</strong>. Prom bottom to top, it is the folcal<br />

methods generally coincide with this regi<strong>on</strong>al knowled- lowing: 1) depth to bedrock (53 m), 2) unfrozen sedi-<br />

Be - ments (mainly saturated clayey silt) from 53 to 13 m,<br />

3) similar sediments but frozen (13-1m), and 4) thaw<br />

fr<strong>on</strong>t depth of approximately 1 m. Coring has shown that<br />

the ice is lenticular in such materials. A sec<strong>on</strong>d exanple<br />

is selected adjacent to a raised marine shoreline and<br />

982

_I<br />

. -<br />

oriented Deroendicular to the three main lines On which<br />

mechanical soundings were performed (Pig. 4a), i.e. per-<br />

Dendicular to the airstrip axis. The ERS indicates the<br />

presence of a 2.5-thick unfrozen surface layer with a<br />

corresp<strong>on</strong>ding ER value to 5 000 Q-m. This thickness is<br />

1 to 2 times larger than in clayey silt of the mounds <strong>on</strong><br />

the peat plateaus. The higher thermal c<strong>on</strong>ductivity Of<br />

sand and gravel mainly explains this difference. The<br />

permafrost thickness <strong>on</strong> this last site is about 10 m<br />

with an ER value of 90 000 P-m. The ER c<strong>on</strong>trast: active<br />

layer-permafrost 1:18. The is texture of the ice in this<br />

tvpe of materials is intergranular.<br />

INDUCED POLARIZATION<br />

I+ 110 600 Ul0 IPO6W O M 654 660 1M 110 6M 100 TK) 710 mor<br />

I l l l t I I I l I I I I J '<br />

...<br />

I 11m1<br />

c_<br />

4 I 12.Ph<br />

I 1 1 1 1 ~ 1 1 1 1 1 ~ 1 1<br />

HORIZONTAL DISTANCE (m)<br />

I<br />

. .<br />

I) IWREMT CkbIBLAOILITV lM@(dI<br />

I I I I I 1 1 1 1 1 1 1 1 1 1<br />

Fig. 5- Electrical resistivity and chargeability pseudosecti<strong>on</strong>s<br />

<strong>on</strong> a porti<strong>on</strong> of the central line of<br />

the planned airport. The dashed lines indicate<br />

Pig. 4- Typical electrical resistivity soundings: a) in<br />

fine-grained sediments, b) in coarse-grained<br />

the outline of permafrost. The abscissa represents<br />

the horiz<strong>on</strong>tal distance al<strong>on</strong>g the center<br />

line of the projected airstrip (in m) and the<br />

double ordinates the dipole-dipole spread integer<br />

(m) and the depth of investigati<strong>on</strong> (,HI in<br />

sediments. The diagrams show the apparent re-<br />

metres respectively.<br />

sistivity (in ordinate) ~s half current electrode<br />

Separati<strong>on</strong> (in abscissa). The interpreted ."- 2"" -e _"" f<br />

stratigraphy and the corresp<strong>on</strong>ding true electrirost<br />

base varies fr I .2 to 13 m al<strong>on</strong>g<br />

urprp cnL pernrsr'<br />

cal resistivities are indicated in parallel to<br />

most of the profile except for stati<strong>on</strong>s 5 + 620 and 6 +<br />

the abscissa.<br />

630 where it is clot 3er to 10 m (Fig. 5). On both apparent<br />

resistivity ant 1 chargeability dipole-dipole pseudo-<br />

3f<br />

b- Induced polarizati<strong>on</strong> (IP)<br />

secti<strong>on</strong>s. the base I the permafrost is irregular rather<br />

than subhoriz<strong>on</strong>tal a and the chargeabilities yield a some-<br />

When making use of the dipole-dipole c<strong>on</strong>figurati<strong>on</strong> with<br />

what thicker estimal te for the thickness of permafrost<br />

the IP surveys, the depth to the base of permafrost is<br />

than the resistivit: Les. Finally, chargeability values<br />

obtained by calibrati<strong>on</strong> of the depth separati<strong>on</strong>s <strong>on</strong> the are apparently less sensitive to lateral heterogeneities<br />

pseudo-secti<strong>on</strong>s into realistic depths which are obtained the than e:<br />

tectrical resistivittes.<br />

by comparis<strong>on</strong> with those obtained by ER soundings at the<br />

same localities or using formulas for depth calculati<strong>on</strong>s<br />

which are characteristic of each c<strong>on</strong>figurati<strong>on</strong> used (Roy In sunnnary, the IP method was very useful to determine the<br />

... I.<br />

and Appatao, 1971, Roy, 1972, Edwards,-1977, Apparao and<br />

tntc~~nees 01 the active layer, the lateral and vertical<br />

Satma, 1971). For this sec<strong>on</strong>d type of calibrati<strong>on</strong>, the extent of permafrost, the stratigraphy and the degree<br />

integer E which corresp<strong>on</strong>ds to the expanding spread in of heterogeneity of the soils.<br />

the dipole-dipole c<strong>on</strong>figurati<strong>on</strong> is used to obtain the<br />

depth of investigati<strong>on</strong>. The pseudo-secti<strong>on</strong>s (Fig. 5)<br />

show a variati<strong>on</strong> of permafrost thickness al<strong>on</strong>g a 150 m<br />

l<strong>on</strong>g transect <strong>on</strong> the central line of the airport. In the<br />

pseudo-secti<strong>on</strong>, the point of investigati<strong>on</strong> is located<br />

The depths of invest . . ".. ,_.I .,\ ~ ~ ~~<br />

clgatl<strong>on</strong> . ' uslng nn (>+>I surveys are<br />

midway between the internal current and potential electro- a functi<strong>on</strong> frequ4 . ancy as well as separati<strong>on</strong> and c<strong>on</strong>fi-<br />

.. c Of _.<br />

pect to the horiz<strong>on</strong>tal) issued from the surface positi<strong>on</strong> nea. lnls 1s aue CI<br />

of the two internal electrodes. The KB pseudo-secti<strong>on</strong> ti<strong>on</strong>s and frequencil as used and the difficulties ofcalcushow<br />

an irregularity at the base of permafrost which is lating the penetrat: i<strong>on</strong> depth of the signal. With a codetermined<br />

by taking into account the resistivity c<strong>on</strong>-<br />

planar vertical c<strong>on</strong>! Eigurati<strong>on</strong> and coils separati<strong>on</strong>s of<br />

trast; the steepest gradient of apparent resistivity c<strong>on</strong>- lo* and 40 mp th' a maximum depths of penetrati<strong>on</strong> are<br />

tour lines outline the boundary between frozen and unfro- 7.5' l5 and 30 re'<br />

spectively. The estimati<strong>on</strong> of permazen<br />

terrain. The IP pseudo-secti<strong>on</strong> shows three z<strong>on</strong>es of frost thickness is I based <strong>on</strong> c<strong>on</strong>ductivity c<strong>on</strong>trasts bet-<br />

' low steep chargeability (A, B and C). Z<strong>on</strong>e A is located<br />

ween frozen and unf~ roeen z<strong>on</strong>es. Accordingly, a decrease.<br />

at the end of line CL and the informati<strong>on</strong> is insufficient in c<strong>on</strong>ductivity (' ' to 4.5 mnhos fi") between stati<strong>on</strong>s<br />

to arrive at a satisfactory interpretati<strong>on</strong>. Z<strong>on</strong>e C <strong>on</strong> 5 + m3 and 5 + 160 1 (Fig. 6) indicates that permafrost is<br />

the chargeability pseudo-secti<strong>on</strong> corresp<strong>on</strong>ds exactly to thicker (over 15 m) than iqthe interval: 5 + 160 to<br />

..<br />

the same z<strong>on</strong>e <strong>on</strong> the resistivity pseudo-secti<strong>on</strong>. Z<strong>on</strong>es 5 + 280 where it is estimated betweer I 1.5 and 15 m. For<br />

B and C may be explained by two phenomena: 1) taliks<br />

instance, at statio1 1 > + L" ow (rig. '" o), L' the c<strong>on</strong>ductivity<br />

in sand or 2) frozen silty or clayey silt lenses, The values for the three separat i<strong>on</strong>s are 4.5, 2.5 and 3.3<br />

mhos m.-l. m.. A"-" _._<br />

last explanati<strong>on</strong> is more probable because permafrost in<br />

&ne aecrease in c<strong>on</strong>ductivity from 4.5 to 2.5<br />

clayey silt mounds was observed nearby the airstrip site.<br />

. by the occurrence of a permafrost<br />

983<br />

nnnhos ,-' is

SRE:86-7-IB-SA<br />

LEGEND<br />

Actlve layor In wet sand 8 g m<br />

0 PMF In wet sand 8 gravol<br />

. ". -<br />

Wet sand and grovel<br />

c<br />

SRz86-7-1-2<br />

Hammer ~ourco<br />

40<br />

/<br />

V3=5000 mi'<br />

351<br />

AW2 (rn 1<br />

n\<br />

2 12 22 31 42 52 62 72 8292 102 112 I22<br />

Dry sand +grovd<br />

SR:86-7-2-2<br />

SRE186-7-17-3<br />

LEGEND<br />

Actlw layer In dry rand and gravl<br />

OPMF In I, I, I4 I,<br />

Unfrozen sand<br />

81 Sllty Cloy dopo~it<br />

Bodrock<br />

.I I,<br />

hi ~0.5 rn<br />

h2'3.8 m<br />

h3:15.0 m<br />

h4'12.0 rn<br />

h5:31.2 m<br />

&Field curve<br />

Dry sand and ravel<br />

SR: 86-7-24<br />

45 - SRE:86-7-17-3<br />

shotgun wurce<br />

Hammer aource<br />

40 -<br />

t<br />

V~=ISOO mi'<br />

1 1 I I<br />

20 30 40 60<br />

AE/2 (rn)<br />

L<br />

K)(<br />

L\<br />

01<br />

0 IO 203040500708090100110120130<br />

DISTANCE (m)<br />

984

- 9-<br />

-<br />

'E<br />

ELECTROMAGNETIC SURVEY ON LINE LC<br />

KANGIQSUALUJJUAQ AIRPORT<br />

Z I<br />

I I<br />

3 h00 5*200 ' 5+400 S+kQ O+ihOkrn)<br />

Fig. 6-<br />

1<br />

t 215m 7.5-15m bISm 7.5-15rn<br />

Electromagnetic profiles (coplanar c<strong>on</strong>figura- is available for ground thruthing but these vdlues are<br />

ti<strong>on</strong>, EM 34-3) with transmitter-receiver separa- in accordance with many drill and holes thermistor cable<br />

ti<strong>on</strong>(s) of 10, 20 and 40 m. Uean c<strong>on</strong>ductivities data in similar materials available around the village.<br />

(rr)are shown and allow a semi-quantitative es- The thickness is quite variable in sand and gravel.<br />

timate of the thickness of permafrost. The abs- ERS, IP pseudo-secti<strong>on</strong>s and EM surveys indicated that<br />

cissa represents the horiz<strong>on</strong>tal distance and permafrost is perforated with taliks and is quite irrethe<br />

ordinate the apparent c<strong>on</strong>ductivity in mhos. gular at its base. This situati<strong>on</strong> is explained by the<br />

layer the base of which is bounded at an approximate<br />

depth of 15 m. The increase of c<strong>on</strong>ductivity at the 40 m<br />

separati<strong>on</strong> suggests str<strong>on</strong>gly that there is no permafrost<br />

at depth greater than 15 m. By comparis<strong>on</strong> with the permafrost<br />

thicknesses determined by resistivity and chargeability<br />

pseudo-secti<strong>on</strong>s from the IF survey (Pig. 5)<br />

which yielded 10 and 13 m respectively, it is c<strong>on</strong>cluded<br />

that the permafrost thickness at this stati<strong>on</strong> is located<br />

between 12 and 15 m. The interpretati<strong>on</strong> of this EM survey<br />

indicates that the lower boundary of permafrost is<br />

irregular as observed in the resistivity pseudo-secti<strong>on</strong><br />

(Fig. 5). Although it gives less detailed results, the<br />

EM method is also useful to outline vertical and lateral<br />

variati<strong>on</strong>s of permafrost and it c<strong>on</strong>firms results obtained<br />

with other methods.<br />

DISCUSSION OF THE RESULTS AND CONCLUSIONS<br />

Some difficulties are faced in the interpretati<strong>on</strong> of the<br />

results obtained with the geophysical methods used. Problems<br />

are encountered with ERS measurements in areas of<br />

very dry sand and gravel. This is mainly due to large<br />

electrode c<strong>on</strong>tact resistance and the extremely high resistivity<br />

of near surface soils. Quite often the IP method<br />

encounters the same difficulties as in ERS dry sand<br />

and gravel. C<strong>on</strong>sequently, the moist mass cover and soil<br />

water table level are important factors<br />

be c<strong>on</strong>sidered<br />

in the determinati<strong>on</strong> of the lateral and vertical distributi<strong>on</strong><br />

of permafrost in marine and fluvioglacial coarse<br />

grained deposits. A comparis<strong>on</strong> of the mechanical and<br />

geophysical soundings is of the upmost impostance as it<br />

provides a good oportunity to verify the precisi<strong>on</strong> of<br />

the ER and IP soundings in estimating active layer thicknesses.<br />

when using the dipole-dipole c<strong>on</strong>figurati<strong>on</strong>, IP<br />

data are not reliable to outline the active layer bounde<br />

ry; the large electrode spread ( 210 m) does not allow a<br />

sufficient resoluti<strong>on</strong>. The thickness of disc<strong>on</strong>tinuous<br />

permafrost ranges from 1.5 to 20 (average: 8.1 m) under<br />

the new airport site. No drilling through the permafrost<br />

grain size variati<strong>on</strong> of the sediments which influences<br />

the physical parameters of the soils (e.g. thermal c<strong>on</strong>ductivity)<br />

which in their turn c<strong>on</strong>trol the electrical properties<br />

of permafrost terrains. Some of the difficulties<br />

related to field c<strong>on</strong>diti<strong>on</strong>s are solved through the integrati<strong>on</strong><br />

of the various geophysical results. This allowed<br />

a more accurate estimate of permafrost distributi<strong>on</strong> as<br />

illustrated in the fence diagram (Fig. 8). In the study<br />

H(m)<br />

A- 64-0-3-1 L8-6-30-S 84-8-6-4<br />

LL<br />

SEISMIC REFRACTION (SR)<br />

SR is an ancillary method of c<strong>on</strong>firming the results obtained<br />

with other geophysical methods relative to permafrost<br />

thickness and a substitute for drilling. The interpretati<strong>on</strong><br />

of the SR profiles was complicated by the<br />

occurrence of a low velocity layer generally located<br />

between the base of permafrost in the sediments and the<br />

deeper bedrock. The true depth to bedrock can be estimated<br />

by assuming a realistic value for this low velocity<br />

layer (Whitely and Greenhalgh, 1978) and calculating<br />

its thickness. An estimate of the velocity of this<br />

.<br />

third layer (below the permafrost base) is obtained from<br />

b<br />

the seismic lines d<strong>on</strong>e in unfrozen areas c<strong>on</strong>tiguous to<br />

the disc<strong>on</strong>tinuous permafrost z<strong>on</strong>es characterized by a<br />

similar stratigraphy. Thirteen seismic lines were<br />

surveyed over the new airport site. All haher shots<br />

were det<strong>on</strong>ated m 1 off the line andwhen a shotgun source<br />

was used, a hole of about 0.65 m below the ground level<br />

was dug to insure maximum energy transfer into the Fig. 8-<br />

ground. Without a knowledge of the velocity inversi<strong>on</strong>,<br />

the travel-time graph would be interpreted as a 2 layer<br />

structure (Pig. 7).<br />

St000 5+160 5+320<br />

I<br />

"I[<br />

5+480 I<br />

5+640 5+720(m)<br />

Fcncp diagram showing active layer thickness<br />

and permafrost distributi<strong>on</strong> under the proposed<br />

airstrip according to the integrated interpretati<strong>on</strong><br />

of all geophysical methods.<br />

985

of the airport site located in a disc<strong>on</strong>tinuous permafrost<br />

z<strong>on</strong>e, integrated geophysical methods are useful for three<br />

reas<strong>on</strong>s: 1) determinati<strong>on</strong> of active layer thickness, 2)<br />

delineati<strong>on</strong> of horiz<strong>on</strong>tal and vertical extensi<strong>on</strong> of permafrost,<br />

3) estimati<strong>on</strong> of the depth to bedrock. Optimisati<strong>on</strong><br />

of the combined geophysical results dem<strong>on</strong>s- that<br />

the ERS and SR surveys are most useful to estimate thick<br />

active layer depths. In decreasing order of resoluti<strong>on</strong>,<br />

IP, ERS and EM surveys are the most reliable integrated<br />

geophysical methods to outline the horiz<strong>on</strong>tal and vertical<br />

distributi<strong>on</strong> of permafrost. ER and IP soundings<br />

are most appropriate to calculate its thickness while IP<br />

and EM methods are the best techniques to determine both<br />

its lateral extent and thickness. Depth to bedrock is<br />

most accurately defined with integrated ERS, RS and gravimetric<br />

methods.<br />

Most of the stratigraphic data are obtained with.the ERS<br />

methods. The water table level is generally located<br />

with a combinati<strong>on</strong> of ERS, IP and SR methods. The<br />

amount of heterogeneity in the soils is usually evidenced<br />

by the parameters: chargeability (IP) and c<strong>on</strong>ductivity<br />

(I”.<br />

<strong>Permafrost</strong> investigati<strong>on</strong>s are clearly needed for the planning<br />

and c<strong>on</strong>structi<strong>on</strong> of airstrip and roads in northern<br />

Canada. The geophysical methods used in this investigati<strong>on</strong><br />

are complementary tools to geomorphological, drainage<br />

and soil studies.<br />

The results are needed: a) to plan and locate an airstrip<br />

site, access roads and ancillary comadities, b)<br />

to plan infrastructure and geotechnlcal studies, c) for<br />

the choice of nature, type, volume and thickness of<br />

c<strong>on</strong>structi<strong>on</strong> materials, d) to indicate the areas when<br />

an artificial insulating pad could be needed, e) to estimate<br />

the volume ofbedrockexcavati<strong>on</strong> required underneath<br />

a thin layer of sedimentary cover. Engineering<br />

problems such as blasting, quarrying, crushing and their<br />

associated costs can be more easily apprehended with the<br />

aid of the geophysical informati<strong>on</strong>. In this rebpect, we<br />

think that the sequence of geophysical methods used for<br />

this purpose is necessary c<strong>on</strong>sidering its relatively<br />

low cost.<br />

ACKNOWLEDGEMENTS<br />

The authors wish to thank the following pers<strong>on</strong>s.who c<strong>on</strong>tributed<br />

to the executi<strong>on</strong> of this study: Claire Beysserias,<br />

Christian Bouchard, Jacqueline Bouchard, Jean Desbiens,<br />

Alain Pournier, Richard Fortier, Bet& Ghlinas,<br />

Yvan Grenler, Lyne Messier, Florence Nicollin, Yv<strong>on</strong><br />

PelLetier and Johanne Plourde.<br />

REFERENCES<br />

Akimov, A.T. (1951). The study of permafrost by geophysical<br />

and geoelectrical methods in the eastern<br />

part of the Bolshezenealtaya tundra. Manuscript<br />

P<strong>on</strong>dy in to Merzlotov AN SSSR.<br />

Ananyan, A.A. (1950). Investigati<strong>on</strong> of the passage of<br />

an electric current through freezing and frozen<br />

soils. Rukopis F<strong>on</strong>dy in to Heralotoved, SSSR.<br />

Annan, A.P. and Davis, J.L. (1976). Impulse radar profiling<br />

in permafrost. Geological Survey of<br />

Canada, Paper 75-1C. 343-351.<br />

Apparao, A. & Sarma, V.S. (1981). A modified pseudodepth<br />

secti<strong>on</strong> as a tool in resistivity and IP<br />

prospecting. Geophys. Res. Bull, (19), 187-208.<br />

Ben-Hiloud, K. & Seguin, H.-K. (1987). Soluti<strong>on</strong> of velocity<br />

inversi<strong>on</strong> in seismic refracti<strong>on</strong> surveys<br />

with the use of electrical methods in three types<br />

of terrains from the Kangiqsualujjuaq valley,<br />

Northern Quebec. Comptes Rendus du 55iSme C<strong>on</strong>gres<br />

de 1’ACFAS. Ottawa, 17 p.<br />

Bostock, H.S. (1964). A provisi<strong>on</strong>al physiographic map<br />

of Canada. Geol. Surv, Can., Paper 64-35, 24 pp.<br />

Brown, J., Metz, H.C. and Hoekstra, P. (1985). Workship<br />

<strong>on</strong> pe-frost geophysics. Golden, Colorado,<br />

23-24 October 1984, CREEL, 118 pp.<br />

Compagnie Ginirale de GPophysique (1955). Abaques de<br />

s<strong>on</strong>dage ilectrique. Geophysiml Prospecting,<br />

(3), Suppl. No. 3, 50 pp.<br />

Compagnie Gindrale de Gdophysique (1963). Abaques de<br />

s<strong>on</strong>dage PlectriquelMaster Curves for Electrical<br />

Sounding. European Associati<strong>on</strong> of Explorati<strong>on</strong><br />

Geophysicists.<br />

Dostovalov, B.N. (1947). Electrical charactertstlcs of<br />

permanently frozen rocks. Akad. Nauk SSSR, 5,<br />

18-35.<br />

Douglae. B.J.W. (1968). Ghologie et reasources minirales<br />

du Canada. Partie A, Sdrie de la giologie<br />

ic<strong>on</strong>omique No. 1. Comissi<strong>on</strong> giologique du<br />

Canada, 50-165.<br />

Edwards, L.S. (1977). A modified pseudosecti<strong>on</strong> for<br />

resistivity and IP. Geophysics, (42), 5, 1020-<br />

io36 -<br />

Gahi, E. (1988). Giomorphologie cryoghe et giophysique<br />

dans la rigi<strong>on</strong> de Kangiqsualujjuaq. Ph.D.<br />

thesis, Universite Laval, 210 pp.<br />

Gahi. E., Allard, M., h Seguin, M.-K. (1987). GLophysique<br />

et dynamique holocine de plateaux palsiques<br />

i Kangiqsualujjuaq,Qu&bec nordique. Giographie<br />

physique et Quaternaire (41). 1, 33-46.<br />

Kawaski, K., Gruol, V. and Osterkamp, T.E. (.1983).<br />

Field Evaluati<strong>on</strong> Site for Ground Ice Detecti<strong>on</strong>.<br />

Report No. FHWA-”83-27, Alaska Dept. of Transportati<strong>on</strong><br />

and Publicati<strong>on</strong> Facilities.<br />

tupien, Rosenberg, Yourneaux & Assoc. Inc. (1984). Etude<br />

giotechnique, (George River), Report 5-84-710,<br />

27 PP.<br />

Rijkswaterstaat, The Neherlands (1969). Standard graphs<br />

for resistivity prospecting. European Associati<strong>on</strong><br />

of Explorati<strong>on</strong> Geophysicists.<br />

Roethlisberger, H. (1961). Seismic Refracti<strong>on</strong> Soundings<br />

in <strong>Permafrost</strong> near Thuli,,Greenland, in G.O.<br />

Roasch, edit., Geology of the Arctic, Vol. 2,<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Symposium <strong>on</strong> Arctic Geology.<br />

lrst Calgicy (Alberta) Proceedings, 1960, 970-981.<br />

Roy, A. (1972). Depth of investigati<strong>on</strong> in Wenner, threectectrode.and<br />

dipole resistivity methods. Geophysical<br />

Prospecting, (20), 329-430.<br />

Roy, A. & Apparao, A. (1971). Depth of investigati<strong>on</strong> in<br />

direct current methods+ Geophysics, (36), 943-<br />

959.<br />

986

Seguin, M.-L (1974). The use of geophysical methods in<br />

permafrost investigati<strong>on</strong>: ir<strong>on</strong> ore deposits of<br />

the central part of the Labrador Trough, northeastern<br />

Canada. Geoforum. (18), 55-68.<br />

Seguin, H.-K. (1976). Observati<strong>on</strong>s gcophysiques sur le<br />

perghlisol des envir<strong>on</strong>s du lac Minto. Cahiers<br />

de GCographie de Quibec, (TO), 20, 327-364.<br />

Seguin, W.-K. & Allard, H. (1984s). La repartiti<strong>on</strong> du<br />

pergilisol dans la rCgi<strong>on</strong> du detroit de Manitounuk,<br />

c8t6 outst de la mer d'hds<strong>on</strong>, Canada.<br />

Garladian Journal of Earth Sciences, (21). 354-<br />

364.<br />

Seguin, H.-K. EL Allard, M. (1984b). Le pergelisol et<br />

les processus themokaystiques la de rhgi<strong>on</strong> de<br />

la rivibre Nastopoca, Nouveau-QuBbec. GQographie<br />

physique et Quaternaire, (38), 11-25.<br />

Seguin, M.-K. & Allard, d. (1987). La geophysique appliquge<br />

au pergelisol, Quibec nordique: historique<br />

et diveloppements recents. Giographie physique<br />

et Quaternaire, (4t), 127-140.<br />

Taylor, F.C. (1968). Operati<strong>on</strong> Torngat, Quebec, Newfoundland-Labrador.<br />

1_" Report of activities;<br />

Geol. Surv. Can. Part A, Study 68-1, 149-150.<br />

Taylor, P.C. (1974). Rec<strong>on</strong>naissance geology of a part<br />

of the Precambrian Shield, Northern Quebec and<br />

Northwest Territories. Geol. Surv, Can., Paper<br />

74-21, 9 pp and map.<br />

Whitely, R.Y. & Greeshalgh, S.A. (1978). Velocity inversi<strong>on</strong><br />

and the shallow seismic refracti<strong>on</strong> method.<br />

Geoexplorati<strong>on</strong>, (17), 125-141.<br />

Zohdy, A.A.R. (1975). Automatic interpretati<strong>on</strong> of<br />

Schlumberger sounding curves, using modified<br />

Dar Zarrouk Functi<strong>on</strong>s, U.S. Geol. Surv. Bull. no.<br />

1313 E, 41 pp.<br />

987

D.C. RESISTIVITY ALONG THE COAST AT PRUDHOE BAY, ALASKA<br />

P.V. Sellmann, AJ. Delaney and S.A. Arc<strong>on</strong>e<br />

U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering Laboratory, Hanover, N.H. 03755-1290 USA<br />

SYNOPSIS<br />

Electrical resistivity measurements, at three sites in Prudhoe Bay, Alaska,<br />

were made to provide an understanding of marine modificati<strong>on</strong> to eoastal permafrost, and to<br />

evaluate D.C. resistivity techniques for coastal subsea permafrost studies. The measurements<br />

were made using Wenner electrical resistivity soundings. Profiles extended 2.8 km offshore and<br />

inland bey<strong>on</strong>d the last siyns OF tundra modificati<strong>on</strong> by coastal processes. Offshore measurements<br />

were made with a floating cable, and inland measurements were made using driven electrodes. The<br />

observati<strong>on</strong>s indicate that the electrical properties of permafrost beneath the coastal bluff and<br />

adjacent tundra are rapidly modified by coastal erosi<strong>on</strong> and periodic flooding during storms.<br />

Al<strong>on</strong>y <strong>on</strong>e c<strong>on</strong>trol line, apparent resistivity changes corresp<strong>on</strong>ded with the c<strong>on</strong>figurati<strong>on</strong> of the<br />

top of ice-b<strong>on</strong>ded permafrost observed by Baker (1987). Modeling supported by the c<strong>on</strong>trol data<br />

permitted a close interpretati<strong>on</strong> of the positi<strong>on</strong> of the top of ice-b<strong>on</strong>ded subsea permafrost and<br />

provided a ranye of real resistivities for offshore materials.<br />

'<br />

INTRODUCTION<br />

Background<br />

Most subsea permairost formed <strong>on</strong> the c<strong>on</strong>tinental<br />

shelves when they were exposed during<br />

low sea level stands associated with periods<br />

of major yLacial activity. This permafrost<br />

was covered by risiny sea level as the glaciers<br />

melted. Even though the sea level is now<br />

fairly stable, permafrost is still heiny .inundated<br />

in some areas of active coastal erosi<strong>on</strong>.<br />

Inundati<strong>on</strong> can dramatically change the properties<br />

of permafrost due to exposure to salt;<br />

water and to as much as a 10°C warming in some<br />

coastal settings. Al<strong>on</strong>y segments of the Beaufort<br />

Sea coastline, permafrost is undergoing a<br />

siynificant reducti<strong>on</strong> in strenyth, thaw settlement,<br />

gas hydrate decompositi<strong>on</strong>, and redistributi<strong>on</strong><br />

of free gas. This study establishes<br />

some electrical resistivity values for coastal<br />

permafrost near Prudhoe Bay, an area undergoiny<br />

active coastal modificati<strong>on</strong>.<br />

Recent studies (Scott, 1975; Corwin, 1983;<br />

Dyck 'et al., 1Y83; Sellmann et al., 1Y85)<br />

indicate that yeophysical D.C. resistivity<br />

methods can be used for subsea permafrost<br />

investiyati<strong>on</strong>s. These methods may be best<br />

suited for shallow coastal waters where iceb<strong>on</strong>ded<br />

permafrost is expectea at shallow<br />

depths (C30 m) below the seabed, permitting<br />

relatively short, mare-manageable electrode<br />

arrays. The technique also has potential in<br />

areas where seismic methods may encounter<br />

problems, such as sediments c<strong>on</strong>taining small<br />

amounts of natural gas in voids, which yreatly<br />

attenuate seismic signals. Thus, practical<br />

implementati<strong>on</strong> of the D.C. soundiny method can<br />

complement deeper soundiny transient electromagnetic<br />

methods for certain areas. Studies,<br />

by the Earth Technology Corp. (19M5, 1986)<br />

have suggested that modified transient EM<br />

988<br />

equipment and procedures and magnetic inducti<strong>on</strong><br />

might also be used for investigati<strong>on</strong>s at<br />

shallow depths below the seabed. ,At present,<br />

however, a combinati<strong>on</strong> oE D.C.'and Transient<br />

EM is the most practical yeophysical approach<br />

to obtaining informati<strong>on</strong> <strong>on</strong> the entire offshore<br />

permafrost secti<strong>on</strong> (Ehranbard et al.,<br />

1983: Walker et al., 1985).<br />

Resistivity data are interpreted by c<strong>on</strong>structiny<br />

models that generate output similar to<br />

observati<strong>on</strong>s. Hecause closed-form inversi<strong>on</strong><br />

soluti<strong>on</strong>s are virtually impossible to achieve,<br />

computati<strong>on</strong>al programs utilizing fast, iterative<br />

procedures are now commo~Ly used to produce<br />

a layered model to fit the data. These<br />

programs often require some preliminary estimates<br />

for the resistivity and thickness of<br />

each assumed layer. Only a small amount of<br />

resistivity data has been correlated with subsurface<br />

secti<strong>on</strong>s having a known distributi<strong>on</strong><br />

of ice-b<strong>on</strong>ded permafrost, and much of it is<br />

proprietary. This lack of resistivity data<br />

near shore is also due to the limited experience<br />

with shallow penetrating electrical<br />

methods in areas of ice-b<strong>on</strong>ded subsea yermafrost<br />

and is <strong>on</strong>e of the reas<strong>on</strong>s for this<br />

study .<br />

objectives and Approach<br />

The objectives of this study were to establish<br />

resistivity values and their spatial variati<strong>on</strong><br />

for coastal permafrost in areas of active<br />

erosi<strong>on</strong>, and to understand the inf Iuence of<br />

erosi<strong>on</strong> and periodic flooding during storms<br />

up<strong>on</strong> those values. Thus we hoped to gain<br />

informati<strong>on</strong> necessary tor the interpretati<strong>on</strong><br />

of electrically based methods. A aec<strong>on</strong>dary<br />

ob~ective was to evaluate our marine D.C.<br />

resistivity surveying equipment for detecting<br />

subsea permafrost at shallow depths in coastal<br />

waters.

Sites with differing coastal relief and beach<br />

c<strong>on</strong>figurati<strong>on</strong> were selected in Pruahoe bay.<br />

It was assumed that the general distributi<strong>on</strong><br />

of subsurface materials would be sim'ilar at<br />

all study sites and that coastal erosi<strong>on</strong> rates<br />

were approximately 1 m/yr. Data <strong>on</strong> ,land were<br />

collected with D.C. soundings made parallel to<br />

the shoreline and moved progressively inland<br />

to a point bey<strong>on</strong>d any evidence of Eloodiny ot<br />

the tundra surface. spacings between soundings<br />

<strong>on</strong> land varied to provide coverage of<br />

local relief and features found <strong>on</strong> the beaches,<br />

bluffs, and adjacent tundra surfaces. The<br />

farthest-inland soundings were c<strong>on</strong>sidered<br />

references representing subsurface electrical<br />

properties not yet modified by coastal processes,<br />

and were made <strong>on</strong> what appeared to be undisturbed<br />

tundra surfaces. A floating cable<br />

was used to extend the survey lines up to 2.8<br />

km offshore by protili,ny and soundiny. The<br />

cable was normal to the shoreline for most of<br />

this surveying. soundings and protiliny otfshore<br />

were d<strong>on</strong>e at regular intervals from the<br />

beach.<br />

D.C.<br />

SOUNDING METHOD<br />

Resistivity was measured using the symmetric<br />

Wenner array illustrated in Figure 1. The two<br />

outer electrodes provide a path for current I,<br />

and the resulting difference in ground potential<br />

v is measured between the inner electrodes.<br />

For homogeneous ground, the real<br />

resistivity p in ohn-m is equal to the<br />

measured apparent resistivity par which is<br />

found from the formula<br />

V<br />

pa = 2t 2 i<br />

where is the interelectrode spaciny. Over<br />

layered earth, Pa is also a functi<strong>on</strong> of the<br />

layer thicknesses and resistivities and so is<br />

an apparent quantity. Computati<strong>on</strong>al modeling<br />

must then be used to interpret the Sounding<br />

curve. .<br />

On land we used copper-clad electrodes driven<br />

approximately 15 cm ink0 the ground at a spacings<br />

up to 50 m. The low resistivity of the<br />

thawed active layer and marine sediments <strong>on</strong><br />

the beach ensured good electrode c<strong>on</strong>tact. The<br />

marine cable was fabricated by a commercial<br />

cabling company and is buoyant. It was 150 m<br />

l<strong>on</strong>g .with eight Wenner a spacings ranginy from<br />

3 to 46 m. The progressively larger 5 spacings<br />

in the Wenner array telescoped out f,rom<br />

the end nearest the boat, with the first electrode<br />

always in use. The cable utilized<br />

simple lead electrodes as described in VOnArX<br />

(1962).<br />

A regulated current signal was yenerated by a<br />

Huntec transmitter, and potential difterence<br />

was measured with a Fluke digital voltmeter.<br />

The Huntec unit has switch-selectable output<br />

impedance, and output current is variable to<br />

1.5 A. In most cases maximum output current<br />

was used for the marine surveys. The potential<br />

difference was determined by subtracting<br />

values read during the cycle from values<br />

for the transmitter off period. The otf reading<br />

allowed eliminati<strong>on</strong> of naturally occurriny<br />

background potentials.<br />

1 1<br />

A A A A<br />

Figure 1. Multi-electrode henner array. The<br />

electrode separati<strong>on</strong> a was varied from 0.5 to<br />

50 m <strong>on</strong> land and 3 to 46 m otfshore.<br />

The rates of coastal erosi<strong>on</strong> and associated<br />

modificati<strong>on</strong> of the cold terrestrial permafrost<br />

vary greatly al<strong>on</strong>y the Beaufort Sea<br />

coastline and depend <strong>on</strong> material type, coastal<br />

relief, and exposure. Three sites were<br />

selected for this study in the Prudhoe Ray<br />

area and are shown in Fiyure 2. The Prudhoe<br />

Bay area has low coastal erosi<strong>on</strong> rates compared<br />

to more western seyments of the Beautort<br />

Sea, where rates comm<strong>on</strong>ly exceed 5 m/yr<br />

(Reimnitz et al. , 1985). Rates in Pruohoe Bay<br />

are closer to 1-2 m/yr and are probably lower<br />

in this area because of the coarser material<br />

and lower ground ice volumes in the upper part<br />

of the permafrost secti<strong>on</strong>. Infiltrati<strong>on</strong> of<br />

sea water can rapidly influence electrical<br />

properties of coarse-yrained material if voids<br />

are not ice-f illed. In general, chemical<br />

modificati<strong>on</strong> by salt should be much less rapid<br />

in fine-grained than in.coarse sediment.<br />

Site 1<br />

This site, shown in Figure 2, is situated<br />

several hundred meters east of the Nest Dock<br />

in Prudhoe Bay. It has R low bluff about 1.5<br />

m hiyh and a very narrow 1-3 m -wide beach.<br />

Data for this site are shown in Figure 3. The<br />

fresh nature of some of the exposures suyyests<br />

active erosi<strong>on</strong>. Only a small increase in sea<br />

level is required to bring waves in direct<br />

c<strong>on</strong>tact with the bluff. This low bluff and<br />

the adjacent terrain are easily overtopped<br />

duriny storms, as indicated by the large<br />

amount of driftwood found more than 100 m<br />

inland.<br />

Direct observati<strong>on</strong>s (Baker, 1987) of the depth<br />

to the top of ice-b<strong>on</strong>ded permafrost otfshore,<br />

shown in Figure 3, for this line provided<br />

ideal c<strong>on</strong>trol for the marine resistivity<br />

observati<strong>on</strong>s. Raker's (1987) profile was<br />

based <strong>on</strong> drilling and probing. Water depth<br />

data incluaea in the profiles were collected<br />

duriny our resistivity survey.<br />

Site 2<br />

This site is about 3.7 km northeast of the<br />

East Uock in Prudhoe Hay (Fiy. 2). The tallest<br />

coastal bluffs occur here (rig. 4), ranginy<br />

from 2 to 3 m in height. The beach is<br />

about 6 m wide and is paved with sod blocks<br />

that slumped t m m the tundra surtace. The<br />

bluft face is actively erodiny, with larqe<br />

989

~~ ~” ~~ -<br />

Figure 2. Index map of the Prudhoe Bay area showing the locati<strong>on</strong><br />

of our study sitee,<br />

blocks collapsing over fresh exposures. Overtopping<br />

of the bluff appears to be very limited<br />

with <strong>on</strong>ly minor changes in the vegetati<strong>on</strong><br />

patterns near the bluff crest due to salt<br />

spray. The materials exposed in the bluff are<br />

silty sands, which seem similar €or all sites.<br />

No informati<strong>on</strong> <strong>on</strong> subsea permafrost was available<br />

for sites 2 and 3.<br />

site 3<br />

Boa<br />

roo<br />

This site is approximately 2 km east of the<br />

West Dock (Pig. 2). This Locati<strong>on</strong> (Fig. 5) is<br />

different .from the previous sites in that it<br />

lacks a coastal bluff. The beach tormed<br />

between two points of land and yrades into the<br />

low-lying adjacent tundra. Overtopyiny of the<br />

beach and inland tundra is extensive because<br />

of the low elevati<strong>on</strong> of the tundra surface.<br />

Driftwood can be found more than 200 m inland.<br />

RESULTS AND DISCUSSION<br />

Figure 3. C<strong>on</strong>toured apparent resistivity data<br />

tor site 1 in Pruahoe bay. C<strong>on</strong>toured data<br />

from an expanded segment ot the line that<br />

includes the beach are shown in the lower part<br />

ot the iiyure. The positi<strong>on</strong> ot: the top ot<br />

ice-b<strong>on</strong>ded permaf rost (atter Hakef, 1987) is<br />

shown in the upper part of the figure as a<br />

solid line, The comQuted depth to the top of<br />

ice-b<strong>on</strong>ded permafrost (shown by dots) was<br />

calculated using the three-layer models at the<br />

top ot the fiyure.<br />

The soundings <strong>on</strong> land were all made asymmetrically<br />

by expanding the electrodes in <strong>on</strong>e<br />

directi<strong>on</strong> parallel to the water’s edge at a<br />

spacings of 0.5, 1, 2, 3, 4, 5, 7, 10, 20, 30<br />

and 50 m. The marine resistivity data were<br />

yathered every 25 m al<strong>on</strong>y profiles at fixed 5<br />

spacings <strong>on</strong> lines normal to the coast. The<br />

offshore 5 spacings comm<strong>on</strong>ly used were 3, 6,<br />

9, 12, 15, 30 and 46 m. In Yiyures 3-5 the<br />

apparent resistivity values are c<strong>on</strong>toured as a<br />

tuncti<strong>on</strong> of distance and a spacing. The positi<strong>on</strong><br />

of important teatures such a6 the coastal<br />

hlutf, beach, and shoreline are noted.<br />

Inserts with expanded scales in the tiyures<br />

illustrate the rapid changes in resistivity<br />

seaward of the coastal bluff. No insert was<br />

c<strong>on</strong>structed tor Site 3 since changes landward<br />

were more yradual.<br />

990

~<br />

r 1<br />

0<br />

IO o'b,p<br />

- c<br />

Dlstancn Offshore (rn)<br />

1 1 1 '<br />

1000<br />

kBeri~h<br />

I I<br />

nn ' 1 4 , '<br />

\<br />

Zohm-m<br />

3<br />

30 20 IO 0 IO 20<br />

Dlat<strong>on</strong>ce Onl<strong>on</strong>d (rn) Dist<strong>on</strong>cn Offshore (m)<br />

Figure 4, C<strong>on</strong>toured apparent resistivity data<br />

for site 2 in Prudhoe Ray. water depth,<br />

height of the coastal bluff, and computed<br />

depth to the top of ice-b<strong>on</strong>ded permafrost are<br />

shown in the cross secti<strong>on</strong> in the upper part<br />

ot the figure. c<strong>on</strong>toured data for an expanded<br />

segment of the line that includes the beach<br />

are shown in the lower part of the figure.<br />

Land observati<strong>on</strong>s<br />

There are some unique features in the <strong>on</strong>-land<br />

resistivity data that appear related to surface<br />

relief, beach width, and potential for<br />

surface floodiny. The greatest resistivities<br />

were observed at site 2 (Fig. 4) , which had<br />

the highest bluffs and the least physical<br />

indicati<strong>on</strong> of flooding or other inland disturbance.<br />

A maximum apparent resistivity of<br />

2800 ohm-m was observed 65 m inland ot the<br />

bluff. The high values and the horiz<strong>on</strong>tal<br />

dispositi<strong>on</strong> of the c<strong>on</strong>tours suggest that' site<br />

2 has had the least modificati<strong>on</strong>. In c<strong>on</strong>trast,<br />

Sites 1 and 3 show the influence of<br />

past flooding by the significant reducti<strong>on</strong> in<br />

near-surtace resistivities and the seaward<br />

slopiny of the resistivity c<strong>on</strong>tours. Nearsurface<br />

resistivities at Site 3 are less than<br />

6 ohm-m more than 175 m inland from the inner<br />

edge of the active beach, a distance that<br />

corresp<strong>on</strong>ds with the inner limit ot most<br />

recent flooding as indicated by drittwood and<br />

other dehris. The topoyrayhy in this area<br />

\<br />

..<br />

200 100 6 100 200 300 400 SO0<br />

Dlrrancr Onl<strong>on</strong>d (rn)<br />

Dlstnnca Offshora (rn)<br />

Figure 5. C<strong>on</strong>toured apparent resistivity data<br />

for Site 3 in Prudhoe Bay. water depth,<br />

coastal relief, and computed depth to the top<br />

of ice-b<strong>on</strong>ded permatrost are shown in the<br />

upper part of the figure.<br />

suggests that coastal flooding may have<br />

occurred at this site for many years. Values<br />

greater than 500 ohm-rn are not founa at depth<br />

until the inner limit of flooding is exceeded.<br />

At the more easterly site 2, the 50U<br />

ohm-m values corresp<strong>on</strong>d with the tall bluffs<br />

and higher-elevati<strong>on</strong> tundra surface where<br />

tlooding apparently aoes not occur.<br />

Seaward Ubgervati<strong>on</strong>s<br />

There are some comm<strong>on</strong> patterns in all data<br />

from seaward of the coastal bluffs. No apyarent<br />

resistivity values greater than 100 ohm-m<br />

were observed at all a spacings. The values<br />

and trends were similar between the blufts and<br />

the water edge, with no values at the water<br />

edge greater than 50 ohm-m at 50-m spacinys; . .<br />

most values were less than 40 ohm-m.<br />

variati<strong>on</strong>s in water depth al<strong>on</strong>y the study<br />

lines were usually less than 1 m, the total<br />

depth never exceeded 2 rn, and the water resistivity<br />

was always about 0.47 ohm-m, The<br />

c<strong>on</strong>toured data of Figure 3 dem<strong>on</strong>strate that<br />

these parameters were not sufficient to mask<br />

resistivity variati<strong>on</strong>s at depth. For examgle,<br />

the larger change in resistivity, at depth in<br />

Figure 3 occurs in a z<strong>on</strong>e between 3UU and 400<br />

m where there is less than a 0.5-rn variati<strong>on</strong><br />

in water depth. This small change in water<br />

depth cannot account for the more than 6 ohm-m<br />

resistivity chanye seen across the z<strong>on</strong>e at an<br />

- a spacing of 46 m, since earlier field observati<strong>on</strong>s<br />

and theoretical c<strong>on</strong>siderati<strong>on</strong>s<br />

(Sellmann et al., 1985) have shewn that a 0.5-<br />

m chanye in water depth would account for a<br />

variati<strong>on</strong> of less than 1 ohm-m. Resistivity<br />

changes at the small a spacings (3-6 m) are<br />

expected for the small chanyes in water depth<br />

(k'iy. 3 and 6).<br />

991

-<br />

0<br />

E<br />

- 10<br />

f<br />

e<br />

63 20<br />

7<br />

E<br />

I 1 I I I I I I<br />

30<br />

24a<br />

Agparent resistivity data for the other two<br />

a 4<br />

0 200 4 00 6 00 800<br />

Olstance Offshore (m)<br />

Figure 6. C<strong>on</strong>trol data for Site 1 (from Baker<br />

1987) and apparent D.C. resistivity data for<br />

five a spacings for a line parallel to the<br />

c<strong>on</strong>trol.<br />

The relatively large variati<strong>on</strong>s in resistivity<br />

with depth and the c<strong>on</strong>figurati<strong>on</strong> of the c<strong>on</strong>tours<br />

corresp<strong>on</strong>d with the shape of the top of<br />

ice-b<strong>on</strong>ded permafrost observed in the c<strong>on</strong>trol<br />

secti<strong>on</strong> of Figure 3. However, the anomaly in<br />

the resistivity data is shoreward of the break<br />

(the shard increase in permafrost depth at 400<br />

m) in the c<strong>on</strong>trol data. This discrepancy may<br />

be caused by our resistivity line beiny<br />

slightly east of the c<strong>on</strong>trol. The marine<br />

resistivity data at the other sites (Yiy. 4<br />

and 5) also show similar breaks, which are<br />

taken to indicate a sudden increase in depth<br />

to the top of the ice-b<strong>on</strong>ded permafrost. The<br />

positi<strong>on</strong>s of the breaks corresp<strong>on</strong>d approximately<br />

with the 1.5-m water depth.<br />

There is a noticeable gradient in all the resistivity<br />

data that occurs within about 200 m<br />

of the beach and appears to reflect chanyes in<br />

the electrical properties of permafrost. This<br />

is believed due to warming in the marine<br />

envir<strong>on</strong>nent. Apparent resistivities at our<br />

sites fall below 20 ohm-m within the first 100<br />

rn of the shore at 46-m fi spacinys.<br />

Modelinq<br />

Modeling of the offshore apparent resistivity<br />

data using Baker's (1987) depth profile for<br />

site 1 (Pig. 3 , 6) achieved a good fit using<br />

three-layer models. The modeling was d<strong>on</strong>e<br />

using a commercially available resistivity<br />

inversi<strong>on</strong> software packaye (RBSIX, Interpex<br />

Limited). Three models were used tor the best<br />

fit and are shown, al<strong>on</strong>g with the calculated<br />

positi<strong>on</strong> of the top of ice-b<strong>on</strong>cied permafrost,<br />

992<br />

.- . f<br />

in Figure 3. Sec<strong>on</strong>d-layer resistivity was<br />

increased with water depth and distance from<br />

shore. A resistivity of 1.1 ohm-m was used<br />

when water depths were 1.5 m and less, 2.5<br />

ohm-m for the 1.6-1.8 m range, and 2.7 ohm-m<br />

for depths 1.9 m and greater. These resistivities<br />

seem logical because of the possibility<br />

of salt enrichment of the bed sediments in the<br />

shallow water z<strong>on</strong>e when salt is rejected during<br />

formati<strong>on</strong> of the sea ice. At yreater<br />

water depths there would be more chance for<br />

mixiny and treshening of the bed sediments.<br />

sites ( 2 and 3) were interpreted using the<br />

models developed for Site 1. The calculated<br />

positi<strong>on</strong> of the top of ice-b<strong>on</strong>ded permafrost<br />

is shown in the upper parts of Figures 4 and<br />

5.<br />

The models for Site 1 indicate real resistivities<br />

for the sediment above the ice-b<strong>on</strong>ded<br />

permafrost (layer 2) and for the ice-b<strong>on</strong>ded<br />

permafrost (layer 3 ). The model is not yreatly<br />

influenced by variati<strong>on</strong>s in resistivity of<br />

the third layer. Resistivity of the iceib<strong>on</strong>ded<br />

permafrost can be varied from 200 to 1000<br />

ohm-m without siynificant change in the calculated<br />

depth to the top of this layer. However,<br />

calculated depths of the ice-b<strong>on</strong>ded permafrost<br />

are extremely sensitive to changes in<br />

the resistivity of the sec<strong>on</strong>d layer. For<br />

example, where the observed depth to the top<br />

of the ice-b<strong>on</strong>ded permafrost is 22 m below the<br />

seabed, a f 0.5 ohm-m variati<strong>on</strong> in resistivity<br />

providing the best fit can cause a f 6 m<br />

variati<strong>on</strong> in layer thickness. Even though<br />

first-layer parameters are also important,<br />

they are not a problem since they can be<br />

directly measured at the time of a survey.<br />

This equipment and technique prepared for investiyati<strong>on</strong>s<br />

in shallow coastal waters with a<br />

maximum electrode spacing of 50 m is limited<br />

to operati<strong>on</strong>s in water that does not exceed 6-<br />

7 m in depth. This is illustrated in Fiyure<br />

7, which shows 50-m 2 spaciny model resistiv-<br />

APPARENT<br />

RESISTNIW<br />

(ohmmeters)<br />

7 m<br />

O J<br />

i<br />

0 5 IO 15 20 25 30<br />

WATER DEPTH (meters)<br />

Fiyure 7. Model resistivity data (50-m g<br />

spaciny) for various water depths in cases<br />

where ice-b<strong>on</strong>ded perrnatrost is at 3, 7 and 20<br />

m depths beneath the seabed.

ity data as a tuncti<strong>on</strong> ot water depth in cases<br />

where ice-b<strong>on</strong>ded permafrost at YO0 ohm-m is<br />

beneath three sediment (2.5 ohm-m) depths ot<br />

3, 7 and 20 m. These model parameters used<br />

were for c<strong>on</strong>diti<strong>on</strong>s similar to those at the<br />

Prudhoe Ray sites. The curves show that<br />

bei<strong>on</strong>d about a 7-m water depth there is little<br />

sensitivity tu the total depth of permatrost.<br />

SUEIPIAKY AND CONCLUSIONS<br />

D.C. resistivity data trom an arctic coastal<br />

setting illustrate the impact of marine inundati<strong>on</strong><br />

<strong>on</strong> cold permarrost formed <strong>on</strong> land, The<br />

D.C. resistivity technique using 3 Wenner<br />

floatiny array with maximum electrode syaciny<br />

of 50 m also appears to proviae a tool for<br />

understanding the electrical yroparties and<br />

distributi<strong>on</strong> of: permatrost in these shallow<br />

coastal waters where ice-b<strong>on</strong>ded permafrost may<br />

not be more than 30 m below the seabed and<br />

where water deDths uo not exceed 6 to 7 m.<br />

Agyarent resistivity observati<strong>on</strong>s for henner<br />

electrode separati<strong>on</strong>s up to 50 m made al<strong>on</strong>y<br />

several cross secti<strong>on</strong>s extending from lana<br />

offshore into Prudhoe Bay have some similar<br />

characteristics: (1) resistivities yreater<br />

than 20 ohm-n were not observed more than 100<br />

m trom shore, (2) maximum resistivities at the<br />

water‘s edye were around 50 ohm-m, (3) resistivities<br />

greater than 100 ohm-m were not tound<br />

seaward of the coastal blufts, and (4) resistivities<br />

Just inland of the bluff can increase<br />

above the seaward values by an order of maynitude.<br />

Modeling indicates that real resistivities<br />

for the sediment over ice-b<strong>on</strong>ded permafrost<br />

ranged from 1.1 to 2.7 ohm-m and Chat<br />

the permafrost may range from 200 to 1000<br />

ohm-m.<br />

Resistivity c<strong>on</strong>tour patterns and modeling<br />

results corresy<strong>on</strong>d well xith the drilling and<br />

penetrometer observati<strong>on</strong>s of Baker (1987):<br />

thus this geophysical approach has been useful<br />

in this yeoloyical settiny and appears to have<br />

applicati<strong>on</strong>s for scientitic and enyineeriny<br />

investigati<strong>on</strong>s such as offshore ilripeline<br />

design anu routiny. The c<strong>on</strong>tours and modeliny<br />

suggest that a rapicl increase in the depth to<br />

the top ot ice-b<strong>on</strong>dea permafrost seen at the<br />

c<strong>on</strong>trol site also occurs al<strong>on</strong>y other study<br />

lines in Prudhoe Hay. The positi<strong>on</strong> of this<br />

z<strong>on</strong>e ~f noticeable increase in depth to the<br />

top of germatrost seems to corresp<strong>on</strong>d approximately<br />

with the 1.5-m water del~th.<br />

The data <strong>on</strong> changing resistivities within 200-<br />

300 m of the coastline may also provide usetul<br />

informati<strong>on</strong> <strong>on</strong> historical erosi<strong>on</strong> rates.<br />

KEYEHENCES<br />

Baker, G C (1987).<br />

salt redistributi<strong>on</strong> during freezing of<br />

saline sand columns, with applicati<strong>on</strong>s CO<br />

subsea <strong>Permafrost</strong>. Ph.D. Thesis, University<br />

ot Alaska, Fairbanks, 232 pp.<br />

Corwin, R F (1983).<br />

Marine permafrost detecti<strong>on</strong> usiny galvanic<br />

electrical resistivity methods. Proceedinys,<br />

15 Offshore Technoloyy <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> (1) I<br />

329-336.<br />

Uyck, A Vi Scott W J & Lobach J (1983).<br />

Waterborne resistivity/induced polarizati<strong>on</strong><br />

survey of Collins Bay, Wollast<strong>on</strong> Lake.<br />

Geoloyical survey of Canada, Paper 82-11,<br />

p. 281-289.<br />

Earth Technology Corp. (1985).<br />

Feasibility investiyati<strong>on</strong> of marine electromaynetic<br />

system. C<strong>on</strong>tract report tor US<br />

Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering<br />

Laboratory, 24 pp.<br />

Earth Technology Cory. (1986).<br />

Feasibility investigati<strong>on</strong> - shallow transient<br />

electromaynetic (TDEM) system. C<strong>on</strong>tract<br />

report for Us Army Cold Regi<strong>on</strong>s <strong>Research</strong> and<br />

Enyineering Laboratory, 22 pp.<br />

Ehrenbard, R L, Hoekstra P & Rozenberg, G<br />

(1983).<br />

Transient electromaynetic .saundinqs for permafrost<br />

mapping. Proc. Fourth Int. C<strong>on</strong>f. <strong>on</strong><br />

<strong>Permafrost</strong>, Fairbanks: Washinyt<strong>on</strong>, DC,<br />

Nati<strong>on</strong>al Academy of Sciences, 272-277.<br />

Keimnitz, E, Graves, S M & Barnes, P W<br />

(1985).<br />

Beaufort sea coastal erosi<strong>on</strong>, shoreline<br />

evoluti<strong>on</strong>, and sediment flux. U.S. Geoloyical<br />

Survey, open-File Report 85-380, 1-18.<br />

Scott, W J (1975).<br />

preliminary experiments in marine resistivity<br />

near Tuktoyaktuk, District oi Mackenzie.<br />

Geoloyical Survey of Canada, paper<br />

75-1A, 141-145.<br />

bellmann, P V, Delaney, A J & Arc<strong>on</strong>e, Y A<br />

(1985).<br />

Mappinq resistive seabed features using<br />

D.C. methods. Proc, of the Arctic Energy<br />

Tech. Workshop, U.S. Dept. of Energy -<br />

DUE/METC-85/6014 , 136-147.<br />

V<strong>on</strong>ArX, W S (1962).<br />

An Introducti<strong>on</strong> to Physical Oceanography,<br />

422 pp. Addis<strong>on</strong> Wesley Publishing Company, Inc.<br />

cJalker, G G, Kawasaki, K & Osterkamp, T E<br />

(1985). ..<br />

Transient electromaynetic detecti<strong>on</strong> of suhsea<br />

permafrost, workshop <strong>on</strong> permafrost<br />

geophysics. US Army Cold Heui<strong>on</strong>s <strong>Research</strong><br />

and- Engineering Laboratory, special Report<br />

85-5, p. 106-108.<br />

993

EM SOUNDINGS FOR MAPPING COMPLEX GEOLOGY IN THE<br />

PERMAFROST TERRAIN OF NORTHERN CANADA<br />

A.K. Sinha<br />

Geological Survey of Canada, Ottawa, Ontario, Canada<br />

SYNOPSIS Borehole temperature measurements in several oil and gas wells in the Big Lake area of the Mackenzie Delta,<br />

N.W.T., Canada, indicated a relatively sharp decrease in permafrost thickness from about 700 m to about 100 m towards the west,<br />

over a distance of 20 km. In an attempt to obtain more detailed informati<strong>on</strong>, transient electromagnetic (EM) soundings were<br />

made al<strong>on</strong>g a 25 km line across the area.<br />

Seventeen central soundings at an average separati<strong>on</strong> of 1.5 km were made <strong>on</strong> a profile which crossed a channel of the<br />

Mackenzie River. At least two loop sizes were used at each stati<strong>on</strong> to produce good resoluti<strong>on</strong> at both shallow and large depths.<br />

The interpretati<strong>on</strong> of EM data indicated an abrupt disc<strong>on</strong>tinuity in the electrical parameters at the channel, possibly due to a<br />

change in the thermal c<strong>on</strong>diti<strong>on</strong>s. West of the channel, the permafrost is less than 100 m thick, and is underlain by 100 - 150 m<br />

thick unfrozen sediments (2-5 om). This unfrozen layer thins to about 50 m in the immediate vicinity of the channel. Below this is<br />

a moderately low resistivity material (5-8 nm) which could be another layer of unfrozen sediments. East of the channel, the<br />

permafrost is about 265 m thick increasing eastward to more than 650 m. A thin unfrozen layer (25-50 m) was detected at depths<br />

of 70-100m at all stati<strong>on</strong>s east of the channel. Interpretati<strong>on</strong> of the data was complicated by the presence of lateral<br />

inhomogeneities and irregularly shaped bodies near the channel<br />

INTRODUCTION<br />

Electrical and electromagnetic (EM) methods have successfully<br />

been used in the past few years for mapping the distributi<strong>on</strong><br />

of permafrost in Alaska and in northern regi<strong>on</strong>s of Canada<br />

(Daniel et al, 1976; Annan and Davis, 1976; Koziar and<br />

Strangway, 1978; Rozenberg et at, 1985). The methods rely<br />

<strong>on</strong> the fact that electrical resistivities of sediments increase<br />

si nificantly when they are frozen (Hoekstra et al, 1975:<br />

Oyhoeft, 1975). A number of papers have documented case<br />

histories <strong>on</strong> the applicati<strong>on</strong> of EM methods for detecti<strong>on</strong> and<br />

delineati<strong>on</strong> of permafrost in northern Canada (Hoekstra and<br />

McNeill, 1973; Rossiter et al, 1978; Sartorelli and French,<br />

1982). Sinha and Stephens (1983) used both multifrequency<br />

and transient ground EM systems for detecti<strong>on</strong> of horiz<strong>on</strong>tal<br />

interfaces between geological formati<strong>on</strong>s in the Mackenzie<br />

Delta, N.W.T., Canada, especially the c<strong>on</strong>tact between the iceb<strong>on</strong>ded<br />

permafrost and the underlying unfrozen sediments.<br />

The tests were made near exploratory oil and gas wells which<br />

had been surveyed earlier with temperature and other<br />

geophysical logs (Taylor et al, 1982). A comparis<strong>on</strong> of the<br />

depths to the interfaces from both systems showed good<br />

a reement with well-log data. The effects of lateral<br />

inl(\orno eneities were found to be less with the transient<br />

system %ta. It was also easier and less ambiguous to invert<br />

the transient EM field data in terms of a layered model.<br />

Taylor et al (1982) have recently published data <strong>on</strong> permafrost<br />

thickness at several locati<strong>on</strong>s in northern Canada based<br />

mainly <strong>on</strong> borehole temperature measurements. They<br />

detected anomalous permafrost characteristics in the Richards<br />

Island area in the Mackenzie Delta (Figure 1). West and south,<br />

of Blg Lake, the permafrost thickness ranged from over 270 m<br />

to more than 600 m in a cluster of holes. But <strong>on</strong>ly 15 km WSW<br />

of that cluster, the permafrost thickness at a number of holes<br />

<strong>on</strong> the eastern bank of a Mackenzie River channel ranged in<br />

thickness from 144 to 275 m. The last thickness value possibly<br />

relates to a transiti<strong>on</strong>al z<strong>on</strong>e since the permafrost thickness<br />

decreases to 217 m in a hole (not shown) about 1 km south.<br />

Over much of the permafrost secti<strong>on</strong>, the thermal profile is<br />

almost isothermal between 0 and -2°C. The base of the ice-<br />

135% 134<br />

Fig. 1<br />

Locati<strong>on</strong> of the survey profile in the Richards Island<br />

area, N.W.T. The thickness of permafrost at several<br />

exploratory oil and gas wells are also indicated.<br />

bearing permafrost was determined by detecting changes in<br />

the electrical and acoustic properties of the sediments. In<br />

coarse- rained sediments, the base ma almost coincide with<br />

0°C isot%erm. In fine gralned soil, the {reezint characteristics<br />

of the soil predominate and the base of t e Ice bearing<br />

permafrost may be several tens of meters above the 0°C<br />

Isotherm with an underlying transltl<strong>on</strong> layer (Osterkamp and<br />

Payne, 1981).<br />

59'm<br />

Geological Survey of Canada C<strong>on</strong>tributi<strong>on</strong> No. 43287<br />

994

Judge (1986) provided permafrost thickness values from<br />

borehole temperature measurements observed at explorator<br />

wells in the Mackenzie Delta and Arctic Islands al<strong>on</strong>g wit;<br />

interpretati<strong>on</strong> of down-hole eophysical logs. Figure 2<br />

adapted from Judge (1986) slows permafrost thickness<br />

c<strong>on</strong>tours in the Beaufort Sea c<strong>on</strong>tinental shelf and adjacent<br />

Tuktoyaktuk coastlands with c<strong>on</strong>tour intervals of 100 m. The<br />

greatest permafrost thickness, about 740 m occurs in northern<br />

Richards Island. The permafrost thickness drops sharply<br />

towards the west from 600 m to less than 100 m within a<br />

distance of 15-20 km with the lowest thickness occurring west<br />

of the Mackenzie River channel shown by the arrow. The<br />

thickness increases again in the SW corner of the map area.<br />

The gradient in permafrost thickness indicates the complex<br />

subsurface geology and Quaternary history in the area.<br />

channels and numerous smaller winding channels. Active<br />

sedimentati<strong>on</strong>, rapid coastal recessi<strong>on</strong> (typical rates of 1<br />

m/year have been observed) and c<strong>on</strong>stantly shifting river<br />

channels also characterize the area. Pleistocene sediments <strong>on</strong><br />

Richards Island c<strong>on</strong>sist of st<strong>on</strong>efree sands, silts and clays, silty<br />

clays being more comm<strong>on</strong> towards the north. During the<br />

Pleistocene, much of the Delta was covered by ice sheets;<br />

however, the northern part of the Delta was believed to have<br />

been unglaciated at least during the late Wisc<strong>on</strong>sinan<br />

Glaciati<strong>on</strong> (Forbes, 1980). i.e. for the last 40,000 years.<br />

Changes as great as 100 m in eustatic sea level during the<br />

glacial period resulted in l<strong>on</strong>g periods of emergence and<br />

submergence of the Delta. As areas of the Delta were<br />

unglaciated throughout the late Wisc<strong>on</strong>sin and subjected to<br />

low surface temperatures during periods of emergence,<br />

c<strong>on</strong>diti<strong>on</strong>s favoured the formati<strong>on</strong> of thick permafrost. Such<br />

c<strong>on</strong>diti<strong>on</strong>s have persisted In the Delta since deglaciati<strong>on</strong> over<br />

10,000 years ago.<br />

The distributi<strong>on</strong> and extent of permafrost in the Delta is<br />

however not simple. The presence of numerous water bodies<br />

(the sea, lakes and shifting river channels), the shoreline<br />

transgressi<strong>on</strong>, past periods of submergence and emergence,<br />

glaciati<strong>on</strong> and deglaciati<strong>on</strong> all c<strong>on</strong>tribute to make the<br />

permafrost distributi<strong>on</strong> rather complex. In the old Delta, the<br />

permafrost thickness varies from 90 to 700 m and the<br />

temperature ran es from -4 to -9°C (Judge, 1975). In the<br />

modern Delta, tte sedimentatt<strong>on</strong> is active with frequent<br />

spring flooding. The permafrost thickness ranger from 0 to<br />

80 m and the temperature isslightly below 0°C.<br />

DESCRJPTION OF THE SYSTEM AND FIELD PROCEDURES<br />

Fig. 2<br />

C<strong>on</strong>tours of permafrost thickness in metres in the<br />

Mackentie Delta and Beaufort Sea C<strong>on</strong>tinental<br />

Shelf (after Judge, 1986). The arrow indicates the<br />

Mackenzie River channel crossing the profile.<br />

Transient EM soundings were made al<strong>on</strong>g a line so as to<br />

obtain detailed informati<strong>on</strong> about the variati<strong>on</strong> of<br />

permafrost thickness in the area. The pur ose of the survey<br />

was to determine if the chan e in permatost thickness was<br />

gradual from west to east or ifthere was an abrupt change in<br />

permafrost thickness at any locati<strong>on</strong>. In the case of the latter<br />

possibility, determinati<strong>on</strong> of the exact locati<strong>on</strong> of the abrupt<br />

change was the other purpose of the survey. Seventeen<br />

soundings were d<strong>on</strong>e <strong>on</strong> a line oriented at N64"E at an<br />

average separati<strong>on</strong> of 1.5 km (Fi ure 1). The first sounding<br />

was d<strong>on</strong>e about 7.5 km WSW 03 the hole Niglintgak B-19<br />

(69"18.2'N, 135"18.3'W) west of the Mackenzie River channel<br />

where the permafrost was 173 m thick. This stati<strong>on</strong> is<br />

designated as Stati<strong>on</strong> 1 while Stati<strong>on</strong> 17 is the easternmost<br />

sounding point. The eastern end of the linended just south<br />

of Big Lake, about 1 km east of the drillhole Taglu C-42<br />

(69'21'N, 134'56.6'W) where the permafrost thickness was<br />

over 600 m. It was hoped that systematic determinati<strong>on</strong> of<br />

permafrost thickness <strong>on</strong> this line would help understanding<br />

the subsurface geology which might be resp<strong>on</strong>sible for such<br />

abrupt changes in permafrost thickness.<br />

An EM-37 transient EM system, built by Ge<strong>on</strong>ics Ltd, Tor<strong>on</strong>to<br />

was used for the survey. The system c<strong>on</strong>sisted of a n<strong>on</strong>rounded<br />

square loop transmitter lyin flat <strong>on</strong> the surface. A<br />

%rge current with equal time-<strong>on</strong> an3 time-off was passed<br />

through the loop. The loop size varied from 450 m by 450 m to<br />

70 m by 70 m as detailed below. The lar er loop was used for<br />

deep soundings while the data from t\e smaller loop was<br />

used to obtain greater resoluti<strong>on</strong> at shallower depths. The<br />

receiver c<strong>on</strong>sisted of a small multi-turn coil that allowed<br />

measurement of voltage decay in three orthog<strong>on</strong>al directi<strong>on</strong>s<br />

during the time-off period at various time intervals or<br />

channels after the current Is turned off. For sounding work,<br />

<strong>on</strong>ly the decay of the vertical comp<strong>on</strong>ent of the induced<br />

magnetic field at Its centre of the transmitter was measured.<br />

The system has been described in detail by Sinha and Stephens<br />

(1983).<br />

A sharp terminati<strong>on</strong> of the current flowing through the<br />

transmitter induces eddy currents to flow in the ground in<br />

accordance with Faraday's law. These time-varying eddy<br />

currents diffuse laterally and vertically at a rate determined<br />

by resistivity and thickness parameters of the ground. The<br />

sec<strong>on</strong>dary magnetic fields produced by the eddy currents are<br />

measured by the receiver at the centre of the loop.<br />

It can be shown that a s stem with a square loop transmitter<br />

and a receiver coil at tKe centre IS equivalent, in the time<br />

range employed, to a system c<strong>on</strong>sisting of a magnetic dipole<br />

transmitter and an electric dipole receiver separated by a<br />

distance R equal to Ufi, where L is the length of the side of<br />

the square loop. This allows for use of all theories developed<br />

for the latter case while using the first set-up in the field.<br />

GEOLOGY OF THE AREA During survey, the skidoos were used for laying of<br />

transmitter loop and for movement, in general. At least two<br />

The Big Ldw drea located SO km west of Tuktoyaktuk in the transmitter loop<br />

sizes were used at each stati<strong>on</strong>. The larger<br />

Mackenzie River Delta is a low coastal area extendin over loop size was 300 m square west of the river channel where<br />

15.000 km2 and covered by unc<strong>on</strong>solidated Pleistocene iuvial, the permafrost was thinner and 450 m square east of the<br />

deltaic and estuarine sediments up to 100 m thick over much channel where permafrost was thicker, for sounding to<br />

of the Celta (Mackay. 1963). The regi<strong>on</strong> is dotted with depths of 300 m and 600 m respectively. A smaller loop was<br />

thousands of lakes and dissected by a network of several large used at each stati<strong>on</strong> to obtain detailed informati<strong>on</strong> at shallow

depths. The site of the smaller loop varied from 70-75 m<br />

square west of the channel to 150 m square to the east. Two<br />

base frequencies of 30 and 3 Hz were used with the system<br />

permitting measurement of decay voltages at 30 channels up<br />

to a maximum of 70 ms after the current turnroff. The<br />

currents in the loop varied from 22-23 A for the larger loops<br />

and 25-27 A for the smaller loops.<br />

A correcti<strong>on</strong> for the finite turn-off time of the current was<br />

applied to the measured decay volta es since the theory was<br />

based <strong>on</strong> an instantaneous turn-ojf. The turn-off time<br />

depends <strong>on</strong> the area of the loop and the current, and may be<br />

read from the transmitter c<strong>on</strong>sole. The corrected decay<br />

voltages are c<strong>on</strong>verted to apparent resistivity using equati<strong>on</strong><br />

(3) assumin late time c<strong>on</strong>diti<strong>on</strong>s. The late time, defined as<br />

the time wfen the induced current distributi<strong>on</strong> becomes<br />

invariant with time, appears relatively quickly in the resistive<br />

<strong>on</strong>shore envir<strong>on</strong>ments. The field data are plotted <strong>on</strong> double<br />

log sheets with apparent resistivity Pa in the ordinate and<br />

square root of time <strong>on</strong> abscissa.<br />

sediments are extremely c<strong>on</strong>ductive, the early time behaviour<br />

may persist for many channels. Since the late time<br />

commences at ~1/R>10, it is easy to show that the time of<br />

measurement must satisfy the relati<strong>on</strong>.<br />

H2<br />

1> -<br />

2 105<br />

A,PPARENT RESISTIVITY CONCEPT<br />

Although the decay of the vertical magnetic field comp<strong>on</strong>ent<br />

at the centre of the transmitter loop depends <strong>on</strong> the resistivity<br />

and thickness of the subsurface layers, the decay pattern itself<br />

is not sufficiently diagnostic for interpretati<strong>on</strong>. Hence, as in<br />

most EM systems, the field results are normally presented in<br />

terms of apparent resistivity. Ehrenbard et al (1983) illustrated<br />

the advantage of presenting the results in terms of apparent<br />

resistivity.<br />

Figure 3 shows a plot of the apparent resistivity pa of a<br />

homogeneous medium normalized by its true resistivity p,<br />

against the parameter TI/R where<br />

pa<br />

I<br />

4<br />

10.0<br />

T, =<br />

(1)<br />

is a measure of the depth of explorati<strong>on</strong>, t is the time after<br />

turn-off and R is the equivalent distance between transmitter<br />

and the receiver.<br />

1.0<br />

At early time, defined by rt/R

-<br />

ID<br />

0<br />

I<br />

C 600-<br />

f<br />

a<br />

0<br />

4<br />

Fig. 4<br />

100"<br />

Stati<strong>on</strong> 1<br />

300 x300m Loop<br />

Stati<strong>on</strong> 15<br />

460 x480m LOOP<br />

* x * * "<br />

Computed Data -<br />

Field Data Y Y Y<br />

1 1 1 :<br />

201nm<br />

73.3rn<br />

2.2nm 169.6m<br />

7.4nm<br />

BOOnm<br />

122nm<br />

8.70m<br />

20 I I<br />

lo-= 2 4 6 8 10" 2<br />

(Decay tlme)l'2 in (aec)1'2<br />

Plats of field data at stati<strong>on</strong>s 1 and 15 in the form<br />

of apparent resistivity versus square root of time<br />

and their interpretati<strong>on</strong> in terms of a layered<br />

ground.<br />

depth of 73.3 m, below which a c<strong>on</strong>ductive la er (2.2 nm),<br />

presumably an unfrozen clay layer exists. A srightly more<br />

resistive layer (7.4 Qm) appears at a depth of 232.8 m. From<br />

the resistivity value, the bottom layer appears to be an<br />

unfrozen silt or sandst<strong>on</strong>e horiz<strong>on</strong> c<strong>on</strong>taining salt water.<br />

From Young and McNeill (1984). the sec<strong>on</strong>d and third layers<br />

could be the Nuktuk and Beaufort formati<strong>on</strong>s c<strong>on</strong>sisting of<br />

mud and clay for the former and ravel, sand and mud for the<br />

latter formati<strong>on</strong>. At stati<strong>on</strong> 15, &e apparent resistivity curve<br />

looks quite different. Although a thin c<strong>on</strong>ductive layer<br />

(30 nm) detected at a depth of 103 m is possibly unfrozen, the<br />

main c<strong>on</strong>ductive horiz<strong>on</strong> occurs at a much greater depth of<br />

593 m. Although there are no drill holes near this stati<strong>on</strong>, drill<br />

hole C-42 located about 1.5 km to the east of stati<strong>on</strong> 15 has a<br />

permafrost thickness of over 600 m according to temperature<br />

measurements. The discrepancy between the two figures may<br />

be explained by the fact that the ice-b<strong>on</strong>ded permafrost<br />

thermal generally logs thaws because at a of shallower the presence depth of than electrolytes, predicted but their<br />

by<br />

temperatures may still be below 0°C. The geological secti<strong>on</strong><br />

within the permafrost transects mudst<strong>on</strong>e and sandst<strong>on</strong>es of<br />

the Beaufort formati<strong>on</strong>.<br />

Figure 5 shows the composite interpretati<strong>on</strong> of the EM<br />

soundings <strong>on</strong> the line. At each stati<strong>on</strong>, the data from the<br />

large and small loops were -ointly interpreted such that the<br />

interpreted model satisfies both sets of data. No sounding<br />

was d<strong>on</strong>e at stati<strong>on</strong> 6 <strong>on</strong> the river channel because of<br />

logistical problems. Figure 5 shows that the permafrost<br />

distributi<strong>on</strong> <strong>on</strong> the line falls into two distinct categories. West<br />

of the river channel (stati<strong>on</strong> 5), the permafrost is relatlvely<br />

thin, generally less than 100 m, underlain by unfrozen<br />

sediments. The unfrozen sediments can be divided into two<br />

distinct layers, possibly indicating two different sediment<br />

types, e.g. clay and sand. East of the river channel, the<br />

permafrost thickens, increasing in thickness from 265 m at<br />

DISTANCE FROM STATION 1 (km)<br />

0 P.0 4.0 1.0 8.0 10.0 12.0 14.0 18.0 18.0 20.0 22.0 24.0 21.0<br />

I I I<br />

0<br />

100<br />

200<br />

n<br />

E 300<br />

Y<br />

r<br />

F<br />

n<br />

400<br />

600<br />

800<br />

700<br />

Fig. 5<br />

Composite interpretati<strong>on</strong> of the survey profile in Big Lake area. The resistivities of the layers are indicated in nm.<br />

997

stati<strong>on</strong> 7 to about 675 m at stati<strong>on</strong> 16, bey<strong>on</strong>d which the<br />

thickness drops to 513 m at stati<strong>on</strong> 17. An interesting feature<br />

at all soundin stati<strong>on</strong>s east of the river channel is the<br />

presence of a &in layer of unfrozen sediments close to the<br />

surface. The layer is thickest under stati<strong>on</strong> 12 where it is<br />

about 125 m thick and more resistive than at nearby stati<strong>on</strong>s.<br />

Thisthin unfrozen layer may reflect a z<strong>on</strong>e which had thawed<br />

either due to the proximity of warm lakes or rivers or cover by<br />

a former extensive lake and subsequent slow refreezing after<br />

drainage of that lake.<br />

The thickness of the permafrost increases abruptly between<br />

stati<strong>on</strong>s 7 and 8 but stays reas<strong>on</strong>ably uniform east of stati<strong>on</strong> 8.<br />

At some of the stati<strong>on</strong>s, the sounding curves were greatly<br />

distorted perhaps implyin the presence of lateral<br />

inhomogeneities such as talifs forming two- and threedimensi<strong>on</strong>al<br />

bodies instead of simple horiz<strong>on</strong>tal layers. This<br />

could again be due to the very complex recent geological<br />

history of the area resulting in very irregular boundaries.<br />

A similar transient EM survey was carried out <strong>on</strong> a N-S line in<br />

1983 (Rozenberg et al, 1985) SW of Big Lake. One of their<br />

sounding stati<strong>on</strong>s was located about 1 km WSW of stati<strong>on</strong> 16.<br />

Rozenberg et a1 (1985) interpreted the permafrost thickness<br />

at their stati<strong>on</strong> to be 670 m which agrees well with our<br />

interpretati<strong>on</strong> of 675 m at stati<strong>on</strong> 16. However, they did not<br />

report detecting any unfrozen sediments close to the surface<br />

at that stati<strong>on</strong>, although they reported detecting unfrozen<br />

material at a depth of 30 m, 400 m south of that stati<strong>on</strong>. Thus,<br />

there is good agreement between their interpretati<strong>on</strong> and<br />

our results in that area.<br />

CONCLUSIONS<br />

Deep transient EM soundings were carried out <strong>on</strong> a 25 km<br />

l<strong>on</strong>g line southwest of the Big Lake in the Mackenzie Delta,<br />

N.W.T., to obtain detailed informati<strong>on</strong> where borehole<br />

temperature measurements indicated a sharp change in the<br />

permafrost thickness. The permafrost was rather thin west of<br />

the Mackenzie River channel which forms the present<br />

boundary between the modern and the old delta. East of the<br />

channel, the permafrost thickness was much reater, of the<br />

order of 500 m or more from 2 km east 07 the channel<br />

<strong>on</strong>ward.<br />

At five sounding stati<strong>on</strong>s west of the river channel, the<br />

permafrost was never more than 100 m thick. Below the<br />

permafrast, two c<strong>on</strong>ductive layers were detected which could<br />

be unfrozen clay and sandy sediments. To the east of the<br />

cha.nne1, an abrupt change in permafrost thickness was noted<br />

at stati<strong>on</strong> 7, less than a km from the eastern edge of the river<br />

channel, where it was 265 m. The thickness increased to 560<br />

m at stati<strong>on</strong> 8, 1.5 km further east from stati<strong>on</strong> 7 and stayed<br />

reas<strong>on</strong>ably uniform further east. A thin, shallow unfrozen<br />

layer was also detected at all stati<strong>on</strong>s east of the channel. This<br />

layer increased in thickness 8 to 10 km east from the river<br />

channel where the sounding curves were rather distorted.<br />

The bottom unfrozen sediments east of the channel were<br />

quite c<strong>on</strong>ductive (3-10 rim), sug esting the presence of<br />

unfrozen clays, mixtures of clay antsilt or the presence ofsalt<br />

water in the pores.<br />

The success of the EM survey in delineatin the subsurface<br />

c<strong>on</strong>diti<strong>on</strong>s in this area down to depths of 780 m proves that<br />

such techniques can be used in mapping the distributi<strong>on</strong> of<br />

permafrost in areas where permafrost thickness may change<br />

rapidly. This type of survey may be extended to offshore areas<br />

with minor changes in equipment although the depth of<br />

investigati<strong>on</strong> may be somewhat reduced because of the<br />

presence of highly c<strong>on</strong>ductive near-surface materials.<br />

ACKNOWLEDGMENTS<br />

The author wishes to thank his colleagues L.E. Stephens and<br />

D. Gresham of the Geological Survey of Canada and Perry<br />

Lanthier of the former Earth Physics Branch for help in<br />

carrying out the field survey and preliminary interpretati<strong>on</strong> of<br />

the data. Thanks are also extended to Polar C<strong>on</strong>tinental Shelf<br />

Pro'ect for providin logistical help during the field program<br />

and to the office oathe Energy <strong>Research</strong> and Development,<br />

EMR, for partial1 financin the field work. Dr. A.S. Judge of<br />

GSC sug ested tte idea opcarrying out EM soundings in the<br />

area anjcritically read this manuscript.<br />

REFERENCES<br />

Anders<strong>on</strong>, W.L. (1982). N<strong>on</strong>linear least-squares inversi<strong>on</strong> of<br />

transient soundin s for a central inducti<strong>on</strong> loop system<br />

(Program NLSfC8. Open-File report 82-1 129, U,S.<br />

Geological Survey, 35 p.<br />

Annan, A.P. and Davis, J.L. (1976). Im ulse radar sounding<br />

in permafrost. Radio Science, v. 11 h , 383-394.<br />

Daniels, J.J., Keller, G.V. and Jacobs<strong>on</strong>, J.J. (1976).<br />

Computer-assisted interpretati<strong>on</strong> of electromagnetic<br />

soundings over a permafrost secti<strong>on</strong>. Geophysics, 41,<br />

752-765.<br />

Ehrenbard, R.L., Hoekstra, P. and Rotenberg, G. (1983).<br />

Transient electromagnetic soundings for permafrost<br />

map ing Proc. 4th Int. C<strong>on</strong>f. <strong>on</strong> <strong>Permafrost</strong>, Nati<strong>on</strong>al<br />

AcackmyPress, Washingt<strong>on</strong>, DX., 272-277.<br />

Forbes, D.L. (1980). Late Quaternary,sea levels in the<br />

Southern Beaufort Sea. Current <strong>Research</strong>, Paper 80-18,<br />

Geological Survey of Canada, 75-87.<br />

Hoekstra, P. and McNeill, J.D. (1973). Electromagnetic<br />

probing of permafrost. in <strong>Permafrost</strong> -- The North<br />

American C<strong>on</strong>tributi<strong>on</strong> to2nd Int. C<strong>on</strong>f., Yakutsk,<br />

Washingt<strong>on</strong>, D.C., 517-526.<br />

Hoekstra, P., Sellmann, P.V. and Delaney, A. (1975).<br />

Ground and airborne resistivity surveys of permafrost<br />

near Fairbanks. Alaska. Geophysics, v. 40 (4), 641-656.<br />

Judge, A.S. (1975). Geothermal studies in the Mackenzie<br />

Valley by the Earth Physics Branch. Geothermal. Series<br />

No. 2, Geothermal Service of Canada, 12 p.<br />

Judge, A. (1986). <strong>Permafrost</strong> distributi<strong>on</strong> and the<br />

quaternary history of the Mackenzie-Beaufort regi<strong>on</strong>: A<br />

geothermal perspective. Open-File Report 1237,<br />

Geological Survey of Canada, 41-45.<br />

Koziar, A. and Strangeway. D.W. (1978). <strong>Permafrost</strong><br />

mapping by audio frequency magnetotelluric. Can. J. of<br />

Earth Sclences, v. 15. 1535-1 546.<br />

Mackay, J.R. (1963). The Mackenzie Delta Area, N.W,T.<br />

Geographical Branch Memoir No. 8, Dept. of Mines and<br />

Technical Surveys, Canada.<br />

Olhoeft, G. (1975). The electrical properties of permafrost.<br />

Ph.D. thesis, University of Tor<strong>on</strong>to, Tor<strong>on</strong>to, Canada.<br />

Osterkamp, T.E. and Payne, M.W. (1981). Estimates of<br />

permafrost thickness from well logs in northern Alaska.<br />

Cold Regi<strong>on</strong>s Science and Technology, v. 5,13-27.<br />

998

Rossiter, J.R., Strangwa D.W., Koziar, A., W<strong>on</strong>g, J. and<br />

Olhoeft, G.R. (19%). Electromagnetic sounding of<br />

permafrost. Proc. 3rd Int. C<strong>on</strong>f. <strong>on</strong> <strong>Permafrost</strong>, v. 1,<br />

Ottawa, Nati<strong>on</strong>al <strong>Research</strong> Council of Canada, 567-572.<br />

Rozenber , G., Henders<strong>on</strong>, J.D., Sartorelli, A.N. and Judge,<br />

A.S. 19~~~. Some aspects of transient electromagnetic<br />

soundings for permafrost deltneati<strong>on</strong>. Workshop <strong>on</strong><br />

<strong>Permafrost</strong> Geophysics, CRREL Special Rep. 85-5 (J.<br />

Brown, M.C. Metr and P. Hoekstra ed), 74-90.<br />

Sartorelli, A.N. and French, R.B. (1982). Electromagnetic<br />

inducti<strong>on</strong> methods for mapping permafrost al<strong>on</strong>g<br />

northern pipeline corridors. Proc. 4th Canadian<br />

<strong>Permafrost</strong> C<strong>on</strong>f, Nati<strong>on</strong>al Res. Council of Canada,<br />

Ottawa, 283-295.<br />

Sinha, A.K. and Stephens, L.E. (1983). Deep<br />

electromagnetic soundin over the permafrost terrain in<br />

the Mackenzie Delta, NfV.T., Canada. Proc. 4th Int.<br />

C<strong>on</strong>f. <strong>on</strong> <strong>Permafrost</strong>, Washingt<strong>on</strong>, D.C.; Natl<strong>on</strong>al<br />

Academy Press, 1166-1171.<br />

Taylor, A.E., Burgess, M., Judge, AS. and Allen, V.S. (1982).<br />

Canadian geothermal data collecti<strong>on</strong> - Northern wells,<br />

1981. Geothermal Series No. 13, Earth Physics Branch,<br />

154 p.<br />

Young, F.G. and McNeill, D.H. (1984). Cenozoic<br />

stratigraph of the Mackentle Delta, Northwest<br />

Territories. gulletin 336, Geological Survey of Canada,<br />

63 p.<br />

999

MAPPING AND ENGINEERING-GEOLOGIC EVALUATION OF KURUMS<br />

A.I. Tyurin, N.N. Romanovsky and D.O. Sergeyev<br />

Faculty of Geology, Moscow State University, Moscow, USSR<br />

mmI6<br />

Over the last 10 to 15 years rock streams are more frequently used or treated<br />

a0 a pmbable base for engineering structures. The present paper Is based <strong>on</strong> the data obtained<br />

from the studies of the Transbaikal bald mountain belt- where rock streams occupy more than a half<br />

of the slo e &Tea and are diatiaguished by large ais9 and complex structure due to gsostructural<br />

peculiaritPei, of near-surface solid rocks, altitudhal permafrost ana climatic z<strong>on</strong>ality, ana epecific<br />

fea.t;umes of the eubsuTface water flow. !Phe author8 have propoaed the methods for mapping<br />

stable paragenetic complexes of facies (rock stream, deluvial soliflucti<strong>on</strong>, etc.) occurring in a<br />

certain area termed "slope segment". Features, which are facjes of slope formati<strong>on</strong>s, are identified<br />

as c<strong>on</strong>venti<strong>on</strong>al. unite within slope Be ents as a result of engineering-geological analyeis.<br />

By the c<strong>on</strong>labiaati<strong>on</strong>s of the peculiarities &the structure and movement mechanisms, the features<br />

are subdivided into four groups depending <strong>on</strong> the lnaeafd for engineering development. Based <strong>on</strong><br />

the studies of the Paaturels the principles of Slope segment evaluati<strong>on</strong> have been developed to<br />

aid in ohoosrslg a proper mehod for laying a roadbed and working out a set of engineering measures<br />

to achieve safe road operati<strong>on</strong>, The procedures which have bean elaborated are embodied In the<br />

maps of tmgbeering-geologic c<strong>on</strong>diti<strong>on</strong>s and engineering-geo~ogical evaluati<strong>on</strong>.<br />

For about; 200 gears rock streame (kurums) have<br />

be- attracting attenti<strong>on</strong> of scientists. Over<br />

the last 10-15 years rock stmama are more and<br />

more often c<strong>on</strong>sidered as a base for various<br />

eeiaeerlng projectis. It should be noted that<br />

the problem of a<strong>on</strong>structing OIL rock rstreams<br />

has alwayer existed. Bullders treated and c<strong>on</strong>tinue<br />

to treat rock streame aa a oomph% and<br />

incomprehensive phenomen<strong>on</strong>, trgiag to by-pase<br />

them. In the majority of cases such a practice<br />

was a lsuccess because 80 far, <strong>on</strong>ly re i<strong>on</strong>s<br />

with rock streams of iimited extent haf bean<br />

developed. Avoidance of rock streams bevitably<br />

incurred additlcraal expenditures. At<br />

present, when high-mountain regi<strong>on</strong>s where<br />

rock streamar occupy up to 60 percent of' the<br />

area are being developed it is impossible to<br />

pass them around and c<strong>on</strong>structi<strong>on</strong> <strong>on</strong> them is<br />

inevitable.<br />

The present paper is based <strong>on</strong> the data obtalnd<br />

from the studies of rock streams in the baldmouutain<br />

belt of the Transbaikal regi<strong>on</strong>. The<br />

authors have experience of rock-stream investigati<strong>on</strong><br />

in South Yakutiya based <strong>on</strong> the cryofacies<br />

analyeis. Rock streams in this area are<br />

formati<strong>on</strong>s limited in extent from Dome tena ta<br />

a few hundred meters. They occur mainly <strong>on</strong> tb<br />

sides of valleys cut in plateaus and have disthct<br />

belts of mobilizati<strong>on</strong> transit and accumulati<strong>on</strong><br />

of clastic mated. The rock streams<br />

in the Transbaikal mountaha are dlfferent;<br />

their features are as Pollows t (1) they<br />

are large and extended down slope; (2) series<br />

of altexnatbg rock streams, often deferent<br />

in morphology and genesis are located, as a<br />

rule, <strong>on</strong> every slope; (3) there is no distlnct<br />

dFPPerenti<strong>on</strong> of rock stream belts (of mobilizati<strong>on</strong>,<br />

transit ma accumulati<strong>on</strong>). One rack<br />

stream cover may be incorporated Fnto the mobilinati<strong>on</strong><br />

belt of the other. This pattern<br />

sometimes complicated by several accumudive<br />

belts, may repeatedly occur <strong>on</strong> a slope; (4)<br />

due to a large altitude gradient, a rock-stream<br />

slope is frequently characterized by climatio<br />

and geocryologlc altftudbal s<strong>on</strong>ality ; and<br />

(5) complex geostruct ural c<strong>on</strong>d it i<strong>on</strong>s (topography,<br />

diverse and cloea $0 the surface aolid<br />

rock bedding, fault and block tect<strong>on</strong>ics etc.)<br />

that lead to complicated paragenetic c<strong>on</strong>necti<strong>on</strong>s<br />

of rock streams and thelr associati<strong>on</strong><br />

with different types of erogenetic processes<br />

and phenomena.<br />

The golats listed above require a larger scope<br />

of methods and procedures as compared with<br />

pmviously used in studying rock streams.<br />

The Btudies of rock streams in the Transbaikal<br />

regi<strong>on</strong> have ahown that in different part6 of<br />

the mountains they are dlfferentlg distributed<br />

and duffer significadtly in morphology, In<br />

additi<strong>on</strong>, rock streams have been found to be<br />

paragenetically related to cerbain types of<br />

slope formati<strong>on</strong>s (accumulati<strong>on</strong>s) Cosequently ,<br />

we have c<strong>on</strong>ducted (1) special geomorphological<br />

mapping to etudy in detail the slopes depend<strong>on</strong><br />

the neotect<strong>on</strong>ic setting, glacial phenomena<br />

in the Pleistocene, as well a8 compositi<strong>on</strong> and<br />

geostructural features of bedrock; and (2)<br />

special mappiq of the Quaternary fornati<strong>on</strong>s<br />

c<strong>on</strong>nected paragenetically with rock streams<br />

deserptium. It hae been established that Quaternarg<br />

fomati<strong>on</strong>a of eluvial, colluvia1,glacia1<br />

and even aquatio series may (a) serve<br />

a8 a subatratum for the formati<strong>on</strong> of rockstream<br />

deserptium; (b) be c<strong>on</strong>nected perageneticall7<br />

with the latter, formkg alternating

areas; and (c) exclude the presence of mckstream<br />

desergtium. It has also been established<br />

that mck-stream deserptium itnelf may<br />

serve a basis for the formati<strong>on</strong>.of other enetic<br />

types of Quaternary deposits. These %; indings<br />

allowed us to compile a Wap of Rock<br />

Streamstt based <strong>on</strong> a special map of Quaternarg<br />

deposits . It represents in detail elope formati<strong>on</strong>s<br />

and especially various mck stream<br />

facies and thelr combinati<strong>on</strong>s. The nsab tax<strong>on</strong>omic<br />

unit of rock stream that wa8 distinguished<br />

a d studied in the course of special geolo<br />

ical surveys was a rock stream facies. The<br />

foflowing rock stream facies were identified<br />

by comm<strong>on</strong> morpholo and orientati<strong>on</strong> of' the '<br />

procesees that dbgacea and transformed rudaceouB<br />

material.: Ylowa of rock streams1', netlike<br />

rock streams, rock-stream ~lopes,.as well<br />

as complicated combinati<strong>on</strong>s of Plow rock strean<br />

forms with areal aaea; Therefore, at the<br />

first stage of studies or rock-stream facies,<br />

three large morphological groups of sockatream<br />

forma were identified$ (I) isometrio;<br />

(2) Linear (flow); and (3) net-like. Each<br />

comprise6 different facies dietFnguisbed by<br />

individual morphological peculiarities of the<br />

rock stream body and occurrence in various<br />

relief forms. This is due to the fact that<br />

the morphology of rock streams is predetermined<br />

b their genesis. Geostructural features of<br />

stopes are also very important. fhese axe:<br />

(1) presence of duf erent khds of fructum<br />

systeme and tect<strong>on</strong>oc fxagmentati<strong>on</strong> s<strong>on</strong>es;<br />

(2) lithoological peculiarikiee of rock6 and<br />

orientati<strong>on</strong> of geologic layefs relative to the<br />

slopee; (3) slope steepness and evoluti<strong>on</strong>;<br />

(4) dimensi<strong>on</strong>s of the drainage system and the<br />

associated slope inundati<strong>on</strong>; (5) preesnce of<br />

external sources of rock stmame; and (6) the<br />

type of unc<strong>on</strong>solidated sediments which semed<br />

as a background for rock streams development.<br />

With this in view, rock-stream facies within<br />

morphological groups were identified based <strong>on</strong><br />

an obligatory analysis of all the factors<br />

involved Fa rook-stream formati<strong>on</strong> directly <strong>on</strong><br />

the slope under study.<br />

The next stage of the work was mapping of rockstream<br />

facies. However, large-scale mapping<br />

of rock streams is impossible because of their<br />

, limited size. Many rock streams are <strong>on</strong>ly a few<br />

meters wide. Rock-stream facies alternate with<br />

,those of other slope deposits 'such as, for<br />

example , eluvial-deluvlal <strong>on</strong>es f omin a paragenetically<br />

related group of dope facfes. Buch<br />

groups occupy c<strong>on</strong>siderable parts of sl.opes corresp<strong>on</strong>ding,<br />

in the tax<strong>on</strong>omic series of landscapes,<br />

to the "facies associati<strong>on</strong>". The geometric<br />

forma gf the latter <strong>on</strong> the slope are<br />

often similar to segments; therefore in this<br />

paper they were c<strong>on</strong>diti<strong>on</strong>ally termed :'slope<br />

segments'*. Thus, a8 a result of a special geological<br />

Survey, it were not the boundaries of<br />

individual rock stream6 that have been identified<br />

and mapped but the paragenesee of Slope<br />

Pormati<strong>on</strong>a, including also the groups of rock<br />

stream facies.<br />

Within the slope segments identified, the percentage<br />

of areas occupied by their c<strong>on</strong>atituent<br />

faales was determined. The map shows the rock<br />

stream llcoverage" (percentage) tn a %egment".<br />

which was shaaed in color correap<strong>on</strong>ding to the<br />

rock fitream genesis W it covered more than 50<br />

percent of the segment's area or to the type<br />

100 I1<br />

of alope deposits prevalent in this llse@entll.<br />

An engineering-geological predicti<strong>on</strong> of the<br />

interacti<strong>on</strong> between a rock stream azl4.a road<br />

al<strong>on</strong>g the entire rock stream slope is not yet<br />

feasible. Within the limits of slope segmen*s,<br />

an engbeerlng-geological analysis enabled<br />

identificati<strong>on</strong> of c<strong>on</strong>diti<strong>on</strong>al units or features.<br />

Most f requsatly , these are rock stream facies<br />

or other types of slope formati<strong>on</strong>s, They can<br />

alao be repreaented by rock stream subfacies,<br />

i.e. by smaller units but still-of c<strong>on</strong>siderable<br />

size. The identificati<strong>on</strong> of such featurea<br />

wa~<br />

based up<strong>on</strong> the Iollowfng faetora:<br />

(1) thickness of the xudaceous cover and its<br />

relati<strong>on</strong> to the depth of the seaamally thawing<br />

layer (STTI); (2) preaence or absence of a baldmountain-ice-c<strong>on</strong>taining<br />

horiz<strong>on</strong> and its thicknessv1<br />

(3) sins and shape of rock Pragments,and,<br />

main4 the degree of thelr mLlndness# (4) density<br />

ot the structiure ("packing**) of the ,ruaaceaus<br />

cover; (5) presence of a layer 09 bundated,<br />

thlxOtPOgiC fine-grahed material in<br />

the basement of the ST5 and/or the same material<br />

in a perennially froBen state; (6) presence<br />

of water OJsw from the STL in the rock<br />

stream body in'summer; and (7) slope steepness.<br />

$0 evaiuate the stability of a eegment feature,<br />

obaexvati<strong>on</strong>e were c<strong>on</strong>duoted of the behavior<br />

of engineering structures and of the mgheering-geological<br />

processes and phnomena Fnduced<br />

bg tha. We could than predict mdesixable<br />

displacements of the rock stream cover<br />

under the impact of road c<strong>on</strong>structi<strong>on</strong>, auoh as:<br />

allding of the rudaceous cover down the iceground<br />

base; plastic .deformati<strong>on</strong> of the baldmauntab<br />

ice layer; its partial or complete<br />

tha~blng aad associated subsidence; viscoplastic<br />

deformati<strong>on</strong>s of the fine-earth lager;<br />

the cover deformati<strong>on</strong>s caused by the hydrodynamic<br />

head of the SfL waters; and fine-earth<br />

suffoei<strong>on</strong> and gravitati<strong>on</strong>al diaplacaments. Begments<br />

with an areal or stream-like (c<strong>on</strong>centrated)<br />

patterns of the rudaceous cover movement<br />

have been distbguished. Tphe order of the<br />

rates of--movement arid amounts of material displaced<br />

have been evaluated.9or the both, depending<br />

<strong>on</strong> slope steepness rudaceoua cover<br />

thiclmssa, and quality of h e displacemetit curface<br />

in natural c<strong>on</strong>diti<strong>on</strong>s and. those of slope<br />

cutting," . By-the rspecjfice of structure and mecanisms<br />

.of moti<strong>on</strong>, the features of rock stream<br />

slopes are subdivzded into four groups as Co<br />

the extent of hazard associated with their engineer-ing-geological<br />

development: safe, comparatively<br />

aafe, hazardous and extremely hazardous<br />

The safe type of rock stream features and other<br />

slope foxmati<strong>on</strong>s is characterized by a fairlg<br />

atable s,tate of the rudaceous cover; absence<br />

of c<strong>on</strong>diti<strong>on</strong>s fox its catastmphic displacements<br />

due to alope cuttings absence of debris<br />

movement; , and rates of movement, if any, that<br />

do not exceeding a few millimeter6 a year.<br />

C<strong>on</strong>structi<strong>on</strong> of roads <strong>on</strong> such rock streams is<br />

safe.<br />

The comparatively safe type of rock stream features<br />

is characterized by the fragments with<br />

bald-mountain ice of insignificant thicbess<br />

(up to 0.3 m); unc<strong>on</strong>solidated structure of<br />

debris Fn the rudaceous cover, etc. Roads

c<strong>on</strong>structed <strong>on</strong> these rock stream features experience<br />

the impact of the rudaceous material<br />

that moves at a rate of up to several mm a<br />

year. Insignificant, decreasing with time,<br />

sibsidence of the roadbed caused by the c<strong>on</strong>solidati<strong>on</strong><br />

of the cover and by thawing of ice<br />

lenses also occurs. Rudaceous material fallouts<br />

with a volume of several. cubic metem are<br />

possible when hollows are cut in a slope. All<br />

the unfavorable c<strong>on</strong>sequences, incurred through<br />

natural and man-hduced processes, can be elimlnated<br />

in the course of routine roaawq exploitati<strong>on</strong>.<br />

The hazardous type of rock-stream features ia<br />

characterized by a complex structure and presence<br />

of a 1-2 m-thick bald-mountain ice layer<br />

or a layer of water-saturated thixotropic fineearth<br />

(0.5 and more m-thick) at the base of<br />

the rock stream. On the whole, the rudaceous<br />

cover moves at a rate of 1-3 cm per year. Natural<br />

causes (rabfall, hot summer bringing<br />

about an increase in STL depth, seismic phenomena,<br />

etc.) as well as engineering activity<br />

can give rise to catastrophic movements 00 the<br />

rudaceous cover with diaplacemanta am0Unthg<br />

to several tens of cubic metem. Themoerosim<br />

scour^, thermokarst subsidence and other undesirable<br />

phenomena, disturbing the stabilit of<br />

structures and requiring specialized cost 9 y<br />

repair work, are also possible. Secti<strong>on</strong>s of<br />

roade built <strong>on</strong> such rock-stream features ctu<br />

experience c<strong>on</strong>siderable subsidence, be washed<br />

out, and blocked up with rudaceous material,<br />

stoppiag normal traffic for a cerOain period<br />

of time, The extremely hazardous type of rockstreem<br />

features is distinguished by 8 2-3 and<br />

more m-thick ice-ground layer and great rates<br />

of the audaceous cover movement reaching several<br />

tans of cm per year. Large catastrophic<br />

movementgl with debris displacements amounting<br />

to several metem are also possible. A secti<strong>on</strong><br />

of the road built <strong>on</strong> such a slope feature<br />

may be completely destroyed as a result of catastrophic<br />

phenomena associated with thawing<br />

or washing out of the ice-ground layer at the<br />

base of the roamed. These phenomena can develop<br />

wiCh time and disrupt the use of the<br />

road for a l<strong>on</strong>g period. Meaauree aimed at<br />

preventi<strong>on</strong> and eliminati<strong>on</strong> of the above phenomen8<br />

demand heavy investments and, j~ a number<br />

of cases, do not guarantee the desired safety.<br />

It should be noted that undisturbed rock-stream<br />

slopes rarely preserve traces of active gro-,<br />

cessea. This seeming stability of rock streams<br />

is a result of l<strong>on</strong>g-term geological proceasas<br />

producing an equilibrium profile. However,<br />

specific permafrost-faciea structure of rock<br />

streme makes them rather wtable if they are<br />

disturbed by c<strong>on</strong>6tructi<strong>on</strong> work. It is clearly<br />

maniPe8ted when mine workings are made in rock<br />

streams .<br />

Thus, an engineering-geological evaluati<strong>on</strong> of<br />

different kinds of rock streams made by the<br />

authors can be used in road designing and<br />

c<strong>on</strong>structi<strong>on</strong>. Nevertheless, the choice of road<br />

variant8 requires compilati<strong>on</strong> of an evaluati<strong>on</strong><br />

map. But rock-stream features, because of<br />

their amall size, cannot be plotted <strong>on</strong> such a<br />

map. That is why it kas been deemed reas<strong>on</strong>able<br />

to evaluate slope segments as a Whole from the<br />

engineering-geological standpoint. Large-scale<br />

studies of slope segments have proved that in<br />

1002<br />

engineerkg development they vary by preferable<br />

methods of Lay 'Lng roadbeds (<strong>on</strong> shelves,<br />

in semi-hollows- semiembankments, in embankments)<br />

and also require different sets of engineer&<br />

measures for their c<strong>on</strong>structi<strong>on</strong> and<br />

safe operati<strong>on</strong>, It ahould be emphasized that<br />

segments can c<strong>on</strong>tain, in dsfferent combhati<strong>on</strong>s,<br />

features of all four roup distinguished<br />

by complexity (hazard) for development.<br />

To c<strong>on</strong>struct a road reliably and operate it safely,<br />

preliminary recommendati<strong>on</strong>s aimed at<br />

carrying out a number of engineering reclamati<strong>on</strong><br />

measures and/or engineering protecti<strong>on</strong> of<br />

various structures built <strong>on</strong> the most hazardous<br />

porti<strong>on</strong>s of slope8 have been worked out. Taking<br />

into account the complexity of the above<br />

described work and eng,Sneersg-profecti<strong>on</strong> meaeurm,<br />

slope segments have been subdivided into<br />

four categories! favorable, c<strong>on</strong>diti<strong>on</strong>ally<br />

favorable, unfavorable and extremely unfavorable<br />

for road c<strong>on</strong>structi<strong>on</strong>. The categorg of<br />

slope segments is an indirect indicati<strong>on</strong> of<br />

relative expences needed for lay Fng a road<br />

within their limits.<br />

Prom the engineering-geological viewpoint, a<br />

method of road c<strong>on</strong>structi<strong>on</strong> is of no principal<br />

significance for the slope segments bel<strong>on</strong>ging<br />

to the first, favorable category since no spacific<br />

reclamati<strong>on</strong> measures and atrucfufes are<br />

required to ensure engineering protecti<strong>on</strong> of<br />

roads.<br />

Laying a roadbed <strong>on</strong> the slope segments of the<br />

sec<strong>on</strong>d, c<strong>on</strong>diti<strong>on</strong>ally favorable for road<br />

c<strong>on</strong>structi<strong>on</strong> and operati<strong>on</strong> category requires<br />

selecti<strong>on</strong> of a preferable method (shelf, embankment)<br />

and .determinati<strong>on</strong> of an optimum slope<br />

cutting depth in accordance with the rock<br />

stream structure and rudaceous cover thickness<br />

(Fig.1). A new drahage system must also be<br />

envisaged or the natural <strong>on</strong>e presaIue8. This<br />

can be d<strong>on</strong>e by laying girder floors over the<br />

hollows c<strong>on</strong>centrating subsuflace flow, by<br />

creatbg over them a coarse-fragmental llcushl<strong>on</strong>r1<br />

to preserve the rudaceous cover from colmatage,<br />

or by other methods.<br />

The third unfavorable category of slope segments<br />

includes those features c<strong>on</strong>structi<strong>on</strong> <strong>on</strong><br />

which does not ensure safety and durability of<br />

structures and their c<strong>on</strong>tinuous operati<strong>on</strong> without<br />

preliminaq removal or stabiliBati<strong>on</strong> of<br />

the rudaceous cover (Fig.2). In every c<strong>on</strong>crete<br />

case different reclamati<strong>on</strong> measures should be<br />

recommended. A set of such measures usually<br />

LncorporateB stabilizati<strong>on</strong> of the rudaceous material<br />

of rock streams, its removal and layFng<br />

drainage pipes into the formed hoLlOw8 or<br />

filling them with rubble-gravelly material.<br />

Other engineering measures cao be employed.<br />

The fourth category comprises slope segments<br />

which are extremely unfavorable for development.<br />

It includes rock-stream facies as well as glaciers<br />

and rock-stream glaciers. The rudaceous<br />

cover removal or stabilizati<strong>on</strong> will not ensure<br />

the stability of structures or their normal.<br />

operati<strong>on</strong> <strong>on</strong> such slope segments (Fig.3) and<br />

c<strong>on</strong>structi<strong>on</strong> will trigger off extremely unfavorable<br />

engineering-geologic processes (powerful<br />

thermokarst aubsidence, themoerosi<strong>on</strong>,etc.).<br />

Ln additi<strong>on</strong>, the rudaceous cover removal or<br />

reliable stabilizati<strong>on</strong> <strong>on</strong> such rock streams is

Fig.2 A slope segment of the &avorab3.e<br />

category with fan-shaped rock<br />

streams. Gymbola a$ in Pig.1<br />

Fig.1<br />

A slope segment of the c<strong>on</strong>ditio-<br />

nally favorable categoq with the rockatream<br />

cover of a heaved rock 1 - blocky<br />

material <strong>on</strong> a rock-stream suflace; 2 -<br />

rubble-blocky material. in the cross-secti<strong>on</strong><br />

of a rock stream; 3 - rubble-blocky material<br />

of rounded shape Fa the croas-secti<strong>on</strong><br />

of a rock Stream; 4 - unc<strong>on</strong>solidated rudaceous<br />

formati<strong>on</strong>s with a fine-grained fill5<br />

5 fractured solid rock ("rock in fragmentsi%<br />

6 - bald-mountah ice with aolid rock frag-<br />

7 - the upper boundayy of perenni-<br />

ments;<br />

ally f roaen rocks.<br />

frequently impracticable due to c<strong>on</strong>siderable<br />

slope steepness and great thicEmesB of rudaceous<br />

formati<strong>on</strong>s or bald mountain ice.<br />

The unfavorable man-fnduced processes occurring<br />

' <strong>on</strong> rock-stream slopes due to slope cutting include<br />

c<strong>on</strong>centrated water flows from the STL.<br />

In the period of anow melting and in the autumn<br />

when air temperature often passes O°C the STL<br />

waters form <strong>on</strong> the road surface 20-30 cmthick,<br />

small in area and volume icings. On<br />

ateep roads such iclngs can make the movement<br />

of wheeled vehiclea not <strong>on</strong>ly difficult and<br />

dangerous but completely impossible.<br />

An analysis of engineering-geological characteriatics<br />

of slopes and natural processes occurring<br />

<strong>on</strong> them coupled with the predicti<strong>on</strong> of<br />

the possible man-induced processes have allowed<br />

us to compile a "Map of engheesing-geologfc<br />

c<strong>on</strong>diti<strong>on</strong>s'' and a "Map of engbeerhg-geological<br />

evaluati<strong>on</strong>". The former representa all<br />

the specific features of the structure of rock<br />

streams and their dynamics, whereaa the latter<br />

1003<br />

..<br />

Big.3 A slope segment of the extremely -<br />

unfavorable categorg with fan-shaped cover<br />

rock streams. Symbols as in Fig.<br />

characterizes the category of slope segments<br />

from the engineerFng-geological stmapoht.<br />

If such maps are fairly simple they can be combhed<br />

Fnto <strong>on</strong>e map.

DEVELOPMENT AND THAWING OF ICE-RICH PERMAFROST AROUND'<br />

CHILLED PIPELINES MONITORED BY RESISTANCE GAUGES<br />

B.O. Van Everdingen and L.E. Carls<strong>on</strong><br />

The Arctic Institute of North America, Calgary, Canada T2N 1N4<br />

L.E.C. Engineering Ltd., Calgary, Canada T2K 4R5<br />

SYNOPSIS<br />

Data from electrical-resistance freezing gauges installed al<strong>on</strong>gside three<br />

test secti<strong>on</strong>s of chilled, buried pipeline show development of frost bulbs around the pipes;<br />

development of increasing ice c<strong>on</strong>tents with time; and,proqressive melting of excess ice and thawing<br />

of the-ground after the shutdown of chilling.<br />

INTRODUCTION<br />

The Calgary Test Site<br />

In early 1974, the Calgary Frost Heave Teat<br />

Facility was c<strong>on</strong>structed by Canadian Arctic Gas<br />

Study Ltd., to study the potential development<br />

of frost heave around chilled, large-diameter<br />

pipelines buried in unfrozen, frost-susceptible<br />

Soils. The initial installati<strong>on</strong> c<strong>on</strong>sisted of<br />

four pipe secti<strong>on</strong>s (CONTROL, GRAVEL, DEEP-<br />

BURIAL and RESTRAINED), each 1.22 m in diameter<br />

and 12.2 m l<strong>on</strong>g, through which refrigerated air<br />

at atmospheric pressure could be circulated at<br />

a temperature of about -12'C. Additi<strong>on</strong>al<br />

details of the test installati<strong>on</strong>, site layout,<br />

and smaries of teat results can be found in<br />

Slusarchuk et a1.(1978) and Carls<strong>on</strong> et al.<br />

(1982). The latter presented an interpretati<strong>on</strong><br />

of the heave history to the end of 1980.<br />

Operati<strong>on</strong> of the test site started <strong>on</strong> 20 March<br />

1974. The CONTROL secti<strong>on</strong> was removed in the<br />

fall st 1977. The facility was taken over by<br />

Foothills Pipe Lines Ltd. at the end of 1977.<br />

Two additi<strong>on</strong>al insulated pipe ecctians were<br />

activated in February 1979. Chilling was<br />

disc<strong>on</strong>tinued <strong>on</strong> 24 February 1986 and shortly<br />

thereafter the DEEP-BURIAL secti<strong>on</strong> was<br />

excavated to enable insp6cti<strong>on</strong> of the frost<br />

bulb around the pipe. The remainder of the<br />

facility was dismantled in October 1986.<br />

Resistivity Measurements<br />

Installati<strong>on</strong> of electrical-resistance freezing<br />

gauges in the test site was to serve two<br />

purposes. First, the test site provided an<br />

excellent oggortuni'ty for testing the l<strong>on</strong>g-term<br />

performance of this type of freesing detactor.<br />

As at least some excess ice could be expected<br />

to form in the frost bulbs around the chilled<br />

pipe secti<strong>on</strong>s, the test site also presented a<br />

chance to establish whether the growth af icerich<br />

permafrost would be reflected in a gradual<br />

increase in measured resistance values.<br />

FREEZING GAUGES<br />

astrumentati<strong>on</strong><br />

Three freezing gauges of the Type 11 variety<br />

described by Banner and van Everdingen (1979)<br />

were c<strong>on</strong>structed as shown in Figurt 1.<br />

kl<br />

Fig. 1 Freezing gauge c<strong>on</strong>structi<strong>on</strong> (after<br />

Banner and-van Everdingen, 1979).<br />

1 - soldered wire stubs; 2 - galvanized<br />

steel pipe couplings; 3 - threaded PVC<br />

nipples: 4 - c<strong>on</strong>necting wires.Yo'ints<br />

waterproofed with Tefl<strong>on</strong> tape.<br />

L - effective electrode interval.<br />

1004

Each gauge carried 52 electrodes, with gaps<br />

between adjoining electrodes varying from 10 to<br />

126 mm (effective electrode interval L varying<br />

from 60 to 176 mm). The lengths of the gauges<br />

ranged from 3.93 to 4.58 m. A special 72-Hz<br />

Wheatst<strong>on</strong>e bridge with phase-sensitive detector<br />

and automatic gain c<strong>on</strong>trol was used to measure<br />

resistance between pairs of adjoining<br />

electrodes <strong>on</strong> each gauge.<br />

The freezing gauges were installed beside three<br />

of the original buried pipe secti<strong>on</strong>s (CONTROL,<br />

GRAVEL, and DEEP-BURIAL). Each gauge was<br />

positi<strong>on</strong>ed 1.2 m from the pipe centre line, <strong>on</strong><br />

the same side of the pipe as the prime<br />

thermistor string, but 2.9 m closer to the cold<br />

inlet end of the pipe.<br />

Readings were taken approximately weekly from<br />

26 February 1974 until 7 October 1977;<br />

m<strong>on</strong>itoring was resumed in May 1985 and<br />

c<strong>on</strong>tinued until late September 1986, to cover<br />

the period proceeding and following the shutdown<br />

of the chilling plant.<br />

Data C<strong>on</strong>versi<strong>on</strong><br />

Readings from the three-digit readout <strong>on</strong> the<br />

ten-turn balancing potentiometer of the<br />

Wheatst<strong>on</strong>e bridge were c<strong>on</strong>verted to resistance<br />

values, using the calibrati<strong>on</strong> curve for the<br />

instrument. Apparent resistivity values (r) in<br />

ohm.metres were then calculated using the<br />

equati<strong>on</strong><br />

r = (R * A) / (100 * log L) 111<br />

where R is measured- resistance in ohms, A is<br />

electrode surface area in cm2, and L is the<br />

effective electrode spacing in mm (see Fig.1).<br />

Equati<strong>on</strong> [L] is based <strong>on</strong> the results of tests<br />

using various electrode spacings in c<strong>on</strong>tainers<br />

filled with saturated soil material from the<br />

test site, and in a water-filled column,<br />

15<br />

DISCUSSION OF RESULTS<br />

As the freezing gauge installed in the GRAVEL<br />

secti<strong>on</strong> provided the most complete record of<br />

changes in resistivity during the operati<strong>on</strong> of<br />

the test site, the results from this gauge are<br />

used as the basis for this discussi<strong>on</strong>.<br />

Resistivity vs. time curves for selected<br />

electrode intervals from 0.10 m above to 1,77 m<br />

below the base of the pipe, for the two periods<br />

of observati<strong>on</strong> (1 March 1974 to 7 October 1977;<br />

9 May 1985 to 28 September 1986), are shown in<br />

Figures 2 and 3, respectively. Resistivity vs.<br />

depth curves are shown in Figure 4 for selected<br />

dates between 1 March 1974 and 24 February 1986<br />

(terminati<strong>on</strong> of chilling), and in Figure 5 for<br />

selected dates during the thaw period. The<br />

progress of initial freezing from 0.20 m above<br />

to 1.77 m below the base of the pipe, and the<br />

progress of complete thawing in the interval<br />

from 1.26 m above to 0.62 m below the base of<br />

the pipe, are shown in Figures 6 and 7,<br />

respectively, together with O'C points for the<br />

prime thermistor string.<br />

As expected, the effects of seas<strong>on</strong>al variati<strong>on</strong>s<br />

in temperature (and in moisture c<strong>on</strong>tent in the<br />

soil) <strong>on</strong> resistivity were extreme €or the upper<br />

few electrode intervals, but they were<br />

gradually attenuated with depth. The sudden<br />

sharp rise in resistivity for each of the<br />

deeper electrode intervals some time after the<br />

start of chilling <strong>on</strong> 20 March 1974 (Fig.2)<br />

reflects the <strong>on</strong>set of freezing and the<br />

development of the frost bulb around the<br />

chilled pipe. After the initial rapid increase,<br />

resistivity values c<strong>on</strong>tinued to rise mora<br />

slowly for some time, reflecting the gradual<br />

decrease in unfrozen Water c<strong>on</strong>tents as<br />

temperatures dropped farther below O'C.<br />

301 .. I<br />

1985 I 1986<br />

I t I I<br />

I I I IT I<br />

0<br />

0 10<br />

0<br />

r<br />

X<br />

E<br />

E<br />

c 5<br />

0<br />

L-<br />

0<br />

Days after start-up, x100<br />

Days after start-up, x 100<br />

Fig. 2 Resistivity vs. time during freezing,<br />

for electrode intervals centred at:<br />

0 +0.10 m; 4 -0.51 m; 0 -0.93 m;<br />

A -1.20 m; X -1.42 m; V -1.77 m,<br />

relative to the base of the pipe.<br />

Fig. 3<br />

Resistivity vs. time during thawing,<br />

for electrode intervals centred at:<br />

0 tQ.10 m; + -0.51 m; 0 -0.93 m:<br />

A -1.20 m; x -1.42 m; v -1.77 m,<br />

relative to the base of the pipe.<br />

1005

Fig. 4<br />

r, ohmam x 1000<br />

Resistivity vs. depth during freezing<br />

<strong>on</strong>: 0 1 Parch 1974: + 9 May 1974;<br />

0 24 Sept. 1974: 4 30 April 1975;<br />

x 9 May 1985: D 24 Febr. 1986.<br />

Fig. 5<br />

r, ohmam x 1000<br />

Resistivity va. depth during thawing<br />

<strong>on</strong>: + I4 April 1986: 0 27 June 1986;<br />

4 25 July 1986; x 29 Aup. 1986;<br />

b 28 Sept. 1986.<br />

al<br />

P<br />

m<br />

v1 +1<br />

al<br />

.-<br />

n<br />

P<br />

r O<br />

-<br />

0<br />

al<br />

P,<br />

Q<br />

><br />

n<br />

0 -1<br />

m<br />

E I I I 7 1 1 1 1 1 1 1 1<br />

Fig. 6<br />

lb '<br />

Days after start-up, x 100<br />

Penetrati<strong>on</strong> of freezing vs. time.<br />

Black dots: arrival of O'C isotherm,<br />

based <strong>on</strong> thermistor readings.<br />

The larger than average increases in<br />

resistivity for some of the electrode intervals<br />

(e.g curve C in Fig.2; Fig.4) arc interpreted<br />

as indicative of either the formati<strong>on</strong> of<br />

segregated ice and ice lenses or, close to the<br />

pipe, the lower unfrozen water c<strong>on</strong>tents caused<br />

by lower temperatures. The general increase in<br />

resistivity values during the period between<br />

October 1977 and May 1985 (days 1297 and 4068,<br />

Figs.2 and 3) is interpreted as reflecting the<br />

formati<strong>on</strong> of additi<strong>on</strong>al segregated ice.<br />

'<br />

I I 1 I I I<br />

4'0 45<br />

Days after start-up, x 100<br />

Fig. 7<br />

Penetrati<strong>on</strong> of thaw vs. time.<br />

Black dots: arrival of O'C isotherm,<br />

based <strong>on</strong> thermistor readings.<br />

The sharp temporary drop in resistivity shown<br />

by curves A and B in Figure 2 around day 288<br />

reflects a rise in soil temperature, and hence<br />

unfrozen water c<strong>on</strong>tent, caused by a temporary<br />

shut-down of the chilling plant betcen<br />

Christmas and New Year's Eve 1974. The effect<br />

of the shutdown extended from 1.97 m above to<br />

1.26 m below the base of the pipe. Two similar<br />

dips in resistivity shown by the same curves <strong>on</strong><br />

days 1177 and 1241 (Fig.2) probably have a<br />

similar origin. In those instances the effects<br />

extended from 1.26 m above to 0.65 m below the<br />

1006

60<br />

1985 ' 1986<br />

for the gauge in the GRAVEL secti<strong>on</strong>. Maximum<br />

resistivity values were somewhat lower in the<br />

CONTROL secti<strong>on</strong>, and somewhat higher in the<br />

DEEP-BURIAL secti<strong>on</strong>, compared with those for<br />

the QRAVEL secti<strong>on</strong>. In the DEEP-BURIAL secti<strong>on</strong>,<br />

the effect of the chilling-plant shut-down<br />

extended to a depth of 1.16 m below the base of<br />

the pipe within 24 hours.<br />

Days after start-up, x 100<br />

Fig. 8 Precipitati<strong>on</strong> at the University of<br />

Calgary weather stati<strong>on</strong> near the test<br />

site,for the period 9 May 1985 to 28<br />

September 1986.<br />

base of the pipe. A rrharp, short-lived dip in<br />

resistivity is also shown by curve A in Figure<br />

3 around day 4198 (15 September 1985). It<br />

followed a two-day rainfall of 95 m <strong>on</strong> I1 and<br />

12 September 1985 (Pig.8). The effect extended<br />

from 0.55 m above to 0.29 m below the base of<br />

the pipe. As the resistivity at and near the<br />

ground surface was not noticeably affectod it<br />

is likely that the cause was a wheather-related<br />

refrigerati<strong>on</strong> problem, rather than the<br />

infiltrati<strong>on</strong> of rainwater.<br />

The effect of the shut-down of the chilling<br />

plant <strong>on</strong> day 4359 extended to a depth of 0.8 m<br />

below the base of the pipe within 24 hours<br />

(Fig.3). For the electrode intervals between<br />

1.2 m above and 0.8 m below the base of the<br />

pipe, resistivity values dropped at a gradually<br />

decreasing rete (reflecting decreasing thermal<br />

gradients), which accelerated suddenly into a<br />

steep drop from some value betwe<strong>on</strong> 5000 and<br />

2000 0hm.m to the range for unfrozen soil<br />

(between 100 and 500 0hm.m). The time lag<br />

between the arrival of the O'C isotherm and the<br />

apparent completi<strong>on</strong> of thawing between 1.3 and<br />

0.5 m above the base of the pipe, indicated in<br />

Figure 7, may have been due to a lack of water<br />

saturati<strong>on</strong> in that porti<strong>on</strong> of the soil until<br />

after the rainstorms of 28 and 29 June 1986<br />

(days 4403 and 4484, Fig.8).<br />

Several of the intervals more than 0.8 m below<br />

the base of the pipe showed increases in<br />

resistivity after 15 Auqust 1986 (day 4530;<br />

curves C and D in Pig.3; curves E and F in<br />

Fig.5). The <strong>on</strong>ly tentative explanati<strong>on</strong> that can<br />

be offered for this phenomen<strong>on</strong> at this time is<br />

that some of the water released during warming<br />

of the frozen soil (below O'C) may have moved<br />

and then refrozen to be incorporated into<br />

several of the existing ice lenses,<br />

The patterns of changes in resistivity revealed<br />

by the freezing gauges in the CONTROL and PEEP-<br />

BURIAL secti<strong>on</strong>s are similar to that shown here<br />

CONCLUSIONS<br />

Electrical-resistance freezing gauge8 provide a<br />

practical means for m<strong>on</strong>itoring of bath natural<br />

and man-induced ground freezing.<br />

The <strong>on</strong>set of freezing is indicated by a sudden<br />

rapid increase in the measured resistance (and<br />

thus resistivity) values for individual<br />

electrode intervals.<br />

Gradual reducti<strong>on</strong> of the unfrozen water c<strong>on</strong>tent<br />

of the soil due to decreasing temperatures<br />

after initial frsazing is reflected by a slower<br />

further increase in resistivity. This effect is<br />

str<strong>on</strong>gest close to the chilled pipe.<br />

Progressive development of segregated ice in<br />

the soil is indicated by larger than average<br />

increases in resistivity.<br />

Thawing is indicated by a retu,rn of the<br />

resistivity to values for unfroeen soil. During<br />

thawing the resistivity drops at an initially<br />

rapid, but gradually decreasing rate.<br />

Although variable electrode spacing complicates<br />

data c<strong>on</strong>versi<strong>on</strong>, it may be attractive in<br />

certain applicati<strong>on</strong>s.<br />

ACKNOWLEDQEMENTS<br />

Canadian Arctic Qas Study Ltd., Canada<br />

Department of the Envir<strong>on</strong>ment, Foothills Pipe<br />

Lints Ltd., and Canada Department of Energy,<br />

Mines and Resources have c<strong>on</strong>tributed to various<br />

aspects of this study at various times.<br />

REFERENCES<br />

Banner, J.A., b van Evordingen, R.O. (1979).<br />

Frost gauges and freeeing gauges. Inland<br />

Waters Directorate, Envir<strong>on</strong>ment Canada,<br />

NHRI Paper No. 3, 18 pp,<br />

Carls<strong>on</strong>, L.E., Ellwood, J.R., Nix<strong>on</strong>, J.F. &<br />

Slusarchuk, W.A. (1982). Field test<br />

results of operating a chilled, buried<br />

pipeline in unfroaen ground. Proc. 4th<br />

Can. <strong>Permafrost</strong> C<strong>on</strong>f., Nati<strong>on</strong>al <strong>Research</strong><br />

Council of Canada, Ottawa, 475-480.<br />

Slusarchuk, W.A., Clark, J.I., Nix<strong>on</strong>, J.F.,<br />

Morgenstern, 1.R. & Gaskin, P.N. (1978).<br />

Field test results of a chilled pipeline<br />

buried in unfrozen ground. Proc. 3rd<br />

Int. C<strong>on</strong>f. <strong>Permafrost</strong>, Nati<strong>on</strong>al <strong>Research</strong><br />

Council of Canada, Ottawa, (I), 877-883,<br />

1007

THE ORIGIN OF PATTERNED GROUNDS IN N.W. SVALBARD<br />

B. Van Wet-Lanoe<br />

Centre de Chmorphologie du C.N.R.S., Rue des Tilleuls - 14000 Csen, France<br />

SYNOPSIS - Different theories exist c<strong>on</strong>cerning the cryoturbati<strong>on</strong> process. This paper develops and<br />

dem<strong>on</strong>strates that the dynamics of the most frequently occuring patterned grounds results from differential<br />

frost heave. This differential heave is by c<strong>on</strong>trolled<br />

1) the drainage and thermal c<strong>on</strong>diti<strong>on</strong>s and<br />

2) the gradient and the c<strong>on</strong>trast of frost susceptibility. Loadcasting and cryostatic pressures are<br />

strictly restricted to poorly drained soils characterized by an unstable cryogenic as fabric pure (suc<br />

silts or silty sand textures) <strong>on</strong> a base of permafrost or shallow bedrock. are The normally other s<br />

stable. The translocati<strong>on</strong> of fine particles during melting can promote frost susceptibility in<br />

n<strong>on</strong>susceptible coarse material. Most of the patterned grounds and cryoturbati<strong>on</strong>s can be easily explaine<br />

by the frost susceptibility gradient related to the prevailing drainage c<strong>on</strong>diti<strong>on</strong>s.<br />

INTRODUCTION<br />

Most studies of periglacial phenomena, either<br />

active or relict, are usually restricted to the<br />

most evident features. But the most comm<strong>on</strong>, albeit<br />

hidden process acting, in a cold envir<strong>on</strong>ment is<br />

ice lensing. Ice lensing is the motor of frost<br />

heave mainly c<strong>on</strong>trolled by the drainage and the<br />

thermal gradient ; for these reas<strong>on</strong>s, it is the<br />

basis to periglacial deformati<strong>on</strong>s (i.e. cryoturbati<strong>on</strong>s),<br />

both <strong>on</strong> slopes and <strong>on</strong> flat topography.<br />

The drainage c<strong>on</strong>diti<strong>on</strong>s under which patterned<br />

ground and cryoturbati<strong>on</strong>s can develop is rarely<br />

correctly studied in active c<strong>on</strong>diti<strong>on</strong>s. Although - HALVOYA"<br />

<strong>on</strong>e can ready find displacement measurements in<br />

the litterature, it is very difficult to find<br />

informati<strong>on</strong> <strong>on</strong>, fox example the autumn positi<strong>on</strong> of<br />

the water table. It is the reas<strong>on</strong> why we have made Fig. 1 - Locati<strong>on</strong> map of the investigated sites related with<br />

a detailed mapping of patterned ground, the late<br />

the different qlaciomarine deposits : holocene<br />

summer c<strong>on</strong>diti<strong>on</strong>s in Svalbard being close very to (u<strong>on</strong>tinuous hatching) and preholocene (broken hatching)<br />

those prevailing at the of <strong>on</strong>set the frost seas<strong>on</strong>.<br />

The cryogenic aggregati<strong>on</strong> or fabric of sediments<br />

THE ROLE OF DRAINAGE QUALITY<br />

resulting from ice lensing is important because Because it topography and lithology give a range of<br />

is resp<strong>on</strong>sible far the enhancement or inhibiti<strong>on</strong> both periglacial patterned ground and drainage<br />

of various mechanisms such as load casting by c<strong>on</strong>diti<strong>on</strong>s, its a small area located to the Gisebu<br />

behaviour (stability) during either or of the both house <strong>on</strong> the northern slope of the Bragger<br />

melt and or the freeze-back seas<strong>on</strong>s. This is<br />

Peninsula was mapped in detail at a reduced scale.<br />

expressed mainly in the form of induced modifi- The sediments and topography result mainly from<br />

cati<strong>on</strong>s of the hydraulic c<strong>on</strong>ductivity. It has been the early holocene history (Corbel, 1961 ; about<br />

menti<strong>on</strong>ed in active forms by soil scientists. A 9000 y. BP) with some recent (t 80 years) aeolian<br />

micromorphological approach (petrographical deposits (Van Vliet & HGquette, 1987). Dolomitic<br />

analysis of c<strong>on</strong>solidated undisturbed soft sam- limest<strong>on</strong>e bars enclose glacio-marine deposits,<br />

ples) allows easy recogniti<strong>on</strong> of the traces andl which form fossil islands in the K<strong>on</strong>gsfjord, now<br />

more specifically, of the locati<strong>on</strong>s of the ice stranded by prograding Atlantic sandur (Brossard &<br />

lenses. This approach permits us :<br />

Joly, 1986). Other sites were also investigated,<br />

1 ) identificati<strong>on</strong> of the annual sequence of<br />

Kvadehuksletta, the Stuphallet , flat Ox%hytta and<br />

plastic soil deformsti<strong>on</strong>s related to frost, and<br />

the mining sector of Ny Alesund, but <strong>on</strong>ly from a<br />

the translocati<strong>on</strong> of particles during melt,<br />

dynamical approach.<br />

2) identificati<strong>on</strong> of the progressi<strong>on</strong> of the<br />

Drainage classes were adapted (Van Vliet. 1983) to<br />

freezing fr<strong>on</strong>t by the successive positi<strong>on</strong>s of<br />

freezing<br />

the<br />

soils ; they are different from those of<br />

ice lenses, c<strong>on</strong>secutive to differences inmoisture<br />

the Soil Survey Manual (1965) because the autumn<br />

c<strong>on</strong>tent related to textural compositi<strong>on</strong>,<br />

positi<strong>on</strong> of the water table and rhe thermal<br />

gradient c<strong>on</strong>trol the intensity and the shape of<br />

3) and identificati<strong>on</strong> of the dominant mechanism frost heave. Knowledge of the spring and summer<br />

behind cryoturbati<strong>on</strong> related to the stability of positi<strong>on</strong>s of the water table is inrelevant because<br />

the cryogenic fabric.<br />

most Arctic soils are waterlogged during the melt

Fig. 2 - Superficial drainage map of the dsebu sector, Brcgger Peninsula Svalbard - la/b. active-inactive beaches ;<br />

2, aeolian sand ; 3. sandur ; 4. morainic arc ; 5. permanent p<strong>on</strong>d ; 6. frost heaved blocks ; 7. cliff ; 8. moderately drained,,;<br />

9, imperfectly drained ; IO. poorly drained ; 12-13. moderately to imperfectly drained brackish soils ;<br />

14. limest<strong>on</strong>e outcrop ; 15. investigati<strong>on</strong> sites ; 16. thermal recording stati<strong>on</strong> ; 17. buildings<br />

seas<strong>on</strong> and drained in summer. Textural c<strong>on</strong>diti<strong>on</strong>s This relati<strong>on</strong>ship between drainage and related<br />

depend up<strong>on</strong> both the level of capillary rise in morphology have also been observed at other si<br />

sediment, its mineralogical compositi<strong>on</strong>, its in the Bragger and also in the lower Advental.<br />

organic c<strong>on</strong>tent and its cryogenic fabric (interag- has also been recently c<strong>on</strong>firmed by Walker (1985,<br />

gregate porosity ; Van Vliet, 1983, 1985).<br />

N.W. Canada).<br />

Five drainage classes were defined (table 1 ) :<br />

CRYOTURBATION DYNAMICS IN GASEBU<br />

In the first three classes, microrelief remains<br />

flat. The most comm<strong>on</strong> patterned ground forms are<br />

The lithostratigraphic units affected by cryoturrelated<br />

to class 3, in sediment with an autumn<br />

bati<strong>on</strong> in this site c<strong>on</strong>sist basically of recent<br />

water c<strong>on</strong>tent close to the field capacity or<br />

aeolian stratified fine sands, rather silty and<br />

slightly higher. On the other hand, if drainage<br />

humic, resting mainly <strong>on</strong> an early Holocene litimproves<br />

for topographic or other reas<strong>on</strong>s (textoral<br />

complexe whose stratigfaphy has been detailed<br />

elsewhere (Van Vliet & Hdquette, 1987).<br />

ture), low center forms can to evolve high centred<br />

<strong>on</strong>es as sounded by Zoltai & Tarnocai (1981).<br />

TABU I<br />

Drainage classes ' Morphology<br />

Shallow pound<br />

Palsas<br />

Poorly drained soil<br />

Flat mudboil or st<strong>on</strong>e<br />

with shallow water table circles, poorly expressed<br />

at less than 5 cm in sands low centre polyg<strong>on</strong>s,heaved<br />

or with a surficial pF blocs<br />

value < 1<br />

Imperfectly drained soil<br />

with a capillary fringe<br />

allowing a stable field<br />

capacity in surface (1 <<br />

pF < 2.5, excepted in<br />

organics 1<br />

Moderately well drained<br />

soil with a capillary<br />

fringe allowing a stable<br />

field capacity at 50 cm<br />

in depth. surface pF is<br />

usually above 2.5<br />

well to extremely well<br />

drained soil ; no detectable<br />

water table. Profile<br />

<strong>on</strong>ly slightly humid,<br />

(normal surface pF > 3)<br />

Most of the patterned<br />

grounds associated with<br />

a flat microtopography<br />

Hummocky soils, high center<br />

patterned ground<br />

1009<br />

In the main profile (site A, fig. 2) three types of<br />

profiles exist : - fine stratified sand resting <strong>on</strong><br />

coarse sands and gravel ; - fine sand resting <strong>on</strong><br />

humic silts, a former paleosol existing at the top<br />

of the lower complex ; - fine sand resting <strong>on</strong> pink<br />

dolomitic silts resulting from the weathering an<br />

frost shattering of carb<strong>on</strong>iferous dolomitic<br />

limest<strong>on</strong>es. Those three facies coexist in the<br />

drainage c<strong>on</strong>diti<strong>on</strong>s in site A. The surface of the<br />

fine sand- is affected by a net of cryodesiccati<strong>on</strong><br />

fissures whose mesh ranges from 25 cm in poorly<br />

drained sites up to 50 cm in well drained <strong>on</strong>es. On<br />

this shallow net rests, a larger net of about 1 m<br />

of mesh seaming related to thermal cracking ; it is<br />

sensitive to the permafrost table, normally at a<br />

depth of 80 cm. C<strong>on</strong>tinuous thermal recording<br />

performed in this site during the years 1982-1983<br />

has shown 1 ) a water table positi<strong>on</strong> close to the<br />

base of surficial fine sand at the freeze-back<br />

seas<strong>on</strong> and 2) <strong>on</strong>ly <strong>on</strong>e effective freeze-thaw cycle<br />

each year.<br />

This site shows clearly the role of differential<br />

heave in the formati<strong>on</strong> of cryoturbati<strong>on</strong>s:<br />

a) The proximity of a water table in depressi<strong>on</strong>s<br />

influence differential frost heave 'of various<br />

textured sediments : the rigidity of frozen wet<br />

surficial horiz<strong>on</strong> induces a flat microrelief and<br />

obliges differential heave pressures to develop,<br />

mainly in a downward directi<strong>on</strong>. This induces<br />

injecti<strong>on</strong> of the unfrozen underlying sediment<br />

al<strong>on</strong>g weakness z<strong>on</strong>es : here in the two nets of<br />

fissures, normally open in late summer (Van Vliet,<br />

1983) as showp by presence in of it entire- leaves<br />

of dryas or willow, This injecti<strong>on</strong> occurs little<br />

by little, independent of the density or frost<br />

susceptibility gradients the of different layers :

~~ -<br />

I a) imperfectly drained I b) well drained -1<br />

POSITIVE<br />

FROST 'SUSCEPTIBILITY<br />

GRADIENT<br />

P 5pem imperfectly drained ,permafrost<br />

5Dcm ~<br />

&EGE_ND<br />

NEGATIVE<br />

al BOcm<br />

line/ caarse<br />

.,. ...<br />

Sands<br />

the slope - a. downslope : flat microtopography -<br />

b. upslope : hummocky microrelief<br />

H Y D W A U L I C R E G I M E<br />

"- 1<br />

-final<br />

initialsurface<br />

insulated lank<br />

'ig. 3 - a) Injecti<strong>on</strong>s and cryoturbati<strong>on</strong> in site A - Gisebu ;<br />

b) Injecti<strong>on</strong> experiment in Caen Laboratory<br />

(25 freeze-thaw cycles)<br />

we have observed at 50 m distance (fig. 3a)<br />

injecti<strong>on</strong>s of silts between prisms of fine sands<br />

in two profiles, although in another site it is the<br />

coarse sand which appears to be injected. These<br />

observati<strong>on</strong>s reduce c<strong>on</strong>siderably the importance<br />

of the load casting.<br />

This surface rigidity has been reproduced<br />

experimentally in the Caen laboratory, both in the<br />

presence of a slope and in the presence of a flat<br />

topography with an high water table (Van Vliet,<br />

1987a). This latter experiment, performed in a<br />

medium size cell (fig. 3b) , suggested that, in<br />

absence of weakness, injecti<strong>on</strong>s may not occur<br />

infine textured sediment <strong>on</strong> flat topography.<br />

Injecti<strong>on</strong>s were also produced by chance in an<br />

earlier experiment (Coutard & Mucher, 1985).<br />

b) At drained sites, the differential heave<br />

resulting from subtile differences in moisture<br />

c<strong>on</strong>tent related to the microrelief, to a discrete<br />

vegetati<strong>on</strong> cover as proposal by Willidms (1962),<br />

or more comm<strong>on</strong>ly to variati<strong>on</strong> of the texture and of<br />

the organic c<strong>on</strong>tent (Tsytovich, 1975 ; Van Vliet,<br />

1986). This differential heave enables the formati<strong>on</strong><br />

of hummocky microrelief as shown in figure<br />

4. Deformati<strong>on</strong> is different from that in poorly<br />

drained aera ; the prisms of fine sands defined by<br />

the desiccatiop net evolves to a rugby football<br />

shape ; infilling of the fissures,produces humic<br />

wedges, On the same slope, in the lowest z<strong>on</strong>e, this<br />

humic accumulati<strong>on</strong> deforms to a drop-like feature<br />

(fig. 4b).<br />

This style of deformati<strong>on</strong> may also be relevant at a<br />

larger scale, for example in the infill of trenches<br />

of large size polyg<strong>on</strong>es. The hummock relief<br />

results from the summati<strong>on</strong> of all the stresses<br />

accumulated during freezing (cryogenic fabric and<br />

differential heaving), at the outset of thawing<br />

(refreezing ice ; Mackay, 1983) and by desiccati<strong>on</strong><br />

in summer. This situati<strong>on</strong> is summarized in figure<br />

5. Notice that this sum of stresses is thc same as<br />

with gilga: formati<strong>on</strong> in swelling Clays (van<br />

Vliet, 1Y87a).<br />

c) On slope the deformati<strong>on</strong> of cryoturbati<strong>on</strong>s or<br />

hummocks are related to the drainage quality and<br />

frostcreep as shown in figure 6 (Van Vliet,<br />

1987b). Supplementary deformati<strong>on</strong>s are related to<br />

I<br />

1010<br />

ONSET OF THAW<br />

(refreezing ice1<br />

SUMMIM<br />

(c<strong>on</strong>tracti<strong>on</strong> by<br />

desiccati<strong>on</strong> )<br />

ION<br />

SUMMER<br />

Fig. 5 - Frost dynamics and geometry of stress leading the to<br />

occurence hummocky microrelief. <strong>Permafrost</strong> is not necessary<br />

1) imported matters ; 2) wet ; 3) moist ;<br />

4) dry ; 5 ) frozen + ice lenses<br />

L<br />

microslipping over ice lenses (Van Vliet, 1982)<br />

which are related to their abundance (Rein &<br />

Burrous, 1980 ; Mackay, 1983). In these c<strong>on</strong>diti<strong>on</strong>s,<br />

the desiccati<strong>on</strong> cracks evolve into pseudoshear<br />

planes.<br />

d) In thin secti<strong>on</strong>s, the injecti<strong>on</strong> patterns show<br />

clearly :<br />

1) Preservati<strong>on</strong> of traces of ice lenses after<br />

deformati<strong>on</strong>. They occur in both injecti<strong>on</strong>s or in<br />

hummocky soils and suggest the existence of<br />

internal pressure during the lowering of the<br />

freezing fr<strong>on</strong>t and an usual absence of liquefacti<strong>on</strong>,<br />

even in sand or silt (fig. 7, left),<br />

2) Thin secti<strong>on</strong>s also show that injected silts<br />

(rig. 7, right) present traces of ice lensing<br />

bending in the directi<strong>on</strong> of the less susceptible<br />

material.<br />

This is to be expected as the normal behaviour of<br />

freezing soils. Mcmreover, in this very unstable

_""<br />

rzIsI+rvP: GRADIENT NEGATIVE susceptibility<br />

Fig. 6 - Deformati<strong>on</strong> of cryoturbati<strong>on</strong>s and hummocks<br />

<strong>on</strong> slope. Gasebu sites<br />

material, traces of ice are still preserved. This<br />

situati<strong>on</strong> has also been reproduced experimentally<br />

in Caen.<br />

These observati<strong>on</strong>s show that ice lensing occured<br />

after the deformati<strong>on</strong>s induced by cryostatic<br />

pressures which, in turn, were created by differential<br />

heave. Liquefacti<strong>on</strong> and load casting<br />

were ineffective even in wet soils. The origin of<br />

cryoturbati<strong>on</strong> is not to be found in loadcasting<br />

theory as proposed by Cegh and Dzulinski ( 1967) I<br />

van Den Berghe an6 Vandenbroeck (1982) or Mackay<br />

(1983), although it could exist in some excepti<strong>on</strong>al<br />

c<strong>on</strong>diti<strong>on</strong>s favouring the destabilizati<strong>on</strong><br />

of the cryogenic fabric.<br />

THE FROST SUSCEPTIBILITY GRADIENT<br />

These observati<strong>on</strong>s enable <strong>on</strong>e to propose a new<br />

theory complementarytothatof differential frost<br />

heave, as proposed by Sharp in 1942, supported by<br />

the observati<strong>on</strong>s of Dylikowa (1961) and partially<br />

dem<strong>on</strong>strated by the. experiments of Corte (1972)<br />

and particularly those of Pissart ( 1982) In 1985<br />

we proposed this of frost susceptibility gradient.<br />

If surface material is more frost susceptible than<br />

underlying sediment (via difference in clay silt<br />

or organic c<strong>on</strong>tent), gradient will be positive ;<br />

here injecti<strong>on</strong>s are not able to reach the surface,<br />

but deform to a diapiric shape (fig. 9 because of<br />

the rigidity of the surface layer caused by frost.<br />

If the surface sediment is less susceptible than<br />

the underlying, the gradient is negative and the<br />

injected sediment heaves more rapidly than the<br />

surface layer ; it is able to burst through to the<br />

surface to form a mudboil as observed by Pissart<br />

(1976) <strong>on</strong> Banks Island (N.W.T. Canada).<br />

The observati<strong>on</strong>s made in the other sandy sites of<br />

the Brogger follow the same laws( Oxdshytta,<br />

Stuphallet, mining z<strong>on</strong>e of Ny Alesund) .<br />

This hypothesis, especially in the presence of a<br />

positive gradient, can be extended to explain<br />

c<strong>on</strong>tiguous st<strong>on</strong>e circles as the result of bedrock<br />

al<strong>on</strong>g cracking patterns (fig. 9 ).<br />

PATTERNED GROUND IN STUPHALLET AND KVAREHUK<br />

a) The imperfectly drained site of the Stuphallet<br />

shows a flat microtopography, In this place, a<br />

yellow lago<strong>on</strong>al dolomitic sand rests <strong>on</strong> a thin<br />

layer of glacio-marine gravel underlain by a red<br />

glacio-marine silty clay : this site presented<br />

initially a negative gradient of frost susceptibility.<br />

Irregularities in the surface of the clay red and<br />

these of thermal c<strong>on</strong>tracti<strong>on</strong>.cracks are similar to<br />

the Gasebu site, but <strong>on</strong> a larger scale. At the<br />

intersecti<strong>on</strong> of the cracks, red clay heaves and<br />

finally burst through surface the of the sand. The<br />

Fig. 7 - Relati<strong>on</strong> between (A) the successive locati<strong>on</strong>s<br />

the 0' C isotherms (theoretical) c<strong>on</strong>trolled by the frost<br />

susceptibility and (B) these of the ice lenses observed in<br />

thin secti<strong>on</strong>s. Dominant heave<br />

heaving of the red clay improves surficial drainage<br />

as shown by changes in lichen. Normally, a<br />

black cryptogamic crust covers the soil surface.<br />

When the clay reaches to within 25 cm of the<br />

surface, direct watersupply from the water table<br />

is stopped and the crust changes to grey lichen.<br />

With times, the interfacial gravel layer burst<br />

first, rapidly followed by a central red mudboil.<br />

In mature forms, mosses can invade the gravely<br />

circle but not the boil.<br />

Micromorphological investigati<strong>on</strong>s show that the<br />

cryogenic fabric remains stable throughout the red<br />

clay profile, even in the surficial horiz<strong>on</strong>. This<br />

shows that load casting or c<strong>on</strong>vecti<strong>on</strong>al theories<br />

are unacceptable in this case.<br />

As a c<strong>on</strong>clusi<strong>on</strong> this early Holocene site can<br />

easily produce coalescing st<strong>on</strong>e circles or mudboils<br />

in imperfectly drained.sites in about 9000<br />

freezing cycles.<br />

b) In the vicinity of Kvadehuk, in the same age and<br />

drainage c<strong>on</strong>diti<strong>on</strong>s, mature st<strong>on</strong>e circles can<br />

occur. Here, as in other sites <strong>on</strong> the Brogger , the<br />

fine matrix is formed by residual silt (frost<br />

shattering and differential dissoluti<strong>on</strong> of beach<br />

pebbles and rock outcrops in dolomitic limest<strong>on</strong>e)<br />

which has been illuviated in depth by melt water<br />

and freeze-thaw translocati<strong>on</strong> (van Vliet, 1983).<br />

This feature, dem<strong>on</strong>strated by Forman and Miller<br />

(1984) in this area, produces at depth an highly<br />

frost susceptible matrix and in the surface, a dry<br />

unc<strong>on</strong>solidated gravelly layer. In this c<strong>on</strong>trasted<br />

situati<strong>on</strong> (experiment at the Caen Stati<strong>on</strong>), the<br />

differential frost heave of the silt can easily<br />

protrude through the surface gravel, enlarge and<br />

finally become coalescing. The micromorphology<br />

shows the partial c<strong>on</strong>servati<strong>on</strong> in depth of the<br />

traces of ice lenses (more or less preserved<br />

following the clay c<strong>on</strong>tent in the matrix) inside<br />

the mudboil ; a vesicular horiz<strong>on</strong> occurs at the<br />

c<strong>on</strong>tact of the st<strong>on</strong>e circle, even in depth, and in<br />

the surface 20 crn of the boil ; it results from the<br />

local rapid thawing of the material with the<br />

c<strong>on</strong>sequent collapse of the cryogenic fabric (Van<br />

Vliet et a!., 1984). As before, it is believed that<br />

st<strong>on</strong>e circles the evoluti<strong>on</strong> sand mudboil is<br />

c<strong>on</strong>trolled by drainage variati<strong>on</strong>.<br />

The c<strong>on</strong>trast of frost susceptibility acts as an<br />

acceleratorcompared to the Stupphalet site.<br />

Moreover, in such c<strong>on</strong>trasted cases, a previously<br />

weakness seems unnecessary to produce a boil. The<br />

existing c<strong>on</strong>trast may be originally present,<br />

inherited from st<strong>on</strong>e frost-jacking (formati<strong>on</strong> of a<br />

st<strong>on</strong>e pavement in depressi<strong>on</strong>) or produced as in of<br />

most of the cases by debris translocati<strong>on</strong> in<br />

depth. Here load casting and c<strong>on</strong>vecti<strong>on</strong>al theories<br />

101 1

Fig. 8 - Differential heave and growth of the st<strong>on</strong>e circles of the StuphaLlet flat - 1. red glacio-marine silty clay ;<br />

2. laguna1 gravel and sands i 3. black cryptogamic crust ; 4. grey lichens ; 5. observed level of the water table (20,9.85)<br />

as proposed by Prestrud and Hallet<br />

inapplicable.<br />

(1986) are<br />

ti<strong>on</strong> and pattern acquisiti<strong>on</strong> in soils affected<br />

weaknesses such as thermal or desiccati<strong>on</strong> nets.<br />

- A marked c<strong>on</strong>trast of frost susceptibility seems<br />

c ) Granulometric analysis undertaken <strong>on</strong> circles<br />

and stripes show a translocati<strong>on</strong> of clay at depth<br />

to act as an accelerator, In this case, and if<br />

as alreadyobservedbySchmertmann & Taylor<br />

gradient is negative, the sometimes loose cha-<br />

(1965) ; this is not <strong>on</strong>ly the result of unsorted<br />

racter of surficial layer leads to formati<strong>on</strong> of<br />

accumulati<strong>on</strong> of frost shattering products but<br />

coalescing circles without a necessary net of<br />

results mainly form a preferential translocati<strong>on</strong><br />

craks.<br />

of clays in depth of the suspensi<strong>on</strong> created by the - This comm<strong>on</strong> sketch of evoluti<strong>on</strong> of cryoturbated<br />

destructi<strong>on</strong> of cryogenic fabric (van Vliet, 1985) soils fits very well with the previous obserin<br />

surface horiz<strong>on</strong>s. Atextural accumulati<strong>on</strong> forms vati<strong>on</strong>s of Hopkins & Sigafoos ( 1950) which were<br />

above an hydraulic c<strong>on</strong>ductivity boundary, in this am<strong>on</strong>gst the firsto show that patterned grounds<br />

case the permafrost. This feature occurs also in corresp<strong>on</strong>ded to cryoturbati<strong>on</strong>s in profiles.<br />

other sediments like in till (Locker 1986). Their<br />

c<strong>on</strong>sequences are<br />

- Our sketch presents also the advantage that it<br />

:<br />

1) an increase in stability of the cryogenic<br />

takes into account the textural evoluti<strong>on</strong> of a<br />

fabric in depth ox downslope positi<strong>on</strong> associated<br />

sediment affected by a cryogenic diagenesis and<br />

with an increase in frost susceptibility,<br />

the modificati<strong>on</strong>s of its frost susceptibility with<br />

2) and a lost of fabric stability and of frost<br />

aging of the topographical surface.<br />

susceptibility in the superficial and upslope<br />

horiz<strong>on</strong>s associated with a propensity to thixo-<br />

AKNOWLEDGMENT<br />

tropy and mud flow,<br />

This work was financially supported by the french<br />

These particle translocati<strong>on</strong>s lead progressively<br />

CNRS "GLS-Arctique" and Centre de G6omorphologie<br />

to a negative gradient of frost susceptibility.<br />

where the analytical datas, the experimental<br />

This explains the omnipresence of inactive circles<br />

researches and the dactylography were performed.<br />

<strong>on</strong> oldArcticsurfaces.Thefeaturebecomes<br />

We thank the following organisms for their logisinactive<br />

when the top of the fines accumulati<strong>on</strong><br />

tical help : the Norsk Polar Institute, the<br />

becomes so deep to escape the injecti<strong>on</strong> process.<br />

Kingsbay Kull Company, Elf Nofge, the french<br />

Ambassy and the Cohpagnie Paquet. We thank also<br />

d) On slopes, this sketch remains valuable, as in John Mitchell (Ottawa) for improving our transthe<br />

case of cryoturbati<strong>on</strong>s ; by the progressive lati<strong>on</strong>.<br />

creati<strong>on</strong> of negative gradient, mudboil can protrude<br />

through a scree surface as <strong>on</strong> profile nearby REFERENCES<br />

Blomstrand peninsula (Herz & Andreas, 1966). These<br />

features aye particulary comm<strong>on</strong> in z<strong>on</strong>es 'of<br />

BROSSARD, Th & JOLY, D, 1986. Le complexe g6omordrainage<br />

c<strong>on</strong>centrati<strong>on</strong>, leading sometimes to rows<br />

phologique aval des glaciers Loven Est et Centr<br />

of mudboils aligne al<strong>on</strong>g the main seepage lines.<br />

(Spitzbergl. Cahiers de Gdoqraphie de Besanq<strong>on</strong>,<br />

29, (2), 5-58<br />

CONCLUSIONS<br />

CEGLA, J.R. & DZULYNSKI, S., 1970. Systems with<br />

reversed density gradient and their occurence in<br />

The systematic use of micromorphological techperiglacial<br />

z<strong>on</strong>es. Acta Univ. Wratisl., Studia<br />

niques leads us to c<strong>on</strong>clude hat differential<br />

geograf., 13, 17-39<br />

frostheave is the main mechanism resp<strong>on</strong>sible for<br />

CORBEL, J., 1961. Morphologie periglaciaire de<br />

both cryoturbati<strong>on</strong> and patterned ground genesis.<br />

I'Arctique. Annales de Geoqraphie, 70, 1-24<br />

CORTE, A., 1972. Laboratory formati<strong>on</strong> of extrusi<strong>on</strong><br />

- The rigidity of wet surfaces by frost, already features by multicyclic freeze-thaw in soils.<br />

advocated by many authors (Washburn, 1969 ; Bull. Centre G6omorphologie CNRS, Caen, no 13, 14,<br />

Shilts, 1973, 1978) is very important, but it is 15, 157-182<br />

here related with poorly to imperfectly drained COUTARD, J.P* & MUCHER, H.M. , 1485. Deformati<strong>on</strong> of<br />

soils, with differential heave and cryogenic<br />

laminated silt loam due to repeated freezing and<br />

pressure to explain the evoluti<strong>on</strong> of micro- thawing. Earth Surface Processes and Landforms,<br />

topography. The positi<strong>on</strong> of the water table in IO, (4l, 309-319<br />

autumn is of prime importance. I<br />

DYLIKOWA, A., 1961. Structures de pressi<strong>on</strong>s<br />

- The role of permafrost is limited ; it essentialc<strong>on</strong>g4listatiques<br />

et structures de g<strong>on</strong>flement par<br />

ly keeps especially in autumn water table in the<br />

le gel pres Katarzynow de pres de Lodz. Bull. SOC.<br />

soil surface vicinity in porous sediments (cryo-<br />

Lettres Lodz, 12, (91, 1-23<br />

genic fabric).<br />

FORMAN, S. & MILLER, G., 1984. Time dependent soil<br />

morphologies and pedogenic processes <strong>on</strong> raised<br />

- The complementary informati<strong>on</strong> given by the type beaches, Broggerhalvoya, Spitzbergen Svalbard<br />

of frost susceptibility gradient leads to an easy archipelago. Arctic and Alpine <strong>Research</strong>, 16, (4),<br />

understanding (fig. 9) of the dynamics of ihjec- 381-394<br />

1012

A<br />

GRADIENT OF FROS,T<br />

POSITIVE , - N<br />

-<br />

SUSCEPTIBILTY<br />

EGATIVE<br />

POWBEB OF FREE%&<br />

. ,... .....*........... ...,... TEAW CYCLES<br />

.f"m&<br />

r;.:::,., ~ ..., 1 : o ;<br />

hummocks<br />

improved drainage<br />

FISSURR OPEBING<br />

- "<br />

A :45<br />

B : 10-100<br />

C :)500<br />

D :slOOO<br />

limited frost<br />

penetrati<strong>on</strong><br />

LEGBPD :<br />

, :.. "<br />

coarse,rnedium,finc<br />

1<br />

DBAflPAGE<br />

1 :capillary fringe<br />

surficial pFC2<br />

water tables<br />

2 rlocati<strong>on</strong>in auw<br />

3 :locati<strong>on</strong> in summe<br />

Fig. 9 - General sketch of cryoturbati<strong>on</strong>s and patterned ground development<br />

HALLET, B. & PRESTRUD, S., 1986. Dynamics of au S. du K<strong>on</strong>gsf jord, Svalbard. Rapport de la<br />

periglacial sorted circles in Western Spitzberqen. Missi<strong>on</strong> Spitzberg 82, public. interne Centre<br />

Quaternary Res., 26, ( 1 ) , 81 -99<br />

G&omorpholoqie CNRS, Caen, 39 p.<br />

HERZ, K. & ANDREAS, G., 1966. Untersuchungen zur VAN VLIET-LANOE, B. , 1985a. Frost effects in soils<br />

Morphologie der periglazialen Auftauschicht in in "Soil and Quaternary Landscape Evoluti<strong>on</strong>" * J.<br />

K<strong>on</strong>gsfjordgebiet (West-Spitsbergen). Petersmann Boardman edit., 117-158<br />

Mitt, 110, (3), 190-198<br />

VAN VLIET-LANOE, B., 1986. Interacti<strong>on</strong> entre<br />

HOPKINS, D.M. & SIGAFOOS, R.S., 1951. Frost acti<strong>on</strong> activite biologique et glace de s6grigati<strong>on</strong> en<br />

and vegetati<strong>on</strong> patterns <strong>on</strong> Seward Peninsula, lentilles ; exemples observ8s- en milieu arctique<br />

Alaska, US Geol. Survey Bull., 974-c, 51-100 et alpin, In "Micrornorphologie des sols/soil<br />

LOCKE, W,, 1986. Fine particles translocati<strong>on</strong> in micromorphology". N. Fidoroff, L.M. Bress<strong>on</strong> et<br />

soils developped <strong>on</strong> glacial deposits, Southern<br />

M.A. Courty idit., AFES, 337-344<br />

Baffin Island, NWT, Canada. Arctic and Alpine VAN VLIET-LANOE, B., 1987a, Le r61e de la glace de<br />

Res., 18, (I),' 33-43<br />

dgrigati<strong>on</strong> dans les formati<strong>on</strong>s superficielles de<br />

MACKAY, J.R., 1983. .Downward water movement into 1'Europe de l'ouest, Processus et Hiritages. Thbse<br />

frozen ground, Western arctic coast, Canada. Can. d'Etat, Univ. Paris I, 796 p.<br />

Jour. Earth Sc,, 20, 120-134<br />

VAN VLfET-LANOE, B., 198713. Cryoreptati<strong>on</strong>, g6li-<br />

PISSART, A,, 1976. Sols h buttes, cercles n<strong>on</strong> fluxi<strong>on</strong> et coulees boueuses : unedynamique<br />

triks et sols stries n<strong>on</strong> tries de 1'Ile de Banks c<strong>on</strong>tinue en relati<strong>on</strong> avec le drainage et<br />

La<br />

(Canada, NWT). Biul. Peryglac., 26, 275-285<br />

stabilit4 de l'aqr6gati<strong>on</strong> cryog8nique. In "Loess<br />

PISSART, A., 1982. Dkformati<strong>on</strong> de cylindres de and Periglacial Phenomena". M. Pecsi ana H.M.<br />

lim<strong>on</strong> entoures de qraviers sous l'acti<strong>on</strong> d'alter- French edit., Akad. Kiado, Budapest, 203-226<br />

nances gel-degel. Experiences sur l'origine des VAN VLIET-LANOE, B., COUTARD, J.P. & PISSART, A+,<br />

cryoturbati<strong>on</strong>s. Biul. Peryglac., 29, 219-229<br />

1984. Structures caused by repeated freezing and<br />

REIN, R. & BURROUS, C. , 1980. Laboratory measu- thawing in various loamy sediments. A comparis<strong>on</strong><br />

rements of subsurface displacement during thaw of active, fossil and experimental data. Earth<br />

low angle slopes of a frost susceptible soil, Surface Proc., 9, 553-565<br />

Arctic and Alpine Res., 12, 349-358<br />

VAN VLIET-LANOE, B. & HEQUETTE, A., 1987. Activitd<br />

SCHMERTMANN, J.H. & TAYLOR, R.S., 1965, Quanti- Bolienne et sables lim<strong>on</strong>eux sur les versants<br />

tative data from patterned ground site over<br />

exposes au NE de la phinsule du Br6gqer Spitzberg<br />

permafrost. CRREL, <strong>Research</strong> Report, (96). 76 p. du NO (Svalbard). In "Loess and Periqlacial<br />

SHARP, R.P., 1942, Periglacial involuti<strong>on</strong> In Phenomena". M. Pecsi and H.M. French edit., Akad.<br />

Illinois. Jour. of Geology, 50, 113-133<br />

Kiado, Budapest, 103-124<br />

SHILTS, W.W. , 1978. Nature and genesis of mudboils WALKER, O., 1985. Vegetati<strong>on</strong> and envir<strong>on</strong>mental<br />

Central Keewatin, Canad. Jour. Earth Sc. , 10 , gradients of the Prudhoe Bay regi<strong>on</strong>, Alaska. CRREL<br />

1053-1068<br />

Report 85-1 4<br />

SIGAFOOS, R.S. E, HOPKINS, D.M., 1952. Soil stabi- WASHBURN, A., 1969. Weathering, frost acti<strong>on</strong> and<br />

lity <strong>on</strong> slopes in regi<strong>on</strong>s of perennially frozen patterned ground in the Mester Vig district, North<br />

ground. Highway <strong>Research</strong> Board, Special Report, East Greenland. Meddel. om Er<strong>on</strong>land, 176, (4),<br />

(21, 176-192<br />

303 p.<br />

TSYTOVICH, N.A., 1975. The mechanics of frozen WILLIAMS, P.J., 1959. The development and signiground.<br />

G.K. Swinzow editor, Scripta Books Cot ficance of st<strong>on</strong>e earth circles, Skrift. Norke<br />

Washingt<strong>on</strong> D.C., 152 p.<br />

Videnskaps Akademi 1, Oslo 1, Math. Naturviden.<br />

VANDENBERGHE, J. & VAN DEN BROECK, P., 1982. Kl., (31, 3-13<br />

Weichselian c<strong>on</strong>voluti<strong>on</strong> phenomena and processes ZOLTAI, S . PTARNOCAI, C., 1981,. Some n<strong>on</strong> sorted<br />

in fine sediments, Bareas, 1 1, 299-3 15<br />

patterned ground types in Northern Canada. Arcti<br />

VANVLIET-LANOE, B., 1983. Etudes cryop6dologigues and Alpine Res,, 13,. 139-1 51<br />

1013

THE STATISTICAL ANALYSIS ON FROST HEAVE OF SOILS<br />

IN SEASONALLY FROZEN GROUND AREA<br />

Wang, Jianguo and Xie, Yinqi<br />

Heil<strong>on</strong>gjiang Provincial <strong>Research</strong> Institute of Water C<strong>on</strong>servancy<br />

SYNOPSIS Based <strong>on</strong> a large number of experiment results in the seas<strong>on</strong>al frost areas (from<br />

N 36' to N 50.2'), the authors made a statistical analysis about the ultimate frost heave amount and<br />

presented a series of relati<strong>on</strong>s between the frost heave amount and its main influencing factors. The<br />

analytical reaultB show that the ultimate frost heave amount does not increase m<strong>on</strong>ot<strong>on</strong>ically with<br />

frost index and north latitude, but follows a random normal distributi<strong>on</strong>. The relat,i<strong>on</strong> between the<br />

underground water head before freezing and ultimate heave amount for clayey and sandy soil can be<br />

expressed by logarithmic and a linear functi<strong>on</strong>. respectively.<br />

INTRODUCTION<br />

The problem of frost heave in seas<strong>on</strong>al frost<br />

areas is <strong>on</strong>e of the anticipative tasks in the<br />

field of frozen ground research. In recent<br />

years, research <strong>on</strong> this subject has deepened<br />

and the research method has been changed from<br />

unitary geographical method to the synthetical<br />

study stage, in which frozen ground! is<br />

regardea as a system related to its structure,<br />

envir<strong>on</strong>ment and functi<strong>on</strong>.<br />

During frost heaving the structure of a soil<br />

(soil texture, density and water c<strong>on</strong>tent) and<br />

the envir<strong>on</strong>ment of the system (water supply and<br />

varioum engineering c<strong>on</strong>diti<strong>on</strong>s) are subject of<br />

random fluctuati<strong>on</strong>. Thus, it is difficult to<br />

get the practical indexes (parameters) for engineering<br />

with <strong>on</strong>ly the method of experimental<br />

soil mechanics. In view of this, the authors<br />

have made a statistical analysis <strong>on</strong> a large<br />

number of frost heave data observed from prototype<br />

engineering structure and observati<strong>on</strong><br />

sites In seas<strong>on</strong>al frost areas of China with the<br />

purpose of :&lJ finding the quantitative relati<strong>on</strong>s<br />

between the characteristic values of frost<br />

heave of subsoil of beneath hydraulic structures<br />

and the main factors which influence them,(2) establishing<br />

the critefia for engineering classificati<strong>on</strong><br />

of soils according to their frost heave<br />

behaviour, and (3) deriving the analytical equati<strong>on</strong>s<br />

to necessary for determining frost heave<br />

indexes to satisfy the requirements of frost<br />

heave forecasting and engineering design.<br />

data are obtained from the areas between 36 to<br />

50.2 degrees north latitude of China. Frost<br />

informati<strong>on</strong> c<strong>on</strong>cerning alpine c<strong>on</strong>diti<strong>on</strong>s is not<br />

included.<br />

The principle of collecting data<br />

All the data used in this work have given sources<br />

and bel<strong>on</strong>g to the same type (e.g., same soil<br />

texture, water c<strong>on</strong>diti<strong>on</strong> and load). This ensures<br />

that the samples be random.<br />

Main items of statistics<br />

(1) The l<strong>on</strong>gitude and latitude of observati<strong>on</strong><br />

sites; (2) Soil text_ure including soil grain<br />

size. liquid limit (WL), plastic limit (W,),<br />

plasticity index (I ) and specific gravity (Gs):<br />

P<br />

(3) Soil classificati<strong>on</strong>; (4) Observati<strong>on</strong> time;<br />

(5) Freezing index (<strong>on</strong>e-year freezing index (F)<br />

or average freezing index (F) over several.<br />

years);(d) The c<strong>on</strong>diti<strong>on</strong>s of soil water (average<br />

w.ater c<strong>on</strong>tent, W, in before freezing and W' in<br />

the period of reaching the maximum frost depth);<br />

(7) The c<strong>on</strong>diti<strong>on</strong>s of underground water (including<br />

the ground water table 2 (metres) in prefreezing<br />

period and deepest water table 2'<br />

(metres) in freezing period);(8) Freezing thickness,<br />

H (metres): (9) Freezing depth (initial<br />

frozen thickness), HM (metres); (10) Ground<br />

frost heave amount h (metres); (11) Freezing<br />

time T (days) from the date of steady freezing<br />

in the ground to the date when the maximum fros<br />

depth is reached.<br />

THE LIMITS AND MAIN PARAMETERS OF THE STATIS-<br />

TICAL ANALYSIS<br />

The sources, tyDes and limits of data<br />

The data are selected from the reports of all<br />

previous Nati<strong>on</strong>al <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>s <strong>on</strong> Hydraulic Engineering<br />

and Anti-heave Technics, Nati<strong>on</strong>al Cbnference<br />

<strong>on</strong> <strong>Permafrost</strong> and Informati<strong>on</strong> Exchanging<br />

Network <strong>on</strong> Anti-heave. Amount which 98% of the<br />

THE STATISTICAL ANALYSIS ON THE REGIONAL<br />

REGULARITIES OF FROST HEAVE<br />

The reni<strong>on</strong>al regularities of the maximum value<br />

of fcost heave<br />

The maximum value of frost heave for both clayey '<br />

and sandy soil obtained from Xinjiang, Qinghsi,<br />

Gansu, Shanxi, Beijing, Neimeng, Heil<strong>on</strong>gjiang,<br />

Jilin and Lia<strong>on</strong>ing were shown in Fig.1 and Fig.2,<br />

1014

-0.4SEXP[-0.63617(X~-lO.O)*] (1)<br />

ul-<br />

"<br />

L<br />

North latitude D. dcerec<br />

Fig.1 The Maximum Values of Frost Heave<br />

vs North Latitude for Clayey Soil<br />

where hD,max is the potential maximum frost<br />

heave in metres, OD and u~ are Characteristic<br />

c<strong>on</strong>stants and have the value of OD-0.88654 and<br />

!J~-10.0 respectively, XD is the c<strong>on</strong>versi<strong>on</strong> value<br />

of the abscissa (equal to 0.2222D) and D denotes<br />

the-north latitude. *<br />

The statistical result for sandy soil is plotted<br />

in Fig.2, and shows a similar shape of envelope<br />

of the maximum values of frost heave vs north<br />

latitude to that seen in Fig.1 for clayey soil.<br />

Since the chasacteri8tic number us for sandy<br />

soil is greater than that €or clayey soil, the '<br />

decrease of the maximum values is slower. The<br />

relati<strong>on</strong> between the maximum values of frost<br />

heave and north latitude for aandy soil can be<br />

written as:<br />

where hc is the potential maximum frost<br />

D,max<br />

heave for sandy soil in meter, ug and pg are the<br />

characteristic c<strong>on</strong>stants, having the values of<br />

0;-0.1773, and US-21.3 and X; denotes the c<strong>on</strong>ver-<br />

si<strong>on</strong> value of abacissa and Xi-0.5.<br />

The peak of the envelope of maximum frost heave<br />

for sandy soil appears at about 42.5'N.<br />

I I I I<br />

35 40 45 50<br />

0, dtgrtc<br />

Fig.2 The Maximum Values of Frost Heave<br />

vs North Latitude for Sandy Soil<br />

The relati<strong>on</strong> between the maximum values of frost<br />

heave and freezing index<br />

The maximum values of frost heave for clayey<br />

soil as a functi<strong>on</strong> of Ereezing index (F) was<br />

plottedinFig.3. The relati<strong>on</strong> between hp,max<br />

and F can be written as<br />

respectively.<br />

These locati<strong>on</strong>s are all in the range of 36 to<br />

50.2 degrees north latitude, covering almost<br />

the entire seas<strong>on</strong>al frost area of China,<br />

It is seen from Fig.1 that the envelope of the<br />

maximum values of frost heave (h) versus north<br />

latitude (D) is o f a good random normal distributi<strong>on</strong><br />

with its peak at 45 N. This indicates<br />

that although frost heave i s the result of comprehensive<br />

effect of various factors, frost<br />

heave, c<strong>on</strong>sidered as a ground system behaviour,<br />

has the specific property of c<strong>on</strong>tinuous evoluti<strong>on</strong><br />

in time and space. The relati<strong>on</strong> between<br />

the maximum values of frost heave and north<br />

latitude D for clayey soil can be expressed as<br />

where hp,max is the possible maximum values of<br />

frost heave corresp<strong>on</strong>ding to a certain freezing<br />

index; OF and IJF are characteristic c<strong>on</strong>stants,<br />

having a value of w- 0.88654, and u~'2.40;<br />

X~=F/650 is the c<strong>on</strong>versi<strong>on</strong> value of abscissa,<br />

and F is freezina index which could be a <strong>on</strong>eyear<br />

observati<strong>on</strong> value or the average value over<br />

several years.<br />

With the same analysis. the statistical results<br />

for sandy soil are depicted in Fig.4. The standard<br />

deviati<strong>on</strong>, B for sandy soil is about two times<br />

greater than that for clayey soil. This indicates<br />

101 5

d n<br />

P, degree. day<br />

Fig.3 Maximum Values of Frost Heave as<br />

a Fupcti<strong>on</strong> of Freezing Index for Clayey<br />

Soil<br />

o.3t<br />

0.1<br />

I I<br />

I<br />

I<br />

I<br />

I<br />

.. . .<br />

I<br />

I<br />

0 1000 2000<br />

Fig.4 Maximum values of Frost Heave<br />

as a Functi<strong>on</strong> of Freezing Index for<br />

Sandy Soil<br />

It is seen from Figs 3 and 4 (or eqs 3 and 4)<br />

that the peak of the envelopes appears at a<br />

freezing index of 1560 degree-days for clayey<br />

soil and 1200 degreehdays for sandy soil. respectively,<br />

The two freezing indexes corresp<strong>on</strong>d<br />

to the latitude of 45'N for clayey soil and<br />

42.5'N for sandy soil, at which the peak of the<br />

envelopes of h vs D appears.<br />

In additi<strong>on</strong>, the authors have also made a statistical<br />

analysis <strong>on</strong> the maximum values Of<br />

frost heave vs frost depth (Hn), frozen ground<br />

thickness (H) and average freezing speed (Vf).<br />

It is found that the maximum values of frost<br />

heave closely follow a normal distributi<strong>on</strong> with<br />

all these random variables. This indicates that<br />

frost heave of the ground does not always increase<br />

with increasing freezing index, frozen<br />

ground thickness, frost depth and rate of freezing,<br />

but there exist optimum values for producing<br />

the maximum frost heave. For clayey soil,<br />

the optimum value of frozen thickness H-1.35 m,<br />

the optimum value of frost depth H"1.15 m, and<br />

the optimum value of average freezing speed<br />

if-l.lO~cm.day. The optimum values D and F can<br />

be obtained from the random normal distributi<strong>on</strong>.<br />

These values provide a scientific basis for<br />

engineering design for frost protecti<strong>on</strong> and<br />

frost heave forecasting.<br />

THE STATISTICAL ANALYSIS OF FROST HEAVE AND<br />

WATER CONGITION<br />

Relati<strong>on</strong> between frost heave and nround water<br />

table before freezing<br />

The frost heave behaviour of soils Is very'sensitlve<br />

to water c<strong>on</strong>diti<strong>on</strong>s. The ground water<br />

table before freezing is usually refered to the<br />

level observed in the first 10 days for which<br />

the ground surface Is c<strong>on</strong>tinually frozen (or<br />

average value in this period). The statistical<br />

curve of ground water depth Z before freezing<br />

va the maximum value of frost heave for clayey<br />

soil Is shown in Fig.5. The geographical locati<strong>on</strong>s<br />

from which the data originated the same<br />

as those used in Fig.1. From Fig.5, we may find<br />

that with lower ground water table,the maximum<br />

that the variati<strong>on</strong> of maximum values of frost<br />

heave with F for sandy soil Is less sensitive<br />

than that for clayey soil. The relati<strong>on</strong> between<br />

hi,max and F for sandy soil can be expressed as:<br />

~0.225EXP[-O.l5S(X~-4.53)'] (4)<br />

where h;, is the possible maximum values of<br />

frost heave for sandy soil; 0; and U; are<br />

characteristic c<strong>on</strong>stants and have a value of<br />

=1.773, and uE-4.53; and Xij-Pf265 is the c<strong>on</strong>-<br />

"CF<br />

versi<strong>on</strong> value of abscissa.<br />

L I 1 1 I 1<br />

0 1.0 2.0 3.0 4.0<br />

2.m<br />

Fig.5 Ground Water Table'before Freezing<br />

vs Maximum Frost Heave for Clayey Soil<br />

1016

value of frost heave decreases, which can be<br />

expressed as<br />

h ,<br />

= 0.45 EXP(-0.7Z)<br />

where hz,max is the possible maximum frost<br />

heave corresp<strong>on</strong>ding to a certain ground water<br />

table beforefreezing for clayey soil, and Z is<br />

the depth of ground water table before freezing<br />

in metres.<br />

The same kind of statistical curve €or sandy<br />

soil is shown in Fig.6 for snady soil (hc 1.<br />

z max<br />

The relati<strong>on</strong> between the maximum values oi<br />

frost heave and the depth of ground water table<br />

before freezing (Z) is linear and can be described<br />

by<br />

hC,, max<br />

0.225-0.1072<br />

The frost heave of soils is closely related to<br />

spatial factors, as well as the functi<strong>on</strong> of the<br />

factors of soil texture, values of hD or<br />

, max<br />

corresp<strong>on</strong>ding to D or F can be regarded<br />

hF, max<br />

as the quantitative basis of specifying geographical<br />

locati<strong>on</strong>s. For the same D or F,<br />

although the frost heave changes at random, it<br />

is still under the c<strong>on</strong>trol of the major factor<br />

Z.<br />

The statistical analvsis <strong>on</strong> frost heave and<br />

ground water c<strong>on</strong>diti<strong>on</strong><br />

The water c<strong>on</strong>tent before freezing is usually<br />

defined as the average water c<strong>on</strong>tent of frozen<br />

soil in the first 10 days of steady freezing<br />

period. The statistical analysis indicates<br />

that frost heave increases linearly with increasing<br />

prefreezing water c<strong>on</strong>tent (W) and can<br />

be expressed as<br />

hw,max = 1.333W-0.2<br />

CONCLUSION<br />

(i) Summing the envir<strong>on</strong>mental factors influencing<br />

frost heave, the north latitued<br />

D and freezing index F all c<strong>on</strong>form<br />

to the random normal distributi<strong>on</strong> va the<br />

maximum values of frost heave. Thus,<br />

in seas<strong>on</strong>al frost areas, the amount of<br />

frost heave may be used as a quantitative<br />

basis for sub-dividing geographical<br />

regi<strong>on</strong>s. When Dm45 degrees and F-1560<br />

'C-day, frost heave in clayey soil will<br />

have the maximum value. When D142.5<br />

degrees and F-1200 'C-day, frost heave<br />

in sandy soil will have the maximum<br />

value. When D or F are larger than<br />

those values frost heave will, c<strong>on</strong>tradictorily,<br />

decrease. This is obviously<br />

due to the fact that the freezing rate ,<br />

is greater than the speed of water migrati<strong>on</strong>.<br />

For clayey soil. the optimum<br />

value of freezing rate for producing the<br />

maximum frost heave is about 1.10 cm/day.<br />

(ii) Statistical analysis shows that the<br />

potential maximumfrost heave amount can<br />

be well related to north latitude,<br />

freezing index,prefreezing fround water<br />

table and water c<strong>on</strong>tent in terms of various<br />

mathematical expressi<strong>on</strong>s.<br />

ACKNOWLEDGl!MEBT<br />

The authors sincerely thank the pere<strong>on</strong>s who<br />

provided us various and very useful informati<strong>on</strong><br />

and experimental data.<br />

where h,<br />

fracti<strong>on</strong>s.<br />

is in metres and W is in decimal<br />

I<br />

I<br />

0 1.0 2.0 3.0<br />

Z. m<br />

Fig.6 Ground Water Table before<br />

Freezing vs Maximum Frost Heave<br />

for Sandy Soil<br />

1017

DISCONTINUOUS PERMAFROST MAPPING USING THE EM-31<br />

D.S. Washburn and A. Phukan<br />

Cold Regi<strong>on</strong>s Laboratory, Inc. (CRL), Anchorage, The University of Alaska at Anchorage (UAA)<br />

SYNOPSIS This paper outlines the successful use and advantaFe of a employing combined<br />

geophysical inducti<strong>on</strong> resistivity survey and drilling program for the delineati<strong>on</strong> of warm, shallow,<br />

disc<strong>on</strong>tinuous permafrost. A few lines of data are given in buildin5 by building detail from a<br />

major housing project in Ft. Wainwright, Fairbanks, Alaska. The apparent resistivity signatures of<br />

frozen, transiti<strong>on</strong>ally frozen, and unfrozen soils are shown. Survey costs are given end success<br />

rates are discussed.<br />

IMTRORUCTION<br />

A Fort Wainwright, Fairbanks, Alaska, housing<br />

project is located in the shallow disc<strong>on</strong>tinuous<br />

permafrost z<strong>on</strong>e. It lies <strong>on</strong> an 80 acre (32.4<br />

hectare) site in the Chena River silty, sandy,<br />

qravelly alluvium. The 400 unit project has<br />

ipproximately 150 individual buildings that are<br />

primarily two story, wooden framed, multiplex<br />

townhouses. The design-stage geotechnical site<br />

investigati<strong>on</strong> roughly outlined the areas of<br />

frozen and unfrozen ground. An inductive<br />

resistivity geophysical survey was planned as<br />

the most cost-effective means to detect the<br />

presence or absence of permafrost <strong>on</strong> a proposed<br />

building by building basis. Such informati<strong>on</strong><br />

would help to design more cost-effective<br />

foundati<strong>on</strong> systems for the buildings, would<br />

help to direct and minimize any additi<strong>on</strong>al<br />

detailed drilling that would be required prior<br />

to c<strong>on</strong>structi<strong>on</strong>, and for ec<strong>on</strong>omic and supply<br />

planning purposes, wohld help to estimate the<br />

required number of the more expensive<br />

foundati<strong>on</strong> designs for permafrost.<br />

The traditi<strong>on</strong>al approach in engineering for<br />

locating permafrost under c<strong>on</strong>structi<strong>on</strong> projects<br />

is to c<strong>on</strong>duct extensive drilling programs. In<br />

many cases however, geophysical surveys should<br />

be c<strong>on</strong>ducted in order to augment the borehole<br />

informati<strong>on</strong>. The major advantage of a combined<br />

geophysical and drilling program is that often<br />

more ground can be c<strong>on</strong>tinuously explored at<br />

less cost than with a drilling program al<strong>on</strong>e.<br />

For example, Peffer and Robelen (1983) show as<br />

much as a 12 to 1 cost advantage with various<br />

geophysical methods for studies that are<br />

comparable in scope and technique to the effort<br />

required for the search of shallow frozen<br />

ground in major engineering projects.<br />

Additi<strong>on</strong>al c<strong>on</strong>siderati<strong>on</strong>s for the choice of the<br />

inductive resistivity method in general and the<br />

Ge<strong>on</strong>ics EM-31 in particular for this problem<br />

include the following.<br />

Of the comm<strong>on</strong> surface geophysical tools,<br />

resistivity can be expected to have the<br />

greatest physical property c<strong>on</strong>trast<br />

between frozen and unfrozen soils (see<br />

Charmichael, 1952; Clark, 1955; or<br />

Kawasaki, 1935). Maximizing the target's<br />

c<strong>on</strong>trast with its host increases its<br />

detectibility and thus increases the<br />

chance of success for the survey. For<br />

example, at warm permafrost temperatyres,<br />

Hoekstra and McNeill (1975) show c<strong>on</strong>trasts<br />

of about 3 for saturated sandy gravel and<br />

of ebout 1.5 for Fairbanks silt. That is<br />

to say, a warm Fairbanks silt permafrost<br />

is generally a very detectable 1.5 times<br />

more resistive than the same, but. thawed<br />

silt.<br />

Seismic c<strong>on</strong>trasts may or may not be<br />

sufficient in this project's mostly icepoor<br />

alluvium. Moreover, seismic surveys<br />

are generally much slower and more complex<br />

to run; require larger crews; have more<br />

complex, less durable, less- reliable, snd<br />

more expensive instrumentati<strong>on</strong>: and, are<br />

not as qualitatively easy to interpret in<br />

the field while underway. With adequate<br />

c<strong>on</strong>trasts, seismic methods can however<br />

give a much better target definiti<strong>on</strong> at<br />

depth. But in this shallow case, this is<br />

not a governing c<strong>on</strong>cern.<br />

Inductive resistivity methods have at<br />

least three times more lateral resoluti<strong>on</strong><br />

than the galvanic, or direct current,<br />

resistivity techniques. Thus, more<br />

detailed data from the n<strong>on</strong>traditi<strong>on</strong>al<br />

inductive resistivity method is possible e<br />

The inductive method uses n<strong>on</strong>-c<strong>on</strong>tacting<br />

fields coils so that significant time and<br />

effort is saved from making four good<br />

electrical electrode c<strong>on</strong>tacts with the<br />

ground for each measurement as is required<br />

by the g,alvanic systems.<br />

1018

To their disadvantage in very resistive<br />

msterials, yalvanic systems are<br />

susceptible to detrimentslly high<br />

electrode c<strong>on</strong>tact resistances, where3s the<br />

inductive methods suffer from a reduced<br />

sensitivity (see Arc<strong>on</strong>e, 1991). Neither<br />

turns out to be a problem for the data<br />

found below.<br />

On this project, all the permafrost that<br />

has been drilled was hit at least before a<br />

depth of 15 feet (4.6 m). So, for the<br />

simple two-layer case of 15 feet (4.5 TI)<br />

of thawed material over permafrost, the<br />

EM-31 receives approximately 356 of its<br />

signal from the more resistive permafrost<br />

(see Ge<strong>on</strong>ics, 1979). Thus, the EM-71 has<br />

an adequate depth of explorati<strong>on</strong>.<br />

- The EM-11 weiThs about 20 pounds, requires<br />

<strong>on</strong>ly 3 <strong>on</strong>e-man crew, and is very easy to<br />

operate.<br />

- And, in Anchorage, the EM-31 rents from a<br />

local sourcs for 80 $US per day or 750 %US<br />

per week, or costs about 10 000 BUS. So it<br />

is quite affordable.<br />

have effectively mapped the arsal extent of<br />

this frost susceptible, F7 to F7, soil thereby<br />

saving some of the delineati<strong>on</strong> drilling costs.<br />

Furthermore, excavati<strong>on</strong> estimates for its<br />

removal from underneath the proposed building<br />

sites could have been<br />

is no c<strong>on</strong>fusi<strong>on</strong><br />

made from the data. There<br />

about this relatively<br />

resistive material's resp<strong>on</strong>se being that of<br />

permafrost because of its surface expressi<strong>on</strong><br />

and correlati<strong>on</strong> with the existing drillhole<br />

data. However, as a result of the reduced<br />

permafrost to overburden c<strong>on</strong>trast and hence it5<br />

reduced detectability, a few drillholes would<br />

still have been necessary to check if any<br />

frozen ground lay hidden underneath the dry<br />

sands<br />

Over the suspected unfrozen ground, we are able<br />

to positively establish that no permafrost<br />

exists under any of the proposed foundati<strong>on</strong>s to<br />

within a depth of at least 35 feet (10.7 m).'<br />

Because cutting line is the most time c<strong>on</strong>suming<br />

part of the survey and since little was<br />

required here, it took two men <strong>on</strong>ly a day and a<br />

half to stake and survey the necessary 14 lines<br />

in this unfrozen area. This figures to about<br />

50 $US per acre (124 $US per hectare) for<br />

acquisiti<strong>on</strong> costs, or about the cost of two of<br />

the twenty existing auger holes in the area.<br />

SURVEY DATA AND RESULTS Line 20<br />

"<br />

The EM-31 was used to detect shallow permafrost<br />

al<strong>on</strong>g proposed roads, underground utility<br />

right-of-ways, snd building lines. The goal<br />

was to establish the presence or absence of<br />

frozen ground under esch proposed site so that<br />

the proper designs could be plsnned. This was<br />

to be accomplished by measuring: the apparent<br />

resistivity at esch site al<strong>on</strong>g lines at 30 foot<br />

(5.1 m) stati<strong>on</strong> intervals and by using any<br />

nearby drillholes from the desi$n-stage<br />

geotechnical investigati<strong>on</strong> as ground truth to<br />

help c<strong>on</strong>trol the interpretati<strong>on</strong>. Then, 2<br />

minimal drilling and trenching program would be<br />

planned to check any areas in questi<strong>on</strong> and any<br />

interpreted hidden frozen z<strong>on</strong>es that lay<br />

beneath the proposed structures for further<br />

thaw strain and thermal c<strong>on</strong>siderati<strong>on</strong>s.<br />

Line 5<br />

-<br />

A t first, a 15 acre (5.5 hectare) area, about<br />

<strong>on</strong>e fifth of the project, was surveyed. No<br />

permafrost was drilled in this area prior to<br />

the survey, and c<strong>on</strong>sequently n<strong>on</strong>e was expected.<br />

Appropristely, n<strong>on</strong>e is detected by the<br />

resistivity survey, The left half of fiyure 1<br />

shows a typical apparent resistivity line,<br />

line 9, over unfrozen predominstely silty sands<br />

and gravels. Note the 170 ohm-m values for the<br />

unfrozen material in this area. Except for -3<br />

few cultursl spikes at ststi<strong>on</strong>s TtOO and 1+70<br />

(in feet), note also how relstively smooth and<br />

noise-free the data is.<br />

As seen at the start of line 8, the most<br />

resistive material encountered in the area is a<br />

very distinct, dry deposit of loose, very fine-<br />

4rsined aeolian sands. It has an spparent<br />

resistivity of 753 ohm-m. Had the survey been<br />

planned and c<strong>on</strong>ducted esrlier in the pro-desien<br />

site Investirgati<strong>on</strong> prorgram, it would have<br />

turned out that the resistivity method would<br />

The right side of figure 1 shows line 20 with<br />

the locati<strong>on</strong>s of the proposed buildings. It<br />

a130 shows the results of the post-survey, prec<strong>on</strong>structi<strong>on</strong><br />

drilling at the bottom of the<br />

secti<strong>on</strong>. Line 20 is an offset extensi<strong>on</strong> of line<br />

9. Line R stati<strong>on</strong> O+OO is proximal to line 20<br />

stati<strong>on</strong> 5t70. The 350 ohm-m, dry aeolian sand ..<br />

hump can be seen centered at stati<strong>on</strong> 5+30.<br />

From stati<strong>on</strong> 4+50 to about +go, the data shows<br />

the characteristic transiti<strong>on</strong> to resistive<br />

permafrost, which in this case is frozen aandy<br />

gravels and gravelly sands. The anomalous data<br />

points st stati<strong>on</strong>s 4t40 and 2+RO are due to<br />

man-made clutter and can be ignored. At 0+50,<br />

the data -shows that a low resistivity thaw bulb<br />

exists and extends off the beginning of the<br />

line. The thaw bulb coincides with an existing<br />

road that is located off the end of the line at<br />

stati<strong>on</strong> 0-70.<br />

The ground c<strong>on</strong>diti<strong>on</strong>s under the proposed<br />

buildings al<strong>on</strong>g line 20 are interpreted to be:<br />

Building<br />

89 - unfrozen<br />

90 - unfrozen<br />

91 - transiti<strong>on</strong>al<br />

97 - frozen, and<br />

96 - frozen.<br />

Later drilling c<strong>on</strong>firms the above<br />

interpretati<strong>on</strong> except that borehole E-91 is<br />

completely unfrozen. Note the heavy frozen bar<br />

and the ice descripti<strong>on</strong> code <strong>on</strong> the borehole<br />

logs in the figure. It turns out that line 20<br />

traverses building 91 near the back of the 70<br />

foot ( P I m) deep building, which is also<br />

towards c<strong>on</strong>firmed frozen ground, and that RH B-<br />

91 was drilled near its fr<strong>on</strong>t, which is also<br />

towards thawed ground. Thus, thawed soils lie<br />

to the left 'and in fr<strong>on</strong>t of the secti<strong>on</strong> and<br />

buildiny, and frozen Soil5 lie to the right and<br />

behind the building. We therefore maintain<br />

1019

th .at the interoret ati<strong>on</strong> of tran siti<strong>on</strong>ally<br />

frozen soil is correct and that the much more<br />

expensive single borehole did not adequately<br />

investigate the site. Furthermore, if the<br />

foundati<strong>on</strong> was built for being <strong>on</strong> an unfrozen<br />

ground, we would then predict that the back<br />

left corner of the building will so<strong>on</strong> be<br />

differentially settling due to thaw<br />

c<strong>on</strong>solidati<strong>on</strong>.<br />

verifies that building 120 lies <strong>on</strong> unfrozen<br />

ground.<br />

The rayqed, irregular resp<strong>on</strong>se 3the ends of<br />

lines, 17 and 18, particularly from stati<strong>on</strong>s<br />

5+20 to 7t20 <strong>on</strong> line 13, supports a variety of<br />

interpretati<strong>on</strong>s. N<strong>on</strong>e of which have been<br />

particularly c<strong>on</strong>firmed or denied at this point.<br />

Since some rubbish is found overgrown <strong>on</strong> the<br />

ground in the woods at stati<strong>on</strong> 5t40 <strong>on</strong> line 15<br />

Lines 17 and I8<br />

(note the missing data point), the c<strong>on</strong>servative<br />

""<br />

interpretati<strong>on</strong> is that there is more metal junk<br />

Figure 2 shows two more lines from the same in the ground at the end of line I8 and that<br />

general area having permafrost a3 line 20. there is some kind of marginal c<strong>on</strong>ductor, like<br />

Lines 20, 18, and 17 are all sub-parallel to<br />

an old buried metal pipeline, that runs from<br />

each other and are separated by about 575 feet line 18 stati<strong>on</strong> 5t59 to line 17 stati<strong>on</strong> 5+50.<br />

(IO2 m) and 135 feet (41 m) respectively. The c<strong>on</strong>ductor bounds evidence of man's<br />

Buildings 121, 122, 124, and,ll7 and 118 are activities <strong>on</strong> the <strong>on</strong>e side from undisturbed<br />

all correctly interpreted to lie <strong>on</strong> frozen permafrost <strong>on</strong> the other. A more Speculative<br />

ground. Note the apparent resistivity highs and interpretati<strong>on</strong> says that there is <strong>on</strong>ly a little<br />

the logs <strong>on</strong> the figure. Numbers 125 and 119 are cutural noise at line 13 stati<strong>on</strong> 5t40 and that<br />

thought to lie <strong>on</strong> transiti<strong>on</strong>ally thawed<br />

there i s <strong>on</strong> line 19 a very irregular and<br />

material. But, EH B-125 shows <strong>on</strong>ly thawed, thermally unstable permafrost margin. A margin<br />

moist to saturated, medium sandy gravels and that includes a thaw channel at ststi<strong>on</strong>s 5+59<br />

fine gravelly medium sands. And, drilling <strong>on</strong> both lines 17 and 19. Al<strong>on</strong>g these lines of<br />

-600 ohm-m<br />

-500<br />

- 400<br />

-300<br />

-<br />

A0<br />

c<br />

-600 ohrn-m<br />

#<br />

-<br />

\<br />

500<br />

-P<br />

-400<br />

-200 P,200-<br />

LINE 20<br />

LINE 8<br />

LEGEND<br />

SP-SM Sand with Silt<br />

SP Sand, to Sand with Gravel, to<br />

GP-GM<br />

Gravelly Sand<br />

Gravel wilh Silt and Sand. lo<br />

Sandy Gravel with Silt<br />

GP Sandy Grovel<br />

Nbn N<strong>on</strong>-Vlsiblr, Well-B<strong>on</strong>ded, No Excess Ice<br />

Nbe N<strong>on</strong>-Visible, Well-B<strong>on</strong>ded, Excerr Ice Figure 1: EM-51 Apparent Resistivity Survey<br />

Vx Visible individual Ice Crystals Lines 8 and 30. Shown with Proposed<br />

Vc , Viribia icr Coatinga <strong>on</strong> Particles<br />

Building Locati<strong>on</strong>s and Post-Survey<br />

Drillhole Logs.<br />

1020

-800 ohm-m h 800-<br />

-700<br />

600-<br />

-5c<br />

4<br />

7+00 6tOO 500 I 4tO01 , 3+00 20,0, , ItOpl , 0<br />

- -<br />

I I I<br />

-800 ohm-m 800-<br />

700-<br />

600-<br />

5.00 pro0 I +op 2t00, 1*00 * -<br />

-<br />

SM<br />

- 7t00 6+00<br />

w<br />

GP-GM<br />

30 fl<br />

Figure<br />

3: EM - 71 Apparent<br />

Resistivity Survey<br />

Lines 17 and 18.<br />

Shown with Proposed<br />

Building Locati<strong>on</strong>s<br />

and Post - survey<br />

Drillhole Logs.<br />

1021

thought, there could also be some thermal<br />

degradati<strong>on</strong> of the permafrost under line 18 at<br />

stati<strong>on</strong> 2+30 which was later missed by either<br />

BH 8-122 or 8-124.<br />

Since the magnitude of the permafrost's<br />

apparent resistivity increases from about 550<br />

ohm-m <strong>on</strong> line 70, to about 700 <strong>on</strong> Line 18, to<br />

about 800 ohm-m <strong>on</strong> 17, the near-surface frozen<br />

ground is probably getting either thicker,<br />

colder, or icier. Colder and icier are thought<br />

to be the more important of the three since the<br />

bottom of the permafrost in this area cannot be<br />

seen with the EM-31. Note the similarly smooth<br />

transiti<strong>on</strong> down to the less resistive ground <strong>on</strong><br />

line 18 at stati<strong>on</strong>s 2400 to 1+20 and <strong>on</strong> line 17<br />

at stati<strong>on</strong>s 3480 to 2+80. The less resistive<br />

unit <strong>on</strong> line 18 at stati<strong>on</strong>a 1+20 to O+OO and <strong>on</strong><br />

line 17 at stati<strong>on</strong>s 2+80 to the O+OO is<br />

interpreted to be thawed, as stated above,<br />

because a similar resp<strong>on</strong>se was registered over<br />

a nearby shallow gravel pit. The apparent<br />

resistivity of this unit increases from about<br />

400 ohm-m <strong>on</strong> 18, to 500 <strong>on</strong> line 17. Thus, it<br />

appears that a gradual lithologic change is<br />

taking place. The 400 ohm-m thawed unit <strong>on</strong><br />

line 18 probably become8 less moist so as to<br />

increase its apparent resistivity to 500 ohm-m<br />

by line 17 while the permafrost becomes more<br />

resistive by line 17 possibly because of an<br />

increase of frozen moisture c<strong>on</strong>tent. A<br />

coarsening of the 400 ohm-m unit and an<br />

increase of the fines in the permafrost could<br />

explain the possible shift in the moisture, and<br />

c<strong>on</strong>sequently the resistivity. Boreholes BH B-<br />

125 and 8-120 c<strong>on</strong>firm the interpretati<strong>on</strong> by<br />

drilling coarser, drier, sandy gravels with<br />

some gravelly sands in B-120,. The 8-120 sands<br />

and gravels have an average moisture c<strong>on</strong>tent of<br />

7% for the material above the 15 foot (4.6 m)<br />

deep watertable. Compare that to an average<br />

1% moisture for the finer material in BH 8-125<br />

as described above. And, the borehole logs from<br />

the permafrost do indeed show siltier material<br />

(GP-GM, SP-SM, and SM) towards the +BOO ohm-m<br />

line 17 high, particularly in BH 8-117. The<br />

idea of having colder, more resistive<br />

permafrost in the directi<strong>on</strong> f,rom line 20 to<br />

line 17 follows from the fact that the edge of<br />

the permafrost in the directi<strong>on</strong> perpendicular<br />

to lines 17, 19, and 20 is mapped off the side<br />

of line 20 away from lines 17 and 98. Thus,<br />

<strong>on</strong>e would suspect colder ground inside of and<br />

away from the margins of the permafrost. An<br />

alternative interpretati<strong>on</strong> to the rise in<br />

apparent resistivity of the 400 ohm-m unit <strong>on</strong><br />

line 70 to 500 ohm-m <strong>on</strong> 17 is that a deep,<br />

resistive permafrost could exist under the unit<br />

at a shallower depth under line 17. This is<br />

not believed to be the case as a result of the<br />

vork in the nearby gravel pit, as menti<strong>on</strong>ed<br />

above. And as we have already seen, BH 8-120<br />

later cwfirms the interpretati<strong>on</strong>.<br />

Because of the more extensive line cutting that<br />

was needed, the acquisiti<strong>on</strong> costs in this<br />

neighborhood averaged about 1.5 timos that of<br />

those in the line 8 area example, or about 75<br />

$US per acre (195 $US per hectare). Of the 24<br />

buildings proposed for this <strong>on</strong>e area, we<br />

correctly interpreted that all 7 of our<br />

unfrozen cases are indeed unfrozen, 10 of our<br />

11 frozen cases were drilled solidly into<br />

permafrost, and of the 6 of our tranafti<strong>on</strong>al<br />

cases, 0 are unfrozen, 2 are marginally or<br />

transiti<strong>on</strong>ally frozen, and 2 are frozen at the<br />

drillhole locati<strong>on</strong>s. In light of the above<br />

discussi<strong>on</strong> about building 91 <strong>on</strong> line 20, we<br />

view our Interpretati<strong>on</strong> of the transiti<strong>on</strong>al<br />

cases as being successful. Significantly, the<br />

worst case of calling a site unfrozen when it<br />

turns out frozen, has not occurred. As for<br />

building 95, the <strong>on</strong>e frozen case in thls<br />

neighborhood that was found to be unfrozen by<br />

the drillhole, it is appropriate here to note<br />

that we have since learned from two temperature<br />

m<strong>on</strong>itoring holes that are placed near lines 17<br />

and 19 into presumably the coldest ground, that<br />

the upper 20 feet (5.1 m) of permafrost<br />

averages a warm 31.4OF (-0.3OC) during the<br />

summertime when the survey and drilling was<br />

d<strong>on</strong>e. Since buildinq 95 is very near the<br />

margin of the permafrost, but it is definitely<br />

completely within the greater than 500 ohm-m<br />

c<strong>on</strong>tour, and since the permafrost mar ins are<br />

probably warmer than 31.4'F (-0.3<br />

8 C), we<br />

suggest that the drilling acti<strong>on</strong> of the auger<br />

melted the marginal permafrost which was then<br />

logged as being unfrozen. Drilling may not<br />

indeed always produce the final word.<br />

Finally, in additi<strong>on</strong> to the main EM-71 mapping<br />

program, a few lines were surveyed with the<br />

deeper-looking EM-34. The EM-74 is very<br />

similar in principle to the EM-31, but it has<br />

two larger, more powerful, separable coils (the<br />

EM-31 is a sinyle piece of equipment that has a<br />

fixed 12 foot (5.7 m) coil spacing) which<br />

c<strong>on</strong>sequently makes it a little heavier, more<br />

complex, and requires a two man crew. The EM-<br />

34 was used to determine a depth to the bottom<br />

of the permafrost. Depths were needed to<br />

estimate what drilling capacity was required to<br />

later bore through the frozen ground and to<br />

estimate an upper limit of thaw c<strong>on</strong>solidati<strong>on</strong><br />

and settlement. It is estimated from the<br />

resistivity data that the permafrost i s<br />

everywhere something under 50 feet (19 m) thick<br />

wherever it was surveyed. One refrigerated<br />

corehole has been drilled to date, and there<br />

the permafrost is 43 feet (11.1 TI) thick.<br />

CONCLUSIONS<br />

Here, as in general, not all high resistivities<br />

exclusively indicate permafrost. On this<br />

project for example, 750 ohm-m aeolian sands<br />

and 500 ohm-rn coarse gravels have been<br />

described. Both of these excepti<strong>on</strong>s however<br />

are easily interpretable and require <strong>on</strong>ly a few<br />

drillholes to verify. Nevertheless, in all<br />

cases <strong>on</strong> this project, surveyed and drilled<br />

permafrost produced a recognizsble, generally<br />

greater than 500 ohm-m, apparent resistivity<br />

high. Eighty proposed building sites were<br />

investigated and not <strong>on</strong>ce was an area<br />

interpreted to be unfrozen when it turned out<br />

to be frozen - the worst case. Moreover, the<br />

method proved to be over 90% accurate for<br />

detecting permsfrost. A large part of the<br />

success is due in general to the moderately<br />

resistive, 300 ohm-m host which provides a good<br />

c<strong>on</strong>trast with the frozen ground. A survey in<br />

dry, clean gravels would not have been so<br />

revealing. But then again, it would not have<br />

been as critical to know. This success is<br />

1022

noteworthy in that the permafrost here is quite<br />

warm, above jloF (-O.S°C), and is thus not<br />

nearly so resistive and detectable as colder<br />

permafrost. This survey was very successful<br />

and provided a large amount of relatively<br />

ine.xpensive data that greatly complimented the<br />

borehole informati<strong>on</strong>. The inductive resistivity<br />

method <strong>on</strong> this project has proven to be<br />

accurate, reliable, faat, and very costeffective.<br />

C lark, S.P., Jr., ed. (1966).<br />

Physical C<strong>on</strong>stants, 587 pp, G<br />

New York.<br />

Ge<strong>on</strong>ics Limited (1979). Operating Manual for<br />

EM-31 N<strong>on</strong>-C<strong>on</strong>tacting Terrain C<strong>on</strong>ductivity<br />

Meter with Technical Notes, 57 pp, Ge<strong>on</strong>ica,<br />

Ontario, Canada.<br />

Hoekstra, P. & McNeill, J.D. (1973).<br />

Electromagnetic probing of permafrost.<br />

Proc. 3nd XCP, p 517-525, Yakutsk, USSR.<br />

REFERENCES<br />

Kawasaki, K. & Osterkamp, T.E. (1985).<br />

Electromagntic Inducti<strong>on</strong> Measurements in<br />

Arc<strong>on</strong>e, S.A. (1931). Some field studies of the<br />

<strong>Permafrost</strong> Terrain for Detecting Ground Ice<br />

correlati<strong>on</strong> between electromagnetic and<br />

and Ice-Rich Soils, 195 pp., University of<br />

direct current measurements of ground<br />

Alaska Geophysical Institute Report UAG<br />

resistivity. Underground Corrosi<strong>on</strong>, ASTM<br />

300, Fairbanks.<br />

Special Treatment Technical Testing<br />

Publicati<strong>on</strong> 741, p 92-110.<br />

Peffer, J.R. & Robelen, P.C. (1983).<br />

Affordable: Overburden mapping using new<br />

Charmichael, R.S., ed. (1992). Handbook of<br />

geophysical techniques. Pit & Quarry,<br />

August 1987.<br />

2, 749 PP<br />

1023

A DISCUSSION ON MAXIMUM SEASONAL FROST DEPTH OF GROUND<br />

Xu, Ruiqi, Pang, Guoliang and Wang, Bingcheng<br />

Hdl<strong>on</strong>gjiang Water C<strong>on</strong>servancy School, Harbin, China<br />

SYNOPSIS Maximum seas<strong>on</strong>al frost depth of ground affeotS the oaloulati<strong>on</strong> of frost heave,<br />

frost heave rate. oiroumferential fome and noma1 foroe, Whiuh is also the indispensable data<br />

for architeotunl desi@ and w<strong>on</strong>structi<strong>on</strong>. But habitually maximum frost depth of ground and the<br />

depth of freesing Soil layer are c<strong>on</strong>furred and without striot distincti<strong>on</strong>.<br />

The paper is for rereamhing and analyzing maximum seas<strong>on</strong>al frost depth of wornd. make alear the<br />

criteri<strong>on</strong> of oalaulating the maximum seas<strong>on</strong>al frost depth of p und.<br />

Maximum seas<strong>on</strong>al frost depth of ground directly<br />

affects the calculati<strong>on</strong> of froat heave oapacity,<br />

frost heave rate, normel form and uircumferential<br />

foroe, which is indispensablo data in<br />

the architectural design and c<strong>on</strong>atruoti<strong>on</strong>.<br />

However at present the maximum frost depth of<br />

grornd and the thiohess of freesing aoil layer<br />

are habitually mixed up both at home and abroad,<br />

and are not distinguished strictly. For instance,<br />

the neteorologiunl stati<strong>on</strong> and in and<br />

outdoor experiments measured that the froat<br />

depth was the thiokneas of freezing aoil lqyer,<br />

not the maximum fr0a.t depth of gromd.<br />

Whether with theoretical squati<strong>on</strong> or empirioal<br />

equati<strong>on</strong>. frost heave oapaoitj. water a<strong>on</strong>tent<br />

migrati<strong>on</strong> and frost heave rate are all related<br />

with froat depth. While adopting inoorreat<br />

froat depth, the frost heave rate that is<br />

uounted will be different. Thus the olrrssiiicati<strong>on</strong><br />

of frost heave divided by fTo,at heaverate<br />

is influenoed.<br />

Fmal depth. cm<br />

fig-1 the relati<strong>on</strong> between frost depth<br />

normal froat heave<br />

and<br />

Frost depth inoreaaes as the froat heave 16<br />

inureaaed. Vhen frost dopth la at its maximum<br />

the acuumulating valua of the frost heave is<br />

the greateat.<br />

The characteristic of fr<strong>on</strong>t heave in soil can<br />

be reflected by the law that the frost heave<br />

capacity and frost heave change al<strong>on</strong>g frost<br />

depth. See fig. 2.<br />

F~OSI hemvc cnpncW. mm<br />

The seas<strong>on</strong>al frost depth of ground is different,<br />

whioh has a great influence <strong>on</strong> the normal frost<br />

heave. See fig. I<br />

iiK.2<br />

P<br />

Maximum<br />

""""<br />

frost deplh<br />

frost heave VB froat depth<br />

1024

From the figure we bow that the distributi<strong>on</strong><br />

of frost heave capaoity al<strong>on</strong>g frost depth la<br />

mevm. Regarding this phwominw a8 the<br />

total frost heave capaoity of the soil surface<br />

(namely the accumulating frost heave capacity<br />

of the soil surface), the total frost heave<br />

qapaaity <strong>on</strong> the soil surfaoe inareasea with<br />

the developsment of frost depth, not increa8ing<br />

in dixeot proporti<strong>on</strong>, nor alwg the total<br />

froat depth. The froat henve <strong>on</strong>paoity m the<br />

soil surface arrives at its mnximun'<strong>on</strong>ly after<br />

frost developbg at a oertaia depth. Though<br />

frost depth develops a<strong>on</strong>tlnuously afterward6<br />

and at laat rsaahes ita maximum frost depth,<br />

the total frost heave aapaaity <strong>on</strong> the 60il<br />

aurfaoe inoreases very little and la relatively<br />

stable.<br />

The same criteri<strong>on</strong> ahould be adopted to oouat<br />

the muinurn frost depth. The frost penetrati<strong>on</strong>.<br />

however. whether it is direQtly rnenaumd<br />

or oalaulatBd and induaed from the empirical<br />

squati<strong>on</strong>t is different from the praotioal<br />

. frost depth value of frost heave meohanism.<br />

That froat heave being widely med in mrioua<br />

equati<strong>on</strong> direatly affeots the anti-frost damage<br />

maaures of hydraullo atruatures. So it la<br />

neceaaary to aohieve manimity of opini<strong>on</strong> of<br />

frost depth. and to adopt the snme standard<br />

in oder to be in comm<strong>on</strong> use.<br />

Frost heave in natural freezing layer is the<br />

natural phenomin<strong>on</strong> crented by the water and<br />

hent in Soil fluxing and phP8Oa ohinging below<br />

OOC. A oertah point in layer moves upwads<br />

al<strong>on</strong>g the normal line of the aooling fr<strong>on</strong>tal<br />

edge. in the meanwhile move9 downwards opposite<br />

to the dirooti<strong>on</strong>t so frost heave at<br />

certain point in freezing layer is equal in<br />

sieo and opposite in directi<strong>on</strong>. Moving upwnd<br />

makes sublayer pN98 tightly. Under the nati<strong>on</strong><br />

of frost, froat depth device is freesing up<br />

wlth freezing soil, which rises upwards aocompnnylng<br />

the increase of frost heave capacity<br />

and frost heave. See fi@uw 3.<br />

Ah lr<strong>on</strong>l heave<br />

t ' h<br />

So the value measured by the general meteorologioal<br />

stati<strong>on</strong> is the thiohess of the freezhg<br />

soil layer, not the pmotiaal frost depth.<br />

If the froat depth needs to be aohievedt the<br />

frost heave oapaoity muSt be mi8USed. For<br />

instance, an experiment in a foreia miverslty<br />

as fig. 4 shows,<br />

fiRure 4<br />

an example of frost heave va frost<br />

depth<br />

From the fiyre we see the appearance before<br />

and after freeling. The thickueas of freeelng<br />

soil layer is 60~10: frost heave oapacity 1s<br />

3Ocmi the maximum frost depth H - 6Oam - 30cm-<br />

30orn. Antl-frost remured ahould bo taken with<br />

3Ooml otherrise the ermr la great with 60cmt<br />

end its result is foreseeable. From this we<br />

om see that it la necessary to achieve unanimity<br />

of opini<strong>on</strong> of frost depth.<br />

2. soil PhySiQS Japan Muxiachengyi 1982,9<br />

3.9011 Mechanics China Wuhan Hydraulio<br />

and Electric College Feng Guod<strong>on</strong>g editor<br />

1984, 8<br />

1025

PRINCIPLES FOR COMPILING AN ATLAS OF SEASONAL<br />

FROST PENETRATION, JILIN, CHINA (1: 2000000)<br />

Zhang, Xing, Li, Yinr<strong>on</strong>g and S<strong>on</strong>g, Zhengyuan<br />

Institute of Water C<strong>on</strong>servancy, Jilin, China<br />

SYNOPSIS For purposes of engineering design an atlas has been compiled<br />

to reflect the<br />

dynamics of seas<strong>on</strong>ally frozen ground, and particularly the depth of frost penetrati<strong>on</strong> in soils under<br />

different freezing c<strong>on</strong>diti<strong>on</strong>s, variati<strong>on</strong>s in the freezing process with time during the freezing seas<strong>on</strong><br />

and interannual variati<strong>on</strong> in the depth of frost penetrati<strong>on</strong>. In a given geographical regi<strong>on</strong>,<br />

soil properties and the moisture c<strong>on</strong>tent of the soil prior to freezing are the major internal factors<br />

influencing the seas<strong>on</strong>al depth of frost penetrati<strong>on</strong>, while the thickness of snow cover and the<br />

freezing index, which very with latitude and altitute, are the main external factors. The dynamic<br />

of frost penetrati<strong>on</strong> in seas<strong>on</strong>ally frozen ground is shown in the atlas by the following four parameters:<br />

the standard frozen depth (Zo), the coefficient of variati<strong>on</strong> of frost depth (Cv), coefficient<br />

for the influence of snow cover (8) and the elapsed time of the freezing seas<strong>on</strong> (T).<br />

INTRODUCTION<br />

The mapping of seas<strong>on</strong>ally frozen ground is a<br />

complicated problem because of the variety of<br />

natural factors that deeply affect the process<br />

and result of ground freezing. At a given site,<br />

the positi<strong>on</strong> of the freezing fr<strong>on</strong>t varies with<br />

time, the maximum depth of frost penetrati<strong>on</strong><br />

differs from year to year; and at any time, the<br />

depth of frozen soil can vary by a factor of 2<br />

to 4 within a distance of a few kilometres.<br />

For engineering purpose, it is necessary to<br />

know the regime of seas<strong>on</strong>al freezing processes,<br />

i.e., to show the seas<strong>on</strong>ally frozen depth, the<br />

process of freezing vs time and the interannual<br />

variati<strong>on</strong>s in frozen depth each of which is<br />

shown in the atlas.<br />

In this paper the authors discuss the principles<br />

for Compilati<strong>on</strong> of the atlas seas<strong>on</strong>ally frozen<br />

ground in Jilin Province, China.<br />

TERMINOLOGY AND CONCEPTIONS<br />

The soil-type classificati<strong>on</strong> and terminology<br />

are based <strong>on</strong> the "Regulati<strong>on</strong>s for geotechnical<br />

tests SDSOI-79" promulgated by the Mini.stry of<br />

Water C<strong>on</strong>servancy and Electri,city, People's<br />

Republic of China.<br />

The period of time with a mean air temperature<br />

below 0°C is called the freezing seas<strong>on</strong>; the<br />

number of 10-day periods (T) is called the<br />

elapsed time of freezing seas<strong>on</strong>.<br />

The freezing index (F1) is defi.ned as the integrated<br />

area of temperature-time curve within<br />

the freezing seas<strong>on</strong> in "C.10 days.<br />

The period from' the beginning of the freezing<br />

seas<strong>on</strong> t o the time of maximum frost penetrati<strong>on</strong><br />

is the calculated durati<strong>on</strong> of the freezing<br />

seas<strong>on</strong> (TI).<br />

The period of time with mean daily air temperatures<br />

below O°C and the beginning of soil freezing<br />

is the pre-freezing period, in which t,he<br />

water c<strong>on</strong>tent of the soil is defined as the<br />

pre-freezing water c<strong>on</strong>tent (W, %).<br />

The term seas<strong>on</strong>ally frozen depth refers to the<br />

maximum value of frost penetrati<strong>on</strong>,.including<br />

frost heave.<br />

STANDARD FROZEN DEPTH<br />

The standard frozen depth is defined as the<br />

mean depth of frost penetrat-i<strong>on</strong> in fine-grained<br />

inorganic soil with a pre-freezing water c<strong>on</strong>tent<br />

of 25% (Wo-standard pre-freezing water<br />

c<strong>on</strong>tent), observed €or several years at a snowfree<br />

meteorological observati<strong>on</strong> site (Central<br />

Meteorological Bureau, 1979b)<br />

A standard frozen depth is dependent mainly <strong>on</strong><br />

the freezing index, as c<strong>on</strong>trolled by latitude<br />

(L) and altitude (H) of the observati<strong>on</strong> site,<br />

and is affected by local c<strong>on</strong>diti<strong>on</strong>s such as<br />

surface cover, hydrogeology and engineeringgeology<br />

*<br />

The standard frozen depth is a site-specific<br />

characteristic determined by statistical analysis<br />

of observatory data. It is a basic index<br />

in the mapping of seas<strong>on</strong>ally frozen ground.<br />

RELATIONSHIP BETWEEN STANDARD FROZEN DEPTH AND<br />

FREEZING INDEX<br />

From statistical analysis of several years data<br />

1026

from 30 observati<strong>on</strong> sites it is known that the<br />

standard frozen-depth (Zo,m) is dependent <strong>on</strong> the<br />

freezing index F1:<br />

regi<strong>on</strong>s east to west.<br />

Regi<strong>on</strong> I, the Changbaishan Natural Envir<strong>on</strong>ment<br />

Protected Regi<strong>on</strong>, is very mountainous and F, is<br />

found t o be closely-related to latitude.<br />

where a, -coefficient of the standard forzen<br />

depth, known to be 0.115 in Jilin<br />

Province: and<br />

F1- mean value of freezing index for<br />

several years.<br />

At the 30 observati<strong>on</strong> sites,the fine-grained<br />

particle c<strong>on</strong>tent of the seas<strong>on</strong>ally frozen soils<br />

ranges from 48 to 78%, in which salt c<strong>on</strong>tent is<br />

11 to 74%,and the clay c<strong>on</strong>tent is from 2 to 34%.<br />

At 15 sites, the depth of the groundwater<br />

table is less than 4 m. Four observati<strong>on</strong> sites<br />

are <strong>on</strong> frost susceptible soils with frost heaving<br />

amounts of 10 to 31.5 cm, or 6 to 25% of the<br />

maximum frozen depth.<br />

INFLUENCE OF PRE-FREEZING WATER CONTENT ON<br />

DEPTH OF FROST PENETRATION<br />

At a snow-free site, as the pre-freezing water<br />

c<strong>on</strong>tent W is not equal to Way the mean frozen<br />

depth for any year (Z) differs from Zo, and can<br />

be expressed by the following equati<strong>on</strong>:<br />

z = KwZo<br />

where K,-<br />

the revised coefficient of water<br />

c<strong>on</strong>tent<br />

W<br />

where L- latitude,in degrees;<br />

H- elevati<strong>on</strong> in 100 m.<br />

The correlati<strong>on</strong> coefficient of Eq.(5) is 0.934.<br />

In Regi<strong>on</strong> 11, the central-eastern hills,<br />

PI= -665.7+18.2L+13.68 (6)<br />

The correlati<strong>on</strong> coefficient of Eq.(6) is 0,838.<br />

Substituting Eq.(5) and (6) into Eq.(l), the<br />

relati<strong>on</strong> of 2, to L and H can be derived.<br />

Inprinciple the formulae Eq.(5) and (6)should<br />

be applied <strong>on</strong>ly to those areas lower than 1000<br />

m a.s.1.<br />

In Regi<strong>on</strong>s I11 and IV, the Central-western Bills<br />

and the Western Plain, the relief is less than<br />

100 m, the distributi<strong>on</strong> of mainly depends <strong>on</strong><br />

latitude,and the observed data of 2, are applied<br />

directly to mapping.<br />

EFFECTS OF SNOW COVER ON THE MEAN VALUE OF<br />

SEASONAL FROST DEPTH<br />

An increase in the de th of snow cover will<br />

reduce the effect of %1 <strong>on</strong> the seas<strong>on</strong>al frost<br />

- depth, So, fl in Eq.(l) should be changed to<br />

F2, so:<br />

Equati<strong>on</strong> (4), although it is approximate theoretically,<br />

has proved by comparis<strong>on</strong> with field data<br />

to be accurate enough for practical purposes<br />

(Zhang, 1983). The water c<strong>on</strong>tent value used for<br />

statistical analysis ranges from 8 to 30%.<br />

VARIATION IN<br />

Within the Jilin Province, 187000 km' in area,<br />

there are 48 observati<strong>on</strong> sites. In additi<strong>on</strong>,<br />

data from 20 adjacent sites were used. Thus,<br />

in a total area of 260000 kma, data from 68 observati<strong>on</strong><br />

sites were used in thP analysis: in<br />

other words, there wef;e more than 10 observati<strong>on</strong><br />

sites for each 100 cm <strong>on</strong> the map (1:2000000).<br />

This is dense enough for mapping.<br />

In the mountainous regi<strong>on</strong>s, variati<strong>on</strong> in elevati<strong>on</strong><br />

affects the values of F1 and 2,. The 2,<br />

increases by h<br />

elevati<strong>on</strong>.<br />

to 7 cm per 100 m increase in<br />

Jilin Province can be divided into four physical<br />

where B - coefficient shew ing the effect of<br />

snow cover <strong>on</strong> F1<br />

B = 0.193 + 0. '402 1, (8)<br />

where ix- mean depth of snow cover for several<br />

years, and can be determined from<br />

Eq. (9),<br />

- C Hi<br />

H, =- 120<br />

where Hi-<br />

daily depth of snow cover during the<br />

period from the beginning of November<br />

the end of February, in centimetres.<br />

INTERANNUAL VARIATION OF FROST PENETRATION<br />

The depth frost penetrati<strong>on</strong> at a any site can<br />

vary greatly from year to year. The coefficient<br />

of variability (C,) ranges from 0.04 to 0.27 in<br />

1027

Jilin Province.<br />

Based <strong>on</strong> analysis of empirical frequency curves<br />

from 100 sites within the temperate z<strong>on</strong>e in China<br />

(Central Meteorological Bureau, 1979a), it is<br />

c<strong>on</strong>sidered that the third type of Poiss<strong>on</strong> normal<br />

distributi<strong>on</strong> curve, with a skewness coefficient<br />

(C,)-O can be the theoretical distributi<strong>on</strong> curve<br />

for the depth of frost penetrati<strong>on</strong> (Zhang and<br />

Wang, 1981). The Cv value is the index to show<br />

the interannual variati<strong>on</strong> of seas<strong>on</strong>al frost<br />

penetrati<strong>on</strong>.<br />

It is necessary to examine carefully the observed<br />

data to determine the value of Cv seas<strong>on</strong>aly<br />

frost penetrati<strong>on</strong> under natural c<strong>on</strong>diti<strong>on</strong>s, because<br />

any change in positi<strong>on</strong> will cause the<br />

observed data to vary widely.<br />

Observati<strong>on</strong>s at 40 meteorological stati<strong>on</strong>s for<br />

25 years show that the thicker the snow cover,<br />

the greater will be the value of Cv.<br />

C, = 0,081 t 0.135Tx (10)<br />

The correlati<strong>on</strong> coefficient for Eq.(lO) is 0.92.<br />

In this province, H, is less than 16 cm.<br />

From Eq.(lO), it can be shown that-if jx=o,<br />

Cv=0,081. A calculati<strong>on</strong> based <strong>on</strong> F1 shows that<br />

the Cv value should be O.OG2,however. The-fact<br />

that two values are close indicates that F1 is<br />

the major factor in c<strong>on</strong>trolling the depth of frost<br />

penetrati<strong>on</strong> at a snow-free site.<br />

PROGRESS OF FROST PENETRATION VS TIME DURING<br />

THE FREEZING PERIOD<br />

The progress of frost penetrati<strong>on</strong> can be expressed<br />

by 5q.(ll).<br />

where a(t)-<br />

time-course coefficient of the<br />

depth of frost penetrati<strong>on</strong>;<br />

t - elapsed time, in 10-day periods: a 4<br />

2 - mean annual value of maximum depth<br />

of frost penetrati<strong>on</strong>.<br />

In the temperate z<strong>on</strong>e of China, can be expressed<br />

by Eq.(12),<br />

where, the value of in depends mainly <strong>on</strong> the<br />

pre-freezing water c<strong>on</strong>tent (W). As W ranges increases<br />

from 8 t o 30%, m increases from 0.51<br />

to 0.73.<br />

As the durati<strong>on</strong> of freezing seas<strong>on</strong> (T) is less<br />

than is IO-day periods depth of frost penetrati<strong>on</strong><br />

will c<strong>on</strong>tinue to increases after the freezing<br />

seas<strong>on</strong>, but the amount of chis increase will<br />

not exceed 5% of the annual frost depth. This<br />

situati<strong>on</strong> often occurs in regi<strong>on</strong>s near the southern<br />

limit of the disc<strong>on</strong>tinuous permafrost z<strong>on</strong>e.<br />

As T

REFERENCES<br />

Central Meteorological Bureau of China, (1979a).<br />

Climatic atlas, China. p.222-223, Cartographic<br />

Publishing House.<br />

Central<br />

.<br />

Meteorological Bureau of China, (1979b).<br />

Regulati<strong>on</strong>s for surface air observati<strong>on</strong>.<br />

Meteorological Publishing House.<br />

Zhang Xing and Wang Shiduo, (1981). Statistical<br />

characteristics of seas<strong>on</strong>al frozen<br />

ground in Jilin, China. Journal of Glaciology<br />

and Cryopedology, (3), 37-46.<br />

Zhang Xing. (1983). Natural freezing penetrative<br />

rate of the seas<strong>on</strong>ally frozen ground in<br />

the medium temperate z<strong>on</strong>e of China. Pro.2nd<br />

Chinese Nati<strong>on</strong>al <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>,<br />

p.138-145, Gansu People's Publishing House.<br />

1029

SEGREGATION FREEZING OBSERVED IN WELDED<br />

TUFF BY OPEN SYSTEM FROST HEAVE TEST<br />

Akagawa, Satoshi, Goto, Shigeru and Saito, Akira<br />

Shimizu Corporati<strong>on</strong>, Tokyo, Japan<br />

SYNOPSIS Segregati<strong>on</strong> freezing that results in ice lens growth is obaerved during<br />

freezing in saturated and unsaturated porous rocks. The porous rock heaves in a way similar to<br />

soil frost heaving, cracking the rock, which has the tensile strength of 1.4 MPa. The heave<br />

susceptibility of the rock was found to be lower than that of frost-susceptible soil; however,<br />

the rest of the heaving properties appear to be aimilar. Almost the same segregati<strong>on</strong> temperatures<br />

at which the final ice lens segregates are obtained in two tests from the ice lenses'<br />

lwcati<strong>on</strong> and temperature profiles, regardless of the water saturati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong> of 92 and 100%.<br />

However, the heave and water intake properties seem to differ with the water saturati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>.<br />

The growth of ice lenses in a porous rock reflects the possibility of weathering by<br />

segregati<strong>on</strong> freezing during rock freezing.<br />

INTRODUCTION<br />

Extensive studies o f the weathering of rocks<br />

due to freeze-thaw cycles have been c<strong>on</strong>ducted<br />

in the past: however, there has been no<br />

general agreement <strong>on</strong> a weathering process<br />

(white, 1976). In <strong>on</strong>e special case of rock<br />

weathering, the frost shattering of a frozen<br />

porous rock was studied by Fukuda and Matuoka<br />

(1982); the data showed a possibility of<br />

Segregati<strong>on</strong> freezing, which may have resulted<br />

in the growth of visible or invisible ice<br />

lenses in the rock. Their paper clearly<br />

dem<strong>on</strong>strated the existence of the pore-water<br />

pressure gradient in the unfrozen part of the<br />

unsaturated rock while freezing.<br />

The existence of the pore-water pressure<br />

gradient reveals a possibility of high sucti<strong>on</strong><br />

force generati<strong>on</strong> near the freezing fr<strong>on</strong>t<br />

(originally Taber, 1929). The sucti<strong>on</strong> force<br />

will be caused by segregati<strong>on</strong> freezing instead<br />

of in situ freezing (Takagi, 1980). Segregati<strong>on</strong><br />

freezing results in the cracking of the<br />

soil skelet<strong>on</strong> through ice lensing. Obviously,<br />

if the segregati<strong>on</strong> freezing takes place in the<br />

rock, it results in weathering.<br />

In this paper, the possibility of segregati<strong>on</strong><br />

freezing in porous rock is observed by two<br />

open- system frost heave tests, Test A and<br />

Test I3, using the same kind of rock that was<br />

cored from the same area as Fukuda and Matuoka<br />

(1982). As a result, segregati<strong>on</strong> freezing in<br />

the rock is c<strong>on</strong>firmed by the growth of ice<br />

lenses. In this paper the characteristics of<br />

the growing ice lenses in a porous rock are<br />

also reported, and compared with those of soil<br />

freezing .<br />

FROST HEAVE TEST<br />

Test<br />

Frost heave tests were c<strong>on</strong>ducted with the apparatus<br />

shown h.Fig. 1. The maximum specimen<br />

size that can be tested in this apparatus is<br />

30 cm in height and 30 cm in diameter. In,<br />

these tests, the specimen diameter was reduced<br />

to 29 cm to reduce side fricti<strong>on</strong>, and height<br />

was reduced to 25 cm to make room for NFS<br />

(n<strong>on</strong>-frost-susceptible) sand at both ends of<br />

the specimen, as shown in pig. 2. Water sealing<br />

of the side wall of the specimen was obtained<br />

by a I-mu-thick, flexible silic<strong>on</strong>e rubber<br />

jacket, a160 shown in Fig. 2.<br />

The temperature of the test specimen was c<strong>on</strong>- ".<br />

trolled through both the top and bottom pedestals.<br />

The temperature of the upper pedestal<br />

was c<strong>on</strong>trolled by circulating ethylene glycol<br />

through the pedestal. The lower pedestal temperature<br />

was maintained at a selected positive<br />

temperature by c<strong>on</strong>trolling the temperature of<br />

the water in the pedestal. The water is c<strong>on</strong>nected<br />

to the pressurized pore water reservoir<br />

tank and is supplied to the specimen through<br />

the porous plate as pore water. Freezing Was<br />

initiated from the upper pedestal downward.<br />

Between the upper pedestal and the specimen,<br />

NFS sand was placed to avoid supercooling and<br />

to improve distributi<strong>on</strong> of the overburdem<br />

pressure. The space between the acrylic<br />

Plexiglas cell and the silic<strong>on</strong>e rubber<br />

membrane was filled with gelatine to prevent<br />

c<strong>on</strong>vective heat transfer. Overburden pressure<br />

was applied by an air actuator except for the<br />

low pressures of 5 and 7.5 kPa used in Test A.<br />

Those two low pressures were applied with<br />

weights.<br />

1030

Cold<br />

Side<br />

-<br />

9-<br />

Si I ir<strong>on</strong>e<br />

- Rubber<br />

2 Porous plate<br />

3 Pore water<br />

4 Heating coil<br />

Specimen<br />

8-<br />

-Gelatine<br />

Thermo-<br />

.,couplrs<br />

transducer<br />

6 Double acry-<br />

7 Air pressure<br />

Fig. 2.<br />

300 mm<br />

5<br />

,.:<br />

i<br />

Specimen c<strong>on</strong>figurati<strong>on</strong>.<br />

Fig. 1.<br />

Frost heave test apparatus.<br />

TABLE I<br />

Physical and Mechanical Properties<br />

oE the Porous Rock<br />

Unfrozen<br />

Frozen<br />

Dry Saturated Saturated<br />

(200C) (-5'C) (-15'C) (-25-C)<br />

Apparent specific 1.40 1.72 " " "<br />

gravity<br />

Porosity (X) 37.9 "<br />

"<br />

Compressive 14.6 6.6 12.0 18.5 26.2<br />

Strength<br />

(MN/ma ) Tensile 1.6 1,4 1.4 4.4 5.7<br />

(split test)<br />

Tangent modulus 4812 3548 2859 2068 3763<br />

(MN/rn'<br />

Secant modulus 4596 3126 3097 3410 6281.<br />

(MN/m')<br />

Elastic wave 2.45 2.72 3.20 3.67 3.89<br />

velocity (bn/s)<br />

Poiss<strong>on</strong>'s ratio 0.17 0.28 0.46 0.38 0.42<br />

Since the apparatus was placed in a walk-in<br />

type coldroom in which the temperature was<br />

maintained at Okl'C, lateral heat flow to or<br />

from the specimen was minimized. The frost<br />

heave was measured with a digital deformati<strong>on</strong><br />

gauge that has an accuracy of +0.001 mm.<br />

1031<br />

Since this measuring system has no analog circuit,<br />

no drift was expected. The pore water<br />

flow was measured with an electrical water<br />

depth meter that was installed in the pore<br />

water reservoir tank. The tank had a 10-L<br />

capacity. The temperature of the specimen was<br />

measured with 10 thermocouples that were installed<br />

5 cm info the side of the specimen.<br />

The locati<strong>on</strong>s of the thermocouples are shown<br />

in Fig. 2. All these data were recorded every<br />

hour by a computerized data acquisiti<strong>on</strong> system.<br />

Sampmrtles<br />

The material used in this experiment is a<br />

rhyolite-welded-tuff that was obtained from an<br />

ocean volcanic deposit. This rock is characterized<br />

by a cemented structure with air<br />

bubble and flow line features. This rock is<br />

made up of about 15% by volume of 0.2- to 2-mm<br />

plagioclase grains and 0.2- to 1-mm quartz<br />

grains such as phenocryst, b<strong>on</strong>ded by 85%<br />

vitreous groundmass. The groundmass is<br />

str<strong>on</strong>gly modified by diagenesis, and volcanic<br />

glass and other minerals are changed to<br />

clinoptilolite, chlorite, and m<strong>on</strong>tmorill<strong>on</strong>ite.<br />

The physical and mechanical properties of this<br />

rock are listed in Table 1 for the c<strong>on</strong>venience<br />

of the future diswasi<strong>on</strong> of a relati<strong>on</strong> between<br />

frost heave force and rock strength.<br />

yest<br />

... .<br />

The test c<strong>on</strong>diti<strong>on</strong>s for the frost heave tests<br />

are listed in Table 2. The water saturati<strong>on</strong><br />

c<strong>on</strong>diti<strong>on</strong>s for the twa tests were different.<br />

For Test A, the sample was submerged in water<br />

for a week, leaving 1 cm of the upper part in<br />

air. In this case, the degree of saturati<strong>on</strong><br />

was 92%. For Test B, the sample was submerged<br />

in water as in Test A but for 3 m<strong>on</strong>ths. In<br />

this case, the degree of saturati<strong>on</strong> was<br />

measured as 100%. The overburden pressure wa6<br />

changed several times from 5 KPa to 0.2 MPa in

TABLE I1<br />

Test C<strong>on</strong>diti<strong>on</strong>s<br />

Test name Water Pressure Temperature<br />

saturati<strong>on</strong><br />

c<strong>on</strong>diti<strong>on</strong> Overburden Pore water Warm Cold<br />

pressure pressure<br />

(X) WW (KPd ("C) ("C)<br />

Test A 92 5, 75, 30, 50, 3 4.0 -14.5<br />

100, 200<br />

Test B 100 60, 105, 150, 3 4.3 -14.9<br />

200<br />

Test A and 60 KPa to 0.2 Mea in Test B to observe<br />

the influence of overburden pressure <strong>on</strong><br />

the frost heaving characteristics. Before the<br />

frost heave tests, the specimens were maintained<br />

at the warm side temperatures, shown in<br />

Table 2, for a week to establish uniform<br />

initial temperature c<strong>on</strong>diti<strong>on</strong>s. Then the cold<br />

side temperatures were dropped to those shown<br />

in Table 2 for the teat initiati<strong>on</strong>. The pore<br />

water pressure was set at 3 KPa at the top of<br />

the specimen to maintain slight positive gauge<br />

pressures throughout it.<br />

TEST RESULTS AND DISCUSSION<br />

During the frost heave tests, both samples<br />

heaved as shown in Fig. 3. Segregati<strong>on</strong> freez-<br />

0.1<br />

S<br />

0<br />

-5<br />

Fig. 3.<br />

flmm (hr)<br />

0 250 500 750 1000 1250<br />

Time (hr)<br />

Heave and water intake characteristics (numbers in [c] are thermocouple numbers).<br />

1032

ing activity in the rock is c<strong>on</strong>firmed by<br />

analyzing the heave and water intake curves<br />

and the ice lens distributi<strong>on</strong>.<br />

water intake vrowerties<br />

The heave and water intake curves are shown in<br />

Fig. 3a with values of applied overburden<br />

pressures. The heave rate and water intake<br />

rate are shown in Fig. 3b: they are calculated<br />

by subtraating adjacent pairs of heave or<br />

water intake data and dividing by the time<br />

difference of 1 hour. The specimen temperatures<br />

are shown in Fig. 3c. The temperatures<br />

were measured with 10 thermocouples installed<br />

in the specimens, as shown in Fig. 2.<br />

During the frost heave test's, both samples<br />

heaved about 2 CIR at 1,000 hours. The heave<br />

amount observed in Test A, which used the unsaturated<br />

sample, is slightly smaller than<br />

than in Test B, which used the saturated<br />

sample, although the overburden pressure in<br />

Test B was usually larger than Test A. The<br />

heave amount observed in Test B is larger than<br />

the water intake amount, whereas the inverse<br />

relati<strong>on</strong> was observed in Test A. One possible<br />

explanati<strong>on</strong> of these properties will be discussed<br />

later.<br />

The frost heave and heave rate curves acquired<br />

from Test A show that heaving started at time<br />

t=55 hours after an initial slight shrinkage.<br />

The heave and heave rate curves of Test I3 show<br />

heaving that is similar to that of the<br />

saturated frost-susceptible soil observed in a<br />

frost heave test c<strong>on</strong>ducted with the same<br />

specimen size, overburden pressure, and freezing<br />

c<strong>on</strong>diti<strong>on</strong>s (Akagawa, 1983).<br />

In general, a saturated frost-susceptible soil<br />

first shows in situ freezing, expelling pore<br />

water if overburden pressure is high. The<br />

heave rate due to in situ freezing then<br />

decreases sharply as the freezing rate<br />

decreases and segregati<strong>on</strong> freezing becomes<br />

predominant, increasing the heave rate and<br />

drawing the pore-water into the sample. When<br />

segregati<strong>on</strong> freezing becomes dominant, ice<br />

lenses start to grow following the depth of<br />

the zero isotherm, and the heave amount is 9%<br />

greater than the water intake amount (Akagawa,<br />

in press). The data shown in Fig. 3 may be<br />

understood as following the heaving modes<br />

found in the soil menti<strong>on</strong>ed above:<br />

1) A period of predominant in situ freezing.<br />

Negative water intake rates were observed<br />

in the first 20 hours in both Test A and<br />

Test B. These data reveal that in situ<br />

freezing was predominant during this<br />

period.<br />

2) A transiti<strong>on</strong> period from in situ freezing<br />

to segregati<strong>on</strong> freezing.<br />

The water intake rates turned positive and<br />

increased steeply during the periods of t=<br />

20 to 55 hours in Test A and 20 to 65<br />

hours in Test B. These data reveal that<br />

in situ freezing was tapering off and<br />

segregati<strong>on</strong> freezing was becoming predominant<br />

.<br />

(3) A period of predominant segregati<strong>on</strong> freezing.<br />

The ratios of heave rate to water intake<br />

rate, (dh/dt)/(dw/dt), at each recorded<br />

time seem to be about 1.09 after 55 hours<br />

in Test A and 65 hours in Test B, except ,<br />

for a period from t=20 to 380 hours in<br />

Test A. These data reveal that segregati<strong>on</strong><br />

freezing was predominant in this period.<br />

From this point of view c<strong>on</strong>cerning the heave<br />

and water intake properties, it may be said<br />

that segregati<strong>on</strong> freezing has been taking<br />

place in both unsaturated and saturated porous<br />

rock and that expansi<strong>on</strong> due to in situ<br />

freezing has also peen active in Test B, in at<br />

least the first 20 hours of freezing, which<br />

used a saturated sample.<br />

Ice lens distributi<strong>on</strong><br />

After the frost heave tests, both specimens<br />

were cut to observe the water c<strong>on</strong>tent profile<br />

and ice lens distributi<strong>on</strong> to c<strong>on</strong>firm the<br />

segregati<strong>on</strong> freezing. Results of these observati<strong>on</strong>s<br />

are shown in Fig. rla and b. Several<br />

visible ice lenses were observed, and their<br />

distributi<strong>on</strong> and variati<strong>on</strong> of thickness were<br />

found to resemble ice lenses seen in frost<br />

susceptible soils; however, there were fewer<br />

visible ice lenses in the rock than in the<br />

soil. Therefore, the occurrence of segregati<strong>on</strong><br />

freezing, which was revealed by the heave<br />

and water intake properties, was c<strong>on</strong>firmed by<br />

the existence of the segregated ice lenses.<br />

Additi<strong>on</strong>al experimental results of note for<br />

the frost heave study are listed below, and<br />

are compared to the heave characteristics of<br />

the above-menti<strong>on</strong>ed frost-susceptible-soil:<br />

Heave rate durina Eeareaati<strong>on</strong> freezinq<br />

The heave rate of the rock appeared to remain<br />

c<strong>on</strong>stant at relatively low values such as 0.01<br />

to 0.03 m/hr shown in Fig. 3b, whereas the<br />

heave rate of the frost-susceptible soil,<br />

which was observed in a frost heave test using<br />

the same specimen size and similar freezing<br />

c<strong>on</strong>diti<strong>on</strong>s, varied from 0.3 to 0.02 m/hr as<br />

time elapsed (Akagawa, 1983).<br />

effect of overburden wressure <strong>on</strong> heave and<br />

water intake rate durina seareaati<strong>on</strong> freezinq<br />

The heave and water intake rates at each overburden<br />

pressure during segregati<strong>on</strong> freezing<br />

are plotted in Fig. 5. AS is generally accepted<br />

in soil frost heave studies, a higher<br />

overburden pressure causes a lower heave rate.<br />

The same situati<strong>on</strong> applies for rock heaving.<br />

effect of unsaturati<strong>on</strong> <strong>on</strong> frost heavinq<br />

In Test A, no heaving was observed during the<br />

period between t=O to 55 hours, but slight<br />

heaving was observed in Test B during t=O to<br />

65 hours, as shown in Fig. 3a. The Water<br />

intake rate was higher than the heave rate<br />

between t=55 to 380 hours in Test A, whereas<br />

the rest of the data in Fig. 3b show an inverse<br />

relati<strong>on</strong>ship between the heave rate and<br />

the water intake rate. One possible explanati<strong>on</strong><br />

for the appearance of the heaving in Test<br />

B in this period is that the excess pore<br />

water, which was locally developed by in situ<br />

freezing in the saturated sample, cracked the<br />

rock, causing expansi<strong>on</strong>, and absence of the<br />

heaving in Test A is thought to be the result<br />

of insufficient excess pore water for cracking<br />

the unsaturated specimen. This lower heave<br />

1033

Wator C<strong>on</strong>tmt ( x)<br />

80 60 40 20 0<br />

80 H<br />

60 40 a 20 0<br />

I<br />

Warm Side<br />

b<br />

Cold Side<br />

Temperature<br />

C<br />

("C)<br />

Fig. 4.<br />

Warm<br />

Side<br />

Ice lens distributi<strong>on</strong> and segregati<strong>on</strong> temperature of the final ice lens<br />

(FIL). (a - water c<strong>on</strong>tent; b - ice lens distributi<strong>on</strong>; c - temperature profile<br />

when final ice lens starts to grow).<br />

4 that of Test B. This experimental result may<br />

4 ' reveal that although segregati<strong>on</strong> freezing was<br />

K<br />

P<br />

taking place predominantly in both the saturated<br />

and unsaturated samples, the unsaturafed<br />

porous rock heaves less by segregati<strong>on</strong> freez-<br />

E - ing than saturated <strong>on</strong>e does. This behavior is<br />

same as that found in soils.<br />

-lati<strong>on</strong> betsen shut-off Dressure and tmz<br />

H strenaa<br />

m ;,<br />

Another interesting result is revealed by ex-<br />

2<br />

trapolating the relati<strong>on</strong> between heave rate or<br />

$<br />

r water intake rate and overburden pressure in<br />

0 Fig. 5 to a higher overburden pressure. As is<br />

0.01 0.1 1 seen in this figure, heave will cease at an<br />

overburden pressure of about 1 MPa, although<br />

Overburden Pressure ( MPa )<br />

Fig. 5. Effect of surcharge pressure <strong>on</strong> frost<br />

heave rate (dh/dt) and water intake rate (dw/dt)<br />

(The triangle and circle data points represent<br />

the results for Test A and Test B, respectively.<br />

White and black points represent heave rate and<br />

water intake rate, respectively) .<br />

rate compared to the water intake rate during<br />

the early stage of freezing in Test A might be<br />

the cause of the higher water intake amount<br />

than heave amount in this test.<br />

As shown in Fig. 5, all data agree well with a<br />

relati<strong>on</strong> (dh/dt)/ (dw/dt) 1. 09, except for<br />

the water intake rate data for Test A at an<br />

overburden pressure of 5 KPa. These unc<strong>on</strong>forming<br />

data can be explained by the mechanism<br />

of intake water filling the void space of the<br />

pores in the unsaturated sample, as menti<strong>on</strong>ed<br />

above. The remainder of the data seem to hold<br />

to that relati<strong>on</strong> (dh/dt)/ (dw/dt) 1.09; however,<br />

the heave rate of Test A is lower than<br />

1034<br />

the shut-off pressure of the final ice lens<br />

was expected to be about 1.4 MPa, which is the<br />

tensile strength of this sample. This relati<strong>on</strong><br />

may lead to a study of force balance at<br />

segregating ice, but several experiments<br />

should be d<strong>on</strong>e to examine the reliability of<br />

the extrapolati<strong>on</strong>, the properties of pore<br />

water, and the mechanisms of cracking in the<br />

porous rock, for example.<br />

Seareaati<strong>on</strong> freezing femeerature of the final<br />

lens<br />

From the sketches of the ice Lens distributi<strong>on</strong><br />

for the two tests, the segregati<strong>on</strong> temperatures<br />

for the final ice Lenses of Test A and B<br />

are determined. The depth corresp<strong>on</strong>ding to<br />

the final ice lens is assumed to be equal to<br />

the cold side of the final ice lens. This<br />

means that the heave amount for the rest of<br />

the ice lenses was negligibly small. Since<br />

the final ice lens thickness is about 10 times<br />

that of the rest of the ice lenses, total,<br />

this assumpti<strong>on</strong> may reas<strong>on</strong>ably be accepted as<br />

seen in Fig. 4. The time when the final ice

lens started to grow is assumed to be in a<br />

period between when the water intake rate is<br />

at a maximum and a time when the amount of<br />

heave reaches a value equal to the total heave<br />

minus the thickness of the final ice lens.<br />

These periods are obtained from Fig. 3a and b<br />

as t=55 to 160 hours for Test A and t-65 to<br />

200 hours fox Test B, because the thickness of<br />

the final ice lenses were determined to be 21<br />

mm for Test A and 18 mm for Test B from<br />

sketches shown in Fig. 4b. During these two<br />

time periods, the temperature profiles seem to<br />

be stabilized as seen in Fig. 3c. Therefore,<br />

the mean values of each of the two corresp<strong>on</strong>ding<br />

depths are used as the temperatures<br />

when the final ice lenses started to<br />

grow and are shown in Fig. 4c. Since the ice<br />

lenses have wavy shapea, the depth and temperature<br />

of the final ice lens might vary by<br />

approximately +3 mm and f0.25'Cr respectively.<br />

From this figure the segregati<strong>on</strong> temperatures<br />

of the final ice lenses were found to be<br />

-1.45f0.25'C for Test A and - 1.4+0.25'C for<br />

Test B. These segregati<strong>on</strong> temperatures are<br />

somewhat lower those that of frost-susceptible<br />

soils (K<strong>on</strong>rad and Morgenstern, 1982: Ishizaki,<br />

1985; Akaqawa, in press). This tendency may<br />

be related to the high tensile strength of the<br />

rock compared to that of the soils (Radd and<br />

Oertle, 1966; Miller, 1978: Takagi, 1980:<br />

Gilpin, 1980: Takashi et al., 1981; Horiguchi,<br />

1987).<br />

Another result acquired from this experiment<br />

is the c<strong>on</strong>cordance of the segregati<strong>on</strong> temperature<br />

of the unsaturated sample and the saturated<br />

sample, although the saturated sample<br />

heaves more than does the unsaturated sample.<br />

This result may reveal that the same value of<br />

frost heaving force that cracked the specimen<br />

was generated at the place where the ice lens<br />

was segregating and the difference in the<br />

heave amount may be caused by the permeability<br />

of the water path to the segregating ice.<br />

CONCLUSIONS<br />

One weathering process of a porous rock,<br />

rhyolite-welded-tuff, was discussed with data<br />

obtained from open-system frost heave tests.<br />

Both saturated and unsaturated (Sr=92%)<br />

samples heaved c<strong>on</strong>siderably.<br />

The mode of heaving was viewed from the analogy<br />

of the frost heaving properties, heave<br />

and/or water intake amount and rate of soil.<br />

The heaving observed in the unsaturated sample<br />

was interpreted as heaving due to Segregati<strong>on</strong><br />

freezing, whereas the heaving observed in the<br />

saturated sample was interpreted as due to in<br />

situ and segregati<strong>on</strong> freezing. These interpretati<strong>on</strong>s<br />

were c<strong>on</strong>firmed by observati<strong>on</strong> of<br />

the segregated ice lenses that grew by cracking<br />

the Specimen, which has the tensile<br />

strength of 1.4 MPa.<br />

The temperatures at the warm side of the final<br />

ice lenses, segregati<strong>on</strong> temperature, in both<br />

saturated and unsaturated rocks were determined<br />

as -1.45+0.25'C and -1.40+0.2'5"C from<br />

the final ice lens locati<strong>on</strong>s and temperature<br />

profiles. This similarity of the segregati<strong>on</strong><br />

temperatures and the test results that the<br />

unsaturated rock heaved less than the saturated<br />

rock implied that the similar values of the<br />

frost heave force, sucti<strong>on</strong> force in pore<br />

water, were generated at the final ice lenses<br />

and the permeability of the water path to the<br />

ice lens causes the heave amounts to differ.<br />

In c<strong>on</strong>clusi<strong>on</strong>, this particular porous rock is<br />

weathered by segregati<strong>on</strong> freezing, which<br />

cracks the structure under relatively mild<br />

negative temperatures at about -1.4 to -1.5'C,<br />

even in a slightly unsaturated c<strong>on</strong>diti<strong>on</strong>.<br />

ACKNOWLEDGMENT<br />

The author thanks Dr. S. Kinoshita and Dr. F.<br />

Fukuda of the Institute of Low Temperature<br />

Science , Hokkaido University, for their<br />

valuable suggesti<strong>on</strong>s. The author is also<br />

indebted to Dr. Y. Nakano, Dr. R. Berg and E.<br />

Chamberlain of USACRREL for their comments and<br />

stimulating discussi<strong>on</strong>s.<br />

REFERENCES<br />

Akagawa, S (1983).<br />

Relati<strong>on</strong> between frost heave and specimen<br />

length. <strong>Research</strong> report of Shimizu Institute<br />

of Technology. Tokyo: ShimizuCo (formally<br />

presented at 4th Int. C<strong>on</strong>f. <strong>Permafrost</strong>).<br />

Akagawa, S (in press). Experimental study of<br />

frozen fringe characteristics.<br />

J. Cold Regi<strong>on</strong>s Sci. Tech.<br />

Fukuda, I & Matuoka, T (1982). Pore-water<br />

pressure profile in freezing porous rocks.<br />

Low Temperature Science, Ser. A, (41), 217-<br />

224.<br />

Gilpin, R R (1980). A model for the predicti<strong>on</strong><br />

of ice lensing and frost heave in soils.<br />

Water Resource <strong>Research</strong>, 16, (5), 918-930.<br />

Horiguchi, K (1987). An osmotic model for soil<br />

freezing.<br />

J. Cold-Regi<strong>on</strong>s Sci. Tech, 14, (l), 13-22.<br />

IShiZaki, T (1985).<br />

Experimental study of final ice lens growth<br />

in partically frozen saturated soil. Proc.<br />

4th Int. Symp. Ground Freezing, 71-78.<br />

Miller, R D (1978).<br />

Frost heaving in n<strong>on</strong>-colloidal soils. Proc.<br />

3rd Int. C<strong>on</strong>f. <strong>Permafrost</strong>, 962-967.<br />

Radd, F J & Oertle, D n (1966)*<br />

Experimental pressure studies <strong>on</strong> frost heave<br />

mechanisms and the growth-fusi<strong>on</strong> behavior of<br />

ice. Proc. 2nd Int. C<strong>on</strong>f. <strong>Permafrost</strong>, 377-<br />

284.<br />

Taber, S (1929). Frost heaving.<br />

Journal Of Geology, 37, (l), 428-461.<br />

Takagi, S (1980). The adsorpti<strong>on</strong> force theory<br />

of frost heaving.<br />

Cold Regi<strong>on</strong>s Science and Technology, 3, 57-<br />

81.<br />

Takashi, T, Ohrai, T, Yamamoto, H & Okamoto, J<br />

(1981). Upper limit of heaving pressure<br />

derived by pore water pressure measurements<br />

of partially frozen soil.<br />

Engineering Geology, 18, 245-257.<br />

White, S E (19.76). Is frost acti<strong>on</strong> really <strong>on</strong>ly<br />

hydrati<strong>on</strong> shattering<br />

Arctic and Alpine <strong>Research</strong>, 8, (11, 1-6.<br />

1035

SOME ASPECTS OF SOILS ENGINEERING PROPERTIES<br />

IMPROVEMENT DURING DAM CONSTRUCTION<br />

G.F. Bianovl, V.I. Makarovz and E.L. Kadkinaz<br />

lscientific <strong>Research</strong> Centre of the "Hydroproject" Institute, Moscow, USSR<br />

zThe <strong>Permafrost</strong>ology Institute, Yakutsk, USSR<br />

. '<br />

SYNOPSIS The paper focuses <strong>on</strong> upgrading soils engineering characteristics by basic parameters<br />

defining their strength, deformati<strong>on</strong> and seepage properties, with change or optimizati<strong>on</strong> of grainsize<br />

compositi<strong>on</strong> and moisture c<strong>on</strong>tent.<br />

For c<strong>on</strong>structi<strong>on</strong> of embankment dams impervious<br />

elements sandy loams are used with coarse<br />

fracti<strong>on</strong>s having a low seepage coefficient<br />

and relatively large internal fricti<strong>on</strong> angle.<br />

In practice the qualitative compacti<strong>on</strong> of<br />

soils with cparse fracti<strong>on</strong> (with over 50 per<br />

cent of 2 mm and larger fracti<strong>on</strong>s of the dry<br />

soil mass) presents some difficulties because<br />

of the formati<strong>on</strong> of rigid skelet<strong>on</strong> during compacti<strong>on</strong><br />

which impedes the fine soil filler<br />

compacti<strong>on</strong>.<br />

It is a comm<strong>on</strong> fact that with the equal amount<br />

of compacti<strong>on</strong> applied the soil is compacted<br />

most effectively <strong>on</strong>ly at the appropriate<br />

moisture c<strong>on</strong>tent called the optimum compacti<strong>on</strong><br />

moisture. In case the sail moisture is below<br />

optimum it is wetted before placement into<br />

the structure which is usually d<strong>on</strong>e without<br />

any difficulties. When the moisture c<strong>on</strong>tent<br />

exceeds the optimum value the soil is called<br />

overmoiat. The moisture c<strong>on</strong>tent reducti<strong>on</strong> of<br />

these soils is quite a problem.<br />

The easiest way is to dry the soil by natural<br />

means, in the open air, i.e. to aerate it. Unfortunately.this<br />

method of soils moisture reducti<strong>on</strong><br />

is <strong>on</strong>ly applicable in dry climate regi<strong>on</strong>s<br />

where the amount of summer precipitati<strong>on</strong>s<br />

is c<strong>on</strong>siderably lower than the evaporated<br />

moisture. In the regi<strong>on</strong>s with the amount of<br />

summer precipitati<strong>on</strong>s exceeding the evaporated<br />

moisture the aerati<strong>on</strong> does not give positive<br />

results, and it may even lead to the soil<br />

moisture c<strong>on</strong>tent increase,<br />

The process of soil drying in specially designed<br />

furnaces is not <strong>on</strong>ly energy and labour<br />

c<strong>on</strong>suming but low productive as well, Generally<br />

the moisture c<strong>on</strong>tent reducti<strong>on</strong> does not exceed<br />

2-3 per cent after drying in furnaces. A more<br />

intensive soil drying results in the sharp<br />

decrease of the furnace output and higher fuel<br />

c<strong>on</strong>sumpti<strong>on</strong>.<br />

In Japan a method was developed of the clay<br />

soil moisture reducti<strong>on</strong> by adding 20 per cent<br />

of crushed granite with 15 mm maximum grain<br />

size. After mixing the moisture of the initial<br />

soil was decreased by 40 per cenf due to water<br />

absorbti<strong>on</strong> by the granite fragments (Borovoi,<br />

1957). The drawback of this method is the<br />

impossibility of simultaneous regulati<strong>on</strong> of the<br />

soil moisture and grain-size compositi<strong>on</strong>. It<br />

is even more significant in cases of soil and<br />

soil mixtures with caarse fracti<strong>on</strong>s. The higher<br />

the cohesive soils moisture, the greater<br />

amount of coarse fracti<strong>on</strong>s is needed. But the<br />

greater the coarse-grained c<strong>on</strong>tent of the soil,<br />

the smaller amount of fragments may be added,<br />

For example, the preparati<strong>on</strong> of soil mixture<br />

with given grain-size compositi<strong>on</strong> inc1udir:g 3<br />

comp<strong>on</strong>ents, namely: the deluvial sandy loam<br />

with pebble, gravel and crushed st<strong>on</strong>e, glacial<br />

rubby sandy loam and sand gravel for c<strong>on</strong>structi<strong>on</strong><br />

of the Ust-Khantaisk dam cores provided<br />

the fine comp<strong>on</strong>ent moisture reducti<strong>on</strong> in the<br />

soil mixture <strong>on</strong>ly by 1.0-1.5 per cent (Kouperman,<br />

Myznikov, Plotnikov, 1977).<br />

The studied literature allows to c<strong>on</strong>clude that<br />

at present there is no sufficiently reliable<br />

procedure for soil reclamati<strong>on</strong> accepted worldwide,<br />

which could c<strong>on</strong>siderably change the major<br />

compactibility parameters, i.e. the moisture<br />

c<strong>on</strong>tent and grain-size compositi<strong>on</strong>.<br />

The Authors' investigati<strong>on</strong>s indicate that in<br />

general there is a soil reclamati<strong>on</strong> method<br />

allowing to change the soil properties so chat<br />

they achieve some previously prescribed parameters,<br />

this method may be called the soil<br />

improvement method. It includes the crushing<br />

of coarse fracti<strong>on</strong> present or added to the<br />

soil (Bianov, Makarov, Kadkina, 1982), After<br />

crushing, the coarse fracti<strong>on</strong> amount reduces,<br />

resulting in the fine grains increase. The<br />

crushed material absorbs moisture from the<br />

initial fine soil. After this treatment the<br />

soil heterogeneity and fine soil moisture<br />

decrease, resulting in higher soil compactibility.<br />

Let us look at the feasibility of this soil<br />

improvement method for dam impervious elements<br />

c<strong>on</strong>structi<strong>on</strong> in various climatic, engineering<br />

and geological c<strong>on</strong>diti<strong>on</strong>s.<br />

Example N 1. For the Kolym dam core c<strong>on</strong>structi<strong>on</strong><br />

the deluvial soliflucti<strong>on</strong> deposits were<br />

used which are natural sand soil mixture fillers<br />

with gruss crushed argillites, aleurolites<br />

1036

and shales fracti<strong>on</strong>s. The natural moisture of<br />

these soils ranges from 6 to 50 per cent with<br />

the coarse fracti<strong>on</strong> (P) amounting to 35-73 per<br />

cent by weight, the coarse fracti<strong>on</strong>s moisture<br />

being 4.9 per cent. The design criteria for<br />

dam materials require the soil moisture below<br />

15 per cent and P C 50 per cent, the dry fine<br />

soil density in compacted state f = 1.65<br />

g/cm3 for 90 per cent occurence.<br />

Suppose we are to use sandy loam with 20 per<br />

cent dry fine soil moisture (Wdfs) and P - 35<br />

per cent for dam core c<strong>on</strong>structi<strong>on</strong>. To reduce<br />

the soil moisture some crushed argillites,<br />

aleurolites and shales may be added which are<br />

provided from the quarry for dam shoulders material.<br />

The crushed st<strong>on</strong>e moisture i s below<br />

3 per cent. This mixture is an initial material<br />

for improvement and is to be crushed in<br />

a given mode. The improved soil is to c<strong>on</strong>form<br />

to the design moisture, the grain-size compositi<strong>on</strong><br />

and the compactibility requirements.<br />

The fine soil moisture to be obtained up<strong>on</strong><br />

improvement i s calculated by the formula<br />

.t Gfs (PES- Pdfs'pm . IOOX (1)<br />

wfs = pfs * Pdfs<br />

where Gfs 0.8 is the minimum fine soil saturati<strong>on</strong><br />

coefficient allowable for dam core<br />

material compacti<strong>on</strong>; Pfs - 2.75 g/cm3 is the<br />

fine comp<strong>on</strong>ent density (specific weight) of the<br />

soil; Pm = 1.0 g/cm3 is the moisture density<br />

of the soil.<br />

In compliance with equati<strong>on</strong> 1 for the improved<br />

soil material of the Kolym dam core the fine<br />

soil moisture is to be W:s - 19.3 per cent.<br />

Determinati<strong>on</strong> of the soil improvement parameters<br />

includes two aspects: estimati<strong>on</strong> of the<br />

required additi<strong>on</strong>s mass (relati<strong>on</strong>s of the initial<br />

comp<strong>on</strong>ents of the soil prior to crushing)<br />

and the choice of the crushing mode to attain<br />

the improved soil.<br />

The relati<strong>on</strong> between the initial comp<strong>on</strong>ents o f<br />

the soil mixture is calculated by:<br />

where X and Y are the amount of the soil comp<strong>on</strong>ents<br />

by weight (for example, sand and clay);<br />

Wx and W are these comp<strong>on</strong>ents moisture values<br />

Y<br />

in per cents.<br />

The c<strong>on</strong>diti<strong>on</strong> of the soil moisture calculati<strong>on</strong><br />

is that the soil moisture remains unchanged<br />

during crushing, i.e. the moisture of the soil<br />

mixture prior to crushing is equal to that of<br />

the improved soil material. During crushing<br />

the soil moisture c,<strong>on</strong>tent is redistributed<br />

due to absorbti<strong>on</strong> by the crushed products.<br />

x<br />

Wdfs c w*= 0.01 w* * *<br />

(100-P )+WCSP<br />

fa<br />

wher.e Wrs is the coarse fragments moisture of<br />

the improved soil in per cent equal to the<br />

coarse fragments saturati<strong>on</strong>.<br />

The experiments proved that argillites, aleurolites<br />

and shales fracti<strong>on</strong>s available at the<br />

Kolym hydropower plant c<strong>on</strong>structi<strong>on</strong> site increased<br />

their saturati<strong>on</strong> by 2-4 per cent*after<br />

crushing. For the given case we accept Wcs =<br />

= 7 per cent, P*- 50 per cent, then Wdf s=W*=<br />

- 13.2 per cent, and c<strong>on</strong>sequently X:Y = 1:0.8,<br />

which means that to attain the soil mixture<br />

with 13.2 per cent moisture c<strong>on</strong>tent it is necessary<br />

to mix sandy loam soil with 35 per cent<br />

moisture c<strong>on</strong>tent and P - 20 per cent and the<br />

crushed st<strong>on</strong>e with 3 per cent moisture c<strong>on</strong>tent<br />

in the proporti<strong>on</strong> 1:O.S. Thus the prepared<br />

mixture will c<strong>on</strong>tain 60 per cent coarse fracti<strong>on</strong>s<br />

which is derived by the formula<br />

where Pdfs is the cdarse fracti<strong>on</strong> amount of the<br />

soil mixture by weight, in per cents; Px and P Y<br />

are the coarse fracti<strong>on</strong>s amount in each comp<strong>on</strong>ent<br />

of the soil mixture by weight, in per cents.<br />

To obtain the improved soil properties with P*=<br />

= 50 per cent from the initial soil with Pfs=<br />

= 61 per cent the crusher mode is chosen so<br />

that 18 per cent of the coarse fracti<strong>on</strong> turn<br />

into fine-grained soil.<br />

The soil improvement procedure i5 as follows.<br />

The inirial soil (comp<strong>on</strong>ent X) from the quarry<br />

is c<strong>on</strong>veyed to the crusher al<strong>on</strong>g with the<br />

additives- in the form of crushed st<strong>on</strong>e (comp<strong>on</strong>ent<br />

Y). The crusher produces the improved soil<br />

with prescribed parameters: W* = 13.2 per cent,<br />

*<br />

Wfs - 19.3 per cent, P*- 50 per cent. Compacting<br />

this soil up to Gf8= 0.8 the dry fine comp<strong>on</strong>ent<br />

density is achieved equal to<br />

3 fdfs<br />

= 1.65 g/cm .<br />

Example N 2. For the Rogun dam core the soils<br />

including 53 per cent of coarse comp<strong>on</strong>ents with<br />

23 per cent fragmgnts above 80 mm, and up to<br />

37 per cent of fragments above 40 mm were used.<br />

The fine soil comp<strong>on</strong>ent moisture is 17 per cent,<br />

the fine particles density (specific weight) is<br />

3<br />

2.7 gfcm , The design envisages the following<br />

dam core material properties: the dry fine com-<br />

3<br />

p<strong>on</strong>ent density Pdfs= 2.1 gfcm , but not below<br />

3<br />

2.05 g/cm , the dry soil densityfds = 2.25<br />

g/cm3, but not below 2.15 g/cm3, and the soil<br />

moisture 11-12 per cent.<br />

Calculati<strong>on</strong> by the formula<br />

1037

shows that the soil with ps = 2.70 g/cm3 and<br />

11.5 per cent moisture c<strong>on</strong>tent can be compacted<br />

up to<br />

2.05 g/cm3 at maximum. Still<br />

p x: =<br />

the available soil i s to be compacted up to<br />

pdfs b 2.13 g/cm 3<br />

thus it is t o be improved,<br />

As with the example above we calculate the<br />

improved soil prope r ties: W* = 10.1 per cent,<br />

*- *<br />

,Wfs - 11.5 per cent, P = 0.25. The calculati<strong>on</strong>s<br />

also reveal that no additives are required<br />

for the soil improvement. The crushing of<br />

40 mm and above fracti<strong>on</strong> al<strong>on</strong>e will suffice.<br />

At present in the <strong>Permafrost</strong>ology Institute of<br />

the Siberian Branch of the USSR Academy of<br />

Sciences a testing soil improvement installati<strong>on</strong><br />

is exhibited using a double-drum crushtr,<br />

the installati<strong>on</strong> is based <strong>on</strong> the soil mixture<br />

preparati<strong>on</strong> procedure suggested by the Authors<br />

(Bianov, Makarov, Kadkina, 1982). It is equipped<br />

with devices preventing the wet clay soil<br />

from aticking to the drums. The soil improve-3<br />

ment installati<strong>on</strong> has the productivity of 1 m /h<br />

per <strong>on</strong>e linear centimeter of the drum length,<br />

3<br />

and the energy c<strong>on</strong>sumpti<strong>on</strong> is 1 kwt.h/m .<br />

The installati<strong>on</strong> operati<strong>on</strong> proves the versitality<br />

of this method c<strong>on</strong>cerning its applicability<br />

to practically all types of initial soils and<br />

materials, and the process of soil improvement<br />

by crushing, according to experiments, is sufficiently<br />

productive, cost-effective and low<br />

energy and labour c<strong>on</strong>suming. The experiments<br />

indicate that some mechanical energy envolved<br />

in crushing is transformed into thermal <strong>on</strong>e<br />

increasing noticeably the final soil mixture<br />

temperature. which is of particular importance<br />

for c<strong>on</strong>structi<strong>on</strong> in low temperature c<strong>on</strong>diti<strong>on</strong>s.<br />

It is also essential that the soil improvement<br />

allows to significantly diminish the dam profile<br />

due to high compactipn density of the soil<br />

mixtures, to reduce the dimensi<strong>on</strong>s of impervious<br />

elements and transiti<strong>on</strong> z<strong>on</strong>es of earthand<br />

rockfill dams comparing with overwetted soil<br />

mixtures.<br />

The above examples illustrate the efficiency of<br />

the given method of soil improvement. It is a<br />

sufficient argument for the unificati<strong>on</strong> of embankment<br />

dams impervious elements and development<br />

of a versatile improvement procedure for<br />

various initial soils for these elements.<br />

Recently the Central Asian Branch of the "Hydroproject"<br />

Institute has performed development<br />

projects of an experimental installati<strong>on</strong> for<br />

improvement of overwetted loams with coarse<br />

fragments for the Rogun dam core. The project<br />

needs further refinment. Still the problem lies<br />

with the choice of adequate crusher. The homemade<br />

crushers, for example, drum crushers, which<br />

are the most suitable for the material to be<br />

crushed, have limited inlet and outlet opening<br />

parameters.<br />

CONCLUSIONS<br />

An optimizati<strong>on</strong> procedure of grain-size compositi<strong>on</strong><br />

and moisture c<strong>on</strong>tent of overwetted clay<br />

soils with coarse fragments has been developed<br />

and experimentally verified. The crushing of<br />

coarse fracti<strong>on</strong>s of the soil mixture results<br />

in the rock material specific surface and absorbti<strong>on</strong><br />

increase, the grain-size compositi<strong>on</strong> improvement<br />

and lower moisture c<strong>on</strong>tent due to its redistributi<strong>on</strong><br />

am<strong>on</strong>g the soil mixture comp<strong>on</strong>ents.<br />

REFERENCES<br />

Bianov G.F,, Makarov V.I., Kadkina E.L. (1982).<br />

Sposob prigotovlenija gruntovykh srnesei,<br />

Authors' Certificate N 971991. Bulletin<br />

of Inventi<strong>on</strong>s, N 41.<br />

Borovoi A .A., editor. (1957), Proektirovanije<br />

i stroitelstvo bolshykh plotin. Review of<br />

the papers, presentid for the 7th and 8th<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> C<strong>on</strong>gresses <strong>on</strong> Large Dams,<br />

Energia, Moscow, p.63-64.<br />

Kouperman V.P., Myznikov Yu.N., Plotnikov V.M.<br />

(1977). Use-Khantaiskie plotiny. Energia,<br />

Moscow, 151 p.<br />

1038

FROST HEAVE FORCES ON H AND PIPE FOUNDATION PILES<br />

J.S. Buska and J.B. Johns<strong>on</strong><br />

U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering Laboratory, Hanover, N.H. 03755-1290 USA<br />

SYNOPSIS<br />

The magnitude and variati<strong>on</strong> of forces and shear str~sses, caused by<br />

frost heaving in Fairbanks silt and the adfreeze effecta of a surface ice layer and a<br />

gravel layer, were determined as a functi<strong>on</strong> of depth al<strong>on</strong>g the upper 2.75 m of a pipe pile<br />

and an H pile for three c<strong>on</strong>secutive winter seas<strong>on</strong>s (1982-1985). The peak frost heaving<br />

forces <strong>on</strong> the H pile during each winter were 752, 790 and 802 ]EN, Peak froat heaving<br />

forces <strong>on</strong> the pipe pile of 1218 and 1115 kN were determined <strong>on</strong>ly for the sec<strong>on</strong>d and third<br />

winter seas<strong>on</strong>s. Maximum average shear stresses acting <strong>on</strong> the H pile were 256, 348 and 308<br />

kPa during the three winter seas<strong>on</strong>s. Maximum average shear mtresses acting <strong>on</strong> the pipe<br />

pile were 627 and 972 kea for the sec<strong>on</strong>d and third winter seas<strong>on</strong>s. The surficial ice<br />

layer may have c<strong>on</strong>tributed 15 to 20% of the peak forces measured <strong>on</strong> the piles. The gravel<br />

layer <strong>on</strong> the H pile c<strong>on</strong>tributed about 35% of the peak forces meaeured.<br />

INTRODUCTION<br />

Foundati<strong>on</strong>s embedded in frost-susceptible<br />

soils can be subjected to large uplift forces<br />

resulting from frost heaving of the soils.<br />

These forces can cause an upward vertical displacement<br />

of foundati<strong>on</strong>s that are not embedded<br />

below the frost depth or do not have sufficient<br />

resistance to counteract heaving forces.<br />

In Alaska, H and pipe piles are often used to<br />

support buildings, bridges and dock Estructures.<br />

It is important that design engineers<br />

know the magnitude of frost heaving forces<br />

that can act <strong>on</strong> foundati<strong>on</strong> piles: and how these<br />

forces are,distributed al<strong>on</strong>g the piles. This<br />

informati<strong>on</strong> is used to determine the tensile<br />

strength requirements of a pile and the depth<br />

to which a pile needs to be embedded or how it<br />

must be loaded to resist heaving forces.<br />

This paper presents the results of a threeyear<br />

study (1982-85) designed to measure and<br />

record the magnitude and distributi<strong>on</strong> of axial<br />

strains, as a functi<strong>on</strong> of depth, time and temperature,<br />

for an H pile and a pipe pile panetrating<br />

surficial layers of ice and gravel and<br />

embedded in Fairbanks silt with an active<br />

layer overlying permafrost.<br />

METHODS AND MATERIALS<br />

soil c<strong>on</strong>diti<strong>on</strong>s<br />

The study was c<strong>on</strong>ducted at the Cold Regi<strong>on</strong>s<br />

<strong>Research</strong> and Engineering Laboratory's Alaska<br />

Field Stati<strong>on</strong>, Fairbanks, Alaska. The test<br />

site had bean cleared of vegetati<strong>on</strong> and c<strong>on</strong>sisted<br />

of deep colluvial deposits of slightly<br />

organic silts (Crory and Reed, 1965). Soil<br />

moisture c<strong>on</strong>tent was not measured in the fall<br />

preceding the 1982-83 measurement program:<br />

however, it was observed that the soil<br />

1039<br />

deposits were saturated below a depth of about<br />

0.5 m. Soil moisture prior to the 1983-84<br />

winter was found to have 405 water c<strong>on</strong>tent by<br />

weight near the surface and varied from 25% to<br />

29% between the surface and a.depth of about<br />

2.4 rn.<br />

The thickness of the seas<strong>on</strong>ally thawed or<br />

active layer between the piles at the<br />

beginning of the winter sea6<strong>on</strong> was 2.3 m in<br />

1982, 1.6 m in 1983 and 1.6 m in 1984. The<br />

soil in the active layer froze to the depth of<br />

the permafrost each winter during the study,<br />

as illustrated in Figure 1. Frost heaving at<br />

the site ranges from 2 to 7 cm during a<br />

typical winter.<br />

TWO comm<strong>on</strong>ly encountered situati<strong>on</strong>s for pile<br />

installati<strong>on</strong>s in Alaska are aufeis buildup<br />

around piles pear rivet crossings and the use<br />

of gravel backfill around the top of pilea.<br />

he experimental C<strong>on</strong>figurati<strong>on</strong> was designed to<br />

allow for surficial ice buildup and the uae of<br />

gravel backfill. Ice collars of 1.8-m<br />

diameter were installed to a thiekneas of 25<br />

cm during the 1982-83 seas<strong>on</strong> and 45 cm during<br />

the 1904-85 seas<strong>on</strong> around the upper secti<strong>on</strong>s<br />

of the piles in an effort to measure the adfreeze<br />

effects of surface ice depoaits (Fig.<br />

1). A 0.6-m-thick by 1.8-m tliameter gravel<br />

layor was used to replace the original backfill<br />

soil around the t~ppe of the piles in<br />

August 1983 and left in place through the<br />

1904-85 seas<strong>on</strong> (Fig. I).<br />

The top 3-m secti<strong>on</strong> of an H pile (HP10~57,<br />

25.4 cm web, 85 kg/lineal meter) and a pipe<br />

pile (30.5-cm I.D., 0.95-cm wall thickness)<br />

was instrumented with hermetically sealed<br />

weldable strain gauges and copper-c<strong>on</strong>stantan<br />

thermocouples. These were placed every 15.2<br />

cm al<strong>on</strong>g the centerline <strong>on</strong> both sides of the<br />

web of the H pile and <strong>on</strong> diametrically opposite<br />

sides of the pipe pile. Strain gauges

LVDT Support 0.a<br />

Pipe Pol0 Tharmol Siph<strong>on</strong><br />

Figure 2,<br />

Plan view of the experiment site.<br />

Figure 1. Development of frost penetrati<strong>on</strong> at<br />

the experimental site.<br />

oriented at 90' to the axial directi<strong>on</strong> were<br />

interspersed between the axially oriented<br />

gauges al<strong>on</strong>g the length of the instrumented<br />

secti<strong>on</strong>s. These we used to measure transverse<br />

strains in the piles ana to estimate the magnitude<br />

of horiz<strong>on</strong>tal compressive stresses in<br />

the soil acting <strong>on</strong> the piles .(Johns<strong>on</strong> and<br />

EsCh, 1985).<br />

Both the H and pipe piles were calibrated in<br />

compressi<strong>on</strong> prior to installati<strong>on</strong> and in tensi<strong>on</strong><br />

at the end of the experiment (Johns<strong>on</strong> ana<br />

Buska, in press). After the initial calibrati<strong>on</strong><br />

the piles were installed in holes augered<br />

to a depth of approximately 9 m. The holes<br />

around the piles were backfilled during the<br />

week of 31 October 1982 with a saturated sand<br />

slurry mixture for the lower 6 rn and with<br />

native silt at 40% water c<strong>on</strong>tent by weight for<br />

the upper 3 m. Thermal-siph<strong>on</strong> tubes with<br />

propane as the refrigerating fluid were<br />

installed in both piles to aid in freezing the<br />

lower 6 m of backfill slurry and cooling the<br />

permafrost, thereby increasing the frost jacking<br />

resistance of the piles.<br />

An air temperature sensor was mounted in a<br />

protective housing <strong>on</strong> the north side of the<br />

instrumentati<strong>on</strong> hut. soil temperatures were<br />

measured using thermistors spaced every 15.2<br />

cm to a depth of 2.75 m (Fig. 2).<br />

Soil surface heave measurementa were made<br />

using standard level surveying methods during<br />

the 1902-83 seas<strong>on</strong>. These measurements indicatea<br />

that the test piles did not change elevati<strong>on</strong><br />

during the 1982-83 seas<strong>on</strong>. Therefore,<br />

linear variable displacement transducers<br />

(LVDTs) mounted <strong>on</strong> a beam suspended between<br />

the piles were used to measure the ground<br />

surface heave during the 1983-84 and 1984-05<br />

seas<strong>on</strong>s (Fig. 2). The stability of the piles<br />

was rec<strong>on</strong>firmed by survey during the 1984-85<br />

seas<strong>on</strong>. *<br />

1040<br />

Force and Shear Stress Calculati<strong>on</strong>s<br />

The magnitudes of frost-heave-induced shear<br />

stresses al<strong>on</strong>g the -soil/pile interface were<br />

determined by using the strain measurements to<br />

first calculate the internal axial stresses in<br />

the piles and the internal axial forces in the<br />

pilea. The frost-heave-induced shear stresses<br />

al<strong>on</strong>g the soil/pile interface were then found<br />

by dividing the difference in force magnitude<br />

between two adjacent gauge6 by the corresp<strong>on</strong>ding<br />

pile surface area (Johns<strong>on</strong> and Esch,<br />

1985).<br />

Due to strain gauge malfuncti<strong>on</strong>s, the shear<br />

stress at the ice/pile interface over the<br />

thickness of the ice collar had to be estimated,<br />

by using the flow law for polycrystalline<br />

freshwater ice to obtain<br />

r = (:/A) l'n<br />

C<br />

where is the strain rate in the ice, A is a<br />

temperature-dependent c<strong>on</strong>stant, r is the<br />

shear ,stress over the thickness oE the ice<br />

collar and n is a c<strong>on</strong>stant determined from<br />

experiments (Paters<strong>on</strong>, 2981; Johns<strong>on</strong> and<br />

Buska, in press). The strain rate in the ice<br />

was calculated as the difference between the<br />

soil surface displacement rate near the pile<br />

and that at the soil/pile interface divided by<br />

the width over which soil displacement occurs<br />

(assumed to be 1 cm; Penner and Irwin, 1969).<br />

The uplift force <strong>on</strong> the piles at the ground<br />

surface due to the ice collar was calculated<br />

as a product of the ice/pile shear stress<br />

(r ), the pile surface area per lineal<br />

cekimeter and the ice collar thickness.<br />

The heaving force acting <strong>on</strong> the piles due to<br />

the gravel la er was calculated by subtracting<br />

the force actlng <strong>on</strong> the pile at a depth just<br />

below the bottom of the gravel layer from the<br />

force due to the ice layer (Johns<strong>on</strong> and Buska,<br />

in press).

EXPERIMENTAL RESULTS AND DISCUSSION<br />

There were five major low-tempeature periods<br />

during each seas<strong>on</strong> when the air temperature<br />

dropped below -25'12 for several days or more.<br />

Ground temperatures throughout the active<br />

layer above the permafrost were at or below<br />

O'C by early April for the first winter seas<strong>on</strong><br />

and by early January for the last two winter<br />

seas<strong>on</strong>s. The temperatures al<strong>on</strong>g the H and<br />

pipe piles were slightly lower than those in<br />

the adjacent undisturbed ground. Temperatures<br />

for'the pipe pile were generally lower than<br />

those for the H pile because of better c<strong>on</strong>tact<br />

with the thermal siph<strong>on</strong> at depth. Soil. and<br />

pile temperatures were lower during the sec<strong>on</strong>d<br />

and third winter seas<strong>on</strong>s because the site was<br />

cleared of snow.<br />

Figure 3 shows the soil surface heave for the<br />

1982-83, 1983-84 and 1984-85 seas<strong>on</strong>s. The<br />

ground surface displacements of between 2 and<br />

7 cm shown in Figure 3 may slightly underestimate<br />

the absolute or maximum accumulated<br />

displacements since the measurements were<br />

initiated just after the <strong>on</strong>set of soil freezing.<br />

The displacement measurements for 1983-<br />

84 indicate that the soil heave was greatest<br />

in the vicinity of the pipe pile.<br />

The temperature, shear stress and frost heave<br />

force distributi<strong>on</strong>s for the H pile are shown<br />

in Figure 4 for selected dates during the<br />

1984-85 seas<strong>on</strong>. The shaded area shows the<br />

shear stress distributi<strong>on</strong> <strong>on</strong> the H pile. The<br />

ice/pile shear stress and the uplift force due<br />

to the ice collar are shown above the ground<br />

surface or zero depth value. Soil/pile shear<br />

stresses due to frost heaving are not uniform<br />

al<strong>on</strong>g the length of a pile: generally they act<br />

from the ground surface ta the depth of the<br />

maximum force <strong>on</strong> the pile, and the restraining<br />

shear stresses act from the depth of the maximum,force<br />

<strong>on</strong> the pile downward until the uplift<br />

force is balanced. Uplift soil/pile<br />

shear stresses are present in the permafrost<br />

throughout the winter seas<strong>on</strong>.<br />

Table 1 summarizes the results and Figures 5-7<br />

show the air temperature, ground temperature<br />

and pile frost heave force as functi<strong>on</strong>s of ,<br />

depth and time for the 1982-83, 1983-84 and<br />

1984-85 sea6<strong>on</strong>s.<br />

6 , 1 1 1 1 1 1 7 1 1 , 1 1 1 1 iIII'1 I I I I I I 1 ' 1 1 1 1<br />

0<br />

- 5001 Surroce<br />

-<br />

E 4t<br />

I<br />

I<br />

0<br />

-I<br />

-<br />

E<br />

-2<br />

I<br />

1 M<br />

-r-<br />

Top af Grovel Loyer<br />

0<br />

-I<br />

0-<br />

I<br />

l,l,l,l,l,l,l~l,l~l,llllt~,<br />

IO 20 IO 20 IO 20 lox) IO 20<br />

SOD Oct NOV Oec J<strong>on</strong><br />

-3 0<br />

PileTemperolure ("C)<br />

Local Sheor Stress (Wa! and Force IkN)<br />

Figure 3. Soil surface heave for the 1982-83, Figure 4. Pile temperature, shear siresa ais-<br />

1983-84, and 1984-85 ssao<strong>on</strong>s. LVDT displace- tributi<strong>on</strong> (shaded area), and force as a funcments<br />

for points 1, 2, 3, and 4 indicate soil, tioh of depth for the I4 pile during the. 1984-<br />

surface displacements taken at the locati<strong>on</strong>s 85 seas<strong>on</strong>. (a) 15 October 1984; (b) 15 March<br />

indicated. 1985: (c) 15 April 1985; (d) 15 May 1985.<br />

.lo41

__-<br />

Table 1.<br />

Summary of Maximum Forces and Average Shear Stresses <strong>on</strong> the H and Pipe Piles.<br />

""""" H pile _--f____-<br />

pipe pile*---<br />

1982-83 1983-84 1984-85 1983-84 1984-85<br />

Date peak frost heaving force occurred 24 Jan 17 Feb 26 Feb 17 Dec 15 Dec<br />

1983 1984 1985 1983 1984<br />

Depth below ground surface where peak 2.29 2.21 2.16 1.75 0.94<br />

force occurred (m)<br />

Peak frost heaving force (kN) 752 790 802 1118 1115<br />

Thickness of active layer between the 2.3 1.6 2.6 1.6 1.6<br />

, piles at beginning of seas<strong>on</strong> (m)<br />

Thickness of ice layer (m) 0.25 "- 0.45 -" 0.45<br />

Heaving force due to ice layer (lcN)** 151 -" 118 "I<br />

Ioe/pile shear stress due to ice layer 5aa "- 255 "- 401<br />

(kPa) **<br />

Max. average soil/pile shear stress 256 348 308 "-<br />

using Itboxed-in" ( ) surface area of<br />

H pile (kPa)***<br />

Max. average soil/pile shear stress 157 2 14 190 627 972<br />

using actual surface area of piles<br />

(kPa) ***<br />

Maximum internal stress in pile (MPa) 40.5, 51.0 51.7 218.7 118.4<br />

Heaving force due to gravel layer (kN)** --- 280 292 "- -"<br />

* The pipe pile results need to be verified by further research (see text).<br />

** The force and shear stresses for the ice and gravel Layers had to be calculated<br />

indirectly (see text) and may be too high for the ice layer and c<strong>on</strong>sequently too low<br />

for the gravel layer.<br />

*** Computed using the pile surface areas from<br />

frost-heaving force <strong>on</strong> the pile.<br />

185<br />

the soil surface to the depth of the peak<br />

"-<br />

The peak forces <strong>on</strong> the H pile were essentially<br />

the same, varying by <strong>on</strong>ly 29 W from the average<br />

peak force for all three winter seas<strong>on</strong>s.<br />

During the study, the pipe pile suffered c<strong>on</strong>siderable<br />

strain gauge malfuncti<strong>on</strong>. The results<br />

from the few remaining good gauges are<br />

presented in Table 1. The magnitudes of forces<br />

and shear stresses <strong>on</strong> the pipe pile appear<br />

too high in comparis<strong>on</strong> with the H pile results<br />

and values reported by others. The pipe pile<br />

results need to be verified by further research.<br />

The ice collars may have c<strong>on</strong>tributed<br />

15 to 20% of the peak forces measured <strong>on</strong> the<br />

piles. The forces and stresses resulting from<br />

the ice and gravel layers could not be determined<br />

directly due to strain gauge malfuncti<strong>on</strong>s.<br />

The forces and stresses were calculated<br />

indirectly and may be too high for the<br />

ice layer and c<strong>on</strong>sequently too low for the<br />

gravel layer.<br />

The forces for both piles generally increased<br />

after a decrease in air temperature and decreased<br />

after an increase in air temperature.<br />

Changes in the forces acting <strong>on</strong> the piles<br />

usually Lagged behind corresp<strong>on</strong>ding air temperatures<br />

from 1 to 8 days, with the l<strong>on</strong>ger<br />

lag times occurring later in the winter<br />

seas<strong>on</strong>. In the spring, uplift forces are<br />

relieved from the surface down as the ground<br />

warms.<br />

The majority of experiments to measure frost<br />

heaving forces acting <strong>on</strong> piles have been c<strong>on</strong>ducted<br />

<strong>on</strong> piles embedded in n<strong>on</strong>-permafrost<br />

soil. In analyzing the results of those experiments<br />

it has been implicitly assumed that<br />

<strong>on</strong>ce the soil temperature is lower than 0°C<br />

(i.e. when the soil is frozen) the soil heave<br />

and frost-heaving forces are negligible. The<br />

results of our experiments and those of Crory<br />

and Reed (1965) indicate that soil heave and<br />

frost heave forces c<strong>on</strong>tinue to be generated<br />

throughout the winter even in frozen ground<br />

(Figs. 3-7). These effects may possibly be<br />

explained by the existence and migrati<strong>on</strong> of<br />

unfrozen water within the frozen soil. When<br />

frozen soil c<strong>on</strong>taining both ice and unfrozen<br />

water Sa subjected to a temperature gradient,<br />

this cauaes water to move toward the colder

i<br />

Figure 5. Comparis<strong>on</strong> of air temperature,<br />

ground temperature, and H pile frost heave<br />

force as a functi<strong>on</strong> of depth and time for the<br />

1982-83 seas<strong>on</strong>.<br />

Figure 6. Comparis<strong>on</strong> of air temperature, ground.<br />

temperature, H pile frost heave force, and pipe<br />

pile frost heave force as a functi<strong>on</strong> of depth<br />

and time €or the 1983-84 seas<strong>on</strong>.<br />

soil, enhancing ice lens formati<strong>on</strong> and soil<br />

heaving (Oliphant et al., 1983). The unfrozen<br />

water c<strong>on</strong>tent-temperature relati<strong>on</strong>ship may<br />

also explain why the heave forces acting <strong>on</strong><br />

piles embedded in permafrost resp<strong>on</strong>d so rapidly<br />

to temperature changes. On cooling, an<br />

increase in ice lens growth will c<strong>on</strong>tribute to<br />

increased heave forces. On warming, the percentage<br />

of unfrozen water will increase exp<strong>on</strong>entiall<br />

as a functi<strong>on</strong> of temperature,<br />

resulting In a decrease in heave forces.<br />

The depth of maximum heave force might be expected<br />

to coincide with the depth where the<br />

most rapid freezing is occurring (Johns<strong>on</strong> and<br />

Buska, in press). For n<strong>on</strong>-permafrost soils<br />

the depth of most rapid freezing is near the<br />

O'C isotherm. The relati<strong>on</strong>ship between temperature<br />

and unfrozen water c<strong>on</strong>tent for frozen<br />

soils mrist be known to estimate the depths of<br />

maximum freezing rate over time. The depth of<br />

maximum freezing rate is then used when cal-<br />

culating the depth of acti<strong>on</strong> for frost heaving<br />

stresses over time.<br />

CONCLUSIONS<br />

Calculated forces, as determined from the instrumented<br />

piles, indicate that the magnitude<br />

of frost-heaving uplift forces acting <strong>on</strong> a<br />

pile increases from the soil surface to a<br />

maximum value at depth, and then decreases due<br />

to the restraining acti<strong>on</strong> of the soil or<br />

permafrost <strong>on</strong> the pile.<br />

The average depths of the maximum frost heave<br />

forces were 2.2 m <strong>on</strong> the N pile and 1.4 m <strong>on</strong><br />

the pipe pile. The peak frost-heave forces<br />

were 802 kN for the H pile and 1118 kN for the<br />

pipe pile during the three winters of the<br />

study. The maximum Internal tensile stresses<br />

were 51.7 MPa for the H pile and 118.4 MFa for<br />

the pipe pile. The maximum calculated heave<br />

1043

kPa for the pipe pile. Ice/pile shear stresses<br />

due to the ice collars at the tops of the<br />

piles were 588 and 255 kPa for the H pile and<br />

401 kPa for the pipe pile.<br />

Maximum heaving forces and shear stresses<br />

occurred during periods of maximum cold and<br />

soil surface heave magnitude. These forces<br />

were not related to the depth of froat for<br />

most of the winter, since the soil adjacent to<br />

the piles was frozen to the permafrost table,<br />

and may be explained by the existence of unfrozen<br />

water in the soil. The forces for both<br />

piles generally increased after a decrease in<br />

air temperature and decreased after an increase<br />

in air temperature. Changes in forces<br />

acting <strong>on</strong> the piles usually Lagged behind<br />

corresp<strong>on</strong>ding air temperature changes by<br />

several days. Soil surface displacements of 2<br />

to 7 cm were measured at the experiment site.<br />

The important mechanisms that determine the<br />

magnitude of uplift heave forces are (1) soil<br />

heaving as the driving force, and (2) soil<br />

temperature, which c<strong>on</strong>trols the unfrozen water<br />

c<strong>on</strong>tent, mechanical properties o€ the, soil and<br />

the area of influence of heaving pressures.<br />

ACKNOWLEDGMENTS<br />

Funding for this study was provided by the<br />

Alaska Department of Transportati<strong>on</strong> and Public<br />

Facilities and by the Federal Highway Administrati<strong>on</strong>.<br />

The authors gratefully acknowledge the efforts<br />

of C. Rohwer, C. Olmstead, S. Perkins, B.<br />

Young, R. Briggs, D. Solie, D. Dinwoodie, M.<br />

Sturm, W. Zito, L. Koaycki and D. Haynes. The<br />

authors also thank Dave Esch for his c<strong>on</strong>tributi<strong>on</strong>s<br />

to the completi<strong>on</strong> of the project.<br />

Figure 7. Comparis<strong>on</strong> of air temperature, ground<br />

temperature, H pile frost heave force, and pipe<br />

pile frost heave force as a functi<strong>on</strong> of depth<br />

and time for the 1984-85 seas<strong>on</strong>.<br />

force that may have been c<strong>on</strong>tributed by the<br />

ice layers at the top of the piles was 151 IEN<br />

for the H pile and 185 kN for the pipe pile.<br />

The maximum calculated heave force c<strong>on</strong>tributed<br />

by the gravel layer around the top of the H<br />

pile was about 292 kN.<br />

REFERENCES<br />

Crory, F E & Reed, R E (1965).<br />

Measurement of frost heaving forces <strong>on</strong><br />

piles. U.S.A. Cold Regi<strong>on</strong>s <strong>Research</strong> and<br />

Engineering Laboratory (USACRREL) Technical<br />

Report 145.<br />

Johns<strong>on</strong>, J B & Esch, D C (1985).<br />

Frostjacking forces <strong>on</strong> H and pipe piles embedded<br />

in Fairbanks silt. Proc 4th Inter<br />

Sym Ground Freezing, Sapporo, (2), 125-133.<br />

Johns<strong>on</strong>, J B & Buska, J S (in press).<br />

Measurement of frost heave forces <strong>on</strong> H and<br />

uiue viles. USACRREL Renort.<br />

Olipiiant, J L, Tice, A R &*Nakano, Y (1983).<br />

Water migrati<strong>on</strong> due to a temperature gradi-<br />

The maximum average soil/pile shear stress<br />

computed <strong>on</strong> the basis of the "boxed in" ( @ )<br />

ent in frozen soil. P~QC 4th Inter C<strong>on</strong>f<br />

surface area of the H pile from the soil sur- <strong>Permafrost</strong>, Fairbanks. 951-956.<br />

face to the depth of peak frost heave force Paters<strong>on</strong>, w S B (1981).'<br />

was 348 kPa for the H pile. The maxidlum aver- The physics of glaciers. 20-41. Pergam<strong>on</strong>,<br />

age soil/pile shear stress computed using the New Yoxk.<br />

actual surface areas of the piles from the<br />

Penner, E h Irwin, W W (1969).<br />

soil surface to the depth of the peak frost<br />

Adfreezing of Leda Clay to anchored footing<br />

heave force was 214 kPa for the H pile and 972 columns. Can. Geotsch. J., (6), 3, 327-337.<br />

1 044

A NEW FREEZING TEST FOR DETERMINING FROST SUSCEPTIBILITY<br />

E.J. Chamberlain<br />

U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering Laboratory<br />

SYNOPSIS A new freezing test for determining the frost susceptibility of soils used in<br />

pavement systems is designed to supplant the standard CRREL freezing test. This new test cuts<br />

the time required to determine frost susceptibility in half. It also allows for the deteminati<strong>on</strong><br />

of both the frost heave and thaw weakening susceptibilities and c<strong>on</strong>siders the effects of<br />

freeze-thaw cycling. The new freezing test also eliminates much of the variability in test results<br />

by completely automating the temperature c<strong>on</strong>trol and the data observati<strong>on</strong>s.<br />

INTRODUCTION<br />

Laboratory freezing tests are necessary to<br />

accurately characterize the frost susceptibility<br />

of soils. This is especially true for<br />

borderline granular materials used for the<br />

base and subbase layers in roads and runways.<br />

The U.S. Army Corps of Engineers has employed<br />

a freezing test (Chamberlain and Carbee, 1981)<br />

for more than 30 years. While this test has<br />

proven adequate for-identifying and classifying<br />

frost-susceptible soils, it suffers from<br />

several serious defects. Most significant of<br />

these are poor temperature c<strong>on</strong>trol,. indeterminate<br />

side fricti<strong>on</strong>, lengthy test period,<br />

lack of thaw weakening index, and provisi<strong>on</strong><br />

for <strong>on</strong>ly <strong>on</strong>e freeze. Furthermore, the standard<br />

CRREL freezing test is c<strong>on</strong>servative and<br />

appears to reject many n<strong>on</strong>-frost-susceptible<br />

materials as frost-susceptible.<br />

This report discusses the current Corps of<br />

Engineers practice for C<strong>on</strong>ducting freezing<br />

tests <strong>on</strong> soils, presents a new freezing test<br />

designed to replace it, describes test equipment<br />

and procedures, and suggests a method for<br />

classifying the frost susceptibility of soils<br />

based <strong>on</strong> both frost heave and thaw weakening.<br />

CURRENT FREEZING TEST<br />

The freezing teat employed by the corps of<br />

Engineers, often referred to as the CRaEL<br />

standard freezing test, was developed to<br />

evaluate the relative frost susceptibility of<br />

soils and granular base and subbase materials<br />

used in pavement systems. In the standard<br />

test, materials are subjected to a very severe<br />

combinati<strong>on</strong> of freezing and moisture c<strong>on</strong>diti<strong>on</strong>s<br />

that are highly c<strong>on</strong>ducive to frost heaving.<br />

The test does not predict the actual<br />

magnitude of frost heave under field c<strong>on</strong>diti<strong>on</strong>s,<br />

but is designed to provide a relative<br />

indicati<strong>on</strong> of the potential for frost heave.<br />

Soil samples are generally compacted and<br />

frozen from the top down at a c<strong>on</strong>stant rate of<br />

13 mm/day for 12 days. The samples are frozen<br />

in tapered, acrylic Plexiglas cylinders that<br />

are Tefl<strong>on</strong>-lined and lightly coated with silic<strong>on</strong>e<br />

grease to reduce side fricti<strong>on</strong>. A porous<br />

st<strong>on</strong>e at the base and a c<strong>on</strong>stant-head water<br />

supply provide a source of water 10 mm above<br />

the sample bottom. A surcharga of 3.5 kPa 18<br />

placed <strong>on</strong> the sample to simu1ate.a 150 mm<br />

thickness of asphalt c<strong>on</strong>crete- pavement. The<br />

samples are frozen in groups of four in a<br />

freezing cabinet. The lower boundary temperature<br />

is maintained at +4'C throughout the<br />

test, while the upper boundary ais temperature<br />

is lowered <strong>on</strong>ce a day in steps to facilitate<br />

the average frost penetrati<strong>on</strong> rate of 13<br />

ram/day.<br />

The temperatures in the soil samples are<br />

measured by thermocouples placed through the<br />

cell walls and are automatically recordea by a<br />

data acquisiti<strong>on</strong> system. Frost heave is observed<br />

with displacement transducers and is<br />

c<strong>on</strong>tinuously recorded, al<strong>on</strong>g with the thermocouple<br />

outputs, <strong>on</strong> the data acquisiti<strong>on</strong> system.<br />

Frost depths are determined by plotting<br />

the temperature profiles and interpolating the<br />

positi<strong>on</strong> of the O'C isotherm. The maximum<br />

frost heave rate occurring during the test<br />

period is used as an index of the frost susceptibility.<br />

The standard test has several limitati<strong>on</strong>s.<br />

The test requires too much time (12 days) and<br />

is encumbered by manual temperature adjustmenta.<br />

Side fricti<strong>on</strong> is not eliminated, particularly<br />

with coarser-grained materials. The<br />

teat does not c<strong>on</strong>sider the effects of freezethaw<br />

cycling. The test is principally an index<br />

test for frost heave and does not directly<br />

address thaw weakening, which is frequently<br />

more of a problem in roads than frost heave.<br />

Furthermore, the standard test appears to be<br />

c<strong>on</strong>servative, and there im no evidence of<br />

direct correlati<strong>on</strong> with field observati<strong>on</strong>s.<br />

1045

DEVELOPMENT OF A NEW FREEZING TEST<br />

A new freezing test was proposed (Chamberlain,<br />

1981) to alleviate the problems with the standard<br />

test. As a result, the following criteria<br />

were established: 1) precise c<strong>on</strong>trol of<br />

boundary temperatures is necessary; 2) radial<br />

heat flow must be minimized: 3) side fricti<strong>on</strong><br />

must be eliminated: 4) free access to water<br />

must be available: 5) freeze-thaw cycling must<br />

be specified; 6) the test must be completed in<br />

<strong>on</strong>e week: and 7) the test must provide for<br />

both frost heave and thaw weakening susceptibility<br />

indexes.<br />

The literature was thoroughly reviewed<br />

(Chamberlain, 1981) for state-of-the-art prac-<br />

*ices for determining the frost susceptibility<br />

of soils with freezing tests. A multi-ring<br />

freezing cell (MRFc) c<strong>on</strong>figurati<strong>on</strong> was selected<br />

to minimize side fricti<strong>on</strong> during freezing<br />

while still accommodating the other important<br />

factors. The EIRFC is not a new development in<br />

frost-susceptibility testing; it was used l<strong>on</strong>g<br />

ago by Taber (1929) and ~uckli (1950).<br />

Because of the lack of a moisture seal between<br />

the rings and because of soil. extrusi<strong>on</strong> between<br />

rings during thawing, a rubber membrane<br />

was selected to line the inside of the cell.<br />

I also round that precise upper and lower<br />

boundary temperature c<strong>on</strong>trol could be best<br />

obtained by circulating a n<strong>on</strong>-freezing liquid<br />

from refrigerated baths through plates in intimate<br />

c<strong>on</strong>tact with the top and bottom of the<br />

test sample. Although a c<strong>on</strong>stant rate of heat<br />

extracti<strong>on</strong> was c<strong>on</strong>sidered desirable, it was<br />

c<strong>on</strong>cluded that a c<strong>on</strong>stant cold-plate temperature<br />

during freezing was a more practical objective<br />

and that the heat extracti<strong>on</strong> rates<br />

should approximate the rates that occur in<br />

seas<strong>on</strong>al frost regi<strong>on</strong>s. A heat flow rate in<br />

the range of 50-100 n/mP was selected €or the<br />

critical period during which the frost heave<br />

susceptibility index would be determined. A<br />

temperature gradient of approximately 0.04*C/<br />

IMI was chosen as a compromise between what has<br />

been observed in the field and what is technically<br />

practical.<br />

I decided that at least two freeze-thaw cycles<br />

were required to allow for the effects of<br />

changes in soil structure, density, permeability,<br />

etc. caused by freezing and thawing.<br />

Each freeze-thaw cycle would take 40 hours and<br />

each leg of the cycle would be 24 hours in<br />

durati<strong>on</strong>. With an allowance for a final 24<br />

hours for c<strong>on</strong>ducting the thaw weakening test,<br />

the freezing and thawing could be accomplished<br />

in <strong>on</strong>e working week.<br />

As a result the upper boundary temperature was<br />

selected to be -3-C and the lower boundary<br />

temperature +3'C for the first 8 hours of<br />

freezing. To assure complete freeze c<strong>on</strong>diti<strong>on</strong>ing<br />

of the test sample, the top and bottom<br />

temperatures are set to -12-C and O'C, respectively,<br />

during.the final 16 hours of each<br />

freezing leg. Complete freezing is necessary<br />

to thoroughly c<strong>on</strong>diti<strong>on</strong> the test material with<br />

frost acti<strong>on</strong> before freezing it a sec<strong>on</strong>d time.<br />

This is necessary because the frost heave<br />

rates of materials c<strong>on</strong>taining clay fines may<br />

be increased significantly by freeze-thaw cycling.<br />

The frost heave observati<strong>on</strong>s critical<br />

1046<br />

to determining the frost heave susceptibility<br />

are made at the end of the first 8 hours of<br />

freezing. During the first 16 hours of thawin,<br />

the temperature of the upper boundary is<br />

ralsed to +12"C and the bottom temperature is<br />

increased to +3'C. Both the upper and lower<br />

boundary temperatures are set to +3'C during<br />

the last 8 hours of thawing to c<strong>on</strong>diti<strong>on</strong> the<br />

sample at a uniform temperature before the<br />

next freeze. The same c<strong>on</strong>diti<strong>on</strong>ing temperatures<br />

are applied before the first freeze to<br />

ensure that the initial temperature c<strong>on</strong>diti<strong>on</strong>s<br />

are the same for both freeze-thaw cycles. The<br />

entire boundary temperature program is illus-<br />

"<br />

trated in Fig.i. -<br />

"-<br />

Plata<br />

Bottom<br />

Cold Plate<br />

L<br />

-15 ~ditiwl~Freete+Thow".fcFreete~Thow-<br />

0 24 48 72 96<br />

Time (hr)<br />

Figure 1. Boundary temperatures for new freezing<br />

test.<br />

I decided that a c<strong>on</strong>stant head of water should<br />

be supplied to the base of the sample through<br />

a porous st<strong>on</strong>e. The water table should be<br />

maintained about 10 mm above the sample base<br />

during freezing to provide a severe c<strong>on</strong>diti<strong>on</strong><br />

of water availability. The samples can be<br />

soaked before freezing by raising the water<br />

table in increments to the top. Theoretically<br />

the water table could a180 be lowered to approximately<br />

1 m below the sample base if a 1-<br />

bar air entry value saturated porous st<strong>on</strong>e<br />

were placed between the sample and the base<br />

plate. The practical maximum distance between<br />

the sample bottom and the water table, however,<br />

is 0.75 m because of problems in sustaining<br />

the c<strong>on</strong>tinuity of water in the porous<br />

st<strong>on</strong>e, in the space beneath it, and in the<br />

c<strong>on</strong>necting lines. The water supply can also<br />

be shut off to simulate closed-system freezing.<br />

A surcharge of 3.5 kPa was selected as a standard<br />

for this freezing test as is used for the<br />

standard test. No surcharge would be a more

severe c<strong>on</strong>diti<strong>on</strong>, but not <strong>on</strong>e applicable to<br />

pavement systems.<br />

To facilitate the determinati<strong>on</strong> of the fmst<br />

depth and the boundary temperatures, thermocouples<br />

are placed at intervals al<strong>on</strong>g the side<br />

of the test sample. More precise thermistor<br />

or RTD sensors were not c<strong>on</strong>sidered because of<br />

their higher cost and greater fragility. The<br />

thermocouples are sealed to the wall with<br />

silic<strong>on</strong>e rubber to prevent water leakage.<br />

Figure 3. Freezing cabinet assembly for new<br />

freezing test.<br />

i<br />

Linear Moti<strong>on</strong><br />

Transducer<br />

Circulating Bath<br />

Dial gages and displacement transducers are<br />

arranged <strong>on</strong> top of each sample to provide<br />

records of frost heave and thaw c<strong>on</strong>solidati<strong>on</strong>.<br />

The outputs of the displacement transducers<br />

and the thermocouples are recorded with a<br />

computer-c<strong>on</strong>trolled data acquisiti<strong>on</strong> system. ,<br />

The same computer is used to c<strong>on</strong>trol the plate<br />

temperatures. The entire data acquisiti<strong>on</strong><br />

c<strong>on</strong>trol system is illustrated schematically in<br />

Fig. 4. The data are automatically processed<br />

and recorded <strong>on</strong> a magnetic tape or floppy disk<br />

and displayed <strong>on</strong> a printer. Up<strong>on</strong> completi<strong>on</strong><br />

of the freeze-thaw cycling, the critical frost<br />

heave rates are determined automatically and<br />

printed for a permanent record.<br />

The frost heave rates at 8 hours into each<br />

freezing leg are c<strong>on</strong>sidered the critical heave<br />

DATA ACW181TIONICONTROL SCWEMATIC<br />

Calculator<br />

Thermal<br />

prlnter<br />

Orla acquislti<strong>on</strong><br />

Figure 2. Schematic of new freezing test apparatus<br />

The MRFC test apparatus is illustrated in Fig.<br />

2. The inside diameter of the MRFC is 146 nun<br />

and the height 154 mm. Six 25.4-mm-high<br />

Plexiglas rings, lined with a rubber membrane,<br />

make up the cell. Water is made freely available<br />

through a porous base st<strong>on</strong>e from a<br />

Mariotte c<strong>on</strong>stant-head water supply. Heat<br />

exchange plates (cold and warm) are located<br />

directly <strong>on</strong> top of the sample and beneath the<br />

water supply base. A soluti<strong>on</strong> of ethylene<br />

glycol and water is circulated through the<br />

cold plates from refrigerated baths to maintain<br />

the desired test temperatures. The bath<br />

temperatures are c<strong>on</strong>trolled with a computer<br />

that is programmed with the boundary temperatures<br />

shown in Fig, 1. Four samples are<br />

frozen together to facilitate replicati<strong>on</strong>s and<br />

productivity. The tests are c<strong>on</strong>ducted in a<br />

cold room with an ambient temperature just<br />

above freezing to limit radial heat flow and<br />

to thus ensure a planar freezing z<strong>on</strong>e. Standal<strong>on</strong>e<br />

setups have also been prepared as shown<br />

in Fig.3.<br />

Thsrmocouplo#<br />

I<br />

I<br />

Figure 4 . Schematic of the temperature c<strong>on</strong>trol<br />

and data acquisiti<strong>on</strong>.system.<br />

I1<br />

I<br />

"I<br />

1 047

ates, and they are used to determine the<br />

frost-heave susceptibilities of the test<br />

materials. The frost-heave susceptibility<br />

determined from the first freeze should be<br />

used for c<strong>on</strong>diti<strong>on</strong>s where freezing is c<strong>on</strong>tinuous<br />

throughout the winter, whereas the frost<br />

susceptibility from the sec<strong>on</strong>d freeze should<br />

be used when more than <strong>on</strong>e complete cycle of<br />

freezing and thawing occura. The thaw-weakening<br />

susceptibility is determined after the<br />

sec<strong>on</strong>d freeze-thaw cycle with a GBR (California<br />

hearing.ratio) test. Preliminary frostsusceptibility<br />

criteria based <strong>on</strong> all three of<br />

the critical factors are shown in Table I.<br />

;,n L Grover y -1.65 q1cm3<br />

k--l A<br />

C I " h<br />

Table I.<br />

Preliminary frost-susceptibility<br />

criteria<br />

Thaw<br />

Frost-susceptibility Heave rate Cm<br />

classificati<strong>on</strong> (&day) (%I<br />

Negligible (1 >20<br />

Very la 1-2 20-15<br />

LmJ 2-4 15-10<br />

Medim<br />

4-8 10-5<br />

High<br />

8-16 5-2<br />

Very high >16 c2<br />

VALIDATION OF THE NEW FREEZING TEST<br />

Preliminary tests were made to ensure that the<br />

MRFC method of c<strong>on</strong>finement minimized the side<br />

fricti<strong>on</strong> problem. The rubber-lined multi-ring<br />

c<strong>on</strong>figurati<strong>on</strong> was first compared with the<br />

CRREL Tefl<strong>on</strong>-coated tapered cylinder and wraps<br />

made of telescoping plastic film and waxed<br />

paper. Fig. 5 shows the results of freezing<br />

tests <strong>on</strong> a frost-susceptible sand with the<br />

four methods of c<strong>on</strong>finement. The MRFC and the<br />

plastic film and waxed paper c<strong>on</strong>fined samples<br />

heaved similarly, while the frost heave in the<br />

CRREL tapered cylinder was c<strong>on</strong>siderably less.<br />

Another test series that included a sample<br />

with no c<strong>on</strong>finement c<strong>on</strong>firmed that the MRFC<br />

method of c<strong>on</strong>finement caused little restraint<br />

to frost heave.<br />

I I I 1 I I I<br />

0 20 40 60<br />

Time (hf)<br />

Figure 5. Results of freezing tests with four<br />

experimental methods of c<strong>on</strong>finement.<br />

Other studies were made to ensure that the<br />

frost fr<strong>on</strong>t was planar and the heat flow was<br />

<strong>on</strong>e dimensi<strong>on</strong>al. Split vertical secti<strong>on</strong>e of a<br />

frozen clay specimen showed nearly linear ice<br />

and soil layer features characteristic of <strong>on</strong>edimensi<strong>on</strong>al<br />

heat flow, whereas radial heat<br />

flow was observed to be no more than 5 W/m2.<br />

The radial heat flow measurements also showed<br />

that the net vertical heat flow was in the<br />

range of 50-100 W/mp at the end of the first 8<br />

hours of both freezing legs.<br />

The new freezing test was validated with<br />

materials and data from field test secti<strong>on</strong>s.<br />

Six soils from Winchend<strong>on</strong>, Massachusetts, and<br />

three from Albany, New York, were selected for<br />

this evaluati<strong>on</strong>. These tests are discussed in<br />

detail elsewhere (Chamberlain, 1986). The<br />

unified Soil Classificati<strong>on</strong>s and other soil<br />

index properties for each of the test materials<br />

are given in Table 11. Examples of test<br />

results for two of the test materials are<br />

shown in Fig. 6 and 7. Figure 7 illustrates<br />

the importance of the two freeze-thaw cycles,<br />

The critical frost heave rate €or the sec<strong>on</strong>d<br />

freeze is five times the rate obsewed during<br />

BO<br />

Table 11. Test material index properties.<br />

Percent Percent Liquid Plasticity Soil<br />

finer than finer than Uniformity Limit Index classi-<br />

Material U.074 nm 0.002 mn Coefficient (%I (%I Gravity ticati<strong>on</strong>"<br />

Winchend<strong>on</strong><br />

Dense-graded st<strong>on</strong>e 9 6 46.2 NP 2.82<br />

Graves sand 4816 20.8 NP 2.70 SM<br />

Hart Brothers sand 31 8 9.1 NP 2.76 SM<br />

Hyannis sand 31 3 3.8 M! 2.67 34<br />

Ikalanian sand 48 a 5.2 -<br />

NP 2.70 S"SP<br />

sibley till 38 24 22.5 19 4 2.74 S"SC<br />

-<br />

Albany<br />

Taxiway €3 base 15 10 95.8<br />

Taxiway B subbase 13 8 16.3<br />

Taxiway H subgrade 16 6 2.6<br />

NP 2.72 WSM<br />

Np 2.68 W-Gt4<br />

- W 2.69 SM<br />

* ti - yravel, S - sand, rfi - silt, P - poorly graded, C - clay, W - well graded.<br />

1048

I .5 I I I<br />

0 Albany<br />

Winchend<strong>on</strong><br />

(Iu Freeze)<br />

0 20 40 60 80<br />

Time (hr)<br />

"""<br />

Figure 6. Example of frost heave results with new<br />

freezing test: Hyannis sand.<br />

100<br />

m c<br />

* o<br />

Base<br />

1 l.5r-i<br />

' 251 I I I I I<br />

1<br />

20 40<br />

Tlme (hr)<br />

Laboratory Heave Rate (rnrnlday)<br />

Figure 7. Example of frost heave results with new<br />

freezing test; Sibley till.<br />

Figure 8. Comparis<strong>on</strong> of average field frost heave<br />

rates with laboratory heave rates.<br />

the first freeze. Three additi<strong>on</strong>al tests <strong>on</strong><br />

the same soil yielded similar results. This<br />

soil, Sibley till, had 24% finer than 0.002 nun<br />

and a plasticity index of 4.<br />

The average frost heave rates for each of the<br />

test materials are plotted against the average<br />

frost heave rates observed for a two-year<br />

period in the field in Fig. 8. There is a<br />

str<strong>on</strong>g correlati<strong>on</strong> between the laboratory and<br />

field observati<strong>on</strong>s of heave fate, especially<br />

for the first freeze. The correlati<strong>on</strong> is not<br />

<strong>on</strong> a line of equality, as the laboratory heave<br />

rates exceed the field values by a factor of<br />

10. However, it is the intent of this study<br />

to use the freezing test qualitatively as an<br />

index test, not a quantitative predictor of<br />

frost heave in the field. When the heave rate<br />

results are plotted for the sec<strong>on</strong>d freeze<br />

(Fig. 7 ), the correlati<strong>on</strong> between the laboratory<br />

and field results is weaker, as the<br />

points for two Albany sites and <strong>on</strong>e Winchend<strong>on</strong><br />

site fall far to the right of the curve fitting<br />

the remainder of the data.<br />

The CBR after thawing is correlated with results<br />

of pavement loading tests in Fig. 9. It<br />

can be seen that there is a str<strong>on</strong>g correlati<strong>on</strong><br />

between the laboratory CBR after thawing and<br />

the maximum resilient pavement deflecti<strong>on</strong>s for<br />

a simulated wheel load of 280 kPa that occurred<br />

during the thaw period in the field.<br />

DISCUSSION<br />

The importance of c<strong>on</strong>ducting a freezing test<br />

with indicators of both frost heave and thaw<br />

weakening susceptibility has been dem<strong>on</strong>strated<br />

with this series of tests. Comparis<strong>on</strong>s of<br />

c<br />

Sibley<br />

Ikalanlan Sand<br />

Hart Hort Brothers<br />

'\&graded<br />

Winchend<strong>on</strong><br />

o Albany<br />

P 260 kPo<br />

T/W<br />

Hy<strong>on</strong>nis<br />

B Subbase<br />

S<strong>on</strong>d<br />

St<strong>on</strong>e<br />

P<br />

Laboratory CBR after Thawing (%)<br />

Figure 9. Comparis<strong>on</strong> of maximum pavement<br />

deflecti<strong>on</strong>s €or 280-kPa simulated wheel<br />

loading in the field with the<br />

laboratory CBR after thawing.<br />

1049

Table 111. Summary of frost-susceptibility ratings made<br />

with new freezing test.<br />

Range oE<br />

New freezing test field observati<strong>on</strong>s<br />

8-hr heave rate Thaw Heave Pavement<br />

Material 1st treeze 2nd freeze CBR rate deflecti<strong>on</strong><br />

Winchend<strong>on</strong><br />

Denseqraded<br />

st<strong>on</strong>e M M M VL-M M<br />

Graves sand n M VH G H , H-VH<br />

Hart Brothers sand M M H VL-bI H<br />

Hyannis sand VL VL M N-L El<br />

Ikalanian sand M M n VI" H-VH<br />

Sibley till VL VH VH N-VL H-VH<br />

- Alba=<br />

Taxiway A base M H L N N<br />

Taxiway R subbase M H M L H<br />

Taxiway R subgrade H H VI, L H<br />

N - negliyible, VL - very lw, L - lm, M - mdium, H - high, VH - very hiyh<br />

frost-susceptibility ratings for each of the<br />

test materials (Table 111) show that the<br />

frost-susceptibility classificati<strong>on</strong>s based <strong>on</strong><br />

thaw weakening are either greater than or<br />

equal to the ratings based <strong>on</strong> frost heave, and<br />

for the Sibley till material, the thaw-weakening<br />

characteristics would definitely c<strong>on</strong>trol<br />

its selecti<strong>on</strong> as a road c<strong>on</strong>structi<strong>on</strong> material.<br />

The importance of c<strong>on</strong>ducting two freeze-thaw<br />

cycles is not as clearly dem<strong>on</strong>strated with<br />

these tests apart from the observati<strong>on</strong> that<br />

freeze-thaw cycling can have a dramatic effect<br />

<strong>on</strong> frost heave rate in the laboratory. The<br />

increases in heave rates observed in the<br />

laboratory were probably due to changes in<br />

permeability caused by freezing. Chamberlain<br />

and Gow (1979) showed that freezing can cause<br />

Large increases in the permeability of soils<br />

c<strong>on</strong>taining clay fines. The resp<strong>on</strong>se was ai€ferent<br />

in the field because the freezing and<br />

thawing did not reach the water table. Thus,<br />

an unc<strong>on</strong>diti<strong>on</strong>ed layer of material remained<br />

between the water table and the freezing z<strong>on</strong>e.<br />

Because all of the field validati<strong>on</strong> work was<br />

d<strong>on</strong>e at sites where the water table was very<br />

near to the maximum depth of frost penetrati<strong>on</strong>,<br />

the frost-susceptibility classificati<strong>on</strong>s<br />

given in Table If1 are for a severe water<br />

availability c<strong>on</strong>diti<strong>on</strong>. For other c<strong>on</strong>diti<strong>on</strong>s<br />

where the water table is deep or there is a<br />

coarse drainage layer that interrupts the flow<br />

of water into the test material, a closed-syst<br />

tem freezing test may be more appropriate.<br />

The test results presented here are for <strong>on</strong>ly a<br />

limited number of materials and test c<strong>on</strong>diti<strong>on</strong>s.<br />

For this test to be implemented as a<br />

tool for design or compliance, additi<strong>on</strong>al<br />

tests must be c<strong>on</strong>ducted for a wider variety of<br />

soil and envir<strong>on</strong>mental c<strong>on</strong>diti<strong>on</strong>s.<br />

CONCLUSIONS<br />

The determinati<strong>on</strong> of the frost susceptibility<br />

of soil materials used in pavement systems is<br />

more adequate with a freezing test if indicators<br />

of both frost heave susceptibility and<br />

thaw weakening susceptibility are included in<br />

the test matrix. The effects of freeze-thaw<br />

cycling can be evaluated by including at least<br />

two cycles of freezing and thawing.<br />

The new freezing test described here accomplishes<br />

these tasks in a more efficient and<br />

precise manner than the currently used standard<br />

CRREL freezing test.<br />

Additi<strong>on</strong>al validati<strong>on</strong> of the new freezing test<br />

is required before reliable froqt-susceptibility<br />

criteria based <strong>on</strong> its use can be established<br />

and before the test can replace the<br />

standard freezing test used by the Corps of<br />

Engineers.<br />

REFERENCES-<br />

Chamberlain, E J (1981).<br />

Frost susceptibility of soil, Review of index<br />

tests. U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong><br />

and Engineering Laboratory, CRREL Cold<br />

Regi<strong>on</strong>s Science and Engineering M<strong>on</strong>ograph<br />

81-2. , 121 p.<br />

Chamberlain, E J (1986).<br />

Evaluati<strong>on</strong> of selected frost-susceptibility<br />

test methods. U.S. Army Cold Regi<strong>on</strong>s<br />

<strong>Research</strong> and Engineering Laboratory, CRREL<br />

Report 86-14, 56 p.<br />

Chamberlain, E J & Carbee, D L (1981).<br />

The CRREL frost heave test.<br />

Frost I Jord, (22), 55-63.<br />

Chamberlain, E J & GWW, A J (1979).<br />

Effect of freezing and thawing <strong>on</strong> the<br />

peremability and structure of soil.<br />

Engr. Geology, (13), 73-92.<br />

RUCkli, R (1950).<br />

Pavement design and frost susceptibility of<br />

road foundati<strong>on</strong>s. (In German),<br />

Strasse und Verkehr, (36), 125-134.<br />

Taber, S (1929).<br />

Frost heaving.<br />

Jour. of Geology, (27), 428461.<br />

1050

THAW SETTLEMENT OF FROZEN SUBSOILS IN SEASONAL FROST REGIONS<br />

SYNOPSIS The laboratory thaw c<strong>on</strong>solidati<strong>on</strong> tests with undisturbed samples and the in-situ<br />

observati<strong>on</strong>s <strong>on</strong> thaw settlements of testing buildings and in-operati<strong>on</strong> buildings were carried out.<br />

for investigating the thaw settlement of frozen ground, It is found that the settlement of frozen<br />

soils starts with the soil temperature increasing and the relati<strong>on</strong> between the settlement amount and<br />

elapsed time of thawing is practically linear. The c<strong>on</strong>solidati<strong>on</strong> settlement tends to be stable in<br />

ten days after the soil was completely thawed. The thawing c<strong>on</strong>solidati<strong>on</strong> settlement amount is directly<br />

proporti<strong>on</strong>al to the applied load, A comm<strong>on</strong>ly used formula for predicting the thawing and<br />

c<strong>on</strong>solidati<strong>on</strong> settlement was checked by testing 967 samples taken from 11 sites.<br />

INTRODUCTION<br />

In seas<strong>on</strong>al frost regi<strong>on</strong>s, if the soil is frost<br />

susceptible, the thaw settlement of foundati<strong>on</strong><br />

will take place during thaw. With a certain<br />

level of load <strong>on</strong> thawing frozen soil, the settlements<br />

are caused by thaw as well as compressi<strong>on</strong>.<br />

Combinati<strong>on</strong> of these two kinds of set,-<br />

tlements will make the building based <strong>on</strong> the<br />

soil to settle in different extents. As the<br />

settlement is greater than the allowable deformati<strong>on</strong><br />

of a building, the building will be destroyed.<br />

In order to investigate thaw-settlement<br />

behaviour of frozen soils and predict the thaw<br />

settlement of actual engineering, the following<br />

work i.e., laboratory thaw-c<strong>on</strong>solidati<strong>on</strong> tests<br />

with undisturbed frozen soil samples, field<br />

observati<strong>on</strong>s <strong>on</strong> thaw settlement of natural<br />

ground with or without external loads, and observati<strong>on</strong>s<br />

<strong>on</strong> thaw settlement of frozen subsoils<br />

beneath actual buildings were performed during<br />

1981-1985.<br />

THE COMMONLY-USED FORMULA FOR CALCULATING THAW-<br />

CONSOLIDATION SETTLEMENT<br />

As menti<strong>on</strong>ed above, if there are Loads <strong>on</strong> frozen<br />

subsoils, the c<strong>on</strong>solidati<strong>on</strong> settlement will take<br />

place in company with thaw settlement during<br />

thaw. This total value of the settlements of<br />

frozen soils may be calculated with the following<br />

formula (Tsytovich, 1962).<br />

S = AoH + aPH (1)<br />

where A, is the coefficient of thaw settlement;<br />

a is the coefficient of c<strong>on</strong>solidati<strong>on</strong>;<br />

H is the thickness of thawing frozen-soil;<br />

P is the total compressi<strong>on</strong> stress <strong>on</strong> the<br />

subsoils c<strong>on</strong>cerned,<br />

If the values of A,, a and P vary with the depth,<br />

in calculating the total Settlement frnzen sub-<br />

soil, it is necessary to divide the'frozen soil<br />

c<strong>on</strong>cerned into several layers. The settlement<br />

in i-th layer may be estimated by<br />

Then, the total thaw and c<strong>on</strong>solidati<strong>on</strong> settlement<br />

is given by<br />

If external pressure is equal to zero, eq.(3)<br />

becomes:<br />

Eq.(4) i s <strong>on</strong>ly used to calculate soi'l thaw settlement<br />

in the self-weight.<br />

DETERMINATION OF PARAMETERS A,,<br />

a AND P<br />

The key to use eq.(3) and (4) is tO determine<br />

the values of A, and a at c<strong>on</strong>structi<strong>on</strong> site.<br />

Investigati<strong>on</strong> shows that the parameters A, and L\<br />

are closely related to the water'c<strong>on</strong>tent, dry<br />

uni,t weight and structure of frozen soils.<br />

In order to get the values of A, and a for foundati<strong>on</strong><br />

design in Daqing regi<strong>on</strong>, a series of thawcunsolidati<strong>on</strong><br />

tests were c<strong>on</strong>ducted <strong>on</strong> 967 undisturbed<br />

samples. By analyzing the test data,<br />

the parameters A, and a can be evaluated with<br />

water c<strong>on</strong>tent (W) and dry unit weight ( yd) in<br />

terms of the following equati<strong>on</strong>s (T<strong>on</strong>g et al.,<br />

1985).<br />

In the case o f compressi<strong>on</strong> after thawed:<br />

1051

A: = 0.00445W - 0.07015 (5)<br />

or A~=47.724-62.504yd+lO.842 EXP (Yd) (6)<br />

In the case of compressi<strong>on</strong> while thawing:<br />

A; = 0.00586W -0.1027 (7)<br />

or 4~=40.088-37.404yd+4.2288 EXP (Yd) (8)<br />

Under a load of 200 kPa<br />

a-0.0025~-0.0179-1.93~10-24E~~ (w) (9)<br />

a-O.2202-0.1203Yd+0.0012 EXP (Yd) (10)<br />

Value of Hi in the formulas menti<strong>on</strong>ed above<br />

depends up<strong>on</strong> the thickness total of frozen soil<br />

and the evenness of A and a in the frozen soil<br />

laver c<strong>on</strong>cerned underneath the foundati<strong>on</strong>s. If<br />

distributi<strong>on</strong> of A, and a in all of frozen soil<br />

layers is even, then the frozen soil can be<br />

treated as <strong>on</strong>e layer, other-wise, the frozen<br />

soil should Be divided into several layers,<br />

The value of P for each subsoil 1ayer.i~ determined<br />

by:<br />

tlements of thawing and c<strong>on</strong>solidati<strong>on</strong> of frozen<br />

soils under different loads at the test sites<br />

and compared the observed values. The comparis<strong>on</strong><br />

.shows that at some test sites, the calculated<br />

values are c<strong>on</strong>cordant with observed values, as<br />

shown in Table 11.<br />

The reas<strong>on</strong>s why the observed and calculated settlements<br />

are in a good agreement may be;<br />

(i) The soil at the test site are of waak or<br />

medium frost susceptibility and are distributed<br />

homogeneously.<br />

(ii)<br />

The applied pressure <strong>on</strong> the test foundati<strong>on</strong><br />

is not greater than the compressive<br />

strength of the thawed soils, therefore,<br />

plastic sliding of the soil beneath<br />

the foundati<strong>on</strong> may not take place.<br />

However, €or other test sites, the calculated<br />

values are discordant with observed values, as<br />

shown in Table 111.<br />

Note that the compressive strength of thawed<br />

soils listed in Table I1 and III are evaluated<br />

according to the Standard of Subsoil and Foundati<strong>on</strong><br />

Design for Industrial and Civil Architecture<br />

(GTJ7-74).<br />

From the data in Table 111, observed settlements<br />

are greater than calculated <strong>on</strong>es, this may be<br />

explained as following:<br />

where PI and P2 are the applied stresses at<br />

upper-and lower-surface of each layer,ql and 92<br />

are self-weight pressure <strong>on</strong> the upper-and lowersurface<br />

of each layer, respectively.<br />

APPLICATION CONDITION AND VERIFICATION OF EQUA-<br />

TIONS (3) AND (4)<br />

To test the reliability of eqs (3) and (4), 40<br />

model test foundati<strong>on</strong>s-were placed in Fangxiao,<br />

Oilfield C<strong>on</strong>structi<strong>on</strong> Design and <strong>Research</strong><br />

Institute of Daqing Petrolem Administerative<br />

BuEeau.;and.. Children's palace test sites with<br />

different buried depthes, and their thaw settlements<br />

were observed. In additi<strong>on</strong>, laboratory<br />

thaw -settlement tests <strong>on</strong> the undisturbed samples<br />

from the observati<strong>on</strong> sites were also carried out.<br />

Verificati<strong>on</strong> of Ea.(4)<br />

The test results from the laboratory thawing<br />

tests <strong>on</strong> the undisturbed samples from the three<br />

test sites were used to calculate thaw settlement<br />

with eq.(4). Then, the calculated thaw settlements<br />

were compared with the observed values,<br />

as shown in Table I.<br />

The soil in the test site is a saturated loam,<br />

str<strong>on</strong>g frost susceptible soil. So, its angle of<br />

internal fricti<strong>on</strong> after thawing will be gregtly<br />

decreased (Tsytovich, 1962).<br />

Because of moisture migrati<strong>on</strong> during freezing,<br />

many ice lenaes were formed in the frozen soils.<br />

After thawing, the water c<strong>on</strong>tent of the subsoil<br />

is very high, about 56.2% in maximum, and the<br />

subsoil becomes in plastic-flow state. Therefore,<br />

the compressi<strong>on</strong> and shear strength of subsoil<br />

are very low. As a result, under the<br />

acti<strong>on</strong> of load, the subsoil beneath foundati<strong>on</strong><br />

will be squeezed out plasticly and the settle-<br />

ment will be much greater. In this case, the<br />

field testing c<strong>on</strong>diti<strong>on</strong> did not accord with the<br />

c<strong>on</strong>diti<strong>on</strong> of lateral restraint, under which eq.<br />

(3) was drived. That eq.(3) is inapplicable to<br />

this case.<br />

By analysing the results observed at the test<br />

site, the c<strong>on</strong>diti<strong>on</strong>s for the applicati<strong>on</strong> of eq.<br />

(4) are: (1) The value of A, should be obtained<br />

from the tests <strong>on</strong> the undisturbed samples taken<br />

from the place where settlement needs to be pre-<br />

dicted and in the time when frost depth is<br />

deepest: and (2) the water c<strong>on</strong>tent of frozen soil<br />

i6 less than 50%.<br />

The applicati<strong>on</strong> of eq.(3) requires more c<strong>on</strong>diti<strong>on</strong>s.<br />

Thev are: (1) .. The structure of frozen<br />

soil must be massive or laminal; ( 2) Values of<br />

From Table I, it is seen that the calculated and A, and a should be less than 0,07 and 0.06 kpa<br />

observed values are very close. Thus, formula<br />

(4) can be used to predict thaw settlement in respectively, and (3) the addlti<strong>on</strong>al stress in<br />

engineering practice with a enough accuracity. subsoil caused by applied load must be less than<br />

the compressive strength of the soil after thaw-<br />

Verificati<strong>on</strong> of Eq.(3) ing .<br />

With formula (3)'we calculated the total set-<br />

1052

TABLE I<br />

Comparis<strong>on</strong> Between the Calculated Thaw Settlements with E q.(4) and Observed Values<br />

Test site<br />

Frost Thickness of Values Total sett. Total sett. Error<br />

depth each layer f A0 calculated observed so-sc<br />

(cm) (cm) S, (cm) So Icm)<br />

so<br />

"<br />

45 0.134 6.03<br />

30 0.079 2.37<br />

Fangxiao 200 35 0.048 1.68<br />

test site 40<br />

50<br />

0.017<br />

0.009<br />

0.68<br />

0.45<br />

=11.21 11.8 5%<br />

Institute<br />

test site 195<br />

40 0.111 .""<br />

4 -44<br />

30<br />

0 108 3.24<br />

40<br />

o .oa76 3.504<br />

40<br />

0.0673 2.692<br />

45<br />

0.0733 3.665<br />

=17.54 17.9 2%<br />

Children<br />

palace 165<br />

test site<br />

45<br />

30<br />

30<br />

30<br />

30<br />

0.178 8.01<br />

0.142 4.26<br />

0.114 3.42<br />

0,081 2.43<br />

0.073 2.19<br />

=20.31 22 7.7%<br />

Comparis<strong>on</strong> aetween Calculated and Observed Thaw Settlement at a Test Sit%<br />

Buried depth of<br />

test foundati<strong>on</strong><br />

(m) 0.5 0.5 1.1 1.1 1.1 1.1<br />

Compressive strength (kpa)<br />

of the thawed soils 98 98 130 130 130 130<br />

C<strong>on</strong>tact pressur.e <strong>on</strong> (Kpa) 49 98 49 98 147 196<br />

the base of foundati<strong>on</strong><br />

Total settlement<br />

calculated<br />

Total settlement<br />

observed<br />

(cm) 14.7 17.6 7.8 8.4 11.2 12.8<br />

(cm) 14.7 16.6 8.3 8.2 11.4 12.9<br />

VERIFICATION THROUGH ACT.U.AL BUILDINGS<br />

In Daqing regi<strong>on</strong>, in order to built apartments<br />

as well as-to make them into use in the same<br />

year, the foundati<strong>on</strong> engineering, including<br />

excavati<strong>on</strong> work of frozen soil, should be usually<br />

started in March, when the active layer is<br />

still frozen, So it is necessary to determine<br />

the frost susceptibility subsoils at the site<br />

according to the data of engineering geological<br />

investigati<strong>on</strong> and then to estimate the allowable<br />

thickness of residual frozen soil based <strong>on</strong> the<br />

check of total thaw settlement of the subsoil<br />

with values of A, and a observed.<br />

The observati<strong>on</strong>s <strong>on</strong> total thaw sqttlement of<br />

three five-storey apartments that were build <strong>on</strong><br />

different typies of frost heave soil were made<br />

in order to check eq.(3) through actual buildings,<br />

The calculated and observed results are<br />

shown in Table IV.<br />

From Table IV, it is seen that the calculated<br />

values of chaw settlement is greater slightly<br />

than that observed, It is feasible to apply eq.<br />

(3) engineering practice from the point of safety<br />

view. The difference between the calculated and<br />

observed values may be caused by that the observati<strong>on</strong><br />

was started after c<strong>on</strong>structi<strong>on</strong> of foun-<br />

1053

TABLE 111<br />

Comparis<strong>on</strong> Between Calculated and Observed Thaw Settlement at a Test Site<br />

Buried depth of<br />

test foundati<strong>on</strong><br />

(m) 0.5 0.8 0.8 0.8 1.6 1.4 1.4<br />

Compressive strength (kpa) (50<br />

of the thawed soils<br />

60 60 60 65 65 65<br />

C<strong>on</strong>tact pressure <strong>on</strong> 1 (kPa 50 50 100 150 50 LOO 200<br />

the base of foundati<strong>on</strong><br />

Total settlement<br />

calculated<br />

Total settlement<br />

observed<br />

(cm) 14.2 9.6 11.9 14.4 2.9 3.8 4.5<br />

(cm) 20.0 16.7 19.3 19.5 10.7 14.3 15.3<br />

TABLE I V<br />

Comparis<strong>on</strong> Between Calculated and Observed Settlements of Three Actual Buildings<br />

Items<br />

Building & Place<br />

Thickness of residual<br />

No.2 Building No,l-2 Building No.3-5 Buildin<br />

Fangxiao In Feanshou inn<br />

in Lixinn-<br />

Quarter Quarter cui Quarter -<br />

frozen soil H (cm) 46 31 27<br />

i<br />

Designed<br />

(kPa) load<br />

100 100 100<br />

Water c<strong>on</strong>tent in ( X ) frozen 21.4 soil<br />

23.1 20.1<br />

Coefficient o f thaw settlement, A, 0.023 0.033 0.015 1<br />

Amount of thaw-settlement S=AnH (cm) 1.058 1.023 0.405<br />

Coefficient of thaw<br />

compressi<strong>on</strong>, a 0.032 0.036 0 .om<br />

Settlement of thaw compressi<strong>on</strong> S=aHP (cm) 1.472 1.116 0.756<br />

Total calculated S=S+S settlement (cm) 2.53 2.14 1.16<br />

Observed total So (cm) settlement<br />

2.34 2.03 1.07<br />

Error, e<br />

8.1 5.4 8.1<br />

Sn<br />

dati<strong>on</strong> before this, some thaw and c<strong>on</strong>solidati<strong>on</strong><br />

settlement had taken place.<br />

CONCLUSIONS<br />

(i)<br />

Through laboratory test with great number<br />

of undisturbed samples of frozen soil and<br />

statistical analysis, the quantitative<br />

relati<strong>on</strong>ship between parameters A, and a ,<br />

and hater c<strong>on</strong>tent as well as dry unit weight were<br />

ebtelned. And alkeithe adaptability of values-of<br />

A 0 and a had been dettr,minsd through ii$d<br />

m and outdoor test of thaw c<strong>on</strong>solidati<strong>on</strong>.<br />

r!EFERENCES<br />

soil layer, it is verified that the<br />

method discussed in this paper can be<br />

used to predict the thaw settlement of<br />

seas<strong>on</strong>ally frozen soils with a good accuracity,<br />

But, it can not be used to<br />

predict the thaw settlement of the<br />

frozen soils with higher frost susceptibility,<br />

which compressive strength<br />

after thawing is less than applied load.<br />

(ii) By observing the thaw settlements of T<strong>on</strong>g Chagnjiang & Chen Enyuan, (1985). Thawthree<br />

five-storey apartments and lots of<br />

c<strong>on</strong>solidati<strong>on</strong> behaviour of seas<strong>on</strong>ally<br />

model foundati<strong>on</strong>s <strong>on</strong> residual frozen<br />

frozen soils. Proceedings of 4th Interna-<br />

1054

ti<strong>on</strong>al Symposium <strong>on</strong> Ground Freezing, Sapporo,<br />

Japan, p.159-163.<br />

Tsytovich, N.A., (1962). Base and Foundati<strong>on</strong>s <strong>on</strong><br />

Frozen Ground, (Chinese translati.<strong>on</strong>).<br />

Chinese Industrial Publishing House, p.29-<br />

13 *<br />

Standard of Subsoil and Foundati<strong>on</strong> Design for<br />

Industrial and Civil Architecture(GTJ7-74).<br />

Chinese Architecture Publishing House,<br />

1974.<br />

1055

TENSILE ADFREEZING STRENGTH BETWEEN SOIL AND FOUNDATION<br />

Ding,Jingkang, Lou, Anjin and Yang, Xueqin<br />

Northwest Institute, China Academy of Railway Sciences<br />

SYNOPSIS The tensile adfreening strength tests between soil and foundati<strong>on</strong> are introduced<br />

and the results are analysed in %hie paper. It is pointed that the tensile adfxeeeing atrength is<br />

2e;$ or so greater than the shear adfreezing atrength. The behavioure of the tensile adfreezin<br />

strength are also analysed in the paper, and the test values of the tenaile adfreezing strength<br />

taken-from laboratory are given.<br />

ITlTROIXlCTION<br />

The adfreezing strength between frozen soil and<br />

foundati<strong>on</strong> is the main souxce of the bearing capacity<br />

of pile and anchor-rod in frozen ground<br />

and -the main element to effect the stability of<br />

the foundati<strong>on</strong>. It is ala0 a great requisite<br />

parameter for calculating the stability of resisting<br />

iroet heave of foundati<strong>on</strong> and of resiating<br />

fall ana slide of the retaining wall. But<br />

in the paat, the adfreezing strength haa been<br />

defined as the ehear strength between frozen<br />

soil and foundati<strong>on</strong>, and from this, a test method<br />

has been presented (Cheitovich, 1973) to<br />

determine the adfreezing strength by pulling or<br />

pushing a pole out of the frozen ground. When<br />

designing an engineering, people often assume<br />

1 Faatening Base 2 Sample<br />

that the tensile adfreezing strength is equal to 3 Dial Indicator 4 Safe Cover<br />

the shear adfreezing strength, use and the later 5 Moving Block 6 Stable Block<br />

for calculating founda-t;i<strong>on</strong> for all frozen the 7 Wsight<br />

interfaces. Is it proper And if it suits the 8 Box of C<strong>on</strong>stant Temperature<br />

practice There is no evidence by now. In<br />

order to solve the above problem and study the Fig.1 Equipment for Tensile Adfreezing<br />

behaviour of tensile adfreezing strength, a test<br />

Strength Teat<br />

is made in laboratory for determining the tensile<br />

ana shear adfreezing strength between frozen<br />

soil ana c<strong>on</strong>crete and steel foundati<strong>on</strong>s.<br />

Then we can start the tensile test.<br />

A c<strong>on</strong>stant loading speed is wed for the test.<br />

The load increment is 98.07 N per hour, i,e.<br />

EXPERIICEFENTATION<br />

The loading ve1ocir;y is 1.47 N/cm2.hx. During<br />

the tesr;, keep the sample in c<strong>on</strong>stant Tempera-<br />

The tensile test of adfreezing strength between Twe and measure tne temperature and deformafrozen<br />

soil and c<strong>on</strong>crete made is by the equip- ti<strong>on</strong> of %ne interface.<br />

ment in Figure 1. The sample is a barrel. Two A rec.r;angul.ar sample 103: shear tesL is wed.<br />

pieces of steel pipe of 80 mm in diameter and The ahear box is divided into TWO parts, <strong>on</strong>e ror<br />

200 mm in length are adopted for making sample, pouring c<strong>on</strong>crete in, anotner ror Tilling test<br />

<strong>on</strong>e for pouring c<strong>on</strong>crete in, another for filling soil in. Arter getting the sample ready, we<br />

the teat soil in. When making a\sample, we put install a thermocouple in tne interrace, and<br />

the two pipes together ana fill the soil into then tbe process OX ireezing sample and the meit,<br />

then insert a thermocouple in the interface. tnod OX shear test are %he same as the tensile<br />

After this, move the sample into cool room for test.<br />

freezing until it is to be frozen, then put it The teat for determining the tensile and shear<br />

into the test inatrument and keep it a c<strong>on</strong>a- in adireezing atrengtn between frozen soil and<br />

tant temperature circumstance for 24 hours. steel foundaZi<strong>on</strong> is made by tne equipment in<br />

* Jiang Jiazheng and Zhao Cuifeng take part in the test.<br />

1056

Figure 2.<br />

The freezing areas of steel sample<br />

for tenaile and shear test are the same. After<br />

burying the steel eample and thermocouples into<br />

the soil in model trough, we make the temperature<br />

of the room decreasing to freeze the model<br />

trough. As tne model trough is completely fro-<br />

Zen, it is covered with soft Soam plastic for<br />

24 hours, BO that the soil temperature could be<br />

more uniform. Tnen we can start the teat.<br />

A fast c<strong>on</strong>tinuoue load by jack is taken Tor the<br />

test and <strong>on</strong>e teat must be finiehed in <strong>on</strong>e to<br />

two minutes. The soil temperature, stress <strong>on</strong><br />

the shear interface and tna displacement of the<br />

ateel ample axe meamred during the test.<br />

I<br />

U<br />

1 Shelf for Loading 2 Dynamometer<br />

3 Jack<br />

4 Dial Indicator<br />

5 Sample for Tensi<strong>on</strong><br />

6 Sample for Shear<br />

Fig.2<br />

Equipment for Tensile and Shear<br />

Test<br />

RESULTS ANIl ANALYSIS<br />

Table 1 and I1 show the tensile and shear adrreezing<br />

strength values obtained by above<br />

ways.<br />

Prom Table I and 11 we can see that the tensile<br />

adfreezing strength is greater than the shear .<br />

adfreezing strength when the boundary c<strong>on</strong>diti<strong>on</strong>s<br />

are the aame (See Fig. 3).<br />

TABLE 5<br />

Tensile and Shear Adfreezing Strength between<br />

Frozen Soil and C<strong>on</strong>crete Foundati<strong>on</strong><br />

1-2 13.6<br />

1-10 12.3<br />

1-14 13.2<br />

1-1 5 13.3<br />

1-16 11 .o<br />

1-23 11.3<br />

1-8 16.4<br />

1-9 16.4<br />

1-12 20.8<br />

1-1 1 21 .I<br />

2-1 - 1617<br />

2-2 16.7<br />

2030<br />

2050<br />

1070<br />

1950<br />

1950<br />

2090<br />

2090<br />

2020<br />

2000<br />

1970<br />

1970<br />

-4.6<br />

-4.8<br />

-5.3<br />

-5.0<br />

-5.6<br />

-5.4<br />

-4.5<br />

-4.7<br />

-5.1<br />

-4.9<br />

-5.5<br />

-4.9<br />

77.5<br />

97.1<br />

175.5<br />

292.2<br />

126.5<br />

185.3<br />

746.2<br />

507.0<br />

526.6<br />

644.3<br />

393.2<br />

435.4<br />

0.07<br />

0.02<br />

0.39<br />

0.39<br />

0.18<br />

0.36<br />

0.48<br />

0.35<br />

0.57<br />

0.38<br />

0.50<br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

She ax<br />

Shear<br />

II<br />

I-<br />

[ ""<br />

Fig.3 Comparis<strong>on</strong> of Tensile and Shear<br />

Adfreezing Strength<br />

Fig.4<br />

Relati<strong>on</strong>ship between Adfreezing<br />

Strength and Tensile Destroying<br />

Creep Displacement<br />

1057

TABLE I1<br />

Tensile and Shear Adfreeeing Strength between<br />

Frozen Soil and Steel Foundati<strong>on</strong><br />

5-5<br />

4-3<br />

4-5<br />

6-2<br />

6-3<br />

6-4<br />

4-4<br />

5- 1<br />

2-2<br />

3-2<br />

1-5<br />

1-4<br />

6-2<br />

4-2<br />

5-2<br />

6-1<br />

6-3<br />

6-4<br />

5-4<br />

4-5<br />

5-5<br />

, 6-5<br />

15.5<br />

15.8<br />

17.8<br />

15.6<br />

15.6<br />

15.6<br />

15.8<br />

15.5<br />

15.9<br />

13.7<br />

12.7<br />

15.7<br />

15.6<br />

15.8<br />

15.5<br />

15.6<br />

15.6<br />

1960<br />

2086<br />

1080<br />

2070<br />

2070<br />

2070<br />

2080<br />

1960<br />

2030<br />

2040<br />

2030<br />

2030<br />

2070<br />

2080<br />

1960<br />

2070<br />

2070<br />

15.6 2070<br />

15.5 1960<br />

15.8 2080<br />

15.5 1960<br />

15.6 2070<br />

-4.8<br />

-5.5<br />

-5.1<br />

-5.3<br />

-5.3<br />

-5.3<br />

-5.3<br />

-7.2<br />

-4.8<br />

-4.8<br />

-11.9<br />

-12.5<br />

-5.4<br />

-5.1<br />

-5.1<br />

-5.2<br />

-5.5<br />

-5.7<br />

-5.9<br />

-6.0<br />

-6.4<br />

-5.9<br />

1583.8<br />

1820.1<br />

1778.9<br />

2008.4<br />

1564.2<br />

1981.9<br />

1934.9<br />

2426.2<br />

1388.6<br />

1372.0<br />

3490.2<br />

4116.8<br />

1260.1<br />

1348.4<br />

1206.2<br />

1415.1<br />

1193.5<br />

1321 .O<br />

1503.4<br />

1731.9<br />

1785.8<br />

1442.6<br />

0.40<br />

0.45<br />

0.11<br />

0.75<br />

0.52<br />

0.73<br />

0.16<br />

0.95<br />

0.81<br />

0.14<br />

0.65<br />

1.30<br />

1.21<br />

1.39<br />

0.65<br />

1.49<br />

1.94<br />

0.59<br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Pensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tenai<strong>on</strong><br />

Tensi<strong>on</strong><br />

Tensi<strong>on</strong><br />

Shear<br />

Shear<br />

Shear<br />

Shear<br />

Shear<br />

Shear<br />

Shear<br />

S'hear<br />

Shear<br />

Shear<br />

Putting together the tensile and shear adfreezing<br />

strength which are obtained under the similar<br />

water c<strong>on</strong>tent, we have Fig. 3. It is shown<br />

that the tensile adfreezing strength is about<br />

25% greater than the shear adfreezing strength<br />

when the temperature are tne same.<br />

Tne features of the interrace-under tensi<strong>on</strong> as<br />

following:<br />

(i)<br />

(ii)<br />

the tensile destroying creep diaplacement<br />

of the inxerface between tne frozen<br />

soil and foundati<strong>on</strong> ia amkller, and<br />

generally ranges from fracti<strong>on</strong> of a<br />

millimeter to <strong>on</strong>e millimeter (see Table<br />

1 and 11). It increases with the tensile<br />

adrreezing strength, and at the<br />

end tends ,to a c<strong>on</strong>stant value (see Fig. Pig.5 Relati<strong>on</strong>ship between Adfreezing<br />

4). This value ie about 0.8 mm. But<br />

Strength and Shear Destroying<br />

The shear destroying creep displacement<br />

creep Displacement<br />

value Is generally greater. Yhe relati<strong>on</strong>ship<br />

between the shear adireezing<br />

strength and destroying creep displace- the deformati<strong>on</strong> increases quickly. It<br />

ment is shown in Yig. 5. When the ad-<br />

indicates that the interface has also a<br />

ireezing strength is leas than 2000 kpa<br />

behaviour that bel<strong>on</strong>gs to the plastic<br />

the shear destroying creep displacement<br />

materials.<br />

ranges from a iracti<strong>on</strong> of' a millimeter Except the natures menti<strong>on</strong>ed above, the tenei<br />

to two millimeter.<br />

adfreezing atrength is eimllar to the shear<br />

tne stresa4min relati<strong>on</strong> tends to De freezing strength. Its features depend up<strong>on</strong><br />

n<strong>on</strong>linear when the interface is tensed. the soil type, water c<strong>on</strong>tent, temperature, load<br />

It has the behaviour that Del<strong>on</strong>ga to acting time and foundati<strong>on</strong> material as stated<br />

the typical Drittle materials, i.e. by Ping Jingkang in 1983.<br />

them is no tuxn <strong>on</strong> the stress-strain The teste indicate that as the water c<strong>on</strong>tent of<br />

curve (see Fig. b), However, it is the soil in interface is different, the tensile<br />

founded from the cmve that the inter- adfreezing strength ie not the same. When the<br />

face ia yielded when tne stress <strong>on</strong> the moisture is less than that of the liquid limit<br />

interface reaches to tne limit. i.e. as of the soil. the tensile adfreezinu strenRth

.,.mil - .. .<br />

Fig.6<br />

Tensile Stress-Strain Curve of the<br />

Interface of Frozen Soil and C<strong>on</strong>crete<br />

Foundati<strong>on</strong><br />

Fig.7<br />

Relati<strong>on</strong>ship between hater C<strong>on</strong>tent<br />

and Tensile Adfreezing<br />

Strength<br />

The variati<strong>on</strong> of soil type at the interface adfreezing strength, the former is generally<br />

will make the c<strong>on</strong>tact properties between frozen 25% or so greater than the later.<br />

soil and foundati<strong>on</strong> diirerent, i.e. it will There is B behaviour of brittle materials u-hen<br />

change the number of ice stuck c<strong>on</strong>tact point the interface is destroyed by tensi<strong>on</strong>, and<br />

and the features of ice film bezween frozen there does not exist residual tensile adfreezsoil<br />

and foundati<strong>on</strong>, so that the tensile ad- ing strength.<br />

Sreezing strength will be different. After she The tensile deatroying creep displacement value<br />

sample are destroyed it i0 discovered oy tne of the interface is smaller and the limit value<br />

obaervati<strong>on</strong>a to the interface that there is<br />

is about 0.8 m.<br />

always an ice film not <strong>on</strong>ly <strong>on</strong> th8 c<strong>on</strong>cre'Ge but That the shear adfreezing strength is used ins<strong>on</strong><br />

the steel foundati<strong>on</strong> as well. 1-1; is the tead of the tensile adfreezing strength for<br />

features of this ice rilm that defines be- the calculating the stability of foundati<strong>on</strong> is<br />

haviour 02 the tensile adfreezing atrengzh of tending to be <strong>on</strong> the safe side. In order to<br />

the interface.<br />

simple the calculating and safety store, that<br />

The test results of the teneile adfreezing we uae the shear adfreezing strength for all<br />

strength at difXerent tempera-curas ana loading freezing interfaces to calculate the stability<br />

velocities are listed in Table 1 and 11. One of foundati<strong>on</strong> is all right.<br />

can see from the tables tnat the tensile ad-<br />

I'reezing strength increases wi'Gh the negative<br />

temperatures and decreases wish the load acting<br />

tune. Por example, the tensile adfreezing REFERENCE<br />

sfrength between froaen soil and s-ceel foundati<strong>on</strong>,<br />

when the temperature <strong>on</strong> the imerrace Cheitovich, H.A. (1973). The mechanics of<br />

cnangea from -4.tlOc: to -12. ~OL!, ranges t'rom<br />

frozen ground. 178-183. High School Press.<br />

1*83.& kpa to 4116.8 kpa. 11' we ignore %ne<br />

Moscow.<br />

difference of the influence of steel and c<strong>on</strong>crete<br />

<strong>on</strong> adfreezing strength, the tenaile ad-<br />

Ding Jingkang (1983). Study <strong>on</strong> the l<strong>on</strong>g-term<br />

freezing strength rangea averagely from 1800<br />

resiatant force of anchor rod in pernakpa<br />

to =OO kpa when the loading velocity<br />

frost. Proc. of the Sec<strong>on</strong>d Nati<strong>on</strong>al<br />

changes from 94 N,&i./Cm2 to 0.02 N/Mi,/Cm2.<br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong> of China. 295-<br />

303. Ganau People's Publishing Howe.<br />

Wu Ziwang (1983). The strength and destroying<br />

properties of frozen soil. Proc. of the<br />

CONCLUSION<br />

Sec<strong>on</strong>d Nati<strong>on</strong>al <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong><br />

of China. 276-283. Gansu Peoplela Publi-<br />

The tensile adfreezing strength between frozen shing House,<br />

soil and foundati<strong>on</strong> is not equal to the shear<br />

1059

INTERACTION BETWEEN A LATERALLY LOADED PILE AND FROZEN SOIL<br />

L. Domaschukl, L. Franss<strong>on</strong>z and D.H. Shields<br />

Wniversity of Manitoba, Winnipeg, Canada<br />

Wniversity of Luld, Sweden<br />

SYNOPSIS The. paper describes the creep behaviour of a laterally loaded pipe pile, 150<br />

mm square and 1800 nun l<strong>on</strong>g, embeded in a frozen sand. Plate load cells mounted al<strong>on</strong>g the bearing<br />

face of the pile measured the soil reacti<strong>on</strong> forces. Initially the distributi<strong>on</strong> of the reactive<br />

forces was n<strong>on</strong>linear with depth but as creep of the pile occurred, the forces near the top of the<br />

pile decreased, while those further down the pile increased. Ultimately the distributi<strong>on</strong> became<br />

linear with depth.<br />

INTRODUCTION<br />

The subject of laterally loaded piles in<br />

frozen soil has recently taken <strong>on</strong> added<br />

importance because of such works as c<strong>on</strong>structi<strong>on</strong><br />

of above-ground pipelines in permafrost<br />

regi<strong>on</strong>s and proposed offshore drilling platform<br />

c<strong>on</strong>structi<strong>on</strong> in the arctic. To date,<br />

very few studies of laterally loaded piles in<br />

frozen soil have been carried out and the<br />

analysis of lateral pile deflecti<strong>on</strong>s is still<br />

in its infancy. To the writers' knowledge,<br />

the <strong>on</strong>ly frozen soil-lateral pile load test<br />

data in the literature are those reported by<br />

Rowley et al. (1975) for full scale tests<br />

carried out at Inuvik, Canada. Nix<strong>on</strong> (1984)<br />

presented some results of small scale lateral<br />

pile load tests that he c<strong>on</strong>ducted in ice,<br />

which could have applicati<strong>on</strong> to ice-rich<br />

soil.<br />

In the analysis of their test data, Rowley et<br />

al. treated the frozen soil<br />

as a Winkler<br />

foundati<strong>on</strong> with a subgrade modulus, k, that<br />

was both load and time dependent. For a<br />

fixed time, k decreased with increasing load<br />

and for a fixed load, k decreased with time<br />

because of the creep behaviour of the soil.<br />

To predict the load-deflecti<strong>on</strong> relati<strong>on</strong>ship,<br />

the authors suggested a procedure in which<br />

the problem of pressure-creep expansi<strong>on</strong> of a<br />

cylindrical cavity was transformed into a<br />

pressure-settlement relati<strong>on</strong>ship for a strip<br />

load which was then used to obtain the pressure-deflecti<strong>on</strong><br />

relati<strong>on</strong>ship for the pile.<br />

Nix<strong>on</strong> (19841, and Neukirchner and Nix<strong>on</strong><br />

(1986) analyzed the Rowley et al. data as<br />

well as the Nix<strong>on</strong> data assuming the<br />

soil<br />

exhibited sec<strong>on</strong>dary creep <strong>on</strong>ly. Their soluti<strong>on</strong><br />

was based <strong>on</strong> the premise that after a<br />

period of load distributi<strong>on</strong> and adjustment,<br />

the pile rotated at a uniform angulas rate<br />

about some definable point. It was tacitly<br />

assumed that the behaviour of the pile<br />

changed from that of a flexible pile to that<br />

of a rigid pile with time. The soluti<strong>on</strong> pre-<br />

dicted the changes in pile deflecti<strong>on</strong>, the<br />

pile moment and the soil pressure al<strong>on</strong>g the<br />

length of the pile with time.<br />

The purpose of the writers' current investigati<strong>on</strong><br />

is to provide much needed test data <strong>on</strong><br />

laterally loaded piles in frozen soil under<br />

c<strong>on</strong>trolled c<strong>on</strong>diti<strong>on</strong>s of soil, , temperature<br />

and load applicati<strong>on</strong>. To this end, a largescale<br />

experimental model study is being<br />

carried out in which the load distributi<strong>on</strong><br />

al<strong>on</strong>g the pile length and its redistributi<strong>on</strong><br />

due to creep is measured in additi<strong>on</strong> to the<br />

pile deflecti<strong>on</strong>. This, paper deals with the<br />

details of the test equipment and procedure,<br />

and some preliminary load-deflecti<strong>on</strong> test<br />

data.<br />

TEST SET UP<br />

Test Facility<br />

The test facility c<strong>on</strong>sists of a pit 2.5 m<br />

square and 2 m deep with reinforced c<strong>on</strong>crete<br />

walls and floor, 200 mm thick, insulated with<br />

200 mm of rigid insulati<strong>on</strong> <strong>on</strong> the outside and<br />

100 mm of rigid insulati<strong>on</strong> <strong>on</strong> the inside.<br />

Platecoil panels made from 14 gauge carb<strong>on</strong><br />

steel and measuring 737 mm by 2108 . m m were<br />

placed al<strong>on</strong>g the sides and the bottom of the<br />

pit. The side panels and the bottom panels<br />

were interc<strong>on</strong>nected separately. to provide two<br />

independent flow networks. The pit is housed<br />

in an insulated room 5 m square and 3 m high.<br />

A 5 hp air-cooled compressor is used to<br />

refrigerate the room and a 3 hp air-cooled<br />

compressor is used to circulate refrigerant<br />

through the platecoil panels. Thermostatically<br />

c<strong>on</strong>trolled solenoid expansi<strong>on</strong> valves<br />

permit independent temperature c<strong>on</strong>trol of the<br />

bottom and side panels. Four vertical strings<br />

of thermocouples mounted <strong>on</strong> l<strong>on</strong>g wood stakes<br />

were positi<strong>on</strong>ed from the centre of the pit to<br />

a wall panel to m<strong>on</strong>itor soil temperatures.<br />

The thermocouple spacing was 200 mm al<strong>on</strong>g each<br />

1060

Fig. 1.<br />

(bl Plan ,Vlrw of Pile Arrangement, Loading<br />

200mm INSUL. 2<br />

200mm REINF. CONCR.<br />

A<br />

100mm INSUL.<br />

FROZEN<br />

TEST PILE<br />

(a) Cross Secti<strong>on</strong> of Pit<br />

"k"<br />

System<br />

Test facil'ity: (a) secti<strong>on</strong> through<br />

pit; (b) planview of pile arrangement<br />

and loading system.<br />

U<br />

-16mm<br />

-STRAIN<br />

ROD<br />

OUAQES<br />

1 1<br />

string. A sketch of the test pit is shown in<br />

Fig. la.<br />

Test Pile<br />

The test pile c<strong>on</strong>sisted of tubular pipe, 150<br />

mm square and 1800 mm l<strong>on</strong>g with a wall. thick-<br />

ness of 6 mm. Nine rectangular plates, 150<br />

mm x 125 mm, and 13 nun thick, were mounted<br />

al<strong>on</strong>g the fr<strong>on</strong>t face of the pile by means of<br />

bolts that passed through holes in the fr<strong>on</strong>t<br />

face to the back face where they were securely<br />

fastened. Four bolts were used for each<br />

plate. A 15 mm gap was left between the<br />

individual plates and a 13 nun gap was left<br />

between the plates and the face of the pile.<br />

These spaces were filled with polyurethane<br />

foam. The bolts were formed from 16 mm steel<br />

rods and were made into load cells by reducing<br />

their diameters and mounting two strain<br />

gauges <strong>on</strong> each reduced secti<strong>on</strong>. The machined<br />

diameters varied from 12 mm for the top plate<br />

to 4 mm for the bottom plate in an attempt to<br />

maintain approximately the same accuracy in<br />

view of the anticipated reducti<strong>on</strong> in reactive<br />

pressurewithdepth.Eachplateload cell<br />

was calibrated individually. The stiffness<br />

of the instrumented pile, EI, as determined<br />

from a deflecti<strong>on</strong> test, was 2.53 x lo3 kNm2.<br />

A sketch of the instrumented pile is shown in<br />

Fig. 2.<br />

Soil<br />

A medium sand, the grain size distributi<strong>on</strong> of<br />

which is shown in Fig, 3, was placed in the<br />

pit. A polyethylene liner , 0.5 mm thick, was<br />

used to separate the sand from the platecoil<br />

panels in order to prevent adfreeze forces<br />

from acting <strong>on</strong> the panels. A LOO nun layer of<br />

wet sand was first placed in the bottom of<br />

the pit, two reacti<strong>on</strong> piles and thermocouple<br />

strings were positi<strong>on</strong>ed in the sand and the<br />

sand was allowed to freeze. Sand was then<br />

placed in the pit in a loose saturated state<br />

-<br />

1<br />

I 40 30<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

SlLlCONE SEAL<br />

/<br />

4,<br />

I<br />

j , Ij<br />

I<br />

* I<br />

a) PILE<br />

b) SECTION A-A<br />

GRAIN SIZE lmm)<br />

FINE SAND COARSE<br />

Fig. 2.<br />

(a) Instrumented pile; (b) details<br />

of plate load cell.<br />

Fig. 3.<br />

Grain-size distributi<strong>on</strong> of the sand.<br />

1061

using the following procedure.<br />

A rectangular wetting tank 2.8 m x 0.7 m and<br />

0.6 m high was c<strong>on</strong>structed out of sheet<br />

metal. A metal divider was placed 0.4 m from<br />

<strong>on</strong>e end so as to create a reservoir. The<br />

bottom of the divider was perforated to<br />

permit water to flow into and out<br />

of the<br />

reservoir. The lower half of the remainder of<br />

the tank was filled with uniformly graded<br />

at<strong>on</strong>e having a maximum size of 38 m. A sand<br />

c<strong>on</strong>tainer 2.4 m l<strong>on</strong>g and 0.7 m wide was<br />

c<strong>on</strong>structed with a bottom made of expanded<br />

steel having approximately 6 nun openings.<br />

This c<strong>on</strong>tainer was set inside the tahk so<br />

that it rested <strong>on</strong> the surface of the st<strong>on</strong>e<br />

layer. Air dry sand was placed in the c<strong>on</strong>tainer<br />

to a depth of about 150 mm. Water was<br />

then pumped into the reservoir from which it<br />

flowed into the st<strong>on</strong>e layer and up into the<br />

sand. The level of the water was brought to<br />

the surface level of the sand. The water was<br />

then drained to a Level below the bottom of<br />

the sand c<strong>on</strong>tainer leaving the sand in a<br />

partially saturated state. The c<strong>on</strong>tainer<br />

with the sand was then lifted out of the tank<br />

and lowered into the pit which had about a<br />

300 mm layer of cold (OOC) water above the<br />

sand in place. The c<strong>on</strong>tainer was lowered just<br />

below the surface of the water and the sand<br />

flowed out of the c<strong>on</strong>tainer and was thus<br />

deposited by sedimentati<strong>on</strong>. Openings were<br />

left in the bottom of the c<strong>on</strong>tainer through<br />

which the reacti<strong>on</strong> piles and thermocouple<br />

strings passed as the c<strong>on</strong>tainer was lowered<br />

and raised. Sand was placed to a depth of 1.8<br />

m in this fashi<strong>on</strong>. The final layer of sand<br />

was levelled off manually, which caused some<br />

disturbance within this upper layer.<br />

Freezing Procedure<br />

The sand was frozen unidirecti<strong>on</strong>ally upward.<br />

The bottom panels were maintained at a temperature<br />

of -3OoC, the side panels were<br />

closed off, and the ambient air temperature<br />

was maintained at OOC. Thermocouple readings<br />

were taken daily. Because the sand had been<br />

cooled to near freezing during its placement,<br />

it <strong>on</strong>ly took about 2 days to bring it to<br />

temperatures equal to or less than<br />

O'C.<br />

After 16 days, the temperature of the sand<br />

varied linearly from O°C at the top to -30°C<br />

at the bottom.<br />

To bring the frozen mass to the intended test<br />

temperature of -3'C, the bottom panels were<br />

shut off and the side panels and the ambient<br />

air temperature were set at -3°C. It was not<br />

possible to simultaneously circulate refrigerant<br />

through both the side panel circuit and<br />

the bottom panel circuit at the same temperature<br />

(-3OC) with the particular arrangement<br />

of a single compressor and thermostatically<br />

c<strong>on</strong>trolled expansi<strong>on</strong> values. After a period<br />

of several weeks, a steady state temperature<br />

distributi<strong>on</strong> throughout the mass was achieved<br />

with a slight vertical temperature gradient.<br />

This state of the temperature was maintained<br />

during the test.<br />

The temperature profiles are shown in Fig. 4<br />

for the following instances: just after the<br />

sand had been placed; 2 days after the freez-<br />

Fig. 4.<br />

Temperature profiles in the sand;<br />

unit weight and soil moisture profiles.<br />

ing process had been initiated (all temperature<br />

at or below O O C ) ; and during the test.<br />

Densities and ice c<strong>on</strong>tents of the sand were<br />

determined to a depth of 800 mm after the<br />

test had been underway for several weeks.<br />

This was d<strong>on</strong>e by coring. The data is shown<br />

in Fig. 4. The dry densities ranged between<br />

15 and 16 kN/mJ and ice c<strong>on</strong>tent increased<br />

from about -21% near the surface to about<br />

23.5% bey<strong>on</strong>d the 700 nun depth. Some drying<br />

of the sand had occurred through sublimati<strong>on</strong><br />

near the surface despite occasi<strong>on</strong>al watering<br />

of the surface.<br />

Test Pile Assembly<br />

Two piles, identical in secti<strong>on</strong> and length to<br />

the test pile were used as reacti<strong>on</strong> piles.<br />

They were installed jbefore the sand was placed<br />

as menti<strong>on</strong>ed previously. The test pile was<br />

installed after the sand had been placed and<br />

frozen. This was achieved by stacking circular<br />

polystyrene discs, 300 mm in diameter and<br />

100 mm thick at the test pile locati<strong>on</strong> as the<br />

sand was being placed. The discs were subsequently<br />

removed, the test pile was put into<br />

place and the annular space between the pile<br />

and the frozen soil was filled with saturated<br />

precooled sand in thin lifts to the top of the<br />

upper plate load cell of the test pile. The<br />

pile embedment was such that the centre of the<br />

first plate load cell was 100 mm below the<br />

surface of the sand. The space above the top<br />

of the upper plate cell (37.5 mm) was filled<br />

with insulati<strong>on</strong>. The back side of the pile<br />

was greased before it was installed to prevent<br />

the soil from freezing to it. The sides of<br />

the pile were left untreated. A yoke was used<br />

to transfer the load from the test pile to the<br />

reacti<strong>on</strong> piles. The load was applied to the<br />

pile through an assembly of dead weights and<br />

hydraulic rams (Fig. lb) and was measured at<br />

the pile with a load cell. Pile deflecti<strong>on</strong>s<br />

were measured with an linear variable differential<br />

transformer (LVDT)<br />

.<br />

1062

TEST PROCEDURES AND RESULTS<br />

Reacti<strong>on</strong> Pile Test<br />

The two reacti<strong>on</strong> piles were subjected to a<br />

series of short term lateral load tests to<br />

obtain an indicati<strong>on</strong> of the creep behaviour<br />

of the frozen sand and the load capacity of<br />

the piles. The piles were jacked toward each<br />

other to eliminate the need for a reacti<strong>on</strong><br />

frame. The point of load applicati<strong>on</strong> and<br />

deflecti<strong>on</strong> measurement was 80 mm above the<br />

sand surface. The loads applied were 20, 40,<br />

60, 80, 100, and 120 kN. Each load was left<br />

<strong>on</strong> until the creep rate had decreased to less<br />

than 0.5 mm per day. At the end of the loading<br />

stage, the piles were unloaded and the<br />

rebound was measured.<br />

The pile deflecti<strong>on</strong>s and rebound axe shown as<br />

a functi<strong>on</strong> of time in Fig. 5. The deflecti<strong>on</strong>s<br />

7- 4 1<br />

-the oil within the system so as to cause some<br />

displacement of the pist<strong>on</strong> and thus destroy<br />

the static fricti<strong>on</strong>. This proved to be quite<br />

satisfactory and is now d<strong>on</strong>e <strong>on</strong> a daily<br />

basis. unfortunately, this was not: d<strong>on</strong>e for<br />

the first two load increments, and therefore<br />

there were some fluctuati<strong>on</strong>s in the magnitude<br />

of the loads. when the deflecti<strong>on</strong> had attenuated,<br />

the load was increased 65 to kN.<br />

The .results of the first two load increments<br />

are included in this paper. The loads and<br />

pile deflecti<strong>on</strong>s are shown as a functi<strong>on</strong> of<br />

time in Fig. 6. Significant fluctuati<strong>on</strong>s in<br />

load occurred primarily at the start of each<br />

load applicati<strong>on</strong> and remained essentially<br />

c<strong>on</strong>stant thereafter. There were corresp<strong>on</strong>ding<br />

fluctuati<strong>on</strong>s in the pile deflecti<strong>on</strong>s.<br />

The deflecti<strong>on</strong>s generally increased with time<br />

at a decreasing rate for each load increment<br />

and essentially attenuated in approximately<br />

100 hss. The attenuated aeflecti<strong>on</strong> was about<br />

1 mm for the 35 kN load and approximately 3<br />

mm for the 60 kN load.<br />

9 40<br />

s SO<br />

r<br />

2.0 3.0 4.0<br />

TIME (DAYS)<br />

d<br />

Fig. 5.<br />

Results o f tests <strong>on</strong> reacti<strong>on</strong> piles.<br />

were corrected to fake into account the distorti<strong>on</strong><br />

of the pile secti<strong>on</strong> due to the c<strong>on</strong>centrated<br />

force acting <strong>on</strong> the face of the<br />

pile. The piles underwent primary creep<br />

under each load increment within the short<br />

*he intervals used. The total deflecti<strong>on</strong><br />

was approximately 5 nm. The rebound followmg<br />

load removal was approximately 4 mm and<br />

therefore the permanent creep was <strong>on</strong>ly about 1<br />

mm under the given test c<strong>on</strong>diti<strong>on</strong>s.<br />

Test Pile<br />

The first load increment applied to the test<br />

pile was 35 kN, The point of load applicati<strong>on</strong><br />

and deflecti<strong>on</strong> measurement was 100 mm<br />

above the sand surface. Some difficulty was<br />

encountered in keeping the load c<strong>on</strong>stant<br />

because of fricti<strong>on</strong> in the hydraulic cylinder<br />

to which the dead weight, W, was attached<br />

(Fig. lb) . Attempts were made to reduce the<br />

fricti<strong>on</strong> by such means as wrapping the cylinder<br />

with heating coils, attaching mechanical<br />

vibrators to the cylinder, etc. The final<br />

soluti<strong>on</strong> was to periodically bleed off some of<br />

1063<br />

Fig. 6.<br />

TIME lhr x 1001<br />

Loads and pile deflecti<strong>on</strong>s versus<br />

time .<br />

The reactive soil forces recorded for those<br />

load cells registering compressive forces axe<br />

shown plotted as a functi<strong>on</strong> of time in Fig.<br />

7. All other load cells registered zero or<br />

slightly negative values. Since the load<br />

cells were mounted <strong>on</strong> the fr<strong>on</strong>t face <strong>on</strong>ly,<br />

there was no way of knowing the load distributi<strong>on</strong><br />

al<strong>on</strong>g the entire pile length. The<br />

data indicates that as creep occurred, there<br />

was a redistributi<strong>on</strong> of the reactive forces<br />

acting <strong>on</strong> the pile. Generally, there *a6 a<br />

reducti<strong>on</strong> in the reactive forces near the top<br />

of the pile and an increase in the reactive<br />

forces lower down. In the case of the 35 kN<br />

load there was a slight reducti<strong>on</strong> in the<br />

force registered in the uppermost cell, and a<br />

slight increase in the next three lower<br />

cells. In the case of the 60 kN load there<br />

was a substantial reducti<strong>on</strong> in the uppermost<br />

cell, a slight reducti<strong>on</strong> in the next lower

f -<br />

9<br />

s<br />

50 - IOOmm DEPTH<br />

40 -<br />

m<br />

0<br />

0 2 8 10 12 14<br />

Figure 7.<br />

TIME (ha x 1001<br />

Reacti<strong>on</strong> loads registered by plate<br />

load cells.<br />

cell, and a significant increase in the next<br />

two lower cells.<br />

The distributi<strong>on</strong>s of measured reactive forces<br />

with depth are shown in Fig. 8 at the start<br />

and at the end of each load applicati<strong>on</strong>. The<br />

distributi<strong>on</strong> indicates that the compressive<br />

Fig. 8.<br />

REACTIVE LOA0 (kN)<br />

0 1 2 3 4<br />

OEFLECflW- (mn)<br />

(a) Distributi<strong>on</strong> of measured reactive<br />

forces with depth; (b) Calculated<br />

pile deflecti<strong>on</strong> profiles<br />

1064<br />

reactive soil forces which acted <strong>on</strong> the face<br />

of the pile extended to a depth of about 520<br />

mm for the 35 kN load and about 660 mm for the<br />

60 kN load, or roughly the upper third of the<br />

embedded depth of the pile. As well, with<br />

time, the redistributi<strong>on</strong> for both loads tended<br />

towards a linear distributi<strong>on</strong> with depth.<br />

The deflecti<strong>on</strong> profile of the pile was not<br />

measured during the test. An approximate<br />

deflecti<strong>on</strong> profile was calculated by simply<br />

treating the pile as a cantilever beam<br />

carrying a series of c<strong>on</strong>centrated known<br />

forces c<strong>on</strong>sisting,of the applied load and the<br />

reactive forces measured by the plate cells.<br />

The beam was assumed to be cantilevered at<br />

the point of zero reactive force. The<br />

initial and final deflecti<strong>on</strong> profiles thus<br />

calculated for the 60 kN applied load are<br />

shown in Fig. 8(b). A comparis<strong>on</strong> of the<br />

computed deflecti<strong>on</strong>s of the top of the pile<br />

(Fig. 8b) with the measured deflecti<strong>on</strong>s '(Fig.<br />

6) shows very good agreement, lending<br />

credence to the assumpti<strong>on</strong>s made in computing<br />

deflecti<strong>on</strong>s. The change in deflecti<strong>on</strong> curve<br />

with time due to soil creep indicates that<br />

the maximum bending moment alao changes with<br />

time. This points out the importance<br />

of<br />

knowing the redistributi<strong>on</strong> of reactive pressuxes<br />

<strong>on</strong> a pile due to creep when ascertaining<br />

the structural requirements of the pile.<br />

CONCLUSIONS<br />

A new facility has been developed which<br />

allows large scale piles to be inserted into<br />

frozen soil or ice and then tested under<br />

lateral load. The c<strong>on</strong>clusi<strong>on</strong>s which can be<br />

drawn from the- first test in the facility<br />

are :<br />

1.<br />

2.<br />

3.<br />

4.<br />

5.<br />

A 150 nun square pile embedded in a<br />

frozen sand, when subjected to loads of<br />

35 kN and 60 kN, underwent attenuating<br />

deflecti<strong>on</strong> due to creep of the frozen<br />

sand. The total attenuated deflecti<strong>on</strong><br />

was approximately 3 mm.<br />

The time to attenuati<strong>on</strong> was about 100<br />

hours for each load.<br />

Load cells mounted <strong>on</strong> the bearing face of<br />

the pile indicated that the compressive<br />

reactive forces acting <strong>on</strong> the face of the<br />

pile extended to a depth of about four<br />

pile diameters, or roughly <strong>on</strong>e-third the<br />

embedment depth of the pile. The depth<br />

to the point of rotati<strong>on</strong> (or fixati<strong>on</strong>)<br />

increased slightly with load.<br />

The initial distributi<strong>on</strong> of compressive<br />

reactive soil forces <strong>on</strong> the face of the<br />

pile was n<strong>on</strong>linear with depth.<br />

As a result of creep, the distributi<strong>on</strong> o<br />

reactive forces became linear with depth.

REFERENCES<br />

Neukirchner, R.J. and Nix<strong>on</strong>, J.F. (1987).<br />

Behaviour of Laterally loaded piles in<br />

permafrost. Jour. of Geot. Eny., Vol.<br />

113, No. 1, Jan., 1-14.<br />

Nix<strong>on</strong>, J.F. (1984). Laterallv loaded oiles<br />

in permafrost. Can. Gdot. Jou;. , Vol.<br />

21, 431-438.<br />

Rowley, R.K., Wats<strong>on</strong>, G.H. and Ladanyi, B.<br />

(1975). Predicti<strong>on</strong> of pile performance<br />

in permafrost under lateral load. Can.<br />

Geot. Jour., Vol. 12, 510-523.<br />

ACKNOWLEDGEMENTS<br />

The writers' wish to acknowledge the financial<br />

assistance provided by NSERC, Ottawa, Canada,<br />

and the Swedish American Foundati<strong>on</strong>. As<br />

well, special thanks qo to Mr. Brian Turnbull<br />

and Mr. Ed Lemke, who provided invaluable<br />

assistance in setting up the testing<br />

facility.<br />

1065

CHOICE OF PARAMETERS OF IMPACT BREAKAGE<br />

OF FROZEN SOILS AND ROCKS<br />

AI, Fedulov and V.N. Labutin<br />

Mining Institute of the Siberian Branch of the USSR<br />

Academy of Sciences, Novosibirsk, USSR<br />

ABSTRACT The paper deals with the technological schemes of breakage of various hard<br />

materials including seas<strong>on</strong>al-frozen soils and ever-frozen rocka by impact load; a change of the<br />

parameters of the process, its acti<strong>on</strong> and a change in time a e shorn. The c<strong>on</strong>cept c<strong>on</strong>cerning<br />

the specific per unit length of impact per Load unit of length of a blade of a wedge-like<br />

tool is introduced.The character of a change of the comp<strong>on</strong>ents of force of breakage, the values<br />

of an angle of positi<strong>on</strong>ing of the tool, the intensity and the energy-intensi%y of the process<br />

is established. The obtained materials of the investigati<strong>on</strong>s are the basis for creatjng the<br />

real working members for practice of breaking and mining of hard materials.<br />

The industrial exploitati<strong>on</strong> of the districks technological processes of separati<strong>on</strong> of a<br />

of the East and the North-East of the Soviet layer of a material, its extracti<strong>on</strong> and<br />

Uni<strong>on</strong> is associated with uLning of<br />

mini%. Tf the first <strong>on</strong>e is associated with<br />

c<strong>on</strong>siderable volumes of rocks and seas<strong>on</strong>al-<br />

single acti<strong>on</strong> completing with a crack of<br />

frozen soils as well as ever-frozen <strong>on</strong>es.<br />

a specimen, the sec<strong>on</strong>d <strong>on</strong>e supposes some<br />

A traditi<strong>on</strong>al method of the soluti<strong>on</strong> this of c<strong>on</strong>tinuity of the process and in this<br />

problem is the drilling-and-blasting method c<strong>on</strong>necti<strong>on</strong> it must possess the high<br />

of loosening followed by loading and transfer efficiency.<br />

of rock mass by the mechanisms of various<br />

As a result,of the analfiica5 and<br />

types, such as excavators, loaders, scrapers experimental investigati<strong>on</strong>s of the process<br />

and bulldozers, etc. Only to a lesser degree, of impact breakage of various hard makerials,<br />

in some places, the rippers mounted <strong>on</strong> the a number of very important scientlfically<br />

tractors axe used.<br />

and practically dependences were establiahed<br />

AS known the drilling-and-blasting method of making it possible fo approach to the<br />

mining supposes the specific cyclicity of the soluti<strong>on</strong> of the questi<strong>on</strong> about the paramefer<br />

process. At the same time the most advanced of the impact devices for these purposes with<br />

high-producti<strong>on</strong> c<strong>on</strong>tinuous flow process<br />

sufficient validity.<br />

technology supposes c<strong>on</strong>t'inuity of the process. The obtained experimental dependences of some<br />

In fairly hard rocks as well as frozen soila parameters of the impact process (maamum<br />

<strong>on</strong>e may perform this <strong>on</strong>ly by means of the<br />

working members of impact acti<strong>on</strong> which may<br />

provide the high-efficient flow of the process<br />

of breakwe, The existing examples in the<br />

field of percussi<strong>on</strong> drilling of hard rocks<br />

and orea c<strong>on</strong>firm c<strong>on</strong>vincingly the reality of<br />

this directi<strong>on</strong>.<br />

For designing and project- the high -<br />

producti<strong>on</strong> impact devices for breakage, the<br />

initial data of the parameters of the<br />

effective flow of this process axe required.<br />

Over a l<strong>on</strong>g period of time, under the various<br />

c<strong>on</strong>diti<strong>on</strong>s, the Mining Institute of the<br />

Siberian Branch of the USSR Academy of<br />

Sciences c<strong>on</strong>ducted the investigati<strong>on</strong>s into<br />

the impact method of breakage of coals, frozen<br />

soils which made it possible to obtain a<br />

series of the fundamental results (Nedorezov,<br />

1965, Vikhlyayev, 1969. FeduLov, 1973, 1975,<br />

1977. Fedulev, Pof<strong>on</strong>sky, 1977. Sleptsov,l982),<br />

Durlng the lnvestlgati<strong>on</strong> of impact breakage<br />

of materials, two schemes of loading were<br />

c<strong>on</strong>sidered. The first scheme takes into<br />

account thc various existing in practice<br />

technological processes associated with<br />

breakage of specimens of end sizes (oversizes<br />

of various rocks, laminated, block materials,<br />

etc.), the sec<strong>on</strong>d <strong>on</strong>e is typical of the<br />

1066<br />

impulsive force, pulse length, maximum aeptb<br />

of penetrati<strong>on</strong> per impact) up<strong>on</strong> the quantity<br />

of sequentially deliverFng impacts against<br />

the wedge-like indenter show a fairly sharp<br />

change of their values from impact to impact.<br />

The character of the graph of the maximum<br />

impulsive force representing the curve<br />

innoseasing with a decelerati<strong>on</strong> indicates the<br />

change of the properties of the material<br />

under the indenter, and makes it possible<br />

to draw fhe import=% c<strong>on</strong>clusi<strong>on</strong>s. One may<br />

state that the traditi<strong>on</strong>al indices of the<br />

mechanical properties of the material<br />

characterize <strong>on</strong>ly its c<strong>on</strong>diti<strong>on</strong> before the<br />

first impact and cannot be used in the process<br />

of growth of stresses uadar the tool. On the<br />

other hand, clearly the magnitude of the<br />

maximum force has the most substantial<br />

influence <strong>on</strong> the process intensity (aepth of<br />

penetrati<strong>on</strong> of the indenker) from the very<br />

beginning of the breaking process during the<br />

first impacts.<br />

Thus, for evaluating the effectiveness of the<br />

impact breakage, it; is necessaxy to use the<br />

integral indices characterizing as it a whole<br />

and incluaing the procese intensiky<br />

themselves. Suck index may be represented by<br />

the energy-intensity of breakage of the

material.<br />

As a result of the experiments with the<br />

specimena having the end sizes, it was found<br />

that the energy-intensity of breakage<br />

c<strong>on</strong>siderably depends <strong>on</strong> the impact energy,<br />

For providing the couxse of the process in<br />

tbe mode of thxee-dimensi<strong>on</strong>al bxeakage,with<br />

enough low energy-intensity, the impact energy<br />

and the striker mass must be not less than<br />

some minimum values. Up<strong>on</strong> exceeding the<br />

optimal value of the energy, the energy -<br />

intensity varies <strong>on</strong>ly slightly whereby an<br />

increase of the impact power must lead to<br />

a growth of crushing capacity.<br />

The process of impact breakage may begin<br />

<strong>on</strong>ly at a defined value of load falling at a<br />

per-unit of the indenter size. In this<br />

c<strong>on</strong>necti<strong>on</strong>, particularly, for the wedge-like<br />

tool, the underst8ndiug of "per unit length<br />

of impact energy" was introduced.<br />

The values of the impact parameters as to<br />

the striker energy and maas should be chosen<br />

with due regard for the physico-mechtmical<br />

characteristics of the material to be broken.<br />

Thus, for example, for the efficient flow of<br />

the process of impact breakage of the<br />

specimens with the end sizes, the "per unit<br />

length of impact energy'., such as the energy<br />

referred to the length of the wedge-like tool<br />

blade having , as it haa been established,<br />

the oriented effect of breakage, must be not<br />

below 120-150 J/m - IOm2 for most rocks and<br />

other bard materials. Our knowledge about<br />

the physical essence of the process of<br />

impact breakage of materiala <strong>on</strong>e layer at a<br />

time, at present, reduces to the scheme<br />

according to which the breakage of the<br />

materials by the working member of impact<br />

acti<strong>on</strong> between two succeasive impacts may be<br />

divided c<strong>on</strong>venti<strong>on</strong>ally into three etages t<br />

impact breaking in EL z<strong>on</strong>e of penetrati<strong>on</strong> of<br />

the tool into the material, cueting of a z<strong>on</strong>e<br />

with disturbed links produced after it due to<br />

arising fracturing, and ,.at last, cutting of<br />

undisturbed material under the acti<strong>on</strong> of the<br />

force of the movement of the working member.<br />

Depending <strong>on</strong> the speed of the movement, three<br />

variants of the values of the indices of the<br />

process are poasible of which the most<br />

favowable variant as regards the breaking<br />

intensi-, the magnitude of %he force of the<br />

movement and the apecific energy c<strong>on</strong>sumpti<strong>on</strong>s<br />

is the case when the next impact delivers<br />

after completi<strong>on</strong> of cutting of the zane with<br />

disturbed linke. Such frequency of impacts<br />

makes it possible to obtain, a fairly high<br />

speed of the movement at comparatively small<br />

tractive forces, The optimal values of the<br />

parameters of the process depend <strong>on</strong> the<br />

properties of the medium broken. For example,<br />

to provide a desired magnitude of penetrati<strong>on</strong><br />

of the wedge-like tool when breaking <strong>on</strong>e<br />

layer at a time of a certain thickness of the<br />

frozm soil, the per unit length of impact<br />

energies of no less than 80-100 J/m .<br />

are required. Based <strong>on</strong> the values of the per<br />

unit length of impact energy obtained during<br />

experimenlx, fhe minimum value of the impact<br />

energy for most practical ca8es must be not<br />

below 800-1000 J.<br />

The principle of the impact breakage <strong>on</strong>e<br />

layer at a time has been best widely checked<br />

in the frozen soils and the coals.<br />

The experimental investigati<strong>on</strong>s into the<br />

breakage of the coals were c<strong>on</strong>ducted in the<br />

Kuzbass opencast collieries, of the seas<strong>on</strong>alfrozen<br />

soils in i!IoscovJ, Novosibirsk and<br />

Ust-Kamenogorsk,.of the war-frozen rocks in<br />

the Zapolyaxye mmes.<br />

Subjected to the impact br:;&age were the<br />

coals with hardness of 0.8 to 3.0 according<br />

to Prof. M.X. Protodyal.<strong>on</strong>cv scale, the<br />

seas<strong>on</strong>al-frozen soils of various grain compositi<strong>on</strong>s:<br />

loamy, light sand loam, gravel,<br />

the tempepture of the soils varied between<br />

-1 to -12 C, the humidity betmen 16 to 287;.<br />

The ever-frozen rocks included SO.. .6C$i of<br />

hard fracti<strong>on</strong>s - gravel and quartizitic<br />

bouldels in size to 0.3xO.3fi.3 m and had<br />

a filler as a loamy light sand, clay, silt<br />

and ice (comm<strong>on</strong> icing of the rocks ranged<br />

from 20 to 307i). The temperature of the<br />

frozen mass varied between -7 to -1OOC.<br />

The investigati<strong>on</strong>s were carried out <strong>on</strong> the<br />

specialized fully dimensi<strong>on</strong>al stands developed<br />

and manufactured for the specific c<strong>on</strong>diti<strong>on</strong>s.<br />

of the breakage as well as with the use of<br />

the base machines (excavator, hard-rock<br />

tunneling machine, truck loader) <strong>on</strong> which<br />

the experimental working impact lnembers,such<br />

as the pneumatic hammers with energy per blow<br />

of 500...1700 J and frequency of blows of<br />

6...15 8-l developed by the Mining Institute<br />

of the Siberian Branch of the USSK Acadeiqy of<br />

Sciences were mounted. The equilateral chisel<br />

teeth with the lip -le of 35O were used a8<br />

a tool.<br />

In fhe process of the investigati<strong>on</strong> of the<br />

break%e <strong>on</strong>e layer at a time of the hard<br />

materials, the variaUe parameters were as<br />

follows: the thickness of the layer broken,<br />

the energy per single blow, the physicomechanical<br />

properties of the material, the<br />

distance between the tools - pitch of<br />

break%e, angle of inclinati<strong>on</strong> of tool axis<br />

to plane of face (angle of attack).<br />

According to this, the following magnitudes<br />

were determined; the thic'mess of the broken<br />

layer; the cross secti<strong>on</strong>s and the Lergth of<br />

cuts foxmea after the passage of the iapact<br />

working member; the force of the movement of<br />

the working member; the normal force acting<br />

<strong>on</strong> the tool from the side of the face; the<br />

speed of the movement of the experimental<br />

working members; the durati<strong>on</strong> of the tests;<br />

the physico-mechanical properties of the<br />

material broken.<br />

AS a result of the c<strong>on</strong>ducted investigati<strong>on</strong>s<br />

of the process of the breakqe <strong>on</strong>e layemt a<br />

time of the hard materials using the impact<br />

working members, the knowledge of the physical<br />

essence of the process under investigati<strong>on</strong><br />

was obtained, and in particular the pattern<br />

of the formed trace of the breakage was<br />

revealed. The process of the impact breakage<br />

<strong>on</strong>e layer at a time is outwardly similar to<br />

the process of the cutting, and is followed<br />

by the periodic separati<strong>on</strong> of the elements of<br />

spalling with the formati<strong>on</strong> of the trace of<br />

the breakage, whose cross secti<strong>on</strong> has a form<br />

similar to the trapezoid. The side surfaces<br />

of the trace are inclined to the vertical at<br />

the -le of side splitting which<br />

decreases with an increase of the thickness<br />

of the layer broken (Fig. I). The crosssecti<strong>on</strong>al<br />

area of the trace of the breakwe<br />

1067

varied depending <strong>on</strong> the angle of side split,<br />

y ZQd<br />

Fig.1<br />

Dependence of angle of split <strong>on</strong><br />

thickness of layer broken<br />

I - seas<strong>on</strong>al-frozen soils; 2 - coal<br />

alow the bedding; 3 - coal cross<br />

the bedaing; 4 - amy-year-frozen<br />

rocks<br />

The exterior ap2earance of the trace of the<br />

breakage showed the deformati<strong>on</strong>s of breakingoff<br />

al<strong>on</strong>g the side surfaces and the presence<br />

of crumple and shear <strong>on</strong> its bottom. The share<br />

of the side surfaces increased with an<br />

increase of the thickness of the broken layer,<br />

thus the breakage in thick layers ehould be<br />

recognized more evedient energetically,<br />

The character of the process of the impact<br />

breakage of the coal and frozen soil using<br />

the doubled tools is mainly similar to the<br />

process of the breakage using the single tools<br />

with tho difference that between the teeth a<br />

ridge of undisturbed soil was formed whose<br />

height decreased with an increase of the<br />

thickness of the broken layer h and with a<br />

decrease of the distance beheen the teeth 1<br />

(Fig. 2).<br />

The horiz<strong>on</strong>tal comp<strong>on</strong>ent of the tractive<br />

forces increased with an increase of the<br />

broken layer thickness from the parabolic law<br />

.. (Fie.3).<br />

whm breaking the frozen soils, their physicomechanical<br />

properties and temperature acted <strong>on</strong><br />

the tractive forcas. Thus, when breaking the<br />

sandy loam, the magnitude of the horiz<strong>on</strong>tal<br />

cornp<strong>on</strong>ent was less compared to the gravel and<br />

loamy soils.<br />

The magnitude of the horiz<strong>on</strong>tal comp<strong>on</strong>ent was<br />

dependent <strong>on</strong> the extent of blocking of the<br />

trace of the breakage, In case of the everfrozen<br />

rocks for the blocked, half-blocked and<br />

free schemes of the breakqe,the horiz<strong>on</strong>*al<br />

comp<strong>on</strong>ent in the relative units accounted for<br />

l:O.5tO.3. These data fox the coal presented<br />

in Table show that the broken layer thickness<br />

influences the distributi<strong>on</strong> of the magnitude<br />

of the horiz<strong>on</strong>tal comp<strong>on</strong>ent.<br />

1068<br />

Fig.2<br />

Dependence of ridge height <strong>on</strong><br />

thickness of layer to be broken and<br />

distance between tools<br />

- - coal across the bedding;<br />

- -" - aeasoaal-frozen soils<br />

Thickness<br />

of layer<br />

to be<br />

broken ,<br />

cm<br />

Distributi<strong>on</strong> 09 Foraea for<br />

.Various Breaking Schemes<br />

Form of separati<strong>on</strong> of layer to be<br />

broken<br />

Blooked' Free Half-blocked with<br />

pitch of breakage 1,<br />

cm<br />

30 I 40 I 50 1 60<br />

Force P, , %<br />

I I I<br />

I I I I I I<br />

As the investigati<strong>on</strong>s show the normal comp<strong>on</strong>ent<br />

09 the movement force is directed from the face<br />

or towarda the face, dependirq <strong>on</strong> the magnitude<br />

of the impact energy, the strength of workedout<br />

Boil, the angle of attack and the broken<br />

layer thickness.Tbus,for the broken layer<br />

thickness leea than 15 cm, the tendency for<br />

expelling of the working member from the broken<br />

material was obsemred, particularly this was<br />

marked for more hard soils, low energies of<br />

single impact and low angle of attack. The<br />

optimal angle of setti% of the a ~ of s the<br />

working members (angle of attack) ranged from<br />

25 to 309.<br />

When evaluating the degree of the effecfivenees<br />

of the breaking process, the index of the

specific energy intensity was usea,The total<br />

specific c<strong>on</strong>sumpti<strong>on</strong> of energy was determined<br />

by the 8um of the c<strong>on</strong>sumpti<strong>on</strong> of energy for<br />

the movement of the working member and the<br />

c<strong>on</strong>sumpti<strong>on</strong> of energy for air, inthis case<br />

the share of the latter accounted for 25. ..‘cy0<br />

for the seas<strong>on</strong>al-frozen soils, 60.*.75% for<br />

the coal, up to 94% for the ever-frozen rocks.<br />

between 0.1 and 1 ,T kii-h/m3 depending. <strong>on</strong> their<br />

stpength. The minium values were obtained<br />

when breaking the coal, and the maximum <strong>on</strong>es<br />

when breaking t2:e ever-frozen rocks.<br />

The coefficient of n<strong>on</strong>uniformity of the load<br />

of the working member varied within 1.5 and<br />

2,5, its values decreased with the increase<br />

of the thickness of the Layer to be broken.<br />

Fig.3.<br />

Dependence of horiz<strong>on</strong>tal<br />

comp<strong>on</strong>ent of force of movement <strong>on</strong><br />

thickness of layer to be broken:<br />

1 - energy per impct A=I000 J ,<br />

gravel Boil t =-6 C; 2 - A=I000 S,<br />

loan~y soil, t =-5OC* 3 - A=500 J ,<br />

sandy loam, t =-3*5b; 4 - A=1000 J,<br />

coal* ccompr. = 20 MPa<br />

The specific energy intensity af the<br />

breakage <strong>on</strong>e layer at a time of the hard<br />

materials by means of the impact woxking<br />

members depends <strong>on</strong> the enepgy per impact,the<br />

physico-mechanical propertiaa of the material<br />

to be broken, the thickness of the layer to<br />

be broken (Fig.4), and takes the optimal<br />

value at the definite relati<strong>on</strong>e of the said<br />

parameters<br />

It decreases to a certain limit with an<br />

increase of the thickness of the layer to be<br />

broken, whereup<strong>on</strong> (depending <strong>on</strong> the c<strong>on</strong>ditiom<br />

of the breakage) it begina either to increase,<br />

or remains c<strong>on</strong>stant. The increase of the<br />

energy of single impact of the working member<br />

decreaeee the magnitude of the specific<br />

c<strong>on</strong>sumpti<strong>on</strong> of energy. When breaking the<br />

material using two or several impact tools,<br />

the group influence of the tools <strong>on</strong> the ma33<br />

to be broken occurs.In this oase at defined<br />

values of the pitch of the breakage and the<br />

thickness of the layer to be separated, the<br />

energy intensity of the breakage decreases<br />

in comparis<strong>on</strong> to the operati<strong>on</strong> by <strong>on</strong>e tool,<br />

The specific energy - intensity of the impact<br />

breakage of the studied hard materials varied<br />

Pig.4. Dependence of specific energyintensity<br />

<strong>on</strong> thickness of layer<br />

to be broken :<br />

1 - A-500 5, n=15 s”, frozen loaq<br />

light sand; 2 - A=500 J, k 15 s-1,<br />

frozen Loamy soil; 3 - A=1000 J ,<br />

-9.5 s”’# frozen gravel soil;<br />

4 - A=I~OO J, n=8.3 s”’ , ever-frozen<br />

rocks<br />

The results of the c<strong>on</strong>ducted in-situ<br />

experimental investigati<strong>on</strong>s of the impact<br />

breakage of the coals, frozen soils and rocks<br />

show that the effectiveness of the breakage<br />

aP the hard materials is largely dependent <strong>on</strong><br />

their physico-mechanical properties, grain<br />

compositi<strong>on</strong> and temperature (for seas<strong>on</strong>alfrozen<br />

soils and ever-frozen rocks).<br />

According to the obtained data, the everfxozen<br />

rocks have the greatest resistance,<br />

which is explained by their relative low<br />

temperatures as well as the c<strong>on</strong>tent of silt<br />

and clay in them possessing the high<br />

cementing properties at a negative<br />

temperature.<br />

The greatest intensity-of the impact breakage<br />

was attained in the coals and the se s<strong>on</strong>alfrozen<br />

soils and ranged 150 to 200 m 3 /h far<br />

<strong>on</strong>e impact tool with energy of single impact<br />

1069

1000 S and frequency 9.5 s-'.The intensity<br />

of the breakage of the ever-frozen coarsefragmental.<br />

rocks obt ined during the<br />

experiments was 20 u~; 11 <strong>on</strong> the averaSe. This<br />

index may be increased at the expense of an<br />

increase of the power of the inpact device<br />

and the drive of the working member.<br />

As <strong>on</strong>e nay believe the obtained materials<br />

first resulting from our inveacigati<strong>on</strong>s fall<br />

into the category of the fundmental resulta<br />

making it possible to judge with any<br />

wsuance about the possibili,W a d the<br />

agglicati<strong>on</strong> of the impact breakage. The data<br />

<strong>on</strong> the per snit length of the impact energy<br />

even _ooint to the required levels of the<br />

energy of single impact of the device, and<br />

hence its Jossible structural sizes. The<br />

tendency for an incrcnse of the per unit<br />

length of the inpact energy at the elcpense of<br />

a decrease of the width of the tool invariably<br />

brings about a decrease of the width of<br />

the ,trace of the breakage and may give rise<br />

to difficulties associated with free passage<br />

of the impact device ,through the trace of<br />

the breakage. The similar pattern will be<br />

obse,rved when increasing the ger unit length<br />

of the iapact energy at the expense of the<br />

paraseters of the impact device which with<br />

other c<strong>on</strong>diti<strong>on</strong>s being equal may lead to an<br />

increase of its overall dimensi<strong>on</strong>s. In this<br />

case the tractive forces of the movement<br />

(the horiz<strong>on</strong>tal comp<strong>on</strong>ent of the tractive<br />

forces) sharply increase and the impact<br />

tireaking process stops.<br />

The obtained results of the c<strong>on</strong>ducted in situ<br />

experimental investifati<strong>on</strong>s showed the<br />

outlook of the use of the impact method of<br />

the breakage of the hard coals, frozen soils<br />

and rocks. For realizing this efficient<br />

method of the breakage, the Institute of<br />

Mining of the Siberian Branch of the USSR<br />

Academy of Sciences has developed and a<br />

number of the ~~laxtts produces in quantity<br />

the PXl3OO and PlSl7OO pneumatic hammers<br />

which may be mounted <strong>on</strong> the working e uipmeat<br />

of the hydraulic excavators and used 8or the<br />

breakage of thb various hard materials<br />

includinE; the frozen soils. Based <strong>on</strong> such<br />

inrpsct devices, the experimental models of<br />

the ivolking members of the .thing machines<br />

of various technological aurposes have been<br />

created.<br />

The ouclret cf active acti<strong>on</strong> for the excavators<br />

of structural (with capacity 0.6~~) ana<br />

quarry (4.6 d) classes have advantageously<br />

passed the industrial tests.<br />

The prelianinaxy scientific-engineering<br />

developments and the ec<strong>on</strong>omic designs have<br />

shovm tile possibility of creating the mining<br />

rnachines with the working meabers of impact<br />

acti<strong>on</strong> and for underground mining in the<br />

cocditi<strong>on</strong>s of permafrost.<br />

Vikhliacv,A., Kam<strong>on</strong>skii,V., Pedulov,A, (1969).<br />

Udarnoe razrushenie krepkilrh materialov.<br />

Novosibirsk: NaUa Sibirskoe otdelenie,<br />

158 SO<br />

Fedulov,A., Labutin,V. (1973). Udarnoe<br />

razrushenie uglia. Novosibirak: Nauka<br />

Sibirskoe otdelenie, 120 8.<br />

Fedulov,A., Ivanov, R. (1975). Udarnoe<br />

razrushenie merzlykh gruntov.<br />

Novoaibirakr Nauka Sibirskoe otdelenie.<br />

'135 5.<br />

Fedulov,A. (1977). 0 dvykh skhemakh<br />

udarnogo razrusheniia bsphykh materialov.<br />

Novosibirsk: Bibirakoe otdelenie,<br />

FT PIipL N 6, S, 63-67"<br />

Fedulov,A. Pol<strong>on</strong>skii, G., Karnaulrhov,A.<br />

(19773. Razrabotka merzlykh gruntov<br />

rykhliteliami udunogo deistviia,<br />

Novosibirakt Nauka Sibirskoe otdelenie.<br />

70 8.<br />

BLepcov,A., Fedulov,A., Labu.t;in,V., Kostyrkin,<br />

V, i dr, (1982). Perspektivy sozdanlia<br />

potochnoi tekhnologii na osnove udarnogo<br />

razrwheniia mogoletnemerzlykh gornykb<br />

porod pnevmomolotom PN1300. Magadan,<br />

Kolw, N 11, 8. 7-9.<br />

&J77JCXfj<br />

Nedorezov, I., Eedorov,D., Fedulov,A., Khamc-<br />

.shukov,Yu. ('1965). Hezanie i udarnoe<br />

razrushenie s~~untov. Novosibirsk: Nauka<br />

Sibirskoe otdolenie, 15.2 S.<br />

1070

FROST HEAVE CHARACTERISTICS OF SALINE SOILS AND CANAL DAMAGE<br />

Feng, Ting<br />

Survey and Design Institute of Xinjiang Army Corps of C<strong>on</strong>structi<strong>on</strong>, Shihezi, Xinjiang, P.R. China<br />

SYNOPSIS Canals built <strong>on</strong> the cold, dry and saline soil regi<strong>on</strong>s have been damaged seriously<br />

because of frost heave. A lot of frost heave tests <strong>on</strong> saline soils have been c<strong>on</strong>ducted both in the<br />

lab and in the field. The test results show that the physical and mechanical properties are becoming<br />

worse with the increase in salinity. In particular, a phenomen<strong>on</strong> analogous to liquefacti<strong>on</strong> may<br />

be caused. The freezing point depressi<strong>on</strong> and the frost susceptibility of soils depend <strong>on</strong> the salinity<br />

and the chemistry of the salts in the pore fluid. Under low temperature and dry c<strong>on</strong>diti<strong>on</strong>s,'<br />

crystalline expansi<strong>on</strong> will take place in saline soils, especially in sodium sulphate soils. The<br />

salinity in pore water will be used to judge the freezing stare of saline soils. Water and salts<br />

were redistributed after the canal commenced operati<strong>on</strong>. Frost heave was occurred in the inside<br />

alope of the canals where salts are leached. The large crystallizati<strong>on</strong> expansi<strong>on</strong> occurs in the<br />

areas where salt has aggregated, which will speed up damage of canals.<br />

INTRODUCTION<br />

Xinjiang is located in the dry and cold regi<strong>on</strong><br />

of the inner c<strong>on</strong>tinent. The salinizati<strong>on</strong> of<br />

soils is very serious in most areas of this regi<strong>on</strong>.<br />

The soils c<strong>on</strong>tain sulphates and chlorates<br />

with a salinity of 2-10%. The canals<br />

built in saline regi<strong>on</strong>s are seriously damaged<br />

by periodic diversi<strong>on</strong>, and dry periods with<br />

frost-thaw acti<strong>on</strong>. The investigati<strong>on</strong>s showed<br />

that almost 100% of the canals built in heavily<br />

saline regi<strong>on</strong>s were damaged, so that studies of<br />

frost heave in saline soil, and the resulting<br />

damage to canals are of great significance in<br />

dry and cold regi<strong>on</strong>s.<br />

NATURAL CONDITIONS AT THE TEST FIELD<br />

Tests were c<strong>on</strong>ducted both in the lab and in the<br />

field. The first branch canal of No.148 farm and<br />

the third branch canal of No.150 farm in Mosuo-<br />

.". wan reclamati<strong>on</strong> area were selected aa the testing<br />

sites. These are located in Quaternary alluvial<br />

deposits at the southern Zhungeer Basin<br />

in the Northern slope of the Tian Mountain. The<br />

soil is classified as silty loam with a thickness<br />

of more than 13 m.<br />

The annual air temperature at the test sites is<br />

5-7OC <strong>on</strong> the average. The maximum air temperature<br />

is 43'C. and the minumum is -42.8'C. The<br />

period when the maximum daily air temperature<br />

below OOC lasts 120-150 days <strong>on</strong> average. This<br />

is an arid area so that agricultural producti<strong>on</strong><br />

completely depends <strong>on</strong> irrigati<strong>on</strong>. For comparis<strong>on</strong>,<br />

two testing sites (denoted as site 1 and<br />

site 2 ) were chosen for each of the two test<br />

ganals. Site 1 is at a saline soil z<strong>on</strong>e and<br />

site 2 is at a n<strong>on</strong>-saline soil z<strong>on</strong>e.<br />

1071<br />

PHYSICAL AND MECHANICAL PROPERTIES OF SALINE<br />

SOILS<br />

Influence of i<strong>on</strong>s <strong>on</strong> soil properties<br />

The existence of i<strong>on</strong>s changes the thickness of<br />

the diffuse layer around soil particles,thereby<br />

influencingth-eplaatic and the liquid lfmits of<br />

soils. Experiments show that the plasticity<br />

index of the soil tested decreases with increasing<br />

salinity, except for the alkaline<br />

soils, as is shown in Fig.1. The soil properties<br />

%re greatly changed when the salinity Sd is<br />

greater than 2%. The physical and mechanical<br />

properties mainly depend <strong>on</strong> the salinity and<br />

the salt type. For saline soils, liquefacti<strong>on</strong><br />

will occur and thua it8 shear strength will<br />

tend towards zero, even if it5 water c<strong>on</strong>tent is<br />

relatively low.<br />

Behavior of swelling and crvstallized exDansi<strong>on</strong><br />

of saline soils<br />

The swelling and crystallized expansi<strong>on</strong> tests<br />

were c<strong>on</strong>ducted <strong>on</strong> the aali:e soil samples with<br />

a dry density of 1.00 glcm . The results show<br />

that the amount of swelling is smaller for the<br />

chlorate and sulphate soils after soaking in<br />

water, but much greater for the carb<strong>on</strong>ate soils.<br />

The amount oE swellin in the carb<strong>on</strong>ate soil<br />

may reach to 2.5-11.8$ (see Fig.1).<br />

The crystallized expansi<strong>on</strong> is defined as the<br />

volumetric expansi<strong>on</strong> of crystallizati<strong>on</strong> caused<br />

by the temperature decreasing and c<strong>on</strong>centrati<strong>on</strong><br />

of the remaining soluti<strong>on</strong>. The formati<strong>on</strong> and<br />

the growth of Na2SOh-lOH20 sfter crystallizati<strong>on</strong><br />

of the soluti<strong>on</strong> with sodium sulphate results in<br />

volumetric expansi<strong>on</strong> and damage to the soil texture.<br />

"The amount of crystallized expansi<strong>on</strong> for<br />

the sulphate soil is large, with a maximum of<br />

28%. It increases with increasing sulphate c<strong>on</strong>tent<br />

and decreases with increases in dry density.

I8<br />

Shear strenath of saline soils after soakinn in<br />

- water<br />

The salts in the saline soils are dissolved<br />

after soaking in water, which results in an increase<br />

in the pore size, and a loss of cohesi<strong>on</strong><br />

between soil particles and thus the decrease in<br />

the shear strength. The measured values of<br />

cohesi<strong>on</strong>, C and the angle of interparticle fricti<strong>on</strong>,<br />

4 for the saturated silty loam with var;<br />

ious salinities and a dry density of 1.4 g/cm<br />

were shown in Table I.<br />

Fig.1<br />

Relati<strong>on</strong>s between Salinity,<br />

Liquid Limit and Plastic Limit<br />

1 - liquid -limit;<br />

2 - plastic limit.<br />

For the sulphate soil with a salinity of S%,<br />

the amount of crystallized expansi<strong>on</strong> is 28.8<br />

and 8.5%, forla dry density, Pd, equal to 1.40<br />

and 1.60 g/cm , respectively. The soils are<br />

loosened after being subjected several times to<br />

the crystallized expansi<strong>on</strong>. The experiments<br />

show that the amount of swelling and crystallizati<strong>on</strong><br />

expansi<strong>on</strong> ate changed slightly when<br />

Sd is greater than.Z%,xnd:tkay,are greatly increased<br />

when Sd is less than 2% (see Figs.2 and<br />

3).<br />

I<br />

To sum up, different kinds of salts play dif- ,<br />

ferent roles in saline soils. For the chlorate<br />

soil, salt crystallizati<strong>on</strong> plays the role of<br />

cementing soil particles, thus increasing the<br />

shear strength. After soaking, the salts are<br />

dissolved and the strength is decreased. With<br />

an increase in the chlorate salinity, the plasticity<br />

is decreased and moisture retenti<strong>on</strong> is<br />

increased. If the soil is in a saturated c<strong>on</strong>diti<strong>on</strong><br />

for a l<strong>on</strong>g time, the phenomen<strong>on</strong> of liquefacti<strong>on</strong><br />

may readily take place.<br />

For the sulphate soil, salt crystallizati<strong>on</strong> will<br />

cause expansi<strong>on</strong> and loosening of the soil, and<br />

thus decrease the soil strength after drying.<br />

After soaking, the salts are dissolved and the<br />

strength is decreased. Only at a water c<strong>on</strong>tent<br />

close to the plastic limit the soil strength is<br />

higher. 'The solubility of the sulphate changes<br />

greatly with temperature. In Xinjiang regi<strong>on</strong>,<br />

the climate is dry and the temperature difference<br />

is great during day and night, providing a<br />

good c<strong>on</strong>diti<strong>on</strong> for crystallized expansi<strong>on</strong> of<br />

the sulphate. Furthermore, the sulphate soil<br />

has a lowek solubility. All of the factors<br />

menti<strong>on</strong>ed above are extremely harmful to engineering<br />

structures. Therefore, the crystallized<br />

expansi<strong>on</strong> of the saline soils with higher<br />

salinity is a very important factor causing<br />

damage to engineering structures in severe cold<br />

and arid regi<strong>on</strong>s.<br />

WATER AND SALT REDISTRIBUTION AFTER DIVERSION ,<br />

IN CANALS<br />

The kep to soluble salt migrati<strong>on</strong> in soils is<br />

the existence of water. The diversi<strong>on</strong> and<br />

drainage of water from the canals, freezing and<br />

evaporati<strong>on</strong> of soils cause salts to be aggregated<br />

and leached periodically in the soils.<br />

Water redistributi<strong>on</strong><br />

With the diversi<strong>on</strong> and interrupti<strong>on</strong> of water<br />

supply and freeze-thaw acti<strong>on</strong>, water in the<br />

soils is redistributed.<br />

Salinity. SD",,<br />

Fig.2 Curves for Fig.3 Curves for<br />

Crystallizati<strong>on</strong><br />

Swelling after<br />

Expansi<strong>on</strong><br />

Soaking<br />

After diversi<strong>on</strong> from the canals, the soils below<br />

the infiltrati<strong>on</strong> line are in a saturated and<br />

leached z<strong>on</strong>e. After cutting off water from the<br />

canals, the water c<strong>on</strong>tent at the surface of the<br />

canal is lowered by evaporati<strong>on</strong> and is increased<br />

beneath the ground surface. It has its highest<br />

value at a depth of 50-60 cm (with the mean<br />

value of 20-3OX). During freezing, water moves<br />

upwards, resulting in a maximum water c<strong>on</strong>tent<br />

of 40-532 at a depth of 30-60 cm, which is in<br />

good agreement with the depth of the maximum<br />

frost heave ratio observed,<br />

1072

TABLE I<br />

The Measured Values of C and 4 for the Soils<br />

Tested with Various Salinities<br />

Salt N<strong>on</strong>e NaCl NaHC03 Na2SO4<br />

Salinity<br />

x<br />

2 5 8 2 5 8 2 5 '8<br />

C, N/cm' 0.04 0 0 0 0.49 0 0 0.98 1.37 0.784<br />

4, degree 11.3 5.7 5.0 4.3 7.8 2.9 2.7 4.3 4.0 4.0<br />

Fig.4 shows curves of water c<strong>on</strong>tent vs depth site 1 are leached, with a salinity much less<br />

before and after freezing at site 1 of both No. than 0.2%. These soils would be c<strong>on</strong>sidered<br />

148 and No.150 €arms, respectively, in 1985-86. s<strong>on</strong>-saline. The salinity at the inside slope<br />

of the canals for both sites 1 and 2 are almost<br />

the same, which implies that they have a similar<br />

freezing behavior.<br />

i<br />

Wawr coeitn~%<br />

FREEZING BEHAVIOR OF SALINE SOILS<br />

Freezing behavior of soluti<strong>on</strong>s<br />

The solubility of various kinds of salts is<br />

shown in Table 11. From Table I1 it can be<br />

seen that the iolubility of NaCl is very high<br />

but is lowered slightly with a decrease in tem-<br />

90<br />

perature. The solubility of NazSO4 is relatively<br />

low, but lowers quickly with decreases<br />

in temperature.<br />

12<br />

I<br />

I<br />

TABLE I1<br />

Fig.4 Changes of the Water C<strong>on</strong>tent<br />

The Solubility of the Salts<br />

before and'after Freezing at Site 1<br />

of Both No.148 Farm (a) and No.150<br />

Solubility (X) at different temperatures ("C)<br />

Farm (b)<br />

0 10 20<br />

Salt redistributi<strong>on</strong><br />

With the water in canals permeating and leaching. NaCl 35.7 35.8 36<br />

the salts are dissolved. Some salts become aggregated<br />

at the outside of the canal and others Na2S04<br />

5 9.0 19.4<br />

are transparted to a depth of 50-60 cm. The sat- NaHC03 6.9 8.2 9.6<br />

urated part of the soil below the infiltrati<strong>on</strong><br />

line is the salt leaching z<strong>on</strong>e. The salinity<br />

in this z<strong>on</strong>e is lowered to 0.03-0.17%, which is<br />

11'70-1/100 of the value at the outside slope<br />

(or the surface of the canal). The distributi<strong>on</strong> With increases in c<strong>on</strong>centrati<strong>on</strong> of the soluof<br />

the salinity at the outside slope is triangu- ti<strong>on</strong>s, the freezing point is decreaeed, espelar<br />

with the values higher at the top and lower cially for the chlorate soluti<strong>on</strong>. At low temat<br />

the bottom. After freezing, the salt dis- perature , the solubility of the sulphate solutributi<strong>on</strong><br />

at the inside slope of the canal is ti<strong>on</strong> is very low (5.00%). Even if its initial<br />

made slightly mors uniform by water redistribu- c<strong>on</strong>centrati<strong>on</strong> were higher, the soluti<strong>on</strong> would<br />

ti<strong>on</strong>, and there is a tendency for salt to mig- be oversaturated and the salts would precipirate<br />

toward the freezing fr<strong>on</strong>t (see Fig.5).<br />

tate out with decreasing temperature, so that<br />

the freezing point depressi<strong>on</strong> of the sulphate<br />

In test site 2, the initial salinity is lower, soluti<strong>on</strong> is relatively small. Table 111 shows<br />

but is higher at site 1. With water flow and the freezing point depressi<strong>on</strong> and,the frost<br />

leaching acti<strong>on</strong>s, almost all of the salts In<br />

heaving ratio for the different types of the<br />

the soils at the inside slope of the canals at soluti<strong>on</strong>s.<br />

1073

~~ ~~ .<br />

TABLE 111<br />

The Freezing Point Depressi<strong>on</strong> and Frost Heaving Ratiof Soluti<strong>on</strong>s<br />

soluti<strong>on</strong> C<strong>on</strong>centrati<strong>on</strong> Freezing point Frost heaving<br />

(X) depressi<strong>on</strong> ("C) ratio (AV/V)<br />

NaCl 5<br />

8<br />

.<br />

2 -1 .o 0.071<br />

22.4 -21.2<br />

-3.0 0.051<br />

-5.4 0.038<br />

2 -1 .o<br />

Na2S04 5 -2.2 0.083<br />

8 -2.6 0.073<br />

- .-<br />

Pure<br />

0 water<br />

0 0.09<br />

Salinity%.<br />

- -7<br />

30<br />

' \ \<br />

\ J<br />

120'<br />

Fig.5 Salinity vs Depth at Site 1 of Both<br />

N0.148 Farm (a) and No.150 Farm (b)<br />

Frost heavin.n tests <strong>on</strong> saline soils<br />

The frost heave tests were c<strong>on</strong>ducted in a steel<br />

c<strong>on</strong>tainer ( 40x40~50 cm') in which there were<br />

four tapered plastic tubes 100 cm in diameter<br />

at the top, 130 cm in height and 1040 cm' in<br />

volume. Insulati<strong>on</strong> materials were wrapped around<br />

the outside of the c<strong>on</strong>tainer to ensure unidirecti<strong>on</strong>al<br />

freezing. Water is supplied from the<br />

bottom of the sample during freezing and the<br />

sol1 is frozen under a natural frost penetrati<strong>on</strong><br />

rate induced by the temperature c<strong>on</strong>troller.<br />

The ambient temperature is in the range of from<br />

-10 toO-15DC and th: dry density is in the range<br />

of 1.2 to 1.40 g/cm . The samples are the saturated<br />

silty clay.<br />

Fig.6 shows the changes of frost heave with<br />

elapsed time Tor the soils with NaCl and NazS04.<br />

The results show that: (1) The amount of frost<br />

heaving decreases with the increase in the<br />

salinity. '(2) The amount of frost heaving for<br />

the sulphate soil is greater than that €or the<br />

chlorate soil when the salinity ie the same.<br />

(3) Even though the air temperature drops down<br />

to -20°C and the soil temperature down to -9'C,<br />

the saline soils wlth 5% chlorate c<strong>on</strong>tent are<br />

still unfrozen and no water migrati<strong>on</strong> occurs.<br />

The water c<strong>on</strong>tent before and after freezing is<br />

30 and 40-50Z for the n<strong>on</strong>-saline soils and is<br />

30 and 20-30Z for the chlorate soils with the<br />

salinity of 5Z respectively. (4) Frost heave<br />

is relatively low when the temperature is very<br />

cold and the freezing index is high. (5) No<br />

frost heave was observed for the soils with the<br />

NaCl salinity of 5% and 8X. In the tests the<br />

soil temperatures are as follows: 0 to -1OC for<br />

the n<strong>on</strong>-saline soil, -1 to -2OC for the sulphate<br />

soil and -6 to -9'C for the chlorate soil.<br />

1074

P 0, 2<br />

Elapsed time, days<br />

4 6<br />

I<br />

Freezinn Doint depressi<strong>on</strong> in saline soils<br />

The freezing point depressi<strong>on</strong> in the saline<br />

soils were determined with thermocouples. The<br />

test results are shown in Figs. 7 and 8.<br />

It is seen from Figs.7 and 8 that the freezing<br />

point depressi<strong>on</strong> for the sulphate soil is lower<br />

than that for the chlorate soil. If the salinity<br />

is the same, the freezing point depressi<strong>on</strong><br />

will be higher when the water c<strong>on</strong>tent is higher<br />

because of the decrease in c<strong>on</strong>centrati<strong>on</strong>.There<br />

is no obvious inflecti<strong>on</strong> point <strong>on</strong> the curve of<br />

the soil temperature VS. the elapsed time for<br />

the saline soils with the higher salinity. The<br />

test results show that the freezing point depressi<strong>on</strong><br />

is closely related to the c<strong>on</strong>centrati<strong>on</strong><br />

of the salts in pore water. The relati<strong>on</strong> between<br />

freezing point depressi<strong>on</strong> and salt c<strong>on</strong>centrati<strong>on</strong><br />

for saline loam is shown in Table IV.<br />

Salinity.%<br />

2 4 6 8<br />

0 , 1 , ( , , , ( , I<br />

Fig.7 The Freezing Point Depressi<strong>on</strong><br />

of the Saturated Saline soils<br />

Water c<strong>on</strong>tent.%<br />

Fig.8 The Freezing Point Depressi<strong>on</strong> of<br />

the Saline Soils at Different Water<br />

C<strong>on</strong>tents<br />

The observed values of the salinity and freezing<br />

point depressi<strong>on</strong> €or the two test canals are<br />

shown in Table V.<br />

From Table V it can be seen that whether the<br />

canal is <strong>on</strong> the saline soils or not, almost all<br />

of the salts in the inside slope have been<br />

leached, and the salinity is in the range 0.04<br />

to 0.09% with the mean value of 0.06%. The c<strong>on</strong>centrati<strong>on</strong><br />

of the pore water R is in the range<br />

0.27 to 0.24% when W=27-30%. By c<strong>on</strong>trast to<br />

Table IV, the freezing point depressi<strong>on</strong> is in<br />

the range 0 to -0.2'C. ThereEore, it is c<strong>on</strong>cluded<br />

that the freezing point depressi<strong>on</strong> of the<br />

soils at the inside elopes has no obvious effect<br />

whether the canal is c<strong>on</strong>structed in saline soil<br />

or not, because of salt leaching. In this case,<br />

frost heave is mainly influenced by the freezing<br />

rate and the water c<strong>on</strong>t-ent before freezing.<br />

1075

TABLE IV<br />

The Freezing Point Depressi<strong>on</strong> of the Saline Loam for<br />

Various Salt C<strong>on</strong>centrati<strong>on</strong>s<br />

Salt c<strong>on</strong>centrati<strong>on</strong> in<br />

pore water (X)<br />

0.5 1 3 5<br />

Freezing point<br />

depressi<strong>on</strong> ("C)<br />

-0.2 -1.5 -1.4 -2.5<br />

TABLE V<br />

Observed Values of Freezing Point and Salinity for the Two Test Canals<br />

Test site<br />

Water<br />

Depth c<strong>on</strong>tent Salinity freezing<br />

( cm> (X> (X) fr<strong>on</strong>t<br />

Measured<br />

Inside Site 1 30-60 23.8 0.070 -0.013<br />

The first slope<br />

branch Site 2 30-60 24.9 0.056 -0.05<br />

canal of<br />

No*148<br />

farm<br />

Outside<br />

Site 1 0-30 24.7 2.23 -1.89<br />

Site 2 0-30 21.7 3.39<br />

Inside<br />

Site 1 30-60 23.1 0.063 -0.02<br />

The third slope<br />

branch Site 2 30-60 23.0 0.084 -0.11<br />

canal, 150<br />

of No.150<br />

farm<br />

Site 1<br />

Outside<br />

0-30 14.3 2.10 -4.90<br />

Site 2 0-30 23.3 0.410 -0.02<br />

INFLUENCE OF FREEZING RATE ON FROST HEAVE<br />

According to the newest theory (Miller, 1972;<br />

K<strong>on</strong>rad and Morgenstern, 1980) the ice segregati<strong>on</strong><br />

temperature is slightly Lower than O°C<br />

which is the freezing point of the pure water.<br />

When the soil temperature is much lower than<br />

the freezing point depressi<strong>on</strong> and the freezing<br />

rate is high, water will not be supplied in<br />

time so that the amount of frost heave will be<br />

lower. The amount of frost heave can reach a<br />

maximum <strong>on</strong>ly for the following c<strong>on</strong>diti0ns:i.e.<br />

the soil temperature is lower than the freezing<br />

point and is maintained for a l<strong>on</strong>g period of<br />

time, and the freezing rate is appropriate for<br />

the available water supply.<br />

The observed results of frost heave ratio and<br />

freezing rate in the farms of No.148. 150 and<br />

121 were plotted <strong>on</strong> Fig.9, showing that the<br />

heaving ratio is greatly influenced by the<br />

freezing rate. The relati<strong>on</strong>ship between them<br />

can be well described by a hyperbolic functi<strong>on</strong>.<br />

The heave ratio was suddenly lowered, when the<br />

freezing rate was greater than about 1.5 cm/day<br />

\<br />

151 I b a I<br />

0 L L<br />

1 2 3<br />

Freezing rate, crnlday<br />

Fig.9 F1,ost Heave Ratio in the Primary Heaving<br />

Z<strong>on</strong>e vs keening rate in .N0.140 farm (cur-re a:)<br />

and No.150 and 121 farm (curve b)<br />

1076

CONCLUSIONS<br />

(i)<br />

The freezing of saline soils is str<strong>on</strong>gly<br />

related to the c<strong>on</strong>centrati<strong>on</strong> of salt in<br />

pore water. The higher the c<strong>on</strong>centrati<strong>on</strong>,<br />

the lower both the freezing point<br />

depressi<strong>on</strong> and the frost heave ratio.<br />

The freezing point depressi<strong>on</strong> and the<br />

heave ratio for sulphate soil are higher<br />

than that for chlorate soil when the<br />

c<strong>on</strong>centrati<strong>on</strong> is the same.<br />

(ii) The amount of frost heave depends <strong>on</strong> the<br />

water c<strong>on</strong>tent before freezing. freezing<br />

rate, salinity, soil temperature, groundwater<br />

table and soil properties.<br />

(iii) Because of the higher water maintenance<br />

capability, lower soil density, the<br />

solubility and the lower plasticity of<br />

saline soils, mechanical properties of<br />

saline soils are worsened after soaking<br />

in water. The soil changes into a slurry<br />

after frost-thaw cycles, resulting in<br />

sloughing of the canal liriing. Therefore,<br />

the instability of the base saline soils<br />

of a canal is the dominant factor in<br />

canal damage.<br />

(iv) Because the original salinity is high,<br />

the salts in the saturated z<strong>on</strong>e of the<br />

canal embankment are leached after the<br />

cana.1 comes into operati<strong>on</strong>, and the<br />

pores in the soils ere enlarged, leading<br />

to an increase in frost heave at the<br />

inside slope of the canal and accelerating<br />

canal damage. Another reas<strong>on</strong> for<br />

canal damage is the crystallizati<strong>on</strong><br />

expansi<strong>on</strong> of saline soils in the salt<br />

enriched z<strong>on</strong>e at some depth beneath the<br />

canal surface.<br />

(VI If the saline soils are kept stable and<br />

the salts In soils are not leached,<br />

water migrati<strong>on</strong> towards the freezing<br />

fr<strong>on</strong>t and froat heave can be completely<br />

eliminated because of the presence of<br />

the univalent cati<strong>on</strong> chlorate (NaC1,<br />

KCl), which maintains a high salinity<br />

in the base soil in the range of 3-5X.<br />

ACKNOWLEDGEMENTS<br />

The author is grateful to his colleagues,Messrs<br />

S<strong>on</strong>g Jun, Liu Xinping and Li Hao for their participati<strong>on</strong><br />

i n this investigati<strong>on</strong>.<br />

REFERENCES<br />

Miller, R.D. (1972). ,Freezing and heaving of<br />

saturated and unsaturated soils. Highway<br />

<strong>Research</strong> Record, No.393, pp.1-11.<br />

K<strong>on</strong>rad. J.M. and N.R. Morgenstern,(l980). The<br />

segregati<strong>on</strong> potential of a freezing soil.<br />

Can. Geotech. J., V.18, pp. 482-491.<br />

1077

MECHANICAL PROPERTIES OF FROZEN SALINE CLAYS<br />

T. Furuberg' and A.-L. Berggren2<br />

ISINTEF, Divisi<strong>on</strong> of Geotechnical Engineering, Tr<strong>on</strong>dheim, Norway<br />

2Geofrost AB, Oslo, Norway<br />

ABSTRACT A test series which we performed <strong>on</strong> a very saline permafrost clay from Svalbard drew<br />

our attenti<strong>on</strong> to the nexus between pore water salinity and the mechanical properties of froz<br />

line soil. To further investigate the effect of pore water salinity we have tested three frozen<br />

clays with pore water salinity -0 of g/l, 3 g/1 and 33 g/L. Unremoulded samples are used to keep the<br />

natural structure of the clays. We have performed both strength and creep <strong>on</strong> the tests three clays.<br />

Unfrozen water c<strong>on</strong>tent as functi<strong>on</strong> of temperature is also determined. For the clay with 33 g/1 salinity<br />

tests at -3, -5. -10 and -2OOC are reported, For the other clays <strong>on</strong>ly tests -5OC at are regortea,<br />

Prom the test results is it seen that increasing gore water salinity leads to increased unfro-<br />

Zen water c<strong>on</strong>tent and creep strains and to decreased creep and compressive strength. The i<br />

of salinity <strong>on</strong> mechanical properties of frozen soil is best accounted for through the unfrozen<br />

c<strong>on</strong>tent.<br />

TNTRODUCTTON<br />

cores. The samples were frozen, with no access<br />

to water, in a freezer at -26OC. <strong>Permafrost</strong> clay<br />

Our interest in frozen saline soils was initi- was cored with an 3" auger. The samples were<br />

ated by a test series which we performed <strong>on</strong> trimmed <strong>on</strong> a lathe to a height to diameter ratio<br />

saline permafrost clay from Svea, Svalbard. The of 2. For triaxial tests the samples were clad<br />

Svea clay has a gore water salinity 50-60 of g/1 in a rubber membrane sealed to top and bottom<br />

and we discovered that its l<strong>on</strong>g term strength pieces by O-ring seals. For uniaxial tests the<br />

was very low compared to other frozen clays. samples were given a thin coating of kerosene to<br />

Saline marine clays are comm<strong>on</strong> in many areas of keep the ice from sublimating.<br />

Norway, thus a knowledge of the properties of<br />

frozen saline soil is needed for ground freezing The strength tests were performed a Ge<strong>on</strong>or in<br />

projects. Relatively few tests <strong>on</strong> frozen saline press with 50 kN capacity. The most comm<strong>on</strong>ly<br />

soils axe reported in the Literature, hence we used strain rate was 1% min-l. The creep tests<br />

started a test aeries <strong>on</strong> artifically frozen were performed in a triaxial creep apparatus.<br />

clays with different gore water salinities. We The equipment is described by Berggren (1985).<br />

tested three clays, Risvollan, Stjdrdal and Radial stress is applied by pressurizing the<br />

Eberg clay, with gore water salinity of -0 g/1, cell fluid. C<strong>on</strong>stant axial stress is produced by<br />

3 g/l and 33 g/l, respectively. When testing an air pressure actuator with c<strong>on</strong>stant air pr<br />

soils <strong>on</strong>e may either use remoulded or undistur- suxe. The air pressure is regulated manually to<br />

bed soil samples. Remoulded soil samples are of correct Tor sample cross-secti<strong>on</strong> increase during<br />

uniform quality and <strong>on</strong>e may vary a single para- the test. All mechanical tests were performed in<br />

meter like salinity. whilst keeping the others a cold room.<br />

c<strong>on</strong>stant. The natural structure of the soil is,<br />

however, disturbed; we therefore chose to use Unfrozen water c<strong>on</strong>tent is determined by two<br />

unremoulded sanwles. The test series will thus methoas, both in an adiabatic calorimeter by and<br />

c<strong>on</strong>tribute to a database c<strong>on</strong>taining results from the nuclear magnetic res<strong>on</strong>ance method. These<br />

tests <strong>on</strong> some typical Norwegian clays. By compa- tests were performed at the Divisi<strong>on</strong> of Refrigering<br />

the results from tests <strong>on</strong> clays with diffe- rati<strong>on</strong> Engineering, The Norwegian Institute of<br />

rent salinities, we hoped to determine the in- Technology, and at the US Army's Cold Regi<strong>on</strong>s<br />

fiuence of pore water salinity <strong>on</strong> the mechanical <strong>Research</strong> and Engineering Laboratories, respectiproperties<br />

of frozen clay.<br />

vely.<br />

We performed both strength and creep tests, Unfrozen<br />

pore water cantent as a functi<strong>on</strong> of tem- MATERIAL DATA<br />

gerature was also determined. A selecti<strong>on</strong> of<br />

the tests performed are presented in this paper, The Svea clay is a permafrost clay of marine<br />

For Stjdrdal clay results from tests at diffe- origin. Its pore water is almost twice as saline<br />

rent temperatures are given. For the other clays as seawater and the clay holds thick vertical<br />

<strong>on</strong>ly tests performed -5OC at are presented. seams of fresh ice. The clay is dark brown with<br />

-a relatively high c<strong>on</strong>tent of organic matter.<br />

Risvollan-, Eberg- and Stjdrdal clay are marin<br />

TEST PROCEDURE<br />

clays with varying salinity.<br />

Astifically frozen samples were cut from 54 m<br />

1078<br />

A summary of material data is given in Table I

I_<br />

I_<br />

As undisturbed samples are used, a range rather<br />

than <strong>on</strong>e single value is given for some of the<br />

parameters. The data include results from the<br />

entire test series, not <strong>on</strong>ly the tests presented<br />

herein. For Svea clay the data are based <strong>on</strong> the<br />

soil excluding thick ice lenses, total values<br />

are given in parenthesis.<br />

TABLE r Nateriul Datu for the Tested Clam<br />

C<strong>on</strong>tents I untrozen strengths I<br />

I<br />

I I I I I I<br />

w - water c<strong>on</strong>tent,

TABLE<br />

BKR55<br />

BKR57<br />

BKR58<br />

BKR51C<br />

v Data for Creep Tests <strong>on</strong> Eberg Clay.<br />

Depth Clal Salt<br />

(m) (X) ( 8/1)<br />

---<br />

2.98<br />

2.99<br />

2.99<br />

3.19<br />

3.42<br />

4.42<br />

4.18<br />

58<br />

66<br />

66<br />

52<br />

69<br />

72<br />

83<br />

2.2<br />

1.8<br />

1.9<br />

*<br />

2.9<br />

3.9<br />

-<br />

5.3<br />

5.3<br />

5.2<br />

5.2<br />

5.2<br />

5.2<br />

5.5<br />

-<br />

TWLE VIDcZa for Creep Teszs <strong>on</strong> Risvollan Clay.<br />

-<br />

lepth<br />

-<br />

e<br />

(A)<br />

(‘C)<br />

- -<br />

T5 1A 3.15 - -0 40.7 1477 0 4.9<br />

3.25 35.8 -0 44.2 1938 0 5.2<br />

T51D 3.40 57.1 -0 34.4 2462 0 5.3<br />

T51E 3.50 15.2 -0 31.4 2557 o 5.3<br />

3.45 40.8 -0 35.4 2563 797 4.7<br />

3.55 19.6 -0 l2.8 3120 797 4.5<br />

93: 3.65 31.7 -0 38.7 2990 197 -<br />

T53D 4.15 29.9 -0 36.6 2993 797 5.2<br />

-<br />

-<br />

’i N M<br />

c<br />

.d<br />

0.3<br />

E 0.2<br />

U<br />

m<br />

!-I<br />

m<br />

.A<br />

x 0.1<br />

m<br />

0. LOOO. 2000. 9000. 4000. 9000. 6001<br />

0.<br />

0.4 - -E<br />

2500 e 5000. 7500,<br />

E<br />

.d<br />

m<br />

L<br />

cl<br />

v1<br />

0.2<br />

m<br />

-rl<br />

x<br />

rn<br />

m<br />

a<br />

L<br />

KRYPQC<br />

KRYP7C<br />

I- 0. ,<br />

0. 500. 1000.<br />

II<br />

0. i00. 200. 300. 400. 500. 600.<br />

0. 500. i000. 1500. 2000. 2500. 3000.<br />

Time (min. 1<br />

1080<br />

c<br />

4<br />

tu<br />

Y<br />

L<br />

VI<br />

0.1<br />

,+ 0.05<br />

m<br />

.A<br />

X<br />

rn<br />

0. 5000. ioooo. 19000. 20000<br />

1E<br />

a2<br />

1<br />

L<br />

I- 0.<br />

0. 50000 * 10000(<br />

Time (min.1

0.15- -H<br />

II<br />

0.05<br />

-jM<br />

I I I I<br />

0.1<br />

0.05<br />

SNOK1 0<br />

0. 1000. 2000. 3000.<br />

0. 1000. 2000. 3000. 4000.<br />

0.015<br />

0. 5000. 10000. isooo. 20000<br />

0. io000 . 20000. 30000. 0. 500. 1000. 1500.<br />

2000 *<br />

0. is<br />

.r(<br />

C<br />

m 0.1<br />

L<br />

4J<br />

UI<br />

rl<br />

m<br />

-c 0.05<br />

m<br />

P)<br />

3<br />

.rl<br />

c<br />

0.<br />

0 .os<br />

m<br />

L<br />

4J<br />

0.025<br />

c<br />

m<br />

.C<br />

X<br />

0. 800. 1000. 0.<br />

"L<br />

Br(p58<br />

I 4'<br />

0<br />

1 0<br />

t 0.<br />

0. 2500. 5000. 7500. 0. 100. 200. 300. 400. 500 I<br />

Time hin.1<br />

Time (min.)<br />

1081

+ 0.<br />

0.2<br />

jR<br />

0.15 1<br />

I W<br />

0.05-<br />

0,4<br />

0. ,",,,,,, , ( ) , ,,,,<br />

0. 100. 200. 300. 400. 500. 600.<br />

S<br />

0. iooo. 2000. 3000. 4000.<br />

Time (min .I<br />

m<br />

3<br />

L<br />

Unfrozen water c<strong>on</strong>tent as functi<strong>on</strong> of temperature<br />

is given in Figure 2,<br />

0.2<br />

'C<br />

.rl<br />

L<br />

m<br />

Y<br />

(0 0.1<br />

e<br />

m<br />

."<br />

X<br />

m<br />

W<br />

1<br />

L<br />

+ 0.<br />

0. 500. l000. isoo. 2000.<br />

0.3<br />

C<br />

.r( 0.2<br />

L<br />

Y<br />

tn<br />

rl<br />

m<br />

.- 0.1<br />

X<br />

m<br />

ru<br />

3<br />

L<br />

+ 0.<br />

0.3<br />

c<br />

."<br />

m 0.2<br />

L<br />

c)<br />

u1<br />

rl<br />

m<br />

" 0.1<br />

X<br />

IU<br />

m<br />

3<br />

0.<br />

0. 1000. 2000. 3000. 4000. 5000. 6000.<br />

Fig. 2<br />

Unfrozen Water C<strong>on</strong>tent as Functi<strong>on</strong> of<br />

Temperature. After Berggren (1983)<br />

STRENGTH AND DEFORMATION PROPERTIES<br />

The teats are interpreted according to Berggren's<br />

model, Berggren (1983). Deformati<strong>on</strong> is computed<br />

from the strain equati<strong>on</strong>s (1) , (2) and (3) ,<br />

Total strain:<br />

Strain in the primary creep period:<br />

1 0 i<br />

E = -1-1 In , 1 = to < t s t (2)<br />

'f %<br />

P<br />

Sec<strong>on</strong>dary creep strain:<br />

1082

TABLE VI1 Creep Parameters for Use in the Berg-<br />

E = strain In primary creep period<br />

gren Model. Parantes Indicates Un-<br />

P<br />

certain Values. After Berggren (1983)<br />

Es = strain in sec<strong>on</strong>dary creep period<br />

tp primary creep period<br />

Clay i<br />

t = t extrapolated to a fictious failure<br />

I :E)<br />

Pf p<br />

j = exp<strong>on</strong>ent<br />

3.8<br />

0, = temperature dependent reference stress Eberg<br />

(4.1)<br />

rf = the creep number, r. extrapolated to a<br />

Risvollan 7.1<br />

1.5<br />

fictitious failure<br />

i = exp<strong>on</strong>ent<br />

In figure 3 creep strength at -5OC is plotted<br />

to = 1 hour, introduced to avoid initial calcu- against design period.<br />

lati<strong>on</strong> problems.<br />

The temperature dependent reference stress u<br />

may be determined from compressi<strong>on</strong> tests !he at<br />

correct temperature or from unfrozen water c<strong>on</strong>tent<br />

tests by Equati<strong>on</strong> (4).<br />

Temperature dependent reference stress:<br />

"s<br />

ae = 0 (-)<br />

"u<br />

(4)<br />

ou = o8 extrapolated to a fictitious thawed<br />

state when Wu = Ws<br />

u = exp<strong>on</strong>ent<br />

WB = moisture c<strong>on</strong>tent at 100% saturati<strong>on</strong><br />

W, = unfrozen water c<strong>on</strong>tent.<br />

If the sec<strong>on</strong>dary creep stage develops, it will<br />

just be a matter of time before failure occurs.<br />

Therefore creep strength is taken to be the<br />

upper stress limit for primary creep.<br />

Creep strength:<br />

t (l/j)<br />

=<br />

OL a e [ tp S I (5)<br />

Fig. 3<br />

Creep strength aL,versus design period.<br />

Temperature -5°C<br />

The four clays accumulate different creep<br />

strains during design periods of equal length.<br />

Creep strains for a design period. or a primary<br />

creep period of 12 m<strong>on</strong>ths at -5'C, are given in<br />

Table VIII.<br />

TABLE VI11 Creep Strains Accumulated During a<br />

12 M<strong>on</strong>ths Primary Creep Period.<br />

Temperature -5°C<br />

The traditi<strong>on</strong>al way of presenting creep tests <strong>on</strong> clay Stjdrdal Eberg RisvoLlan Svea<br />

frozen soil is by plotting true strain versus<br />

time. True strain, E = Ah/h, is therefore plot- Primary<br />

ted in Fig. 1, even if the Berggren model is<br />

creep 0.9 0.03 -0 3.3<br />

based <strong>on</strong> engineering strain, E = Ph/ho. The<br />

strain (%)<br />

error made by using true strain curves instead<br />

of engineering strain curves, for determining Salinity 33 3 -0 50-60,SOil<br />

parameters for the Berggren model, is relatively (g/l)<br />

34, total<br />

small. The parameters given in Table VI1 are,<br />

however, determined from engineering strain<br />

plots, The parameters are also based <strong>on</strong> all<br />

tests performed, not <strong>on</strong>ly the selected number of COMMENTS<br />

tests presented in this paper.<br />

In the Berggren model dependency of amount of<br />

unfrozen water is exchanged for the temperature<br />

dependency. This is d<strong>on</strong>e because the water phase<br />

is believed to govern the l<strong>on</strong>g-term behaviour of<br />

the frozen soil whilst the ice governs the shortterm<br />

behaviour of the soil. No simple mathematical<br />

formulati<strong>on</strong> of the unfrozen water c<strong>on</strong>tenttemperature<br />

curve is found. Fox n<strong>on</strong>saline soils<br />

a linear logarithmic formulati<strong>on</strong> might be used,<br />

but this will not apply if the soil is highly<br />

saline. Results from the unfrozen water c<strong>on</strong>tent<br />

1083

tests should therefore be used directly when<br />

determining the temperature dependent reference<br />

stress, oe.<br />

A3 seen from Fig. 2, the amount of unfrozen<br />

water increases with increasing salinity. The<br />

most saline clays were therefore expected be to strains. As for creep strength, the influence of<br />

the weakest clays. As seen from Table 11, this salinity <strong>on</strong> creep strain is accounted for<br />

is not quite true. The Sves clay has c<strong>on</strong>sider- through the unfrozen water c<strong>on</strong>tent.<br />

ably higher compressi<strong>on</strong> strength than the slightly<br />

less saline Stjdrdal clay, We believe that<br />

this is due to the vertical fresh ice seams in CONCLUSIONS<br />

the clay, acting as reinforcement when the clay<br />

is subjected to rapid loading. From Fig. 3 it is Creep strains and unfrozen water c<strong>on</strong>tent inseen<br />

that the creep strength of Svea clay is far crease with increasing salinity of the clay,<br />

less than the creep strength of Stjdrdal clay. whereas creep and compressive strqngth decrease<br />

The difference between the creep strengths of with increasing salinity. The relative strength<br />

the two clays are larger than <strong>on</strong>e would expect reducti<strong>on</strong> as salinity,increases is not equal for<br />

rrom the difference in total salinity of the craep and ComDreSsi<strong>on</strong>. This makes it difficult<br />

clays. In the Svea clay, however, the salt is to quantify t& influence o'f salinity <strong>on</strong> frozen<br />

c<strong>on</strong>centrated in the pores in soil, the 50-60 clay strength directly,. our In opini<strong>on</strong> the ing/l.<br />

whilst the ice seams are fresh, This<br />

fluence of salinity <strong>on</strong> strength and deformati<strong>on</strong><br />

probably the reas<strong>on</strong> for the Svea clay's low properties is best accounted For through the recreep<br />

strength.<br />

It is difficult to quantify directly the influence<br />

of pore water salinity <strong>on</strong> strength of frozen<br />

soils. Results presented by Ogata (1983) REFERENCES<br />

clearly show that the relative strength reducti<strong>on</strong><br />

caused by increasing salinity is different<br />

for different types of soils. Our tests indicate<br />

that the relative strength reducti<strong>on</strong> caused by<br />

increasing salinity is not the same for compresai<strong>on</strong><br />

and creep strength. In our opini<strong>on</strong> the influence<br />

of salinity <strong>on</strong> strength of frozen soil Berggren, A-L.<br />

is best accounted for through the of use unfrozen<br />

water c<strong>on</strong>tent-temperature curves for determining<br />

the temperature dependent reference<br />

stress.<br />

A comparis<strong>on</strong> of the creep strengths determined<br />

by Berggren's model to creep strengths determined<br />

by other methods, shows that the Berggren<br />

model gives relatively low creep strengths, This<br />

is due to the fact that the model <strong>on</strong>ly allows<br />

stresses resulting in primary creep. The creep<br />

strains accumulated in the same design period<br />

uxe different for different clays. From Table<br />

VI11 it'is seen that the creep strains are<br />

str<strong>on</strong>gly dependent <strong>on</strong> pore water salinity. The<br />

most saline clays accumulate largest creep<br />

lati<strong>on</strong>ship between the unfrozen water c<strong>on</strong>tent<br />

and mechanical properties of clay.<br />

Berggren, A-L. (1983). "Engineering creep<br />

models for frozen soil behaviour".<br />

Dr. of Engineering thesis at the Norwegian<br />

Institute of Technology.<br />

and Furuberg, T. (1985). "A new<br />

Norwegian creep model and creep equipment"<br />

Proceedings ISGF85 Hokkaido University,<br />

Sapporo, Japan. pp. 181-185.<br />

Ogata, N,, Yasuda, M. and Kataoka, T. (1983).<br />

"Effects of salt c<strong>on</strong>centrati<strong>on</strong> <strong>on</strong> strength<br />

and creep behaviour of artifically frozen<br />

soils". Cold Regi<strong>on</strong>s Science and Technology<br />

8 (1983) pp. 139-153.<br />

1084

DECREASED SHEAR STRENGTH OF A SILTY SAND SUB.JECTED TO FROST<br />

G.P. Gifford<br />

Uni<strong>on</strong> College, Schenectady, N.Y.<br />

SYNOPSIS A unique direct simple shear device is described. The device is used to<br />

quantitatively assess the thaw-weakening of a soil. A relati<strong>on</strong>ship between void ratio and simple<br />

shear strength af a silty sand is established. The device is used with a specimen mold, a frost<br />

cabinet, and auxiliary instrumentati<strong>on</strong> to establish a relati<strong>on</strong>ship between void ratio and postthaw<br />

simple shear strength of the soil. The resulting relati<strong>on</strong>ship between void ratio and postthaw<br />

shear strength indicates the soil has weakened due to freeze and thaw. The causes of<br />

weakening are increased void rati<strong>on</strong> due to moisture migrati<strong>on</strong> during freezing and weakened plan<br />

at the locati<strong>on</strong> of previous ice lenses. During shear, suspected moti<strong>on</strong> of the thaw-freeze interface<br />

and flexibility of the reinforced membrane prove was shear not performed at c<strong>on</strong>stant volume.<br />

Therefore, it cannot be categorically stated that the post-thaw shear strength is Less than th<br />

prefreeze strength at all magnitudes of void ratio. However, the device shows great promise for<br />

‘quantitative assessment of thaw-weakening.<br />

INTRODUCTION<br />

The phenomen<strong>on</strong> of frost heave and subsequent<br />

thaw of soils can cause engineering problems,<br />

Present soluti<strong>on</strong> techniques are expensive and<br />

often based <strong>on</strong> past experience with Little or no<br />

scientific basis. A more thorough understanding<br />

is required to develop ec<strong>on</strong>omical design<br />

techniques. This paper reports the use of a<br />

device which employs the simple shear test mode<br />

<strong>on</strong> unfrozen and thawed soil samples.<br />

The device was developed at Worcester<br />

Polytechnic Institute and modeled after the<br />

simple shear device of the Norwegian<br />

Geotechnical Institute as reported by Bjerrum<br />

and Landva (1966). The dimensi<strong>on</strong>s of the shear<br />

sample are ideal for measuring the shear<br />

resistance in a highly anisotropic material,<br />

such as a soil sample c<strong>on</strong>taining melted ice<br />

lenses.<br />

As reported by Bishop (1971), the shearing<br />

resistance of a saturated soil is inve.rsely<br />

proporti<strong>on</strong>al to water c<strong>on</strong>tent when all other<br />

factors are equal. During thaw a soil c<strong>on</strong>tains<br />

“thaw-weakenedtt z<strong>on</strong>es with little or no ability<br />

to resist shear. Alkire (1983) assumes that<br />

some form of metastable cluster structure<br />

develops in a lOOP8 silt during freeze and thaw,<br />

and collapses under load. Little is known<br />

regarding the magnitude of strength change<br />

caused by this metastable structure.<br />

fit empirical equati<strong>on</strong> is developed relating<br />

void ratio to shear strength. The primary<br />

thermal c<strong>on</strong>diti<strong>on</strong>ing variables which were<br />

purposely varied during freeze are rate of heat<br />

extracti<strong>on</strong>, thermal gradient, and cycling of<br />

freeze--thaw. The effects which these variables<br />

have <strong>on</strong> the post-thaw shear strength are<br />

k<br />

discussed.<br />

EQUIPMENT EMPLOYED DURING THIS RESEARCH<br />

The direct simple shear (DSS) device c<strong>on</strong>sists of<br />

a specimen mold and top cap assembly. The<br />

device, shown in Fig. 1, is discussed in detail<br />

by Gifford (1984), and is briefly reviewed here.<br />

The specimen mold c<strong>on</strong>sists of twenty tapered an<br />

interlocked split acrylic discs. As recommended<br />

by Shen et a1 (l978), a maximum height to<br />

diameter ratio of 1:8 is utilized to maintain<br />

relatively uniform shear strain distributi<strong>on</strong>.<br />

The mold is Lined with a tapered rubber membrane<br />

which is laterally reinforced with nyl<strong>on</strong> thread.<br />

This membrane is employed during DSS testing to<br />

prevent leakage and provide lateral support of<br />

the sample.<br />

The top cap assembly is used to apply normal and<br />

shear stress to the thawed sample through the<br />

roughened porous st<strong>on</strong>e. The heating element<br />

thaws the top of a previously frozen specimen to<br />

produce a thaw-weakened DSS test sample.<br />

The objective of this report is to dem<strong>on</strong>strate a The elevati<strong>on</strong> of the top cap assembly is<br />

new device capable of assessing the shear<br />

variable, to enable a series of DSS tests to be<br />

strength of a silty sand subjected to frost<br />

performed <strong>on</strong> each previously frozen specimen.<br />

acti<strong>on</strong>. To this end the device was used to<br />

develop a relati<strong>on</strong>ship between void ratio and The frost cabinet and auxiliary instrumentati<strong>on</strong><br />

shear resistance for a frost-susceptible soil, are discussed by Gifford et a1 (1983) and<br />

both before and after thermal c<strong>on</strong>diti<strong>on</strong>ing. The reviewed here. In order to simulate frost<br />

test data is statistically analyzed, and a best acti<strong>on</strong> in the field, the cabinet is equipped<br />

1085

p<br />

x I I I<br />

rl<br />

normal load mechanism<br />

reacti<strong>on</strong> frame<br />

linear thrust bearing<br />

rocking resistant frame<br />

2<br />

4 translati<strong>on</strong> carriage<br />

0<br />

roller bearing assembly<br />

a,<br />

;<br />

B .!<br />

shear<br />

heating element<br />

roughened porous st<strong>on</strong>e<br />

split acrylic discs<br />

thermocouple lead<br />

reinforced membrane<br />

porous st<strong>on</strong>e<br />

ground watersupply<br />

PRESENTATION AND DISCUSSION OF RESULTS OF DSS<br />

TESTS ON UNFROZEN IKALANIAN SAND<br />

The results of undrained DSS tests performed <strong>on</strong><br />

unfrozen soil are presented and discussed in<br />

thie secti<strong>on</strong>. Also presented is a descripti<strong>on</strong><br />

of the research program employed. The purpose<br />

of the prefreeze porti<strong>on</strong> of this research is to<br />

establish a best fit relati<strong>on</strong>ship between void<br />

ratio and undrained shear strength whieh is<br />

compared to a similar relati<strong>on</strong>ship from<br />

post-thaw test results.<br />

The DSS tests were performed over a wide range<br />

of void ratio, e. After each test the entire<br />

sample was uses to determine moisture c<strong>on</strong>tent,<br />

w. The average void ratio for all samples was<br />

calculated from w assuming saturati<strong>on</strong>.<br />

uniform stress and strain distributi<strong>on</strong> <strong>on</strong> the<br />

sample boundaries is assumed valid. Therefore,<br />

average values of both shear stress, 7 , and<br />

normal stress, <strong>on</strong>l are assumed equally<br />

distributed throughout the sample.<br />

The soil utilized during this research is termed<br />

Ikalanian sand. Index, compacti<strong>on</strong>, and<br />

permeability test results are presented in Table<br />

I, al<strong>on</strong>g with associated ASTM test<br />

specificati<strong>on</strong>s. .<br />

Fig. 1<br />

The Direct Simple Shear Device<br />

with two independent refrigerati<strong>on</strong> units.<br />

Vermiculite insulati<strong>on</strong> helps develop the desired<br />

thermal gradient. Temperature of the specimen<br />

is m<strong>on</strong>itored with thermocouples placed al<strong>on</strong>g the<br />

outside of the membrane.<br />

During thermal c<strong>on</strong>diti<strong>on</strong>ing a plate placed <strong>on</strong><br />

the specimen prevents sublimati<strong>on</strong> and provides a<br />

stable base for the heave measurement system.<br />

Heave and moisture migrati<strong>on</strong> are m<strong>on</strong>itored<br />

electr<strong>on</strong>ically, Data from periodic readings of<br />

temperature, heave, and moisture migrati<strong>on</strong> are<br />

recorded by a data acquisiti<strong>on</strong> system,<br />

After the desired thermal c<strong>on</strong>diti<strong>on</strong>ing, the<br />

specimen is frozen throughout to 20°F (-7OC) and<br />

the top cap positi<strong>on</strong>ed For thawing the uppermost<br />

sample. After thaw, air is bled from the sample<br />

and the membrane ig clamped to the top cap.<br />

Water movement is prevented laterally by the<br />

membrane, downward by the still frozen subsoil,<br />

and upward by the to^ cap. During shear,<br />

c<strong>on</strong>stant sample height is mointained by manually<br />

adjusting the normal load.<br />

After shear the entire sample is removed for<br />

moisture c<strong>on</strong>tent determinati<strong>on</strong>, and the still<br />

frozen specimen top shaved to a horiz<strong>on</strong>tal<br />

plane. The remaining specimen is frozen<br />

throughout before the next thaw and shear.<br />

An alternate base is used with the top cap<br />

assembly to perform DSS tests <strong>on</strong> unfrozen soil.<br />

A pose pressure tranaducer in the base<br />

allows analysis of test data.<br />

TABLE I<br />

Results of Index, Compacti<strong>on</strong>, and<br />

Permeability Testing of Ikalanian Sand<br />

Index Property:<br />

Specific Gravity (D-854): 2.68<br />

Liquid Limit (D-423): N.P.*<br />

Plastic Limit ID-4241: N.P.<br />

Particle Size (D-421):<br />

%weight finer than:<br />

No. 4 (4.76mm) 100<br />

No. 10 (2 a OOmm) 99<br />

No. 20 (0.84mm) 96<br />

No. 40 (0* 42mm) 88<br />

No. 60 (0-25mm) 77<br />

No. 100 (0.1491t1m) 61<br />

NO. 200 (0.074m) 36<br />

0.02mm 9<br />

0.005mm 2<br />

0. OOlmm 1<br />

Compacti<strong>on</strong> Testing (D-698):<br />

Maximum Dry Density (KN/mS) 18.6<br />

Optimum Woisture C<strong>on</strong>tent (%) 13.0<br />

Permeability Testing (D-2434):<br />

k (cm/sec) 5.7 x LO'$ at e = 0.51<br />

k (cm/sec) 1.1 x 10" at e - 0.75<br />

*N.P. indicates n<strong>on</strong> plastic<br />

Since in-situ frost-susceptible soils often<br />

become saturated during thaw, and highway design<br />

tests often use saturated samples (i.e. CBR):<br />

all samples used in this research program were<br />

saturated. Failures related t o thaw-weakening<br />

are shallow in nature so a low,magnitude oi<br />

initial normal stress, uno, was used for all.<br />

I<br />

1086

tests. Three test series were performed <strong>on</strong><br />

saturated samples of Ikalanian Sand and<br />

designated SX, SIK, and NM.<br />

The SX test series c<strong>on</strong>sists of nine tests. The<br />

samples were prepared by pouring air-dry soil<br />

into Standing de-aired water in the membrane.<br />

After c<strong>on</strong>solidati<strong>on</strong> air was bled from the<br />

system, and the membrane clamped to the top cap.<br />

Water was allowed to percolate up through the<br />

sample from a c<strong>on</strong>stant head water supply for at<br />

least 24 hours.<br />

During these DSS tests c<strong>on</strong>stant volume and<br />

c<strong>on</strong>stant pore pressure were insured by<br />

maintaining c<strong>on</strong>stant elevati<strong>on</strong> of a water level<br />

in a standpipe which was attached to a drain<br />

line from the sample. The water level was held<br />

c<strong>on</strong>stant by adjusting the normal load.<br />

Knowledge of the hydrostatic heaa due to the<br />

water level yielded the pore pressure within the<br />

sample and c<strong>on</strong>sequently allowed ef.fective stress<br />

analysis of test data. Basic drainage<br />

calculati<strong>on</strong>s were performed which indicated that<br />

the shear rate was slow enough to allow complete<br />

dissipati<strong>on</strong> of excess pore pressure. These<br />

tests were, in fact, c<strong>on</strong>stant volume<br />

quasi-drained tests in that moisture c<strong>on</strong>tent and<br />

pore pressure remained c<strong>on</strong>stant during shear.<br />

The SIK test series c<strong>on</strong>sists of six tests. To<br />

ivsure saturati<strong>on</strong> the sand was boiled prior to<br />

use and poured into etanding de-aired water in<br />

the membrane. This series was performed prior<br />

to the installati<strong>on</strong> of the pore pressure<br />

transducer. Therefore, initial pore pressure<br />

magnitude Was assumed equal to that porti<strong>on</strong> of<br />

the initial normal stress applied to the sample<br />

after all drain lines were closed. The initial<br />

effective normal stress, uno', is equal to the<br />

difference. During shear, the change in pore<br />

pressure was assumed equal to the change in<br />

normal stress required to maintain c<strong>on</strong>stant '<br />

sample height.<br />

The NM te~t<br />

series c<strong>on</strong>sists of five tests.<br />

Sample preparati<strong>on</strong> and test procedure were<br />

identical to the SIK test series except that a<br />

pore pressure transducer was employed to m<strong>on</strong>itor<br />

pore pressure during c<strong>on</strong>solidati<strong>on</strong> and shear.<br />

stress paths in the T versus On' Stress Space<br />

were plotted for all teats. With the excepti<strong>on</strong><br />

of very loose samplea, the stress path touches<br />

and moves al<strong>on</strong>g a failure enve&ope. The arc<br />

tangent of this r/un' ratio yields the effective<br />

angle of internal fricti<strong>on</strong>, 9'. Furthermore, it<br />

may well be argued that the point of tangency<br />

adequately definae failure, and the magnitude of<br />

shear stress at this point is thg undsained<br />

shear strength, ~ f. This failure criteri<strong>on</strong> was<br />

employed for 16 tests.<br />

The stress path of very loose samples is erratic<br />

and does not move al<strong>on</strong>g a failure envelope. he<br />

magnitude of shear stress at the first peak in<br />

the stress path was adopted as failure. This<br />

failure criteri<strong>on</strong> was employed for four samples<br />

which possessed void ratios of 0.91, 0.80, 0.83,<br />

and 0.73.<br />

Fig. 2 shows the e versus rf data with a best<br />

fit natural logarithmic cuwe. The data scatter<br />

1087<br />

X \x<br />

0 = sx<br />

I I I el<br />

0.5 0.6 0.7 0.8 0<br />

Void Ratio, e<br />

FIG. 2<br />

e Versus rf for Unfrozen<br />

Ikalanian Sand<br />

appears reas<strong>on</strong>able for samples looser than e<br />

0.59, but for raamples denser than e = 0.59 the<br />

scatter is larger. The data scatter is due to<br />

partial drainage during shear caueed by volume<br />

change associated with flexibility of<br />

nyl<strong>on</strong>-reinforced membranes. The error of<br />

measured shear strength due to flexibility<br />

decreases with shear resistance.<br />

Since thaw-weakened shear resistance is expected<br />

to be low, the large magnitude errors from tests<br />

<strong>on</strong> dense samples are of little c<strong>on</strong>cern. The<br />

discussi<strong>on</strong> above, coupled with the other device<br />

related problems, enhanced employment of a<br />

different failure criteri<strong>on</strong> for thaw-weakened<br />

samples.<br />

PRESENTATXON AND DISCUSSION OF RESULTS ON<br />

THAW-WEAKENED IKALANIAN SAND<br />

The DSS results obtained from tests performed <strong>on</strong><br />

Ikalanian Sand which was thermally c<strong>on</strong>diti<strong>on</strong>ed<br />

in the frost cabinet are presented and<br />

discussed.<br />

Three 'thermal c<strong>on</strong>diti<strong>on</strong>ing variables were<br />

purposely varied to study how they effect the<br />

degree of ice lensing and ultimately the<br />

post-thaw shear strength. They are rate of heat

extracti<strong>on</strong>, thermal gradient, and cycling of<br />

freeze-thaw. To c<strong>on</strong>trol other variables, <strong>on</strong>e<br />

soil was used at approximately the same<br />

prefreeze void ratio, and each specimen was<br />

subjected to the same overburden prior to<br />

thermal c<strong>on</strong>diti<strong>on</strong>ing. With the excepti<strong>on</strong> of<br />

specimen FTS-6, all test specimens employed open<br />

water supply systems, and were initially<br />

capillary saturated. Test FTS-6 employed a<br />

closed water supply system and was initially<br />

fully saturated.<br />

All specimens except FTS-7 were subjected to <strong>on</strong>e<br />

freeze-thaw cycle. Test FTS-7 was subjected to<br />

two cycles as follows. After the desired<br />

thermal c<strong>on</strong>diti<strong>on</strong>ing, the specimen was frozen<br />

throughout to 200F (-7oC). Then the temperature<br />

of the upper porti<strong>on</strong> of the frost cabinet was<br />

incrementally raised to 340F (lac), and the<br />

lower cabinet porti<strong>on</strong> set at 30°F (-1OC). The<br />

thaw cycle lasted 130 hours. The specimen was<br />

then frozen from the top downward by a large<br />

temperature drop of the upper cabinet porti<strong>on</strong> so<br />

as to minimize freezing from the thaw-freeze<br />

interface upward.<br />

The rate of heat removal is directly related to<br />

the rate of frost fr<strong>on</strong>t penetrati<strong>on</strong>. The rate<br />

of frost fr<strong>on</strong>t penetrati<strong>on</strong> was varied throughout<br />

the research program and each individual test.<br />

The thermal gradient, defined as the change in<br />

temperature per unit length of specimen height,<br />

was varied throughout the entire test program.<br />

The rate of frost penetrati<strong>on</strong> into each specimen<br />

was scheduled in increments and varied for each<br />

test, so that nearly horiz<strong>on</strong>tal z<strong>on</strong>es of varying<br />

degrees of ice segregati<strong>on</strong> would develop. Table<br />

I1 presents a summary of the thermal<br />

c<strong>on</strong>diti<strong>on</strong>ing, and the prefreeze specimen<br />

characteristics; as well as moisture migrati<strong>on</strong><br />

and heave data for the six freeze tests<br />

performed <strong>on</strong> Ikalanian Sand. The corrected<br />

heave was calculated by subtracting the heave<br />

due to nine percent volume expansi<strong>on</strong> of pore<br />

water up<strong>on</strong> transformati<strong>on</strong> to ice from the total<br />

heave.<br />

Because of the difference in thermal<br />

c<strong>on</strong>ductivity of the acrylic mold and soil<br />

specimen unidirecti<strong>on</strong>al frost fr<strong>on</strong>t penetrati<strong>on</strong>,<br />

thus horiz<strong>on</strong>tal ice lensing was suspected.<br />

During rapid freezing, if the 32OF (ow)<br />

isotherm penetrates the mold more quickly than<br />

the soil, an arched 32OF (OOC) isotherm will<br />

develop within the specimen. If the depth of<br />

frost penetrati<strong>on</strong> is then held c<strong>on</strong>stant, the<br />

isotherm would become horiz<strong>on</strong>tal after some<br />

time, but ice segregati<strong>on</strong> might be smeared<br />

throughout the azchediz<strong>on</strong>e. One specimen, FTS-9<br />

was purposely removed from the frost cabinet<br />

after <strong>on</strong>ly three DSS tests to visually inspect a<br />

suspected ice lens. Examinati<strong>on</strong> of the<br />

collected data indicates that heave of 0.15 in.<br />

(0.38 cm) occurred a8 the depth of frost<br />

penetrati<strong>on</strong> increased from 4.2 in. (10.7 cm) to<br />

4.5 in. (11.4 cm). An ice lens, 0.12 in. (0.3<br />

cm) thick, was found within this depth, and<br />

extended horiz<strong>on</strong>tally completely across the<br />

specimen. This observati<strong>on</strong> proved that<br />

horiz<strong>on</strong>tal ice lensing can purposely be induced<br />

with this equipment,<br />

Knowing the moisture migrati<strong>on</strong> history of the<br />

specimen, it is c<strong>on</strong>ceivable to expect z<strong>on</strong>es of<br />

high post-thaw moisture c<strong>on</strong>tent and low<br />

post-thaw shear resistance at the locati<strong>on</strong> of<br />

ice lenses. Attempts to correlate the moisture<br />

migrati<strong>on</strong> and shear resisc%nce with thermal<br />

history were inc<strong>on</strong>clusive and are further<br />

discussed by Sage and D'Andrea (1983).<br />

In order to simulate field c<strong>on</strong>diti<strong>on</strong>s during<br />

thaw and post-thaw shear, the top cap was placed<br />

<strong>on</strong> the frozen specimen and a normal stress of<br />

Summary of Freeze Tests <strong>on</strong> Ikalanian Sand<br />

FTS-3 FTS-4 FTS-5 FTS - 6 FTS-7 FTS-9 '<br />

Initial Dry Density, KN/m 3 17.59 17.75 17.92 18.12 18.03 17.68<br />

Initial Moisture C<strong>on</strong>tent, % 18.4 19.1 18.8 17.0 17.5 18.8<br />

Initial void Ratio 0.49<br />

0.48 0.47 0.46 a. 47 0.49<br />

Initial Percent Saturati<strong>on</strong>, % 100.0 100.0 100.0 100.0 100.0 100.0<br />

Durati<strong>on</strong> of Test, hours 2186 116<br />

63<br />

62 515 156<br />

Number of Freezing Cycles 1<br />

1<br />

1<br />

1 2 1<br />

Number of Freezing Increments 14<br />

2<br />

1<br />

1 2<br />

3<br />

Ground Water C<strong>on</strong>diti<strong>on</strong>s<br />

OPEN OPEN OPEN CLOSED OPEN OPEN<br />

Maximum Frost Depth, cm 10.7<br />

8.9 13.5 11.7 11.4 13.0<br />

Max. Rate of Frost Pene. cm/day 2.29 12.80 199.90 51.31 188.98 28.19<br />

Aver. Rate of Frost Pene. cm/day 0.13 1.83 5.13 4.06 3.00 1.98<br />

Mini. Rate of Frost Pene. cm/day 0.00 0.56 0.36 1.24 2.74 0.76<br />

Aver. Thermal Gradient, 'C/crn 0.22 0.26 0.35 0.31 0.28 0.26<br />

Depth to Water Level, cm 21.6<br />

21.6 21.6 0.0 21.6 21.6<br />

Maximum Frost Depth. cm 10.7<br />

8.9 13.5 11.7 11.4 13.0<br />

Total Moisture Migrati<strong>on</strong> , cc 442.5 206.5 81.9 0.0 3.3 324 e 5<br />

Total Heave, cm 3.0 1.5 0.5 0.3 0.3 2.3<br />

Corrected Heave, cm 2.8 1.3 0.0 0.0 0.0 2.0<br />

Aver. Moist. Transfer Rate cc/day 4.92 42.77 31.30 0.0 0.0 49.98<br />

Aver. Heave Rate, cm/day 0.03 0.25 0.0 0.0 0.0 0.3<br />

1088

approximately 150 psi (7.2 KPa) was maintained<br />

during thaw. ha thaw commenced, air was bled<br />

from the sample and the membrane was sealed and<br />

clamped around the top cap. As thaw c<strong>on</strong>tinued,<br />

the nine percent volume loss caused by ice<br />

transformati<strong>on</strong> to water required that the normal<br />

stress be c<strong>on</strong>tinually adjusted to maintain 150<br />

psf (7.2 KPa)<br />

As the desired depth of thaw was approached, the<br />

heating element was turned off and a DSS test<br />

performed. During shear the elevati<strong>on</strong> of the<br />

top cap was maintained c<strong>on</strong>stant by adjusting the<br />

normal load as required. Pore pressure was not<br />

m<strong>on</strong>itored; and furthermore, the preshear pore<br />

pressure was not known. Therefore, a total<br />

stress analysis was the <strong>on</strong>ly means available for<br />

data interpretati<strong>on</strong>, and a somewhat arbitrary<br />

point <strong>on</strong> the total stress path must define<br />

failure.<br />

To this end, a statistical analysis was<br />

performed <strong>on</strong> prefreeze DSS test data. The<br />

values of shear strain, 6, at rf were plotted<br />

against void ratio. A best fit line was<br />

calculated via the least squares method and the<br />

equati<strong>on</strong> of the line is:<br />

6 = 100 (e - 0.49) (1)<br />

AS expected, strain at: failure increases with<br />

void ratio. The post-thaw shear strength of<br />

Ikahnian Sand, rpt, is herein defined as the<br />

measured shear resistance at the strain<br />

calculated from Equati<strong>on</strong> 1 utilizing the<br />

appropriate void ratio.<br />

Fig. 3 shows the e versus rPt data for 23 of the<br />

tests performed <strong>on</strong> thermally c<strong>on</strong>diti<strong>on</strong>ed<br />

Ikalanian Sand with a best fit natural<br />

logarithmic curve. The six data points which<br />

are circled exhibited minimal shear resistance<br />

and were not used to establish the best fit<br />

curve. Data from all 23 tests were grouped in<br />

this figure, because at a given void ratio<br />

little variati<strong>on</strong> of rPt was perceived,<br />

regardless of the rate of freezing, open or<br />

closed water supply syetem, or number of<br />

freeze-thaw cycles to which the specimen was<br />

subjected. Also included in Fig. 3 is the best<br />

fit cuxve from prefreeze data.<br />

Examinati<strong>on</strong> of Fig. 3 reveals the following. At<br />

a particular void ratio a saturated sample of<br />

unfrozen Ikalanian Sand possesses an undrained<br />

shear strength which is greater than that of a<br />

thawed sample at the same void ratio. It<br />

appears that thaw-weakening is caused by two<br />

effects. First, the additi<strong>on</strong>al water which<br />

migrates into the soil during freeze causes an<br />

increased void ratio of the sample up<strong>on</strong> thaw.<br />

This increased void ratio would cause a<br />

decreased shear strength al<strong>on</strong>g the prefreeze<br />

curve if the soil had not been previously<br />

frozen. The fact that the loss of strength is<br />

more than that due to the increase of void ratio<br />

is attributed to the fact that the soil was<br />

frozen. AS the soil grains separate due to<br />

freezing pore water and ice lensing, and<br />

Prefreeze<br />

909-0.072 Enrf<br />

0.5 0.6 0.7 0.8 0.9<br />

Void Ratio, e<br />

Fig. 3 e Versus T~~ €or Thaw-<br />

Weakened Ikalanian Sand<br />

subsequently c<strong>on</strong>verge during thaw, weak planes<br />

develop withih the specimen. The weakness of<br />

these planes is detected by the DSS device.<br />

The DSS device shows promise as a useful tool to<br />

evaluate the post-thaw shear strength of a<br />

previously frozen eoil specimen.<br />

A problem of the device has to do with the<br />

latent heat built up in the top cap during thaw.<br />

Because of the nine percent volume decrease<br />

associated with phase transformati<strong>on</strong> of ice to<br />

water, the normal load applied to the closed<br />

system decreases as thawing progresses.<br />

C<strong>on</strong>sequently, the magnitude of change of normal<br />

stress caused by c<strong>on</strong>tinued thaw and/or by soil<br />

behavior subject to undrained DSS testing is not<br />

distinguishable. This is the reas<strong>on</strong> the strain<br />

oriented failure criteri<strong>on</strong> was adopted.<br />

Furthermore, it is not possible to correct the<br />

test data, because of the variable amount of<br />

heat present during each test. Since shear<br />

resistance is a functi<strong>on</strong> of the effective normal<br />

stress, it cannot be categorically stated that<br />

the difference between prefreeze and post-thaw<br />

relati<strong>on</strong>ships presented in Fig. 3 is solely due<br />

to thermal c<strong>on</strong>diti<strong>on</strong>ing.<br />

Another complicating factor has to do with the<br />

measured moisture c<strong>on</strong>tent. There was a time lag<br />

of about ten minutes between executi<strong>on</strong> of the<br />

DSS test and sampling for moisture c<strong>on</strong>tent<br />

determinati<strong>on</strong>. c<strong>on</strong>tinued thaw during this time<br />

may have caused a change of moisture c<strong>on</strong>tent,<br />

thus void ratio, of the bulk sample.<br />

Undrained DSS tests were performed <strong>on</strong> thawed<br />

samples at various levels within the specimens.<br />

Profiles of moisture c<strong>on</strong>tent and post-thaw shear<br />

1089

strength with depth are presented by Gifford<br />

(1984). The profiles accentuate the anisotropic<br />

soil shear strength which is expected in a<br />

previously frozen soil column. The DSS test<br />

mode is geometrically ideal to investigate the<br />

shear resistance at the thaw-weakened z<strong>on</strong>es of<br />

limited vertical extent.<br />

CONCLUSIONS<br />

As dem<strong>on</strong>strated herein, this unique direct<br />

simple shear device can be used to evaluate the<br />

post-thaw shear strength of a frost-susceptible<br />

soil. This pi<strong>on</strong>eering use of the DSS test mode<br />

is particularly useful to assess the shear<br />

resistance at weakened z<strong>on</strong>es of a previously<br />

frozen soil column. Even though the results<br />

presented are inc<strong>on</strong>clusive, a new method of<br />

quantitatively measuring both the prefreeze and<br />

post-thaw shear strength of soil is introduced.<br />

The following c<strong>on</strong>clusi<strong>on</strong>s were reached:<br />

1. The incorporati<strong>on</strong> of a pora pressure<br />

transducer into the alternate DSS test device is<br />

useful, in that effective stress analysis of<br />

test data is available.<br />

2. As presently designed, the DSS device i s<br />

Less effective in assessing the strength of a<br />

thaw-weakened soil utilizing total. stress<br />

analysis.<br />

-3. Use of this DSS device lends itself to<br />

examinati<strong>on</strong> of the anisotropic z<strong>on</strong>al nature of<br />

thaw-weakened soil; especially C<strong>on</strong>sidering<br />

previous studies which used c<strong>on</strong>venti<strong>on</strong>al test<br />

methods.<br />

4. Based <strong>on</strong> test results presented herein, the<br />

following behavioral characteristics are noted<br />

specifically for Ikalanian sand:<br />

a. The undrained shear strength of saturated<br />

Ikalanian sand decreases with increased void<br />

ratio.<br />

b. Under appropriate c<strong>on</strong>diti<strong>on</strong>s, frost heaving<br />

of Ikalanian Sand produces ice lensing and<br />

subsequent z<strong>on</strong>es of high moisture c<strong>on</strong>tent<br />

after thaw. Furthermore, these z<strong>on</strong>es exhibit<br />

undrainad DSS strength magnitudes which are<br />

greatly reduced from the prefreeze strength,<br />

c. The post-thaw DSS strength of Ikalanian<br />

Sandis independent of the rate of frost<br />

penetrati<strong>on</strong>, the water supply system (open or<br />

closed), and the number of freeze-thaw cycles<br />

to which it had been previously subjected.<br />

d. The post-thaw DSS strength of Ikalanian<br />

Sand 'is less than that of the unfrozen<br />

saturated soil at an equivalent void ratio.<br />

e. Thermal c<strong>on</strong>diti<strong>on</strong>ing which causes an<br />

increase in Localized moisture c<strong>on</strong>tent<br />

produces a weakened plane within the<br />

Ikalanian Sand up<strong>on</strong> thaw. Therefore,<br />

thaw-weakening is produced not <strong>on</strong>ly by the<br />

increased moisture c<strong>on</strong>tent (i.e. void ratio)<br />

and decreased residual stress, but also from<br />

grain separati<strong>on</strong> <strong>on</strong> some plane.<br />

ACKNOWLEDGEMENTS<br />

The research described has been partially<br />

supported by the United States Department of<br />

Transportati<strong>on</strong>, office of University<br />

<strong>Research</strong>.and their c<strong>on</strong>tributi<strong>on</strong>s are gratefully<br />

acknowledged. The views presented herein,<br />

however, are those of the author. Thanks are<br />

also extended to the Massachusetts Department of<br />

Public Works Frost <strong>Research</strong> Stati<strong>on</strong> for<br />

supplying the Ikalanian Sand used during t his<br />

research.<br />

REFERENCES<br />

Alkire, "Chanae B. in D., and Soil Morris<strong>on</strong>, Structure Due J. M., to Freeze-Thaw<br />

(19831<br />

. -- - .- -<br />

and RGpeated Loading, Transportati<strong>on</strong> <strong>Research</strong><br />

Record #918, pp. 15-22.<br />

Bishop, A. W. , (1971). "Shear Skrength Parameters<br />

for Undisturbed and Remolded Soil Specimens,"<br />

In Stress-Strain Behavior of Soils,<br />

Proceedings, Roscoe Memorial Symposium,<br />

Cambridge University, Cambridge, England,<br />

pp. 3-58.<br />

Bierrum, L. and Landva, A,, (1966). "Direct<br />

-Simple Shear Tests <strong>on</strong> a Norwegian Quick Clay, I1<br />

Geotechnique, Vol. 16, No. 1, pp. 1-20.<br />

Gifford, G. P. , (1984)-<br />

'IAssessment of Shear<br />

Strenqth Loss of a Silty Sand Subjected to<br />

Frost-Acti<strong>on</strong>, Dissertati<strong>on</strong> Presented to the<br />

Faculty of Worcester Polytechnic Institute,<br />

Worcester, Ma., in partial fulfillment of the<br />

requirements for the degree of Doctor of<br />

Philosophy.<br />

Gifford, G. P., DIAndrea, R. A., and Sage, J.<br />

D., (1983). "A Device for the Evaluati<strong>on</strong> of<br />

Thaw-Weakening of Frost-Susceptible Soil,'I<br />

Transportati<strong>on</strong> <strong>Research</strong> Record #918,<br />

pp. 16-15.<br />

Sage, J. D. , and D'Andrea, R. A., (1983). "Shear<br />

Strength Characteristics of Soils Subjected<br />

to Frost Acti<strong>on</strong>," Final Report DTRS<br />

5680-C-00035, Department of Transportati<strong>on</strong>,<br />

Washingt<strong>on</strong>, D. C. , 143 pp. .<br />

Shen, C., Sadigh, K., and Hermann, L., (1978).<br />

"An Analysis of NGI Simple Shear Apparatus €or<br />

Cyclic Soil Testing," Dynamic Geotechnical<br />

Testing, ASTM STP654, pp. 148-162.<br />

1090

THEORETICAL FROBLEMS OF CRYOGENIC GEOSYSTEM MODELLING<br />

S.E. Grechishchev<br />

All-Uni<strong>on</strong> Scientific <strong>Research</strong> Institute of Hydrogeology and Engineering Geology, MOSCOW, USSR<br />

(NE) - geosystems - are c<strong>on</strong>sidered<br />

SYNOPSIS Cryogenic natural-territorial complexes<br />

a8 natural objecte of mathematical modelling for the purposee of geocryologic predicti<strong>on</strong>. A funoti<strong>on</strong>al<br />

thermodynamic model of NTC is suggested, in which cryogenic physical-geologic proceases<br />

are c<strong>on</strong>sidered as etrains of rocks that are a lithogerdc baais of NTC.<br />

C<strong>on</strong>siderable complexity of natural geocryologic<br />

ayetema ie specified by interacti<strong>on</strong> of<br />

m y pxocessea of the lower elaas, including<br />

the proceases in biota; therefore, the <strong>on</strong>ly<br />

aoluti<strong>on</strong> of the problem of geocryologic preacti<strong>on</strong><br />

is mathematical modelling.<br />

For the c<strong>on</strong>etructi<strong>on</strong> of a mathematical model<br />

of some natural object according to the pfinciplea<br />

of eystematic approach it ia necessary<br />

to perfom the following operati<strong>on</strong>88 determinati<strong>on</strong><br />

of the object of modelling (object of<br />

predicti<strong>on</strong>), formalizati<strong>on</strong> of the statement of<br />

predicti<strong>on</strong> problem, ascertainment of faotorsreas<strong>on</strong>a<br />

in a well-grounded plan, choice of model<br />

organizati<strong>on</strong>.<br />

The problem of distinguishing uniformly funatf<strong>on</strong>in<br />

natural bodies, the choice of which ELB<br />

a modefling object ie expedient, is for the<br />

last 20 years studied in detail by Landwape<br />

science, in the framework of which the study<br />

hae been developed of natural-territorial<br />

complexes (BTC) - "homogeneous, able to 8819-<br />

regulati<strong>on</strong> natural ayateme, c<strong>on</strong>nected with<br />

the outer medium through energy and mass<br />

transfern (Sockava, 1974). There in NTC close<br />

interc<strong>on</strong>necti<strong>on</strong>a axe realized between heat<br />

and moisture circulati<strong>on</strong> in rocks, their lithalogy<br />

and place in the relief, climate and<br />

vegetati<strong>on</strong> (Sochava, 1974; Krauclis, 1980;<br />

Shveteov, 1973).<br />

Soil and vegetati<strong>on</strong> are uaually accepted by<br />

apecialists in physical geography to be a part<br />

of WTC or geoayafem. The rocka that occur beneath<br />

the soil layer, are actually not c<strong>on</strong>eidered<br />

that ia reflected in the term "inert<br />

baSis" (Krauclis, 1980).<br />

But this view should not be c<strong>on</strong>sidered valid.<br />

lnveatigati<strong>on</strong>e carried out in the north of<br />

West Siberia by statistical methods have proved<br />

that there is a correlati<strong>on</strong> between appeaxance<br />

of NTC and ita lithogenic base to a c<strong>on</strong>siderably<br />

higher depth. Melnikov (1981) determined,<br />

for inatance, that NTC appearance for<br />

eifea correlates with lithogenic base to the<br />

depth of qeaa<strong>on</strong>aZ freezing-thawing layer, for<br />

atows it correlates with lithogenic baee to<br />

the depth of annual heat storage and for<br />

tract8 - to the depth of erosl<strong>on</strong>al cut.<br />

The data above indicate that NTC ahould be<br />

c<strong>on</strong>sidered as the whole complex of eurface<br />

c<strong>on</strong>diti<strong>on</strong>e (vegetati<strong>on</strong>, soil. cover, soils)<br />

and underlying lithogenic baae to their correlati<strong>on</strong><br />

depth. As NTC are geoeysterne c<strong>on</strong>necfea<br />

with the outer envir<strong>on</strong>ment through energy<br />

and masa exchange, then such a correlati<strong>on</strong><br />

apeaka for self-orgeaizing accompanied by homeostaais,<br />

In this case homeostaeie area of<br />

cfyogenic NTC should coincide with lithology<br />

variati<strong>on</strong>s observed in natural c<strong>on</strong>diti<strong>on</strong>a and<br />

also soil moisture and temperature with the<br />

88me biota compositi<strong>on</strong>.<br />

The NTC definiti<strong>on</strong> euggested includes, as characters,<br />

the following two important circumstances,<br />

First, the main character i~ homogenity<br />

criteri<strong>on</strong>, <strong>on</strong> this basis a system is<br />

singled out as a homogeneous nntural body,<br />

and this is an area of its homeostasis. Sec<strong>on</strong>d,<br />

homeostasis boundaries are a natural<br />

limit bey<strong>on</strong>d that thermodynamic stability of<br />

the eyetem ie lost. So a suggeefed interpretati<strong>on</strong><br />

of NTC is a aynthesi~l of ideae about<br />

BTC as an energy and masa exchange syatem<br />

with c<strong>on</strong>cepts developed by Shveteov about<br />

thermodynamic stability of soil aeaociati<strong>on</strong>.<br />

The aim of geocryologic predicti<strong>on</strong> and hence<br />

simulati<strong>on</strong> is to determine a change of geocrye<br />

ologic c<strong>on</strong>diti<strong>on</strong>s in time wlthin natural-terriforial<br />

complexes for a given period. In thin<br />

ca8e geocryologic c<strong>on</strong>diti<strong>on</strong>s w e as follows:<br />

temperature, total moisture c<strong>on</strong>tent, aoil. ice<br />

c<strong>on</strong>tent, ice body availability, thickness of<br />

freezing and thawing layem, cryogenic &ai--<br />

cal geological proceeaee (thermokarst, heaving,<br />

fmcturing, soliflucti<strong>on</strong> etc,). It should<br />

be noted that under energetical (thermodynamic<br />

1 approach cryogenic physical geological<br />

procaaees are c<strong>on</strong>sidered in a generalized view<br />

aEi moti<strong>on</strong> (migrati<strong>on</strong>, deformati<strong>on</strong>) within and<br />

at the border of soil complex.<br />

1091

The energetical approach to the analysis of<br />

NTC functi<strong>on</strong>ing allows to make its functi<strong>on</strong>al<br />

thermodynamic model.<br />

To formalize the aim of geocryologic predicti<strong>on</strong>,<br />

NTC ahould be c<strong>on</strong>sidered a8 a certain<br />

area D with <strong>on</strong>e relati<strong>on</strong>, c<strong>on</strong>stituted by rocka<br />

that are a lithogenic base of NTC with the<br />

boarder line L, that Is the soil aurface. Within<br />

the D area there is area D, with <strong>on</strong>e and<br />

many relati<strong>on</strong>s and with the temperature lower<br />

than OOC (seas<strong>on</strong>ally and perennially frozen<br />

ground) with boarderline L . In its turn there<br />

is a subarea with many redti<strong>on</strong>a C2 of ice<br />

bodies with the boarderline L, within the area<br />

Dl<br />

Formalizing of "cryogenic physical geologLca1<br />

proce8st1 notF<strong>on</strong> is not difficult if to take<br />

account of ita definiti<strong>on</strong> as a "morphogenetic<br />

pxoaeas". Such a definiti<strong>on</strong> is i terpreted by<br />

the deformati<strong>on</strong> (moti<strong>on</strong>) vector 8 noti<strong>on</strong> of<br />

the surface L, that is boundasy meaning of<br />

the deformati<strong>on</strong> vector #of the whole area D.<br />

Thue cryogenic proc 88s can be formalized aa<br />

deformati<strong>on</strong> vector v(including rupturesfracturee)<br />

in the area E. This ie <strong>on</strong>e of the<br />

main differences of the suggeated functi<strong>on</strong>al<br />

model oaxiant from analogous models in phyaical<br />

geography and other related Bciencea. To<br />

idelztiricate the pes of cryogenic proceaaee<br />

,baaing <strong>on</strong> vector @jointly with boundariee L,<br />

and L , occurring in soil, it ia neceaaary<br />

to eliborate the criteria of identificatioli<br />

(i.e. a certain analyzing block in the model).<br />

C<strong>on</strong>sidering the above menti<strong>on</strong>ed, the aim of<br />

geocryologic predicti<strong>on</strong> can be formalized a8<br />

w (total<br />

dariea L, and L2<br />

time Z in the area C f L,<br />

When selecting factors that affect changes<br />

of geocryologic c<strong>on</strong>diti<strong>on</strong>s of NTC, a formalized<br />

definiti<strong>on</strong> of geocryologio redicti<strong>on</strong><br />

aim should be c<strong>on</strong>sidered. In partfcular, factora<br />

should not be c<strong>on</strong>sidered with a period of<br />

variati<strong>on</strong> eseentislly more (trend <strong>on</strong>es) or eaeentially<br />

lese (ehorf-period <strong>on</strong>es) than a predicted<br />

<strong>on</strong>e. Changes of world ocean level, climatic<br />

fluctuati<strong>on</strong>s (as climate ie a mean value<br />

for a 30-yeare , tect<strong>on</strong>ic movement glaciati<strong>on</strong><br />

etc. ref%":: trend changes. Ea&<br />

fluctuati<strong>on</strong>s of meteoelemente refer to shortperiod<br />

changes.<br />

One of the main purposes of geocryology is<br />

Btudying the factore that influence the process<br />

of geocryologic c<strong>on</strong>diti<strong>on</strong>s change. They<br />

are preeented in a number of generalising<br />

works (Principles of permafrost predicti<strong>on</strong>s,<br />

1974; Pavlov, 1979; Grechiehchev, Chistotinov,<br />

Shur, 1984 etc. ). Vith regard to this a hysical-geographical<br />

axiom by Shvetaov (19737 ie<br />

a very useful <strong>on</strong>e according to it geocryologic<br />

c<strong>on</strong>diti<strong>on</strong>e are determined by interacti<strong>on</strong> of<br />

three comp<strong>on</strong>ents: climate, ground compoaiti<strong>on</strong><br />

ana ita place in the relief. The following<br />

groups of factors, affecting geocryologic<br />

c<strong>on</strong>&Lti<strong>on</strong>s should be singled out: hydxometeorologic,<br />

compoaiti<strong>on</strong> and properties of soil<br />

cover, relief, compositi<strong>on</strong> and propartiee of<br />

ground, human activities. The latter include8<br />

any changes of heat and masB exchan e, relief,<br />

soil cover, cauaed by human activitfee (c<strong>on</strong>structi<strong>on</strong><br />

and operati<strong>on</strong> of engineering a,tructures).<br />

To make a functi<strong>on</strong>al (mathematical in future)<br />

NTC model it is reas<strong>on</strong>able to subdivide the<br />

above menti<strong>on</strong>ed groupe af factore ihto two<br />

within subgroupe: D + L factors depending <strong>on</strong> the area (i.8. In grounde, o<strong>on</strong>etitut-<br />

processea<br />

ing BTC) aad factors that do not depend <strong>on</strong> the<br />

procesa inside the area. A list of factom,<br />

affecting MTC geocryologic c<strong>on</strong>diti<strong>on</strong>s with<br />

allowance for formalized aim of geocryologic<br />

predicti<strong>on</strong> is given in Table 1.<br />

Pesign of a functi<strong>on</strong>al cybernetic NTC model<br />

can be carrie'd out <strong>on</strong> the baela of different<br />

principlee.For instance, 14 can be made <strong>on</strong> the<br />

baais of claeeifying .the factore valid for the<br />

input to the area D. But the complexity of<br />

such a model. is too high. That Is why a xati<strong>on</strong>al<br />

organizing principle ahould eerve a basis<br />

of a model.<br />

AB the purpose of geocryo~ogic predicti<strong>on</strong> is<br />

to determine changes of thermal and moisture<br />

c<strong>on</strong>diti<strong>on</strong>s of rocka (physical proceeeea) and<br />

development of cryogenic phyaical geological<br />

procewes (mechanical proceseree), then a model<br />

should reflect a c<strong>on</strong>necti<strong>on</strong> between thephysics<br />

and mechanics, $.e, to refef to a<br />

clam of thermodynamic modela. As far a such<br />

NTC, aocording to definiti<strong>on</strong>, is a syatem open<br />

to energy and maser, then a model ahould refled<br />

energy and mas8 exchange.<br />

!Chum BTC model ehould base <strong>on</strong> the principle of<br />

energy and masa exchange of the area D + L<br />

with the outer envir<strong>on</strong>menf. Noreover pae BXchange<br />

will moan <strong>on</strong>ly moisture exchange ae for<br />

the main types of cxyogenic NTC the other comp<strong>on</strong>ents<br />

of mas8 exchange are not significant<br />

eolian rede oaifs of sand and'auat 8011~) or<br />

can be. c<strong>on</strong>sflderad in a different way (for inetance,<br />

anowstorm transport of mow oan be taken<br />

into account wtth E certain coefficient,<br />

c<strong>on</strong>stant for each NTC and depending <strong>on</strong> relief<br />

and surface rougbeae).<br />

Relative to the Pact thst.there the input of<br />

NTC system must be energy and maam, their balance<br />

<strong>on</strong> the surface L ahoula be c<strong>on</strong>sidered.<br />

Thie approach to thermophysicd aspect8 of<br />

hndacapes is comm<strong>on</strong> and in c<strong>on</strong>formity with<br />

permafrost z<strong>on</strong>e it ie well. preaented in Pavl<br />

lov's work, 1979. As far atl heat, entering the<br />

soil. ie the morJt interesting aspect of heat<br />

balance for UB, then the main equati<strong>on</strong> of heat<br />

balance will be as follows:<br />

P = Qc - (QcA + Ief t P + LE), (1)<br />

where Q - heat, entering the soil; L - moisture<br />

evaporati<strong>on</strong> heat; the reat are given in<br />

Table 1.<br />

Comp<strong>on</strong>ents of heat balance in equati<strong>on</strong> 1 aefend<br />

<strong>on</strong> o<strong>on</strong>dltf<strong>on</strong>a <strong>on</strong> the aurface L, that alows<br />

to write this equati<strong>on</strong> in the following<br />

generalized way:<br />

1092

TABLE 1<br />

Factora Affecting Geocryologlc C<strong>on</strong>diti<strong>on</strong>e of NTC<br />

Groups of factors Factora, depending <strong>on</strong> the procesees Factors, that do not depend <strong>on</strong> the<br />

within the area E + L<br />

processes within the area C + L<br />

Hydrometeorologic<br />

Compositi<strong>on</strong> and<br />

properties of soil<br />

cover ( rt)<br />

Belief<br />

Compositi<strong>on</strong> a d<br />

ropartiss of roeka<br />

PC 1<br />

Technogenic (human<br />

Evaporati<strong>on</strong> from the surface L of At the height of 2 m above L; total<br />

the soil and by soil covers (E); radiati<strong>on</strong> (Q 1; reci itati<strong>on</strong> (0);<br />

c<strong>on</strong>vective heat flow (P); effecti- air temperatare tairP; humidity<br />

ve radiati<strong>on</strong> (Ieee); cover albedo c'y,i* 1<br />

(A); wind velocity at the height<br />

of I m; aoil temperature (tL);<br />

soil moisture (WL); surface water<br />

inflow (r)<br />

Thickness of the cover, density<br />

(of the anow cover) or epecific<br />

biomes (of vegetati<strong>on</strong> cover);<br />

relative phytomass area; vegetati<strong>on</strong><br />

extincti<strong>on</strong>; traneparency of<br />

water layer; 8011 cover roughness;<br />

heat c<strong>on</strong>ducti<strong>on</strong>, heat capacity,<br />

vapour and moiature c<strong>on</strong>ductivity<br />

(of mow, water or technogenic<br />

cover) etc.<br />

Surface outline (b)<br />

Thermophysical (heat c<strong>on</strong>aucti<strong>on</strong>,<br />

heat capacity); mechanical (deform<br />

mati<strong>on</strong>, strength, thermal expansl<strong>on</strong>,<br />

ewelling etc.); mass exchange<br />

(moisture c<strong>on</strong>ductivity, water<br />

yielding capacity from the surface<br />

etc.)<br />

Lithology,.granulometric Compositi<strong>on</strong>,<br />

wafer-physical properties (plastic<br />

limlt, moisture capacity etc.)<br />

Heat inflow to the ground Prom engineering<br />

structuree (AQT); disturbances<br />

o f aoil cover under c<strong>on</strong>structing<br />

and operating these structures (bnP);<br />

B change of surface water inflow under<br />

artificial irrigati<strong>on</strong> or drainage<br />

( &MT); a change of surface profile<br />

(foundati<strong>on</strong> pits, embankments) - dLT<br />

Maes (Moisture) balance <strong>on</strong> the surface L can<br />

be c<strong>on</strong>sidered in the analogous way. Moisture<br />

balance equati<strong>on</strong> solved for moieture msa,<br />

entering the rroil or leaving it can be written<br />

in the form:<br />

M = O + r -(s+E) (3)<br />

where Y - moisture, entering the eoil, S -<br />

surface run off, the rest are given in Table<br />

1.<br />

Comp<strong>on</strong>enta of water balance in equati<strong>on</strong> (3)<br />

alao depend <strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s <strong>on</strong> the surface L,<br />

that can be given in the following generalized.<br />

fomr<br />

When making a functi<strong>on</strong>al (and <strong>on</strong> its baeis a<br />

mathematical) model of NTC it is essential<br />

that factors, valid inside the area D + L and<br />

affecting factora-reas<strong>on</strong>e in the way analogow<br />

to feedback, can be summed up with the latter,<br />

This c<strong>on</strong>diti<strong>on</strong> is significant, ae most relati<strong>on</strong>s<br />

in NTC aystem are not linear. Energy<br />

and mama incrementa satisfy thls requirement.<br />

So, assuming that balance relati<strong>on</strong>ships (2).<br />

and (4) satisfy expansi<strong>on</strong> into seriea c<strong>on</strong>diti<strong>on</strong>s<br />

let's mite them down as increments:<br />

1093

Fig. 1<br />

Functi<strong>on</strong>al model of cryogenic NTC for geocxyologic predloti<strong>on</strong>a.<br />

The following notea should be made to the bslance<br />

equati<strong>on</strong>s (5). The first equati<strong>on</strong> ia a<br />

transformati<strong>on</strong> of the heat balance equati<strong>on</strong><br />

(I). Calculati<strong>on</strong>s, based <strong>on</strong> thi8 equati<strong>on</strong>s,<br />

are c<strong>on</strong>sidered in Borne works, to be difflcult<br />

<strong>on</strong>e8 as the heat value Q, entering the Boil,<br />

is small if compared with Q,, namely it ie a<br />

small difference between large numbers. Phia,<br />

in some cams, can bring about a c<strong>on</strong>eiderable<br />

emor in deterfillzing Q. Accordingly, a change<br />

to the eoil surface temperatufe when oalculating<br />

ie made <strong>on</strong> the basis of air temperature.<br />

Then, instead of the firat of equati<strong>on</strong>s (5)<br />

another <strong>on</strong>e is taken, namely:<br />

and 80 <strong>on</strong>. In a general cam dependence between<br />

soil cover compoaiti<strong>on</strong> and pro erfiea can<br />

evidently be represented aa a oertaxn temporary<br />

operat OF<br />

Proceeaes of heat and moisture rediatributi<strong>on</strong><br />

and deformati<strong>on</strong> development within the area<br />

D + L under known heat and moisture flows at<br />

the area boundary, ifa outline and soil properties<br />

can be described by thermoreology<br />

equatims of frozen ground (Grechiahchev,<br />

Chistotinov, Shur, 1984) that can be symbalioally<br />

given as a certain operator<br />

where tair - is air temperature.<br />

The uae of the latter equati<strong>on</strong> inetead of the<br />

heat balance equati<strong>on</strong> doea not affect the c<strong>on</strong>structi<strong>on</strong><br />

of a general functi<strong>on</strong>al model. Later<br />

<strong>on</strong> incremental signs will be omitted.<br />

Soil covers: vegetati<strong>on</strong>, mow, water and human<br />

(for instance, asphalt) are very important for<br />

energy and mass exchange of Landacapes. Compositi<strong>on</strong><br />

and properties of vegetati<strong>on</strong> cover depends<br />

<strong>on</strong> the relief, tern mature, soil moieture<br />

and time (phytocoenosfs age); of snow cover<br />

- <strong>on</strong> the relief (snow blowing off the elevated<br />

places and ita accumulati<strong>on</strong> in the depressi<strong>on</strong>s)<br />

and vegetati<strong>on</strong>; water depth - <strong>on</strong> the relief<br />

Boundary outline L depends <strong>on</strong> deformati<strong>on</strong> VBCtor<br />

at the boundary, i.e.<br />

L = L (U,).4 (9)<br />

Soil properties depend <strong>on</strong> its temperature<br />

total moieture c<strong>on</strong>tent, that can be given<br />

c = c (t, w).<br />

and<br />

as :<br />

( 10)<br />

1094

Equati<strong>on</strong>s (5)-(10) form a closed aystem. They<br />

axe graphically shown in the acheme of Fig. 1,<br />

that represent functi<strong>on</strong>ing of NTC and can be<br />

called a functi<strong>on</strong>al model of NTC. It refers<br />

to a class of aimultati<strong>on</strong> thermodynamic modela<br />

and ie composed of the following, united by<br />

feedback and feedforward, blocke: relief, comositi<strong>on</strong><br />

and properties of surface covers<br />

P biota, snow and technogenic covere etc.),<br />

compositi<strong>on</strong> and properties of NTC to the depth<br />

of ita correlati<strong>on</strong> with the surface covera.<br />

At the input to the model there are factore<br />

of energy exchange (climate energetic comp<strong>on</strong>ente:<br />

radiati<strong>on</strong> or sir temperature above and<br />

geotermic gradient or mean temperature of the<br />

higher NTC rank) and mass exchange (precipitati<strong>on</strong><br />

and hydrologic regime), ut the output of<br />

the model there are thermal moisture c<strong>on</strong>ati<strong>on</strong>a<br />

and cryogenic physical geological praceasea.<br />

There <strong>on</strong> the acheme possible incrementa<br />

axe also given for heat, moisture, surface<br />

covera and relief caused by technogenic reas<strong>on</strong>s<br />

(see Table l).<br />

The main advantage of a functi<strong>on</strong>al model ia<br />

that it makes visible the whole complex of<br />

processes ocaurring in a natural. object and<br />

c<strong>on</strong>tributing to a better understanding of predicti<strong>on</strong><br />

aim. Besides, if allows to combine detmrminiBtic<br />

physical mathematical modele with<br />

empirical relati<strong>on</strong>a, obtalned Prom direct observati<strong>on</strong>s<br />

for the regime of separate NTC comp<strong>on</strong>ents<br />

without physioal analyeis of their<br />

interrelati<strong>on</strong>e.<br />

Investlgatiin of moil complex functi<strong>on</strong>ing can<br />

be carried out with the offered functi<strong>on</strong>al<br />

thermodynamic model. In particular, it6 analysis,<br />

allows to a<strong>on</strong>cretize a principle noti<strong>on</strong><br />

of thermodynamic etability of natural geocrgologic<br />

bodies, that oan be defined 88 a<br />

rekurn of the aystem, after outer impaot, t o<br />

the homeostaaia area that is the area o f e uilibxium<br />

in phase apace of characters. If a%ter<br />

an outer (technogenic, for instance) impact a<br />

system does not return to a homeostaais area,<br />

then it means a lose of equilibrium. In this<br />

way the value can be determined of perdesible<br />

outer impacts <strong>on</strong> NTC, that is required for<br />

determining the purposes of envir<strong>on</strong>ment protecti<strong>on</strong>,<br />

for instance.<br />

One of the future problems in mathematical<br />

modelling is the problem OP model atability<br />

due to a great number of factors ana to a<br />

probabilistic character of the initial data,<br />

obtained in the process of regi<strong>on</strong>al investigati<strong>on</strong>s.<br />

A possible way to solve thio problem<br />

is development o f optimal. mathematical models,<br />

to minimizing calculati<strong>on</strong> errom.<br />

REFERENCES<br />

Grechishchev, S.E., Chietofinov, L.V.,Shur,<br />

Y.L. (1984). Osnovy modelirovaniya<br />

kriogennykh fiziko-geologicheskikh pro:<br />

tseeaov. M., Nauka, 230 a.<br />

Krauklis, A.A. (1980). Eksperimantalnoye<br />

landshaftovedenie. Bovoeibirak, IJauka,<br />

320 a.<br />

hlelnikov, E.S. (1981). K razvitiyu metodologicheskikh<br />

omov regi<strong>on</strong>alnof inzbenernoi<br />

geologii. Inzhenernaya geologiye,<br />

N 6.<br />

Osnovy merzlotnogo prognoza pri inzhenernogeologicheakikh<br />

iseledovaniyakh. M.,<br />

IZd-VO MGU, 1974, 432 El.<br />

F’avlov, A.V. (1979). Eeplofizika landahaftov.<br />

Novosibirsk, Nauka, 320 a.<br />

Shvetsov, P.F. (1973). Obshchie polozheniya.<br />

V knige: Osnovy metodiki inzhenerno-geokriologichetjklkh<br />

prognozov pri razvedke<br />

mestorozhdenii tverdykh poleznykh iakopaemykh.<br />

M., Neha, 8.10-20.<br />

1095

USE OF GEOTEXTILES TO MITIGATE FROST HEAVE IN SOILS<br />

K. Henry<br />

U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering Laboratory, Hanover, N.H. 03755-1290 USA<br />

SYNOPSIS<br />

One potential use of geotextiles is horiz<strong>on</strong>tal placement in soil above the<br />

water table to act as a capillary break or barrier to mitigate frost heave. A capillary break<br />

works because larger pore sizes and/or wetting angles of the material than simrounding soil result<br />

in lower unsaturated hydraulic c<strong>on</strong>ductivity and lowered height of capillary rise'of water. This<br />

reduces frost heave by limiting the rate of upward water migrati<strong>on</strong>.<br />

Five series of open-system, unidirecti<strong>on</strong>al frost-heave tests were run in which three n<strong>on</strong>woven<br />

polypropylene geotextiles were tested for their ability to mitigate frost heave. Certain fabrics<br />

were successful in reducing frost heave by as much as 85%. Test results also indicate that the<br />

optimum fabric thickness required to mitigate frost heave is a functi<strong>on</strong> of soil type as well as<br />

properties of the geotextile.<br />

INTRODUCTION<br />

Frost acti<strong>on</strong> in soils poses significant problems<br />

for highway and airport pavements. The<br />

advent of the use of geotextiles in pavement<br />

secti<strong>on</strong>s offers the possibility o f mitigating<br />

frost effects. Certain geotextiles can be<br />

placed horiz<strong>on</strong>tally in the soil above the<br />

water table to reduce upward water migrati<strong>on</strong><br />

under freezing c<strong>on</strong>diti<strong>on</strong>s.<br />

The presence of a capillary break in frostsusceptible<br />

soil can, in certain cases, reduce<br />

frost heave by reducing the height of capillary<br />

rise of ground water and by reducing the<br />

upward migrati<strong>on</strong> of water under tensi<strong>on</strong> gradients<br />

when the capillary break is not saturated.<br />

It is hypothesized that geotextiles with<br />

comparatively large pore sizes and fibers that<br />

are hydrophobic can be successfully used as<br />

capillary breaks.<br />

The laboratory investigati<strong>on</strong> currently under<br />

way at CRREL is attempting to show that<br />

properly chosen geotextiles will behave as<br />

capillary breaks when placed in froat-susceptible<br />

soil and to better define the characteristics<br />

important to a geotextile's ability<br />

to mitigate frost heave. To date, <strong>on</strong>ly n<strong>on</strong>woven<br />

polypropylene qeotextiles have been<br />

tested because they performed comparatively<br />

well in preliminary tests.<br />

lary path and thereby reducing water available<br />

at the freezing fr<strong>on</strong>t (e.g. Rengmark, 1963).<br />

The saturated hydraulic c<strong>on</strong>ductivities of many<br />

geotextiles are similar to clean medium to<br />

fine sands (Bell et al., 1980), which suggests<br />

their use as capillary breaks due to pore sizes.<br />

In additi<strong>on</strong>, some fabrics c<strong>on</strong>sist of<br />

fibers that have a lower affinity for water<br />

than soil particles, which is likely to enhance<br />

their ability to reduce capillary rise.<br />

In a laboratory study c<strong>on</strong>ducted by Allen st<br />

al. (1983) in which five geotextilee were<br />

tested by placing them in samples of frostsusceptible<br />

soil and freezing the samples,<br />

they stated that the qeotextiles that reduced<br />

frost heave the most were either relatively<br />

thick and permeable* as well as somewhat<br />

hydrophobic or were l'str<strong>on</strong>gly hydrophobic."<br />

The 'lhydrophobicityl' of the materials was<br />

evaluated based <strong>on</strong> the casual observati<strong>on</strong> of<br />

water <strong>on</strong> the surface of these materials<br />

(Allen, 1986). One geotextile that was<br />

described as being made of hydrophilic material<br />

actually increased frost heave compared to<br />

the reference sample (Allen et al., 1983).<br />

Allen et al. (1983) did not discuss the results<br />

in terms of pore characteristics such as<br />

pore size distributi<strong>on</strong> in the various fabrics<br />

compared to the pore or grain size distributi<strong>on</strong><br />

of the soil. A survey of manufacturers'<br />

literature revealed that the AOS** of the<br />

No actual values of permeability for specific fab-<br />

PREVIOUS WORKS<br />

rics tested wexe published; however, it is implied<br />

that they ranged from 0.1 to 0.01 cm/sec (Allen et<br />

The placement of layers of clean sands and<br />

al., 1983). These values of permeability are compafable<br />

to those of clean sand.<br />

gravels in frost-susceptible materials has<br />

been known to reduce fkost heave (Rengmark,<br />

1963: Taivainen, 1963). It is thought that ** AOS, or apparent opening si2e (also referred to<br />

when wlaced above the water table and below<br />

as equivalent opening size or EOS), is defined as<br />

the dipth of frost penetrati<strong>on</strong>,- coarse materi- the number of the U.S. standard sieve with openings<br />

al reduces frost heave by breaking the capil- closest in eize to the largest openings in the geotextile<br />

(CW-02215. 1986).<br />

1096

Table I.<br />

Engineering properties of geotextiles as manufactured.<br />

Geotaxtile<br />

C<strong>on</strong>structi<strong>on</strong><br />

and<br />

Equivalent<br />

Hydraulic K Opening<br />

Thickness C<strong>on</strong>ductivity Size<br />

I cm\ Icm/sec) tmm)<br />

Fibertex 200 Needle-punched 0.19 0.15 0.15<br />

polypropylene<br />

Fibertex 400 Needle-punched 0.38 0.3 0.15<br />

polypropylene<br />

Mirafi 60Qx<br />

Typar 3401<br />

Woven<br />

polypropylene<br />

Heat-b<strong>on</strong>ded<br />

polypropylene<br />

0.01 0.1-0.85<br />

0.038 0.03 0.23-0.15<br />

,<br />

1501 i<br />

the fabric's pore characteristics,<br />

200<br />

0 X) 40 60 80 1 0 0<br />

Time (hours)<br />

Figure 1. Results of standard CRREL frostheave<br />

tests c<strong>on</strong>ducted <strong>on</strong> Dartmouth sand with<br />

three different geotextiles (modified after<br />

Chamberlain, 1986).<br />

best- and worst-performing fabrics was essen--<br />

tially the same, indicating the inadequacy of<br />

AOS as an index of pore characteristics and<br />

the need for a measure of pore size distributi<strong>on</strong><br />

of the fabrics to better examine their<br />

effect.<br />

Hoover et al. (1981) examined the ability<br />

of geotextiles to act as interlayer reinforcement<br />

in the c<strong>on</strong>structi<strong>on</strong> and maintenance of<br />

roadway secti<strong>on</strong>s. Mirafi 140, a heat-b<strong>on</strong>ded<br />

polypropylene fabric was found to reduce heave<br />

in open-system laboratory freeze-thaw tests.<br />

Although Hoover et al. (1981) did not discuss<br />

c<strong>on</strong>sultati<strong>on</strong><br />

with the manufacturer indicates that the<br />

fabric has a coefficient of permeability of<br />

0.05 cm/s, which is <strong>on</strong> the order of that of<br />

a medium to fine sand (Lothspeich, 1988). The<br />

sample that heaved the least had two layers of<br />

fabric -- each located at a 1/3 point in the<br />

sample. The fabric also improved all stability<br />

and strength parameters of the soils in<br />

the laboratory.<br />

U. S. Std. Sieva Openinq (in.) U.S. Std. No. Hydrometer<br />

6 3 Illz =/4 s/s 4 8 14 20 40 70 140<br />

(Ist,Znd. 3rd<br />

80 test series)<br />

\<br />

Groves Sand<br />

(4th, 5th)<br />

(1st. 2nd,Jrd)<br />

Grain Size (mm)<br />

S<strong>on</strong>d<br />

1 Cmrz' Fine iCmrm, Mndlvrn [ Fin. I<br />

Effective<br />

Silt or Cloy<br />

1<br />

0 1111 I I ' I 1 1 1 I I I I IIII I I I I I<br />

. 1.0 0. I 0.01 0.001<br />

Diom. Pore (mm)<br />

Figure 2b. Pore size distributi<strong>on</strong>s of soils<br />

Figure 2a. Grain size distributi<strong>on</strong> curves of used in frost heave tests, based <strong>on</strong> soil<br />

soils used in frost heave tests.<br />

moisture characteristic determinati<strong>on</strong>.<br />

1097

Experimental results of standard CRREL frost- Table 11. Test series and sample descripti<strong>on</strong>s<br />

heave tests <strong>on</strong> silty soil with three different €or laboratory frost-heave tests utilizing'<br />

polypropylene geotextiles inserted at mid- geotextiles inserted at midheight as capillary<br />

height in soil samples are presented in Figure barriers.<br />

1 (Chamberlain, 1986). The engineering<br />

properties of the fabrics tested in this<br />

series, as well as tests in the present study, Test Series s-le C<strong>on</strong>fiawti<strong>on</strong><br />

are listed in Table 1. Since Fibertex 200 and<br />

400 are identical except for thickness, these 1 1 Silt, no fabric<br />

preliminary results indicate the significance (reference for 2 - Silty sand, no fabric<br />

of fabric thickness in ability to mitigate series 2 and 3)<br />

frost-heave (bear in mind, however, that the<br />

fabrics are compressed when placed in the<br />

2 1 - Silt with Typar 3401<br />

sample mold). Pore size distributi<strong>on</strong>s of the<br />

fabrics and soils used were not determined in<br />

2 - Silt with Fibertex 400<br />

these tests. Grain size distributi<strong>on</strong> of the<br />

soil used is shown in Figure 2a.<br />

EXPERIMENTAL PROGRAM<br />

Five series of open system, unidirecti<strong>on</strong>al<br />

frost-heave tests were run in which n<strong>on</strong>woven<br />

geotextile fabrics were tested for their ability<br />

to mitigate frost heave. The procedure<br />

followed is known as the CRREL Standard Frost<br />

Heave Test, where the rate of frost penetrati<strong>on</strong><br />

is approximately 12.7 mm/day. See<br />

Chamberlain and Carbee (1981) for complete<br />

test details and Table I1 for test series and<br />

sample descripti<strong>on</strong>s.<br />

In the first three test series, soil specimens<br />

3 - Graves sand, 2 layers<br />

'were c<strong>on</strong>tained in tapered Plexiglas cells,<br />

Fibertex 200<br />

15.2 cm in length with a 14.0 cm inner<br />

diameter at the bottom a and 14.6 cm inner<br />

4 - Graves sand, 4 layers<br />

diameter at the top. The purpose of the taper<br />

Fibertex 200<br />

was to minimize side fricti<strong>on</strong> during frost<br />

heave. In the last two test series, sample<br />

c<strong>on</strong>tainers c<strong>on</strong>sisted of 15.2-cm-diameter<br />

cylinders made up six of Plexiglas rings lined<br />

with rubber membranes. This sample mold has fifth test series were replicate tests that<br />

been found to be more effective than the utilized a frost-susceptible sandy silt<br />

tapered molds in reducing side fricti<strong>on</strong> during (Graves sand) with eero, <strong>on</strong>e, two, and four<br />

frost heave (Chamberlain, 1987). Sample<br />

abutting layers of Fibertex 200 inserted at<br />

height before freezing was 15.2 cm.<br />

midheight of the samples.<br />

Based <strong>on</strong> results of previous work, Fibertex<br />

400 and Typar 3401 were the geotextiles<br />

selected for the fir.st three laboratory trials.<br />

Both of these fabrics have the same permittivity,<br />

defined as hydraulic c<strong>on</strong>ductivity<br />

divided by thickness: however, Fibertex 400 is<br />

ten times as thick as Typar 3401. Both<br />

fabrics, being composed of polypropylene<br />

fibers, are hydrophobic. The Fibertex is<br />

needle-punched and the Typar is heat-b<strong>on</strong>ded,<br />

and as such, it is likely that porosities and<br />

pore size distributi<strong>on</strong>s are very different<br />

3 - Silt with 2 layers<br />

. Fibertex 400<br />

4 - Silty sand with<br />

Fibertex 400<br />

3 1 - Layered sample: silty<br />

sand and silt separated<br />

by Fibertex 400<br />

4 & 5 1 - Graves sand, no<br />

(duplicate tests) geotextile<br />

2 - Graves sand, 1 layer<br />

Fibertex 200<br />

Grain size analyses and pore size distributi<strong>on</strong>s<br />

(calculated from soil moisture characteristics)<br />

for the soils used are presented i<br />

Figure 2. In all cases, the geotextiles meet<br />

U.S. Corps of Engineers filter fabric design<br />

criteria for the particular soil tested (CW-<br />

02215, 1986). The de8ign was d<strong>on</strong>e in an e€fort<br />

to minimize potential clogging of fabric<br />

during sample saturati<strong>on</strong> prior to freezing an<br />

is a factor that should be c<strong>on</strong>sidered in any<br />

field installati<strong>on</strong> of geotextiles €or such<br />

purposes.<br />

(Christopher and Holtz, 1985). The Fibertex<br />

and Typar were both tested in the same silt It is noted that about 10-1/2 hours after the<br />

and the Fibertex was also tested in a silty fifth frost heave test series was begun, a<br />

sand.<br />

very rapid freeze of all four samples occurr<br />

(within <strong>on</strong>e hour) due to a malfuncti<strong>on</strong> in <strong>on</strong><br />

The first frost-heave test series was a refer- of the glycol temperature baths. The samples<br />

ence series run <strong>on</strong> four soils without fabrics. were subsequently thawed, and the test was<br />

The sec<strong>on</strong>d and third series utilized two heav- restarted about 57 hours after the test was<br />

ing soils from the first series with geotex- originally started. The results of the tests<br />

tiles placed at midheight. A total of five may have been affected this by initial freezsainples<br />

with geotextiles were tested in the ing of the fabrics.<br />

first three test series: no duplicate samples<br />

were tested due to a shortage of soil materi- In all tests, the locati<strong>on</strong> of the fabric in<br />

al. After these initial tests, it was decided the samples was at midheight; this is approx<br />

to investigate further the effect of fabric mately 6-7 cm above the water table. However,<br />

thickness <strong>on</strong> frost heave. The fourth and the optimum locati<strong>on</strong> of geotextiles being use<br />

1098

as capillary breaks with respect to water<br />

table height and depth of frost penetrati<strong>on</strong><br />

should be-determined. Ongoing work at CRREL<br />

is c<strong>on</strong>sidering these factors. Results should<br />

be available later.<br />

40t<br />

o Silty Sand<br />

. w/Flbertex 400<br />

RESULTS AND ANALYSIS<br />

The results of the first three frost heave<br />

test series are presented in Figures 3, 4, and<br />

6. Fibertex 400 appears to be capable of reducing<br />

frost heave in the silt and silty sand<br />

tested as well as in a two-layered sample<br />

where the fabric separated two soils.<br />

Typar 3401 had an almost identical effect in<br />

reducing heave of the silt as did Fibertex.<br />

These results indicate that capillary behavior<br />

is influenced by thickness, pore structure,<br />

and hydrophobicity.<br />

C<strong>on</strong>sidering factors that affect capillarity,<br />

the height of capillary rise (he) in a tube<br />

is:<br />

0 200 300<br />

Time (hrs)<br />

Figure 4. Effect of a geotextile <strong>on</strong> the frast<br />

heave of a silty sand.<br />

where<br />

T, = surface tensi<strong>on</strong> of liquid,<br />

R =-radius of the tube,<br />

7 = unit weight of the liquid, and<br />

a = c<strong>on</strong>tact angle between the liquid<br />

and the tube.<br />

This relati<strong>on</strong>ship clarifies the role of surface<br />

properties in the capillary behavior of<br />

geotextiles. Although the soil and geotextile<br />

pore geometry is much more complex than that<br />

of a tube, it is obvious that when a geotextile<br />

has a wetting angle greater than that of<br />

soil particles, the geotextile experiences<br />

less capillary rise. The surface properties<br />

of fibers are affected by the polymers used as<br />

well as by the manufacturing process: unfor-<br />

50 I<br />

I I I I<br />

. w/Two Layers Flbertex 400 1<br />

I I I I I I<br />

0" IO0 200 300<br />

Tlme (hrs)<br />

Figure 3. Effect of geotextiles <strong>on</strong> the frost<br />

heave of a silt.<br />

1099<br />

tunately, not much is known about the wetting<br />

angles of engineering fabrics (Bell et al.,<br />

1980). Some measure or index of wetting angle<br />

would be useful to this research and, ultimately,<br />

to the proper selecti<strong>on</strong> of fabrics for<br />

use as capillary breaks. The threshold pressure<br />

(discussed below) divided by some characteristic<br />

pore size may be such an index of<br />

wetting angle of geotextiles.<br />

Relatively large pore sizes and wetting angles<br />

result in low unsaturated hydraulic c<strong>on</strong>ductivity<br />

of a layer and thus would inhibit the<br />

upward migrati<strong>on</strong> of water under freezing c<strong>on</strong>diti<strong>on</strong>s.<br />

If this is the case, the fabric behaves<br />

as a low permeability clay layer with<br />

respect to frost heave -- that is, the rate of<br />

water flow upward is too low to optimally feed<br />

a growing ice lens. In unsaturated hydraulic<br />

c<strong>on</strong>ductivity tests run <strong>on</strong> Fibertex 400, at a<br />

desaturati<strong>on</strong> pressure of 1.5 kPa, the hydraulic<br />

c<strong>on</strong>ductivity was 5 x cm/sec, and at a<br />

desaturati<strong>on</strong> pressure of 8.9 kPa, the fabric

was so dry that no moisture was in c<strong>on</strong>tact<br />

with the porous cups to give pressure readings<br />

(Henry, 1987). This is an extremely rapid<br />

rate of decrease in hydraulic c<strong>on</strong>ductivity<br />

with sucti<strong>on</strong> when compared with typical silty<br />

soils. A typical silt would have an unsatu-<br />

rated hydraulic c<strong>on</strong>ductivity of about lom6<br />

cm/sec at 10 kPa. Thus, these geotextilas<br />

could limit the rate of upward water migrati<strong>on</strong><br />

and reduce frost heave in unsaturated flow<br />

c<strong>on</strong>diti<strong>on</strong>s in freezing soils.<br />

A str<strong>on</strong>gly hydrophobic fabric may tend to trap<br />

water above its surface and cause "pending"<br />

problems. Allen et al. (1983) report that a<br />

"threshold pressure" of 7.5 cm of water was<br />

required to initiate flow through a particular<br />

melt-b<strong>on</strong>ded polypropelene fabric. (The<br />

threshold pressure, being related to pore size<br />

and fiQer uettability, also provides an indicati<strong>on</strong><br />

of hydrophobicity [Allen et al.,<br />

19831.) Allen (1986) reported p<strong>on</strong>ding problems<br />

<strong>on</strong> the same fabric when draining under<br />

low positive pressures.<br />

Based <strong>on</strong> results of Chamberlain (1986), the<br />

variati<strong>on</strong> of fabric thicknesses was expected<br />

to have more of an effect <strong>on</strong> tlm heave than is<br />

dem<strong>on</strong>strated in Figure 3. There were too many<br />

variati<strong>on</strong>s in experimental parameters and too<br />

few tests to draw any definite c<strong>on</strong>clusi<strong>on</strong>s<br />

yet. &%en the frozen samples were sliced in<br />

half vertically, it could be seen that the<br />

double layer of Fibertex 400 had moved upward<br />

in the sample and that an ice lens was present<br />

just beneath it. This was different, from the<br />

usual observati<strong>on</strong> that the fabric remained<br />

relatively horiz<strong>on</strong>tal or even slightly c<strong>on</strong>cave<br />

within the sample (see Figure 5) .<br />

Figure 6 shows the interesting result of<br />

having Fibertex 400 reduce heave in a layered<br />

soil specimen. In this case a coarser, marginally<br />

frost-susceptible silty sand was<br />

separated by the geotextile from a more frostsusceptible<br />

silt. This test result indicates<br />

that there is a possibility of using geatextiles<br />

with marginal base course material and a<br />

frost-susceptible subgrade to act both as a<br />

separator and a capillary barrier.<br />

The results of the fourth and fifth frost<br />

heave tests are shown in Figures 7 ana 8. One<br />

of the most interesting results is that <strong>on</strong>e<br />

layer of Fibertex 200 had na effect <strong>on</strong> the<br />

amount oL heave, whereas two layers appreciably<br />

moderated frost heave. The pore size<br />

distributi<strong>on</strong> curve for Graves sand reveals<br />

that 100% of the pore sizes in the soil are<br />

finer than the AOS (apparent opening size) of<br />

the Fibertex 200 (0.125 mn); thus, capillary<br />

barrier behavior is likely. In work d<strong>on</strong>e by<br />

Chamberlain (1986), <strong>on</strong>e layer of Fibertex 200<br />

did mitigate heave (see Figure 1): however, a<br />

different soil was used in that test. The<br />

soil used in these testa and the sail used by<br />

Chamberlain (1986) are both classified as<br />

sandy silt according to the Unified Soil Classificati<strong>on</strong><br />

System (see Figure 2 for the grain<br />

size distributi<strong>on</strong> curves). The AOS of Fibertex<br />

200 is less than the DS5 (the sieve size<br />

for which 85% of the soil remains) of both<br />

soils -- this being the design criteria of the<br />

10- 0<br />

I<br />

0 IO0 200 300<br />

Time (hrs)<br />

Figure 6. Effect of geotextile <strong>on</strong> frost heave<br />

of layered silty sand/silt sample.<br />

P<br />

Elapsed Tlme (hr)<br />

Figure 7. Effect of Fibertex.200 <strong>on</strong> the frost<br />

heave of Graves sand (fourth test series).<br />

Figure 8. Effect of Fibertex 200 <strong>on</strong> the frost<br />

heave of Graves sand (fifth test series).<br />

I<br />

-<br />

1100

U.S. Army Corps of Engineers for filter<br />

fabrics used in this soil type (CW-02215,<br />

1986). Other than the published AOS value, no<br />

informati<strong>on</strong> is available <strong>on</strong> the pore size distributi<strong>on</strong><br />

of Fibertex 200. If the actual<br />

range of pore sizes in the fabric were known,<br />

it would be possible to determine if a soil<br />

would be likely to clog the fabric as well as<br />

to compare the pore size distributi<strong>on</strong>s of the<br />

soil and fabric. It is possible that the<br />

Graves Sand, which has more fines near the AOS<br />

of the fabric than the Dartmouth Sand, has<br />

enough fines to substantially fill voids in<br />

<strong>on</strong>e layer of fabric, and thus reduce its<br />

capillary break behavior.<br />

Two layers of Fibertex 200 reduced heave by<br />

about 85% in the fourth test series and by<br />

<strong>on</strong>ly 25% in the fifth test series. In additi<strong>on</strong>,<br />

four layers of fabric were more effective<br />

frost-heave mitigators in the fourth<br />

series than the fifth. The anomalous test<br />

c<strong>on</strong>diti<strong>on</strong>s of the fifth test series have already<br />

been noted above. The freezing of the<br />

saturated fabric may have changed the pore<br />

structure or otherwise degraded the fabric.<br />

CONCLUSIONS<br />

Based <strong>on</strong> the current test results and their<br />

analysis, the following c<strong>on</strong>clusi<strong>on</strong>s are made:<br />

1. Certain n<strong>on</strong>woven polypropylene geotextiles<br />

show promise for use as capillary breaks in<br />

mitigating frost heave when placed horiz<strong>on</strong>tally<br />

above the water table. Factors that are<br />

likely to c<strong>on</strong>tribute to their success in<br />

laboratory tests include pore size, pore distributi<strong>on</strong>,<br />

pore structure, and the hydrophobicity<br />

of the fibers.<br />

2. Fabric thickness can significantly affect<br />

the ability of a fabric to mitigate frost<br />

heave. There appears to be an optimum thickness<br />

of fabric to reduce frost heave. This<br />

varies with soil type.<br />

3. When Fibertex 400 separated two frost-susceptible<br />

soils, it reduced heave in a laboratory<br />

test. This suggests the possibility of<br />

using geotextile both as a separator and as a<br />

capillary break with a marginal base course<br />

and a frost-susceptible subgrade.<br />

4. Future work should try to better define<br />

the roles of fabric characteristics such as<br />

pore size and pore size distributi<strong>on</strong> of the<br />

fabric compared to pore size distributi<strong>on</strong> of<br />

the soil fiber type (wetting angles), permeability,<br />

and placement in the soil body in<br />

determining capillary break behavior when<br />

placed in particular soils. Possible degradati<strong>on</strong><br />

due to clogging and freezing should also<br />

be studied. Work is <strong>on</strong>going at CRREL to better<br />

define geotextile characteristics and<br />

field c<strong>on</strong>diti<strong>on</strong>s that may influence capillary<br />

behavior.<br />

REFERENCES<br />

Allen, T (1986).<br />

Pers<strong>on</strong>al communicati<strong>on</strong>, Engineer.<br />

Washingt<strong>on</strong> State Department of<br />

Transportati<strong>on</strong>, Olympia.<br />

Allen, T, Bell, J R & Vins<strong>on</strong>, T S (1983).<br />

Properties of Geotextiles in Cold Regi<strong>on</strong>s<br />

Applicati<strong>on</strong>s, Transportati<strong>on</strong> <strong>Research</strong> Report<br />

83-6, 275 pp. Transportati<strong>on</strong> <strong>Research</strong><br />

Institute. Oreg<strong>on</strong> State University,<br />

Corvallis.<br />

Bell, J R, Hicks, R G, Copeland, J, Evans,<br />

G L, Cogne, J J, Mallard, P, Jahn, S & Lewis;<br />

M (1980).<br />

Evaluati<strong>on</strong> of Test Methods and Use Criteria<br />

for Geotechnical Fabrics in Highway Applicati<strong>on</strong>s,<br />

FHWA Report 80-021, June. Federal<br />

Highway Administrati<strong>on</strong>. Washingt<strong>on</strong>, D.C.<br />

Chamberlain, E J (1987).<br />

A freeze-thaw test to determine the frost<br />

susceptibility of soils, US Army Corps of<br />

Engineers Cold Regi<strong>on</strong>s <strong>Research</strong> and Engi-'<br />

neering Laboratory, Special Report 87-1,<br />

January, 90 pp.<br />

Chamherlain, E J (1986).<br />

Pers<strong>on</strong>al communicati<strong>on</strong>, <strong>Research</strong> Civil Engineer.<br />

US Amy Cold Regi<strong>on</strong>s <strong>Research</strong> and<br />

Engineering Laboratory, Hanover, N.H.<br />

Chamberlain, E J & Carbee, D L (1981).<br />

The CRREL Frost Heave Test, USA.<br />

Frost i Jord, November (22) 53-63.<br />

Christopher, B R & Holtz, R D (1985).<br />

Geotextile Engineering Manual, Federal<br />

Highway Administrati<strong>on</strong>, FHWA-TS-86-203.<br />

Nati<strong>on</strong>al Highway Institute, Washingt<strong>on</strong>, D.C.<br />

CW-02215 (1986).<br />

Geotextiles Used as Filters, Civil Works<br />

C<strong>on</strong>structi<strong>on</strong> Guide Specificati<strong>on</strong>, Dept. of<br />

the Army, Corps of Engineers.<br />

Henry, K S (1987).<br />

A Laboratory Investigati<strong>on</strong> of the use of<br />

Geotextiles to Mitigate Frost Heave and a<br />

Case Study of Potential Causes of Frost<br />

Heave, Master's Thesis, Civil Engineering<br />

Department, Northwestern University,<br />

Evanst<strong>on</strong>, Ill., 155 pp.<br />

Hoover, J M, Pitt, J MI Handfelt, L D &<br />

Stanley, R L (1981). Performance of Soil-<br />

Aggregate-Fabric Systems in Frost-<br />

Susceptible Roads, Linn County, Iowa.<br />

Transportati<strong>on</strong> <strong>Research</strong> Record (827) 6-14.<br />

Lothspeich, S (1988).<br />

Pers<strong>on</strong>al communicati<strong>on</strong>, Civil Engineer,<br />

Mirafi, Inc., Charlotte, N.C. 28224.<br />

Rengmark, F (1963).<br />

Highway Pavement Design in Frost Areas in<br />

Sweden, Highway <strong>Research</strong> Record No. 33,<br />

137-150.<br />

Taivainen, 0 A (1963).<br />

Preventive Measures to Reduce Frost Heave in<br />

Finland, Highway <strong>Research</strong> Record No. 33,<br />

202-216.<br />

Roth, H (1977).<br />

Filter Fabric for Improving Frost Susceptible<br />

Soils, Proceedings, <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> the Use of Fabrics in Geotechnics,<br />

Ecole Nati<strong>on</strong>ale des F<strong>on</strong>ts et Chausses,<br />

Paris, April, (1) 23-28.<br />

Department, Northwestern University,<br />

Evanst<strong>on</strong>, Ill., 155 pp.<br />

1101

VOLUME OF FROZEN GROUND STRENGTH TESTING<br />

L.N. Khrustalev and G.P. Pustovoit<br />

Laboratory of Engineering Ceocryology, Faculty of Geology,<br />

Moscow State University, Moscow, USSR<br />

sYNomIB<br />

An optimizati<strong>on</strong> approach to dettermking the volume of imzen ground strength<br />

testing is described which Involves minimisati<strong>on</strong> of the coats of euoh testing a d of possible<br />

losses due to its Insufficent volume. A derivati<strong>on</strong> is given fox the analytic relati<strong>on</strong>ship<br />

c<strong>on</strong>nsctlng optimal volume of tessing wtth,its cost, c<strong>on</strong>structi<strong>on</strong> project cost; and variability of<br />

permafrost characteristics. This relati<strong>on</strong>ship can form the bmis of sumey piapnbg.<br />

One of the fundamental principles of engfneeriDg<br />

geology 1 is *he principle of feed-back (Rater,<br />

19733. -. r. It demands that the soluti<strong>on</strong> of a geological<br />

problem should be made taking into<br />

account the aims and results of the corresp<strong>on</strong>ding<br />

engbeering problem soluti<strong>on</strong>. In recent<br />

years, Fncrsasing importance is attached to the<br />

methods for c<strong>on</strong>trw11ing the quality of geotechnical<br />

systems. For this reas<strong>on</strong> the quality<br />

factors of the system to be c<strong>on</strong>structed which<br />

are detemnhed from the appropriate moc!el,~hou~<br />

be taken into c<strong>on</strong>siderati<strong>on</strong> ih engineeringgeologic<br />

investigati<strong>on</strong>s. It is these which can<br />

and should ensure the feed-back menti<strong>on</strong>ed above.<br />

With these c<strong>on</strong>siderati<strong>on</strong>s in view, we are kohg<br />

to exambe a specific (but very important)<br />

problem of engineering geology that arises in<br />

any investigati<strong>on</strong>s: determinati<strong>on</strong> of the volume<br />

of ground testing, The approach we<br />

suggest here is general enough and can be applied<br />

to any testing, both of frozen and unfrozen<br />

gmunds. However, the problem being very complicated<br />

there is no general soluti<strong>on</strong> of it<br />

availabie in complete form that; can be used in<br />

practice, Such a aoluti<strong>on</strong> has been obtained by<br />

us In appltcati<strong>on</strong> to the use of permafrost,<br />

when characteristics of ground strength have<br />

the c<strong>on</strong>trollhg influence <strong>on</strong> the quality and<br />

stabilitg of structures. We shall try not to<br />

restrict the generality of our expositi<strong>on</strong>, but<br />

the final result that can form the basis of<br />

survey planning is given for the particular<br />

case menti<strong>on</strong>ed above and reflected Fn the title<br />

of our paper.<br />

The purpose of testing comm<strong>on</strong>ly c<strong>on</strong>sists Fn<br />

estimating the mean value of a characteristic x<br />

of the ground in a statistical populati<strong>on</strong> (an<br />

engineering-geologic element) and 3n providing<br />

the uncertainty of that estimate which does not<br />

exceed a fixed value wlth a fixed probability.<br />

If n trials have been made, the testing results<br />

are sampling mean x. and sampling variance<br />

E' , the emor being estimated usin@; the<br />

random quantity<br />

The methods tn use for atatistical. proceesSng<br />

of testing resulta are based <strong>on</strong> the assumpti<strong>on</strong><br />

of the normal distributi<strong>on</strong> law for charactertstics<br />

of the ground. In that cane the random<br />

quanti* (1) b B Student's t-dietributi<strong>on</strong>, md<br />

the numger of trials can be found from the<br />

equati<strong>on</strong><br />

b<br />

where tn-, (d) is quentile or the t-dintrlbuti<strong>on</strong><br />

with n-1 degree of freedom corm8 <strong>on</strong>ding<br />

to the c<strong>on</strong>fidence coelficl~t & ; and $ is<br />

relaelve emor in determining the oharacteristie<br />

to be ensured with probability d .<br />

The last faotor fn the equa.t;i<strong>on</strong> beoomes known<br />

<strong>on</strong>ly when data have been obtained and proeessed,<br />

that is, a volume of testiag depends <strong>on</strong> its<br />

re~ults, One can break thie vioioua circle by<br />

uahg the method of sudoesslve approximati<strong>on</strong>s<br />

c<strong>on</strong>sisthng of a mu1tist;age correcti<strong>on</strong> of mrvey<br />

planning in the courde of work.<br />

It has been suggeeted, for lnatance to recalculate<br />

the mean value of the obracierbtlo under<br />

study a8 new data come in, rrtop in$ the<br />

trials when the mea has been ssabdired masloo,<br />

1968) . However, to do this <strong>on</strong>e needs to<br />

establish a c<strong>on</strong>tinuous Xhk between the labom-<br />

tory and the field wit, a c<strong>on</strong>diti<strong>on</strong> that cannd<br />

always be satisfied. The most natural prooedw<br />

seem8 to be the practtce of a multir3tage sumeg<br />

in which the volume of testing at a aubsequent<br />

stage is determined from the results obtained<br />

at the previous <strong>on</strong>e. Fmbably , better schemes<br />

of successive approximati<strong>on</strong>s can be dev%ned but,<br />

when c<strong>on</strong>sidered within the framework of deterministic<br />

or *lsemiprobabilisticll c<strong>on</strong>Fepta usual.l$<br />

adopted j,n deai@, all such procedures encounter<br />

the hardly surmountable obstacle related to Faaetemnlnacy<br />

of the first factor b tho righthand<br />

aide of equati<strong>on</strong> (2).<br />

&O<br />

The questi<strong>on</strong> of c<strong>on</strong>fidence co$$ficient<br />

d<br />

1102

I<br />

guaranteeing the accuracy and reliability of<br />

desim indices remains open so far. The design<br />

codes $n foroe in the USGR recommend the value<br />

OL ~0.85 for permafrost. Some authors propose<br />

to relate this quantity to the type of c<strong>on</strong>atructi<strong>on</strong><br />

end survey stage (Kagan,'lp3) and point<br />

out specific probability values, sub8tantiating<br />

them with c<strong>on</strong>structi<strong>on</strong> practices. One has to<br />

admit, however, that in all casea the c<strong>on</strong>fidence<br />

probability la actually aesigned. One mag even<br />

assert that the established approach based <strong>on</strong><br />

the detemlnlsti<strong>on</strong> of c<strong>on</strong>fidence intervals and<br />

subsequent u8e of deterministic theoretical values<br />

of chaxacteriatfce In deai@ practice is<br />

incapable of a justified assignment of the probability<br />

.<br />

Indeed, a c<strong>on</strong>fidence probabtllty ia an inevitable<br />

c<strong>on</strong>sequence of the a~ificial mplaoement<br />

of random quantities by deterministic theoretical<br />

values and in principle it cannot be obbained<br />

as a result of ang kind of measusements<br />

because it depends <strong>on</strong> the purpose of such measurements.<br />

However, there is a <strong>on</strong>e-aide c<strong>on</strong>necti<strong>on</strong><br />

<strong>on</strong>ly between surveys a d their fFnaL objeetive<br />

- fhe struct.ure to be erxected, namely8<br />

the output data of surveys with a fixed reliability<br />

(o<strong>on</strong>fidence probability) axe the input<br />

<strong>on</strong>es for the structure desi= project. But data<br />

reliability is an input parameter for the BUP<br />

vsgs and cannot be detexmnnlned Lmlesa through<br />

the reliability of the final result, i.e. the<br />

structure stability . However, this reltabilitp<br />

cannot be estimated by using the deterministic<br />

approach. Therefore, the necessary feed-back<br />

the is absent, reliability<br />

thus making of the input It impossible data.<br />

to ensure<br />

When that fact is realized, this leads to 8<br />

different approach based <strong>on</strong> probabilistic c<strong>on</strong>cepte<br />

and ec<strong>on</strong>omic criteria. Its essence, as<br />

noted by Rata (19731, can be summarized in the<br />

following questi<strong>on</strong>: "ROW much will the guarantees<br />

cost UB and what do we risk if our guarantees<br />

are broken" The word "guarantee" here<br />

refera, not to accuracy of the data, but to<br />

stability of the structure, and the necessary<br />

feed-back is prvlded, not by an artificial c<strong>on</strong>fidence<br />

probability, but by actual ec<strong>on</strong>omic<br />

indices: survey cost and the cost of possible<br />

loases due to Insufficient volume of testing.<br />

By minimising the sm of them quantities,<br />

Cs 4 C1 -+minimum (3)<br />

<strong>on</strong>e can determine a volume of testing that is<br />

ec<strong>on</strong>omically optimal ,<br />

The arising optimizati<strong>on</strong> problem is attractive<br />

due to its apparent simplicity; soluti<strong>on</strong>s<br />

having been tried many timea. As far as we<br />

how, however, not; a single attempt has resulted<br />

in a closed soluti<strong>on</strong> free of artificial restricti<strong>on</strong>s<br />

(such as normative reliability levels<br />

eta.), which are essentially equivalent to<br />

assipkg a c<strong>on</strong>fidence probability in arbitrary<br />

mmner. The cause of this is as follows,<br />

Stability of structures is affected by a great<br />

many random factom, many of them being dependent<br />

<strong>on</strong> time; thus, the temperature regime of<br />

the foundati<strong>on</strong> playa the c<strong>on</strong>trolling role In<br />

c<strong>on</strong>structi<strong>on</strong> <strong>on</strong> permafrost. ' C<strong>on</strong>sequently, even<br />

when the accuracy and reliability of geologic<br />

data are identical, structures built in difiermt<br />

natural c<strong>on</strong>diti<strong>on</strong>s have differing degrees of<br />

stability guarantee. The loss cost ala0 var'188,<br />

being pfobabilistic in nature 'Ln adCSti<strong>on</strong> to<br />

this. The relati<strong>on</strong> between the accuracy of basic<br />

data, stability guarantee, and loss cost<br />

is indirect. It depends <strong>on</strong> processes, both deterministic<br />

and randam <strong>on</strong>es, that take place<br />

duriag interacti<strong>on</strong> of foundati<strong>on</strong> soil with the<br />

structure end the envir<strong>on</strong>ment. For this mae<strong>on</strong><br />

it is Smpoesible to provide a sound eatimati<strong>on</strong><br />

of losses outside of a c<strong>on</strong>aiate&t probabilieftic<br />

approach to the descripti<strong>on</strong> of the<br />

"foundati<strong>on</strong>-structure" system. Such an<br />

approach,as developed by the present authom,<br />

permits a sound formulati<strong>on</strong> and Boluti<strong>on</strong> of<br />

the optimizati<strong>on</strong> problem (3). We now examlne<br />

the basic Ideas and results of that approach.<br />

First of all, we have to admit that any Btabilitg<br />

criteri<strong>on</strong> formulated is a c<strong>on</strong>diti<strong>on</strong> imposed<br />

<strong>on</strong> random functi<strong>on</strong>s of time, such as loadhag<br />

<strong>on</strong> the foundati<strong>on</strong>, ita temperature,<br />

car iag capacity, and strain. A violati<strong>on</strong><br />

of zat c<strong>on</strong>diti<strong>on</strong>, called failure of the systsm,<br />

1s a random event which may or may not occur<br />

during a given interval of with aome probability<br />

. The probability of failureless<br />

functi<strong>on</strong>ing of a eystem regarded ae a functi<strong>on</strong><br />

of time interval i13 termed the life functi<strong>on</strong>.<br />

The functi<strong>on</strong> has the value <strong>on</strong>e for an Minitesimal.<br />

internal of time and tend6 to zero<br />

when the htemtal indefisitely increases.<br />

The liPe functi<strong>on</strong> depends 011 dl parameters<br />

(both Betermlabtic and stochastic) that c<strong>on</strong>tml<br />

structural stability. When 8 methemstXca1<br />

(stochastic) model of a system is being built ,<br />

lera significant parameters are identified and<br />

discarded, while the -remaining <strong>on</strong>es are used<br />

to c<strong>on</strong>struct a parameter-complex wFth the help<br />

of a stability criteri<strong>on</strong>; this is termed safety<br />

characteristic and is another argument in<br />

the lFfe functi<strong>on</strong> (the f kcst being the time)<br />

Thug for example, when permafrost is used as<br />

foun8ati<strong>on</strong> (according to principle I), the<br />

stability criteri<strong>on</strong> is the carrying capacity<br />

of the fomdati<strong>on</strong> whfch must always remain<br />

greater than the ioad <strong>on</strong> it. The normalized<br />

strength margln (the dlffemnce between the<br />

carrgbg eapacit and the load divided by the<br />

square root of tie variance of that difference)<br />

which is a random functi<strong>on</strong> of time must be poaitive.<br />

A peak in this functi<strong>on</strong> towarda the<br />

negative regi<strong>on</strong> meam failure of the system,<br />

while the probability of the absence of such<br />

peaks determines the life functi<strong>on</strong>. The safety<br />

characteristic Is the mathematical expectat i<strong>on</strong><br />

of normalized strength margin which is c<strong>on</strong>structed<br />

from the mathematical expectati<strong>on</strong>s of<br />

basic quantities (regarded as random functi<strong>on</strong>s),<br />

their variances and spectral characteristics,<br />

!The form of the hfe ,functi<strong>on</strong> P( 'c, 1 and<br />

the method for calculating the safety characterietic<br />

r were obtabed by us (Khruetalev<br />

and Pustovoit, 1904, 1985t Pustovolt, 1986),<br />

the latter paper giving more exact results,<br />

according to which<br />

The life functi<strong>on</strong> is a quantitative measure of<br />

the guarantee that a structure will be Btable<br />

under unfavorable random excitati<strong>on</strong>s. This<br />

1103

measud bas a merely mathematical meanhg however.<br />

The corresp<strong>on</strong>dbg measure invested with<br />

ec<strong>on</strong>omic c<strong>on</strong>tent has been called risk cost by<br />

us. It is defined as the mathematical expectati<strong>on</strong><br />

of loss due to premature failure of the<br />

foundati<strong>on</strong> and is expressed through the time<br />

derivative of the life functi<strong>on</strong> (the latter<br />

taken with the minus sign is the probability<br />

density of the the interval until the first<br />

failure). The meaning of risk cost is sufficiently<br />

exactly rerlected in its name. When<br />

stability (and the safety characteristlc) increases<br />

the coat decreases, but the hitla1 expense<br />

(foundati<strong>on</strong> c<strong>on</strong>structi<strong>on</strong>, preparati<strong>on</strong> of<br />

the foundati<strong>on</strong> base etc.) increases. The sum<br />

of the initial cost of the structure and risk<br />

cost is called the reduced total cost and we<br />

expect it to be a minimum at some value of the<br />

safety characteristic, Investigati<strong>on</strong>s show<br />

that this is the case, The value of safety<br />

characteristic (and the corresp<strong>on</strong>ding design<br />

soluti<strong>on</strong>) that provides the least reduced total<br />

cost is optimal from the ec<strong>on</strong>omic point of view.<br />

Any departure from It causes unjustified expensest<br />

either during c<strong>on</strong>structi<strong>on</strong> (strength<br />

margin is unjustifiably increased) or during<br />

use (premature repairs and rec<strong>on</strong>seructi<strong>on</strong> due<br />

to low stability).<br />

We have obzained a general eguati<strong>on</strong> for the<br />

optimal safety characteristic which, however,<br />

is little c<strong>on</strong>venient for routine practical<br />

calculati<strong>on</strong>s. In the particular case indicated<br />

(principle I), the specific form of functi<strong>on</strong><br />

(4) has permitted c<strong>on</strong>siderable simplificati<strong>on</strong>s,<br />

representing the equati<strong>on</strong> Fn the form<br />

: fo desired aptimal value of safety characteristic;<br />

V is tho combined coefficient of<br />

variati<strong>on</strong> that incorporatea variability in the<br />

carrying capacity and loads; E is an ec<strong>on</strong>omic<br />

coefficient characterizing relative cost of<br />

base and foundati<strong>on</strong>; ('Le is the durati<strong>on</strong> of<br />

structure use, in years. The method for calculating<br />

the coefficients E and F from basic<br />

design cost FnSormati<strong>on</strong> is described, in ths<br />

papers menti<strong>on</strong>ed above.<br />

The result8 obtained have aerved as a basis for<br />

solving problem (3) central to OUT paper,which<br />

we can at last c<strong>on</strong>alder, Let UB retmrn to expressi<strong>on</strong><br />

(I) and the notati<strong>on</strong> Fntroduced there.<br />

After surveyhg, we Fnaert sampling mean x. Fnto<br />

the calculati<strong>on</strong> and get from equati<strong>on</strong> (5) the<br />

optimal value of safety characteristic rb<br />

cosreap<strong>on</strong>ding to the least reduced total cost<br />

C, But the populati<strong>on</strong> mean x which will act<br />

<strong>on</strong> the structure ia different from xo, hence<br />

the actual value of safety characterisfic<br />

will be different from Ifb and the comesp<strong>on</strong>ding<br />

value c from C,. Since C, is the least<br />

possible cost of the structure designed for c<strong>on</strong>dtti<strong>on</strong>s<br />

determined by xo, we have C>Cm no<br />

matter what are the signs of x-x. or r- fo<br />

We explaln: if > ro , that means that the<br />

geological c<strong>on</strong>diti<strong>on</strong>s have turned out to be<br />

"better than we thought" and we had desiuned<br />

too costly foundati<strong>on</strong>s - the total cost tis<br />

increased aue eo hitla1 cost; tr 6.c- ro<br />

that would mean that the c<strong>on</strong>diti<strong>on</strong>s have turma<br />

out to be "wome than we thought", and the<br />

atability Is lower than deaijped - the cost<br />

has increased due to risk cost. In either<br />

case the difference AC = C - Cm meam extra<br />

cost (losses) because of inaccurate bowledge<br />

of soil characterlBt ice<br />

C<strong>on</strong>sider the above total cost 88 the functi<strong>on</strong><br />

C(x>. Xu that case C = C(x 1, and the loss<br />

A C is a functi<strong>on</strong> ofmthe diherence x-xG. If<br />

we expand that functi<strong>on</strong> into Taylor's series<br />

and c' eubskitute variable & for. x aC,oording .<br />

ko (I) we shall have<br />

where C(k) is the k-th derivative of C(x) + at<br />

pais* x0. The serisa begins with the sec<strong>on</strong>dorder<br />

term, because x,., Is a point where the<br />

reduced total coat is at; a minlmum, hence<br />

dl) = 0.<br />

Since E la a random quantity, the cost of<br />

possible loeses due to Fnsuufficlent volume of<br />

testing should be defiaed a~ the mathamatical<br />

expectati<strong>on</strong> 'of (6) t<br />

-<br />

(7 1<br />

"<br />

where P( E. 1 ia the diBtrlbuti<strong>on</strong> density of<br />

random quanttty (I), thae is, the t-distribut<br />

i<strong>on</strong>.<br />

As can be seen from (61, tha.htegral c a be ~<br />

calculated by summin the series composed of<br />

the moments of the d!!stributl<strong>on</strong>. We can<br />

reatrict ourselves to the first term of the<br />

series, because all odd momentrs of the t-distrlbuti<strong>on</strong><br />

are zero, while the sec<strong>on</strong>d term<br />

(corresp<strong>on</strong>ding to k=4) already differs from<br />

the first by a factor of order<br />

(4n)-I, <strong>on</strong>e<br />

can now write down the loas coat as a functi<strong>on</strong><br />

of volume of testing nt<br />

The dependence of survey cost <strong>on</strong> n is atraim<br />

fomard (it can be taken linear, far instance),<br />

so problem (3) is fully detemmined. Naturally,<br />

the difficulty menti<strong>on</strong>ed above st111 remains:<br />

(y md x. can be determined <strong>on</strong>ly after<br />

trials. It is involved in the problem itaeli<br />

ana cannot be obviated except by the method of<br />

successive appraximati<strong>on</strong>s, In the cam of<br />

multistage surveys c(2) ma IT should be<br />

calculated based <strong>on</strong> testing results obtained<br />

at the preceding stage (these quantities at<br />

the first stage can be detembed by analogs -<br />

we are antttled to c<strong>on</strong>sider that there ia<br />

1104

always some informati<strong>on</strong> <strong>on</strong> the subject of<br />

study); in such a case in expressi<strong>on</strong> (8) they<br />

should be Te arded as independent; of the deeired<br />

size n of the subsequent stage Substituting<br />

(8) in (31, differentiating wiih respect<br />

to n and equating the derivative to zero, we<br />

obtaL an equati<strong>on</strong> from which to detemlne the<br />

optimal volume of testing nt<br />

where<br />

The existence and uniqueness of the soluti<strong>on</strong><br />

follow from the fact that when n> 3 functi<strong>on</strong><br />

(IO) m<strong>on</strong>ot<strong>on</strong>ically decreases f~om dinity to<br />

zero, while all the other quantities In (9)<br />

are positive. 02 course, n<strong>on</strong>-integer values of<br />

n should be rounded. If (9) yields 8. value of<br />

n that is smaller than the volume of testing at<br />

the precedhg stage, further survey is not rehs<strong>on</strong>able<br />

ec<strong>on</strong>omically .<br />

!Po 8um u the general soluti<strong>on</strong> of the basic<br />

problem !k given by (g),. We have c<strong>on</strong>fined OUT<br />

c<strong>on</strong>aiderati<strong>on</strong> to the caee of teatjsg a single<br />

ground charaotesfstic in order not to encumber<br />

the logic with more technicalities, The problerm<br />

ia easily extended to cover the multidimensi<strong>on</strong>al<br />

caset: (9) is then reglaaed by a set of<br />

eguatl<strong>on</strong>s In the unknowns nl, n2 ,..., volumes . .<br />

of testing for various ground charactepistics.<br />

The soluti<strong>on</strong> could b.e found because we have<br />

succeeded in establishin a feed-backs from<br />

cost ana structure s t d i t y guarantees to sup<br />

veys. The feed-back has turned out to be complex<br />

enough, b terns of the derivative c(2)<br />

which c<strong>on</strong>centrates in Itself all informati<strong>on</strong> <strong>on</strong><br />

the interacti<strong>on</strong> of base grounds with the structure<br />

and the envir<strong>on</strong>ment, in additi<strong>on</strong> to bcorporating<br />

ec<strong>on</strong>omic indicea. This cbmplex'itg is<br />

partly the reas<strong>on</strong> why it has for ao l<strong>on</strong>g been<br />

not posslble to get the soluti<strong>on</strong> to thiB<br />

problem, although the relevant ideaa fldated in<br />

the air so to speakr the problem seems to be<br />

genuineig n<strong>on</strong>trivial and requires n<strong>on</strong>trivial<br />

methoda to solve it.<br />

Let us e<strong>on</strong>alder a% laat the better developed<br />

particular cam (principe I). Here the main<br />

object of testing fs strength characteristics<br />

of permafrost c<strong>on</strong>tmllhng a structure stability<br />

and functi<strong>on</strong> (4). Using equati<strong>on</strong> (5) and the<br />

relati<strong>on</strong> between reduced total cost and its aec<strong>on</strong>d<br />

derivative at the mlnimum, we express the<br />

latter in terns of known (computable) parameters.<br />

Denottng the derivative in the left-hand side of'<br />

(9) by C, (cost of a slngle trial), we get the<br />

equati<strong>on</strong><br />

The reader should pay attenti<strong>on</strong> to the general<br />

character of the relati<strong>on</strong>ship between the cos*<br />

00 a structure and optimal volume of testing:<br />

n- Eo, i.e. to the fact that volume of<br />

testing increases less rapidly than the COBC.<br />

Therefore, the larger the structure the smallsr<br />

is the cost of aurveys in the sum total of<br />

expeditures. This should be kept in mind by<br />

those dealing with ec<strong>on</strong>omics of c<strong>on</strong>structi<strong>on</strong>.<br />

The remaining parameters In the right-hand side<br />

of (11) relate the opthal volume of testing<br />

to a great number of regi<strong>on</strong>al and local factoret<br />

climate and ground c<strong>on</strong>diti<strong>on</strong>s, c<strong>on</strong>structi<strong>on</strong>al<br />

peculiarities ec<strong>on</strong>omic indices of '<br />

c<strong>on</strong>structi<strong>on</strong>, etc. 111 these factors should<br />

be taken Fnto account when plannin surveys in<br />

the permafrost z<strong>on</strong>e. Equati<strong>on</strong> (117 should<br />

serve here as a specific instrument of calculati<strong>on</strong>.<br />

'<br />

IZEFERENCEB<br />

Kagan A.A, (1973). Raschetnge pokazateli<br />

Piaiko-mekhaaichesklkh svoiatv gruutov ,<br />

IMpp. Leningrad: Stmiledat.<br />

Khrus!alev LON .(1 979). Tekhniko-ak<strong>on</strong>omicheskb<br />

raschet optimalnoi glubiny<br />

predpostmechnogo ottaivaniya vechnomerslykh<br />

gruntov pod zdmiem. - Osnovaniya<br />

fundamentg i mechanika gruntov, 3,<br />

19-23<br />

Rbrustalev, L.N. & Pustovoit, G.P. (1984). 0<br />

naznachenil koeffitsienta nadezhnosti pri<br />

raschete vechnomerzlykh osnovaniy sooru-<br />

zheniy . - Osnovaniy a f undamentg i mekha-<br />

nika gruntov, 5, 21-39.<br />

KhrustaLev, L.N. .!I, Pustovoit, G.P. (1985)<br />

Namachenie koeffitsienta nadezhnosti pri<br />

raschete vechnomerzlykh osnovanfy sooruzheniy<br />

s chiato ek<strong>on</strong>ornicheskoi otvetstvemostyu,<br />

- Osnovaniya fundamenty i<br />

mekhanFka grun%ov, 2, 26-22.<br />

h!aslov, N .N. (1968). Dlitelnaga uEltoichivostt<br />

i deformatsir smeshcheniya podpornykh<br />

soosuzheniy, 159 pp. Moskvar Energiya.<br />

Pustovoit G.P. (1986) i Propoz ustoichivosti<br />

zdaniy vozvodimykh 8 sokhraneniem vechnomerziogo<br />

sostoganba gruntov osnovmiya,<br />

V knige: Trudy Severnogo ofdeleniya NII<br />

osnovanty , vyp.5, 28-34, Sgktyvkar.<br />

Rats, M.V. (1973). Strukturnge modeli v behenernoi<br />

geologii, 214 pp. Mosknra: Nedra.<br />

1105

~<br />

MECHANICAL FROZEN ROCK-FILL PROPERTIES AS SOIL STRUCTURE<br />

Ya.A. Kr<strong>on</strong>ik, A.N. Gavrilov and V.N. Shramkova<br />

Branch <strong>Research</strong> Laboratory for Engineering Cryopedology in Power Plant C<strong>on</strong>structi<strong>on</strong> (BRLECPPC),<br />

Kuibyshev Civil Engineering Institute, Moscow, USSR<br />

smoPsIs<br />

Physical and mechanical properties of this qualitatively new material-fce-<br />

rock (st<strong>on</strong>e) system differ from those of the comp<strong>on</strong>ents forming it, that-dry rock fill and ice.<br />

The results of the experemental laboratory and field researches of the deformati<strong>on</strong> and strengkh<br />

propertyes of the frosen coarse-grained soils are discussed in this topic. Deformati<strong>on</strong> characte-<br />

ristic of the rock-fill relati<strong>on</strong>ship no!nograms of the temperature and ice c<strong>on</strong>tent to be used in<br />

the engineerirlg work are set in this repork too.<br />

INTRODUCTION<br />

index ( e ) varying from 0,43-0,48. The degree<br />

of ice c<strong>on</strong>tent; ( Gi ) varied from zero (air-dq<br />

mixture) to 1 (ice-rock mixture), negative<br />

temperatures (8 ) - from zero to -21OC below<br />

zero, which corresp<strong>on</strong>ds to the data of field<br />

When hydraulic structures 'are built in the Par<br />

North such material as coarse-grain soil is<br />

used which, however, gets saturated with ice<br />

when-moisture p&netrates it. Xde saturati<strong>on</strong> observati<strong>on</strong>s of thermo-regime of embankment<br />

may take place in a natural way-through c<strong>on</strong>den- darns built in the Far North. Under field c<strong>on</strong>-<br />

' sati<strong>on</strong> of moisture from interstitial pore air, diti<strong>on</strong>s deformability of zock fill was estimathrough<br />

infiltrati<strong>on</strong> of atnospheric precipita- ted having fracti<strong>on</strong> diameter up to Im and more,<br />

ti<strong>on</strong> which is observed, for instance, in rock- and density ( p ) of 2,2 t/m3. For this purearthfill<br />

dam, or it is formed artificially pose a piLot embankment was built or+ the site<br />

by pouring we-ber as, for instance, in building of the Kolima hyydrostati<strong>on</strong>,<br />

port hydraulic structures. The degree of natural<br />

ice saturati<strong>on</strong> of coarse-grain soil nay To define deforma*ive pro-pertiep, of the rnatevary<br />

midel;) being caused by anizotropy of the rial under laboratory c<strong>on</strong>diti<strong>on</strong>s compressi<strong>on</strong><br />

aaterial as well as by its being placod into devices were used placed in the working secthe<br />

Etructurc body in stages.<br />

ti<strong>on</strong> oi' the climatic chanber of KTK-800.<br />

Strength properties of frozen .coGse-grain<br />

Physico.1 2nd mechanical properties of this gua- oils were studed using direct shecar apparatus<br />

litativel; new 'laterial - ice-rock (st<strong>on</strong>e) sys- ~ $ 30 placed in the gal1el.y of the c<strong>on</strong>trol meatern<br />

- differ fro those of the comp<strong>on</strong>ents form- raring apparatus in the dam of the Kolima hyding<br />

it, thal; is dry rock fill and 1ce. This rostati<strong>on</strong>. The experirnen-bs were c<strong>on</strong>ducted in<br />

should be takel: into c<strong>on</strong>siderati<strong>on</strong> in design- the ,nethod described in (Vjalov S.S., 1978)<br />

ing and building hylrotechnical structures in which implies carq-ing or1 a series of tests<br />

the Forth. under c<strong>on</strong>dfti<strong>on</strong>s of ra id shear to define "instan'caneous"<br />

strength ti) follovred by a se-<br />

The object of the researches carried <strong>on</strong> was to ries of tests in applyin. direct ahear loading<br />

study the effect of the degree of ice satura- in stages, withat =O,l$i, the time of load<br />

ti<strong>on</strong> and negative tenperatwe <strong>on</strong> deformative apijlicati<strong>on</strong> <strong>on</strong> each stage (At) being 24 hours.<br />

and strength characteristics of the ice-rock<br />

material.<br />

Prol<strong>on</strong>ged strength ( 'IT ) for each test is defined<br />

by design using {he point where directi<strong>on</strong><br />

of the straight line of the raph of dependence<br />

of shear deformati<strong>on</strong>s ( # ) <strong>on</strong> a ting<br />

in coordinates hc-hk<br />

stress 6 = ST)<br />

!:XCHBNJSbI OF SUPPORT Uaximurn vertic stress ( 6' ) was 0,9.. .<br />

Experimental researches were c<strong>on</strong>ducted both in<br />

the BRLZCPPC and at the Kolima hydrostati<strong>on</strong><br />

now under c<strong>on</strong>structi<strong>on</strong>, the Kolima biotite granite<br />

seming as the material for studies. In<br />

studying deformability under laboratory c<strong>on</strong>diti<strong>on</strong>s<br />

homogeneous gruss-grsvel mixbure with<br />

fracti<strong>on</strong> diameter of 3-5 mm was used while in<br />

evaluating strenb%h a mixture formed by cruahing<br />

Larger pieces of hiotitu par:i-Le with fracti<strong>on</strong><br />

diawt;;r of' 3-10 1 1 1 wac tested. ".:e density<br />

of hard particle:; ( f tno soil tested<br />

!~RS<br />

with porosity<br />

v/ithin 1 ,&4 - 1 , 5<br />

1106<br />

Analysis<br />

The anal;/sis of the redults of testing deformqtive<br />

properties 01 frozen coarse-grain soil<br />

under compressi<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s allowed to use<br />

fracti<strong>on</strong>al-linear relati<strong>on</strong>ship (Tsytovich N.A.<br />

and other, 1981) to describc the development<br />

of deformati<strong>on</strong>s in time, verticd stress beins<br />

variable : . I* .A

where & - relative deformati<strong>on</strong>, - time ,8-<br />

acting stress,S;T*, ,!3 - empirical parameters<br />

depending, in general case, <strong>on</strong> and Gi (3).<br />

The dispersi<strong>on</strong> analysis made showed that the<br />

influence of ice c<strong>on</strong>tent ( Gi ) tells <strong>on</strong> the<br />

values of all the three empirxcal parameters<br />

while temperature ( 8 ) essentlalls effects<br />

<strong>on</strong>ly ( r- ) pax ter: The charactek of fhe +(a<br />

relati<strong>on</strong>ships Fy));F=#(&) =a Tzf &),P<br />

is shown in Fig.1 (a,b,c ,d) and for their<br />

descripti<strong>on</strong> relati<strong>on</strong>ships (2) - (4) are offer-<br />

Fig.1 Dependezce of deformctive reological<br />

paraxeters of gruss soils <strong>on</strong> temperature<br />

and degree of ice saturati<strong>on</strong>.<br />

The influence of G; up<strong>on</strong> strenzth properties<br />

of frozen gmss-gravel soil - internal fric-<br />

ti<strong>on</strong> angle ( ) and specific cohesi<strong>on</strong> ( C )<br />

at various temperatures and different modes of<br />

loading is shown in Fia.2.<br />

I<br />

It should be noted that fhe aarameters in ex-<br />

0.2 0.4 0.6 0.8 10<br />

Fig.2 Dependence of streneh properties of<br />

gruss-gravel soils <strong>on</strong> ice c<strong>on</strong>teat<br />

- prol<strong>on</strong>ged strength<br />

-.- x<br />

- prol<strong>on</strong>geg strewth of ice at e = ~ O C<br />

and -12 C respectively<br />

- instantaneous strength<br />

instantaneous stren th of ice at<br />

8 =-4OC and e -12 C respectively<br />

-*I--<br />

The analysis of the results obtained shows<br />

that increasing ice c<strong>on</strong>tenk leads to greater<br />

Values Of specific cohesi<strong>on</strong> (c) and that; the<br />

effect of ice c<strong>on</strong>tent ( G. ) <strong>on</strong> tkle internal<br />

fricti<strong>on</strong> angle ( qp<br />

in skying prol<strong>on</strong>ged<br />

strength is n<strong>on</strong>ambiguous; it increases with Gi<br />

gxowing up to ,4-0,5 a d then it falls down<br />

to values of when Gi.0 The reducti<strong>on</strong> of<br />

teaperatwe 8 c<strong>on</strong>tributes to the increase of<br />

qp and cp values of frozen grmss-gravel<br />

soils. Data of ice tests made following tine<br />

same nethod arc $resented, for co:nparis<strong>on</strong>, in<br />

Fig. 2.<br />

Such a-cilarncter of the effect of ice c<strong>on</strong>tent<br />

( GL) <strong>on</strong> deformative 2nd strength properties of<br />

ice-rock materials is obviously due to cryogennic<br />

texture of thc samples. In deep through<br />

freezing of not fully water-satuated coarsemain<br />

soil a fi1.n (crust) texture is formed.

~ reduces<br />

*<br />

, The developrlent of ice-cementing b<strong>on</strong>d presents<br />

repackinE of coarse-grain soil pcxticles,which<br />

deforrnability (Fig.lB) d raises<br />

stren&h and increases values and cp<br />

With all-side three-dimensi<strong>on</strong>al freezing of<br />

fully vater-saturated soil basalt texture is<br />

for:ned. C<strong>on</strong>tacts between fracti<strong>on</strong>s are broken<br />

and in this case strength and deformative propertizs<br />

of ice are primzrily resp<strong>on</strong>sible for<br />

!nechanical pro-,,er-t;ies of ice-i30ck material,<br />

which results in incl%ased deforaability para-<br />

:.letex 8 and reduced 'Pp . Specific cohesi<strong>on</strong><br />

vdth increased G; c<strong>on</strong>times to Zrow vihich indicates<br />

that the ctrengti; of ice-rock system<br />

has increased as a .,,ihole owin& to involving.<br />

into \-:ark r:ot or112 sepuate arts but also the<br />

ice formed.<br />

The result.:j of labor.ator, renearchGz aLLov: to<br />

evaluate zuali$ntivciy "enera1 regularities of<br />

the behaviour of icd-rock naterials in varying<br />

themo-moisture rcgize , ti-,:e and acting stress.<br />

To obtain aesigr :echanical characteristics of<br />

frozen rock :nass <strong>on</strong>e sho:lld nake use of thc results<br />

of field observati<strong>on</strong>s of pilot embankments<br />

or of kr~scale field tests. Thus, as<br />

8 reault of pocessing the data of field obserdef<br />

rm t'ops<br />

Y%$H+io,f,<br />

ana lo Eexlng<br />

into account the regularities of soil &formati<strong>on</strong><br />

obtained in IaboFabory experixen-bs (Fig.1)<br />

vzluea of reological pera:qeters of expxessi<strong>on</strong>s<br />

(l), (2), (3) for real rock mas were found<br />

which are presentad in Table 1.<br />

R%.pW o%l~~~%$<br />

. To decrease Labour-taking engineerirlg calculati<strong>on</strong>s<br />

a no:nogra:: V I ~ S built usin; the parameters<br />

obtained :or defining %he value of relative deformati<strong>on</strong>,<br />

taking into account the degree or<br />

ice c<strong>on</strong>tent, negative te:ggeratures, acting<br />

stress and tine factor shorn in Fig.3.<br />

The dekTee of creep xas defined using expres-<br />

TABLE I<br />

Values of el:lpirical coefficients of<br />

expressi<strong>on</strong>s (1) - (3)<br />

C; K 8' P T* b<br />

Fig.3. Nomogram for defining relative deformati<strong>on</strong>s<br />

of rock maw<br />

settlement made with the help of a nomogram<br />

for a real roclrfilZ structure and the settlements<br />

observed using the data of c<strong>on</strong>trolmeasuring<br />

device^. Besign parameters are given<br />

in Table 2.<br />

Design parameters<br />

settlements<br />

' TXBLE 2<br />

for estimating structure<br />

Calculati<strong>on</strong>s were made by apecially prepared<br />

programme in Fortran language for coilputer ES-<br />

1033. The solutioa vla8 a-mlyzed nith the help<br />

of a grnpher in staaddard "Grafor" laethod. The<br />

nomogran prese:ited here is of grid no.nogram<br />

class with equally spaced scales al<strong>on</strong>g coordinate<br />

axes. It gives a 10-20-fold saving of labour<br />

and ti% for calculati<strong>on</strong>s. %ith its help<br />

using field observati<strong>on</strong> date. of ice formati<strong>on</strong><br />

and temperature regime of various real rockfill<br />

hydrostmcturss, settlements were calculated<br />

and the resultz were coqared ivith the data of<br />

settlements observed in the field. This comparis<strong>on</strong><br />

indicates that the design forecast sufficiently<br />

well agrees (with discrepancy unto 17$)<br />

with the data of field obriervati<strong>on</strong>s. Fig.4, as<br />

an exaTnple, LJresent:; I). design Yorocact of<br />

I stage 0,26 0 0 0,099 p=2,.2 t/m3<br />

h=4,5 m<br />

I1 stage 0,25 0 0 0,054 p=1,2 t/m3<br />

111 stage 0,.75 1,0 -5 0,099<br />

511 stage 0,5 0 0 0,054 Layer is aaaumed<br />

to have<br />

thawed, watersaturated<br />

Y stage 0,5 0 0 0,054 Pd,2 t/m3<br />

1108

Fig.4. Structure settlements<br />

-*- design forecast data<br />

-- data gkven by c<strong>on</strong>trol-meaauring<br />

apparatus<br />

All the above allows to recommend that the<br />

described method, nomograms as well 4s the<br />

obtained deformative reological characteris-.<br />

tics of rock mass should be used for preliminary<br />

evaluati<strong>on</strong> of the deformative behaviour of<br />

embankmant structmes,<br />

REFERENOES<br />

Vja OVl 8.8. (1978). ReOlQgiCheSkye OSnOVY<br />

iehaaiky tov. MoskVa. Vystchaja shkola.<br />

str.448 (E%Ussiad<br />

Tey-bovich,. N.A., Kr<strong>on</strong>ik Ta.A., Gavrilov A.N.<br />

and Vorobyov E.A. (1981). Mechanical properties<br />

of frozen comae-grained soils. Engineering<br />

Geolow, 18 p.47-53. Elsevier Scientific<br />

Publishing Company, Amsterdam-Rinted<br />

in The Netherlands.<br />

Isytovich, N.A., Tir<strong>on</strong>ik Ja.A., Gavrilov A.N.,<br />

Dernin 1.1. (1983). Prognoz term<strong>on</strong>aprjagennodeformirovannogo<br />

soato janya gruntovyh SOOrugenij<br />

metodom k<strong>on</strong>echneh elementov. -oblemy<br />

geokryologii. bioskva. Nauka. -str.44-<br />

569<br />

1109

A STUDY OF FROST HEAVE IN LARGE U-SHAPED CONCRETE CANALS<br />

Li, Anguo<br />

Northwest Institute of Water C<strong>on</strong>servancy, Ministry of Water Resources and Electric Power,<br />

Yangling Town, Shanxi, People’s Republic of China<br />

SYNOPSIS<br />

Based <strong>on</strong> the data obtained from observati<strong>on</strong>s in an experimental canal and a test<br />

site during the three cold seas<strong>on</strong>s, the freezing and the frost heave behaviour of the subsoils beneath<br />

large U-shaped c<strong>on</strong>crete canals were analyzed and the methods for predicting the frost depth<br />

and the heaving rate are presented. It was found that frost heave will not occur if the water c<strong>on</strong>tent<br />

in the subsoils before freezing, is not greater than 15.1% and the normal frost heave force will<br />

be negligible if it is not greater than 17.3%. The normal frost heave force determined by a pressure<br />

transducer was 1.8 times greater than that determined by a dynamometer, <strong>on</strong> the everage, and was 5.5<br />

times greater in completely c<strong>on</strong>fined c<strong>on</strong>diti<strong>on</strong>s than in lining-c<strong>on</strong>fined c<strong>on</strong>diti<strong>on</strong>s. After revisi<strong>on</strong>,<br />

values of the normal frost heave force are suggested for engineering design under the same c<strong>on</strong>diti<strong>on</strong>s.<br />

INTRODUCTION<br />

‘To study the freezing and the frost heave behaviour<br />

in subsoils beneath large U-shaped c<strong>on</strong>crete<br />

canals and to study the feasibility and the methods<br />

for the design and the c<strong>on</strong>structi<strong>on</strong> of the<br />

linings, an experimental canal was built in<br />

Shanxi in 1981 and a site for observing frost<br />

heave of different buried plates (10, 30 and 50<br />

cm in diameter) was set up nearby. The experimental<br />

canal was located <strong>on</strong> the loess terrace,<br />

<strong>on</strong> the east bank of the Qian river with a northeast<br />

trend and without snow cover in winter so<br />

that the slopes, whether facing the sun or not,<br />

were observable. The soil was classified as a<br />

silt:, -lay with the ground water table at about<br />

the -’ I rPepth, The size of the test secti<strong>on</strong> of<br />

the c:. i was: 5 .1 m in depth, 7.17 m in width<br />

at the Lap, sides having a 3.2 m radius and 10’<br />

slope of the bottom. The lining was built with<br />

spray c<strong>on</strong>crete with a thickness of 10 cm and<br />

cross flexible seams every 2 m. On the southern<br />

bank of the canal, there was a site used fgr<br />

determining air temperatures, precipitati<strong>on</strong>,<br />

ground temperatures and frost depth. The water<br />

c<strong>on</strong>tent of the subsoils was obtained by drilling<br />

and sampling. The amounts of frost heave (or<br />

thaw settlement) in the subsoils and the displacements<br />

of canal lining were determined by dial<br />

gauges. The normal frost heave force was determined<br />

by both a pressure transducer (set up in a<br />

completely c<strong>on</strong>fined pattern) and a dynamometer<br />

(set up in completely c<strong>on</strong>fined and liningc<strong>on</strong>fined<br />

patterns). All of the instruments were<br />

set up normal to the surface at the observati<strong>on</strong><br />

points and calibrated before using. The observati<strong>on</strong><br />

period lasted €or three cold seas<strong>on</strong>s and<br />

all of the data showedalmost the same regularity.<br />

FREEZING BEHAVIOUR OF CANAL SUBSOILS<br />

In the U-shaped canal, each observati<strong>on</strong> point<br />

had its own slope orientati<strong>on</strong> and degree of<br />

direct sunshine, so that each point had its own<br />

difference between ground surface temperature<br />

and air temperature in winter, According to the<br />

observati<strong>on</strong>s, the ratios ‘li of the accumulated<br />

negative temperatures (the sum of the absolute<br />

values of temperaturesin the period f.rom the<br />

start of the cold seas<strong>on</strong> to the day of maximum<br />

frost depth) at the surface of each observati<strong>on</strong><br />

points to the freezing index (the sum of the<br />

absolute values of mean daily air temperature<br />

during the cold seas<strong>on</strong>), are shown in Table I<br />

and c<strong>on</strong>tours of this ratio, below the<br />

canal, at a particular times,are shown in Fig.1.<br />

TABLE I<br />

Values of rli and ai at Each Locati<strong>on</strong><br />

Within the Canal<br />

positi<strong>on</strong> Sol $1 $2 $3 S4 S5<br />

rl 4.00 3.45 2.55 2.58 2.81 3.27<br />

Cli 2.66 2.95 2.46 1.96 2.34 2.28<br />

positi<strong>on</strong> 0 N5 N4 N3 N2 N1 No1<br />

‘li 3.28 2.58 1.73 1.03 1.01 1.25 1.95<br />

ai 3.22 2.15 1.31 2.06 1.30 2.45<br />

The distributi<strong>on</strong> pattern of frost depth was in<br />

good agreement with that of surface temperature<br />

patterns. The frost depth was relatively deep<br />

at the southern slope which had a l<strong>on</strong>ger freezing<br />

period and relatively shallow at the northern<br />

slope which had a shorter freezing period<br />

1110

Fig.1 C<strong>on</strong>tours of Ground Temperature Ratios, q1<br />

(Jan 23, 1983, at 7 o'clock)<br />

and which usually underwent freezing at night<br />

and thawing during the day. The frost depth at<br />

the southern bank of the canal was greater than<br />

that at the northern bank.<br />

The relati<strong>on</strong>ship between the maximum frost depth<br />

and the atcumulated negative temperature at the<br />

surface and that between the maximum frost depth<br />

and the Ereezing index could be expressed respectively<br />

by:<br />

h = ai I='<br />

heave'which was expressed by a differential<br />

coefficient (K) defined as the ratio of the<br />

difference in the amount of heavebetween two<br />

points adjacent to each other, to the distance<br />

between the two points, expressed as a percent.<br />

The results showed that the locati<strong>on</strong>s with maximum<br />

frost heave were at 0 and S5 and the locati<strong>on</strong>s<br />

with the maximum value of K were at N5<br />

in 1981 and 1983. An excepti<strong>on</strong> was the locati<strong>on</strong><br />

54, which had both the maximum heave and<br />

the maximum K, in 1982. Although the differential<br />

coefficient of frost heave was greater at<br />

locati<strong>on</strong>s with the greater amount of frost heave,<br />

the locati<strong>on</strong>s with the maximum frost heave was.<br />

not coincident with the locati<strong>on</strong> of the maximum<br />

differential coefficient. Therefore, in the<br />

frost heave resistance design of canal linings,<br />

using the single parameter. i.e.the maximum<br />

frost heave, is not safe and another parameter,i.e.<br />

the maximum differential coefficient should be<br />

added.<br />

Relati<strong>on</strong>ship between frost heave and water .<br />

c<strong>on</strong>tent in subsoils<br />

Frost heave is caused by the phase change of<br />

water during freezing which results in volumetric<br />

expansi<strong>on</strong>. Thus the w,ater c<strong>on</strong>tent in subsoils<br />

is a dominant factor for frost heave. According<br />

to the data taken from observati<strong>on</strong>s,<br />

the relati<strong>on</strong>ship between the heaving rate (defined<br />

as- the ratio of the amount of frost heave<br />

to its corresp<strong>on</strong>ding frost depth, %) and the<br />

water c<strong>on</strong>tent in the subsoils before freezing<br />

and the relati<strong>on</strong>ship between the heaving rate<br />

and the water cantent Qf the subsoils during<br />

the freezing period could be expressed by a<br />

statistical method as follows:<br />

q = 0.3638 (W1-15.07)' (3)<br />

q = 0.5857 (W2-17.15) (4)<br />

where h the maximal frost depth, cm;<br />

Ii - the accumulated negative temperatures<br />

at surface, 'C day;<br />

ai - the+coefficient of frost depth,cm*<br />

'C-2 day (see Table I);<br />

Fo - the freezing index, ' C day;<br />

qi - the temperature ratio (see Table I).<br />

FROST HEAVE IN THE SUBSOILS OF THE CANAL<br />

Analysing the amount of frost heave <strong>on</strong> a cross<br />

secti<strong>on</strong> of the canal<br />

Observati<strong>on</strong>s during three years showed that the<br />

amount of frost heave at each observati<strong>on</strong> point<br />

of the canal was not directly proporti<strong>on</strong>al to<br />

the frost depth, but mainly depended <strong>on</strong> the<br />

moisture c<strong>on</strong>diti<strong>on</strong> of the subsoils. Where the<br />

water c<strong>on</strong>tent was higher , &here was a greater<br />

amount of frost heave, and vice versa. In order<br />

of the amount of frost heave goin,g from high to<br />

low the positi<strong>on</strong>s were: S5, 0, $4 and N5 im the<br />

first year. S1 and S2 in the sec<strong>on</strong>d: S3 and N4<br />

in the third.<br />

where q - the heaving rate, %;<br />

W1- the water c<strong>on</strong>tent of subsoils before<br />

freezing, X;<br />

W2- the water c<strong>on</strong>tent of subsoils during<br />

the freezing period. %.<br />

From equati<strong>on</strong>s (3) and (4) it can be seen that<br />

when the water c<strong>on</strong>tent in subsoils is 15.07%<br />

before freezing (Wol) and 17.15% in the freezing<br />

period (WO~), respectively, the heaving<br />

rate is equal tozero and no frost heave occurred<br />

in the subsoils. Both of the water c<strong>on</strong>tents<br />

menti<strong>on</strong>ed above are slightly lower than the<br />

plastic limit, Wp (18.4% <strong>on</strong> the average) and<br />

could be expressed by .<br />

Equati<strong>on</strong>s ( 3) and (4) could be used for .the predicti<strong>on</strong><br />

of frost heave in the same type of subsoils<br />

in a closed system and Bquati<strong>on</strong>s ( 5) and ,<br />

(6) could be used for the predicti<strong>on</strong> of the<br />

water 'c<strong>on</strong>tent.at which frost, heave occurs,' ,To<br />

prevent c<strong>on</strong>structi<strong>on</strong> from frost damage, the<br />

It is well known that frost damage in a canal fo1,lowing measures should be taken: draining,<br />

lining is mainly caused, by the differential frost cutting off any water supply and lowering the<br />

' 1111

water c<strong>on</strong>tent in the subsoils.<br />

Residual deformati<strong>on</strong> of frost heave<br />

The amount of frost heave could disappear completely<br />

in some situati<strong>on</strong>s, but usually it is<br />

<strong>on</strong>ly recovered partially during the thawing<br />

period by thaw settlement , and so there is<br />

some residual deformati<strong>on</strong>. If the deformati<strong>on</strong><br />

caused by frost heave disappeared completely in<br />

the thawing period, the lining would be safe,<br />

Otherwise, frost damage will be produced by the<br />

accumulated residual deformati<strong>on</strong>s, so the value<br />

of the residual deformati<strong>on</strong> should be the third<br />

parameter in the anti-frost design of canals.<br />

Table I1 shows the maximum frost heave and the<br />

values of the residual deformati<strong>on</strong> determined at<br />

the site.<br />

soils. Obviously, if there is no frost heave<br />

during subsoil freezing, or if the can'al lining<br />

could be deformed freely a normal frost heave<br />

force would not be produced. However this<br />

situati<strong>on</strong> is seldom met in practice. Fig.2<br />

shows the normal frost heave pressure vs.the<br />

elapsed time determined by the pressure transducer<br />

with a plate diameter of 30 cm. It can be<br />

It can be seen that residual deformati<strong>on</strong> existed<br />

everywhere. Where there was a great amount of<br />

frost heave, there was a great amount of residual<br />

deformati<strong>on</strong>, but there was no direct correlati<strong>on</strong><br />

between the two. The ratio of the<br />

residual deformati<strong>on</strong> to the amount of frost<br />

heave tended to increase with an increas.e in the<br />

elevati<strong>on</strong> of the observati<strong>on</strong> point (from point<br />

0 to Sl). It implies that the residual deformati<strong>on</strong><br />

not <strong>on</strong>ly depends <strong>on</strong> the maximum frost heave,<br />

but also depends <strong>on</strong> the canal secti<strong>on</strong> and the<br />

slope. The steeper the slope, the higher was<br />

the residual deformati<strong>on</strong>. For the U-shaped canal,<br />

the deformati<strong>on</strong>.caused by frost heave was not<br />

' totally recovered. Even though its value was<br />

very low, frost damage still could occur after<br />

,the canal came into operati<strong>on</strong> for a l<strong>on</strong>g period,<br />

so that anti-frost heave measures should be<br />

taken.<br />

NORMAL FROST HEAVE FORCE<br />

Forming and developine. processes of normal frost<br />

heave force<br />

Fig.2 Frost Weave Pressure vs. Elapsed<br />

Time a6 Determined by a Pressure<br />

Ttansducer<br />

TABLE I1<br />

Maximum Frost Heave and Maximum Residual Deformati<strong>on</strong>*<br />

positi<strong>on</strong> s1 s2 s3 s5 s4 0 N5 N4<br />

1981 1.30 0.99 1.03 3.29 9.43 11.94 8.78 0.91<br />

Ahmax 1982 6.40 7.08 3.78 8.24 7.60 7.41 6.29 1.93<br />

1983 5.89 3.42 1.50 5.54 14.00 11.02 11.23 1.64<br />

1981 0.81 0.78 0.30 1.28 5.01 ,3.55 0.103.10<br />

E 1982 5.09 6.33 2.89 4.28 2.36 1.73 1.88 0.75<br />

1983 4.88 1.96 1.03 2.21 7.47 5.51 9.12 0.40<br />

1981 62.31 79.19 29.13 38.91 53.13 29.73 35.25 10.99<br />

€/Ah 1982 79.53 89.41 76.46 51.94 31.05 23.35 29.89 38.86<br />

1983 82.85 57.31 68.67 39.89 53.36 50.00 81.21 24.39<br />

* Ahmax -maximum of frost heave,mm;<br />

E - residual deformati<strong>on</strong>, mm.<br />

1112

TABLE I11<br />

Maximum Normal Frost Heave Pressure in Different<br />

Locati<strong>on</strong>s of the Canal, kgf/cm’<br />

positi<strong>on</strong> S1 S2 S3 S4 S5 0 N5 N4<br />

by transducer<br />

completely c<strong>on</strong>fined<br />

1.71 0.98 1.22 1.08 1.64 1.77 1,21 0.29<br />

by dynamometer 0.97 0.86 0.41 1.28 0.92 0.90<br />

completely c<strong>on</strong>fined<br />

by dynamometer 0.11 0.12 0.25 0.11 0.37 0.02<br />

lining-c<strong>on</strong>fined-like<br />

increase in frost depth after c<strong>on</strong>t.inuous freezing<br />

occurred, reached a maximum after the maximum<br />

frost depth occurred, decreased sharply in<br />

the thawing period, and finally dropped down to<br />

a negative value lower than the values in the<br />

initial stage of subsoil freezing.<br />

Distributi<strong>on</strong> of normal frost heave force a lox<br />

the cross secti<strong>on</strong> of the canal<br />

From Table 111 it can be seen that the locati<strong>on</strong>s<br />

with the normal frost heave pressure from high<br />

to low are.as follows: 0, S5, S1 in the first;<br />

N5, $2, S3. S4 in the sec<strong>on</strong>d; N4 in the third<br />

and N 1, N2, N3 with the values equal to zero.<br />

Under completely c<strong>on</strong>fined c<strong>on</strong>diti<strong>on</strong>s, the normal<br />

frost heave force determined by the pressure<br />

transducer was 1.8 times higher than that determined<br />

by the dynamometer, <strong>on</strong> the average. When<br />

the dynamometer was used, the normal frost heave<br />

force under the completely c<strong>on</strong>fined c<strong>on</strong>diti<strong>on</strong><br />

was 5.5 times higher then that under the liningc<strong>on</strong>fined<br />

c<strong>on</strong>diti<strong>on</strong>, <strong>on</strong> the average.<br />

Factors affecting normal frost heave force<br />

The factors influencing the normal frost heave<br />

force could be the following: frost heave factors<br />

of the subsoils including soil properties, water<br />

c<strong>on</strong>tent, temperature and freezing rate; and the<br />

deformati<strong>on</strong> factors of the lining plates,including<br />

strut-ture, type of lining plates and their<br />

secti<strong>on</strong> size, etc.<br />

1) influence of moisture c<strong>on</strong>diti<strong>on</strong> of subsoils<br />

<strong>on</strong> normal frost heave fprce<br />

In the closed system, the normal frost heave<br />

force increased with an increase in the initial<br />

water c<strong>on</strong>tent greater than that initiating frost<br />

heave. For a plate diameter plate of 30 cm,<br />

the relati<strong>on</strong>ship between the maximum normal<br />

frost heave pressure and the water c<strong>on</strong>tent before<br />

freezing could be expressed by<br />

U= 0.2127 (Wl-17.28) (7)<br />

Where 0 is tge maximum normal frost heave pressure,<br />

kgf/cm .<br />

The water c<strong>on</strong>tent of the subsoils before freezing<br />

was 0.94 times the plas’tic limit.<br />

2) influence of heaving rate <strong>on</strong> the normal frost<br />

heave force<br />

In the closed system, the normal frost heave<br />

pressure increased with an increase in the heaving<br />

rate of the subsoils. The relati<strong>on</strong>ship<br />

between them could be expressed by<br />

0 = 1.164qO. 793 (8)<br />

Where ,q is the heaving rate, %.<br />

3) influence.of the area of the test plate <strong>on</strong><br />

normal frost heave force<br />

The relati<strong>on</strong>ship between the normal frost heave<br />

pressure and the area of the test plate could<br />

be expressed by<br />

(Y<br />

u uo<br />

+T (9)<br />

Where u - the determined value of the yormal<br />

frost heave pressure, kgf/cm ;<br />

o0 - the frost heave pressure of the soil<br />

column under the test plate, tgf/cm’;<br />

51 - the area of the test plate,cm ;<br />

a - the coefficient, kgf, which is the<br />

frost heave force of the soil body<br />

surrounding the c<strong>on</strong>fined soil column.<br />

Based <strong>on</strong>.the determined values of the normal<br />

frost heave force with different areas oE the<br />

test plates at the site, equati<strong>on</strong> (9) could be<br />

written in the following form:<br />

0 = 0,3568 + -<br />

62 .875<br />

L1<br />

From equati<strong>on</strong>s (9) and (10) ft can be seen that<br />

(lo is equal to 0.3568 kgf/cm , which is the<br />

normal frost heave pressure without the influence<br />

of the surrounding soils.<br />

Adopted values of normal frost heave force<br />

The values, shown in Table 111, of the normal<br />

frost heave pressure were obtained by different<br />

methods, The values, Oi, determined by the pressure.transducer<br />

were greater than their tru,e<br />

values so they could be used in engineering<br />

design until they are revised. First, c<strong>on</strong>sidering<br />

the c<strong>on</strong>fined c<strong>on</strong>diti<strong>on</strong>, the values of oir<br />

shown in Table 111, should be divided by 5.5<br />

1113

TABLE IV<br />

The Revised Values of the Normal Frost<br />

Heave Force aoi, kgf/cma<br />

positi<strong>on</strong> Stop S1 $2 s3 s4 0 N5 N4 N3<br />

' oi 0 0.249 0.143, 0.178 0.157 0.258 0.176 0.042 0<br />

Fig.3 The Secti<strong>on</strong>al Drawing<br />

of Dif ferent Types of Canal Lining<br />

for the revisti<strong>on</strong> from the completely c<strong>on</strong>fined<br />

pattern to lining c<strong>on</strong>fined patternaccording to<br />

the analysis menti<strong>on</strong>ed pre previously. Sec<strong>on</strong>d,<br />

c<strong>on</strong>sidering the area of the test plate ui should<br />

be divided by 1.249 to delete the influence of<br />

the area of the test plate because u/oo equals<br />

to 1.249 in equati<strong>on</strong> (10) when the plate diameter<br />

is 30 cm. After the revisi<strong>on</strong> mentioed above,<br />

the values Uoi, shown in Table IV, are those<br />

determined by the pressure transducer and without<br />

the influences of the plate area and the<br />

c<strong>on</strong>fined c<strong>on</strong>diti<strong>on</strong>s so that they could be used<br />

in engineering design.<br />

ANTI-FROST DAMAGE EFFECTIVENESS OF DIFFERENT<br />

TYPES OF LINING<br />

Fig.3 shows the type and the size of the linings.<br />

Cracks in the lining plates were checked for,4<br />

times from 1982 to 1984. The results showed<br />

that cracks occurred in all of the secti<strong>on</strong>s of<br />

the c<strong>on</strong>crete canal to different degrees (except<br />

for the st<strong>on</strong>e canal secti<strong>on</strong>) and the crack rate<br />

tended to increase year by year. The cracks were<br />

distributed horiz<strong>on</strong>tally from 1 to 3 m beneath<br />

the top of the canal and the crack width was<br />

less than 0.5 mm. The displacement at the locati<strong>on</strong><br />

of the cracks could not be observed. The<br />

order of the crack rate, from high to low, in th<br />

different types of lining shown in Fig.3, was<br />

as follows: type IV(50% in slope facing south<br />

and north)>type 1-1(28.6% in slope facing north<br />

and 19% in slope facing south) > type 11-3 (28.6%<br />

in slope facing north and 7.1% in slope facing<br />

south). The resistance to frost damage of the<br />

different types of the lining was in the following<br />

order: type IIV (the st<strong>on</strong>ed lining) was the<br />

best, type I1 (the c<strong>on</strong>crete lining),the sec<strong>on</strong>d<br />

best (am<strong>on</strong>g which, type 11-3 was better), type<br />

T the third best and type IV the worst.<br />

1114

(ii)<br />

(iii)<br />

'( iv<br />

'The distributi<strong>on</strong> of both frost depth<br />

and frost heave observed al<strong>on</strong>g the cross<br />

secti<strong>on</strong> of a canal lining was n<strong>on</strong>uniform.<br />

For similar canal c<strong>on</strong>diti<strong>on</strong>s,<br />

the frost depth at different locati<strong>on</strong>s<br />

could be calculated by equati<strong>on</strong> (1) or<br />

(2) according to whether the data are<br />

air temperatures or grodnd surface temperatures.<br />

The heaving rate could be<br />

calculated by equati<strong>on</strong> (3) or (4) according<br />

to the water c<strong>on</strong>tent in the<br />

subsoils.<br />

Where the water c<strong>on</strong>tent in the subsoils,<br />

before freezing, was less than 15.07%,<br />

frost heave did not occur, and where it<br />

was less than 17.282, the normal frost<br />

heave force was negligible. the ratio<br />

of the two water c<strong>on</strong>tents~menti<strong>on</strong>ed<br />

above to the plastic limit was 0.82.and<br />

0.94, respectively,<br />

The dominant design parameters for frost<br />

heave resistance,in canal linings<br />

should be the maximum frost heave, the<br />

differential coefficient of frost heave<br />

and the residual deformati<strong>on</strong>.<br />

The value and the distributi<strong>on</strong> of the<br />

normal frost heave force depends <strong>on</strong> the<br />

magnitude of the frost heave in the sub<br />

soilsand the deformati<strong>on</strong>of the lining<br />

'plates. The values of the normal frost<br />

heave force changed with the determinati<strong>on</strong><br />

method. The values determined by<br />

the pressure transducer were 1.8 times<br />

higher than those determined by the<br />

dynamometer, <strong>on</strong> the average, and the<br />

values determined in the completely<br />

c<strong>on</strong>fined pattern were 5.5 times higher<br />

than those determined in the liningc<strong>on</strong>fined<br />

pattern, <strong>on</strong> the avmage. The<br />

influence of the area of the test<br />

plates <strong>on</strong> the normal frost heave pressure<br />

could be expressed by equati<strong>on</strong> (10)<br />

and the values of the normal heave ,<br />

pressure, shown in Table IV, could be<br />

used for engineering design if the c<strong>on</strong>diti<strong>on</strong>s<br />

are the same.<br />

€racks occurred in each type of canal<br />

lining and the crack rate tended to<br />

increase year by year. Type I1 lining<br />

was better than type I and type IV was<br />

the worst.<br />

In the large U-shaped c<strong>on</strong>crete canals,<br />

the lining was not <strong>on</strong>ly uplifted but<br />

also displaced to the inside at -the<br />

slope facing north by the frost heave<br />

forces, and the displacement caused by<br />

frost heave was not totally recovered<br />

and so frost damage occurred. Measures<br />

for preventing frost heave in subsoils<br />

should be taken into account in the<br />

design and c<strong>on</strong>structi<strong>on</strong> of canals.<br />

Cheng Xlaobal, (lrtru). U ~ S C U S S ~ <strong>on</strong> O ~ ~ur zsrrrysa<br />

method for calculating the normal frost<br />

heave force at the bottom of foundati<strong>on</strong>s.<br />

J.of Water C<strong>on</strong>servancy and Electric Power<br />

(2).<br />

Orlov, B.O. (1962). Frost heave in fine-grained<br />

soils. Moscow, Publishing House of Sciences<br />

'l<strong>on</strong>g Changjiang and Cuan Fennian, (1985). Frost<br />

heave in soils and preventi<strong>on</strong> of frost<br />

damage in structures. Publishing House of<br />

Water C<strong>on</strong>servancy and Electric Power.<br />

1115

FROST HEAVING FORCE ON THE FOUNDATION OF A HEATING BUILDING<br />

Liu, H<strong>on</strong>gxu<br />

Beil<strong>on</strong>gjiang Provincial Institute of Low Temperature C<strong>on</strong>structi<strong>on</strong> Science, Harbin, China<br />

SYNOPSIS In order to investigate the frost heaving for,ce <strong>on</strong> the foundati<strong>on</strong> of heating<br />

building, an experimental heating building with various test foundati<strong>on</strong>s was c<strong>on</strong>structed at the Yanjiagang<br />

Frozen Ground Field Stati<strong>on</strong> nearby Harbin, Northeast China. Frost heaving force <strong>on</strong> the test<br />

foundati<strong>on</strong>s was observed for three winters from 1982 to 1985. The test results thaw that the frost<br />

heaving forces <strong>on</strong> the foundati<strong>on</strong>s of a heating building are much smaller than that <strong>on</strong> the similar<br />

foundati<strong>on</strong>s at a natural test site, which are not heated. Based <strong>on</strong> the test results, emperical<br />

equati<strong>on</strong>s for calculating the frost heaving forces <strong>on</strong> footings or pile foundati<strong>on</strong>s of a heating<br />

building were presented.<br />

INTRODUCTION<br />

Many investigati<strong>on</strong>s <strong>on</strong> frost heaving forces at<br />

natural sites in permafrost and seas<strong>on</strong>al frozen<br />

areas have been carried out (Liu, 1983; T<strong>on</strong>g,<br />

1983), but <strong>on</strong>ly a few studies are c<strong>on</strong>cerned with<br />

the frost heaving force <strong>on</strong> the outside of foundati<strong>on</strong>s<br />

of the heating buildings. This subject<br />

had been intensively investigated by the author<br />

and his colleagues through an experimental heating<br />

building at the Yanjiagang Field Stati<strong>on</strong><br />

nearby Harbin, Northeast China, for three winters<br />

from 1982 to 1985. This report is the summary<br />

of this work.<br />

FIELD EXPERIMENT<br />

mine the ground temperature and thaw depth of<br />

the aubaoil beneath the test building, 27 sets<br />

of thermal couples (No.1-27) and 11 detectors<br />

of frost depth (No.28-38) were embedded around<br />

the building foundati<strong>on</strong>s, as shown in Fig.1.<br />

Foundati<strong>on</strong>s A and C are square footings with a<br />

dimenti<strong>on</strong>'of lOOxl00 cm and a layer of 50-CUIthick<br />

underlying sand pad. Foundati<strong>on</strong> B is a<br />

strip footing with the dimenti<strong>on</strong> of 100 cm l<strong>on</strong>g<br />

by 60 cm wide. It was embedded 50 cm deep below<br />

natural ground surface <strong>on</strong> a 50-cm-thick sand pad.<br />

To eliminate the frost heaving force <strong>on</strong> the ends<br />

of the strip footing, subsoils around both ends<br />

of the footing were replaced with coarse-grained<br />

sand in a volume of 130 cm l<strong>on</strong>g by 30 cm wide<br />

and by 300 cm deep. Foundati<strong>on</strong> D is a grounding<br />

pile, which is 40 cm in diameter by 155 cm l<strong>on</strong>g.<br />

Site c<strong>on</strong>diti<strong>on</strong>s For comparis<strong>on</strong>, three seperate a,b foundat<br />

and d, which are similar to the test foundati<strong>on</strong>s<br />

The test site for the experimental heating<br />

A, B and D, respectively, were c<strong>on</strong>structed at<br />

building is located at the Yanjiagang Frozen<br />

the test site nearby the testing building where<br />

Ground Field Stati<strong>on</strong>, which is about 30 km South- no effect were induced bv the heatinn.<br />

west to Harbin. It is <strong>on</strong> the first terrace of<br />

-<br />

the S<strong>on</strong>hua River and has a thick layer of the<br />

Quaternary river and lake deposits.<br />

The maximum frost depth at this site is about<br />

155 cm. The subsoil beneath the experimental<br />

building is loam, with an average plastic limit<br />

of 20% and 1i.quid limit of 35%. The amount of<br />

frost heave occured at this site is 30.9 mm in<br />

maximum and 17.5 cm in minimum, with an average<br />

heaving ratio of 20%,bel<strong>on</strong>ging to a high frost<br />

susceptibility.<br />

C<strong>on</strong>structi<strong>on</strong> of the experimental buildin&<br />

The experimental heating building is composed of<br />

four rooms, wi.th a total area of 61.75 ma, as<br />

drown in Fig.1. It is suppurted by eight piles<br />

with a diameter of 40 cm by 10 m l<strong>on</strong>g (denoted<br />

as M1,M2, ... M8 in Fig.1). These piles are also<br />

used as the anchoring piles for the four test<br />

foundati<strong>on</strong>s A ,B,C and D (see Fig.1). To deter-<br />

TEST RESULTS<br />

The variati<strong>on</strong> of daily mean air temperature<br />

(ed), frost depth (H), frost heave amount (Ah)<br />

and ground water table at the test site from<br />

November 1982 to June 1983 were shown in Fig.2.<br />

The in-door m<strong>on</strong>thly mean air temperature (e) of<br />

each room of the experimental heating building<br />

for three winters from 1982 to 1985 was Listed<br />

in Table I. The observed values of the total<br />

frost heaving force <strong>on</strong> each pair of comparative<br />

foundati<strong>on</strong>s A and a, B and b, D and d and foundati<strong>on</strong><br />

C in two winters of 1983-1985 were illustrated<br />

in Figs. 3, 4, 5 and 6, respectively.<br />

Variati<strong>on</strong> of the frost depth and thaw depth<br />

beneath these foundati<strong>on</strong>s and at the test site<br />

were also plotted in these figures.<br />

1116

~<br />

I ! $6<br />

"t- ' * I<br />

Fig.1 Drawing of the Experimental Building: (a) air view: (b) 1-1 secti<strong>on</strong><br />

X-thermalcouples (No.l-27), 0-detectors for frost depth (No.28-38)<br />

M<strong>on</strong>thly Mean Air Temperature (a,<br />

TABLE I<br />

"C) Inside of Each Room of the Test Building<br />

0, "C in various years and rooms<br />

M<strong>on</strong>th<br />

1982-1983<br />

I I1 I11 IV<br />

1983-1984<br />

I I1 I11 IV<br />

11 20.5 18.7 15.8 14.3 17.7 16.8 13.2 10.5<br />

12 17.8 17.7. 13.5 11.4 13.0 15.5 11.4 9.1<br />

1 16.6 18.4 14.1 12.2 12.9 14.2 8.5 9.3<br />

2 17.9 19.0 15.1 12.4 15.7 19.7 14.2 11.5<br />

3 19.0 20.5 17.4 16.8 17.0 20.6 16.4 13.3<br />

4 20.0 21.8 20.0 19.0 19.7 20.6 17.8 17.2<br />

5 22.0 23.6 21.5 19.6 22.0 21.7 20.5 20.5<br />

I<br />

14.1<br />

16.8<br />

18.3<br />

18.4<br />

16.6<br />

15.7<br />

-<br />

1984-1985<br />

I1 111 IV<br />

14.8 13.7 11,2<br />

13.2 12.6 9.7<br />

11.8 11.4 9.1<br />

12.4 11.3 8.3<br />

13.2 12.3 9.3<br />

15.9 15.9 12.9<br />

- - -<br />

Room<br />

average<br />

Building<br />

average<br />

19.2 20.0 16.8 15.1 16.9 18.4 14.6 13.1 16.7 13.5 12.9 9.8<br />

17.7 15.7 13.2<br />

Note: I - Administrating room, 11- Dormitory,<br />

111- Office, IV - M<strong>on</strong>itoring room.<br />

1117

Fig.:! Variati<strong>on</strong> of Frost Heave (a), Daily Mean Air<br />

Temperature (b), Frost Depth (c) and Ground Water<br />

Table (d) with Time for the Natural Test Side<br />

16 -<br />

.E<br />

c.<br />

m o -<br />

u-<br />

Fig.3 Variati<strong>on</strong> of total frost heaving force and frost<br />

and thaw depthes for foundati<strong>on</strong>s A and a:<br />

1,2 Foundati<strong>on</strong> a in 1983-1984 and 1984;<br />

3,4 - Foundati<strong>on</strong> A in 1983-1984 and 1984-1985;<br />

5 -Thaw depth at the natural test site in 1984-1985;<br />

6,7 - Frost depth determined by thermalcouples No.27<br />

and 26; in 1984-1985;<br />

8 - Frost depth at test site in 1984-1985.<br />

c u<br />

\<br />

40 - \<br />

Fig.4 Variati<strong>on</strong> of Tota1,Frost Heaving Force and Frost<br />

and Thaw Depthes for Foundati<strong>on</strong>s B and a:<br />

1,2 - Foundati<strong>on</strong> b in 1983-198s and 1984-1985;<br />

3 - Foundati<strong>on</strong> B in B 1984-1985 ;<br />

4 -Thaw depth at the test site in 1983-1984;<br />

5,6 - Frost depth determined by thermalcouples No.4<br />

and 5 in 1983-1984;<br />

7 - Frost depth at test site in 1983-1984.<br />

ANALY.SIS AND DISCUSSION<br />

It is seen from Figs.3 to 6 that the frost heave<br />

forces <strong>on</strong> foundati<strong>on</strong>s a,b and d are much greater<br />

than that <strong>on</strong> foundati<strong>on</strong>s A,B,C and D. It means<br />

that the frost heaving forces acting <strong>on</strong> the outs,ide<br />

surface of the foundati<strong>on</strong>s of a heating<br />

building are much smaller than that <strong>on</strong> the foundati<strong>on</strong>s<br />

at a natural site, which are not heated.<br />

This is due to the fact that n<strong>on</strong>e or <strong>on</strong>ly a little<br />

of the subsoils inside the heated foundati<strong>on</strong>s<br />

were frozen.<br />

Note that the total frost heaving force measured<br />

<strong>on</strong> foundati<strong>on</strong> D is the smallest <strong>on</strong>e ((2xlO4N)<br />

am<strong>on</strong>g those values of frost heave force measured<br />

of the four testing foundati<strong>on</strong>s, as shown in<br />

Fig.5. This is accounted for: (a) This foundati<strong>on</strong><br />

is <strong>on</strong> the sunny side o f the building, 80<br />

that the frost depth of the subsoils around the<br />

foundati<strong>on</strong> is substantially reduced; (b) Their<br />

was a certain length of the pile foundati<strong>on</strong><br />

below the deepest frost fr<strong>on</strong>t, which provided a<br />

certain amount of anchoring force against frost<br />

heave due to the fricti<strong>on</strong> between pile and<br />

soils.<br />

1118

Fig.5 Variati<strong>on</strong> of total frost heaving force, frost<br />

depth and thaw depth for foundati<strong>on</strong>s D and d:<br />

1,2 -.Foundati<strong>on</strong> d in 1982-1983 and 1983-1984;<br />

3 Foundati<strong>on</strong> D in 1984-1985 ;<br />

4 Thaw depth at the teat site in 1982-1983;<br />

5,6 - Frost depth determined by thermalcouples<br />

No.17 and 18 in 1984-1985:<br />

7 - Frost depth at test site in 1982-1983.<br />

Fig.7 Scheme<br />

Foundati<strong>on</strong><br />

I<br />

of a Buried Shallow<br />

It is seen from Fig.4 that the maximum frost<br />

heaving force per unit length observed <strong>on</strong> the<br />

strip footing (foundati<strong>on</strong> B) is about 4.3~104<br />

N/m. It usually can not be balanced by the<br />

weight of a <strong>on</strong>e-floor building, but can be<br />

balanced by a two-floor building with a twobrick-thick<br />

wall and a few windows. In the<br />

senae of this, the possibility of suffering<br />

frost damage for the latter is much lowerthen that<br />

Fig.6 Variati<strong>on</strong> of total frost heaving force<br />

(I), thaw depth (2) and frost depth (3) for<br />

foundati<strong>on</strong>s C in 1984-1985<br />

for the former.<br />

It is seen from Figs.3 and 4 that the total<br />

frost heaving force <strong>on</strong> the pile foundati<strong>on</strong> is<br />

slightly greater than that <strong>on</strong> the strip footing<br />

(about 5.6x104N for the former and 4.3x104N €or<br />

the latter) at the same buried depth. However.<br />

the former load applied <strong>on</strong> the foundati<strong>on</strong>s by<br />

the building weight per unit base area is much<br />

(2.5-3 times) greater than the latter. That is<br />

to say using pile or column foundati<strong>on</strong> is favourable<br />

in taking its weight to balance frost heaving<br />

force. Furthermore. the c<strong>on</strong>tact area with<br />

frost, susceptible subsoils is much less €or pile<br />

or column foundati<strong>on</strong> than for strip footing. It<br />

means that the possibility of suffering uneven<br />

frost heave is much lower for the former than<br />

for the latter. It is, therefore, c<strong>on</strong>cluded<br />

that using pile or column foundati<strong>on</strong> instead of<br />

strip footing is favourable in preventi<strong>on</strong> of<br />

frost damage.<br />

In calculating the frost heaving force <strong>on</strong> the<br />

foundati<strong>on</strong>s of the outside wall of heating<br />

buildings, basides the effect of heating <strong>on</strong> the<br />

frost depth of base soil, the distributi<strong>on</strong> of<br />

frozen soil around the foundati<strong>on</strong>s should also<br />

be c<strong>on</strong>sidered. For the foundati<strong>on</strong> of a c<strong>on</strong>cave<br />

wall (shady corner), not <strong>on</strong>ly the frost depth<br />

of its base soil is shallow, but also <strong>on</strong>ly <strong>on</strong>e<br />

quater of its surrounding subsoil (i.e., outside<br />

of the foundati<strong>on</strong> ) is possible to produce frost<br />

heave. Whereas, for the foundati<strong>on</strong> of a c<strong>on</strong>vex<br />

wall (sunny corner), not <strong>on</strong>ly the frost depth of<br />

its base soil is deeper, but also about three<br />

1119

suar ters of its subso il will be able to produce<br />

irost heave. For the foundati<strong>on</strong> beneath the<br />

straight secti<strong>on</strong> of a wall, its situati<strong>on</strong> of<br />

suffering frost heave is between the above two<br />

cases,<br />

Based <strong>on</strong> the test results, the total normal<br />

frost heave force (PH) <strong>on</strong> the shallow foundati<strong>on</strong><br />

of a heating building with its buried depth less<br />

than maximum frost depth can be evaluated by<br />

where Pe is the normal frost heaving force <strong>on</strong><br />

a similar foundati<strong>on</strong> which is placed in the<br />

natural site; mu is the heating-effect coefficient<br />

reflectlng the distributi<strong>on</strong> of frozen<br />

soil around a heated foundati<strong>on</strong> and has the<br />

values of 0.25, 0.5 and 0.75 for c<strong>on</strong>cave,<br />

straight and c<strong>on</strong>vex wall, respectively; and m<br />

is the heating-effect coefficient related with<br />

the frost depth beneath the foundati<strong>on</strong>. It is<br />

estimated by<br />

ILTZ,-H<br />

mv = -<br />

2,-H<br />

REFERENCES<br />

Liu H<strong>on</strong>gxu, (1983). Calculati<strong>on</strong> of frostheaving<br />

forces in seas<strong>on</strong>ally frozen subsoils.<br />

Proceedings of 4th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>, Washingt<strong>on</strong>, D.C.,<br />

Nati<strong>on</strong>al Academy Press.<br />

T<strong>on</strong>g Changjiang and Yu Ch<strong>on</strong>gyun, (1983). <strong>Research</strong><br />

<strong>on</strong> the frost-heaving force of soils,<br />

Proceedings of 4th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g><br />

<strong>on</strong> <strong>Permafrost</strong>, Washingtou, D.C.,<br />

Nati<strong>on</strong>al Academy Press.<br />

where UT is a coefficient'related'to the effect<br />

.of heating <strong>on</strong> frost depth, Zo i s the so-called<br />

standard frost depth and H is the embedded depth,<br />

of the foundati<strong>on</strong> (Fig.7).<br />

The total tangential frost heaving force <strong>on</strong> a<br />

pile foundati<strong>on</strong> can be evaluated by<br />

in which the subsoils have the same meaning as<br />

above.<br />

CONCLUSIONS<br />

1. The circular or square (pile or column) foundati<strong>on</strong><br />

had a higher ability of anti-frost heave<br />

than strip footing.<br />

2. The planar c<strong>on</strong>figurati<strong>on</strong> of a heating building<br />

should be designed as simple as possible so<br />

as to greatly decrease the difference in the<br />

effect of heating <strong>on</strong> the foundati<strong>on</strong>s beneath<br />

outside wall of the building.<br />

3. Increasing the weight of a foundati<strong>on</strong> (e.g.,<br />

c<strong>on</strong>structing two-floor buildings rather than<br />

<strong>on</strong>e-floor bu-ildings) is an effective measure of<br />

anti-frost heave,<br />

ACKNOWLEDGEMENTS ,<br />

The author is grateful to his colleagues,Messrs<br />

Zhou Youchai, Wang G<strong>on</strong>gshan and Lj Kun for their<br />

c<strong>on</strong>tributi<strong>on</strong>s to this study.

FROST HEAVE IN SALINE-SATURATED FINE-GRAINED SOILS<br />

B.T.D. Lu, M.L. Le<strong>on</strong>ard and L. Mahar<br />

The Earth Technology Corporati<strong>on</strong>; 3777 L<strong>on</strong>g Beach Boulevard,<br />

P.O. Box 7765 L<strong>on</strong>g Beach, 90807 USA<br />

SYNOPSIS<br />

This study investigated the effects of salinity an the frost heave characteristics of four finegrained<br />

sails through a series of laboratary tests <strong>on</strong> specimens prepared at various combinati<strong>on</strong>s of<br />

salinity, temperature, temperature gradient, averburden stress, and density. The water intake and<br />

heave versus time results of specimens frozen from top down at Ereezing rates representative of arctic<br />

field c<strong>on</strong>diti<strong>on</strong>s indicated that increasing salinity, overburden stress and temperature gradient<br />

would decrease frost heave potential of atherwise highly frost susceptible fine-grained soils.<br />

Since grain size is a key factor in the farmati<strong>on</strong> of segregated ice lenses, and the soils tested had<br />

grain size characteristics mare optimal €or lens growth than many arctic soils, it is quite probable<br />

that there should exist a wide variety af soils with limited frost heave potential far c<strong>on</strong>structi<strong>on</strong><br />

use in the arctic offshore enviranment.<br />

INTRODUCTION<br />

Althaugh c<strong>on</strong>siderable work has been canducted<br />

regarding frast heave characteristics of sails,<br />

very limited data deals with the frost heave<br />

nature of saline-water-saturated material<br />

(Chamberlain, 1983). The presence of saline<br />

pare fluid significantly alters the freezing and<br />

water migrati<strong>on</strong> mechanisms and will, therefore,<br />

alter the frost heave process.<br />

The study described here was c<strong>on</strong>ducted as part<br />

of a Joint Industry <strong>Research</strong> Program (The Earth<br />

Technology Corporati<strong>on</strong>, 1983 and 1985) to provide<br />

fundamental data for designing arctic<br />

exploratian and productian islands.<br />

The specific objectives of the frost heave study<br />

were to assess the effect of salinity <strong>on</strong> the<br />

frost heave behaviar of a known frostsusceptible<br />

soil, evaluate the effects of overburden<br />

pressure and temperature gradient <strong>on</strong> the<br />

frost heave behavior of saline soil, and gage<br />

the effect of soil gradati<strong>on</strong> <strong>on</strong> the frast heave<br />

resp<strong>on</strong>se of saline soil. Ta meet the objectives,<br />

a laboratory frost heave test program was<br />

performed <strong>on</strong> specimens af four fine-grained<br />

sails including Manchester silt, sandy silt,<br />

clayey silt, and a mixture of arctic clay and<br />

silt samples. Tests were performed <strong>on</strong> specimens<br />

at various salinity, temperature, temperature<br />

gradient, overburden pressure, and durati<strong>on</strong> combinati<strong>on</strong>s.<br />

Test Materials<br />

Four fine-grained sail types were used in the<br />

testing pragram. Grain size curves for the four<br />

different materials tested are shown in Figure 1.<br />

As shown in Table I, a majority of the tests<br />

were performed <strong>on</strong> sail type 1 - Manchester silt,<br />

which was selected because it exhibits high<br />

frost heave potential when saturated with fresh<br />

IL<br />

NC<br />

1.0 0.9<br />

GRAIN SIZE IN MILLIMETER<br />

SILTOR CLAY<br />

HYDROMETER<br />

H<br />

FIGURE 1. GRAIN SIZE DISTRIBUTIONS-FROST HEAVE TEST SOILS<br />

water (Kaplar, 1974). Sail type 2 (sandy silt)<br />

and soil type 3 (clayey silt) were prepared by<br />

adding specif ic amounts of sand and clay to<br />

Manchester si It, respectively. Soil type 4 is<br />

an arctic clayey silt which was rec<strong>on</strong>stituted<br />

from bag samples of silt and clay remaining from<br />

a previous arctic offshore drilling program.<br />

'1121

TABLE I.<br />

Summary of Test Program<br />

1 1 1.63 0<br />

2 1 1.60 30<br />

3 1 1.68 10<br />

4 1 1.64 0<br />

5 1 1.62 24<br />

6 1 1.64 15<br />

7 1 1.65 20<br />

8 1 1.61 0<br />

9 1 1.61 19<br />

10 1 1.62 10<br />

11 1 1.65 10<br />

12 1 1.66 10<br />

13 1 1.61 10<br />

14 3 1.61 10<br />

15 4 1.80 26<br />

16 2 1.68 0<br />

17 3 1.61 20<br />

18 2 1.70 10<br />

19 2 1.70 20<br />

Note:<br />

-0.2<br />

-1.5<br />

-0.4<br />

-0.1<br />

-1.0<br />

-0.7<br />

-1.0<br />

-1.5<br />

-1.9<br />

-2.3<br />

0<br />

0<br />

-1.5<br />

-2.4<br />

-1.8<br />

-1.6<br />

-3.2<br />

-1.6<br />

-1.2<br />

-0.9 0.07 3.5 ,198<br />

-2.4 0.09 11.0 75<br />

-1.6 0.11 3.5 113<br />

-1.4 0.12 3.5 216<br />

-2.0 0.09 3.5 28<br />

-2.0 0.12 3.5 164<br />

-2.4 0.13 3.5 92<br />

-5.8 0.41 3.5 93<br />

-8.7 0.65 3.5 72<br />

-9.7 0.70 3.5 96<br />

-8.1 0.77 69.0 117<br />

-8.4 0.80 34.5 96<br />

-8.4 0.66 20.7 76<br />

-8.5 0.58 3.5 103<br />

-8.2 0.61 3.5 70<br />

-8.3 0.64 3.5 72<br />

-8.7 0.52 3.5 95<br />

-8.8 0.68 3.5 74<br />

-8.6 0.70 3.5 68<br />

CIRCULATIDN'<br />

GROOVE -STAND AOEMBLY<br />

85 b",T<br />

(1) Sail type 1 = Manchester silt; soil<br />

@ TEMPERATURE READOUT<br />

type 2 = sandy silt: soil type 3 =<br />

@ REFRIGERATION LINE<br />

clayey silt: and soil type 4 = arctic<br />

clavev silt<br />

"<br />

(2) Ydry = dry density; S * salinity;<br />

FIGURE 2. FROST HEAVE CELL DIAGRAM<br />

Tt = temperature at top of specimen;<br />

Tb = temperature at bottom of speci- accurate to within +O.l°C, with +O.Ol°C repeatamen;<br />

Tf = steady state temperature bility.<br />

gradient; atv = overburden pressure;<br />

and t = test durati<strong>on</strong>.<br />

EQUIPMENT AND PROCEDURES<br />

The frost heave test apparatus c<strong>on</strong>sists af a<br />

9.8 cm I.D. by 15.6 cm O.D. cylinder, instrumented<br />

alang the sides with thermistors.<br />

Details of the frost heave cell design and<br />

operati<strong>on</strong> are presented by Mageau and Sherman<br />

(1983). Figure 2 shows a schematic diagram of<br />

Sample Preparati<strong>on</strong><br />

Specimens for soil type5 I, 2 and 3 were prepared<br />

in 2.5-crn lifts in a compacti<strong>on</strong> mold using<br />

a 4.5-kg hammer dropping at a height af about<br />

45.7 cm. The surface of each lift was scarified<br />

prior to placing the next lift.<br />

The soil type 4 specimen was prepared by a<br />

slurry c<strong>on</strong>solidati<strong>on</strong> method. The soil slurry<br />

the test apparatus, thermistor arrangement, and : ~ ~ u ~ h ' e ~ x f f ~ e b ~ a ~ ~ ~ r ~ ~<br />

freezing and insulati<strong>on</strong> provisi<strong>on</strong>.<br />

The cell is insulated with 7.6 cm of polyurethane<br />

foam to minimize radial heat flaw into<br />

the sample. During testing, the cell is placed<br />

in a temperature-c<strong>on</strong>trolled envir<strong>on</strong>ment<br />

(industrial refrigerator). The temperature in<br />

the cold room is maintained as close to 0.3"C<br />

above the freezing point as possible. External<br />

coolant circulating baths supply a glycol-water<br />

mixture to the heat exchangers at adjustable<br />

preselected temperatures, allowing any desired<br />

gradient to be applied. Earlier testing during<br />

the research had shown very similar results when<br />

freezing specimens upward and downward. The<br />

coolant baths are capable of maintaining refrigerant<br />

temperatures to within +O.0ZoC.<br />

During each test, measurements of vertical<br />

displacement (heave), water intake, and temperature<br />

are recorded. Vertical heave is<br />

measured using a dial gage accurate tu 2<br />

0.0025 mm. Water intake is measured by reading<br />

a burette accurate to +0.2 mP,. Waterproof and<br />

pressure resistant theFmistors, calibrated prior<br />

to the test program in a zero point calibrati<strong>on</strong><br />

bux, are used for temperature measurements<br />

water c<strong>on</strong>tent in excess af the liauid limit of<br />

the soil. The slurry was then c<strong>on</strong>solidated in a<br />

specially deaigned cansolidometer under a<br />

surcharge ~f abaut 173 kPa for 5 days prior to<br />

testing.<br />

Saturatian, C<strong>on</strong>salidati<strong>on</strong>, and Isothermal<br />

Equilibrati<strong>on</strong><br />

The frost heave cell was assembled in the refrigerator.<br />

The specimens (except the arctic soil<br />

specimen) were saturated with salutian of the<br />

desired salinity. The specimens were saturated<br />

from the base with the tap drain line open.<br />

During saturati<strong>on</strong>, the specimens were subjected<br />

to the desired overburden pressure. Gravity<br />

flow gave degrees of saturati<strong>on</strong> between 90 and<br />

100 percent overnight for all samples except the<br />

clayey silt, which required a pressure of about<br />

7 to 10 kPa <strong>on</strong> the incoming water line to<br />

accelerate the saturati<strong>on</strong> process. Whenever a<br />

pressure was added to the incoming water line,<br />

an equivalent additi<strong>on</strong>al surcharge load was<br />

applied to the sample via the top pist<strong>on</strong> and<br />

dead weight system, After closing the bottom<br />

plate drainage line, the specimen was al'lowed tu<br />

set for 3 to 4 hours to stabilize pore<br />

1122

pressures. After saturati<strong>on</strong>/c<strong>on</strong>sulidati<strong>on</strong>, the<br />

tup and bottom heat exchanger plates were c<strong>on</strong>nected<br />

to the refrigerati<strong>on</strong> bath, set at 0.3T<br />

above the pore-fluid freezing point. Coolant<br />

was circulated for several hours tu induce a<br />

uniform temperature in the specimen.<br />

Freezinq Procedure<br />

For thq seven tests performed having cold side<br />

temperatures of 1 to 2OC below the freezing<br />

point, nucleati<strong>on</strong> was induced by supercooling<br />

the base of the sample at -15 to -17OC while<br />

m<strong>on</strong>itoring the change in height and base plate<br />

temperature. As so<strong>on</strong> as any change in height<br />

was observed, the circulati<strong>on</strong> lines were<br />

disc<strong>on</strong>nected from the -15 ta -17T bath and<br />

rec<strong>on</strong>nected ta the refrigerati<strong>on</strong> baths, which<br />

were preset to give the desirad boundary temperature<br />

for each test. For the remaining 12<br />

tests performed having cold side temperatures of<br />

5 to 7OC below the freezing point, nucleati<strong>on</strong><br />

inducement was not required.<br />

Temperature readings for top and battom plates<br />

and cell sidewalls were recorded periodically<br />

al<strong>on</strong>g with change in height and water intake or<br />

expulsi<strong>on</strong>. Data were typically recorded<br />

at times of 0, 1, 5, 10, 20, and 30 minutes; and<br />

2, 4, 8, 16, and 24 hours, and twice daily<br />

thereafter. Tests were c<strong>on</strong>tinued for 4 days or<br />

until the rate of frost heave appeared to reach<br />

steady state.<br />

After completi<strong>on</strong> of the test, the specimen was<br />

remaved fram the cell and examined. The lacati<strong>on</strong><br />

af the final ice lena, if any, and frost<br />

fr<strong>on</strong>t were measured. The moisture c<strong>on</strong>tent of<br />

both frozen and unfrozen parts was obtained for<br />

most specimens. Salinities of the frozen and<br />

unfrozen parts were determined for several<br />

samples by electrical c<strong>on</strong>ductivity methods.<br />

Test<br />

NO.<br />

-<br />

1<br />

2<br />

3<br />

4<br />

5<br />

6<br />

7<br />

8<br />

9<br />

10<br />

11<br />

12<br />

13<br />

14<br />

15<br />

16<br />

17<br />

18<br />

19<br />

Nates:<br />

TABLE I1<br />

Summary of Test Results<br />

So i 1<br />

Z Y L S D f h , h. Lf- ys 2<br />

1 8.1 1-04 1.8 0.07 1.1 -<br />

1 - 0.00 - 0.09 - 0.0<br />

1 1.27 4.0 0.11 3.9 3.5<br />

1 14.0 1.42 7.0 0.12 4.5 5.5<br />

1 - 0.05 - 0.09 - 0.0<br />

1 1.12 2.2 0.12 2.5 2.3<br />

1<br />

0.89 18.5 0.13 15.0 -<br />

1<br />

1.12 4.3 0.41 5.3 10.5<br />

1<br />

0.66 7,8 0.65 9.7 -<br />

1<br />

0.56 3.8 0.70 5.3 5.3<br />

1 - 0.20 3.6 0.77 1.6 2.8<br />

1 11.9 0.30 3.9 0.80 2.5 4.8<br />

1 - 0.36 6.0 0.66 3.9 9.1<br />

3 14.2 0.83 6.0 0.58 5.6 10.2<br />

4 13.5 1.17 12.8 0.61 12.5 5.0<br />

2 13.7 0.66 3.1 0.64 7.7 -<br />

3 14.5 0.48 6.5 0.52 6.1 12.3<br />

2 12.7 0.53 7.0 0.68 5.3 10.1<br />

2 11.7 0.30 3.6 0.70 2.5 5.1<br />

Df = observed frost penetrati<strong>on</strong> distance,<br />

cm; hs = total heave in 100 hours, cm;<br />

hs = steady state heave rate,<br />

cm/sec: Tf = steady state temperature<br />

gradient, OC/cm; V, = steady state water<br />

intake velocity, 10-7 cm/sec; SP =<br />

calculated segregati<strong>on</strong> potential, 10-6<br />

cm2/sec oc<br />

TEST RESULTS<br />

The results of this study are summarized in<br />

Table 11 and evaluated in the fallowing secti<strong>on</strong>s.<br />

Vertical Heave and Water Intake<br />

Figure 3 presents typical example plots of water<br />

intake and vertical heave versus time.<br />

Each plot fallows a typical pattern of dacreasing<br />

water intake and heave with time. .During<br />

the tests, the plots were c<strong>on</strong>tinually updated.<br />

When the rate of heave became c<strong>on</strong>stant (slope of<br />

heave versus time plot nat changing) or heaving<br />

stopped, the test was ended. The slopes of the<br />

curves during this steady-state period were<br />

calculated and recorded as the water intake<br />

velocity and heave rate. For tests ending prior<br />

ta 100 hours, the heave vexsu6 time curve was<br />

extrapolated at the steady-state slope to 100<br />

hours.<br />

Observed Frost Penetrati<strong>on</strong> and Ice Lens<br />

Format i<strong>on</strong><br />

TIME Ihwnl<br />

FIGURE 3. TYPICAL HEAVE AND WATER INTAKE VS.TIME.TEST N0.S<br />

No. 15 (arctic clayey silt) were c<strong>on</strong>centrated in<br />

a z<strong>on</strong>e about 1.0 cm thick, located 13 cm above<br />

sample bottom. Instead of a thin, c<strong>on</strong>tinuous<br />

ice layer, this z<strong>on</strong>e c<strong>on</strong>tained many small,<br />

disc<strong>on</strong>tinuous ice lenses. An ice Lens, 0.5 to<br />

0.75 cm thick, was noted at 14 cm above the bottom<br />

of the clayey silt specimen (Test No. 17).<br />

Visible ice lenses were observed in <strong>on</strong>ly three Frost penetrati<strong>on</strong> distances for samples with<br />

specimens (Test Nos. 14, 15, and 17). For Test clear frozen/un€rozen boundaries were measured<br />

Nu. 14 (clayey silt), the ice lens was about with a scale accurate to 0.25 cm. They ranged<br />

0.25 cm in thickness and located 14 cm from spe- from 8.1 cm in Test No. 1 to nearly 15.2 cm in<br />

cimen bottom. The ice lenses observed in Test Test No. 19 (Table 11).<br />

1123

Effect of Salinity <strong>on</strong> Heave<br />

For Manchester silt, the effect of salinity <strong>on</strong><br />

heave at 100 hours test durati<strong>on</strong> is dem<strong>on</strong>strated<br />

in Figure 4A . At shallow temperature gradients<br />

(0.09 to 0.13"C/cm), the Manchester silt saturated<br />

with distilled water heaved 1.42 cm in 100<br />

hours. With 10 g /i salinity, the heave reduced<br />

tn 1.27 cm which is about 89 percent of the<br />

distilled water sample heave. For salinity<br />

increased above 10 g/l, the heave progressively<br />

reduced. Above a salinity of 20 g/l, the<br />

100-hour heave suddenly drapped to nearly zero.<br />

At 24 g/ll salinity, the heave at 100 hours was<br />

0.05 cm (Test No. 5), and at 30 g/E, no heave<br />

was measured after 75 haurs. In the latter<br />

test, heave shutoff may have resulted from<br />

r<br />

a<br />

Combinati<strong>on</strong> of overburden pressure (11 kPa versus<br />

3.5 kPa in other tests) and salinity. For<br />

steeper temperature gradients (0.41 ta<br />

OVERBURDEN PRESSURE-O'v=3.6 kPa<br />

(except for the Salinity=3Oo/l spciman where (I,"= 11.0 kPa<br />

1.5<br />

TEMPERATURE GRADIENT4.09TO 0.13OC/Cm<br />

TEMPERATURE GRADIENT-0.41 TO 0.86 'Ckm<br />

3 1.0<br />

&<br />

YI<br />

><br />

d<br />

T<br />

a<br />

s<br />

0.5<br />

r<br />

0.0<br />

20<br />

40<br />

SALINITY (p/l)<br />

(A) MANCHESTER SILT<br />

1.5 -<br />

LEGEND<br />

TEMPERATURE GRADIENT=0.41-0.7O"ClCm<br />

OVERBURDEN PRESSURE-3.6 kPs<br />

MANCHESTER SILT (6% ssnd. 06% sild<br />

0 ClAYEY SILT 15% ssnd. 83%silt. 12% clayl<br />

SANDY SILT (33% sand. 87% silt1<br />

A ARCTIC SILT (27% rand. 54% silt, 19% clay)<br />

0.0 ! I I I<br />

4<br />

0 10 io 30 40<br />

SALINITY Ig/l)<br />

A<br />

IBI ALL FOUR SOIL TYPES<br />

FIGURE 4. -FROST HEAVE STUDY4ALlNITY EFFECT ON HEAVE<br />

AT 100 HOURS FOR VARIOUS SOIL TYPES<br />

1 I124<br />

0.70°C/cm), the effect af salinity at lower c<strong>on</strong>centrati<strong>on</strong>s<br />

(0 to 20 g/R) was similar to that at<br />

shallower gradients. However, the salinities<br />

tested at the steeper temperature gradients were<br />

not high enough to reduce heave to zero.<br />

As shown in Figure 4B, both clayey silt and<br />

sandy silt exhibited the same trend of reduced<br />

heave at higher salinities. Although heave<br />

"shutaff" salinities were nat reached for<br />

clayey silt and sandy silt, the percent reducti<strong>on</strong>s<br />

in heave with salinity within the range af<br />

salinities tested were greater than for<br />

Manchester silt (40 to 50 percent compared to 35<br />

to 40 percent). Heave at 100 hours was reduced<br />

to less than 0.5 cm for both soils at 20 g/R<br />

salinity. It would be expected that, at slightly<br />

higher salinities (25 to 30 g/k), nearly zero<br />

heave would accur.<br />

Effect of Overburden Pressure <strong>on</strong> Heave<br />

Test Nos. 11 ta 13 tested the effect of overburden<br />

pressure <strong>on</strong> the heave potential of highly<br />

frost-susceptible Manchester silt. As with nansaline<br />

samples, increased overburden pressure<br />

reduced the hFave observed for Manchester silt<br />

with 10 g/.e salinity (Penner and Ueda, 1977;<br />

K<strong>on</strong>rad and Mosgenstern, 1983). Heave at 100<br />

hours reduced by more than 42 percent as overburden<br />

pressure increaaed from 20.7 to 69.0 kPa<br />

(Table 11). The greatest reducti<strong>on</strong> in the heave<br />

occurs in the 0 ta 20.7 kPa range.<br />

Effect af<br />

Sail Gradati<strong>on</strong> <strong>on</strong> Heave<br />

The test results in Table I1 show that the sandy<br />

silt (33 percent sand, 67 percent silt) heaved<br />

less than the more fine-grained soils at each<br />

salinity level. Also, clayey silt heaved<br />

slightly less than Manchester silt.<br />

The <strong>on</strong>e arctic soil specimen (27 percent sand,<br />

54 percent silt, 19 percent clay) tested gave<br />

unexpected high heave despite a post-test salinity<br />

of 26 g/R in the frozen portian of the<br />

sample (Test No. 15). The arctic soil specimen<br />

was pkepared by slurry c<strong>on</strong>solidati<strong>on</strong> which may<br />

have caused heave results differing from those<br />

of all other samples prepared by wet tamping.<br />

Also, the clay c<strong>on</strong>tent in the arctic clayey silt<br />

is significantly higher than that in the other<br />

three sails. Thus, the higher frost heave<br />

potential may be a result of either higher clay<br />

c<strong>on</strong>tent or specimen preparati<strong>on</strong> method. Further<br />

investigati<strong>on</strong> is needed to c<strong>on</strong>firm this.<br />

An increase in the coarse fracti<strong>on</strong> c<strong>on</strong>tent tends<br />

to decrease heave, as expected. For samples<br />

tested at 0 g/R salinity, the additi<strong>on</strong> of 33<br />

percent fine-medium sand tu the Manchester silt<br />

reduced the frost heave at 100 hours by about 40<br />

percent, while at salinities near 20 g/R, the<br />

reducti<strong>on</strong> was about 55 percent. More testing of<br />

granular soils with varying fines c<strong>on</strong>tents would<br />

be needed to establish clearer relati<strong>on</strong>ships<br />

between gradati<strong>on</strong> and frost heave potential.<br />

Effect of Temperature Gradient <strong>on</strong> Heave<br />

For freshwater Manchester silt specimens, a temperature<br />

gradient increase from 0.12 to<br />

0.41°C/cm reduced heave by 22 percent (Figure<br />

4A). A similar effect is shown for specimens<br />

saturated with saline (20 g/L) pore fluid.

Effect of Salinity <strong>on</strong> Water Intake Velocity and<br />

Steady-State Heave Rate<br />

For Manchester silt specimens tested at Shallow<br />

temperature gradients (less than 0.16'C/cm), a<br />

substantial decrease in water intake velocities<br />

occurs with increasing saline c<strong>on</strong>tents (Table 11).<br />

The trend is quite similar to that observed for<br />

100-hour heave versus salinity (Figure 4A).<br />

Water intake velocities also decreased substantially<br />

with increasing salinity for sandy silt<br />

specimens. At 20 g/L saline c<strong>on</strong>tent, the water<br />

intake velacity was down to 2.5 x 10-7 cm/sec<br />

compared to 7.7 x 10-7 cm/sec for the nansaline<br />

specimen (a reducti<strong>on</strong> of abaut 67 percent).<br />

Steady-state heave rates were alsa observed to<br />

decrease with increasing salinity for both<br />

Manchester silt and sandy silt (Figure 5). The<br />

reductian in heave rate from that for n<strong>on</strong>saline<br />

samples was nearly 70 percent far Manchester<br />

silt at 15 g/L salinity and about 55- percent for<br />

the sandy silt at 20 g/t salinity.<br />

10.6<br />

7.0<br />

3.5<br />

0<br />

SALINITY,pll<br />

FIGURE 6. SALINITY EFFECT ON STEADY-STATE HEAVE RATE<br />

DISCUSSION<br />

Although c<strong>on</strong>siderable effort has been put forth<br />

to understand the frost heave phenomen<strong>on</strong>, the<br />

effect of salinity <strong>on</strong> frost heave behaviar has<br />

received limited attenti<strong>on</strong>. Chamberlain (1983)<br />

studied the influence of salinity <strong>on</strong> two soils,<br />

Morin clay and Dartmouth sand. For Morin clay<br />

saturated with distilled water, Chamberlain<br />

found steady-atate heave rates of 2.3 x 10-7<br />

cm/sec, which compares well with the heave rate<br />

of abaut 0.7 x 10-7 cm/sec found here for<br />

Manchester silt. Increasing the salinity to<br />

34.6 g/ll reduced the Morin clay heave rate by<br />

abaut 60 percent compared with a 40 percent<br />

reducti<strong>on</strong> associated with an increase to 20 g/a<br />

for the Manchester silt. Similar percent reducti<strong>on</strong>s<br />

in heave at 100 hours were observed for<br />

both material types, for the same increase in<br />

salinity. Far Dartmouth sand (4 percent gravel,<br />

56 percent sand, and 40 percent silt and clay),<br />

Chamberlain reported a 75 percent reducti<strong>on</strong> in<br />

heave rate and a 49 percent reducti<strong>on</strong> in heave<br />

at 100 hcrurs associated with pore-fluid salinity<br />

increasing from 0 to 35.7 9/11. He also<br />

dem<strong>on</strong>strated the marked differences in moisture<br />

c<strong>on</strong>tent profiles of samples with and without<br />

salinity. The results of moisture c<strong>on</strong>tent and<br />

salinity measurements after the tests in this<br />

program-also c<strong>on</strong>firmed such findings.<br />

A mechanistic theory of ice lens formati<strong>on</strong> and a<br />

method fur evaluating frost heave behavior in<br />

fine-grained soils has been developed by K<strong>on</strong>rad<br />

and Morgenstern (1981, 1982, 1983, 1984). The<br />

method relates the rate of heave under steadystate<br />

C<strong>on</strong>diti<strong>on</strong>s to the potential to develop<br />

segregated ice, termed the "segregati<strong>on</strong> potential"<br />

(SP) which equals the ratio crf the heave<br />

rate, hs to the temperature gradient, Tf.<br />

Values of segregati<strong>on</strong> potential were determined.<br />

for the present testing program, and are tabulated<br />

in Table 11. The results indicate the<br />

segregati<strong>on</strong> potential decreases with increasing<br />

salinity. The observed effect of salinity <strong>on</strong>.<br />

segregati<strong>on</strong> potential is very similar to that <strong>on</strong><br />

heave after 100 hours, previously Shown in<br />

Figures 4A and 4B.<br />

The effect of steady-state temperature gradient<br />

<strong>on</strong> segregati<strong>on</strong> potential is also shown an Table<br />

11, where it can be observed that segregati<strong>on</strong><br />

potential decreases with increasing temperature<br />

gradient. The effect af Overburden pressure <strong>on</strong><br />

segregati<strong>on</strong> potential for saline (10 g/a)<br />

Manchester silt specimens shows decreasing<br />

segregati<strong>on</strong> potential with increasing pressure.<br />

K<strong>on</strong>rad and Morgenstern (1983) developed the<br />

following relati<strong>on</strong>ship to account for the effect<br />

of overburden pressure, Pel <strong>on</strong> SP:<br />

SP = SP,<br />

where SPO is the segregati<strong>on</strong> potential for zero<br />

overburden pressure and "a" is the empirical<br />

c<strong>on</strong>stant.<br />

When applied to a best fit of test results for<br />

saline (10 9/11) Manchester silt specimens, the<br />

above analysis yields values €or SPo = 0.57 X<br />

30-6 cmz/sec"C and a = 1.04 kPa-1.<br />

Such a relati<strong>on</strong>ship can be used for predicting<br />

the frost heave under field c<strong>on</strong>diti<strong>on</strong>s from<br />

laboratory tests at zero or low overburden<br />

pressures. The expected frost heave of homogeneous<br />

soil in the field.may be estimated over a<br />

wide range of overburden pressures and salinities<br />

from the results of relatively few laboratory<br />

tests using the method presented by K<strong>on</strong>rad<br />

and Morgenstern (19831, provided that the<br />

following apply:<br />

1) The salinity and density of the soil sample<br />

used in laboratory testing are essentially<br />

the same as that existing in the field.<br />

2) The freezing characteristics reflect the<br />

c<strong>on</strong>diti<strong>on</strong>s at the <strong>on</strong>set of the formati<strong>on</strong> of<br />

the final ice lens (i.e,, a "quasi" stati<strong>on</strong>ary<br />

frost fr<strong>on</strong>t).<br />

3) The sucti<strong>on</strong> at the frost fr<strong>on</strong>t is relatively<br />

small (i.e., warm plate temperatures close<br />

enough to O°C to ensure a small length of<br />

unfrozen soil).<br />

1125

SUMMARY OF RESULTS AND CONCLUSIONS<br />

REFERENCES<br />

The effects of the various parameters <strong>on</strong> frost Chamberlain, E.J. (1983). Frost heave a€ saline<br />

heave test results can be summar

EFFECT OF VARIABLE THERMAL PROPERTIES ON FREEZING<br />

WITH AN UNFROZEN WATER CONTENT<br />

VJ. Lunardini<br />

U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering Laboratory, Hauover, NH, USA<br />

SYNOPSIS While many materials undergo phase change at a fixed temperature, the variati<strong>on</strong> of unfrozen water with<br />

temperature causes a soil system to freeze or thaw over a finite temperature range. Exact and approximate soluti<strong>on</strong>s<br />

are given for c<strong>on</strong>ducti<strong>on</strong> phase change of plane layers of soil with unfrozen water c<strong>on</strong>tents that vary linearly and<br />

quadratically with temperature. The temperatures and phase change depths are found to vary significantly from those<br />

predicted for the c<strong>on</strong>stant temperature (Ne-umann) problem. The thermal c<strong>on</strong>ductivity and specific heat of the soil<br />

within the mushy z<strong>on</strong>e varied a8 a functi<strong>on</strong> of unfrozen water c<strong>on</strong>tent. The effect of specific hear is negligible and<br />

the effect of variable thermal c<strong>on</strong>ductivity can be accounted for by a proper choice of thermal properties used in<br />

the c<strong>on</strong>stant thermal property soluti<strong>on</strong>.<br />

INTRODUCTION<br />

for soils can be expressed by different functi<strong>on</strong>al rala-<br />

The theory of c<strong>on</strong>ductive heat transfer with solidifica-<br />

ti<strong>on</strong>s. The simplest relati<strong>on</strong> is a linear <strong>on</strong>e<br />

ti<strong>on</strong> has been largely c<strong>on</strong>fined to materials that change<br />

phase at a single temperature. The beat known problem is<br />

that of Neumann and its soluti<strong>on</strong> has been ddely used for<br />

the.freezing of soils, Neumann (1860), Berggren (1943),<br />

Carslaw and Jaeger (1959). However, for media such as<br />

soils, the phase change can occur over a range of temperatures,<br />

Anders<strong>on</strong> and Tice (1973), Tice et al. (1978),<br />

Lunardini (1981s). At any temperature below the normal<br />

I<br />

freezing point, there will be an equilibrium state of<br />

I<br />

I<br />

+Thowsd<br />

unfrozen wafer, ice, and soil solids. Figure 1 shown the<br />

geometry for a semi-infinite soil mass, initially at a<br />

temperature above freezing, that freezes due to a c<strong>on</strong>stant<br />

surface temperature held below freezing. The phase<br />

change is assumed to occur within temperature limits of<br />

T, and Tf, representing mlnimum and maximum phase<br />

change temperatures.<br />

I I<br />

Figure 2 show a sketch of the unfrozen water, E, as<br />

Tm<br />

Tf<br />

a functi<strong>on</strong> of temperature for a typical soil. At Tf<br />

the water is all liquid, while at T,. the free water is<br />

Figure 2. Unfrozen water verau8 temperature.<br />

all frozen. There may be a residual amount of unfrozen<br />

bound water, denoted by Ef, which will remain even at<br />

very low temperatures. It is assumed that for T < Tm, 4 relati<strong>on</strong> which can closely model the data and is easy<br />

unfrozen water may exist but no phase change will occur.<br />

TO manipulate analytically is a quadratic functi<strong>on</strong><br />

The regi<strong>on</strong> T, 5 T 5 Tf iR called the z<strong>on</strong>e of phase<br />

change or the mshy z<strong>on</strong>e. In this regi<strong>on</strong> water can<br />

r,=c0+ 24 (T - Tf) + %(T - Tf)2<br />

solidify to ice with unfrozen water and ice coexisting.<br />

4Tm<br />

As (4- T,) + 0, the phase will change approach the ATm<br />

(2)<br />

Neumann problem often used for coarse-grained materials The thermal c<strong>on</strong>ductivity and the specific heat, within<br />

errch as sands and gravels. The form of the functi<strong>on</strong><br />

the rmshy z<strong>on</strong>e, are functi<strong>on</strong>s of the unfrozen water and<br />

may be represented by<br />

I 2<br />

3<br />

h+W* b+Wh ThWd<br />

(kf -ku )<br />

k -ku -- A5 (5-2,) (3)<br />

(Cf Xu)<br />

c = cu - (€3,) (4)<br />

These properties are functi<strong>on</strong>s of the particular unfrozen<br />

water functi<strong>on</strong>, Frivick (1980). Equati<strong>on</strong> 3 gives k-<br />

values close to those of the geometric ran for the<br />

I - parameters of this study. Within the fully<br />

X<br />

(z<strong>on</strong>e 1) it is assumed that the thermal propertiee are<br />

l"-x 6 c<strong>on</strong>stant and equal to the frozen valuea while €or the<br />

thawed regi<strong>on</strong> (z<strong>on</strong>e 3) the properties are c<strong>on</strong>stant and<br />

Figure 1. Geometry for solidificati<strong>on</strong> with a phase equal to<br />

the thawed soil valuea.<br />

change z<strong>on</strong>e. Tien and Geiger (1967) and Ozjsk and Uzzell (1979)<br />

1127

used an unfrozen liquid c<strong>on</strong>tent which varied with positi<strong>on</strong><br />

within the two-phase z<strong>on</strong>e but did not deal with soil<br />

systems. Cho and Sunderland (1974) found a soluti<strong>on</strong> for<br />

the freeze of a material with thermal c<strong>on</strong>ductivity varying<br />

linearly with temperature and with a single phase<br />

change temperature.<br />

BASIC EQUATIONS<br />

For a small volurne within the mushy z<strong>on</strong>e, energy will be<br />

c<strong>on</strong>ducted in and out of the volume and latent heat will<br />

be released during solidificati<strong>on</strong>: the problem is <strong>on</strong>e of<br />

c<strong>on</strong>ducti<strong>on</strong> with a distributed energy source. The<br />

governing equati<strong>on</strong>s were derived by Lunardini (1985,<br />

1987). The energy equati<strong>on</strong> is<br />

Thermal C<strong>on</strong>ductiviLy and specific heat in regi<strong>on</strong> 2, for<br />

the linear E case, are<br />

k = ko(l + 61 02) ( 6a)<br />

c = CoCl + 62 e,)<br />

(6b)<br />

For the rmshy z<strong>on</strong>e with variable thermal properties<br />

ko - ku and Co - Cu. however, ko, Co can be any values if<br />

the thermal properties in regi<strong>on</strong> 2 are c<strong>on</strong>stant.<br />

In the mushy z<strong>on</strong>e the following transformati<strong>on</strong><br />

For linear 6 the functi<strong>on</strong><br />

is used.<br />

$ can be evaluated explicitly.<br />

k - ko 41 + 2E,$ (9)<br />

e3(x,t) = o (14)<br />

Exact soluti<strong>on</strong>s for the three-z<strong>on</strong>e problem with variable<br />

thermal properties have not been found. Approximate<br />

soluti<strong>on</strong>s can be obtained using the heat balance integral,<br />

however, before doing this it is useful to examine<br />

the simpler two-z<strong>on</strong>e problem. If the surface temperature,<br />

Ts, is greater than or equai to the minimum phase<br />

change temperature then a completely frozen z<strong>on</strong>e dl1 not<br />

exist. Thus we need <strong>on</strong>ly examine regi<strong>on</strong>s 2 and 3.<br />

lW0 ZONE PROBLEMS<br />

The two-z<strong>on</strong>e problem is simpler than the three-z<strong>on</strong>e case<br />

and will lead to results that can simplify the need for<br />

the full three-z<strong>on</strong>e problem. The linear unfrozen water<br />

case will be examined for both variable and c<strong>on</strong>stant<br />

thermal properties while the quadratic water c<strong>on</strong>tent case<br />

will be evaluated <strong>on</strong>ly for the c<strong>on</strong>stant property problem.<br />

This will be shown to be adequate for the general<br />

problem.<br />

Linear Unfrozen<br />

Water Functi<strong>on</strong><br />

Variable Thermal Properties<br />

Equati<strong>on</strong>s (12-14)<br />

*<br />

are valid for this case except that the<br />

boundary c<strong>on</strong>diti<strong>on</strong> (12b) becomes<br />

E 92<br />

9(0.t) = 0 ,+ - p (15)<br />

An approximati<strong>on</strong> to the soluti<strong>on</strong> my be obtained with the<br />

heat balance integral method which has been adapted to<br />

prob.lems of freezing in soils systems by Lunardini<br />

(i981b, 1982, 1983) and Lunardini and Varorta (1981).<br />

The equati<strong>on</strong>s are well known and will not be derived<br />

here, the interested reader can c<strong>on</strong>sult Lunardini<br />

(1981a). Referring to Figure 1, Equati<strong>on</strong>s (12) and (13)<br />

become<br />

The most general case is a problem with 3 regi<strong>on</strong>s as<br />

ahown in Figure 1, The equati<strong>on</strong>s for the three regi<strong>on</strong>s<br />

are<br />

For the heat balance integral<br />

Eqs (13a,b) becom-3<br />

Quadratic temperature profiles are assumed for $ and<br />

since experience has shown that they yield good results<br />

for the heat balance integral wthod.<br />

In order to simplify the<br />

are defined<br />

x - 2yq<br />

’ algebra the following parameters<br />

lim e3 (x.t) = -<br />

x4-<br />

$0<br />

6-X - BX<br />

The soluti<strong>on</strong> of Eqe (16) and (17) is stralghtforward but<br />

tedlous; the algebraic manipulati<strong>on</strong>s are given in<br />

1128

Lunardini (1987). The parameters y and B can be found<br />

from the following equati<strong>on</strong>s.<br />

I<br />

Q2 - [N t Y M + T I<br />

-<br />

r12BlK + B1(2K t A)<br />

Q3 - Jw + %1A<br />

C<strong>on</strong>stant Thermal Properties<br />

t<br />

- 'y<br />

8J2BlK<br />

The c<strong>on</strong>stant thermal properties soluti<strong>on</strong> follows from the<br />

preceding case if flPl + 0, B1 + 0, a. = a2, uo - u, &,-A.<br />

The parameter. y is again found from Eq (22). For this<br />

case an exact soluti<strong>on</strong> is possible by using a similarity<br />

transformati<strong>on</strong>, as was shown by Lunardini (1985).<br />

Quadratic Unfrozen<br />

Water Functi<strong>on</strong><br />

With a quadratic unfrozen water functi<strong>on</strong>, it is not<br />

possible to find a closed form soluti<strong>on</strong> for variable<br />

thermal properties. Thus a heat balance approximati<strong>on</strong><br />

will be used for c<strong>on</strong>stant thermal properties.. The equati<strong>on</strong>s<br />

for regi<strong>on</strong> 2, using IQ (21, are<br />

a-<br />

a2 aL2 -<br />

a<br />

at [(1+2u)e2 - 0 e22]<br />

(25)<br />

some specific cases. C<strong>on</strong>sider a typical 8011 with<br />

Properties suggested by Nakano and Brown (1971). The resultr<br />

of several cases are summrrired in Tables I and<br />

11. Cases 1-3 in the tables show that the effect of<br />

specific heat variati<strong>on</strong> is not important and can be<br />

neglected. However. case 4 indicates that the thermal<br />

c<strong>on</strong>ductivity can cause 15-25% variati<strong>on</strong>s in the rate of<br />

growth of the freezing z<strong>on</strong>e. Case 5 uses average values<br />

of k and C within the mushy z<strong>on</strong>e and the effect of variable<br />

properties can be accounted for by using the<br />

c<strong>on</strong>stant property soluti<strong>on</strong> with the average of the fully<br />

frozen and fully thawed thermal properties. Cases 4 and<br />

6 show that the heat balance approximati<strong>on</strong> is within<br />

about 7% of the exact soluti<strong>on</strong>. This verifies the<br />

acceptable accuracy of the heat balance integral method.<br />

The effect of the different unfrozen water c<strong>on</strong>tent<br />

functi<strong>on</strong>s can be deduced from cases 4 and 7 of Table 11.<br />

The growth rate for the quadratic water functi<strong>on</strong> lags<br />

that of the linear water functi<strong>on</strong> by about 9%. This was<br />

also noted by Lunardini (1985). The quadratic unfrozen<br />

water functi<strong>on</strong> will be more accurate for an actual soil<br />

and is presented in graphical form as Figures 3-5 for the<br />

2-z<strong>on</strong>e problem.<br />

Table 1. Effect of thermal properties <strong>on</strong> freeze of Boil<br />

with average properties, linear 6.<br />

Case Co ko 61 y X Diff. Comment<br />

1 0.63 0.0058 0.431 0,3988 - variable k.C*<br />

2 0.63 0.0058 '0.431 0.3996 0.2 CzO.63, c<strong>on</strong>stant<br />

3 0.54 0.0058 0.431 -0.4016 0.7 Cx0.54, c<strong>on</strong>stant<br />

4 0.54 0.0083 0 0.4575 14.7 c<strong>on</strong>stant k,C*<br />

5 0.585 0.0071 0 0.4126 3.5 c<strong>on</strong>stant k,C**<br />

6 0.54 0.0083 0 0,4277 7.2 exact soluti<strong>on</strong>*<br />

To -T, - -Tm - 4'.c, 60 * 0.2, Ef x ,0782, Pd 1.68 g/Cm3<br />

kf - .0083 cal/s-cm'C, = a0058. Cf - -54 cal/cm3-"C<br />

cu = .63, =. 0.1539, ,$ - ,$o - 1.0 Case 1: 62 = -0.1429<br />

* k2 0.0083 C2 = 0.54 kg k, c3 = c,<br />

** k2 - (kf + ku)/2 0.0071 Cp * (Cf + Cu)/2 0.585<br />

Table 11. Effect of thermal properties <strong>on</strong> freeze Of Soil<br />

with extreme property variati<strong>on</strong>s, linear 5.<br />

The heat balance integral<br />

form of Eq (25) is<br />

Case Co k0 g1 y 4, Diff. Comment<br />

1 0.63 0.0058 1 0.4626 - variable k.C<br />

2 0.63 0.0058 1 0.4607 -0.4 -30.63. c<strong>on</strong>stant<br />

3 0.315 0.0058 1 0.4696 1.5 C4.315 c<strong>on</strong>stant<br />

4 0.315 0.0116 0 0.5671 22.6 c<strong>on</strong>stant k,C*<br />

5 0.473 0.0087 0 0.4726 2.2 c<strong>on</strong>stant k,C**<br />

6 0.315 0.0116 0 0.5304 14.7 c<strong>on</strong>stant k,C*<br />

exact soluti<strong>on</strong><br />

7 0.315 0.0116 0 0.5226 13.0 c<strong>on</strong>stant k.C*<br />

quadratic 6.<br />

Eq (17) is still valid €or regi<strong>on</strong> 3. The temperature<br />

profile for regi<strong>on</strong> 3 is again Eq (19) while that for<br />

regi<strong>on</strong> 2 is assumed to be<br />

kf=.0116 cal/s-cm-'C, 4-.0058, Cf-.315 cal/~m~-~C, &-.63<br />

ST 0.1539 4 = +o 5 1 Case 1: 82 = -0.50<br />

* ,= 0.0116 C2 0.35<br />

** k2 ir (kf + ku)/2 = 0.0087 C2 - (C, + Cf)/2 0.473<br />

The parameter y is found from Eq (22) and the equati<strong>on</strong><br />

for B is<br />

h<br />

340 2 .x*<br />

THREE ZONE PROBLEMS<br />

(4B-2h)(B+3) a32 {& @)I1 + 2cI - y1 - 3 71 (28) Since the variable property case can be adequately<br />

handled by an appropriate c<strong>on</strong>stant property soluti<strong>on</strong>,<br />

The two z<strong>on</strong>e soluti<strong>on</strong>s can be compared by c<strong>on</strong>sidering <strong>on</strong>ly the c<strong>on</strong>stant property problem<br />

will be examined.<br />

1129

Linear Unfrozen Water Functi<strong>on</strong><br />

cp= 1.0<br />

0.3" -<br />

The similarity method was used by Lunardini (1985) to<br />

obtain an exact soluti<strong>on</strong> to this problem. The soluti<strong>on</strong><br />

is found with two phase change parameters tl and y,<br />

defined by<br />

The parameters 11 and y are found from the simultaneous<br />

soluti<strong>on</strong> of two equati<strong>on</strong>s. Lunardini (1985) showed that<br />

this soluti<strong>on</strong> approached the Neumann soluti<strong>on</strong> as the<br />

phase change z<strong>on</strong>e decreased. The thaw/freeze interface<br />

can greatly exceed the value for the Neumann soluti<strong>on</strong> if<br />

phase change occurs over a finite temperature z<strong>on</strong>e.<br />

Figure 3. y vs u, quadratic E. two z<strong>on</strong>e problem, + = 1,<br />

= 0.1, 0.3.<br />

0<br />

Heat Balance Integral Soluti<strong>on</strong><br />

The heat balance integral equati<strong>on</strong>s for the three<br />

problem are as follows<br />

z<strong>on</strong>e<br />

0.05k -I<br />

I -<br />

1<br />

5<br />

IO<br />

0 '1111 I I I I Illll<br />

I I I I Ill1<br />

I IO IO0<br />

0<br />

Quadratic temperature profilea were aesurned for the three<br />

regi<strong>on</strong>s with a straightforward soluti<strong>on</strong> to Eqe (31-33).<br />

The results are given below.<br />

(34)<br />

Figure 5. y vs u, quadratic E , two z<strong>on</strong>e problem, 9<br />

0.1, = 0.1, 0.3.<br />

1130

Todoc, TH"6, TfSIOoC, k1-0,00828 cal/s-cm 'c, k2=0.00703<br />

b40.00578. c142-C34.165 cal/cm3 'C, ST4.O605<br />

Quadratic Unfrozen Water Functi<strong>on</strong><br />

The equati<strong>on</strong>s for the quadratic unfrozen<br />

are identical" to Eqs (31-33) except that,<br />

a& (X,t)<br />

-<br />

3 (XI&)<br />

a2 ax ax I -<br />

water relati<strong>on</strong><br />

Eq 32 is<br />

d X<br />

[z I {(1+2u)e2 - U O ~ ~ } + ~ (l+u)X11 X<br />

(38)<br />

X1<br />

Quadratic temperature approximati<strong>on</strong>s were used. The<br />

soluti<strong>on</strong> la given by Eqs (34-36) with the mushy z<strong>on</strong>e<br />

equati<strong>on</strong> given by<br />

2-2 5 e<br />

1-22 - R2 O32y2{T + - 15 (2Z2 - 7~+18)} - O (39)<br />

Case 1 of Table 3 was evaluated for the quadratic E and<br />

it was found that 0 - 0.0572 and y = 0.2730. These<br />

values differ from the linear E approximati<strong>on</strong> by about<br />

8%. Graphical soluti<strong>on</strong>s for the quadratic E, three z<strong>on</strong>e<br />

problem are shown in Figs 6-8 for typical soil parameters.<br />

-------"<br />

Figure 7. Quadratic E, three z<strong>on</strong>e soluti<strong>on</strong>. 9-10, x =0.5.<br />

II<br />

0-<br />

CONCLUSIONS<br />

The mathematical model used assumed the latent heat to be<br />

a eource of energy distributed throughout the volume of a<br />

soil with phase-change temperature limits of Tf and<br />

Tm. This c<strong>on</strong>trasts with the Neumann problem<br />

wherein the latent heat is totally released at the upper<br />

phase change temperature Tf. A comparis<strong>on</strong> of the exact<br />

soluti<strong>on</strong> for the former case showed that it c<strong>on</strong>verged to<br />

the Neumann soluti<strong>on</strong> as (Tf-T,) approached zero.<br />

Thus the mdel is based <strong>on</strong> sound physical principles.<br />

The effect of variable specific heat <strong>on</strong> the rate of<br />

phase change is negligible for the cases examined, thus<br />

it is acceptable to uae an average specific heat value in<br />

the mushy z<strong>on</strong>e. Variati<strong>on</strong> of the thermal c<strong>on</strong>ductivity<br />

with water c<strong>on</strong>tent is significant and can cause 15-252<br />

change in the rate of freezing of the soil. The c<strong>on</strong>stant<br />

"""<br />

IO<br />

IO0<br />

0<br />

Figure 8. Quadratic 5, three z<strong>on</strong>e soluti<strong>on</strong>, +=30, xQ=O.5.<br />

1131

-<br />

property soluti<strong>on</strong>, with average values of the thermal<br />

properties in the mushy z<strong>on</strong>e, gives a soluti<strong>on</strong> which is<br />

quite close to that for the variable property soluti<strong>on</strong>.<br />

It is acceptable to use the much s+mpler, c<strong>on</strong>stant<br />

property soluti<strong>on</strong> rlth average thermal properties to<br />

compensate for the actual variable thermal C<strong>on</strong>ductivity.<br />

A series of graphs are presented of the c<strong>on</strong>srant<br />

property, three-z<strong>on</strong>e problem for typical ranges of soil:<br />

parameters. These graphs allow rapid predicti<strong>on</strong>s to be<br />

made for the freezing of soile with an unfrozen water<br />

c<strong>on</strong>tent that is a functi<strong>on</strong> of temperature and variable<br />

thermal properties. ' . ,<br />

REFERENCES<br />

Anders<strong>on</strong>, D.M. and A. Tice (1973) "The Unfrozen Interfacial<br />

Phase in Frozen Soil Water Systems." In Analysis<br />

and synthesis. EcoloRical Studies, vol. 4, eds., A.<br />

Nodoi et el., New Yort: Springer-Verlag, pp. 107-124,<br />

Berggren, W.P. (1943) "Predicti<strong>on</strong> of Temperature Distributi<strong>on</strong><br />

in Frozen Soils." Transacti<strong>on</strong>s, American<br />

Geophysical Uni<strong>on</strong> 24(3):71-77.<br />

Carslaw. H.S. and Jaeger, J.C. (1959) C<strong>on</strong>ducti<strong>on</strong> of Heat<br />

in Solids, Clarend<strong>on</strong>, Oxford.<br />

Cho, S.H, and Sunderland, J.E. (1974) "Phase Change Problems<br />

with Temperature-Dependent Thermal C<strong>on</strong>ductivity,"<br />

3. Heat Transfer. V. 96, (2), pp. 214-217.<br />

Frivik, P.E. (1980) "State-of-the-Art-Report, Ground<br />

Freezing: Thermal Properties, Modelling of Processes and<br />

Thermal Design," ISGF, pp. 354-373.<br />

Lunardini, V.J. (1987) "Freezing of Soil with an Unfrozen<br />

WatCr C<strong>on</strong>tent and Variable Thermal Properties," CRREL<br />

Rept 417, Hanover,'NH.<br />

Ozisik, M.N. and J.C. Uzzell (1979) "Exact Soluti<strong>on</strong> €or<br />

Freezing in Cylindrical Symmetry with Extended Freezing<br />

Temperature Range", J. Heat Transfer, vol. 101, pp.<br />

331-334.<br />

, Tice, A.R., C.M. 'Burrows and D.M., Anders<strong>on</strong> (1978) "Phase<br />

,,Compositi<strong>on</strong> Measurements &I Soils at Very High Water<br />

C<strong>on</strong>tent by ,the Pulsed Nuclear Magnetlc Ree<strong>on</strong>ance Technique."<br />

Moisture and frost-related soil properties.<br />

Transportati<strong>on</strong> <strong>Research</strong> Board, Nqt. Acad. Sciedces, pp.<br />

11-14.<br />

Tien, R.H. and Geiger, G.I. (1967) "A Heat Transfer<br />

Analysis of the Solidificati<strong>on</strong> of a Binary Eutectic<br />

System", Y. Heat Transfer, Ser C, ASME, vol. 89, pp.<br />

230-234.<br />

NOMENCLATURE<br />

A - 2A0/B<br />

B = (6-X)/X<br />

C = specific heat, ~al/cm~-~C<br />

value of specific heat for c<strong>on</strong>stant<br />

property nushy z<strong>on</strong>e, orherwise C+G<br />

F1 - (1- - 82 )/ao<br />

Fp B21/3aofl1\<br />

k thermal c<strong>on</strong>ductivity, cal/s-cm-'C<br />

* kiJkj<br />

:y- any specified c<strong>on</strong>stant c<strong>on</strong>ductivity mshy z<strong>on</strong>e<br />

value of k, otherwise k, 5 ku.<br />

K - F A<br />

L * latent heat of fusi<strong>on</strong> of water, cal/g<br />

M a 1 - A261/(2K)<br />

Lunardini, V.J. (1985) "Freezing of Soil with Phase<br />

Change Occurring Over A Finite Temperature Z<strong>on</strong>e," Pro- t<br />

time<br />

ceedings, 4th Int. Offshore Mechahics and Arctic Engi- T<br />

temperature<br />

neering Symposium, Vol. II, pp. 38-46, Alnerican Society, Tf, T,,, - maximum and minimum phase change temperatures<br />

of Mechanical Engineers.<br />

To, Ts = initial and Burface temperatures<br />

X = Cartesian coordinate<br />

Lunardini, V.J. (1983) ';Freezing and Thawing: Heat<br />

Balance Integral Approximati<strong>on</strong>s," J. Energy Resources 2; volumetric ,water fracti<strong>on</strong> "<br />

X; = ,phase change interface for Tf, Tm<br />

Tech., vol. 105(1), pp. 30-37.<br />

e - RA/B<br />

Lunardini, V.J. (1982)' "Freezing of Soil with Surface a I thermal diffusivity k/C<br />

C<strong>on</strong>vecti<strong>on</strong>," Proceedings of Third <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Symposium ail -, ai/aj<br />

<strong>on</strong> Ground Freezing, USbCRREL, Hanover, I", pp. 205-212, a0<br />

kO/CO,<br />

61 = kp.. -1<br />

Lunardini, V,J, (19Bla) Heat Transfer in Cold Climates,<br />

Van Nostrend Reinhpld Company, New York. 6 "<br />

62 - CfU -1<br />

temperature penetrati<strong>on</strong> depth<br />

e (T- T)/(Tf-Tm). dimensi<strong>on</strong>less temperature<br />

Lunardini,* V.Y. (1981b) "Phase Change Around a Circular A = $0 E'- 32<br />

Cylinder," J. Heat Transfer. vol. 103, no. 3, pp.<br />

A0 90 '30<br />

598-600.<br />

E - ratio ,of unfrozen water ma88 to soil, solid<br />

mass<br />

Lunardini, V.J. and R. Varotta. (1981) "Approximate Solu- , to, &f, - values of 5 at Tf, Tm, T,<br />

ti<strong>on</strong> to Neumann Problem for Soil Systems," J. Energy<br />

pd -, dry unit density of soil, solid&, g/cm3<br />

Resources Tech., vol. 103, no. 1,' pp. 76-81.<br />

a<br />

C329fS~<br />

00 cso$/sT<br />

Xakano; Y. and J. Rrotm (1971) "Effect of a Freezing Z<strong>on</strong>e $, (Tf-T,)/(Tf-T,).<br />

of Finite Width <strong>on</strong> the Thermal Regime of Soils,'' J. Water 40 - ITo-Tf)/(Tf-Tm)<br />

Resources <strong>Research</strong>, vol. 7, no. 5, pp. 1224-1233.<br />

Subscripfs<br />

Neumann, F. (ca. 1860) 9ctures given in 1860s. See<br />

Riemann-Weber, Die partiellen Differential-gleichungen 1,2,3 regi<strong>on</strong>s of soil<br />

'Physlk (5th ed., 1912.). 2: 121.<br />

f.8.u - frozen, surface value, and thawed value<br />

1132

- . DEVELOPMENT AND APPLICATION PRACTICE OF METHODS<br />

FOR PRELIMINARY THAWING OF PERMAFROST<br />

SOILS IN FOUNDATIONS<br />

E.S. Maksimenko<br />

Northern Affiliate, <strong>Research</strong> Institute for Foundati<strong>on</strong>s and Underground Structures,<br />

USSR's State Building Committee, Vorkuta, USSR<br />

SYNOPBIS ' 'Varieties Of methoda are examined( methods for calculati basic electric thawing<br />

parametera, via. charati<strong>on</strong> and power expen@&, pre Qiacuaaed according~o frozen-soil o<strong>on</strong>dlti<strong>on</strong>a<br />

and the. chosen thewing regime;, technical apecliicafi<strong>on</strong>s and f ieLds of applicati<strong>on</strong>, Some new<br />

thawing methods ard deaozibed.<br />

A highly important measue for reduaing deiowati<strong>on</strong>s<br />

in the foun&t$ow of buildlximand.<br />

strua4wba exeated 05 prmafroet aoilb xovea<br />

to b9 a pralimimq thawtng of $hew so Q la to<br />

I design depth: Preli@inary thawing enjoya<br />

a partioularlg largs-male epglicatioa-in COP<br />

strmctiozl gro acta. o e&eaS 'wtth an irri.&ul&r<br />

and deep ocou$Bnoe of the top swam oi 'Renurfxost<br />

9oib* 1 ,<br />

TM. etsi 'of. trie a~kri aa8"8e~tbrr..for,prsliminary<br />

thawing em to, be &alculkrbe& rccordiiag<br />

to the apeciIia froaen-soil c<strong>on</strong>aPtiioaa, the<br />

sise of the struoCul.e bo be rrerlted, the iw<br />

tenaity of its, i ot <strong>on</strong>'i6~4ql;ioo iapila, as<br />

well 881 the, im&ntrd. mebhod oi 'ioundafl<strong>on</strong><br />

c3<strong>on</strong>gtruet~oa. Preliminary ebranning depth for<br />

buil8s a QQ to 24 $p wide ar,e as a ruJe, 10-<br />

-20 m,yor large irldustrial OB jeofa they may<br />

attaS,n 40 m (Maksimenko, Pmornersv et air,<br />

9986).<br />

Am<strong>on</strong>g the 'f alrly' great 'number of different<br />

methods of, preliminary thawing the <strong>on</strong>es that<br />

have become partioul~wly wideagreed are hydro-,<br />

steam- and eleotric, thawing.<br />

The firit two secuxe a high thawing 'rat6 ' in<br />

Well-filteriog largebskeletal soils, but are<br />

little ef feotive' in thawing iinelgl.disgezsed<br />

sediments.<br />

Applicability of elaatric thewing mefhoda is<br />

Rraatioally not restrioted by. the type' of I549<br />

soils to be thawed; thereibre, in the .Vorkuta<br />

industxiel dlstriot, where clayey aoila axe<br />

Sridespreed the entire volume of work for pre-<br />

'liminasy t h n g her been executea with the<br />

uBe of eleotricity. Xn recent years these methods<br />

have been suoceasfullg used also in 0th-<br />

BE Pegi<strong>on</strong>s - Waetern en4 Eastern Siberia (Umngoiakaya<br />

end Ndr ungrinskaya thermal power stati<strong>on</strong>s).<br />

Not lead important In this were such<br />

iaotprs as the use of electricity required for<br />

oarr ing out numerous general c<strong>on</strong>etrmcti<strong>on</strong> jobs,<br />

a a&iciently sim le technology and the poaslbilitg<br />

of o<strong>on</strong>trolling the Ghawing process.<br />

The grinoipal varieties of electrto thawing<br />

methods are: the use of various eleatric he<br />

aters and a direct passage of eJternatiug electric<br />

current through the soil mass being<br />

thawed with the aid of electrodes,<br />

Heaters and eleo$rodes are to be set up at<br />

the area to be thawed. in the majority of caaes<br />

at the apioes of e uilaterel triangles in<br />

the preliminarily dxilhd holes. The spading<br />

of holes will be appointed according to caloulatioa<br />

results with respect; to the duxat5-<br />

<strong>on</strong> of soil thawing and electricit enses,<br />

i.s. the main parametera determin&$he efiieienoy<br />

of the method.<br />

Since in the meJority of cases preliminary<br />

thawing is achieved <strong>on</strong> areas with permafrost<br />

soils of n<strong>on</strong>dueing type, to reduoe electri-<br />

.city a<strong>on</strong>sum ti<strong>on</strong> various measuxes are taken<br />

to oodins teat releases solely to oacurence<br />

depfha of the soila to be thawed. In the use<br />

of eleotric heaters this. ia achieved by lacing<br />

the heatin arts directly inside t e<br />

frozen maw ant in the we of electrodes -<br />

by covering with electrically nowc<strong>on</strong>ductive<br />

varnishee nit paints the upper surfaces of<br />

thawed soils cutting gcxasa the frozen mass.<br />

Of a11 the versatilit of elactric heater dealgns<br />

(Maksimenko, l&) afticulerly wideap<br />

reed in thawing raatice %ave become ohmlc<br />

heaters (Boiko, fS7S) which are noted for low<br />

material c<strong>on</strong>sumpti<strong>on</strong> and simplicity in manufacture.<br />

The power of such heaters is determined<br />

by the applied v6ltege (ulhally not ab<br />

ow 40 V) and the diameter of ib# branches<br />

subject to B .c<strong>on</strong>diti<strong>on</strong> that the density of the<br />

cuxrgnt flowing in it should not exceed 1.5<br />

A/mm (Meksimenko, 1982). An optimal opereting<br />

regime of, ohmic heatera corresp<strong>on</strong>ds to<br />

a length power, 1 .GI.8 .kW/m. A further inream<br />

of power will lead to significant evaorati<strong>on</strong><br />

of soil moist;ure. f.xoa the @oil mass<br />

!ehg thawed, which is accompanied b'y an .inorease<br />

of thermal resistance of the soil aro-<br />

uqd the heafer and a decrease of the th~dw<br />

rate.<br />

Ohmic heatera bel<strong>on</strong>g to c<strong>on</strong>stant-power heaters<br />

for which the durati<strong>on</strong> of thawing (electric<br />

power aupply) is to be calculated according to<br />

fhe formula (1) obtainea by approximating the<br />

analytical aoluti<strong>on</strong> of the problem of heat<br />

c<strong>on</strong>aucti<strong>on</strong> for a linear source of heat in a<br />

boundless massif ( hrdaw, &6p,#&).<br />

1133

where is durati<strong>on</strong>, a; R is the radius of<br />

thawing (hdius of the z<strong>on</strong>e of thawed ground<br />

around the heater), m; 6 is latent heat of<br />

ice melting, kJ/k 8 w ia the ice c<strong>on</strong>tent of<br />

frozen soil, kg/m 9 4 a is t e temperature c<strong>on</strong>ductivity<br />

of thawed soil, m .B/si Fl La the<br />

length power of the heater, kW/m.<br />

Bpecific electric powep c<strong>on</strong>sumpti<strong>on</strong> per unit<br />

volume of prepared soil for c<strong>on</strong>atant-power<br />

heaters is to be calculated according to the<br />

i ormula<br />

py, yT is the specific electric resistan-<br />

ance of soil in the frozen and thawed state,<br />

respectively, Obmm; r is the radius of the<br />

hoW inside which an electroae is'glaced,<br />

Y is the electrode radius, m; V is the<br />

v8ltege between the electrodes, usually equal<br />

to 380 V; the rest of the symbols axe the same<br />

as those in the formulae (I) ana (2).<br />

The specific electric power c<strong>on</strong>sumpti<strong>on</strong> per<br />

unit volume of prepared soil under the elgctxode<br />

meshod is to be calculated according to<br />

the i ormula<br />

where q1 is electric power c<strong>on</strong>sumpti<strong>on</strong>, kJ/m 3<br />

;<br />

h is the length of the heating part of the<br />

heater, mi R, ia the depth of preliminary he<br />

tiw, . m-<br />

Applicati<strong>on</strong> of electric heaters for preparing<br />

foundati<strong>on</strong> soils is characterised by the fob<br />

lowing indices; under 2-4 m spacing of heaters<br />

the thewing durati<strong>on</strong> varies within <strong>on</strong>e-two<br />

, m<strong>on</strong>tha, the speoific e ectric pow r<br />

ti<strong>on</strong> amounting to 4G98 kWhr pel' mgo35Kperad<br />

foundati<strong>on</strong> area (Maksimenko, 'I 984) ..<br />

Direct passage of alternating electrlo cui+<br />

rent through the soil mass being thawed (electxode<br />

method) is eeeentially elm ler tecb<br />

nolo icall , since we may use as. efectrodes<br />

metafiic pfpes, xeiddrclement ro- etc, whia6<br />

do not call for special treatment. The durati<strong>on</strong><br />

of tbawing (c), of soils by means of the<br />

electrode method Is described by a aemi-empirice1<br />

formula<br />

where q2 le electric power c<strong>on</strong>sumpti<strong>on</strong>, kY/m<br />

The above varieties of electric thawing methods<br />

differ not merely in the character of heet<br />

c<strong>on</strong>ducti<strong>on</strong> .in the mil mass thewad (heat<br />

from the heater finds its way into the soil<br />

through the borehole walls, whilst under t4e<br />

electrode method it is generatea directly in<br />

the soil) but also b the dynamlos of the tha-<br />

1ng process proper, $.e. by the dependence of<br />

the thawiqg radius <strong>on</strong> the durabi<strong>on</strong> of electric<br />

power up ly.. When usi heatefa (ef.fi ure,<br />

curve 1) he tha~y 2% attunatee witi time,<br />

which is explained y an increase of thermal<br />

resisbance bf thw. thawed soil z<strong>on</strong>e, ,interfering<br />

with heat tranafer from the.beater to the<br />

boundary of phaeta tranaitigns, i,e. the fr<strong>on</strong>t<br />

of thawing. Under the electrode method, with<br />

and increase 02. the thawed z<strong>on</strong>e volume the thawing<br />

rate inareaees (cumre 2),'which ia associated<br />

with a decrease of B ectfic resiatanoe<br />

of the soil between thg e 1 ectrodea and,<br />

oorrespoadingl , with an inoxease of heat releese<br />

inside de soil mas bel% .tbwgd. ,<br />

where<br />

Fig. Thawing redtus R versua durati<strong>on</strong><br />

for different methoda.. of electric thawing<br />

h 3 2<br />

A significant impxovement of technico-ec<strong>on</strong>omic<br />

r>=.1-03a103 [(In -1 +5'm18]P p ' ':06 gw/v2r indices of electric thawing has been made PO+<br />

HO<br />

Bible by the we of a combinati<strong>on</strong> method developed<br />

receetly (Maksimenko, 19E4), which is a<br />

synthesis of the poaitlve propertier of the<br />

r.= .& (~/r,)~<br />

- ti (r/~~>~; above-deacxibed varieties.<br />

1134<br />

Thawing of soils b the combinati<strong>on</strong> method<br />

involves the use OK the same electric heaters

as current receivers with a variable, two-<br />

med by the electrod8 incrsses with the thaw-<br />

-stage power supply regime. A t the fifst stage ing re dius) .<br />

voltage is supplied to the cdrxent receivers<br />

in accordance with the specificati<strong>on</strong>s of the Using the Soluti<strong>on</strong> of the problem of electric<br />

electric heaters used.' In this case the thaw- resistencs between coaxially arranged infinite:-<br />

and finite cylinders (loeael, Kochanov,<br />

q~hieved. separately by the heatera and by the<br />

electrode method the first stage is ovex. Ab<br />

the' sec<strong>on</strong>d stage, voltage, mostly 380 V, is $ roo y.v2<br />

BU plied to the adjacent current P= receivers,<br />

9 (5)<br />

usfng them a8 electrodes foy a direct passage<br />

of electric current through the soil (curve 31<br />

0.87*yr0<br />

s,(1 - 71<br />

Reducti<strong>on</strong> of thawing'length and of electric<br />

power c<strong>on</strong>aumpti<strong>on</strong> under the combinati<strong>on</strong> method<br />

.is achieved: at the first; stage - due to a ,<br />

higher rate of thawing by the us0 of heaters where $/ = 0.637 + 0.554*(h/2 ro)0*761 theotber<br />

for an inaignificenf thermal resistance of of the symbols are the same a8 in the pxevtficant<br />

%he thawed zoile xe,semtes of and, heat corresp<strong>on</strong>dingly, accumulated in Inaigni- thia<br />

o\is i ormula e.<br />

z<strong>on</strong>e! at, the sec<strong>on</strong>d atage - due to :e high rate :&YAYe Of H, be calculated from the<br />

of deCtXQd8' thawing fop a sufficient1 well-<br />

-developed procesa and c<strong>on</strong>centrati<strong>on</strong> of heat<br />

*rd.eaaes inside the soil mass being thawed.<br />

Beginning froi 1984 the combinati<strong>on</strong> methqd of<br />

eleotric thawing has been intensively intro- .<br />

qucucad in the cify of Vorkuta,' wherw during<br />

t.he ,f irst thzlee ears al<strong>on</strong>e it was .uaed in the<br />

R, r,*exp(A (6)<br />

where<br />

c<strong>on</strong>structioe of jY 5 indusffial and civvil grojecta<br />

and is at presant beilog mastered by the<br />

builders of the Uxe oiskaya thermal powex<br />

stati<strong>on</strong> ana the Tikh 9 4M .. 3 In i comaunity centre. As<br />

A=B+C# B 7 - i<br />

comparaa, to - the design solutiomproviding for JT (1 - q p,,<br />

the use of ohmic heaters for eoil thawing, if<br />

waa possible to mom than aouble improve the<br />

main teabnfco-ec<strong>on</strong>omio indicesr volume of borehole<br />

drilling to accomodete heaters, mefal<br />

c<strong>on</strong>sumpti<strong>on</strong> in fabrioating current: receivezs, 1.3lv;<br />

electric power c<strong>on</strong>awnti<strong>on</strong>, Correap<strong>on</strong>dlngly,<br />

C =<br />

the OOSt Of pXepPrlD& 1. OUrU, Of 'fOWdatiOP SOil<br />

was twice reduced. It is to be underlined<br />

that <strong>on</strong> these projects while, using the combinati<strong>on</strong><br />

method the tkawkng depth d$d pot, underbtandablg,<br />

changh '(1422 m)i qimilhxl is<br />

did the volumes of .prepared 80 1. Opry f [ e spacixig<br />

of current receivers increased from 2.2-<br />

' -3.5 m to 4.0-4.5 m. In, the cam of objecti The durati<strong>on</strong> of soil thawing by the use of the<br />

combinati<strong>on</strong> method will be calculated after<br />

~ ~ t ~ r f & ~ ~ f ~ & ~ $ ' z2!ttfG ~ ~ $ :$- ~ ~ the formula (7) and B ecif ic electric power<br />

in <strong>on</strong>e-<strong>on</strong>e 'and a @;elf m<strong>on</strong>ths, the spacing of c<strong>on</strong>sumpti<strong>on</strong> - after tfe formula (8).<br />

current receivers can bs'increased to 5.C-7.0<br />

m.<br />

..<br />

-<br />

rk = Lq + r2 i (7)<br />

The length of the first stage of soil thawing<br />

by the uag of the combinati<strong>on</strong> method Is. to be<br />

c$lcula'twd after the formula (1) by substiuting<br />

R values in .it,'and that of the sec<strong>on</strong>d<br />

stagso- after the fbrmula' (3) by preLimSaerily<br />

aubstitufing .r fox, %. 0.25010'~f he, I<br />

The value of R is dependent both <strong>on</strong> the ape- Ptl +<br />

eific .froeen-eoh and technological pareme- In( Wx0 1<br />

terst spacing of curxqnt xeceivexa, their geo- Pn =<br />

metribal dimensi<strong>on</strong>s, the magnitude a9 applied x I<br />

R2-Ro<br />

voltage the power of electric beaters used<br />

at the 2irst stage. Moreovax, 'in app'o$nting<br />

technological parameters it would be feasible where , is the durati<strong>on</strong> of the first<br />

to secure the possibility of using the aame -.I 2nd SeCOdi st&e calculated accordkng to the<br />

sources of electric power (transforinars) for formulae () and (2) for tbe respective parapopex<br />

supply of current receivers at bath the meter values, st qk ia elecfric power c<strong>on</strong>sun+<br />

sfageii, i.e, to apppint the power of the he- pti<strong>on</strong>, kJ/cu.m.<br />

to<br />

minati<strong>on</strong> of the<br />

thet Of<br />

thawing<br />

the<br />

process (power at the c<strong>on</strong>au- ter- mexience in using t'bwing<br />

1135

inthe Voxkuta industrial district and in otb<br />

er regi<strong>on</strong>s snables u8 to give the following<br />

characteristic of the field of applicability<br />

of these methoda,<br />

The use of electric heaters is not c<strong>on</strong>trolled<br />

by the frozen-soil c<strong>on</strong>diti<strong>on</strong>s of the areas<br />

to be thawed, and the technico-ec<strong>on</strong>omic<br />

indices of Che said method axe grincLpally<br />

determined by the ice c<strong>on</strong>tent of the SOi18,<br />

their thermal-physical properties and the<br />

chosen thawing regime (heater power, thawing<br />

ra diua) .<br />

The applicati<strong>on</strong> efficiency of the electrode<br />

method is, mopeover, dependent <strong>on</strong> the electric<br />

properties of the soils. Frozen soils<br />

are endowed with a .significant specific resistanae<br />

and the process of electrode thawing<br />

proceeds rather slowly, We length of thawing,<br />

particularly in largeskeletal soils, may be<br />

as l<strong>on</strong>g as several m<strong>on</strong>ths. Furtherpore, by<br />

virtue of the natural inhomogeneity of the<br />

soil mas8 with respect to elecfric resistance<br />

there arise at the gnitial stage local heating<br />

z<strong>on</strong>es the growth of which accounts for<br />

a significant n<strong>on</strong>-wiformity bf- heat releases.<br />

Therefore, 9 rati<strong>on</strong>al field of applicati<strong>on</strong><br />

for the plectrode methd prove to be the<br />

secti<strong>on</strong>ally liomogeneou's clayey grounds with<br />

a specific electric resistance in the frozen<br />

state up to 100 Ohm-m.<br />

The above drawbacks of the electrode method<br />

significantly lese affect the efficiency of<br />

the combinati<strong>on</strong> method because fh8 passage<br />

of electzic current through the soil mass OCcurs<br />

with the presence in the latter ,of sufficiently<br />

developed z<strong>on</strong>es of thawed soil around<br />

the current receivers. Its a plicati<strong>on</strong><br />

is not; restricbed by dlspersi<strong>on</strong> of the soils,<br />

but solely by the specific raaiatance in the<br />

frozen state - 300-400 Ohm .m.<br />

The above-described methods for reliminary<br />

thawing, for all their univereelfty and technolo<br />

ical advantages, call fox the presence<br />

in $e c<strong>on</strong>structi<strong>on</strong> area of electric power<br />

which is not always available in required amounts<br />

in the areas of pi<strong>on</strong>eer c<strong>on</strong>structi<strong>on</strong>,<br />

particularly oil and $as fields. To deal with<br />

such c<strong>on</strong>diti<strong>on</strong>s there has been developed the<br />

energetically aut<strong>on</strong>omous method involving a<br />

direct burning of liquid fuel in the boraholes<br />

(Naksimenko and Pavlichenko, 1986). We<br />

may use as fuel petroleum- ana oil-c<strong>on</strong>taining<br />

wastes .of mpchine building, straw oil,<br />

masouf, etc.<br />

The method is realiaed in the following menner.<br />

Placed ih a borehole preliminarily drilled<br />

to the requisite thawing depth is an in-<br />

,ventory pipe of 80-100 ma diaqetex with a '<br />

welded bottom, intp which fuel is poured and<br />

a perforated tubular air c<strong>on</strong>duit of 2550 mm<br />

diameter is lowered. Setting the fuel <strong>on</strong> fixe<br />

is achieved by means of a lowered wick with<br />

air supplied into the borehole from compressox.<br />

As fuel burns up, there occurs an automa'tic<br />

movement of the z<strong>on</strong>e of principal heat releases<br />

(flame) ovex the depth of the layer beillg<br />

dealt with. Heat is c<strong>on</strong>veyed into the<br />

soil mass being thawed around the borehole<br />

through radiati<strong>on</strong> and a c<strong>on</strong>vective heat exchange<br />

between gaseous combusti<strong>on</strong> proaucts and<br />

borehole walls.<br />

This method is notable for 8 sufficiently unsofisticated<br />

producti<strong>on</strong> technology end a potseibilisof<br />

c<strong>on</strong>trolling the, rate of fuel burning<br />

(t ough air iupply) and. df the number:<br />

of , urns-through in a borehole, and.by $ha<br />

leligth of operatirlg stag'es. The combiq,ed, fSeld<br />

and laboratory teats OP the new method<br />

have" pointed to a sufficiently high efficien-<br />

~3.;. in the use of fuel (0,'5+0,8), as detesmined.<br />

by the ratio of beat sgent bn thawing<br />

frozen soil to the calorific value of the1 Zuel<br />

(Maksimenko and Pavlicbenko, 986).<br />

In c<strong>on</strong>alusi'<strong>on</strong> we would like to point out that<br />

a preliminary thawing of permafrost soila<br />

in foundati<strong>on</strong>s rignificantly,extends the posaibilitias<br />

of c<strong>on</strong>stmcti<strong>on</strong> reclamati<strong>on</strong> of n+<br />

rthern areas and of the us8 of numerous met&<br />

ods af foundati<strong>on</strong> design, Mwreoyer, the thawingrocess<br />

proper and the c<strong>on</strong>stxucti<strong>on</strong> pro- '<br />

psrtfea of thawed aoils am well costrollable,<br />

thus enabling practically any prsaeC reliability<br />

of the foundati<strong>on</strong> to be securpd for the '<br />

entire eervice period.<br />

Boiko I.V.-(1975). Prec<strong>on</strong>structi<strong>on</strong> thawing<br />

of ermaf rost aoils in the io~drrti~na<br />

of hldixlge and structures in Vorkuta.<br />

- In: Materials <strong>on</strong> C<strong>on</strong>structi<strong>on</strong> Problems<br />

in Vorkuta, Komi ~aqk Publishers, p. 9-<br />

-15, Syktyvkar. .<br />

Iossel Yu,Ya., Kochanov B.S., Stxunakii M,G,<br />

(7981). Calculati<strong>on</strong> of electric ca acb<br />

tgnce. mergoizdet Publishers, p.218,<br />

Maksinmnko E.S, (1982). Becogmendati<strong>on</strong>s for<br />

the use ,of electrOc heaters in thew"<br />

ing permafrost soiZs. N.M.Gersevanov <strong>Research</strong><br />

Institute foS Bpundati<strong>on</strong>a ard<br />

unaergrouna Btructurea, p.26, MOSCOW.<br />

"aksimenko E.5, (198ft). Combinati<strong>on</strong> m0tbod<br />

, for electric thawing. of permafroat grounds<br />

and foundati<strong>on</strong>s. *%ases, Foundati<strong>on</strong>s<br />

an8 Soil Mechanics", I 6, p.21-23,<br />

Moecow.<br />

Maksimenlrd X.S., P<strong>on</strong>omaref V.D., Sorokin V.A.,<br />

Fedoseev Yu.G. (1986) Determinati<strong>on</strong>. of<br />

deformati<strong>on</strong> characteristics of permafrost<br />

soils by using. Che method of test<br />

thawing. "Bases, Foundati<strong>on</strong> and Soil<br />

Mechsnics", I 6, p.21,,22, Moscow. -<br />

Yakaimenko B.S., Pavlicbenko S.4, (1986).<br />

Estimatiw the efficiency of usm liquid<br />

fuel for preliminary thawing 045 tomdati<strong>on</strong><br />

SQ~~EI. - PTDC, N.M*Gwxevanov <strong>Research</strong><br />

Institute for Foundati<strong>on</strong>s a d Underground<br />

Btructnres, issue 85, p.1521.<br />

1136

SECONDARY CREEP INTERPRETATIONS OF ICE RICH PERMAFROST<br />

Sec<strong>on</strong>dary Creep, <strong>Permafrost</strong> Soils, Creep of Ice<br />

E.C. McRoberts<br />

Hardy BBT Limited, Edm<strong>on</strong>t<strong>on</strong>, Alberta<br />

SYNOPSIS 2ec<strong>on</strong>dary greep interpretati<strong>on</strong>s of samples of ice rich permafrost soils at temperatures<br />

from -0.8 C to -4.0 C are presented. The data are compargd to recently published summaries<br />

of ice creep. It is found khat for temperatures below -2.0 C ice creep data c<strong>on</strong>stitutes a<br />

good upper bound or c<strong>on</strong>servative relati<strong>on</strong>ship for permafrost soil creep rates.<br />

At warmer temperatures<br />

samples of ice rich permafrost exhibit faster sec<strong>on</strong>dary creep rates.<br />

INTRODUCTION<br />

A sec<strong>on</strong>dary creep model can offer a realistic<br />

interpretati<strong>on</strong> of load-deformati<strong>on</strong> resp<strong>on</strong>se of<br />

ice and ice-rich permafrost soi1s, for example,<br />

Roggensack (1977) , McRoberts et a1 (1978) ,<br />

Morgenstern et a1 (1980), and Savigny and<br />

Morgenstern (1986) . In additi<strong>on</strong>, sec<strong>on</strong>dary<br />

creep models provide a reas<strong>on</strong>ably straightforward<br />

method of predicting load-deformati<strong>on</strong> resp<strong>on</strong>se<br />

for a wide variety of design requirements<br />

in permafrost, i.e., Nix<strong>on</strong> and McRoberts<br />

(1976) , Nix<strong>on</strong> (1978,) , and Morgenstern et a1<br />

(1980). This paper reports <strong>on</strong> sec<strong>on</strong>dary creep<br />

interpretati<strong>on</strong>s of undisturbed samples of natural<br />

permafrost obtained at several sites in<br />

the Mackenzie River Valley. Upper bound correlati<strong>on</strong>s<br />

relating sec<strong>on</strong>dary creep rate to applied<br />

stress are provided. While the greater<br />

part of the data c<strong>on</strong>siaered are based <strong>on</strong> unc<strong>on</strong>fined<br />

tests, c<strong>on</strong>fined tests are alqo reviewed.<br />

as appropriate, sec<strong>on</strong>dary creep correlati<strong>on</strong>s<br />

are compared with published data <strong>on</strong> flow laws<br />

for ice.<br />

SECONDARY CREEP<br />

The creep resp<strong>on</strong>se obtained by step loadfng a<br />

frozen sample of ice or ice-rich permafrost<br />

soil can exhibit three distinct states; primary,<br />

Sec<strong>on</strong>dary, and tertiary creep. At high<br />

stress levels the sec<strong>on</strong>dary creep stage is<br />

transitory with deformati<strong>on</strong>s passing quickly<br />

into a tertiary phase, the <strong>on</strong>set of which denotes<br />

failure. At low stresses, and depending<br />

up<strong>on</strong> test durati<strong>on</strong>, a sec<strong>on</strong>dary creep stage may<br />

not be reached. The test data c<strong>on</strong>sidered here<br />

are well described bysec<strong>on</strong>dary creep behaviour.<br />

The form of the flow law for Sec<strong>on</strong>dary creep<br />

takes the form (see McRoberts et al 1978)<br />

= A o;/(l-TIm . . . . . * . * . . . . . . 1<br />

where A, F, and n are c<strong>on</strong>stants determined by<br />

testing, E is the sec<strong>on</strong>dary creep rate, a the<br />

applied deviator stress, and T is the temgerature.<br />

In some cases, Equati<strong>on</strong> 1 takes a bilinear<br />

form, see Equati<strong>on</strong> 3.<br />

1137<br />

There has been c<strong>on</strong>siderable discussi<strong>on</strong> <strong>on</strong> the<br />

magnitude of exp<strong>on</strong>ent, n, in Equati<strong>on</strong> 1. Nix<strong>on</strong><br />

and McRoberts (1976) c<strong>on</strong>sidered creep data for<br />

ice and reported a range of n from near 1.0 up<br />

to 4.0 as a functi<strong>on</strong> of temperature and shear<br />

stress level. More recently Morgenstern et a1<br />

(1980) and Sego and Morgenstern (1983) report<br />

that n c<strong>on</strong>verges <strong>on</strong> 3 for ice. This is in<br />

agreement with Paters<strong>on</strong> and Budd (1982) whoc<strong>on</strong>clude<br />

that n = 3 for glacial ice. As noted by<br />

McRoberts (19821, low n values reported byNix<strong>on</strong><br />

and McRoberts (1976) were influenced by low<br />

shear stress, relatively warm tests <strong>on</strong> wellstrained<br />

glacial ice with preferentially oriented<br />

ice crystal structure. McRoberts (1982)<br />

reported a best fit n = 3.2 for artificially<br />

prepared ice with randomly oriented crystal<br />

structure.<br />

Creep data for icerich permafrost soils support<br />

a value of n =3. Roggensack (1977) reported<br />

creep tests <strong>on</strong> undisturbed samples of ice-rich<br />

Eine-grained glaciolacustrine soil anit reported<br />

a bilinear flow law. However by eliminating<br />

certain data he defined a flow law with ~2.75.<br />

McRoberts et a1 (1978)tested ice-rich glaciolacustrine<br />

silts and reported a bilinear flow<br />

low with n =3.0 at low stress. However athiqher<br />

stresses, where creep resp<strong>on</strong>se was dominated<br />

by samples wpich ultimately reached tertiary<br />

creep, an exp<strong>on</strong>ent value of 6.0 was reported.<br />

The magnitude of the exp<strong>on</strong>ent m in Equati<strong>on</strong> 1<br />

accounts fox temperature effects. McRoberts<br />

et a1 (1978)used an m value of 1.8, based <strong>on</strong><br />

correlati<strong>on</strong>s with ice as reported.by McRoberts<br />

(1982). Nix<strong>on</strong> (1978)provided a re-analyses of<br />

the McRoberts et a1 (1978)data and used a value<br />

of m = 2 for a reference temperature of -2 .s'c.<br />

Creep data for ice reported by Morgenstern eta1<br />

(1980) is presented in the form of log A, versus<br />

log (1-T) following Nix<strong>on</strong> andNeukirchner (1984),<br />

see Figure 1. The slope of log A, versus Log<br />

(1-T) defines the m parameteg, which for ice<br />

appears to be E = 2 for T =-1 C and m =1 for T<br />

colder than -2 C.<br />

SAMPLE DESCRIPTION<br />

The creep test data reported byRoggensack(1977),

McRoberts et a1 (1978), and Savigny and Morgenstern<br />

(1986)as well as additi<strong>on</strong>al data reported<br />

here a’re all for icy permafrost soils obtained<br />

in the Mackenzie River Valley between FortSimps<strong>on</strong><br />

and Norman Wells NWT. The test data discussed<br />

here is referred to as B, E, G and P<br />

Series, from Northern Engineering Services Company<br />

Ltd. (1977), the data from Roggensack(l977)<br />

as R series, and from Savigny and Morgenstern<br />

(1986) as S series. The B series samples were<br />

described in detail by McRoberts et al (1978).<br />

The E series samples were obtained by horiz<strong>on</strong>tally<br />

coring in the headscarp of a large landslide<br />

in close proximity to the site discussed<br />

by Roggensack (1977). The G series were obtained<br />

from the same boreholes reported by Savigny<br />

and Morgenstern (1986) * The P series are<br />

peat samples obtained from an elevated peat bog<br />

in the Fort Simps<strong>on</strong> area. Table1 summarizes<br />

the index properties of the samples tested. A<br />

list of the water (ice) c<strong>on</strong>tent data is given<br />

€or each sample in Table 2 as well as in<br />

McRoberts et a1 (1978) for B samples.<br />

B series samples are given as Figures<br />

McRoberts et al (1978).<br />

1 to 7 in<br />

A limited series of tests were c<strong>on</strong>ducted with<br />

c<strong>on</strong>fining pressures of from 28 to 276 kPa using<br />

jacketed samples and either air, mineral oiltor<br />

a weak methanol soluti<strong>on</strong> as cell fluid, see<br />

McRoberts et a1 (1987). TheR series hada light<br />

mineral oil as cell fluid, no membrane, and a<br />

light coat of ice sprayed <strong>on</strong> the sample as a<br />

jacket. No penetrati<strong>on</strong> of oil into the sample<br />

was reported. S series samples were unjacketed.<br />

Test temperatures ranged from -0.8OC to -4 -00 c<br />

and with the majority at -l.O°C and -3.OOC.<br />

Testing durati<strong>on</strong> varied depending up<strong>on</strong> stress<br />

level. For samples that resulted in cre p ruptest<br />

durati<strong>on</strong> ranged from 1 xlOf to<br />

ture 2 x10 $he min. L<strong>on</strong>g-term tests at low stress<br />

Levels ranged in durati<strong>on</strong>s from 2 x10 to2 x IO5<br />

min. In certain cases, tests were terminated<br />

after significant test durati<strong>on</strong>s but before a.<br />

sec<strong>on</strong>dary creep stage, as evidenced <strong>on</strong> a log E -<br />

log time plot was reached. Such tests are separately<br />

identified.<br />

The B samples c<strong>on</strong>sisted of a finely banded stratified<br />

ice with sub-parallel bands of visible<br />

ice from 5 to 20 nun in thickness separated by<br />

soil layers of equivalent thickness. TheE samples.<br />

obtained by horiz<strong>on</strong>tally coring in icerich<br />

glaciolacustrine soils, have the same general<br />

water c<strong>on</strong>tent range as the B samples, but<br />

have an entirely different ice structure. The<br />

ice in the E samples exists assubstantial veins<br />

up to 80 rran thick oriented at varying angles to<br />

the main axis of the sample. The G coxes obtained<br />

by vertical sampling of fine grained<br />

glaciolacustrine clay have lower water c<strong>on</strong>tents<br />

of typically 22% to 30% with <strong>on</strong>e sample at 748.<br />

Visible ice was usually present in the form of<br />

thin lenses and inclusi<strong>on</strong>s even in the lower<br />

water c<strong>on</strong>tent samples. The P seriessamples had<br />

c<strong>on</strong>siderable visible ice with water (ice) c<strong>on</strong>tents<br />

ranging from 410% to 2000%.<br />

Details of laboratory equipment and testing<br />

procedures are discussed by McRoberts et a1 (1978).<br />

In all cases creep interpretati<strong>on</strong>s were d<strong>on</strong>e<br />

using large size computer derived plots of temperature<br />

versus time, strain versus time and log<br />

strain rate versus log time. The average creep<br />

rate of the sample could then be easily determined<br />

from the slope,of the straight Line segment<br />

of the strain-time curve. The creep rate,<br />

so obtained was then compared against the log E<br />

versus log t to check that a sec<strong>on</strong>dary creep<br />

stage had been reached. An example of the type<br />

of plot used to derive strain rates €or all<br />

tests quoted here is given in Figure 2. In this<br />

particular test, primary creep ended at about<br />

3.0 x lo4 min. For the next 3.0 x104 min. a sec<strong>on</strong>dary.<br />

rate of E = 9.09 x lO-’/year was calculated<br />

at a temperature of -1.2’~, A rise in temperature<br />

to -1,OOC then resulted in a sec<strong>on</strong>d period<br />

of sec<strong>on</strong>dary creep at a rate of 1.12 xlO-l/<br />

year. Typical strain time plots for some 30<br />

1138<br />

SECONDARY CREEP INTERPRETATIONS<br />

Basic data for each sample tested are given<br />

either in Table 20r by McRoberts .et a1 (1978).<br />

The greater part of the creep data is for ternperatures<br />

near -1.0%. all B,E,G and P series<br />

data was first grouped together using m =2 .O to<br />

a reference temperature Of -1OC using Equati<strong>on</strong> 2,<br />

McRoberts et a1 (1978), see Figure 3. A cross<br />

superimposed <strong>on</strong> the se‘ries symbol indicates the<br />

creep test terminated in creep rupture. A vertical<br />

line denotes that the sample was testedin<br />

a c<strong>on</strong>fined c<strong>on</strong>diti<strong>on</strong>. A best fit upper bound<br />

line to all data was obtained by judgment to be:<br />

This relati<strong>on</strong>ship exhibits a marked bilinear<br />

form. The exp<strong>on</strong>ent n =6 is heavily influenced<br />

by samples that ultimately failed. Manysamples<br />

at stress levels above 400 kPa did nwtfail, but<br />

may well have d<strong>on</strong>e so fox sufficiently l<strong>on</strong>gtest<br />

durati<strong>on</strong>s. A best fit average line to these<br />

data using statistical methods has not been obtained,<br />

but would clearly result in significantly<br />

lower creep rates than those predicted by<br />

the upper bound relati<strong>on</strong>ship of -Equati<strong>on</strong> 2.<br />

Figures 4. 5 and 6 c<strong>on</strong>sider three temperature<br />

ranges of B,E,G and P series data at average<br />

reference temperatures of -1.0, -2.5 and -3.50Ct<br />

respectively. As ice data reported in Figure 2<br />

suggest a variati<strong>on</strong> in m as a functi<strong>on</strong> of tempexature<br />

an m =2 was used for the soil data between<br />

-0.5 and -1.5OC and an m =1 for colder<br />

data. All samples which failed were eliminated<br />

in Figures 4,5 and 6. Figure4 suggests the flow<br />

law for ice is slightly n<strong>on</strong>-c<strong>on</strong>servative and an<br />

upper bound c<strong>on</strong>sisting of the first term of<br />

Equati<strong>on</strong> 2 isa good fit to the warm soil data.<br />

For soil data between -2 .O and -3 .O°C the ice<br />

data is a reas<strong>on</strong>able upper bound. Thedata colder<br />

than -3. O°C is solely %series data and the<br />

greater part of the data suggests creep rates<br />

somewhat less than ice. Various attempts were<br />

made toquantify reas<strong>on</strong>s for the scatter apparent<br />

in the data by c<strong>on</strong>sidering index properties,<br />

soil classificati<strong>on</strong>s and so forth. However, no

orderly pattern was found. It is possible that<br />

ice structure and the favourable orientati<strong>on</strong> of<br />

ice lenses with planes of higher shear stress<br />

may play a role.<br />

The soils c<strong>on</strong>sidered here c<strong>on</strong>firm a flow law<br />

with n of 3 at lower stresses. At higher stresses<br />

n can become greater than 3 for frozen<br />

soils and a bilinear Plow lawhas been presented<br />

in this study, Equati<strong>on</strong> 3. While it might be<br />

argued see Saviqny and Morgenstern (1986) that<br />

the sec<strong>on</strong>dary creep interpretati<strong>on</strong> should notbe<br />

applied to stress levels which result in failure<br />

it is important to note that transient creep<br />

rates at higher stress levels will be higher<br />

than that predicted by an n of 3. This factor<br />

may be important in a variety of design c<strong>on</strong>siderati<strong>on</strong>s.<br />

Equati<strong>on</strong> 2 is not viewed as being a realistic<br />

upper bound relgti<strong>on</strong>ship for soil data colder<br />

than about -&.5 c. For soil temperatures colder<br />

than -2.0 C and for shear stress levels less<br />

than about 400 kPa the upper bound of soil behaviour.follows<br />

the flow law for ice. That is:<br />

T

0<br />

MCROBERTS, E.C. LAW, T.C. and MURRAY, T.K.<br />

1978. Creep tests <strong>on</strong> undisturbed ice-rich<br />

silt. 3rd. Int. C<strong>on</strong>f. <strong>on</strong> <strong>Permafrost</strong>.<br />

Edm<strong>on</strong>t<strong>on</strong>, Alberta, Canada, pp.540-555.<br />

MORGENSTERN , N . R. , ROEGENSACK , W S . and<br />

WEAVER, J.S. The behaviour of fricti<strong>on</strong><br />

piles in ice and ice-rich soils. 17(3),<br />

pp.405-415.<br />

NIXON, J.F. 1978. Foundati<strong>on</strong> design approaches<br />

in permafrost areas. Can. Geotech. J..<br />

15 (1) I pp.96-112.<br />

NIXON, J.F. and LEM, G. 1984. Creep and<br />

strength testing of frozen saline finegrained<br />

soil. Can. Geotech. J., 21(3),<br />

pp.518-529<br />

NIXON, J.F. and MCROBERTS, E.C. 1976. A design<br />

approach for pile foundati<strong>on</strong>s in permafrost.<br />

Can. Geotech. J., 13(1) pp.40-57<br />

NIXON, J.F. and NEUKIRCHNER, R.J. 1984. Design<br />

of vertical and laterally loaded piles in<br />

saline permafrost. Third Internati<strong>on</strong><br />

Symposium Cold Regi<strong>on</strong>s Engineering<br />

Edm<strong>on</strong>t<strong>on</strong>, Alberta.<br />

NORTHERN ENGINEERING SERVICES COMPANY LTD.<br />

1978. Interim report <strong>on</strong> creep testing of<br />

permafrost soils. Northern Engineering<br />

Services Company Ltd., Calgary, Alberta<br />

1977.<br />

PATTERSON, W.S.B. and BUXl , W.F. 1982. Flow<br />

parameters for ice sheet modeling. Cold<br />

Regi<strong>on</strong>s Science and Technology, 6<br />

pp.175-177.<br />

RADD, F.J. and ORTLE, D.H. 1973. Experimental<br />

pressure studies of frost heave mechanisms<br />

and the growth-fusi<strong>on</strong> behaviour of ice.<br />

North American C<strong>on</strong>tributi<strong>on</strong>, 2nd fnt. P.F.<br />

C<strong>on</strong>f., Yakutsk, pp.377-384.<br />

ROGGENSACK, W.D. 1977. Geotechnical properties<br />

of fine-grained permafrost soils. Unpub.<br />

Ph.D. Thesis, Univ. of Alberta, Edm<strong>on</strong>t<strong>on</strong>,<br />

Canada.<br />

SAVTGNY, K.W. and MORGENSTERN, N.R. 1986. Creep<br />

behaviour of undisturbed clay permafrost.<br />

Can. Geotech. J., 23(4), pp.515-527.<br />

TSYTOVICB, N.A. 1975. The mechanics of frozen<br />

ground. McGraw Hill.<br />

TABLE 2<br />

Test Data<br />

B Series<br />

1 2 3 4 5<br />

E Series<br />

G Series<br />

1 2 3 4 5 1 2 3 4 5<br />

P Seties<br />

1 2 3 4 5<br />

115 200 138 -1.0 4.33-2<br />

93 14 276 -1.0 2.OE-3<br />

55 414 138 -1.1 4.4E-2<br />

107 276 138 -1.1 8.OE-1<br />

118 207 69 -1.0 2.7-1<br />

120 138 69 -1.1 5.6E-2<br />

79 14 0 -1.3 1.1E-3*<br />

112 4l4 138 -0.7 5.93.0<br />

92 35 0 -0.8 3 4E- 3*<br />

110 276 138 -3.3 9.8E-t*<br />

111 207 138 -3.1 8. IE-l*<br />

81 14 0 -3.0 4.6E-4 22 207 0 -2.0 6.83-2<br />

78 69 0 -3.0 2.OE-3 26 138 0 -2.2 2.1E-2<br />

-1.2 1.9E-2 30 69 0 -2.2' 2.83-3<br />

144 413 0 -1.0 9.8S+l 24 138 0 -1.0 3.3E-2<br />

44 103 0 -2.2 6.73-3 22 69 0 -2.2 1.7-2<br />

74 280 0 -2.4 2.5E-1 28 414P 0 -1.8 1.18+1<br />

-2.9 1.5E-1 276 0 -1.9 1.852.<br />

26 138 0 -2.9 4.03-3 21' 276 138 -1.8 5.43-2<br />

-1.5 6.8E-3 22 138 0 -1.9 5.1E-3<br />

50 413P 0 -1.0 1.9E+1 22 207 0 -2.0 7.6E-1'<br />

1-18 34 0 -2.7 1.8E-3* 26 158 138 -0.8 2.8E-2<br />

104 0 -1.8 6.6E-2* 30 138 0 -1.2 1.3E-2<br />

87 138 0 -2.5 1.3E-2* 74 138 0 -1.2 9.1E-2<br />

254 2761 0 -0.8 1.9EO<br />

-1.0 1.1E-1<br />

96 69 0 -2.5 4.8E-3* 30 64 0 -1.2 3.3E-2<br />

131 207 0 -1.0 4.2E-1 23 207 0 -0.8 7.5E-3<br />

114 138 0 -1.1 8.33-2 23 138 0 -2.8 1.7E-2<br />

151 207 0 -1.0 8.3E-1*<br />

67 414F 0 -1.0 2.6EO<br />

53 69 0 -0.9 1.6E-2<br />

65 69 0 -0.9 1.3B-2<br />

62 689F 0 -1.0 2.2E+2<br />

37 200 0 -3.0 2.1E-2<br />

47 207 0 -2.5 2.83-2<br />

59 6898 0 -1.0 3.33+2<br />

moo 414 o<br />

729 207 0<br />

908 564.. 0<br />

542 35 0<br />

683 69 0<br />

567 138 0<br />

558 690 0<br />

LO77 104 0<br />

861 690 0<br />

531 414<br />

570<br />

I<br />

721 0<br />

725 13BOF 0<br />

549 138 0<br />

138 0<br />

652 69 0<br />

748 1380F 0<br />

482 138 0<br />

409 69 0<br />

448 414 0<br />

496 690 0<br />

181 69 0<br />

69 0<br />

1988 34 0<br />

-3.0<br />

-2.3<br />

-2.3<br />

-2.8<br />

-2.9<br />

-2.9<br />

-2.7<br />

-2.3<br />

-2.3<br />

-1.7<br />

-0.7<br />

-0.7<br />

-1.4<br />

-1.3<br />

-1.9<br />

-0.8<br />

-1.2<br />

-1.3<br />

-1.1<br />

-0.9<br />

-2.1<br />

-2.8<br />

-2.2<br />

2.7EO *<br />

2.w-2<br />

8.MO<br />

6.1E-4<br />

3.0-3<br />

2.4E-2<br />

1,1E+2<br />

1.6E-2*<br />

3.4E+1<br />

1.1E+1<br />

2.4E+2<br />

5.7E*3*<br />

1.6E-2<br />

2.U-2<br />

2.ol-2<br />

2.9E+3*<br />

5.313-2<br />

1.8R-2<br />

4 .OE+l<br />

1.4E+2*<br />

9.73-4<br />

6.8E-4<br />

1.9E-3<br />

I<br />

1140

0 I 2 3 4 5 6<br />

LOG TIME (MIN.1<br />

10 100<br />

TEMPERATURE (1-t) 'C<br />

Fig. 1 Typical %st Data and Interpretati<strong>on</strong> Fig. 2 Creep Data for Ice Compared with Upper Bound Soil Data<br />

1<br />

0 B SERIES<br />

' 0 E SERIES<br />

0 G SERIES<br />

P SERIES<br />

IO" 10- 100 IO"<br />

6, (YEAR)" AT T.- -1.0.c<br />

Fig. 3 B,E,G,P Series Data at Reference Temperature (TR) of -loc<br />

E" (YEAR)" AT rR- -1.0.c<br />

Fiq. 4<br />

B,E,G,P Series Data<br />

1141

108<br />

I<br />

-3.0 a 7 G -4.I.C. rn - 1.0<br />

O B<br />

0<br />

€-(1.35x10")0'" FOR ICE AT T--3.1°C -<br />

FROM MORGENSTERN ETAL 11980)<br />

IO'<br />

lo" 10-3 10- 10-1 I00 10*l<br />

En (YEAR)" AT Tp - -3.dC<br />

Fig. 6<br />

B Series Data<br />

- i<br />

6<br />

IO<br />

lo<br />

0 THIS STUOY<br />

v s<br />

X R<br />

U3 a I3BkPa<br />

IC<br />

E, (YE~R)"AT r,. -I.O'C<br />

Fig. 8 All Series Data -0.5 ST S - 1.50C<br />

1142

PHASE RELAXATION OF THE WATER IN FROZEN GROUND SAMPLES<br />

V.P. Melnikov, L.S. Podenko and A.G. Zavodovski<br />

Institute of Northern Development, Sibirian Branch of the USSR Academy of Sciences, Tyumen, USSR<br />

!Cha kinetictu of phase rel-ti<strong>on</strong> of pore WBter<br />

ie c<strong>on</strong>aidessd to be <strong>on</strong>e of the most Smortant<br />

and oornpliaated aapeats in the pmb-<br />

P em of moisture crystallimati<strong>on</strong> Sa grounds.<br />

The kfxletioa of phase sslarsti<strong>on</strong> -of the m-<br />

tex ip oapilhxy-porous asterns was the<br />

mbjeat of numerow bveetigsti<strong>on</strong>s (Meram,<br />

1978; Errrhov, 1979; Greohiahev, 1980;<br />

Chistotinor, 1973; Eisbtnan, 1985). Acoording<br />

to the data available, deoelerrrti<strong>on</strong> of<br />

moirrtttre cryetallisati<strong>on</strong>, Le, a elow xelaxati<strong>on</strong>,<br />

is oblrened after the equilibrium<br />

temperature -0 entablished (fig. 1<br />

-1<br />

I I I<br />

'T:<br />

T<br />

Fig.1<br />

N<strong>on</strong>-equilibrium Crystallisati<strong>on</strong><br />

of the Water in oapilLarJr - porow<br />

media<br />

1143

thermal xegime of water crystallizati<strong>on</strong>,<br />

fitting to these samples (Kalve, Pmtt, 1963).<br />

Even mall thermal gradients c<strong>on</strong>tribute a lot<br />

to the heat flow, due to the transient processea<br />

of the temperature re-dietributi<strong>on</strong><br />

over the samplels bulk. According to the<br />

data (Nesterov, Danielyan et al., 1984), the<br />

2;, value in quartz 0ands, clay rnbmla,<br />

peat and ground, irrespective of cooling c<strong>on</strong>diti<strong>on</strong>e<br />

of a sample, variee from aome instants<br />

to 45 minutea, influenced by the dispersity<br />

and cherniosl-mineralogical compositi<strong>on</strong> of the<br />

envir<strong>on</strong>ment.<br />

It ma ahown (Liahtwan et al., 1985) that<br />

phatre relazati<strong>on</strong> in peat ssmples, <strong>on</strong>ce the<br />

equilibrium tern eratuxe was eetabliaed, c&p<br />

durate for two bwa. It was also establldd<br />

(Oreobirrhev et al., 1980) that temperature<br />

dt3fQm.U%ti<strong>on</strong>S in lay 8 ~ m lee hat; for tea<br />

daym after the iaothermaf regime ma eatablished.<br />

ThSe thermal retarded eifeot is<br />

aaaooiated with slow pb~e<br />

xe-ti<strong>on</strong> of<br />

ground water ([frechishev et ale, 1980).<br />

It is thus neoeaaary, first, to meawe pb~e<br />

relaxati<strong>on</strong> time of the mter in grounds with<br />

high moisture c<strong>on</strong>tent, taking into aooount<br />

the effect of tmtnsient thermophysical roceseee,<br />

and, sec<strong>on</strong>d, to perform the anafyeie<br />

of a probable influence of sp<strong>on</strong>taneous cryetallizati<strong>on</strong><br />

<strong>on</strong> the kineticrj of the Leathermal<br />

phase rel-ti<strong>on</strong> of the water in grounds with<br />

low moisture c<strong>on</strong>tent.<br />

The a~~lgeie was d<strong>on</strong>e of the kinetics of water<br />

crystallizati<strong>on</strong> fox a number of dieperse<br />

$ateme: quartz sands of different dispernity<br />

( 3-71 mkm: 63-140 dun), kaolinite, m<strong>on</strong>tmorill<strong>on</strong>ite.<br />

The analyrris was oarried out by<br />

the methoda of #canning calorimetry,and NMR,<br />

taking insto‘atscount tlt.anBient ‘thermo hyalael<br />

proaeames. por the soluti<strong>on</strong> of the ffrpt<br />

to& meaaurements were -en at the negative<br />

temperature of the envir<strong>on</strong>ment Tenv. -loo(:<br />

in order ta eliminate the effect of sp<strong>on</strong>ta-<br />

neoua cryatallizatiou, Pox experiments have<br />

ahom that in oase of Bp<strong>on</strong>taneous crystallizati<strong>on</strong><br />

the life-time 02 metartable state<br />

c* 8 1 sr The effioiency of nucleati<strong>on</strong> in<br />

m<strong>on</strong>tmorill<strong>on</strong>ite aam les with moieture o<strong>on</strong>tent<br />

W = 60-75% was etudfed in order to evaluate<br />

the o<strong>on</strong>tributi<strong>on</strong> of water cluaters sg<strong>on</strong>taaeous<br />

cryetalli5ati<strong>on</strong> to the kinetics of the<br />

isothemal ground crystallisati<strong>on</strong>.<br />

Calorimetric meamremente reported were obtained<br />

with Perkin-Elmer quick-rempome<br />

mamiag miorooalorimeter DSC-2 with the time<br />

c<strong>on</strong>stant 0.5 a in the absence of a sam le.<br />

I9MR- measurements were aarried out w i d the<br />

cobxent xebrometer with 0 esating Srequenoy<br />

of 30 laaz (Kibrik, 1980). !&e advantage of<br />

IWR-mearrurements is that transient thermop<br />

dcal prooesses inside of the meaeuring<br />

oe hs 1 do not diatom the results of kinetic<br />

meamreniente of phase compositi<strong>on</strong>.<br />

Relaxati<strong>on</strong> thee of the temperature ST were<br />

estimated for every ample through a atandard<br />

procedure, deaoribed by Kalvr, (19631.<br />

The uial temperature of the measuring cell,<br />

o<strong>on</strong>taining a sample, w m abruptly o<br />

(with the veloaity of 80°C/min) by hang;ed 2-3 C and<br />

the dynamior oi the heat flow q was studied<br />

in the abeenoe of phase transiti<strong>on</strong> proceeeee.<br />

Under these c<strong>on</strong>diti<strong>on</strong>@ the heat flow - AT<br />

re rebenta the kinetics of thermal reexati<strong>on</strong><br />

within the eatu le, where P T in the tempemtmre<br />

difference getween the le and the cell.<br />

!he obtained valuer of the% tl<strong>on</strong> time of<br />

the te erahe 2 in the abaenoe of phare<br />

tranriz<strong>on</strong> procemrs%e do not exoeed 10 e, which<br />

is several orders of magnitude W&r than the<br />

time c<strong>on</strong>stant of the calorlmeter DSO-2.<br />

The estimrrti<strong>on</strong> of relaxati<strong>on</strong> times in waterin<br />

clay mlnerals aad quarts Eandm warn d<strong>on</strong>e with<br />

applying the techniques, tleeoxibed by Heatemv<br />

et al. (19841. A c<strong>on</strong>.t;alneer with a asmple<br />

was placed iato the measuring aell at the<br />

c<strong>on</strong>stant negative wall temperatuxe of -loo&<br />

Aftex Home initial mapercooXing and dewy of<br />

metaetability a self-rrreorder xegiertemmd the<br />

peak value ai o~ydd.li5atiOn (fig.21, charaoteristic<br />

for the majoxity OS the errmplee.<br />

To determine fhe relaxati<strong>on</strong> the of water<br />

the Slog- mt of the themOg= *BS divided<br />

into .motioae at arbitrary equal time<br />

~ppaas an8 interpreted $n temrr of a well<br />

holm method (Beeterov et aZ., 19841, tak<br />

Into acoount $hemal muti<strong>on</strong> of the RIEIU~ e.<br />

The initial moment of temperature relswti<strong>on</strong><br />

was alrenuaed to corresp<strong>on</strong>d to the peak value.<br />

The prooess m e inveatigated up to the time<br />

(C , when the deviati<strong>on</strong>s of the xegirrtrred<br />

ouden from the basic lFna were le130 than 2%<br />

as oom ared with the eak value. A special<br />

estfmafi<strong>on</strong> revealed tLt at time intervale<br />

following CB no more than 1% Srom the<br />

amount of water, rtioipat- in cryetallisati<strong>on</strong><br />

w a @ oxystal p* ized, whioh made up<br />

Lese than 2% from the abnolute total moiarhrse<br />

c<strong>on</strong>tent. For all sam les of quarts d,<br />

m<strong>on</strong>tmorill<strong>on</strong>ite and %aolieife with moleture<br />

c<strong>on</strong>tent Srom 25 to 5% at -1OOC the times<br />

“i: p, evaluated by the method (Neeterov et al.<br />

19841, do not exoeed 20 B.<br />

The measurement* of , obtained by the<br />

P<br />

1144

authors, differ signtfiuantly from $he literature<br />

data <strong>on</strong> (Neeterov st al. , 1984).<br />

P<br />

Tbuar, according to Nesterov et al.. (1984),<br />

tVp = 800 I, whereas according to the authors"<br />

result@, E, 20 s. The particular feature<br />

of our experiments ie that samples, much<br />

smaller in sfze as compared with those decribed<br />

Sn LiPexature, were invastihted, and<br />

meamrements were aaqied out with" Perkin-<br />

Elmer quick-resg<strong>on</strong>ce scapning microcaloripter<br />

DSC-2.<br />

In oFder to analme the discrepancies diacovemd<br />

the dependence ma studied of<br />

from' ,the amowt of the sample, paoked nto<br />

the calorimeter oell. As ir seen in table I<br />

an inoreaee in ia obsemed with increarring<br />

in 'ire mount of !he sample. The bottom line<br />

of table I preaents data <strong>on</strong> %' for the m a<br />

ample. AB it can be men from table I, the<br />

fT value also increases with quantity inoreasing<br />

of the eample, which is true for all<br />

investigated weeas of C .rn.<br />

To oux ]mow, the main c<strong>on</strong>iributi<strong>on</strong>Ao the obtained<br />

valuea of 'T: is given by the temperature<br />

rebti<strong>on</strong> probrree ana water phee<br />

a w e with characteristic timea not exaeeding<br />

20 B.<br />

C<br />

-X<br />

- IC<br />

Fig.3 Equilibrium Diagram Of Unfrozen<br />

Water C<strong>on</strong>tent in Y<strong>on</strong>tmorilL<strong>on</strong>ite<br />

with Moistwe W = 70%.<br />

TABLE 1<br />

Relaxati<strong>on</strong> Times<br />

and Temperalame aa a hcti<strong>on</strong> of<br />

the Sample's hkss<br />

Additi<strong>on</strong>al iaIormEitiOn <strong>on</strong> plum COmp08itiOn<br />

of moicrture and the kinetics of io6 formati<strong>on</strong><br />

in quarts aanda and m<strong>on</strong>tmorill<strong>on</strong>ite wae<br />

obtained tbough tbs nadR-method. Phase compositi<strong>on</strong><br />

of moiature was determined by the<br />

techniquen, described by fice et al. .(1978).<br />

Thus obtained equilibriua diagram of the phase<br />

cornpoetiti<strong>on</strong> of m<strong>on</strong>tmorill<strong>on</strong>ite is presented<br />

in fig. 3. Fig.4 preoeate the dynamics of mass<br />

change in Wrozen watep during its crystallizati<strong>on</strong><br />

in m<strong>on</strong>tmosillanite. The analysis of<br />

the kinetic cwea revcsalsd that ,the pbadte<br />

aompoaitioa of pore water rewine yohanged<br />

after the isotherms1 regime was established.<br />

So, the results of kinetic measurement& <strong>on</strong><br />

water crystallizati<strong>on</strong>, obtained through micsocaloxirne.l;ry<br />

and m, &ow that at -1 OW the<br />

relarati<strong>on</strong> time of the phaae comp<strong>on</strong>iti<strong>on</strong> of<br />

the total amount of nater in capillary-porous<br />

media do not exceed 20 s.<br />

Through NlGi-teobnLquee a l<strong>on</strong>g-term (within<br />

several days) phase rehti<strong>on</strong> of water warn<br />

investigated in m<strong>on</strong>tmorill<strong>on</strong>ite samples of<br />

aharaateristic eiae 0.01 m and with moiature<br />

icc .I<br />

c IC ' 41<br />

Fig.4<br />

Dynamic# of Mass Chuge of<br />

Unfrozen Water in M<strong>on</strong>tmorill<strong>on</strong>ite<br />

with W w 70% at T -lB°C<br />

c<strong>on</strong>tent of 25-12m at -1OOC. Am folLowa from<br />

the data obtained thermal equilibciwn between<br />

the envir<strong>on</strong>ment and the sample me- establiahed,<br />

as a rule. in an hour. Afterward uafrosen<br />

water wam.not mbjected to any changes bey<strong>on</strong>d<br />

the scope of measurement errom. After an hour<br />

the maximum deviati<strong>on</strong> of ualmzen water o<strong>on</strong>teat<br />

from the equilibrium value does not<br />

exceed 10%. Afterward the phase compositi<strong>on</strong><br />

of water remains unchanged for '13 bye. The<br />

results obtained revealed the absence of<br />

l<strong>on</strong>g-term changes of water oompositi<strong>on</strong> in<br />

1145

frozen grounds at -1OOC. Acooxding to olwl data,<br />

the period, at which the e uillbbrium<br />

pharse compositi<strong>on</strong> of water a~rlng moistusesaturated<br />

grounds freeziq ir eprtablished,<br />

doea not exceed 20 s, after the equilibrium<br />

ma established between the envir<strong>on</strong>ment and<br />

the eample. Xn case of large B B les ~ with<br />

high moiature c<strong>on</strong>tent l<strong>on</strong>g-term kaawient<br />

proceases are seemed to be c<strong>on</strong>diti<strong>on</strong>ed by the<br />

temperature re-distributi<strong>on</strong> ovex the ample’s<br />

bulk.<br />

In case of partial moieture e<strong>on</strong>tent pore water<br />

exsista in the iom of clueters. It appears<br />

to lead to a notable increase in the llfetime<br />

of n<strong>on</strong>-equilibrium aupercooled water.<br />

In fact, the experimental reeulte <strong>on</strong> the<br />

life-time of metaetable supercooled Vlem<br />

with moiature c<strong>on</strong>tent 4 45%<br />

revealed<br />

that the Life-time 00 metastable water<br />

at -7OOC bXCeedS 8 hours. b~ general it<br />

meaw that in case of partial moisture c<strong>on</strong>tent<br />

and at temperatures Tmean & -7OC<br />

the procesls of total cryetallizati<strong>on</strong> may be<br />

decelerated due to a sigaifioant life-the<br />

of aeparate clustere of n<strong>on</strong>-equilfbrium m-<br />

pexcooled water.<br />

To etrfimate the mean (%‘“,I value of the<br />

life-time of a BU ercooLed nater cluster<br />

the efficiency $ of nucleatfun waa determined<br />

for m<strong>on</strong>tm8rilloaite with moisture<br />

c<strong>on</strong>tent 60-75% at - 56V. It wa~ eetablished<br />

that j * - 1 06,1-1m-3 at T a -5,6OC*<br />

With the help of correlati<strong>on</strong> (Franks, 1985)<br />

IMLLE, B, WENNERSTROM, H. (1981) . Interprefati<strong>on</strong><br />

of magnetic res<strong>on</strong>ance data from wafer<br />

nuclear in hetero eneouB syatema.<br />

J.Cheh.Phys,, V.75,(4$, 1928-1943.<br />

HEIFETZ, L.1, NEINARK, A.V. (1982). Mnogoghaznie<br />

processi v poristih wedah. Himia,<br />

Moskwa.<br />

KAZVE, E, PRATT, A. (1963). Mikrokalorimetria<br />

Inostrannaya Ziteratura, Moskwa.<br />

KIBRIK, G.E. (1980). Moduliator imgulsnogo<br />

spektrometra yadexnogo magnitnogo rez<strong>on</strong>ansa.<br />

(3). P.T.E.<br />

LISBTWAN, 1.1, BROVKO, GmP, DAVIDOVSKYI, P.1.<br />

(1985). Zssledovanie fazovogo soetava vodi<br />

v forfe kalorimetricheskbn rnetodom.<br />

Ingenarnaya Geologia, Bauka, (4),s.114-<br />

-120.<br />

MELLNIKOV, V.P. (1987). Electrophyzicheskie<br />

iealedovaniya merzlih gorod. Nauka,Moskwa<br />

NESTEROV, 1.1, DANIELIAN, Yes, YANITSKYI,P.A,<br />

GALIEVA, V.N. (1984). Neravnovesnaya kristallizacia<br />

vlagi v merzlih gruntah. Dalnevostochnoe,Otdelenie<br />

Akademii mauk SSSR,<br />

t.277, (4), S.928.<br />

TICE, A.R. BURROUS, C.M, ANDERSON, D.M.(1987).<br />

Corn ositi<strong>on</strong> measurements <strong>on</strong> soila at very<br />

hei! water c<strong>on</strong>tente by pulaed Nuclear<br />

Magnetic 3es<strong>on</strong>ance Tecnique. Trans.Re8.<br />

Bord., 16-20, Washingt<strong>on</strong>.<br />

the mean life-time of a fixed aize cluster<br />

could be estimated. Thus, the %value exceedm<br />

10 da 8 at T -51~6°C and at &e size of<br />

100 &.<br />

This latter proves that deviati<strong>on</strong>e in the<br />

kinetics of themnophysical ohangee in gruunde<br />

within upper horiz<strong>on</strong>s of the oxyolithosope<br />

may be, in many CBaea, c<strong>on</strong>diti<strong>on</strong>ed by oyolio<br />

%emperatwe changes (MelnlkQV , 1 987)<br />

WSHOV, E.D. et al. (1979). Fazovyi 8ostaV<br />

vlagi v merzlih porodah. Moekovskyi Gosudarstvennyi<br />

Univeraitet, Morjkwa.<br />

CI:ISTI)TINOV, L,Sr. ( 1973) . 0 relaksaci<strong>on</strong>nom<br />

haraktere kinetiky kristallizacii vlagy<br />

v gornih gorodah. Sbornik IVroblemi geokxiologii”,<br />

Sibirskoe dtdelenie kkademii<br />

Xauk SSSS.<br />

I;UNKS, F. (1985). Voda i vodnie raatvorl.<br />

pri temperaturah nije OW. Iiaukova Dumka,<br />

Kiev, 338s .<br />

1146

STANDARD METHOD FOR PILE LOAD TESTS IN PERMAFROST<br />

RJ. Neukirchner<br />

Dames & Moore, Golden, Colorado, USA<br />

Synopsis: The completi<strong>on</strong> of a pile load test in permafrost involves the expenditure of<br />

c<strong>on</strong>siderable time and m<strong>on</strong>ey, Documented pile load test programs have been completed using a variety<br />

Of methods; however, no accepted, uniform set of test procedures exists. The American Society for<br />

Teating and Materiala (ASTM) is developing a standard method for c<strong>on</strong>ducting axial compressive pile<br />

load tests in permafrost. This paper outlines the proposed standard test method. It presents .the<br />

key permafrost-related aspects of the test method and discusses the rati<strong>on</strong>ale used in their<br />

development.<br />

INTRODUCTION<br />

The practice of engineering is based in<br />

large part <strong>on</strong> the ability to predict the<br />

behavior of materials in resp<strong>on</strong>se to applied<br />

laading c<strong>on</strong>diti<strong>on</strong>s. Engineers often rely <strong>on</strong><br />

the results of laboratory and field tests <strong>on</strong><br />

teat materials and/or systems to describe the<br />

behavior of real materials and/or systems. In<br />

order to ensure the reliability and<br />

repeatability of the results of these tests,<br />

standard testing methods are used. One of the<br />

major functi<strong>on</strong>s of' the American Society for<br />

Testing and Materials (ASTM) is to assist in<br />

the development, documentati<strong>on</strong> and distributi<strong>on</strong><br />

of standard test methods and procedures. ASTM<br />

has, in 1986, established Subcommittee D18.19,<br />

Frozen Soil and Rock, to address the key issues<br />

associated with the identificati<strong>on</strong>,<br />

classificati<strong>on</strong>, evaluati<strong>on</strong> and testing of<br />

frozen earth materials.<br />

procedures used and teat resulta obtained have<br />

enabled the validati<strong>on</strong> of theories <strong>on</strong><br />

permafrost behavior and the development of<br />

current analytical procedures. Valuable<br />

less<strong>on</strong>s have been learned from each program.<br />

The development of a standard test method<br />

will build <strong>on</strong> the -less<strong>on</strong>s learned to enable<br />

future test programs to proceed with the<br />

knowledge that, if carefully planned and<br />

executed, the data they produce will be<br />

reliable and repeatable and will allow far a<br />

realistic assessment of actual pile behavior.<br />

In the development of any such test<br />

method, however, c<strong>on</strong>flicts between theory and<br />

practice exist. The desire for scientific<br />

purity and precisian are apposed by the limited<br />

time and funds which invariably exist:<br />

compromises must be made. The proposed test<br />

method represents compromises between the<br />

desired and the achievable.<br />

The subcommittee is currently developing a<br />

"Standard Method of Testing Individual Piles in PILE LOAD TEST OBJECTIVES<br />

<strong>Permafrost</strong> Under Static Axial Compressive<br />

Load". Before the standard test method is<br />

The proposed test method will provide data<br />

adopted, it must be reviewed and adopted by the <strong>on</strong> the behavior of the test pile in its<br />

current subcommittee, by committee D-18 <strong>on</strong> Soil envir<strong>on</strong>ment. The test results, in themselves,<br />

and Rock and, finally, by. the overall will not directly provide or c<strong>on</strong>firm design<br />

membership of ASTM. This paper presents the<br />

criteria for actual piles. Inherent<br />

key permafroat-related aspects of the proposed differences between short term and l<strong>on</strong>g term<br />

test method as well as the rati<strong>on</strong>ale used in behavior of frozen materials, physical<br />

its development.<br />

differences between the test pile and the<br />

actual pile and differences in the test pile<br />

BACKGROUND<br />

envir<strong>on</strong>ment (air and ground temperatures) and<br />

the design c<strong>on</strong>diti<strong>on</strong>s for the actual pile must<br />

first be evaluated and accounted for. The load<br />

The completi<strong>on</strong> of pile a load test program test data must be analyzed in light of the<br />

in permafrost involves the expenditure of above.<br />

c<strong>on</strong>siderable time and m<strong>on</strong>ey. Documented pile<br />

load test programs have been completed using a<br />

A satisfactory method for testing piles in<br />

variety of methods. These programs, many of permafrost must provide reliable data <strong>on</strong> the<br />

which are listed in Table 1, have been designed behavior of a loaded test pile which can be<br />

and carried out by leading engineers and<br />

used to predict the behavior of actual piles<br />

organizati<strong>on</strong>s without the benefit of an agreed under actual load c<strong>on</strong>diti<strong>on</strong>s. The test data<br />

up<strong>on</strong>, standard test method or procedure. Each must be adequate to describe the similarities<br />

test program has added to the overall state-of- and to evaluate the differences between the<br />

the-art regarding the behavior of pile test pile and the actual piles. The test data<br />

foundati<strong>on</strong>s in permafrost. The various must be suitable for use with existing<br />

analytical techniques and must be reliable.<br />

1147

TAELE 1 - PARTIAL LlSTlffi OF wBLlSH@ PILE TEST DATA<br />

Pi le EffKtlvl PIIS Instal lstl<strong>on</strong> Type Of<br />

Test<br />

Source TYp4 Dlslstor(m) Procedure Load I na Ouratl<strong>on</strong> (hrl<br />

VyaIw wood (1959)<br />

0.035 Statlc 650-9000<br />

C<strong>on</strong>crete 0.10-0.22 I van Dr<br />

Static 1oM)<br />

Wood 0 .os3 I ncreiwnta 1 lM/losO<br />

Crwy (1963) . wood 0.15-0.25 Slurrlsd I ncrmnta I 24/lwd<br />

StHl PIP*<br />

Stwl H<br />

Wuchayev and Harkln (1971) C<strong>on</strong>crete 0.40 Or I v*n static 360<br />

Johnst<strong>on</strong> and Ladanyl (1972) StHl Rad 0.15 Croutod Static 1KK)<br />

Rowley, Wats<strong>on</strong>, Lad<strong>on</strong>yl (1973) wwd O.

Pile testing must be delayed until freezeback<br />

has occurred and until lateral pressures<br />

generated during freezeback have dissipated to<br />

a nominal level. Temperature measurements will<br />

be used to determine when freezeback occurs.<br />

Lateral stresses, according of Ladanyi et a1<br />

(19871, will be at a maximum after pile driving<br />

or freezeback and will dissipate slowly with<br />

time at a Kate dependent <strong>on</strong> sail type, temperature,<br />

pile geometry and initial lateral<br />

stress. Minimum delay times, after freezeback,<br />

proposed in the test method are shown in Table<br />

2"<br />

APPARATUS FOR APPLYING LOADS<br />

Following is a summary of the key requirements<br />

included in the secti<strong>on</strong> titled "Apparatus<br />

for Applying Loads". The requirements have<br />

been developed to insure accuracy of load applicati<strong>on</strong><br />

and overall test safety. The<br />

requirements are c<strong>on</strong>sistent with past pile load<br />

test procedures dnd are based <strong>on</strong> procedures included<br />

in ASTM D-11431 the equivalerrt standard<br />

procedure for piles in thawed soils.<br />

W<br />

a-Jaek Acrlng Against Anchored<br />

Reference Frame<br />

Cross<br />

Beams<br />

b-Jaek Actlng Agalnst Welghted<br />

Box and Platform<br />

Cross<br />

Beams<br />

Test<br />

Beam(<br />

c-Direct Load Uslng Weighted<br />

Platform<br />

'Sleeve<br />

Casing<br />

or Casing<br />

Figure 1 - Acceptable Loading Systems<br />

Load Applicati<strong>on</strong> may be accomplished by<br />

direct load or through a mechanical or<br />

hydraulic system. Loads may be generated by<br />

known weight, or by jacking against a dead load<br />

or a structural Eramework. Figure 1 shows<br />

three examples of acceptable loading systems.<br />

Accuracy of the loading system must be<br />

maintained to within two percent of the minimum<br />

applied load. Because of the durati<strong>on</strong> of the<br />

tests, load certainty, or reliability, must be<br />

provided. Jacks must be accurately calibrated<br />

at expected test temperatures; load accumulator<br />

devices may be required.<br />

APPARATUS FOR MEASURING MOVEMENT<br />

Following is a summary of the key requirements<br />

included in the secti<strong>on</strong> titled,<br />

"Apparatus for Measuring Movement". The<br />

requirements have been developed to provide for<br />

the acquisiti<strong>on</strong> of reliable data suitable for<br />

use in the analysis of test pile behavior..<br />

A primary and a sec<strong>on</strong>dary system must be<br />

provided for the measurement of axial pile top<br />

movements. Thg primary sys em must have an aecuracy<br />

of 10' in (2.5~10-<br />

h<br />

cm); the seco dary<br />

system pst have an accuracy of lo-' in<br />

(2.5~10- cm). The sec<strong>on</strong>dary system is provided<br />

as an overall check <strong>on</strong> the primary measurement<br />

system.<br />

The reference-beam syste must be designed<br />

and c<strong>on</strong>structed to minimize unaccounted<br />

for<br />

movements. The systems must provide adequate<br />

structural stability and must be shielded from<br />

wind, precipitati<strong>on</strong> and direct sunlight. Each<br />

reference beam must include a temperature<br />

measurement point which is to be periodically<br />

m<strong>on</strong>itored during each test. Prior to a test,<br />

readings of air temperature versus deflecti<strong>on</strong><br />

of the reference beam system must be made and<br />

used as a basis for developing a deflecti<strong>on</strong><br />

correcti<strong>on</strong> for reference beam.temperature,<br />

Incremental strain measurements or intermediate<br />

pile movement measurements are not mandatory<br />

but are included as opti<strong>on</strong>al<br />

requirements in the proposed standard. Either<br />

system would allow an assessment of pile load<br />

distributi<strong>on</strong> with time and depth. The measurement<br />

of lateral pile top movement is also included<br />

as an opti<strong>on</strong>al requirement.<br />

LOADING PROCEDURES<br />

Following is a summary of the key requirementa<br />

included in the secti<strong>on</strong> headed "Loading<br />

Procedures". The standard defines pile failure<br />

as the <strong>on</strong>set of an accelerating creep rate or<br />

incremental deflecti<strong>on</strong>s which increase with<br />

subsequent, uniform time increments. Careful,<br />

periodic measurements of load, pile top<br />

movement, ground temperature and reference beam<br />

temperature must be recorded in order to allow<br />

for proper evaluati<strong>on</strong> of the pile behavior.<br />

The standard defines a Ease Test Load as<br />

the applied load acting <strong>on</strong> the test pile in the<br />

c<strong>on</strong>text of the then-existing ground temperatures<br />

which is equivalent to the actual pile<br />

design load. In order to c0nver.t a Base Test<br />

Load to a design pile load, or vlce-versa, the<br />

engineer must account for differences in ground<br />

1149

temperature during the test period and design<br />

c<strong>on</strong>diti<strong>on</strong>s as well as differences in diameter<br />

and/or length between the teat pile and the design<br />

pile. Published relati<strong>on</strong>ships between<br />

soil strength, or creep, and temperature may be<br />

used to adjust the Base Test Load to the design<br />

pile load.<br />

The current test procedure requires the<br />

engineer to establish a tentative relati<strong>on</strong>ship<br />

between pile load and time to failure. A relati<strong>on</strong>ship<br />

such as that developed by Vyalov<br />

(1959), as illustrated in Figure 2, may be<br />

used. The tentative relati<strong>on</strong>ship will be used<br />

to select a short-term failure load for the<br />

test pile and may be used in the analysis of<br />

load test data. The procedure for loading<br />

piles is given as follows:<br />

o The test load should be applied in a<br />

c<strong>on</strong>tinuous, uniform manner until the<br />

test load is achieved. The load should<br />

be applied quickly (5-10 min.) but not<br />

at a rate which will cause rapid, progressive<br />

failure of the pile during the<br />

loading process. Impact loads are not<br />

permitted.<br />

o The test load should be held at its designated<br />

value until either pile<br />

failure occurs or a *'uniformH creep<br />

rate is obtained. If failure does not<br />

occur, loads must be maintained for a<br />

minimum of three days. Prior to the<br />

load test, the engineer must establish<br />

criteria for defining what c<strong>on</strong>rtitutes<br />

a "uniform" creep rate for the<br />

particular test c<strong>on</strong>diti<strong>on</strong>s.<br />

o After either pile failure or uniform<br />

creep occurs, the applied load should<br />

be removed as quickly as possible and<br />

rebound deflecti<strong>on</strong> measurements shall<br />

be taken.<br />

o The test pile shail remain unloaded for<br />

24 hours before a subsequen test load,<br />

if required, is applied.<br />

TEST PROCEDURE<br />

Base Test Load and the tentative relati<strong>on</strong>ship<br />

between strength and time established, as described<br />

above, by the engineer.<br />

The proposed standard c<strong>on</strong>tains three<br />

acceptable test procedures - Standard, Alternate<br />

and C<strong>on</strong>firmati<strong>on</strong> Test Procedures. Other<br />

acceptable procedures may be added in the<br />

future as either new data, new analytical procedures<br />

or new design needs dictate.<br />

The Standard Test Procedure is the basic<br />

procedure for testing piles in permafrost. It<br />

ig applicable to all soil and ground<br />

temperature c<strong>on</strong>diti<strong>on</strong>8 and should be used where<br />

no other pile test data for similar c<strong>on</strong>diti<strong>on</strong>s<br />

in the same area are available. The procedure<br />

requlres the testing of two piles; cach pile<br />

will be loaded with two test load increments as<br />

listed in Table 3. A creep load increment and<br />

a failure load increment will be applied to<br />

each pile, The Standard Test Procedure will<br />

yield two pile failure load data points and at<br />

least two pile creep load data points for use<br />

in subsequent analysis of test data.<br />

The Alternate Test Procedure is equivalent<br />

to the Standard Test Procedure as regards its<br />

area of applicability. It may be a more useful<br />

procedure in n<strong>on</strong>-ice rich soils. The Alternate<br />

Test Procedure requires the testing of three<br />

piles: each pile will be loaded with <strong>on</strong>e test<br />

load increment as listed in Table 3. Either a<br />

failure load or a creep load increment will be<br />

applied to eqch pile. The Altcrnate Test Procedure<br />

will yield two pile failure load data<br />

points and at least <strong>on</strong>e pile creep load data<br />

point for use in subsequent analyses of test<br />

data.<br />

The C<strong>on</strong>firmati<strong>on</strong> Test Procedure may <strong>on</strong>ly<br />

he used in areas where other pile test data for<br />

similar c<strong>on</strong>diti<strong>on</strong>s are available; it can be<br />

us49 specifically to c<strong>on</strong>firm existing pile<br />

design criteria. The C<strong>on</strong>firmati<strong>on</strong> Test<br />

procedure requires the testing of <strong>on</strong>e pile; the<br />

pile will be loaded with two test load<br />

increments - a creep load increment and a<br />

Lailure load increment - as listed in Table<br />

3. The data from each test load increment must<br />

Following is a of summary the key require- TABLE 3<br />

ments included in the secti<strong>on</strong> headed "Test Pro-<br />

Acceptable Pile Test Procedures<br />

cedures". The test procedures make use of the<br />

c<br />

'a<br />

%<br />

o.,I>Tl zT22n<br />

I<br />

0<br />

Of -<br />

l"(l,O1tO,<br />

Whew -WIWO 8tress<br />

7; -7'Inu to Falluro<br />

q-, , tO-c<strong>on</strong>otants<br />

I<br />

I<br />

Pile Load Load<br />

Procedure No. No. %(') Load Level<br />

Standard 1 1<br />

2<br />

C<br />

F<br />

100% Base Test Load<br />

Failure in 6-12 hrs.<br />

2 1 C 200% Base Test Load<br />

2 F Failure in 3-5 days<br />

Alternate 1 1 F Failure in 3-6 hrs.<br />

2 1 F Failure in 3-5 days<br />

3 1 C 100s Base Test Load<br />

C<strong>on</strong>firmati<strong>on</strong>(') 1 1 C 100% Base Test Load<br />

2 F Failure in 24 hrs.<br />

Note<br />

.OOl I .a1 10.1 1.0 10 100<br />

, 1Day 1 M<strong>on</strong>th (l) C-Creep PSFallure Load; Load<br />

Time to Failure, tf - Yoars<br />

(*) For use in areas where other pile<br />

load test data are available<br />

Figure 2 - Vyalov Relati<strong>on</strong>ship Between Failure Stress and Time<br />

1150

e compared, in the field, to the predicted<br />

creep rate and the predicted failure time. If<br />

either the actual creep rate is greater than<br />

failure the predicted is less creep than<br />

rate the ox if the predicted time time to<br />

to<br />

failure, a sec<strong>on</strong>d pile must be tested. The<br />

sec<strong>on</strong>d pile, if required, would be loaded as<br />

described in Table 3 for the Standard Test<br />

Procedure, test pile number 2.<br />

During each test load increment,<br />

measurements of load, axial movement and<br />

reference beam temperature are to be taken and<br />

recorded at specified time intervals. These<br />

readings must be taken as nearly simultaneously<br />

a8 possible. Ground temperatures must be<br />

measured at least <strong>on</strong>ce a day during each test<br />

load increment.<br />

The test procedures described above are<br />

designed to provide adequate data for analysis<br />

by a qualified engineer or practiti<strong>on</strong>er. Each<br />

test procedure has been set at a minimum level<br />

in order to encourage the organizati<strong>on</strong>s<br />

resp<strong>on</strong>sible for the installati<strong>on</strong> of pile<br />

foundati<strong>on</strong>s in permafrost areas to c<strong>on</strong>duct such<br />

test programs. For large, new Eacilities or<br />

for areas with unusual or complicated<br />

subsurface c<strong>on</strong>diti<strong>on</strong>s, the test procedures<br />

described above should be expanded to include<br />

additi<strong>on</strong>al test piles in order to provide<br />

additi<strong>on</strong>al failure load and creep load<br />

informati<strong>on</strong>. In particular, l<strong>on</strong>ger durati<strong>on</strong><br />

creep load tests should be c<strong>on</strong>ducted in order<br />

to provide a better basis for assessing l<strong>on</strong>g<br />

term behavior of the actual piles.<br />

ASTM is developing a standard test method<br />

for individual piles in permafrost under a<br />

static, axial, compressive load. This test<br />

method, which must be approved by the overall<br />

membership of ASTM, will provide a standard<br />

method for carrying out load tests <strong>on</strong> piles in<br />

permafrost.<br />

The test method includes requirements for<br />

test pile installati<strong>on</strong>, for the apparatus for<br />

applyitig loads, for the apparatus for measuring<br />

pile movement, for pile loading procedures and<br />

for the pile teat procedures.<br />

The development of the proposed test<br />

method has taken into account the less<strong>on</strong>s<br />

learned in previous pile test programs. The<br />

test method, when adopted, will enable future<br />

test programs to proceed with, the knowledge<br />

that the data they produce should be reliable<br />

and repeatable and should allow for a realistic<br />

assessment of actual pile behavior.<br />

REFERENCES<br />

Crory, F.E., (1963) "Pile Foundati<strong>on</strong>s in<br />

<strong>Permafrost</strong>", Proceedings <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>, Lafayette, Ind.,<br />

pp 467-472.<br />

Dipasquale, L., Gerlek, S. and Phukan, A. ,<br />

(1983) "Design and C<strong>on</strong>structi<strong>on</strong> of Pile<br />

Foundati<strong>on</strong>s in the Yuk<strong>on</strong>-Kuekokwim Delta,<br />

Alaska", Proceedings of the Fourth<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>;<br />

Fairbanks, Nati<strong>on</strong>al Academy of Science<br />

Press, pp 232-237.<br />

Dokuchayev, W. and Markin, K., (1971) "Pile<br />

Foundati<strong>on</strong>s in <strong>Permafrost</strong>", in Russian,<br />

Gostroyizdat, 143 pp.<br />

Goff., R.D., (1974), "Pile Foundati<strong>on</strong>s in Arctic<br />

Areas," Preprint, ASCE Nati<strong>on</strong>al Structural<br />

Engineering Meeting, Cincinnati, 26 pp.<br />

Johnst<strong>on</strong>, G.H. and Ladanyi, B. (1972) "Field<br />

Tests of Grouted Rod Anchors Embedded in<br />

<strong>Permafrost</strong>", Canadian Geotechnical<br />

Journal, Vol. 11, No. 4, pp. 531-553.<br />

Ladanyi, B. and Guichaqua, A. (1986) "Time<br />

Dependent B<strong>on</strong>d Regain in Driven Piles in<br />

<strong>Permafrost</strong>, I' Proceedings of the<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> Deep<br />

Foundati<strong>on</strong>s; Beijing, Vol. 1, pp. 2164-<br />

2169 *<br />

Luscher, U. , Black, W.T. and McPhail, J.F.<br />

(1983) "Results of Load Tests. <strong>on</strong><br />

Temperature C<strong>on</strong>trolled Piles . in<br />

<strong>Permafrost</strong>", Proceedings of the Fourth<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>;<br />

Fairbanks, Nati<strong>on</strong>al Academy of Science<br />

Press, pp. 756-761.<br />

Manikian, V. (1983) "Pile Driving and Load<br />

Tests in <strong>Permafrost</strong> For the Kuparuk<br />

Pipeline System," Proceedings of the<br />

Fourth <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong><br />

<strong>Permafrost</strong>: Fairbanks, Nati<strong>on</strong>al Academy of<br />

Science Press, pp. 804-810.<br />

Nix<strong>on</strong>, J.F. (1988) "Pile Load Tests <strong>on</strong> Saline<br />

<strong>Permafrost</strong> at Clyde River, N.W.T.",<br />

Canadian Geotechnical Journal, Vol. 25,<br />

No. 1.<br />

Rowley. B.K., Wats<strong>on</strong>, G.H,, , and Ladanyi, B.<br />

(1973) "Vertical and Lateral Pile Load<br />

Test in <strong>Permafrost</strong>," Proceedings, Sec<strong>on</strong>d<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>,<br />

Yakutsk, North American C<strong>on</strong>tributi<strong>on</strong>, pp.<br />

712-721.<br />

Vyalov, S.S., (1959) "Rheological Properties<br />

and Bearing Capacity of Frozen Soils",<br />

Translati<strong>on</strong> 74, U.S. Army Cold Regi<strong>on</strong>s<br />

<strong>Research</strong> Engineering Laboratory,<br />

translated 1965, 219 pp.<br />

Vyalov, S.S., (1962) "Strength and Creep of<br />

Frozen Soils and Calculati<strong>on</strong>s in ice-soil<br />

Retaining Structures", U.S. Army Cold<br />

Regi<strong>on</strong>s <strong>Research</strong> Engineering Laboratory,<br />

Translati<strong>on</strong> 76, 301 pp.<br />

Vyalov, S.S, (1978) "L<strong>on</strong>g Term Settlement of<br />

Foundati<strong>on</strong>s <strong>on</strong> <strong>Permafrost</strong>", Proceedings,<br />

Third <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong><br />

<strong>Permafrost</strong>, Edm<strong>on</strong>dt<strong>on</strong>, Alta., Vol 1, pp.<br />

898-903.<br />

1151

CRYOGENIC HEAVE UNDER FREEZING OF ROCKS<br />

V.L. Nevecherya<br />

Moscow Geological Prospecting Institute<br />

SYNOPSIS The main regularities of cryogenic heeve of rocko in time and area, obtained<br />

in perennial studies, are given in the work. A new technique was uaed, asserting that cryogenic<br />

heave within bomoganaoua sites, distinguished by z<strong>on</strong>ati<strong>on</strong>, is c<strong>on</strong>sidered a to stochastic be<br />

(random) procesa that allows the probability theory and statistical methods be widely to used fox<br />

a reliable determinati<strong>on</strong> of this pxocesa parameters. Seas<strong>on</strong>al heaving is estimated to regularly<br />

transform into perennial <strong>on</strong>e in neoformati<strong>on</strong> of permafrost. Neverthelesa, a cyclic process of<br />

seas<strong>on</strong>al heaving becomes progressive, whiah reaulta in gradual rise of freezing rocks. The intensify<br />

and irregularity of heaving in an area aharply decreaees with the growth of freezing<br />

depth,<br />

INTRODUCTION<br />

atudying cryogenic heave in soils (SFL-SML)<br />

a new methodology, different from those sccepted<br />

before, has been worked out to study and<br />

Regardless of perennial. investigati<strong>on</strong>s, oxyogenic<br />

(frost) heave under seas<strong>on</strong>al end peren- predict this process, besed <strong>on</strong> the idea that<br />

nial freezing of rock~l has been eo fer insuffi- cry0 enic heave is' c<strong>on</strong>eiderad to be a stochasciently<br />

studied. Inadequate c<strong>on</strong>siderati<strong>on</strong> of tic $random) process, that allows to widely<br />

this process has a harmful impaot, eepecially use the probability theory and statistical<br />

in the seas<strong>on</strong>al freezing-thawing layer (SFL- methods to estimate it in time and area. '<br />

-SML), which reeulta in freezing deforinati<strong>on</strong>s<br />

of various c<strong>on</strong>structi<strong>on</strong>s and primarily linear Analyeis<br />

<strong>on</strong>es (railweye, motor roads pipelines, irrigati<strong>on</strong><br />

channels, communicati<strong>on</strong> lines, atc.). It 18 known that seae<strong>on</strong>al cryogenic heave,<br />

These defomati<strong>on</strong>a do not have cataetrophic cauaing general freezing of heaving rock, ia<br />

R<br />

affects, but they cause c<strong>on</strong>eidexable losses<br />

complex natural process that occurs in certo<br />

nati<strong>on</strong>al ec<strong>on</strong>omy, due to their multiplicity. tain engineering-geological c<strong>on</strong>diti<strong>on</strong>s and is<br />

Active development of the north and east ter- caueed not <strong>on</strong>ly by the rock compositi<strong>on</strong>, but<br />

ritories of the country where dust-clay over- also by thermal-physical and physical-mechaaaturated<br />

soila with deep seaa<strong>on</strong>al freezing- nical regularities of the rock (SFL-SML)<br />

thawing predominate, haa made a further study freezing, Special and time variability of the<br />

of cryogenic procesaee neceSaery. That ia why main engineeri~-geocryological parameters<br />

apecial attenti<strong>on</strong> was paid to cryogenic haavs results in the change of intensity of cryoof<br />

rocks when studying these areas. re- The genic heave for different cites, within c<strong>on</strong>aulta<br />

of perennial investigati<strong>on</strong>s (1958-1986),<br />

siderable limits and in some homogeneous sites<br />

made by the author to develop the technique it is not uniformly manifested in area but as<br />

and to study cryogenic heave in different re- a random (stochastic) process. Thus, when eagi<strong>on</strong>s<br />

of tho countxy, are given briefly in timating cryogenic heave manifestati<strong>on</strong> of the<br />

this report. As a process of cryogenic heave territory, above all ite,z<strong>on</strong>ing (typtfying) io<br />

under seae<strong>on</strong>al freezing is a bit different<br />

made according to this manifestati<strong>on</strong> intensity.<br />

from that under perennial <strong>on</strong>e, they should be With this aim in view a classificati<strong>on</strong> has been<br />

first c<strong>on</strong>sidered separately.<br />

worked out that helps to correlate cryogenic,<br />

heave procerraee with the main natural factors<br />

MECHANISM OF SUPPORT<br />

Before c<strong>on</strong>sidering cryogenic heave under seas<strong>on</strong>al<br />

freezing of rocks, it should be noted<br />

that by the beginning of the 706 a tendency<br />

of permafrost z<strong>on</strong>e development has been chsnged.<br />

Vast area8 are involvad in ec<strong>on</strong>omic development<br />

instead of small <strong>on</strong>eB. A trend in<br />

cryogenic heave lnvestigoti<strong>on</strong>s has also boen<br />

changed since c<strong>on</strong>diti<strong>on</strong>B for c<strong>on</strong>structi<strong>on</strong> were<br />

not everywhere favourable, The main efforts<br />

are focused <strong>on</strong> revealing the intensity of cryogenic<br />

heave manifeatati<strong>on</strong> in an area when developing<br />

these territories. C<strong>on</strong>sequently, for<br />

1152<br />

specifying them: soil (SFL--SML)<br />

CQmpOSitiOn,<br />

moiature before freezing and freezing temperature<br />

regime (Nevecherya, 1973). Depending <strong>on</strong><br />

the combinati<strong>on</strong> of these factors, all the variability<br />

of cryogenic heave through the intensity<br />

of ita manifentati<strong>on</strong> should be subdivided<br />

into four types: I -- rather inteneive; I1 --<br />

intensive; 111 -- week; liV -- hardly manifested.<br />

The type of cryogenic heave baeed <strong>on</strong> the<br />

intensity of its manifestati<strong>on</strong> is determined<br />

by comparative estimati<strong>on</strong> of natural factors<br />

according to the clasaificati<strong>on</strong> (Table I).<br />

For a typifying unit an engineering-geological<br />

subdivisi<strong>on</strong> is accepted that is characterized

y homogeneous factors menti<strong>on</strong>ed above and<br />

diiferent from combinati<strong>on</strong> of these factora<br />

for another subdivisi<strong>on</strong>. At the scale of<br />

1:100,000 - 1:200,000, a natural complex<br />

(micro-area) sineled .out during engineeringgeocryological<br />

aurvey ia accepted to be a<br />

typificati<strong>on</strong> unit. At thw small-scale z<strong>on</strong>ing,<br />

an engineering-geological area and engineeringgeological.<br />

regi<strong>on</strong> are taken for the typificati<strong>on</strong><br />

unit,<br />

In 1965 this technique used for the z<strong>on</strong>ing the<br />

Siberia according to the intenaity of heave<br />

manifestati<strong>on</strong> in soils (BML) for high-way <strong>on</strong>gineering<br />

(Nevecherya,l966). In 1980 the area<br />

between the rivorrj Pur and Nadym (West Siberia)<br />

the z<strong>on</strong>ing was made according to the intensity<br />

of SFL--SML cryogenic heave and a map WQB compiled<br />

to a scale of 1 :100.000 and for the same<br />

areas to a scale of 1 :25.000 (Geocryologicnl<br />

C<strong>on</strong>diti<strong>on</strong>s, 19831,<br />

In 1986 the map of the USSR territory z<strong>on</strong>ing<br />

was compiled together with Belopukhova E.%,<br />

baeed <strong>on</strong> the intensity of cryogenic heave<br />

manifestati<strong>on</strong> in soils of seas<strong>on</strong>al thawing-<br />

-seas<strong>on</strong>al freezing layers, to a scale of<br />

1 :7.500.000. According to the legend, 9 aubdivisi<strong>on</strong>s<br />

of the areas arc made due to the intensity<br />

of cryogenic heave manifestati<strong>on</strong> and<br />

the area of frost-suaceptible soil spreading<br />

within the district.<br />

The reliability of the area subdivisi<strong>on</strong> and<br />

the accuracy of boundaries put <strong>on</strong> the map is<br />

c<strong>on</strong>firmed to a certain degree by actual data<br />

and the data of many authors <strong>on</strong> the progress<br />

in deformati<strong>on</strong> of different structures, caused<br />

by soil heaving.<br />

Thus, as a result of z<strong>on</strong>ing, we obtain 8. qualitative<br />

estimate of the territory based <strong>on</strong> the<br />

intensity of cryogenic heave manifestati<strong>on</strong>.<br />

To determine quantitative parameters of cryowithin<br />

genic heave the typified and their areas<br />

chan $sites), e in time the follow-<br />

and area<br />

ing methods are used. When it is possible to<br />

carry out the work for <strong>on</strong>e or more years within<br />

the typified area, heave measuring plots are<br />

made and regime observati<strong>on</strong>e are carried out.<br />

Jhen making studies within a Bpring-summer<br />

seas<strong>on</strong>, the velue and intensity of heaving is<br />

deterained <strong>on</strong> the baaiE of the technique<br />

suggested by the author and heaving ia estimated<br />

with the value of the frozen heaving<br />

rock wbsidence under thawing. (Nevecherya ,1976).<br />

Since cryogenic heave manifests itaelf as a<br />

random process within homogeneous sites, then<br />

for a reliable determinati<strong>on</strong> of ita parameters<br />

a heave measuring testing gromd ia made <strong>on</strong><br />

the regime-studying plot, where 30 heave-moasuring<br />

devices of different c<strong>on</strong>atructi<strong>on</strong>s are<br />

sct up, according to a certain scheme that<br />

allown to define the nature of heaving show in<br />

area and to obtain data enough for statistical<br />

treatment. The height of marks positi<strong>on</strong> relative<br />

to a specially put bench-mark, not subjected<br />

to heaving, is determined by the levallinp<br />

before freezing (st the n~oment of maximum SML5<br />

and in spring by the end of snow melting before<br />

thawing. The difference botween measurements<br />

give8 the value of total heaving in these<br />

points in a winter was<strong>on</strong>. The dcpth of SPL-<br />

SML is measured with cryopedometcrs, probes or<br />

by drilling probe wells. Nith the data obtained<br />

the mean by depth intensity of cryogenic heave<br />

is determined. To study cryogenic heave by<br />

1153<br />

1<br />

Temperature coefficient<br />

freezina dem./sm<br />

TABLE I<br />

gical Favourable for ’ Unfavourable<br />

composi- heaving, for heaving<br />

ti<strong>on</strong> of<br />

soils<br />

q - 0.10 - 0.15 q w 0.15 or<br />

q E 0.10<br />

cw cr c Wht WbWQ lcr< Wht < Wbwd<br />

’ “b$ ‘bw4 ‘ht ‘bw‘ ‘bw‘ ‘hf<br />

*<br />

wyf Wcr ‘b wcr<br />

Loa;n, dust I*/ 1 I11 TI III IV<br />

Clay, duet I I 111 I1 I11 IV<br />

Sandy loam,<br />

dust I 11 I11 11 I11 IV<br />

Loam T I1 111 TI I11 IV<br />

Sandy loam 1 I1 I11 I1 111 IV<br />

Sand, dust 1 TI I11 I1 I11 IV<br />

Clay I 11 IV 1x1 111 IV<br />

Pine sand I1 111 IY 111 111 Iv<br />

Rock debris<br />

(coarse 1<br />

with 30 per<br />

cent claydust<br />

filler I1 111 IV TIT 111 IV<br />

Peaty soil I1 1x1 IV I11 IV IV<br />

Rock debris<br />

(coarse)<br />

with clayduat<br />

filier<br />

from 10 to<br />

30 per cent. II I11 IV 111 IV IV<br />

Medium- -<br />

size sand I11 I11 IV 111 IV IV<br />

Note: I-IV - numbers come for the type of cryogenic<br />

heave according to the intensity of its<br />

manifeetati<strong>on</strong>, given above.<br />

$vbW - pre-winter moiature of soil (SFL--S&Iz).<br />

If -- full moisture capacity<br />

Wht -- heaving threshold moisture, according<br />

to Kudxyavtsev B.A.<br />

Wcr -- critical moiature according to Sumgin<br />

M.1, and Tsytovich N.A, (Nevecherya,<br />

1973).<br />

depth, a differential heave-measuring -shaped<br />

device is used, and to determine the value of<br />

tangential forces of heaving a -shaped tie<br />

rod with a load goage is umd. On the site<br />

temperature wells ore mad6 and snow-sticks arc<br />

put. To study the tendency of heaving paremetern<br />

change duxing development, atati<strong>on</strong>ary<br />

plots within the sites of disturbed c<strong>on</strong>diti<strong>on</strong>s<br />

and also the sites with apecially disturbed<br />

c<strong>on</strong>diti<strong>on</strong>s have to entablished.<br />

of

The data <strong>on</strong> the total amount of heaving and<br />

mean intensity of cryogenic heave, obtained<br />

in observati<strong>on</strong>s <strong>on</strong> the proving ground using<br />

accelerated technique, can be c<strong>on</strong>sidered as<br />

random values, due to a randomness of cryogenic<br />

heave or as realiaati<strong>on</strong> of a random functi<strong>on</strong><br />

during the analysis of the proceus intensity<br />

dependence <strong>on</strong> space and time coordinates.<br />

That is why corresp<strong>on</strong>ding mathematical methods<br />

are used for the treatment of theae observati<strong>on</strong>s<br />

(Nevecherya, 1978). Without diecusaing<br />

the technique of the data treatment in detail,<br />

it should be noted that to determine spacial<br />

irregularity of cryogenic heave menifestati<strong>on</strong>,<br />

an auto-correlati<strong>on</strong> functi<strong>on</strong> is used, characterizing<br />

a change of interdependence of heaving<br />

value with a distance growths between two mea-<br />

heaving at a point changes within a ve.3; narrow<br />

interval. Changes of the mean, for the proving<br />

ground, value of the heaving total amount are<br />

also small. Tundra, forest tundra and taiga<br />

the increase or decrease of the mean for the<br />

proving ground, value of the heaving total<br />

amount if compared with a previoua seas<strong>on</strong> is<br />

observed in the caae when a cdrrewp<strong>on</strong>ding increage<br />

or decrmse of SFL-SML thickness is<br />

marked. Estimati<strong>on</strong> of this factor impact hao<br />

dem<strong>on</strong>strated that an average, over depth<br />

heaving intensity that doea not depend <strong>on</strong> the<br />

depth of SPL--SIKL, ie a more stable, in-time<br />

value, characteristic of a given cryogenic type.<br />

Thif: has allowed to obtain a formula for determining<br />

8 summarized value of heaving over the<br />

thickneas of SFL-SML. Aa a whole lor the abovcmenti<strong>on</strong>ed<br />

z<strong>on</strong>es the mean ovcr-depth heaving intensity<br />

is characterized ae follows: 6 -- 10<br />

per cent and more for SFL Boils come for the<br />

plots with a very intensive manifestati<strong>on</strong> of<br />

cryogenic heave, 3 - 6 per cent come for plots<br />

with an intensive manifestati<strong>on</strong> and 1 - 3 per<br />

cent come fox the plots with a weak manifestati<strong>on</strong><br />

of cryogenic heave. There in the forest<br />

steppe and steppe z<strong>on</strong>es average over-depth<br />

heaving intensity changes c<strong>on</strong>siderably depending<br />

<strong>on</strong> the pre-winter moisture c<strong>on</strong>tent. Accordsurement<br />

points, An auto-correlati<strong>on</strong> chart ingly, the technique was worked out for detergives<br />

the idea of froat motmde nature in <strong>on</strong> mining pre-winter moisture of soils before<br />

area while the correlati<strong>on</strong> radius value, with freezing <strong>on</strong> the basie of perennial data <strong>on</strong> the<br />

the functi<strong>on</strong> value equal to zero,characteria- nature of moistening in this area (Nevecherya,<br />

tims dimensi<strong>on</strong>s of a separate frost mound. 1966) and for determining moieture c<strong>on</strong>tent ba-<br />

The radiue value allows to obtain a real mean- sed <strong>on</strong> the data of separate measurements in the<br />

ing of irregularity coefficient and a module summer-autumn seas<strong>on</strong> (Nevecherya,l965). It has<br />

of heaving relative irregularity, The irregu- been defined that a correlati<strong>on</strong> radius and, c<strong>on</strong>larity<br />

coefficient value can be determined<br />

sequently, the dimensi<strong>on</strong>s of single frost mounds<br />

the following WRY. Correlati<strong>on</strong> radius deter- under heaving of SFL soils averages IC metres,<br />

mines the length of a separate frost mound. from 15 to 8 m. The size of the frost mounds<br />

In an extreme caae heaving summarized value is under heaving of SML soils amounte to 6-8 m.<br />

equal to a maximum <strong>on</strong>e in the centre of the with the excepti<strong>on</strong> of cites with medalli<strong>on</strong>-like<br />

frost mound and to a minimum <strong>on</strong>e at the edge. apots, where correlati<strong>on</strong> radius amounts 3-4 to<br />

C<strong>on</strong>aequently, the irregularity coefficient i~ m., which coincidea with the dimensi<strong>on</strong>s of<br />

equal to R difference between these values, medalli<strong>on</strong>-like apots in plan. So, the eetabdivided<br />

by a half of aorrelati<strong>on</strong> radius. So liahed type of cryogenic heave corresp<strong>on</strong>ds in<br />

w3 obtain maximum value of Lrregularity coeffi- nature to <strong>on</strong>e of the three types of the sites,<br />

cient that should be c<strong>on</strong>aidered whan estimating singled out due to the intensity of cryogenic<br />

heaving capacity of the territory, Treatment heave. Thua, the data obtained within <strong>on</strong>e-two<br />

of the perennial observati<strong>on</strong>s by means of the winter periods can be c<strong>on</strong>aidered as an average<br />

above menti<strong>on</strong>ed technique helped to raV6al the characteriatica of cryogenic heave of the terrifollowing<br />

regularities of the seas<strong>on</strong>al. cryo- tory. According to the first-year observati<strong>on</strong>s,<br />

genic heave. Fir& of all. it wag Pound out it is possible to determine a minimum number of<br />

that cryogenic heave of aoila (SFL-SML) under heave-measuring marks, basing <strong>on</strong>e self a <strong>on</strong><br />

natural c<strong>on</strong>diti<strong>on</strong>a is a steady process of<br />

gfven reliability and accuracy of heaving mean<br />

annual surface ascending ana descending, its value. It ahould be noted that when developing<br />

parametera changing within comparatively nar- the territory the established type of cryogenic<br />

row limits or being practically unchanged. heave c<strong>on</strong>eiderably changes, but as fer a8 an<br />

Separate frost mound centres are hardly ever<br />

by displaced the data from obtained<br />

year to and year. also This by the ia c<strong>on</strong>firmed average by depth intensity of heaving for ShL<br />

soils does not change, then the data obtained<br />

fact that for natural c<strong>on</strong>diti<strong>on</strong>s can be used for prediccorrelati<strong>on</strong><br />

radius, being very characteristic ti<strong>on</strong>s when estimating soil cryogenic heave.<br />

of the plot, remains almost unchanged for yeara.<br />

It should be noted that the coxxalati<strong>on</strong> radiua It has also been defined that under neoformatincreases<br />

a bit with a growth of heaving mean i<strong>on</strong> of permafrost (PPI a seas<strong>on</strong>al cryogenic<br />

value, that is the dimensi<strong>on</strong>s of a separate heave regularly transforms into a perennial <strong>on</strong>e.<br />

frost mound expand somewhat with the increase Separate aeas<strong>on</strong>al frost mounds turn into growof<br />

the heaving total value. Particular mean- ing frost mounda in proper c<strong>on</strong>diti<strong>on</strong>s: It is<br />

ing of the heave total value at a point is not c<strong>on</strong>firmed by the fact that dimensi<strong>on</strong>s of growc<strong>on</strong>stant.<br />

It changee from year to year but ing frost mounds in plan in the first years are<br />

there is no trend in it. The intensity of theae<br />

equal to those under very inteneive seas<strong>on</strong>al<br />

changes are c<strong>on</strong>siderably detarmined by the cryogenic heave manifestati<strong>on</strong>. Neoformati<strong>on</strong> of<br />

type of natural c<strong>on</strong>diti<strong>on</strong>s. There, within the PF is as 8 rule accompanied by its heaving. In<br />

natural complexes where aoil moisture, the<br />

the southern part of a permafrost z<strong>on</strong>e with a<br />

depth of SFL-SML and c<strong>on</strong>diti<strong>on</strong>s of freezing c<strong>on</strong>aiderable thickness of a mow cover it ie<br />

change a bit from year to year, the value of<br />

cryogenic heave that mekes for the formati<strong>on</strong> of<br />

a short-term permafrost and PF neoformati<strong>on</strong>.<br />

Elevati<strong>on</strong> of the surface as a result of heaving<br />

brings about notable decrease of'the mow-cover<br />

thickness, whit:,. ,lakes lor a eudden cooling of<br />

ground in winter, Particularly intensive heaving<br />

is observed with a growing of perennial<br />

segregated mounds and heaving ridges, c<strong>on</strong>vexhillocky<br />

and large-hillocky peat lands and also<br />

string bogs. To reveal the dynamics Of cryo-<br />

1154<br />

genic heave under perennial freezing, c<strong>on</strong>stant<br />

observati<strong>on</strong>s were organiscd to watch mounds

growing and heaving areas of elevati<strong>on</strong> using<br />

special marks and bench marks. Observati<strong>on</strong>s<br />

were initiated in 1971-72 years and axe being<br />

c<strong>on</strong>tinued todate. To determine the age of<br />

the mounds and c<strong>on</strong>sequently average heaving<br />

rate, the method was used of field comparative<br />

intcxpretati<strong>on</strong> of aerial photographs (@I) fox<br />

different years (Geocryological c<strong>on</strong>diti<strong>on</strong>s,<br />

1983). It has been determined thet under perennial<br />

soil freezing cryogenic heave manlfeate<br />

itself as B eeas<strong>on</strong>al (cyclic) <strong>on</strong>e, i.e. it<br />

lasts for a certain period each year. The<br />

start of the heaving period and its durati<strong>on</strong><br />

is determined by the depth of perennial freezing<br />

and intensity of winter cooling our of<br />

soils, that actively shows itself under heave<br />

segregati<strong>on</strong> mounds growth. Cryogenic heave<br />

rate. decreases abruptly with the permafrost<br />

thicknese. Thus in the year of the mound formati<strong>on</strong>#<br />

i.e. when seas<strong>on</strong>al freezing turns into<br />

perennial <strong>on</strong>e, the rate of cryogenic heave<br />

amounts to 200-250 mm per year, With a growth<br />

of permafrost thickness from 1.5 mm to 3 mm<br />

the rate decreases Prom 130 to 60 mm per year.<br />

vJith permafrost thickness below the mound being<br />

8 mm and other favourable c<strong>on</strong>diti<strong>on</strong>s, cryogenic<br />

heave rate amounts to 7-10 m/y. In permafrost<br />

and rare permafrost island z<strong>on</strong>e the<br />

growth of seperate frost mounds in unfrozen<br />

layer ceaaee, the thickness of newly-formed<br />

PF being 10-1 5 mm. A change of height is noted<br />

of such mounds within 10-30 mm over the years<br />

caused by displacement of the PP lower boundsry<br />

in heaving soil with a change of heaving<br />

mound therms1 state in Bome winter seas<strong>on</strong>a.<br />

With a c<strong>on</strong>stant increaee of soil temperature,<br />

an elevati<strong>on</strong> takes place of the PI lower Burface,<br />

causing the mound settlement with the<br />

rate of 60-200 nun per year and then its feilure.<br />

Cryogenic heave with an areal PF formati<strong>on</strong><br />

is also noted, but its rate is markedly<br />

lower than with frost mound growth. In permafrost<br />

island z<strong>on</strong>e it amounts to 5-15 m/y.<br />

It should be noted that when developing the<br />

territory, the intensificatian of perennial<br />

cryogenic heave is often observed and frost<br />

mound growth is resumed that in natural c<strong>on</strong>diti<strong>on</strong>s<br />

does not occur.<br />

COBCL!JSIOW<br />

ThuE, cryogenic heave manifests itself as B<br />

limited process under Reas<strong>on</strong>s1 and perennial<br />

gsound freezing. However, when seas<strong>on</strong>al frsezing<br />

transforms into perennial <strong>on</strong>e, cryogenic<br />

heave turns from o cyclic process into a cyclic<br />

pxogreseive, and that brings about gradual<br />

elevati<strong>on</strong> of some layers and the freezing<br />

ground surface to a c<strong>on</strong>siderable height. It<br />

should be taken into c<strong>on</strong>siderati<strong>on</strong> when making<br />

geological and geomorphological investigati<strong>on</strong>s<br />

in permafrost z<strong>on</strong>e. Heaving irregularity occurring<br />

under seaa<strong>on</strong>el freezing causes various<br />

ice c<strong>on</strong>tent of the upper 10-15 rn thickness of<br />

PF homogeneous as to compositi<strong>on</strong> and total moisture.<br />

Metodicheskie rekomendataii PO pxognozu izmereniya<br />

inzhenexno-geologicheakikh ualovii i<br />

razvitiya criogennykh protaesaov pri<br />

lineinom stroitelstve v severno-tayozhnoi<br />

z<strong>on</strong>e Zapadnoi Sibfrf (1976). Nauchn, red.<br />

Nevecherya V.L., M., YSEGINGEO, 44<br />

Nevecherya V.L., (1965). 0 metodike rascheta<br />

predzimnei vlszhnosti gruntov yuga Zepadnoi<br />

Sibiri. V kn.: "Izvestiya SO AN SSSR",<br />

vyp. 3, N 10, 134-1 39, Novosibirak.<br />

Nevecherya V,z. (1966 1. K voproau prOgnOBirovaniya<br />

predzimnei vlazhnoati gruntovykh<br />

oanovanii zheleznykh dorog Zapadnoi Sibixi,.<br />

. V kn. : "Mexzlotnye iasledovaniya".<br />

Vyp, 5, 100-1 11, Moskovskii Universitet ,<br />

Moakwa.<br />

Nevecherya, V.L. (19661, K xsi<strong>on</strong>irovsniyu<br />

Zapadnoi Sibiri PO infenaivnosti protses-<br />

8ov puchino-obrazovaniya v gruntakh.<br />

V kn. 8 Waterialy VI11 Vseeoyuzn. mezhved.<br />

aoveshch. po geokxiologii, vyp. 3, 53-59.<br />

Yakutak.<br />

Nevccherya, V.L. (1973). K metodike rai<strong>on</strong>irovaniya<br />

territorfi PO intensivnoati proyavleniya<br />

protaeaEtov puchinoobrszovaniya<br />

v gruntakh. V kn.: "Uskorennye metody<br />

inzhenerno-geologichaekogo fzucheniya<br />

nefte-gaz<strong>on</strong>osnykh raianov Zapadnoi Sibiri<br />

na oanove landshaftnoi indikatsii,<br />

Trudy VSEGINGEO, vyp. 62, 21-27. Moskwa.<br />

Nevecherya,V.L., Goralchuk M.I. (1978). Nekotorye<br />

zak<strong>on</strong>ornernosti sez<strong>on</strong>nogo putcheniya<br />

gruntov v severotayozhnoi z<strong>on</strong>e Zapadnoi<br />

Sibiri. V kn,: Krfgennye @rOtsessy.<br />

177-188. tlNauka*t, Moskwa.<br />

RElJEREIJC ES<br />

Geologicheskiye uslovia Znpadno-Sibimkoi e;sz<strong>on</strong>osnoi<br />

provintsii, (1983). Izd-vo "Nauka",<br />

Sibirskoye otdeler.ie, Novosibirsk, 197 s.<br />

1155

EFFECTIVE LIFE IN CREEP OF FROZEN SOILS<br />

V.R. Parameswaran<br />

Department of Materials Science and Engineering, Northwestern University,<br />

Evanst<strong>on</strong>, IL 60208 USA<br />

SYNOPSIS<br />

A new method to predict the <strong>on</strong>set of failure in the creep of frozen soils is suggested. By this technique an<br />

effective life l<strong>on</strong>ger than that predicted from the time to reach minimum creep rate or the time of transiti<strong>on</strong> from<br />

steady state to accelerating creep, can be obtained during the performance of<br />

a structure prior to ultimate failure.<br />

Using a pers<strong>on</strong>al computer to m<strong>on</strong>itor the performance of the foundati<strong>on</strong>, a warning signal can be activated prior to<br />

the <strong>on</strong>set of failure.<br />

INTRODUCTION<br />

Bearing capacities of foundati<strong>on</strong>s in permafrost areas<br />

are governed by the strength and creep of frozen soils.<br />

A pile foundati<strong>on</strong> for fnstance, bears the load due to<br />

the structure mainly by the adfreeze b<strong>on</strong>d strength at<br />

the pile-soil interface, and partly by end bearing. If<br />

the ground can be assumed to c<strong>on</strong>sist essentially of <strong>on</strong>e<br />

type of soil c<strong>on</strong>sidered homogeneous, the above two<br />

factors can be combined to calculate the total bearing<br />

capacity 9 as:<br />

where Tad. is the shear strength of the adfreezing b<strong>on</strong>d<br />

at the pile-soil interface, is the adfreezing<br />

interfacial area, u is the l<strong>on</strong>iaeerm strength of the<br />

soil in compressi<strong>on</strong> and Ab is the end bearing area of<br />

the pile tip. Thus the important parameters that<br />

govern the bearing capacity are: the l<strong>on</strong>g term<br />

adf reeze b<strong>on</strong>d strength between a pi le and the soil (T),<br />

and the l<strong>on</strong>g term strength of the soil under<br />

compressi<strong>on</strong> (u). The objective of any good design is<br />

to arrtve at suitable (or allowable) values of the<br />

stresses T and U, so that they are not exceeded in<br />

practice.<br />

The soil around the pile is under a c<strong>on</strong>stant load creep<br />

c<strong>on</strong>diti<strong>on</strong>, and the pile is c<strong>on</strong>tinuously being displaced<br />

at a rate (although imperceptibly small) that depends<br />

<strong>on</strong> the applied load, temperature, physical<br />

characteristics such as grain size, Ice c<strong>on</strong>tent,<br />

porosity etc. of the soll, surface characteristics of<br />

the pile, and several other factors. In practice,<br />

based <strong>on</strong> an allowable settlement to occur during the<br />

anticipated life of the structure, an allowable rate of<br />

pi.le displacement or settlement is calculated. The<br />

stress corresp<strong>on</strong>ding to this allowable displacement<br />

rate has to be determined in order to arrive at the<br />

number of piles required to support a structure.<br />

*Formerly Senior <strong>Research</strong> Officer. Institute for<br />

<strong>Research</strong> in C<strong>on</strong>structi<strong>on</strong>, Nati<strong>on</strong>al <strong>Research</strong> Council<br />

Canada<br />

of<br />

Three different approaches to obtain the allowable<br />

stresses T and U, were reviewed earlier (Parameswaran,<br />

1985a, 1986). In <strong>on</strong>e approach, stress obtained by<br />

extrapolati<strong>on</strong> of the results from rate c<strong>on</strong>trolled tests<br />

carried out at higher rates, to a lower allowable<br />

displacement rate, is always much higher than that<br />

obtained from c<strong>on</strong>stant load creep tests carried out at<br />

the lower displacement rates. In the sec<strong>on</strong>d method,<br />

the allowable stress is determined from a plot of<br />

applied stress vs the minlmum or steady state creep<br />

rate observed in creep tests, neglecting the<br />

instantaneous displacement and primary creep. In the<br />

third method proposed by Vyalov (1959, 1962) tne<br />

failure time tf (defined as the time at which sec<strong>on</strong>dary<br />

or steady state creep ends and tertiary or accelerating<br />

creep starts) is related to the applied stress -C at the<br />

pile-soil interface, by an equati<strong>on</strong>:<br />

where t and -c0 are characteristic c<strong>on</strong>stants for the<br />

soil d e r c<strong>on</strong>siderati<strong>on</strong>. (In the case of creep tests<br />

carried out <strong>on</strong> frozen soil material in the form of<br />

samples of cylindrical or other shape, the shear stress<br />

z in equati<strong>on</strong> 2 is replaced by the compressive or<br />

tensile stress u). From a plot of In (t ) vs<br />

l/(stress). the allowable str,ess for an expected life<br />

is calculated.<br />

Al the three methods underestimate the allowable life<br />

of a structure in frozen soil under a given load,<br />

because, in general, frozen soils creep with a<br />

prol<strong>on</strong>ged tertiary creep regi<strong>on</strong>. A much l<strong>on</strong>ger failure<br />

time extending into the early part of tertiary creep<br />

regi<strong>on</strong> can be chosen by a method proposed recently for<br />

determtnati<strong>on</strong> of failure time in creep in any material<br />

(Parameswaran, 1987). The method is based <strong>on</strong> the<br />

premise that failure time in creep can be taken as the<br />

time at which the straight line from the origin to the<br />

point corresp<strong>on</strong>ding to the displacement (or strain) <strong>on</strong><br />

the creep curve becomes a tangent to the curve. At<br />

this point, the slope of the line, which is equal to<br />

the total displacement or strain divided by the elapsed<br />

time since the beginning of a test, is also a minimum.<br />

In this paper, results from several creep tests cdrried<br />

1156

out in the permafrost laboratories of the Institute for<br />

<strong>Research</strong> in C<strong>on</strong>structi<strong>on</strong>, <strong>on</strong> piles embedded in frozen<br />

soils as well as those carried out <strong>on</strong> cylindrical<br />

samples of frozen soils, are analyzed and it is shown<br />

that the effective life of a structure can be increased<br />

by at least 50% more than that based <strong>on</strong> Vyalov's<br />

definiti<strong>on</strong> of failure time.<br />

ANALYSIS OF TEST DATA<br />

Experimental methods and materials used for model pile<br />

tests and creep tests in frozen soils were described in<br />

earlier papers (Parameswaran, 1979, 1985b). Figures 1<br />

and 2 show typical creep curves where the displacement<br />

and displacement rate of a pile embedded in a frozen<br />

soil and subjected to a c<strong>on</strong>stant load, are plotted as a<br />

functi<strong>on</strong> of time, in (a) and (b), respectively.<br />

Similar creep curves for a cylindrical sample of frozen<br />

sand (Figure 2) show the variati<strong>on</strong> of strain and strain<br />

rate respectively, with time. The times denoted by tl<br />

and t in these Figures represent the beginning and end<br />

$of t$e sec<strong>on</strong>dary or steady state creep regi<strong>on</strong>.<br />

Although engineering creep curves obtalned by plotting<br />

the variati<strong>on</strong> of displacement or strain with time show<br />

a pseudo-steady-state regi<strong>on</strong> (as in Figures (a) of 1 to<br />

3), strictly speaking there is not a truly steady state<br />

regi<strong>on</strong> where the rate of displacement or strain remains<br />

c<strong>on</strong>stant for the period tl to t2, The rate of<br />

displacement or strain decreases c<strong>on</strong>tinuously until it<br />

reaches a minimum at t , after which it increases, as<br />

shown in the Figures (by of 1 to 3. The failure time<br />

t used by Vyalov in equati<strong>on</strong> (2) is the same as t2 in<br />

Ffgures 1 to 3. It may, however, be more accurate to<br />

use t instead of t , although this reduces the<br />

effectrve life of the structure c<strong>on</strong>siderably.<br />

The time t corresp<strong>on</strong>ds to the point <strong>on</strong> the creep curve<br />

at which tge straight line from the origin is a tangent<br />

to the curve. The slope of a line from the origin to<br />

any point lying <strong>on</strong> the creep curve is given by the<br />

total displacement at that point divided by the elapsed<br />

time, and this slope is a minimum at the point<br />

corres'p<strong>on</strong>ding to t3. As pointed out earlier<br />

(Parameswaran, 1987) it wil be c<strong>on</strong>venient to use the<br />

time t instead of t2 or t , as the failure time for<br />

calculaling the optimum s!ress in the design of<br />

foundati<strong>on</strong>s for structures in frozen ground. This wil<br />

give a much l<strong>on</strong>ger effective life of a structure built<br />

<strong>on</strong> perennially frozen ground.<br />

An error in estimatlng the failure time tJ Is likely to<br />

have a somewhat greater effect than an error in<br />

estimating tm, as the former is in the tertiary or<br />

accelerating creep regi<strong>on</strong>, where the creep rate<br />

Increases muoh faster with tlme than in the vicinity of<br />

However, as frozen soils under stresses usually<br />

h:ountered in the field (1 MPa) exhibit a prol<strong>on</strong>ged<br />

tertiary creep regi<strong>on</strong>, preventive measures can be taken<br />

prior to the <strong>on</strong>set of actual failure of a structure.<br />

1.<br />

E<br />

E<br />

" 1.<br />

z<br />

Y<br />

z<br />

5<br />

0<br />

v)<br />

l.L t 1<br />

0.<br />

- 0.<br />

a<br />

1.0<br />

I I l l 1 I I<br />

0.<br />

0.<br />

TIME. h<br />

2<br />

YI<br />

-<br />

El 10"<br />

I 1 1 1 1 1 I<br />

0 20 40 60 80 100 120 140 160 180<br />

TIME. h<br />

FIGURE 1 Typical creep curves for a steel pile in<br />

frozen sand at -2.5.C<br />

(stress: 0.215 MPa, moisture c<strong>on</strong>tent: 14%)<br />

a Variati<strong>on</strong> of displacement with time<br />

I1 b Variati<strong>on</strong> of the rate of displacement<br />

with time<br />

1157<br />

I ,ItrnI I , , 1<br />

10"0 40 80 120 160 200 240 280<br />

TIME. h<br />

FIGURE 2 Creep curves for a wood pile in frozen silty<br />

clay at -6'C<br />

(stress: 0.315 MPa, moisture c<strong>on</strong>tent in soil:<br />

40%)

101 2 9<br />

h<br />

TIME, h<br />

FIGURE 3 Typical creep curve for a frozen cylindrical<br />

sand sample at -1O'C (stress: 6.4 MPa,<br />

moisture c<strong>on</strong>tent of sample: 20%)<br />

a) Variati<strong>on</strong> of axial strain wlth time<br />

b) Variati<strong>on</strong> of strain rate with time<br />

The displacement of a pile can be m<strong>on</strong>itored<br />

c<strong>on</strong>tinuously as a functi<strong>on</strong> of time by a device such as<br />

a linear variable differential transformer, and the<br />

data stored using a suitable data logger and a<br />

microcomputer. The slope at each instant, calculated<br />

automatically by dividing the total displacement by the<br />

elapsed time, can be compared with previous values.<br />

The instant at which this ratio starts to increase<br />

significantly after reaching a minimum value can be<br />

determined by the computer, and a warning signal can be<br />

issued to take preventive measures to avoid<br />

catastrophic failure. This method has been used<br />

successfully in laboratory experiments <strong>on</strong> creep of<br />

frozen soils and <strong>on</strong> model pile foundati<strong>on</strong>s in frozen<br />

soils.<br />

The times corresp<strong>on</strong>ding to the various polnts al<strong>on</strong>g the<br />

creep curves (such as those shown in Ftgures 1 and 2)<br />

for model piles frozen in various soils and subjected<br />

to c<strong>on</strong>stant loads are given in Table I. The table also<br />

shows the temperature and stress at the pile-soil<br />

interface during each test. Table I1 is similar to<br />

Table I except that the data shown there are obtained<br />

from creep curves (such as that shown in Figure 3) for<br />

cylindrical samples tested under c<strong>on</strong>stant uniaxial<br />

compressive stress. It is evident frpm these tables<br />

that the fallure time as def/ned by It3 is much l<strong>on</strong>ger<br />

than that defined by It (the time to attaln the<br />

minimum creep rate) or '!2', the time for transiti<strong>on</strong><br />

from stage 2 to stage 3 creep. The ratio (t3 / t ) has<br />

a value of about 1.5 in most cases, and the ratio of<br />

(t3/ tm) is larger than 2 in most cases. This shows<br />

that at a particular temperature and stress, the useful<br />

llfe predicted for foundati<strong>on</strong>s of structures built in<br />

perennially frozen ground could indeed be enhanced by<br />

c<strong>on</strong>sidering the time t as the fallure time instead of<br />

tm or t2. Alternativejy, for a structure designed for<br />

a lifetime of t2, the limiting or allowable stress <strong>on</strong> a<br />

pile foundati<strong>on</strong> can be increased due to the extended<br />

failure time, thereby resulting in some savings.<br />

TABLE I<br />

TYPICAL CREEP DATA FOR PILES IN FROZEN SOILS (REF. FIG, 1 AND 2 FOR TIMES t, t7, tq)<br />

Ttmp . Minimum Tlme to Reach Time at the<br />

Test c Stress Creep Min. rate Creep Rate End of Stage 11<br />

No. Material (t0.2) MPa m/s tm, S t2, s Time t3. S t3/t2 t3/tm<br />

36 Wood Pile -6 0.447 5.6 x 10'8 2.52 x ios 8.28 X io5 1.44 x 106 1.74 5.71<br />

in Sand<br />

42 -2.5 0.285 2.5 x 9.00 x lo5 1.58 X lo6 2.38 x lo6 1.51 2.63<br />

30 Wood Pile in -2.5 0.544 4 x 3.60 x io4 6-12 x lo4 8.64 x 104 1.472.40<br />

silty so11<br />

75 Wood Pile -6 0.365 5.5 x 1.26 x io5 2.52 X io5 5.4 x 104 2.14 4.29<br />

in clay<br />

79 Creosoted<br />

wood pile<br />

-6 0.442 9.7 x 2.16 x lo5 7.20 x IO5 1.44 x lo6 2.00 6.67<br />

in clay<br />

41 Steel Pipe -6 0.447 2.5 x lom6 7.92 X IO4 9.36 X io4 1.33 x lo5 1.42 1.68<br />

Pile in Sand<br />

37<br />

I1 -2.5 0.215 3.9 x 10-7 1.80 x 105 3.60 x 105 5.04 x lo5 1.40 2.80<br />

51 II -2.5 0.175 1.1 x 10-5 5.76 X 103 1.19 X 104 1.91 x lo' 1.60 3.32<br />

20 C<strong>on</strong>crete<br />

Pile in Sand<br />

-2.5 0.238 6.7 x low7 2.16 x IO5 3.60 X lo5 4.68 x lo5 1.30 2.17<br />

65 C<strong>on</strong>crete 11 0.222 2.5 x 10-7 9.00 X 104 1.98 X 105 3.06 x lo5 1.55 3.40<br />

Pile in Silty<br />

Soi 1<br />

1158

TABLE I1<br />

TYPICAL CREEP DATA FOR CYLINDRICAL SAMPLES OF FROZEN SOILS<br />

Typ. Minimum Time to Reach Time at the<br />

Test C Stress Creep rate Min. Creep Rate End of Stage I1<br />

No. Material (k0.2) MPa s-1 tm, 5 t2, 5 time tg, S t3/t2 t3/tm<br />

35 Frozen sand -10 7.45 9.0 x 10-7 2.27 x 104 3.60 X 104 5.40 x lo4 1.50 2.38<br />

(20% ice)<br />

I II<br />

36 8.65 1.8 x loW6 1.01 x lo4 1.62 x lo4 2.52 x lo4 1.56 2.50<br />

II<br />

38 6.48 1.6 x 104 9.00 x 104 1.44 x 105 2.41 x 105 1.67 2.68<br />

I1 I1<br />

39 6.72 6.5 x lom7 2.34 x lo4 , 3.60 x lo4 5.40 x 104 1.50 2.31<br />

I1<br />

21 -3 2.37 8.7 x 10-9 5.40 x lo5 . 1.19.~ lo6 1.80 x 106 1.51 3.33<br />

II I1<br />

26<br />

3.32 1.1 x 10-7 1.69 x 105 2.16 x 105 3.24 x lo6 1.501.92<br />

II I1<br />

27<br />

3.11 9.1 x 10-8 1.26 x 105 2.15 x 105 3.24 x 106 1.50 2.57<br />

47 Frozen clay -10 3.50 2.8 x lom6 5.40 x 103 8.28 x lo3 1.80 x 104 2.17 3.33<br />

(50% ice)<br />

I1 I1<br />

48 2.10 7.6 x 10-3 1.08 x 104 1.44 x 104 4.68 x IO4 3.25 4.33<br />

II II<br />

49 3.17 1.8 x lom5 2.52 X lo3 3.24 x lo3 5.40 x lo3 1.67 2.14<br />

I1 I1<br />

19 0.78 1.7 x 1.44 x lo5 3.46 x lo5 5.40 x lo5 1.56 3.75<br />

CONCLUSIONS<br />

A new c<strong>on</strong>cept of failure time ln the creep of frozen<br />

soils extending into .the tertiary creep regime Is<br />

proposed. According to this c<strong>on</strong>cept, the failure time<br />

can be taken as that point <strong>on</strong> the creep curve at which<br />

the slope of the stralght line joining the origin<br />

(which is equal to the total displacement up to that<br />

time divided by the elapsed time) is a mlnlmum, and the<br />

line becomes a tangent to the curve at that point.<br />

Data from several creep tests of loaded piles in frozen<br />

soils as well cylindrical samples of frozen Soil5 under<br />

compressi<strong>on</strong> were analyzed, and it was shown that the<br />

failure time so estimated is 1.5 to 2 times larger than<br />

the c<strong>on</strong>venti<strong>on</strong>al failure time defined as the time to<br />

reach minimum creep rate in the sec<strong>on</strong>dary creep regi<strong>on</strong><br />

or the end of the steady state creep regime. This<br />

extended failure time thus prol<strong>on</strong>gs c<strong>on</strong>siderably the<br />

useful life of structures built in permafrost areas.<br />

The method can also be used to determine the <strong>on</strong>set of<br />

failure by creep of a foundati<strong>on</strong> in frozen soil, and to<br />

take preventive measures prior to <strong>on</strong>set of catastrophic<br />

failure,<br />

ACKNOWLEDGEMENTS<br />

The research reported in this paper was carried out at<br />

the Institute for <strong>Research</strong> in C<strong>on</strong>structi<strong>on</strong>, Nati<strong>on</strong>al<br />

<strong>Research</strong> Council of Canada. Colin Hubbs c<strong>on</strong>ducted most<br />

of the tests reported here, Douglas Bright and Harold<br />

Dah1 interfaced the creep tests with a desk top<br />

Computer through an automatic data logger, and Doug<br />

Scott did the illustrati<strong>on</strong>s. The author appreciates<br />

their help and extends his sincere thanks to all of<br />

them.<br />

REFERENCES<br />

Parameswaran, V.R. (1979). Creep of model piles in<br />

frozen soils. Canadian Geotechni cal Journal, Vol<br />

16, p. 69.<br />

Parameswaran, V.R. (1985a). Attenuating creep of piles<br />

in frozen soils. Proceedings of Sessi<strong>on</strong>:<br />

"Foundati<strong>on</strong>s in <strong>Permafrost</strong> and Seas<strong>on</strong>al Frost",<br />

ASCE Spring C<strong>on</strong>venti<strong>on</strong>, pp. 16-28.<br />

Parameswaran, V.R. (1985b). Effect of alternating<br />

stress <strong>on</strong> the creep of frozen soils. Mechanics of<br />

Materlals. Vol . 4, p. 109.<br />

Parameswaran, V.R. (1986). Bearing capacity<br />

calculati<strong>on</strong>s for piles in permafrost.<br />

Proceedings, Fourth <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, Cold<br />

Regi<strong>on</strong>s Engineering, Anchorage, Alaska, pp,.<br />

751-759.<br />

Parameswaran, V.R. (1987). Failure time in creep.<br />

Mechanics of Materials, Vol. 6, pp. 89-91.<br />

Vyalov, S.S. (1959). Rheological properties and beartng<br />

capacity of frozen soils. (Izdatel 'Stvo Akademii<br />

Nauk SSR, Moscow), U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong><br />

and Engineering Laboratory Translati<strong>on</strong> No, 74, 219<br />

P.<br />

Vyalov, S.S. (editor) (1962). The strength and creep of<br />

frozen Soil5 and calculati<strong>on</strong>s for ice-soil<br />

retaining structures. (Izdatel 'Stvo Akademii Nauk<br />

SSR, Moscow), U.S. Army CRREL Translati<strong>on</strong> No. 76,<br />

301 P.<br />

1159

HORIZONTAL FROST HEAVE FORCE ACTING ON THE RETAINING<br />

WALL IN SEASONAL FROZEN REGIONS<br />

Shui, Tieling and Na, Wenjie<br />

Heil<strong>on</strong>gjiang Provincial Institute of Water C<strong>on</strong>servancy, Harbin, China<br />

SYNOPSIS Based <strong>on</strong> the studies<br />

of developmental process and distributi<strong>on</strong> al<strong>on</strong>g a retaining<br />

wall of horiz<strong>on</strong>tal frost heave force acting <strong>on</strong> the wall, this paper presents a simplified chart of<br />

stress distributi<strong>on</strong> of the horiz<strong>on</strong>tal frost heave force to determine the value of maximum horiz<strong>on</strong>tal<br />

frost heave force, and provides a design basis for the safety operati<strong>on</strong> of the retaining wall in<br />

seas<strong>on</strong>al frost regi<strong>on</strong>s. According to the distributi<strong>on</strong> characteristics of the horiz<strong>on</strong>tal frost heave<br />

force, the affected scope of horiz<strong>on</strong>tal frost heave force in the soil at the back of the retaining<br />

wall and the proposed fill secti<strong>on</strong> for the protecti<strong>on</strong> of frost hazard can be identified.<br />

NATURAL<br />

CONDITIONS OF THE TESTING SITB<br />

TABLE I1<br />

The tested soils in the test site are heavy silty Frost Depth,Groundwater Table and Maximum Frost Heave<br />

loam,The physical properties of the soil samples Amount at the Test Site From 1982 to 1986<br />

taken from different depths are shown in Table I.<br />

The mean air temperature at the Harbin Frozen<br />

Ground Test Site is 3.5 degree Centigrade. The<br />

lowest temperature is -38.5 degree Centigrade,<br />

and maximum freezing index is 2371 degree-days.<br />

The frost depth, groundwater table and the<br />

maximum frost amount at the test site from 1982<br />

Yrs<br />

It ems<br />

Frost heave 142<br />

amount (mm)<br />

to 1986 are shown in Table 11. Frost depth 150<br />

(cm)<br />

DEVELOPMENTAL OCESS' AND DISTRIBUTION OF<br />

HORIZONTAL FRO% HEAV,E *FORCE<br />

1982-83 1983-84 1984-85 1985-86<br />

170 161 286 ,<br />

160 154 134<br />

Groundwater 140-300 110-340 90-297 60-260<br />

depth (cm)<br />

When it is in the double directi,<strong>on</strong> freezing<br />

state, the freezing line in s'oil at the back of surface to curce, then<br />

to straingt line again parala<br />

retaining wall, transits from shaight line<br />

le1 to the base of the wall (Fig.1).<br />

paralled to the top of the wall<br />

k<br />

near ground<br />

TABLE I<br />

Physic-a1 Properties of the Soil Tested Taken From Different Depths<br />

Soil<br />

Compositi<strong>on</strong> of Plastic Liquid Plastic<br />

'<br />

classifi- depth soil grain (2) limit limit index gravity Specific<br />

' 'dati<strong>on</strong>. (Cm) > d o 5 .05-

PRESSURE CHART AND AFFECTED SCOPE<br />

Fig.1 Horiz<strong>on</strong>tal Frost Heave Force Acting <strong>on</strong> the<br />

Retaining Wall Under Two-directi<strong>on</strong>al Freezing<br />

1- ice lenses, 2 - directi<strong>on</strong> of frost heave force,<br />

an - frost heave force,<br />

5 - tangential frost heave force,<br />

q, - horiz<strong>on</strong>tal frost heave force.<br />

Frost heave force (On ) is always normal to the<br />

freezing line fr<strong>on</strong>t. horiz<strong>on</strong>tal comp<strong>on</strong>ent, 'h<br />

of <strong>on</strong> is the 1.7riz<strong>on</strong>tal frost heave force discussed<br />

in thl, paper.<br />

The deve1opme':al process of horiz<strong>on</strong>tal frost<br />

heave force a- ing <strong>on</strong> the retaining wall can be<br />

divided into fodr stages: a) Formati<strong>on</strong> stage.<br />

With the cha .e of temperature from plus to<br />

minus, the soil at the back of the retaining<br />

wall begins r' freeze and generates the horiz<strong>on</strong>tal<br />

frost heave force oh. This stage generally<br />

lasts frorn '.he middle October to late November.<br />

b) Increase stage. Negative temperature<br />

falls c<strong>on</strong>tinuo sly, and freezing depth increases.<br />

The horiz<strong>on</strong>tal frost heave force increases<br />

gradually and rzaches its maximum value, This<br />

stage is from i 2cember to March. c) Decaying<br />

stage. When the weather becomes warmer, the<br />

thawing of the soil initiates. The horiz<strong>on</strong>tal<br />

frost heave force decreases gradually, which<br />

occurs in late March. d) Disappear stage. When<br />

the soil is completely thawed, the frost heave<br />

force will disappear accordingly (Xu, 1983).<br />

Fig.2 shows the variati<strong>on</strong> of the horiz<strong>on</strong>tal<br />

frost heave force (oh) acting <strong>on</strong> the unit area<br />

of the retaining wall with different exposed<br />

height (h) observed at the test site in two<br />

winters of 1984-1985 and 1985-1986, respectively.<br />

The distributi<strong>on</strong> of horiz<strong>on</strong>tal. frost heave force<br />

al<strong>on</strong>g the height of the retaining wall is approximately<br />

triangular. With the increase in<br />

frost depth,5h increases almost linearly, and<br />

after reaching its maximum value at a certain<br />

depth, it decreases with increasing depth. The<br />

distributi<strong>on</strong> of horiz<strong>on</strong>tal frost heave force<br />

al<strong>on</strong>g the depth measured in the winters of<br />

1984-1985 and 1985-1986 were shown in Fig.3 and<br />

4, respectively.<br />

The occurencc time uf maximum Oh acting <strong>on</strong> the<br />

retaining walls with diffcrent heights is not<br />

synchr<strong>on</strong>ous.<br />

Check of stability and strength of the retaining<br />

wall should be made according to the maximum<br />

value of oh occured <strong>on</strong> the wall c<strong>on</strong>cerned. It<br />

is, however, impossible and impractical to give<br />

out so many pressure charts for the walls with<br />

different height. It is advised to design the<br />

wall according to the pressure chart with the<br />

envelope of the maximum value of oh measured<br />

from 1984 to 1986, which can be simplified as<br />

a trapezoid, as shown in Fig.5, The simplified<br />

char.t can be divided into the exposed and buried<br />

parts. The maximum value of "h appears at the<br />

secti<strong>on</strong> located from 1/2 to 213 of the exposed<br />

height of the wall (from B to C). The value of<br />

oh at the +ase of the exposed part (D) is about<br />

60'percent of the maximum value; while at the<br />

maximum frost depth (E) the value of Oh equals,<br />

to zero. The maximum frost depth (Hm) beneath<br />

the wall is 110 cm from the natural ground surface.<br />

The pressure chart proposed above is suitable<br />

<strong>on</strong>ly when the height of the wall is as 0.8 to<br />

1.2 times high as the local maximum frost depth<br />

and the soil at the back of the retaining wall<br />

is heavy silty loam, Table I11 shows the comparis<strong>on</strong><br />

between the designed and the measuredvalue<br />

of oh. For the heavy silty loam fill material<br />

with large frost heave at the upper part and<br />

null heave at the base, it is proposed to take<br />

the maximum value of oh of 0.25.MPa as the design<br />

value for the retaining wall. According<br />

to the process of temperature variati<strong>on</strong> in filling<br />

soil and the pressure chart of oh, the affected<br />

scope of oh <strong>on</strong> the back of the retaining<br />

wall can be determined. In practical engineering<br />

the affected scope can be c<strong>on</strong>sidered as the<br />

fill secti<strong>on</strong> for the protecti<strong>on</strong> of the frost<br />

heave. The simplified fill secti<strong>on</strong> behind the<br />

wall can be determined as follows: Identifying<br />

E at 2/3. of the height of the exposed wall from<br />

the top and drawing a horiz<strong>on</strong>tal line from E<br />

to D, let ED equal to the maximum frost depth<br />

Hm. From F at the base of the wall at which<br />

the buried depth is the same as the maximum<br />

frost depth Hm, drawing a horiz<strong>on</strong>tal line to<br />

G. let FG equal to the half of Hm. Then, from<br />

A at the top of the wall, making BAC equal to<br />

40°, drawi.ng a straight line to intersect wiLh<br />

GD at C (see Fig,6). The area of ACDG is the<br />

scope of effect of horiz<strong>on</strong>tal, frost heave force.<br />

Within the area the fine-grained soil needs to<br />

be replaced to prevent frost damage.<br />

CONSLUSIONS<br />

The amount and distributi<strong>on</strong> of horiz<strong>on</strong>tal frost<br />

heave force acting <strong>on</strong> the lateral surface of a<br />

retaining wall have a close relati<strong>on</strong>ship tu the<br />

height of the wall exposcd and change with the<br />

development of frost penetrati<strong>on</strong>. 'l'he maximum<br />

value of oh acting <strong>on</strong> the different parts of<br />

the retaining wall does not occur synchr<strong>on</strong>ously.<br />

For a fully-restricted low retaining wall wi.th

I<br />

0.15-<br />

M<strong>on</strong>lh<br />

M<strong>on</strong>lh<br />

Fig.2 Variati<strong>on</strong> of Horiz<strong>on</strong>tal Frost Heave Force with Time for the<br />

Retaining Walls with Exposed Height of:<br />

(a) 0-20.cm,(b) 20-40 cm, (c) 40-60 cm, (d) 60-80 cm,<br />

(e) 80-120 cm, (f) 100-120 cm, (8) 120-140 cm and<br />

(h) 140-160 cm, respectively, and in two winters of<br />

1984-1985 (solid line) and of 1985-1986 (broken line).<br />

TABLE I11<br />

Comparis<strong>on</strong> Between the Deeigned and Measured Value<br />

of Oh<br />

Measured value of<br />

Exposed height<br />

oh (MPa)<br />

Designed value<br />

of the wall h<br />

of Oh (MPa)<br />

(cm) 1984-1985 1985-1986<br />

20<br />

40<br />

60<br />

80<br />

100<br />

120<br />

140<br />

160<br />

0.025<br />

0.137<br />

0.131<br />

0.220<br />

0.197<br />

0,200<br />

0.192<br />

0.150<br />

0,047<br />

0.150<br />

0.149<br />

0.191<br />

0.208<br />

0.091<br />

-<br />

0.06<br />

0.125<br />

0.185<br />

0.25<br />

0.25<br />

0.25<br />

0.205<br />

0,15<br />

backfill of heavy silty loam with large frost<br />

heave at the upper part and null. heave at the<br />

Lower part, the retaining wall can he designed<br />

according to that the maximum value of oh is<br />

equal to 0.25 MPa and O C C U ~ S at 2/3 of the<br />

height of the wall exposed. The pressure chart<br />

can be drawn by means of t.he simplified method<br />

presented in this paper.<br />

ACKNOWLEDGEMENT<br />

'Thanks are ext.ended to Mr.Jinng Liqiang and Mr+<br />

Li Dashan for their help in this study.<br />

1162

0.12<br />

12'<br />

-<br />

0-<br />

II<br />

u<br />

= 40-<br />

80 -<br />

I20 -<br />

180 -<br />

151<br />

;+<br />

0.176<br />

;:.<br />

0.124<br />

161<br />

0.2<br />

Fig.<br />

Distributi<strong>on</strong> of On al<strong>on</strong>g the Height of Retaining Wall Observed <strong>on</strong> the Date of:<br />

(1) Dec.10, (2) Jan.7, (3) Jan.19, (4) Feb.4, (5) Feb.26, (6) March 4,<br />

(7) March 18 and (8) the maximum value in the winter of 1984-1985.<br />

80<br />

\ 120 4:t<br />

0.084 0.175<br />

151<br />

Fig.4 Distributi<strong>on</strong> 0:<br />

Uh al<strong>on</strong>g the Height of Rctakning Wall Observed un the Date of:<br />

(1) Dec.16, (2) Jan 14, (3) Jan.24, (4) Jan.28, (5) Feb.24, (6) March 6 ,<br />

(7) March 13, (8) March 20 and (9) the maximum value in the winter of 1985-1986.<br />

1163

0<br />

W<br />

0<br />

u<br />

Fig.5 Simplified Pressure Chart of Oh<br />

al<strong>on</strong>g the Retaining Wall<br />

1 - observed in 1984-1985,<br />

2 - observed in 1985-1986.<br />

A<br />

B<br />

-<br />

Fig.6 Fill Secti<strong>on</strong> behind a Retaining Wall<br />

REFERENCE<br />

Xu Shaoxin, (1983). On frost heave force in<br />

foundati<strong>on</strong>. Proceedings of the Scc<strong>on</strong>d<br />

Nati<strong>on</strong>al <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>, 229-232,<br />

Gansu Publishing House, Lanzhou, China.<br />

1164

DYNAMIC LOAD EFFECT ON SETTLEMENT OF MODEL PILES IN FROZEN SAND<br />

D.L. Stelzer and O.B. Andersland<br />

Departement of Civil and Envir<strong>on</strong>mental Engineering, Michigan State University, East Lansing, Michigan 48824 USA<br />

SYNOPSIS Small cyclic loads superimposed <strong>on</strong> a sustained ile load will, in some frozen<br />

ground situati<strong>on</strong>s, increase pile settlement rates to lFvels whfch significantly lower their design<br />

capacity. To provide more informati<strong>on</strong> <strong>on</strong> this problem, model pile tests were c<strong>on</strong>ducted to determine<br />

the influence of cyclic load frequency and load amplitude <strong>on</strong> displacement (settlement) rates I<br />

in frozen sand. Experimental results showed that cyclic loads significantly increased model pile<br />

displacement rates over those observed for the sustained load. The measured displacement (creep)<br />

rates were essentially independent of frequency for small cyclic loads superimposed <strong>on</strong> a sustained<br />

load in the range of 0.1 Hz to 10 Hz. Data analysis suggests that creep theory, with an experimental<br />

creep parameter and known loads, can be used for predicti<strong>on</strong> of the increase in pile<br />

displacement rates.<br />

INT'RODUCTLON<br />

Small cyclic loads superimposed <strong>on</strong> a static<br />

pile load will, in some frozen ground situati<strong>on</strong>s,<br />

increase pile settlement rates and<br />

significantly lower their design capacity. this<br />

situati<strong>on</strong> may arise fqr piles in perennially<br />

frozen ground which are used to support vibrating<br />

machinery (turbines, power generators, or<br />

compressors) or traveling loads (cranes or fork<br />

lift trucks). Pile design criteria normally<br />

limit shaft stresses at the pile/frozen soil<br />

interface to values which will give no more<br />

than 25 mm pile displacement aurin the service<br />

life of the structure. Small cyclc loads, 5<br />

percent of the l<strong>on</strong>g-term sustained load, will<br />

accelerate settlement (displacement) rates of<br />

piles embedded in frozen ground (Parameswaran,<br />

1984). An increase in pile surface roughness<br />

(additi<strong>on</strong> of corrugati<strong>on</strong>s or lugs) will increase<br />

adfreeze b<strong>on</strong>d strength for both shortand<br />

l<strong>on</strong>g-term loads (Thomas and Lusher, 1980;<br />

Andersland and Alwahhab, 1983; Ladanyi and<br />

Guichaoua, 1985). The basic mechanisms by<br />

A - MODEL PILE<br />

B ~ THERMISTOR<br />

C FROZEN SAND<br />

D SOIL RESTRAINT<br />

E COOLANT CIRCULATION<br />

F DISPLACEMENT TRANSDUCERS<br />

G - DISPL. & TIME RECORDING<br />

H - FORCE TRANSDUCER<br />

I - FORCE RECORDING<br />

J - 360 DEGREE PIVOT<br />

K - RINGS ON KNIFE EDGES<br />

L LEVER ARM<br />

M - STATIC WEIGHT<br />

0 - ELECdODYNAMIC SHAKER<br />

p - DYNAMIC LOADING CONTROLS<br />

Q TEMPERATURE RECORDING<br />

FIG. 1<br />

EXPERIMENTAL SYSTEM FOR MODEL PILE TESTS.

which small cyclic loads increase pile settlement<br />

rates and a suitable theory for estimati<strong>on</strong><br />

of this increase remain unknown.<br />

To provide more informati<strong>on</strong> <strong>on</strong> this problem,<br />

experimental tests have been c<strong>on</strong>ducted to<br />

determine the de endence of model pile displacement<br />

rate& Tn f,rozen sand <strong>on</strong> several<br />

c<strong>on</strong>trolled variables. These variables included<br />

cyclic load amplitude, frequency of load applicati<strong>on</strong>.<br />

static load, sand density, ice volume<br />

fracti<strong>on</strong>, temperature, and pile surface roughness.<br />

After iliitial rupture of ice adhesi<strong>on</strong> at<br />

the pile/frozen soil interface, the load was<br />

supported primarily by interacti<strong>on</strong> between the<br />

frozen sand and protrusi<strong>on</strong>s (lugs) <strong>on</strong> the model<br />

pile. Melting of ice and water movement away<br />

from high pressure points, accompanied by a<br />

breakdown and formati<strong>on</strong> of new b<strong>on</strong>ds between<br />

the ice and soil grains, permits adjustment or<br />

movement of particles interacting with<br />

dependent displacement (creep) which appeared<br />

to be dependent primarily <strong>on</strong> the static load.<br />

Applicati<strong>on</strong> of a dynamic load increased displacement<br />

rates for all dynamic load amplitudes<br />

at the various frequencies.<br />

EXPERIMENTAL PROCEDURES<br />

Model Pile Set-ug<br />

A plain 9.52 mm steel bar with <strong>on</strong>e 1.59 mm high<br />

lug, embedded in a frozen sand specimen (Fig.<br />

I), served as a model pile secti<strong>on</strong> suitable for<br />

dynamically loaded pull-out tests. The leading<br />

edge of the lug was perpendicular to the pile<br />

shaft. The frozen sand represents frozen<br />

slurry which is used to fill the annulus around<br />

piles in the field. The washed, uniformly<br />

graded, silica sand (particle size range of<br />

0.420 mm to 0.595 nun) was combined with<br />

distilled water to form 152 mm dialpeter by 152<br />

mm high frozen specimens with the model pile<br />

embedded vertically in the center. Preparati<strong>on</strong><br />

procedures gave an average void ratio close to<br />

0.581 with an ice matrix density close to 0.892<br />

gm/cu cm. Sample freezing was permitted l<strong>on</strong>gitudinally<br />

al<strong>on</strong>g the pile wigh the temperature<br />

allowed to stabilize at -14 C. After removal<br />

from the mold, the frozen sample, model pile,<br />

and reacti<strong>on</strong> plate were enclosed within a<br />

rubber membrane to prevent c<strong>on</strong>taminati<strong>on</strong> by the<br />

coolant fluid. The sample and pile were then<br />

attached to the restraint bracket of the static<br />

and dynamic loading system within the empty<br />

coolant tank. A refrigerated ethylene glycol/<br />

water coolant mixture was pumped into and<br />

circulated through the coolant tank for immediate<br />

and subsequent temperature c<strong>on</strong>trol<br />

during testing. A thermistor embedded in the<br />

frozen sand (38 mm from lug) permitted<br />

temperatures to be m<strong>on</strong>itored a8 required.<br />

m n g , three displacement transducers<br />

(LVDT) and a force transducer were<br />

mounted near the top of the model pile.<br />

Additi<strong>on</strong>al insulati<strong>on</strong> was placed <strong>on</strong> top of the<br />

coolant tank and around the pile c<strong>on</strong>necti<strong>on</strong>s so<br />

as to minimize any temperature fluctuati<strong>on</strong>s.<br />

LoAD * I 254 N I * 1 254 N * I 254 N *<br />

I I 1<br />

I * SEE TEST CONDITIONS AS IN FIG. 3<br />

- SEE<br />

FIG. 3<br />

/'<br />

-<br />

- /*<br />

.'<br />

BEHAVIOR DURING LEVER<br />

ARM ADJUSTMENT<br />

i/"<br />

,,"<br />

/*<br />

0 10 20 30 40 50 60 70 80<br />

TIME, t ,(hr)<br />

FIG. 2 DISPLACEMENT-TIHE CURVES FOR A MODEL RILE IN FROZEN SAND AT A TEMPERATURE OF -3.0 'C.<br />

1166<br />

J

2.20 kN 2.34 kN<br />

n<br />

LJ LJ hJ<br />

2.20' ICN 2.26 m 2.2O'kU<br />

50.2 x +10.2 7.<br />

+10.2 x<br />

@ 1.0 Hz $ 0.1 Hz<br />

@ 10 Hz<br />

50 51 52 53 54<br />

TIME, t (hr)<br />

FIG. 3 DISPUCEMENT-TIHE CURVE FOB A MODEL PIE3 'IN FROZEN SAND SBWING<br />

THE RELATIONSHIP FOR TESTS VI11 THR(I1GB XI ON SAMPLE 92.<br />

/<br />

3 20.75<br />

Y<br />

W<br />

t<br />

TEST IX<br />

E 20.70<br />

3 20.65<br />

m<br />

H<br />

n<br />

9 20.60<br />

E<br />

AD<br />

V<br />

2.20 kN<br />

t<br />

g21.53<br />

3 21.58<br />

Y<br />

w<br />

f<br />

8<br />

3 21.48<br />

m<br />

CI<br />

n<br />

t<br />

321*43 E<br />

TIME. t (hr)<br />

TEST X<br />

2.20 kN<br />

0<br />

0<br />

-f r<br />

m m<br />

VI<br />

ul<br />

VI<br />

YI<br />

":<br />

3<br />

r m<br />

Wt ul 3<br />

TIME, t (hr)<br />

FIG. 4 DISPLACEMENT-TIME CURVES FOR A MODEL PILE IN FROZEN SAID, TESTS VI11 THROUGH XI, SAMPLE 92.<br />

1167

The coolant, loading system, pile, and froze8<br />

sand were allowed to stabilize at -3.0 & 0.1 C.<br />

The desired static load was,then placed <strong>on</strong> the<br />

pile through the lever system illustrated in<br />

Fig. 1. Displacement, temperature, and force<br />

were recorded relative to elapsed time of test.<br />

The static load was maintained until pile<br />

movement slowed to essentially a c<strong>on</strong>stant<br />

displacement rate (Fig. 2). A dynamic force,<br />

with the desired wave form, frequency, and<br />

force amplitude, was generated by the electrodynamic<br />

shaker attached to the lover arm<br />

(Fig. 1). This force, m<strong>on</strong>ikored by the load<br />

cell, was transferred to the top of the model<br />

pile thru very stiff c<strong>on</strong>nectians. Overall<br />

results for several tests <strong>on</strong> <strong>on</strong>e sample are<br />

illustrated in Fig. 2. The periods of low load<br />

(254 N) which follow each high load (2.20 kN)<br />

were necessary to reset the lever arm (Fig. 1).<br />

Dynamic loading during the third period of high<br />

stress in Fiq. 2 18 illustrated in Fig. 3. Each<br />

dynamic loading period was preceded by and<br />

followed by a l<strong>on</strong>ger static load period to<br />

allow return to a nearly c<strong>on</strong>stant displacement<br />

rate. Careful m<strong>on</strong>itoring during 0.100 mm displacement<br />

before and after the start of a<br />

dynamic load provided data such as illustrated<br />

in Fig. 4. This technique gave data least<br />

effected by other variables for observing the<br />

dynamic load effect <strong>on</strong> displacement rates.<br />

EXPERIMENTAL RESULTS<br />

Model pile displacements were recorded as a<br />

functi<strong>on</strong> of time for several variables. Results<br />

presented in this paper include the influence<br />

of static loads, dynamic loads, ar:,3 frequency.<br />

The effects of soil dry density, ice fracti<strong>on</strong>,<br />

pile surface roughness, and temperature, are to<br />

be covered in a subsequent paper. A typical<br />

displacement-time curve involving <strong>on</strong>e sample<br />

and several tests is illustrated by the overall<br />

curve in Fig. 2; Loads are included at the top<br />

of Fig. 2. At about 7 mm displacement after<br />

initial loading or 3 to 4 mm after each lever<br />

arm adjustment, primary creep decreased to a<br />

nearly c<strong>on</strong>stant rate and dynamic load tests<br />

were started. <strong>on</strong> a larger scale, a test series<br />

is shown in Fig. 3 with detailed informati<strong>on</strong> in<br />

Fig. 4 for about 0.100 mm displacement immediately<br />

before and after applicati<strong>on</strong> of the<br />

three dynamic and <strong>on</strong>e static load changes. Beat<br />

fit straight lines over the 0.100 mm displacement,<br />

immediately before and after a load<br />

change, ave average displacement rates during<br />

that perfod of time. Test XI in Fig. 4 ,<br />

showing the effect of a 6.5 percent increase in<br />

static load <strong>on</strong> the displacement rate, has been<br />

included for comparis<strong>on</strong>.<br />

A com aris<strong>on</strong> of displacement rates, measured<br />

immedfately before and after a load change, did<br />

not always clearly show the effect of a test<br />

variable. To illustrate the effect's magnitude,<br />

the ratio of displacement rate after<br />

dynamic loading to that immediately before the<br />

load change was used. These normalized displacement<br />

ratios have been plotted against<br />

frequency in Fig. 5 for a static load of 2.2 )rN<br />

and include three different groups of superimposed<br />

dynamic loads. The dynamic load was a<br />

sine curve waveform with a single peak value<br />

e ual to the percent of static load given in<br />

Fygs. 5 and 6. Lines c<strong>on</strong>necting individual<br />

data points in ~ig. 5 represent several series<br />

of tests similar to the series shown in Fig. 3.<br />

During dynamic loading at 1.0 Hz and 6.2 HZ,<br />

moti<strong>on</strong> of the static weight (Fig. 1) placed<br />

small additi<strong>on</strong>al loads <strong>on</strong> the model pile. Since<br />

these forces could not be accounted for, data<br />

at the test system frequencies of 1.0 and 6.2<br />

Hz have been omitted in Fig. 5. The pile-soil<br />

res<strong>on</strong>ant frequency, as described by Schmid<br />

(1969), should be much higher than the 10 Hz<br />

attainable with equipment available for this<br />

study. Three levels of dynamic loading, at<br />

frequencies between 0.1 Hz and 10 Hz, provided<br />

a range of increased displacement rates.<br />

;DISCUSSION<br />

I<br />

CY<br />

the experimental data, summarized in Fig. 5,<br />

lshows that model pile displacement rates in<br />

frozen sand were essentially independent of<br />

/frequency in the range of 0.1 Hz to 10 Hz. This<br />

lbehavior is in agreement with work reported b<br />

1969) for model brass piles embedded In<br />

formly qraued, quartz sand with the<br />

same particle size range. Schmid (1969)<br />

Ireported a pile-soil res<strong>on</strong>ance at about 50 Hz<br />

with a relatively flat peak in his load versus<br />

lfrequency curve. This curve, with a relatively<br />

flat resp<strong>on</strong>se, suggests frequency independence<br />

above and below res<strong>on</strong>ance. The smaller model<br />

steel pile and stiff frdzen sand used in this<br />

stud should give a higher res<strong>on</strong>ant frequency<br />

and 'its displacement should be relatively<br />

frequency independent for 0.1 Hz to 10 HZ.<br />

Observed res<strong>on</strong>ant frequencies close to 1.0 Hz<br />

and 6.2 HZ were clearly due to the loading<br />

system since they could be altered by changing<br />

the Loading arm set-up.<br />

Amalitude Effed<br />

An increase in Uynamic load amplitude significantly<br />

increased pile displacement rates over<br />

rates observed for sustained loads (Fig. 5).<br />

Comparis<strong>on</strong>s show rate increases rou hly in<br />

proporti<strong>on</strong> to increase in load ampltudes,<br />

i.e., the rate was approximately doubled when<br />

load amplitude was doubled. Since several<br />

tests were run <strong>on</strong> <strong>on</strong>e frozen Sam le, a creep<br />

rate measured just prior to applycati<strong>on</strong> of the<br />

dynamic load might differ from rates for<br />

subsequent tests <strong>on</strong> the same sample. To compare<br />

tests performed at different initial creep<br />

rates, the ratio b, / b, was plotted against<br />

6, as shown in Fig. 6. Data for each of the<br />

three best fit lines corresp<strong>on</strong>ds to a given<br />

dynamic load amplitude. The small negative<br />

slopes may show the effect of starting tests at<br />

various displacement rates before sec<strong>on</strong>dary<br />

creep was fully attained. Points <strong>on</strong> the left<br />

in Fig. 6 would be closer ,to the minimum or<br />

sec<strong>on</strong>dary creep rate. In additi<strong>on</strong>, 4 shaded<br />

data points (indicated by a slash) represent<br />

displacement rate increases for a small static<br />

load increase. For a d namic load amplitude<br />

equal to a static load Increase, the dynamic<br />

rate increase always appeared as some fracti<strong>on</strong><br />

of the static rate increase. The observed<br />

model pile behavior suggested that displacement<br />

rate increases might be related to creep<br />

behavior.<br />

Creee fntere retatim<br />

The approximate l<strong>on</strong>g-term time-dependent porti<strong>on</strong><br />

of displacement (settlement) for a model<br />

fricti<strong>on</strong> pile in a frozen soil under a c<strong>on</strong>stant<br />

load at a c<strong>on</strong>stant temperature can be represented<br />

by the creep equati<strong>on</strong> in the form<br />

1168

,. .. ,.. ""<br />

_.."<br />

Similar symbols represent a test series as in Figure 3<br />

w<br />

LOAD = 2.20 kN 10.2 %<br />

0 0<br />

X<br />

I7<br />

K<br />

LOAD - 2.20 kN 2 6.1 ik<br />

0"<br />

+- -+""+--+<br />

0°C "-u<br />

y """""" -""<br />

4<br />

0<br />

-<br />

h<br />

2.20 kN 5 2.6 9:<br />

-Y<br />

I I I I<br />

0.1 0.3 3.0 10<br />

FREQUENCY, E (He)<br />

FIG. 5 DYNAMIC LOADING EFFECT ON DISPLACEMENT RATES (NORMALIZED) VERSUS FREQUENCY.<br />

1.7<br />

Slmllar symbols represent a test series as in Figure 3<br />

LOAD<br />

2.20 kN 5 5.1 %<br />

G 0 d<br />

2.25 kN<br />

+ 3.2 9:<br />

CI -<br />

LOAD 0<br />

9 2.20 kN +1.6 7.<br />

Y<br />

2.20 kN f 2.6 %<br />

Y<br />

\ I I I I I<br />

0.3 0.4 0.5 0.6 0.7, 0.8<br />

DISPLACEMENT RATE BEFORE DYNAMIC LOAD, 5 (m/Hr)<br />

2.27 kN<br />

+ 3.1 %<br />

9<br />

FIG. 6<br />

DISPIACEKENT RATE RATIO VERSUS DISPLACEMENT RATE BEFORE DYNAMXC (2) AND STATIC (+) LOADINGS.<br />

1169

6 - 6, F.1" e<br />

where b is a reference creep rate corresp<strong>on</strong>ding<br />

to h e proof load P , P is the pile load,<br />

t is time, and n a Cree& parameter, The model<br />

pile load can be readily c<strong>on</strong>verted to a shear<br />

stress by dividing by the pile surface area.<br />

Differentiati<strong>on</strong> of equati<strong>on</strong> (1) with respect to<br />

time gives the displacement (creep) rate b.<br />

For a small increase in load, with other variables<br />

c<strong>on</strong>stant, the ratio of displacement rates<br />

can be expressed in terms of the initial load<br />

Pi, the new load P,, and the creep parameter n,<br />

thus<br />

Equati<strong>on</strong> (2) may also be obtained from the<br />

relati<strong>on</strong>ship representing primary creep.<br />

Applying equati<strong>on</strong> (2) to the rates represented<br />

in Fig. 4, test XT, with b, = 0.540 mm/hr,<br />

62 = 0.092 mm/hr, P, = 2.20 kN, and Pa = 2.20<br />

t 0.065(2.20) = 2.34 IcN gives n = 8.13. Similar<br />

computati<strong>on</strong>s can be made for the other static<br />

load increase data points shown <strong>on</strong> Fig.-6 with<br />

good agreement and an average n close to 8.22.<br />

With frequency effects very small or negligible,<br />

and load change taken equal to the<br />

dynamic load amplitude, calculati<strong>on</strong>s with equati<strong>on</strong><br />

(2) using P, = (static load + dynamic<br />

load amplitude) , P, , 6, , and 6, as before, give<br />

an average value of n = 4.20 tor all dynamic<br />

loads. Examinati<strong>on</strong> of Fig. 6 shows a decrease<br />

in the displacement rate ratio (6, / 6,) with<br />

an increase in displacement rate immediately<br />

before dynamic loading. The slower 6, values<br />

corresp<strong>on</strong>d more closely to sec<strong>on</strong>dary creep.<br />

For the same loads (PI and P2), the creep<br />

parameter n changed, i-e., n appears to<br />

increase from about 3.1 to 5.5 as 6<br />

decreased. Available informati<strong>on</strong> indicates<br />

that n does not change for a static load<br />

increase applied to the model pile. The range<br />

in n values provides an estimate of the<br />

magnitude of the displacement rate changes for<br />

dynamic loading.<br />

ACKNOWLEDGMENTS<br />

The authors wish to express their appreciati<strong>on</strong><br />

to the Nati<strong>on</strong>al Science Foundati<strong>on</strong> for their<br />

support of this research project.<br />

REFERENCES<br />

Andersland, O.B., and Alwahhab, H.R.M. (1983)<br />

Lug behavior for model steel piles in frozen<br />

sand. PERMAFROST, Proceedings 4th<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, Nati<strong>on</strong>al Academy<br />

Pxess, Washingt<strong>on</strong>, D.C., p. 16-21.<br />

Ladan i, B. , and Guichaoua, A. 1985. Bearing<br />

capacrty and settlement of shaped piles in<br />

permafrost. Proceedings, 11th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

c<strong>on</strong>ference <strong>on</strong> Soil Mechanics and Foundati<strong>on</strong><br />

Engineering, A.A. Balkema, Bost<strong>on</strong>, Vol. 3,<br />

p. 1421-1427.<br />

Parameswaran, V.R. (1984) Effect of dynamic<br />

loads <strong>on</strong> piles in frozen soils. Proceedings,<br />

3rd <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Cold Regi<strong>on</strong>s Engineering<br />

Specialty <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, Canadian Society for<br />

Civil Engineering, M<strong>on</strong>treal, Canada, Vol. I,<br />

p. 41-52.<br />

Schmid, W.E. (1969) Driving resistance and<br />

bearing capacity of vibro-driven model piles.<br />

PERFORMANCE OF DEEP FOUNDATIONS, American<br />

society for Testing and Materials, Special<br />

Technical Publicati<strong>on</strong> 444, p. 362-375.<br />

Stelzer, David (in preparati<strong>on</strong>, 1988). Cyclic<br />

load effects <strong>on</strong> model pile behavior in frozen<br />

sand. Ph.D Dissertati<strong>on</strong>, Michigan State<br />

University, East Lansing, Michigan.<br />

Thomas, H.P., and Lusher, U. (1980)<br />

Improvement of bearing capacity of pipe piles<br />

by corrugati<strong>on</strong>s. collecti<strong>on</strong> of papers from a<br />

U.S. Soviet Joint Seminar, Leningrad, USSR.<br />

CONCLUSIONS<br />

1. A technique has been developed for measurement<br />

of displacement rate changes due to<br />

dynamic loads superimposed <strong>on</strong> statically<br />

loaded model piles. For small static load<br />

increases and n<strong>on</strong>res<strong>on</strong>ant cyclic loading<br />

this method appears to be suitable for<br />

determinati<strong>on</strong> of a creep parameter n.<br />

2. Model pile displacement rates in frozen<br />

sand were observed to be essentially<br />

independent of frequency for small dynamic<br />

loads superimposed <strong>on</strong> a large static load<br />

in the range of 0.1 Hz to 10 Hz.<br />

3. Cyclic loads significantly increased pile<br />

displacement rates over those observed for<br />

a sustained load. The magnitude of rate<br />

increase was shown to be dependent <strong>on</strong><br />

amplitude of the cyclic load.<br />

4. Creep theory appears to he suitalle for<br />

predicti<strong>on</strong> of the change in pile displacement<br />

rates due to a small cyclic load. The<br />

method does require use of loads and a<br />

reduced creep parameter n determined experimentally<br />

following procedures outlined in<br />

this paper.<br />

1170

TANGENTIAL FROST-HEAVING FORCE OF THE REINFORCED CONCRETE<br />

PILE AND CALCULATION OF PREVENTING IT FROM<br />

PULLING UP DUE TO FROST HEAVE<br />

Sun, Yuliang<br />

Water Resources Committee of S<strong>on</strong>ghua-Liao Basin, Ministry of Water Resources and Electric Power, P.R.C.<br />

measuring tinlo the electric resistance ratio<br />

and tho re3ultanl electric resistance ia<br />

aeasured, amordin;: to the difference of the two<br />

above values the taneential frost hoavhng force<br />

is derived.<br />

1171

In order to elirrlj.nnate the effect of s:,mthctic<br />

factors up<strong>on</strong> the dmamorletric sp.;tom, n<strong>on</strong>-stress<br />

metwo vem Inclu.dcd and. both the te;.:perature<br />

and the n<strong>on</strong>-stress meter corrocti<strong>on</strong> vert<br />

c<strong>on</strong>ducted to the xeasuring quantifjcz. Tho<br />

-renults of this two correcti<strong>on</strong>s arc cl<strong>on</strong>e,<br />

their differenpe is within 1.53 i.N, shorrn h<br />

lbes 1 and 2 Of Fig. 2.<br />

IOi<br />

Pig.2 .)recess Lines of Tangentin1 Frost<br />

IIanvin,- Polace, Frozen Depth and<br />

Underground Water<br />

l--':'otal frost heaving force with<br />

temperature corrocti<strong>on</strong> (iS1)<br />

2--Total frost heaving force rith<br />

n<strong>on</strong>-stress meter corrcctri<strong>on</strong> (U)<br />

3--UnIt tangential frost heaving<br />

pressure (2.m)<br />

4--Prozcn dopth (en)<br />

5--Undei3grol~nd mter level<br />

1172

~~ total<br />

T I<br />

I<br />

I<br />

"<br />

I<br />

I<br />

t<br />

I<br />

4-<br />

I<br />

t<br />

t<br />

""""<br />

40.1<br />

I<br />

""""<br />

*<br />

28.2 I<br />

i<br />

50.3 I<br />

, " 1<br />

I<br />

60.1 I<br />

. " i.<br />

41.8<br />

For the c<strong>on</strong>venience of corlparis<strong>on</strong>, the obtained<br />

data of tmngoitial frbst heaving force and the<br />

fricti<strong>on</strong>al reaiistance in the two fields in<br />

recent yeam are Listed in Table 2 for select<br />

Fn calculati<strong>on</strong>. There are 7 piles from<br />

Shmn,-liao , 9 frou G<strong>on</strong>gzuling, amounts to 16<br />

piles.<br />

In Table 2, the naximl total force of YhunSliao<br />

field occws at pile Eo. 3, the maxim1 mit<br />

forco st pile ITo. 4; fn G<strong>on</strong>gzuling, liouever,<br />

the aaxilml total force at pile Bo. 5, while<br />

the Laaximl unit force at pile No. 9. The<br />

and unit forcos do not occur at<br />

the same pile, Irhich is <strong>on</strong> account of the effeot<br />

of frozen de'th. Since the time vhen the<br />

mxinw occurs are different, the corresp<strong>on</strong>dhe<br />

frozen depth are ohmging also, as a romilt,<br />

value of unit force is influenced. In general<br />

cases, tho mxinux of tmgcntial frost heaving<br />

force often occurs in the early freaze-up atage<br />

(see line 7 of Fig. 2) Prou line 3 <strong>on</strong>e can<br />

see that the mrirnal unit force occurs in the<br />

early stago, the niniixn in the late staze.<br />

Bsnce, <strong>on</strong>e should not take the unit force at<br />

either of above tt:o stakps as criteria to<br />

deternine the form value. Yinoe in the early<br />

stage, the.tot;al force correzp<strong>on</strong>dinz to the unit<br />

force is not the ::aximm, and in tho late stage<br />

the unit force is the minimu, hovcver, tho<br />

deDi@ desired data is tho mximur.~ of the total<br />

force. In order to solve thin c<strong>on</strong>tradicti<strong>on</strong>,<br />

the reductive coefficient of the frozen depth<br />

is derived based <strong>on</strong> the frozen depth data<br />

corresp<strong>on</strong>ding to tho zaaxir& total Porcc.<br />

As menti<strong>on</strong>ed prcviou~ly tho time when tho<br />

maxi~d tanfpntial fcost heavin force occura is<br />

at the frozen depth Qf (0.5-0.77Ih, whore Ih--<br />

tho mxi&. frozen dcpth or 3-m standard frozen<br />

depth in local area. Let's tdce 0.71h m<br />

G 1 53.0 I 24.7 I 56.3<br />

1 - I<br />

I<br />

.+" """"-~""-"-+"""--<br />

I 7 i 69.5 I 52.2 i 46.0.<br />

i 7""""-p"""" i i *---"""<br />

t"""<br />

I I<br />

9 I 60.5 j ' 58.9 i t I<br />

_ "-<br />

I<br />

roeen depth, in the area of above fields the<br />

frozen depth after correcti<strong>on</strong> is Kz=l.O m.<br />

horn this, the aalculated unit forces in<br />

Shungliao and G<strong>on</strong>gzuling are 56.8 Ka and<br />

52.4 KPa, respectively. The desi,% value aan<br />

be tdcan aa p=G0 Ua.<br />

Fricti<strong>on</strong>al Resistant<br />

1-<br />

I<br />

I<br />

Force of Pile Foundati<strong>on</strong><br />

i "" -_l."""""""""""~".*-.-~~~~~~<br />

The in-situ observed data of limit fricti<strong>on</strong>al<br />

r<strong>on</strong>fstant l'orce of pile foundati<strong>on</strong> are few.<br />

In order to dctertlinc the force value range,<br />

Ire study the pulling-up resistant according to<br />

stability calculati<strong>on</strong> of piles and in-situ<br />

test data. Pox the poured pile, in the case<br />

of no top load, tho limit equilibrium of<br />

pulling-u resistance can be proved by the<br />

forr.lula: ,!an!;, I ~ 3 : )<br />

whom T--pulliing-up foroe, KLT,<br />

U--dinnoter of the pile, m,<br />

h,.--the depths of every surrounding soil<br />

." layo,-, rn,<br />

fi--the limit fricti<strong>on</strong>al resistant forcea<br />

ketxco:1 every surrounding soil Layer,<br />

1173

and the pile surt'ace, Ea,<br />

:/--the weight of pilo itfiolf, K T , for the<br />

underwater part, tzke float urei$it.<br />

For pile ITo.3 of Shungliao Siold vrre corquted<br />

the limit pulling-up frioti<strong>on</strong>al resistant force.<br />

The diovleter of pile No.3 is 0.45 n vith embedcd<br />

depth of 9 m. According to the teat data, from<br />

Jan, 13,1925, tho pile was pulJ.ed-up Lgr:~dmll;r,<br />

till Jan. 31 the tatal pulling-up mountod to<br />

6 m. On the basis of the two different frozen<br />

depths <strong>on</strong> Jan. 73 and Jan. 31, the aalculatetl<br />

rooults are ad follows: the frozen dopth <strong>on</strong> Jan.<br />

13 is 0.9 n, pullinpup foroe is 72 KN,<br />

fricti<strong>on</strong>al resistant form f =4.5IrPa; the frozen<br />

depth <strong>on</strong> Jan. 31 is 1 .f2 m, Julling-up force 1s<br />

79.71Q, fxicti<strong>on</strong>al force f =6.4 =a. In order<br />

to obeah tho p~llbg-up fhcti<strong>on</strong>al resistant<br />

force, the pull-out tests Were carried out at<br />

G<strong>on</strong>geuling field. The teated two piles axe<br />

iith diaMQt9r of 0.6 m and enbeded depth of 9 r.1.<br />

Jn order to exploit the nom1 frost heave foroe<br />

to yXLL-out the pilo, a reinforcod c<strong>on</strong>crate<br />

plate with Lameter of 1 m wos fixed <strong>on</strong>to the<br />

top of the pile. The lover surface of it was<br />

againat the ground, tharoforo, pile shaft was<br />

pulled-out by the norlllal fr<strong>on</strong>t heaving force.<br />

According to the measured pulling-out force,<br />

the calculated pulling-up frioti<strong>on</strong>d resistances<br />

me f =9.02 KPa, f =7.30 Ecpa, respeotively.<br />

C<strong>on</strong>paing the frich<strong>on</strong>d resistance f wi$h f2<br />

in Shu~n~liao fTeI.4, f < f . From tde<br />

dynmometric anu akfo&tdn measurement reouts<br />

<strong>on</strong>e can see that the pulling-up amount of pfie<br />

foundati<strong>on</strong> <strong>on</strong> Jan. 13 ~fns 3 m, did not reaoh<br />

ita limit, till Yan. 31 the pulling-up amount<br />

was 6 m, and the pulling-up force of the pile<br />

had already reached its limit, . Themfore, it<br />

is rati<strong>on</strong>al. to take the valuo of f , that is,<br />

the de8ign fricti<strong>on</strong>al resistant fogce is talcen<br />

m f =6 KPa. With the tangential frost<br />

heavhg foroe mnd the limit frictk<strong>on</strong>al.<br />

resbtanco, the pulling-up atability andysL.5<br />

of pile foundati<strong>on</strong> can be oarried out<br />

aacrding to the corresp<strong>on</strong>ding criteria.<br />

CaNcm IOHS<br />

The teat results of tangential frost heave force<br />

of shuangliao and G<strong>on</strong>gzuling can be applied to<br />

bore-poured reinforced o<strong>on</strong>crete piles whose<br />

em'ueded parts h frozen layer are required to<br />

be formwork poured. In order to avoid the<br />

effect of normal froot heaving, it is not<br />

allowed to c<strong>on</strong>struct crossgirders 19nkinng pile<br />

shafts in the frozen layers or <strong>on</strong> the ground<br />

surface. Tho reinforcement bars shodd<br />

strafch to the ~ O W W end of the pfie in order<br />

to mect the pulling-up atr<strong>on</strong>gth roquiromenfs.<br />

From the results, tre can dratr the c<strong>on</strong>cluoi<strong>on</strong>s<br />

as f ollotm :<br />

(1) Tho reinforced c<strong>on</strong>croto piles at<br />

Shuanglino and G<strong>on</strong>gzuling fields are<br />

formurar!: poured with.h tho frozen depth,<br />

hence tho values of tmzential frost<br />

heavhg force la dotemined when the<br />

pile surface is c<strong>on</strong>paritively smooth.<br />

As tho average fr<strong>on</strong>t howin; rate of tho<br />

local areas is 6.9-12.2'X; , tho design<br />

value of unit tagentin1 frost heavhng<br />

force is =60 lii'a, which am be refered<br />

to for pulh-q-up denign of pile<br />

1 t,74

BEHAVIOUR OF LONG PILES IN PERMAFROST<br />

A. Theriauft and B. Ladanyi<br />

Northern Engineering Centre, W e Polytecblaque, M<strong>on</strong>treal, Canada<br />

SYNOPSIS Loading axially a l<strong>on</strong>g pile in permafrost tesults in a transient redistributi<strong>on</strong> of<br />

stresses al<strong>on</strong>g its shaft due to time-dependent displacements characterizing frozen soil creep.<br />

Until now, finite element or finite difference methods had to be used for simulating the behaviour I<br />

of such piles. In this paper, an analytical soluti<strong>on</strong> for the $ame problem is presented and its<br />

predicti<strong>on</strong>s nre compared with some publiahad data obtained by a numerical calculati<strong>on</strong> method and<br />

by a direct observati<strong>on</strong> of model piles.<br />

&<br />

INTRODUCTION<br />

The piles used as foundati<strong>on</strong>s in permafrost<br />

soils are generally made of c<strong>on</strong>crete, wood or<br />

steel. While c<strong>on</strong>crete piles are usually c<strong>on</strong>sidered<br />

to be rigid with respect to the soil,<br />

pile compressibility has to be taken into<br />

account in the design of slender steel or<br />

timber piles.<br />

Pile compressibility produces a stress dfrtributi<strong>on</strong><br />

al<strong>on</strong>g the pile that varies with time and<br />

displacement. A numerical soluti<strong>on</strong> has been<br />

presented by Nix<strong>on</strong> and McRoberts(l976) for a<br />

pile embedded in frozen soil. For piles in<br />

unfrozen soils, analytical soluti<strong>on</strong>s, baaed <strong>on</strong><br />

the lateral shear modhlus c<strong>on</strong>cept, have been<br />

published by several authors (Cambefort, 1964;<br />

Coyle and Reese. 1966; Cassan, 1966;<br />

Murff,1975, 1980; Randolph and Wroth, 1978; Alpan,<br />

1978; Silvestri et a1.,1986; Murff and<br />

Shapery.l986), while, for piles embedded in an<br />

ideal elastic soil mass. numerical soluti<strong>on</strong>s have<br />

been obtained by Poulos and Davis(1968) and<br />

Mattes and Poulos(1969).<br />

In this paper, an attempt i s made to extend<br />

some of these soluti<strong>on</strong>s to piles in frozen<br />

soils. The proposed soluti<strong>on</strong> accounts fot creep<br />

properties of the soil surrounding a pile, in<br />

additi<strong>on</strong> to the pile-soil interface behaviour<br />

and pile properties normally c<strong>on</strong>sidered by<br />

soluti<strong>on</strong>s used for unfrozen soils. Similarly.<br />

the soluti<strong>on</strong> can account for slip al<strong>on</strong>g any porti<strong>on</strong><br />

of the pile-soil interface, which takes<br />

place after a certain shear displacement. As a<br />

result, the theory can evaluate change8 in pile<br />

stress and deformati<strong>on</strong>, as well as pile-soil<br />

interface shear stresses with time at any<br />

positi<strong>on</strong> al<strong>on</strong>g the pile.<br />

The results obtained by the proposed theory are<br />

then compared with those found earlier by the<br />

finite difference procedure (Nix<strong>on</strong> and McRoberts.1976)<br />

and those measured <strong>on</strong> model piles<br />

(Zhigul'skiy.1966).<br />

THEORY<br />

It is known that for slender piles in permafrost<br />

under service c<strong>on</strong>diti<strong>on</strong>a, <strong>on</strong>ly a very<br />

Small fracti<strong>on</strong> of the applied axial load is<br />

transfered to the pile base. The theory presented<br />

here neglects the base resistance; however.<br />

its effects can be taken into account easily.<br />

as shown by Theriault (1988).<br />

C<strong>on</strong>sider a cylindrical open ended pile embedded<br />

in permafrost (Fig.L), with radius t, embedded<br />

length D, and Young's modulus E. The equivalent<br />

axial modulus of the pile, can be<br />

calculated from<br />

EP *<br />

Ep = E Ap/rr2 - (1)<br />

where A i is the true area of the pile cross<br />

secti<strong>on</strong>. Vertical equilibrium of a secti<strong>on</strong> of<br />

the pile, dz, gives<br />

dP t 2tr~dz - 0 (2)<br />

where P is the axial load, T is the shear<br />

stress al<strong>on</strong>g dz, and z is the depth. Since the<br />

average axial stress in the pile, 0 , is<br />

related to P by<br />

dP = r2 do , <strong>on</strong>e gets (3)<br />

dddz + 2T/r = 0 (4)<br />

In additi<strong>on</strong>, c<strong>on</strong>sidering that the elastic shortening,<br />

dw,. of the length dz of the pile is<br />

given by<br />

Equati<strong>on</strong> (4) becomes<br />

dw, = -(o/Ep)dz (5)<br />

d2wz/dz2 - 2 r/rEp 0 (6)<br />

1175

IP<br />

O<br />

Figu're 2. True (n > 1) and assumed (n = 1) mobilizati<strong>on</strong><br />

of b<strong>on</strong>d strength t with shear displacement<br />

8 and time t, for a pile in permafrost.<br />

Equati<strong>on</strong> (8) can be written as<br />

Figure 1. Schematic variati<strong>on</strong> with time of pile<br />

settlement and the corresp<strong>on</strong>ding shear stresses<br />

al<strong>on</strong>g the shaft.<br />

This differential equati<strong>on</strong> can be integrated if<br />

the variati<strong>on</strong> of T al<strong>on</strong>g the pile shaft is specified.<br />

A usual assumpti<strong>on</strong> made in unfrozen<br />

soil mechanics, i s that f is a linear functi<strong>on</strong><br />

of the shear displacement at the so,il-pile<br />

interface, s, attaining a peak value, T - Tm x ,<br />

when a slip occurs at a given limiting dispfacement,<br />

sf. After the slip, T either remains<br />

c<strong>on</strong>stant, or falls to its residual value,<br />

If, instead of simple shear informati<strong>on</strong>. <strong>on</strong>e<br />

wants to use the results of triaxial.<br />

compressi<strong>on</strong> creep tests, then, assuming the validity<br />

of the v<strong>on</strong> Hises law, it can he shown<br />

(Ladanyl, 1972) that in the above equati<strong>on</strong>s<br />

should be replaced by<br />

TC<br />

with Tc50c, where b, and uc are creep parameters<br />

In the triaxial compressi<strong>on</strong> creep law<br />

In evaluating t , nost present theories limit<br />

themselves to the mobilizati<strong>on</strong> of b<strong>on</strong>d at the<br />

,pile-soil interface, neRlecting the deformati<strong>on</strong>s<br />

of the surrounding soil. I!owever, as shown<br />

by Johnst<strong>on</strong> and Ladanyi(l972) for piles in<br />

frozen soils, and hy Frank (1974) , and Randolph<br />

and t.'roth (1978) for piles i n unfrozen<br />

soils, this relati<strong>on</strong>ship can be established<br />

easily, using :he model of c<strong>on</strong>centric cylinders<br />

in simple shear.<br />

1:sing this model and assuming a power-law<br />

stress-strain rate relati<strong>on</strong>ship for frozen soil<br />

in simple shear<br />

-7 = - 7 y T y (7)<br />

where T,and TC are reference shear stress and<br />

shear strain rate, rcspcctivcly. Johnst<strong>on</strong> and<br />

Ladanyif1572) ohtained for a pile of radius r,<br />

and for no-slip c<strong>on</strong>diti<strong>on</strong>, the followinr: relati<strong>on</strong>ship<br />

hetween the settlement rate,<br />

4 = ds/dt and thc shear stress T al<strong>on</strong>r, the<br />

shaft<br />

where be and ue are the v<strong>on</strong> Mises equivalent<br />

strain rate and stress. Note that c<strong>on</strong>tains<br />

the effect of temperature and c<strong>on</strong>fining pressure,<br />

as shown by Ladanyi(l972). Sego and<br />

Morgenstern (1985) have shown the validity of<br />

Eq.(7) for ice-rich soil and polycrystalline<br />

ice.<br />

In additi<strong>on</strong>, if <strong>on</strong>e wants to use Eq.(lO) for<br />

also representing the primary creep, this can<br />

he d<strong>on</strong>e, under a time-hardening assumpti<strong>on</strong>. by<br />

replacing i n Eq.(lO) the time t by an<br />

appropriate time functi<strong>on</strong>, say btb, in which<br />

case E, in Eq.(ll) becomes (E,/b) , where h<br />

5 1. (Ladanyi.1975). Finally, Eq.(lO) can then<br />

he written in a fieneral form<br />

Equati<strong>on</strong> (13) shows that, for any Riven time<br />

t = c<strong>on</strong>st., T is a n<strong>on</strong>linear functi<strong>on</strong> of s. If<br />

there is no slip between the pile and the soil,<br />

s = wz, and substituti<strong>on</strong> of T from Eq.(13) into<br />

Eq.(6) gives<br />

Since, for I<strong>on</strong>:: tern, when crcep displacements where M is a time-dependent coefficient.<br />

RTC much larqcr than instnntaneous <strong>on</strong>es<br />

1176

the problem, similar to that used in unfrozen<br />

wo = (uo/E N) coth (ND)<br />

soils. had to be taken. In the latter, it is<br />

P<br />

usually assumed (Fig.2) that for wz < sf, the<br />

giving wz in terms of wo<br />

mobilized shear stress is linearly related to<br />

the shear displacement at the pile-soil wz = w [ cosh N(I) - z)<br />

interface, such wz < that, sf, for<br />

o cosh (ND)<br />

f 2:)<br />

(24)<br />

T = (s/sf) Tmax (15) A t the moment when slin starts at e = 0, wZ is<br />

given by Eq.(24), in which v0 =<br />

For s = sf, -r = Trnax, but for s > sf, T 5 -r Sf<br />

, eventually falling to ~ ~ ~ ~ i max d ~ ~ l ,<br />

when the adhesi<strong>on</strong> b<strong>on</strong>d is broken (Fig.Z), (see<br />

(2) Slip-everywhere soluti<strong>on</strong> (w, > sf)<br />

also Murff, 1980).<br />

As the other extreme, when slip has taken place<br />

Under these c<strong>on</strong>diti<strong>on</strong>s. Eq.(G) can he integrated,<br />

and several appropriate soluti<strong>on</strong>s are al<strong>on</strong>g the whole pile length, and T has dropped<br />

readily available in the literature. In order<br />

to its c<strong>on</strong>stant residual value, 'ere,, En.(17)<br />

to use these soluti<strong>on</strong>s for a pile in frozen becomes<br />

soil, the aging theory of creep can be applied,<br />

as d<strong>on</strong>e by Murff and Shapery(l986). In this<br />

particular case, this c<strong>on</strong>sists in expressing<br />

<strong>on</strong>ly Tmax in Eq.(15) as a functi<strong>on</strong>-of time and where ( Tres/lm) is the new shear reacti<strong>on</strong><br />

temperature, and in finding soluti<strong>on</strong>s for a modulus, c<strong>on</strong>stant al<strong>on</strong>g the pile, but deoendinc<br />

series of increasing time intervals. For any <strong>on</strong> time and temperature, because TreS usually<br />

given time, (t = ti > 0), and €or a given<br />

represents a fracti<strong>on</strong> of T ~ ~ ~ ,<br />

soil temperature, Eq.(13) gives the value of<br />

‘Crnax,i, corresp<strong>on</strong>ding to the critical (slip) Integrating Eq.(24) and respecting the boundary<br />

displacement. s = sF:<br />

c<strong>on</strong>diti<strong>on</strong>s that at z = 0, wz = wo an$ dwz/dz =<br />

- Uo/Ep, yields<br />

Since, for s < sf, s = wz, substituting<br />

Eq.(15) into Eq.(6), the latter becomes<br />

In fact, Eq.(26) is valid <strong>on</strong>ly when the displacement<br />

at the pile base has also attained the<br />

critical value, i.e., WD = s at z = D. Jr.<br />

that instant, the settlement of the pile head<br />

will he<br />

In Eq.(18), ( sf) represents a shear<br />

reacti<strong>on</strong> modulus, which is a functi<strong>on</strong> of time Note that, under field c<strong>on</strong>diti<strong>on</strong>s, T~~~ uill<br />

and temperature. The well known soluti<strong>on</strong> of tend with time to a finite value, affecte by<br />

Eq.(17) is<br />

gravity stresses and Senerally increasing \:ith<br />

depth. A soluti<strong>on</strong> for such c<strong>on</strong>diti<strong>on</strong>s in unfro-<br />

Wz = C1 exp(h’z) + C2 exp(-Nz) (19) zen soil was obtained by Silvestri et al.<br />

(19RG)<br />

and from Eq.(5), the axial stress in the pile<br />

is<br />

(3) Partial-slip soluti<strong>on</strong> (vo 2 sf)<br />

In that case. it is assumed that slip has<br />

where C1 and C2 are integrati<strong>on</strong> c<strong>on</strong>stants to occurred tloun to the depth z = 9f (FiF.l),<br />

be determined from the houndnry c<strong>on</strong>diti<strong>on</strong>s. The<br />

while there is no slip al<strong>on</strong>g the rest of the<br />

particular soluti<strong>on</strong>s have the following form.<br />

pile lenath, (n - Il ). The boundary c<strong>on</strong>diti<strong>on</strong>s<br />

for Eqs.(l9) and (26) are then: wz = sf at z =<br />

Df, and dw,/dz = 0 at z = n. This gives for the<br />

(I) No slip soluti<strong>on</strong> (wo < sc)<br />

If it is assumed that there is no slip hetween<br />

the pile and the soil, Rqs.(l) and (20) Can hr<br />

solved by intr ducing the houndary c<strong>on</strong>diti<strong>on</strong>s<br />

(Jz = Uo = P,/nrY at z = 0, and oz = 0 nt z = D.<br />

This yields (e.g., Farmer, 1075)<br />

cosh N(D - z)<br />

“2 = (‘o/EpN)[ sinh (ND) 1 (21)<br />

u =<br />

sinh N(D - z)<br />

z ‘0 [ sinh (ND) 1<br />

porti<strong>on</strong> of the pile belov the z<strong>on</strong>e of slip (I),<br />

< z 4 I),<br />

1177

Pile Displacement, IOm4m<br />

0 2 4 6 8 1 0 0 2 4 6 8 1 0 0 2 4 6 8 1 0<br />

0<br />

1<br />

2<br />

€3<br />

G4<br />

E<br />

5<br />

6<br />

0.3 days<br />

0 0 1 2 3 4 5<br />

1 1 - 1 I 1<br />

0<br />

3<br />

t+<br />

- 1 day<br />

-<br />

Shear Stress, lo2 kPa<br />

0 1 2 3 4 5 0 1 2 3 4 5<br />

1 I I IO'<br />

5<br />

6<br />

0.3 days<br />

II.<br />

-<br />

-<br />

1 day<br />

Nix<strong>on</strong> & McRoberts(1976)<br />

0 0 0 oCalculated, this paper<br />

Figure 3. Dl. splacements and shear stresses for a 6.1 m l<strong>on</strong>g timber pile<br />

in permafrost, obtained by.the finite difference method (Nix<strong>on</strong><br />

and McRoberts. 1976), and by the proposed analytical soluti<strong>on</strong>.<br />

0 - (2 -rres Df)/r -+<br />

= 0 (31)<br />

+ exp N(2D-Df) 1<br />

Once Df is known, the values of wz and uz at<br />

any depth al<strong>on</strong>g the pile can be determined for<br />

any given values of the applied load and time.<br />

Value of sf<br />

Similarly as for piles in unfrozen soils, the<br />

value of critical slip displacement, sf, for<br />

piles in frozen soils depends <strong>on</strong> the shape and<br />

roughness of the pile shaft, and <strong>on</strong> the method<br />

of pile installati<strong>on</strong>. For very rough cast-inplace<br />

piles in a frozen varved soil, Johnst<strong>on</strong><br />

and Ladanyi(l972) found sf t o be of the order<br />

of 20 to 30 rnm. These values are not much<br />

different from those found €or piles in unfrozen<br />

soils (VesiE, 1976). For driven piles, sf<br />

value may be also a functi<strong>on</strong> of the pile diameter.<br />

On the other hand, in small scale shear<br />

box tests wjth frozen sand against smooth<br />

metallic surfaces, ThEriault(l988) has found<br />

for sf a value of about 0.4 mm.<br />

Settlements<br />

CALCULATION PROCEDURE<br />

For predicting the time-dependent settlement of<br />

a compressible pile. embedded in frozen soil<br />

and loaded by a c<strong>on</strong>stant load, Po, the<br />

following procedure is suggested:<br />

(a) For a given time, t = ti > 0, and for known<br />

values of Ep and sf, determine T ~ from ~<br />

Eq.(16), and N = Ki from Eq.(18).<br />

(b) Determine Df from Eq.(31).<br />

(c) If Df 4 0, calculate wo from Eq.(23), by<br />

takins increaaing time intervals, until wo =<br />

Sf *<br />

(d) If IIf > 0. calculate w from Fq.(2P) by<br />

substituting Df for D. P.s 8, increases and<br />

T~~~ decreases with time, w will also<br />

increase until it attains its Pinal finite<br />

value given by Fq.(28). From that instant <strong>on</strong>,<br />

<strong>on</strong>ly settlement rate can be determined, if<br />

= f(6) is known.<br />

Clearly, as menti<strong>on</strong>ed, for pile secti<strong>on</strong>s located<br />

between Df < z 6 D, the time settlement is<br />

~ i v e n by iq.(29).<br />

1178

Shear Stress after 1 hour, Id kPa<br />

0 1 2 3 4 0 1 2 3 4 0 1 2 3 4 5<br />

I<br />

l ' c<br />

tf<br />

1.0<br />

Po = 39.2 kN<br />

1.2<br />

Shear Stress after l20 hours, lo2 kPa<br />

0 1 2 3 4 0 1 2 3 4 0 1 2 43 54 5<br />

to<br />

1.2p<br />

I+<br />

Po = 39.2 kN<br />

T 1<br />

78.5 kN<br />

Measured (Zkgul'skiy, 1966)<br />

Calculated, this paper<br />

Figure 4. Short- and l<strong>on</strong>g-term ahear stresses al<strong>on</strong>g the shaft of a<br />

1.20 m l<strong>on</strong>g model tubular pile, obtained by direct measurements<br />

(Zhigul'skiy, 1966), and calculated by the proposed<br />

analytical soluti<strong>on</strong>.<br />

A program in BASIC is availahle for these calculati<strong>on</strong>s.<br />

Axial stresses in the pile<br />

(a) Before slip<br />

(D < Df): use Eq.(22).<br />

(b) For partial slip (0 < Df < D): use F,q.(30).<br />

COMPARISON WITH PUBLISHED DATA<br />

As no complete case histories <strong>on</strong> the field $e-<br />

(c) For complete slip (Df = D): use Eq.(27).<br />

haviour of comoressible piles in permafrost have<br />

been published to date, the predicti<strong>on</strong>s by<br />

Clearly, because !: = €(time). there is a c<strong>on</strong>- the proposed theory have been compared with two<br />

tinuous axial stress redistrihuti<strong>on</strong> for any published studies: <strong>on</strong>e involving a numerical sogiven<br />

Po value,<br />

luti<strong>on</strong> (Nix<strong>on</strong> and McRoberts. 1976). and another<br />

<strong>on</strong>e resenti in^ the results of observati<strong>on</strong>s <strong>on</strong><br />

modei piles (Ziigul'skiy, 1966).<br />

Tangential stresses al<strong>on</strong>g the pile<br />

Nix<strong>on</strong> and McRoberts (1976) have used the finite<br />

In the regi<strong>on</strong> where w < sf, <strong>on</strong>e gets from<br />

difference procedure to simulate the behaviour<br />

Eq.(15):<br />

of a compressible pile embedded in an ice-rich<br />

soil or ice. As no slip was allowed at the<br />

T = wz' Tmax'sf) (32)<br />

pile-soil interface, they used the Johnst<strong>on</strong> and<br />

enabling to calculate 'I : Ladanyi (1972) theory for taking into account<br />

the soil creep, as in this paper. They also<br />

(a) Refore slip (n < Uf), from Eq.(21). assumed a zero point resistance. The pile characteristics<br />

were: D = 6.1 m, r = 0.1525 m, E<br />

(b) For partial slip (0 < Df < TI). from = 8.3 GPa (timber pile), and the pile wag<br />

Eq.(29)." loaded by Po = 188 kN. The ice-rich soil at a<br />

temperature of -2OC, was characterized by: b =<br />

(c) For complete slip (Df = D), T = 'res.<br />

1179

Figure 3 shows a comparis<strong>on</strong> between the finite<br />

difference soluti<strong>on</strong> (full linea) and the proposed<br />

analytical soluti<strong>on</strong> (points) for three<br />

different times after load applicati<strong>on</strong>. A<br />

reas<strong>on</strong>ably good agreement can be seen in both<br />

the displacements and the shear stresses al<strong>on</strong>g<br />

the shaft.<br />

A sec<strong>on</strong>d comparis<strong>on</strong> is based <strong>on</strong> the test<br />

r e s u l t s <strong>on</strong> model piles, published by<br />

Zhigul'skiy(l966). His tests were made <strong>on</strong><br />

tubular open-ended aluminium piles embedded in<br />

frozen sand. The pile characteristics were: D =<br />

1.20 m, r - 0.103 m (wall thickness 3 mm). A 3<br />

no properties of the frozen sand used in the<br />

tests have been reported by the author, some<br />

typical values of parameters, found by<br />

Theriault(l984) for a similar frozen fine sand<br />

("Joliette Sand"), have been used in the<br />

calculati<strong>on</strong>. For the test temperature of -<br />

3.2OC, these are: b = 0.67, n = 4.0, and Uc =<br />

1390 kPa at ic = min-l. As before, it kraa<br />

assumed that sf = 0.4 mm.<br />

Figure 4 shows the results of the comparis<strong>on</strong><br />

for both short-term (t - 1 hour) hnd l<strong>on</strong>g-term<br />

(t - 120 hours) tests, and for the applied<br />

loads of 39.2, 78.5, and 118 kN, respectively.<br />

The agreement between the observati<strong>on</strong>s (full<br />

lines) and the predicti<strong>on</strong>s (points) is Been to<br />

be quite reas<strong>on</strong>able, keeping in mind that the<br />

properties of frozen sand used in the tests,<br />

and the value of sf had to be taken from other<br />

sources. ,<br />

CONCLUSION<br />

A complete analytical soluti<strong>on</strong> for an axially<br />

loaded compressible pile, embedded in frozen<br />

soil is presented. The soluti<strong>on</strong> accounts for.<br />

creep properties of the soil, in additi<strong>on</strong> to<br />

the usual pile-soil interface bchaviour. including<br />

slip. Comparis<strong>on</strong> between stresses and<br />

displacements predicted by the proposed<br />

soluti<strong>on</strong>, and those obtained earlier hy a numerical<br />

procehure and by a direct observati<strong>on</strong><br />

<strong>on</strong> model piles, respectively, shows a satisfactory<br />

agreement. It is noted that all necessary<br />

calculati<strong>on</strong>s can be made <strong>on</strong> a PC, using BASIC,<br />

or can be programmed for a pocket calculator.<br />

ACKNOWLEDGEMENT<br />

Vol.17,. no'.204, pi1462.<br />

Cassan, X. (1966). Le tassement des pieux:<br />

synthese des recherches rgcentes et essais<br />

comparatifs. Sols-Soils, 1.!0.18-19, pp.43-<br />

52.<br />

Coyle. I{.!,!. Bnd Reese, L.C. (1966). Load<br />

Transfer for Axially Loaded Piles in Clay.<br />

J.of Soil !lech.& Found.Div.,ASCE, Va1.92,<br />

F:o.s112, pp.1-26.<br />

Farmer. I.K. (1975). Stress Distributi<strong>on</strong> al<strong>on</strong>g<br />

a Resin Grouted Rock Anchor. Int.J.of Rock<br />

I4ech.E Mining Sci., Vo1.12. Ko.11. pp.347-<br />

351.<br />

Johnst<strong>on</strong>, G.I!. and Ladanyi, B. (1972). Field<br />

Tests of Grouted rod Anchors in <strong>Permafrost</strong>.<br />

Canad.Geotech.J., Vo1.9, pp.176-194.<br />

Ladanyi, B. (1972). An Engineering Theory of<br />

Creep of Frozen Soils. Canad.Ceotech..J..<br />

V01.9, pp.63-80.<br />

Ladanyi, B. (1975). Eearing Capacity of Strip<br />

Footings in Frozen Soils. Canad.Ge0tech.J..<br />

V01.12, pp.393-407.<br />

Mattes, X.S. and Poulos, R.G.(l969). Settlement<br />

of Single Compressible Pile. J.of Soil<br />

Kech.& Found.Civ.,ASCE, Vo1.95, Sy!l,<br />

pp.189-207.<br />

Murff, J.D. (1975). Resp<strong>on</strong>se of Axially !,oaded<br />

Piles. J.of Geotech.Engrg.Div.ASCC,<br />

V01.101, GT3, pp.356-360.<br />

Murff, J.D. (1980). Pile Capacit!' in a<br />

Softening Soil. 1nt.J. of Kumer.!:<br />

Analyt.l,leth. in Geomech., Vol.h, pp.185-139.<br />

blurff, J.D. and Schapery, R.A.(1986). Time<br />

Dependence of Axial Pile Resp<strong>on</strong>se. 1nt.S.of<br />

Numer.& Analyt.>leth. in Geomech., Vol.10,<br />

pp. 449-458.<br />

Nix<strong>on</strong>, J.F. and FlcRobcrts, E.C.(1976). A Design<br />

Approach for Pile Foundati<strong>on</strong>s in <strong>Permafrost</strong>.<br />

Canad.Geotech.3.. Vol.l3. pp. 40-57.<br />

Poulo8, B.G. and Davis, E.H.(1968). The Settlement<br />

nehaviour of Single Axially Loaded<br />

Incompressible Piles and Piers.Geotcchnique,<br />

le,pp.351-371.<br />

Randolph, V.F. and \t!roth, C.P.(1976). Analysis<br />

of Deformati<strong>on</strong> of Vertically Loaded Piles.<br />

J.of Ceotcch.Engrp.Div.ASCF, Yo1.104,<br />

GT12, pp.14S5-1488.<br />

Sego, D.C. and Korgenstern. .R.(1985). Punch<br />

Indentati<strong>on</strong> of Polycrystalline Ice.<br />

Canad.Geotech.J., Vo1.22, pp.226-233.<br />

Silvestri, V., Chapuis, R.P. and Souli6, Pi.<br />

(1966). Predicti<strong>on</strong> of Axial Capacity of<br />

L<strong>on</strong>g Piles in So.ft Cohesive Soils.<br />

Proc.3rd Int. C<strong>on</strong>f.<strong>on</strong> Numer.I.iethods in<br />

Offshore Piling, Nantes, France, pp. 191-<br />

200.<br />

ThBriault(Guichaoua). A. (1984). CapacitE<br />

portante des pieux tr<strong>on</strong>c<strong>on</strong>iqucs et<br />

crenelCs. ):&moire !.I.Sc..\.. Pcole<br />

This work was financially supported by the<br />

grants A-1801 and G-1566 (R. Ladanyi) of the<br />

Nati<strong>on</strong>al Science and Engineering <strong>Research</strong> Polytechnique, Il<strong>on</strong>tr6al. lllp.<br />

Council of Canada. ThBriault. A. (1988). Capncite p<br />

pieux dans' le .perge'lisol. 'ThEse Ph..,<br />

REPEREF!!CES<br />

Ecole Polytcchniquc, X<strong>on</strong>treal,<br />

PesiE, A.S. (1977). Design<br />

350~.<br />

of Pilc<br />

Transp.Res.Coard ;i<strong>on</strong>ograph. !;.C,I'ashingt<strong>on</strong>.<br />

Alpan, I. (1978). Dae Last-Setzungverhalten des<br />

68p.<br />

Einzelpfahles (Load-Settlement I3ehaviour Zhip,ul'sl:iy, A.A. (1966). Experi rental Investiof<br />

a Single Pile). nauingenieur, Vo1.53, gati<strong>on</strong> of the State of Stress and Strain<br />

pp.293-298. in Soil around thc R Pilc. T'r<br />

C<strong>on</strong>f.<strong>on</strong> Geocryology, Yakutsk. L'SSR, Part<br />

5, pp.211-223. (In Russian).<br />

1180

INVESTIGATION ON TANGENTIAL FROST HEAVING FORCES<br />

T<strong>on</strong>g, Changjiangl, Yu, Ch<strong>on</strong>gyunr, and Sun, Weimin2<br />

1Lanzhou Institute of Glaciology and Geocryology, Academia Sinica, China<br />

zlnstitute of Daqing Oilfield C<strong>on</strong>structi<strong>on</strong> Design and <strong>Research</strong><br />

SYNOPSIS The tangential frost heaving force acting od the lateral surface of foundati<strong>on</strong>s<br />

depends up<strong>on</strong> the compositi<strong>on</strong> and moisture c<strong>on</strong>diti<strong>on</strong> of -the soil, freezing rate and foundati<strong>on</strong> material.<br />

Test results show that silty soil and loam may create the maximum tangential frost heaving<br />

force. The tangential frost heaving force increases with increasing moisture c<strong>on</strong>tent, negative temperature<br />

and freezing rate of soils and the roughness of the surface of foundati<strong>on</strong>s. The tangential<br />

force also increases with the rise of the groundwater table. The tangential force varies with the<br />

foundati<strong>on</strong> material. It has a maximum value for c<strong>on</strong>crete piles and lower values for steel and wood<br />

piles. Test results also show that the tangential frost heaving force does not depend up<strong>on</strong> the diameter<br />

of piles. The design values of tangential frost heaving forces, which were determined based<br />

<strong>on</strong> the susceptibility of soils, are also given in this paper.<br />

INTRODUCTION<br />

In the last 50 to 60 years, extensive researches<br />

<strong>on</strong> tangential frost heaving forces acting up<strong>on</strong><br />

lateral surfaces of foundati<strong>on</strong> piles in the<br />

freezing process have been c<strong>on</strong>ducted by many<br />

investigators. Since 1965, the authors have ,<br />

carried out a lot of experiments <strong>on</strong> this subject<br />

both in the laboratory and at field stati<strong>on</strong>s.In<br />

additi<strong>on</strong>, plenty of data <strong>on</strong> frost heaving forces<br />

were obtained by the Wangjia Field Test Stati<strong>on</strong><br />

of Heil<strong>on</strong>gjiang Provincial Institute of Water<br />

C<strong>on</strong>servancy, the Qingan Field Test Stati<strong>on</strong> of<br />

Heil<strong>on</strong>gjiang Provincial Institute of Traffic<br />

Science and the Yanjiag<strong>on</strong>g Field Observati<strong>on</strong><br />

Stati<strong>on</strong> of Heil<strong>on</strong>gjiang Provincial Institute of<br />

Low-Temperature C<strong>on</strong>structi<strong>on</strong> Science. Some<br />

achievements have been made in the study <strong>on</strong> the<br />

formati<strong>on</strong> and development of the tangential frost<br />

heaving force and its influencing factors.Design<br />

values o f tangential frost'heaving stresses have<br />

been proposed, Further research, however, is<br />

still needed for better, understanding of the<br />

mechanism of formati<strong>on</strong> of theforce and the interacti<strong>on</strong><br />

between foundati<strong>on</strong>s and frozen ground,as<br />

well as stress distributi<strong>on</strong> in frozen ground.<br />

This paper discusses some of the test results<br />

obtained by the authors and other investigators.<br />

the 2/3 of the maximum penetrati<strong>on</strong> depth, as is<br />

shown in Fig.1 (T<strong>on</strong>g and Guan, 1985a). The variati<strong>on</strong><br />

of tangential frost heaving stress at<br />

different depths is closely relaeed to soil<br />

moisture, temperature and the vo.lume of moisture<br />

migrati<strong>on</strong>. During the whole process of freezing,<br />

each layer of soil experiences four stacges:<br />

initial freezing, active freezing, cooling and<br />

super-cooling. Tangential frost heaving pressure<br />

increases chiefly in the 1st and 2nd stapes, and<br />

decreases in the 3rd and*hth stages.<br />

Influence of Soil Characteristics <strong>on</strong> TanRential<br />

Frost HeavinR Stress<br />

Under siftrilar thermal and moisture c<strong>on</strong>diti<strong>on</strong>s,<br />

a decrease in grain size leads to an increase in<br />

tangential frost heaving stress. The magnitudes<br />

of the stress for various types of soil are in<br />

the order of: silty loam>loam>clay gravel>medium<br />

sand>coarse sand (Fig.2). The value of the<br />

stress for saturated coarse sand with 98% grains<br />

larger than 0.1 mm is 95% less than that for<br />

the saturated sandy loam. If the c<strong>on</strong>tent of the<br />

grains smaller than 0.1 mm is over 30-50% in<br />

sand and gravel, the value of the stress for the<br />

soil is about 50% greater than that for the pure<br />

sand and gravel.<br />

DISCUSSION<br />

Distributi<strong>on</strong> u f Tangential Frost Heaving Stress<br />

<strong>on</strong> Lateral Surface o f a Pile<br />

The experimental results show that the distributi<strong>on</strong><br />

of tangential frost heaving stress <strong>on</strong> the<br />

lateral surface of a pile is extremely n<strong>on</strong>uniform<br />

during the process of freezing. The<br />

peak value of the stress moves down with the<br />

penetrati<strong>on</strong> of the frost fr<strong>on</strong>t and reaches its<br />

maximum value when the frost fr<strong>on</strong>t drops down to<br />

Influence of Soil Moisture <strong>on</strong> Tangential Frost<br />

Weaving Forces<br />

The experimental evidence shows that in a closed<br />

system, the tangential frost heaving stress fur<br />

clayey soi.ls increases with an increase in water<br />

c<strong>on</strong>tent as the water cmtent is greater than the<br />

plastic limit, and finally reaches the value of<br />

the tangential stress for ice, as is shown in<br />

Fig.3.<br />

For water c<strong>on</strong>tents ranging from Wp to Wp+l7,the<br />

1181

0 10 20 0 10 20 0 10 20 (r 10 20<br />

0<br />

c<br />

e<br />

150,<br />

Pig.1 Variati<strong>on</strong> of Tangential Frost<br />

Heaving Pressure at Different Depth<br />

with Time:<br />

(a) Oct.25, (b) Nov.10, (c) Hov.25,<br />

(d) Dec.10, (e) Dec.20.<br />

Range of temperature:<br />

1. 0" -0.5'C, 2. -0.5" -5"C,<br />

3, -5" -1O"c, 4. -10°C.<br />

increase in the t-angential frost heaving stress<br />

(UT) with water c<strong>on</strong>tent can be approximately<br />

formulated as the following:<br />

= a (w - wp) (1)<br />

where a is an empirical coefficient and Wp is<br />

the plastic limit of the soil.<br />

When the water c<strong>on</strong>tent is between Wp+17 and wpt<br />

60, the tangential frost heaving stress decreases<br />

with the increase in water c<strong>on</strong>tent and<br />

finally closes the value of the tangential<br />

stress for ice (about 200 kPa) after W is greater<br />

than Wpt60.<br />

Influence of Soil Temperature <strong>on</strong> Tangential<br />

Frost Heaving Stress<br />

Fig.2 Comparasi<strong>on</strong> of the Tangential<br />

Heaving Pressure Am<strong>on</strong>g Different<br />

types of Soil:<br />

1--loam, 2--silty loam, 3--clay,<br />

4--gravel, 5--medium sand,<br />

6--coarse sand.<br />

It has been shown experimentally that the tangential<br />

frost heaving stress increases as soil<br />

temperature drops (Fig.4). As the temperature<br />

drops from freezing point to -5'C, the stress<br />

sharply increases and reaches about 60-70% of<br />

its maximum value. In the range of temperature<br />

from -5OC to -1O'C, the increase in the stress<br />

with decreasing temperature slows down and,with<br />

the temperature below -lO°C, the stress tends to<br />

be c<strong>on</strong>stant. The tangential frost heaving stress<br />

as a €uncti<strong>on</strong> of temperature for cohesive soils<br />

can be expressed by<br />

oT = alglb (2)<br />

where e is the soil temperature in degrees<br />

Celsius below zero, a and b are empirical parameters.<br />

In additi<strong>on</strong>, the frost penetrati<strong>on</strong> rate has a<br />

str<strong>on</strong>g influence <strong>on</strong> the tangential frost heaving<br />

stress, The statistical analysis <strong>on</strong> experimental<br />

data shows that the slower the frost fr<strong>on</strong>t moves,<br />

o Lab<br />

Field<br />

Water c<strong>on</strong>tent W (*.I<br />

Fig.3 Tangential Frost Heaving Stress<br />

vs Water C<strong>on</strong>tent<br />

1182

the less the tangential lrost heaving pressure<br />

increases (Fig.5). A t a frost penetrati<strong>on</strong> rate<br />

(Vf) ranging from 0.9 to 1.0 mm/hr., the growth<br />

rate of tangential frost heaving stress<br />

(

<strong>on</strong> Qinghai- Xizang Plateau, Academia Press,<br />

China.<br />

m<br />

Fig.6 Tangential Frost Heaving Stress<br />

C<strong>on</strong>crete Piles Coated with Different<br />

Kinds of Oils vs.Temperature<br />

%uncoated ocoated with residuum<br />

ocoated with vaseline<br />

<strong>on</strong><br />

explorati<strong>on</strong> and evaluati<strong>on</strong>, the authors identified<br />

the texture and physico-mechanical parameters<br />

of frozen soils with frost heaving and<br />

classified the frost susceptibility of soils<br />

as the following: negligible, low, medium, high<br />

and very high, for which the corresp<strong>on</strong>ding Erost<br />

heaving ratios are: 12% respectively. Since the values in Table<br />

11 are given based <strong>on</strong> a comprehensive c<strong>on</strong>siderattan..<br />

of frost heaving <strong>on</strong> precast c<strong>on</strong>crete piles<br />

at temperatures below -10°C under natural frost<br />

c<strong>on</strong>diti<strong>on</strong>s, the amendments can be made according<br />

to the average temperature of the ground from<br />

the surface to 2/3 of the maximum frost penetrati<strong>on</strong><br />

depth and the pile material and surface<br />

c<strong>on</strong>diti<strong>on</strong> (Table I11 and IV) (T<strong>on</strong>g., 1985~).<br />

ACKNOWLEDGEMENTS<br />

The authors gratefully thank the co-workers of<br />

Heil<strong>on</strong>gjiang Provincial Institute of Water<br />

C<strong>on</strong>servancy and Heil<strong>on</strong>gjiang Provincial Institute<br />

of Low-Temperature C<strong>on</strong>structi<strong>on</strong> Science and<br />

Institute of Daqing Oilfield C<strong>on</strong>structi<strong>on</strong> Design<br />

and <strong>Research</strong> for their c<strong>on</strong>tributi<strong>on</strong> of a great<br />

deal of experimental data. The assistance received<br />

from Mr..Huang He and Prof. Zhu Yuanlin<br />

is sincerely appreciated.<br />

REFERENCES<br />

Changjiang T<strong>on</strong>g and F<strong>on</strong>gnian Guan, (1985a),<br />

Frost heaving and preventi<strong>on</strong> of frost<br />

damages to c<strong>on</strong>structi<strong>on</strong>s. China Water<br />

C<strong>on</strong>servancy and Power Press.<br />

Changjiang T<strong>on</strong>y, Yaqing Wang and Jingshou Li.u,<br />

(1985b), Effect of antiheaving coating <strong>on</strong><br />

frost heaving. Collected Papers <strong>on</strong> <strong>Permafrost</strong>.<br />

Studies un Qinghai-Xizang Plateau,<br />

Academia Press, China.<br />

Changjiang T<strong>on</strong>g, (1985c), Tangential frost<br />

heaving f0rc.e of soils and their classificati<strong>on</strong>.<br />

Collected Papers <strong>on</strong> <strong>Permafrost</strong> Studies<br />

1184

TABLE I1<br />

Design Values of Tangential Frost Heaving Stress<br />

Frost susceptibility classificati<strong>on</strong> N<strong>on</strong> Weak Med i unt<br />

Str<strong>on</strong>g stro<br />

VerX g<br />

Frost heaving ratio (X) 12<br />

Texture of frozen soils massive mini-layered layered specked based<br />

mini-reticulate<br />

clayey w

STRESS-STRAIN BEHAVIOUR OF FROZEN SOILS<br />

S.S. Vyalovl, R.V. Maximyakz, V.N. Razbeginz, M.E. Slepak2 and A.A. Chapayevz<br />

1Moscow Civil Engineering Institute, Moscow, USSR<br />

2Gersevanov <strong>Research</strong> Institute of Bases and Underground<br />

Structum, MOSCOW, USSR<br />

ABSTRBCT In practice, predicting the stress-strain behavioux of frozen soil loaded by a<br />

locally distributed presaure is the most usual problem of engtneerbg geocrgology. Xn this paper<br />

some experimental results are given, whFch have been obtained recently from both microscopic nnd<br />

macroScopic investigati<strong>on</strong>s of frozen soil deformati<strong>on</strong> and failure under a rigid plate as well as<br />

from uniaxial compressi<strong>on</strong> tests. A mathematical model is proposed and discussed to describe the<br />

basia peculiarities of frozen soil mechanical bebartour. An analytical soluti<strong>on</strong> of plane strain<br />

problem has been found using simplified modificati<strong>on</strong> of nodel proposed. This modificati<strong>on</strong> can<br />

also be regarded &s the partial variane of strain-hardening theory. Calculati<strong>on</strong> results are<br />

given which oompare well-with experimental data.<br />

INTRODUCTION<br />

Up to preeent, o w a few work^ are horn dealing<br />

with M erperlmeatal study of plate pmblem<br />

in frozen soils (Berezantchev, 1947, Vy&<br />

lov, 1959, Marimyak, 1985). Physical peculiarities<br />

of soil behavlour under a loaded rigid<br />

plate were firstly investigated by S.S.Vyalov<br />

(19.59), who described a set of interdependent<br />

physicod.uecharrlca1 prooessea associated with<br />

plate indentati<strong>on</strong>, am<strong>on</strong>g them local phase<br />

transiti<strong>on</strong>s, unfrozen water migrati<strong>on</strong>, cracks<br />

nucleati<strong>on</strong> and other <strong>on</strong>es. This paper develope<br />

earlier jsoestigati<strong>on</strong>s to acueve a better<br />

understandhg of various structure deterioratfng<br />

processes c<strong>on</strong>parative role unaer various<br />

loading c<strong>on</strong>diti<strong>on</strong>e. A mathematical model of<br />

new type is px'oposed to describe the basta of<br />

revealed peculiaritkes, including microcracking<br />

influence aad elastoviscoplastic effects<br />

at the variable loading regimes.<br />

TESTING MEPHODS' BND RESKiXS<br />

Experiments were carried out with a' disturbed<br />

clay of fired density and water c<strong>on</strong>tent, c<strong>on</strong>fined<br />

into the ateel shoot of 1oOr30~1~0 m.<br />

Soil waa freezing at the fired temperature<br />

during about I00 hours. After that, a c<strong>on</strong>stant<br />

load was applied through a rigid rectangular<br />

steel plate 100x30 am and 3 mm thicbess. had<br />

values were choosd over a range 1.3-13'm.<br />

Corresp<strong>on</strong>ding test c<strong>on</strong>tinuties were from seve- -<br />

xal days to several sec<strong>on</strong>ds. Quasi-instant<br />

strength value (3.75 "a) had been previously<br />

determined In uniaxial cornpressi<strong>on</strong> teats with<br />

the same soil.<br />

Structure changes were studied both by visual<br />

observati<strong>on</strong>s and by investigati<strong>on</strong>s of microecopic<br />

secti<strong>on</strong> of representative soil areas.<br />

Resulting soil aenaity, temperature and water<br />

1186<br />

c<strong>on</strong>tent were also measured in the wrious<br />

points though the V O~W~.<br />

Plate settlement in time was fixed usual by<br />

way and the typical results are Shorn <strong>on</strong><br />

Figure I.<br />

Generally, a frozen soil under a loaded pXab<br />

defoms like a multicomp<strong>on</strong>ent system with<br />

phase transiti<strong>on</strong>s and comp<strong>on</strong>ent relative mowments<br />

occuring. Near the plates footiia z<strong>on</strong>e<br />

of compressed soil usually named as soil core"<br />

is obtained where soil density increases<br />

and a high looal pressure occurs <strong>on</strong> the particle<br />

c<strong>on</strong>tacts. This leads to an ice melting<br />

and the unfrozen water migrati<strong>on</strong> to the less<br />

stressed outlying z<strong>on</strong>es where it freezes <strong>on</strong>ce<br />

again. Corresp<strong>on</strong>dingly, soil temperature was<br />

found to decrease nearby the plate and to increase<br />

at the remote areas due to latent heat<br />

of phase transiti<strong>on</strong>s. Visually, there are no<br />

ice layers within the core z<strong>on</strong>e whereas a fanlike<br />

system of such layers Is obtained around<br />

it .<br />

Depending <strong>on</strong> the loads level, the various<br />

types of structure detarLorating processes<br />

are to be prevailing <strong>on</strong>e.<br />

when a load is high enough, n soil under the<br />

plate fails its bearing capacity Fn time, tha<br />

can 'be neglected for practice. mre brittle<br />

failure takes place characterized by macroscopic<br />

cracks inltiating instant growth and<br />

merging, a3 it is shown <strong>on</strong> Figure 2. Microstructural<br />

analyses ahow the inltial imperfecti<strong>on</strong>s<br />

leading role LI the failure process. The<br />

intrknsic soil. cracks, cavities, inclusi<strong>on</strong>s<br />

and so <strong>on</strong> Initiate stress c<strong>on</strong>centrati<strong>on</strong> and<br />

unlimited cracks development up to ,the Ful<br />

destructi<strong>on</strong>.<br />

At fixst, macfoscopic cracks of 45O incline<br />

were observed under the plate ends. Then a

fan-like system of such cracks was formed, in the laboratory sample teats. Their equal<br />

added by vertical cracks, reaching free sol1 valiaity is supposed at the every point of<br />

surface. The average macroscopic cracks length homogeneous soil volume.<br />

slightly exceeded the plate width (30 m). No<br />

essential changes were found in soil. density The set of creep curves, which has been obtainand<br />

water c<strong>on</strong>tent distributi<strong>on</strong> (see Figure 3). ed in uniaxial compressi<strong>on</strong> teste is shown <strong>on</strong><br />

Figurn 51 Tested Soil was the same with that<br />

'men 2 load is still high but unsufficient used in the plate experiments.<br />

for inst;ant failure (e.@;. 6.5 MPa in our teste<br />

plate settlement grows up with time in- very The following peculiarities should noted be<br />

tensively (see curve 1 <strong>on</strong> Figure 1). Micro- geaexallyr<br />

structural analyses as well as visual obser- -instant failure of brittle type is obtained,<br />

vati<strong>on</strong>a give an evidence of macroscopic crack if strees ap lied is high enough8<br />

nucleati<strong>on</strong> under the plate end at the first - up to the natant strength value if fading or<br />

moment. During a following viscoplnatic flow, unfading with time viscoplastic flow takes<br />

initially opened cracks are closing gradually, place depen&ing <strong>on</strong> the level of stress applled<br />

but microcracks of new type occur and inten- - it is suitable to present the Pull deformasively<br />

propogate due to viacoplastkc deforma- ti<strong>on</strong>s as khe sum of puaai-instant and creep<br />

ti<strong>on</strong> devolopment. A new formed set of micro- parts, each. of these can include both revexcracks<br />

has a str<strong>on</strong>g influence <strong>on</strong> the flow rate sabJe and Irreversable comp<strong>on</strong>ents (see Figure<br />

which increases with microcracking. In the test 6) ;<br />

discussed settlement rate value finally reach- - all qp three successive Cree eta BB<br />

ed 0.8 mm/sec. Corresp<strong>on</strong>ding soil state &ould maq (E 4- 0 >, sec<strong>on</strong>dary ( 8- 0 f<br />

- priand<br />

terbe<br />

evidently regarded as a damaged <strong>on</strong>e.<br />

tiary ( fro ) creep Os generally observed<br />

in frozen soils;<br />

Typiaal settlement-to-time curves fixed under - the reaulting strain value depends str<strong>on</strong>gly<br />

8. moderate loads also are presented <strong>on</strong> Figure <strong>on</strong> changing stress hist<strong>on</strong>,<br />

1 ("2" -6d+oC) D, "3" - 6 '~ 3.7 Eapa>o Ib<br />

this experiment settlement rate values reached<br />

I<br />

corresp<strong>on</strong>dingly2,8RO-2 and 5,5 dinin A<br />

mixed type of failure takes place which cha- hrIfl'I'HEWTfCBL MODEL<br />

mcterized by essential development of both<br />

viscoplastic and brittle structure deteriora- lo describe menti<strong>on</strong>ed peculiadties the matheti<strong>on</strong>s<br />

through a soil volume. The set of mlcro- matical model early proposed by the authors<br />

cracks tends to be a regular <strong>on</strong>e with a prey (Razbegin, 1983, 1985) is developed here. The<br />

ferable cracks orientati<strong>on</strong> Formed in acco- graphic illustrati<strong>on</strong>s of tbLs model by help of<br />

dance with the marFmum shear sereas directi<strong>on</strong>a. standardrheolpgical elemento is- shown <strong>on</strong> Figure<br />

L<strong>on</strong>g-term plate indentati<strong>on</strong> under a small 7. Here the block nl" sirnulatea a quasi-insloads<br />

goes <strong>on</strong> without essential. ruptuxes. Only tad elastoplastic behadour; ''2" - presents<br />

a limited number of isolated cracks occuxs viscoslaatoplastic deformati<strong>on</strong>s developrag In<br />

which infinitesimal summarized area as aell time.<br />

as low cracks density in any representative (;banging rate of dscoemscoplaesia behaviour<br />

Soil volume allows to ignore cracks influence is c<strong>on</strong>nected with the element v'2T2" which si<strong>on</strong><br />

the mechanical behaviour. Pure viscoplastic mulates a n<strong>on</strong>-linear (strain rate)-to-(aotive<br />

flow takes place. Typical settlement-to-time stress) relati<strong>on</strong>ship. An "actOve" -stress is<br />

curve at the such loading c<strong>on</strong>diti<strong>on</strong>s la shown defined as the difference between total streas<br />

<strong>on</strong> Figure I (line "4"). It has been obtained applied and viscoelastic due to viscoelastic<br />

from the test, when the average plate stress deformafi<strong>on</strong>s gxowth. As it waa established in<br />

5 I 1.7 ma acted till. 34 days. Up to the sgecial unloading tests, the values of viscoend<br />

of this test a water c<strong>on</strong>tent; in core z<strong>on</strong>e elastic moauli were not to be a c<strong>on</strong>stant till<br />

under the plate decreased fmm 0.30 ini- vtscoplaetic flow. Their changes are cause& by<br />

tially to 0.27. In outlying areas wat-er c<strong>on</strong>- the intensive microcxackb.g through a soil<br />

tent reachod finally the value 1.34. Gradual volume. To illustrate this a syatem of breakdisappearance<br />

of ice layers in the core ing springs is introduced into the element<br />

z<strong>on</strong>e can see clearly <strong>on</strong> Fi . Sol1 density "2.1". Before the c<strong>on</strong>stitutive equati<strong>on</strong>s wLll<br />

has increased to 1.73 g/cm$lre in core z<strong>on</strong>e and be set up Tor model proposed, note *he Quasiwaa<br />

approximately c<strong>on</strong>stant (1.7 g/cm3) in out- Lnstant plastic deformati<strong>on</strong>s can take of great<br />

lying areas. Generally, cope z<strong>on</strong>e extenaea importance if the dynamic effects are signiwith<br />

time.<br />

ficant, but under a static load applied their<br />

Proceeded fmm menti<strong>on</strong>ed above it can be c<strong>on</strong>- influence is neglectable.<br />

cluded that peculiarities of stress-strain Then it can be written down:<br />

behavtour of frozen soil are determined mainly<br />

by Interacti<strong>on</strong> of structure reorganizati<strong>on</strong><br />

processes of brittle and viscoplastic types.<br />

Depending <strong>on</strong> stress level, each of them can be<br />

prevailing <strong>on</strong>e. It shoad carefully be taken<br />

into account by any complete theoretical model<br />

t3 predict mechanical behaviour of frozen<br />

soils 0<br />

By usual methods of c<strong>on</strong>tinuum mechanics, to<br />

calculate a plate settlement under a certain<br />

Load, the stress-strain-time relati<strong>on</strong>ships<br />

need to be known, which usually established<br />

1187

For the followhg, an assumpti<strong>on</strong> can be made<br />

in accordance with lu~own ex erimental data<br />

(Vyalov, 1986) : 6 a F; (IqJ JLf<br />

where J2 - the sec<strong>on</strong>d Invariant of deoiatoric<br />

stress tensor, and<br />

CBJ<br />

Here<br />

total strabs;<br />

~uasi~instant; stralns 8<br />

E' ' viscoelastoplarstic serawe;<br />

LJ<br />

viscoelastic etxaue;<br />

EJP<br />

viscoplastic straws;<br />

d~g, quasi-instaneoua elastio modulus4<br />

- total stress;<br />

Tg I ~'actSven stress (the difference<br />

between total stress applied and<br />

visooelaatio reeistmce; riscoelastoplaetic<br />

strain rate io defined<br />

atrectly by %his tensor value);<br />

4.<br />

viscoelastic stress;<br />

(a) - symbol of In-time derivative ;<br />

vlscoelastic modulus (are champ8<br />

E$& due to mlcxocracki )i<br />

A - damaging parameteryis introduced fox<br />

t;aking into amount microcracks dedeloped;<br />

<strong>on</strong>e can be regarded as the<br />

average volume of microcracka c<strong>on</strong>thuum<br />

at a certain point of soil<br />

media) ;<br />

[(d,j$$) - scalar damaging functi<strong>on</strong> (pmeents<br />

an average length of plane, narrow<br />

microcracks being plscced perpen8lcularly<br />

to the vector n [pJ&)<br />

A - an angle between cracks<br />

directi<strong>on</strong> and fixed coordinate system<br />

in the plae of the arack; this<br />

functi<strong>on</strong> Is determined In any poink<br />

through a soil volume);<br />

In xespeot of Figure 7, eQUatiOI3 (2) describes<br />

the behaviour of element rrlt' and egs (3)-(10) .<br />

- that of elemenb "2".<br />

(4) -,an (active) stresa)~to-(viscoelaatoglaotic<br />

strain rate) relatioaship.<br />

In the most Reneral caset<br />

. "<br />

F, , FA , PJ - functi<strong>on</strong>s of the<br />

wbere<br />

stress tensor invariants.<br />

- soil parameters.<br />

Usually a volume strains increment due to <strong>on</strong>ly<br />

Qdrostafic pressure is neglectable. The ratio<br />

( C, /Cz = c ) is a dilatancy coefficient. UP to<br />

the sta of intensive microcracks growth<br />

appears to be a c<strong>on</strong>stant, rising<br />

essentially after it.<br />

f. i7 ) is the equati<strong>on</strong>s accepeed as in the<br />

usual plaaticity theory to describe irreversable<br />

part of viscoelastoplastic strain increments.<br />

A plastic potential surface supposed to<br />

be the same with a yield surface being placed<br />

at the viacoelastic stress space (not at the<br />

total atxeae space). Analogical assumpti<strong>on</strong>s<br />

has been early made in (Ivlev, 1971 ; ZaretcQ,<br />

q983). Figure 0 sihows a posaible form of the<br />

yield surface. Eas (q), (IO) are a klnetic<br />

<strong>on</strong>es for the damaging arametex. A general<br />

thexmodyramical force (P', d,p,<br />

is in+broducsd to describe growt of any indivfdual<br />

crack. Crack length incxement assumes<br />

to be fully Irreversable and corresp<strong>on</strong>ding<br />

functi<strong>on</strong> of mechanical energy dissipati<strong>on</strong> assumes<br />

to be homogeneous of degree 1 in respect<br />

of this increment. One can be written down<br />

c<strong>on</strong>sequently:<br />

3 &-)*o; d % =o ('12)<br />

Here Re - an initial tbr sho d or<br />

- an initial increment of crack length; x<br />

microcracks development starting; !+z k e",<br />

- hardening functi<strong>on</strong> <strong>on</strong> the cracks length and<br />

some additi<strong>on</strong>al parameters.<br />

In general case R (%, (d,,~ 6-/ looks in.t;ricate<br />

enough. For a plane-strain c<strong>on</strong>diti<strong>on</strong>s it<br />

where k; -stress intensity fa*r to describe<br />

the stress distributi<strong>on</strong> nearby tbe cracks top.<br />

1188

Scalar functi<strong>on</strong> e(& p, b-) seems to be suffi- To get (21) some additi<strong>on</strong>al assumpti<strong>on</strong> has<br />

cient for taking indo accout the main featu- been adopted. Particularly, hydrostatic presres<br />

of microcracks c<strong>on</strong>tinuum. At the beginning sum influence is no taken into a count for<br />

this functi<strong>on</strong> should evidently be a c<strong>on</strong>stant shear deformati<strong>on</strong>s development ; 4 is asfrom<br />

polnt to oint thxough a soil volume and Sued to be c<strong>on</strong>stant, so, the shear and the<br />

for any d, p, f when initially isotropic, volume strain-to-time curves axe similar. me-<br />

homogenous soi i regarded. In the lain- vertheless, (21) successfully describes the<br />

atreas case is![&. and ~ cP-,

1190

J<br />

L<br />

Pig-8, Rheological elements illustrati<strong>on</strong> to<br />

moqel propoeedc<br />

I<br />

pig.9.<br />

Yield surface.<br />

Fig*G. Creep curves in uniaxial compressi<strong>on</strong><br />

tests under c<strong>on</strong>stant atremes. MPa:<br />

:b$"=--<br />

3<br />

4<br />

Fig.10.<br />

Plate settlement: I - experimental,<br />

2 - calculated,<br />

Pie..<br />

Idealized creep curve (with unloading)<br />

1191

-- FROST HEAVING FORCES ON FOUNDATIONS IN SEASONALLY FROZEN GROUND<br />

lXu, Shaoxin<br />

Heil<strong>on</strong>gjiang Provincial <strong>Research</strong> Institute of Water C<strong>on</strong>servancy<br />

SYNOPSIS All three types<br />

of frost heaving forces, i.e., tangential, normal and horiz<strong>on</strong>tal,<br />

are examined in this paper. The results of laboratory and f ield experiments show tbat the three<br />

types of frost heaving forces have not <strong>on</strong>ly the same physica 1 meaning but also a similar process of<br />

generati<strong>on</strong> and development. C<strong>on</strong>sequently, the values of the three types of forces can be examined<br />

and estimated from each other.<br />

INTRODUCTION<br />

In seas<strong>on</strong>al frost areas, freezing ground exerts<br />

heaving forces <strong>on</strong> the foundati<strong>on</strong>s of structures<br />

when frost heave of the ground is restrained by<br />

the foundati<strong>on</strong>. Based <strong>on</strong> the difference in the<br />

form of restraint, frost heaving forces are<br />

generally classified as three types: tangential<br />

frost heaving force, horiz<strong>on</strong>tal frost heaving<br />

force <strong>on</strong> the lateral surface of a foundatin, and<br />

normal frost heaving force acting vertically <strong>on</strong><br />

a'foundati<strong>on</strong>. C<strong>on</strong>sidering the physical basis of<br />

their generati<strong>on</strong>, all three forces are caused by<br />

the restraint to volume expansi<strong>on</strong> or heave of<br />

the soil due to the phase-change of moisture to<br />

ice. Further analysis of laboratory and field<br />

experiment data indicates that the three types<br />

of frost heaving forces not <strong>on</strong>ly have the same<br />

physical basis but also are similar wfth regard<br />

to the combined acti<strong>on</strong> of temperature, moisture<br />

andstress fields in the generati<strong>on</strong> and development<br />

of the forces. In similar foundati<strong>on</strong> soils<br />

some close relati<strong>on</strong>ships exist am<strong>on</strong>g the three<br />

types of frost heaving forces. This means that<br />

empirical examinati<strong>on</strong> and estimati<strong>on</strong> of the three<br />

types of forces from each other can be made.<br />

DISCUSSION<br />

Tangential Frost Heaving Force <strong>on</strong> Pile Founda--<br />

t iolls<br />

The adfreezing b<strong>on</strong>d strength between a pile and<br />

the surrounding frozen ground is a prerequisite<br />

for the generati<strong>on</strong> of tangential frost heaving<br />

forces <strong>on</strong> the lateral surface of a pile. The<br />

volume cxpansi.<strong>on</strong> due to the phase-change of<br />

water-to-ice in the surrounding soil is the<br />

source-of the force. The weight of a pile, applied<br />

load and compressibility of the underlying<br />

unfrozen soil are the main factors influencing<br />

the magnitude of the tangential frost heaving<br />

force.<br />

A literature survey shows that most of the experimental<br />

investigati<strong>on</strong>s <strong>on</strong> the tangential frost<br />

heaving furce <strong>on</strong> piles focused <strong>on</strong> the infl.uence<br />

of moisture, temperature and properties of the<br />

pile material. Without any doubt, a clear understanding<br />

of the generati<strong>on</strong>, development and<br />

variati<strong>on</strong> of the force can be attained with the<br />

method of m<strong>on</strong>ofactor analysis. In engineering<br />

practice, however, the requirement for preventing<br />

the frost uplift of a pile foundati<strong>on</strong> is that<br />

the tangential frost. heaving stress must be less<br />

than the adfreezing strength.<br />

Investigati<strong>on</strong>s show that the magnitude of the<br />

tangential frost heaving force <strong>on</strong> a pile depends<br />

chi.efly <strong>on</strong> the frost-heave susceptibility of the<br />

surrounding soil and the degree of the pile's<br />

restraint to frost heave. In c<strong>on</strong>sidering the<br />

stability of a pile subjected to frost uplift<br />

for design, the following formula is generally<br />

used as the stability criteri<strong>on</strong>:<br />

0~ *SSP + G + fmsl (1)<br />

where 0~ is the tangential frost heaving stress;<br />

P is the applied load <strong>on</strong> the pile;<br />

G is the weight of the pile;<br />

f is the fricti<strong>on</strong> between the pile and<br />

unfrozen soil;<br />

S is the surface area of the secti<strong>on</strong> of<br />

the pile in c<strong>on</strong>tact with the frozen<br />

soil layer;<br />

and S1 is the surface area of the secti<strong>on</strong> of<br />

the pile in c<strong>on</strong>tact with the unfrozen<br />

soil layer.<br />

If the right side in eq.(l) is greater thanoT*b,<br />

then the magnitude of the tangential force depends<br />

<strong>on</strong> the frost heaving potential of the surrounding<br />

soil. In this case, the buried pile<br />

foundati<strong>on</strong> restricts the upward frost heave deformati<strong>on</strong><br />

of the surrounding soil body. According<br />

to laboratory and field experiments, the<br />

radius of influence ( I) is approximately equal<br />

to the frost deplh H (see Fig.1).<br />

If a loading plate with the samecross-secti<strong>on</strong> as the<br />

pile i.s used to restrain fully the frost heave<br />

deformati<strong>on</strong> of the underlying soil, then the<br />

angle of the irost heaving stress in the subgrade<br />

is generally regarded as 45O; t.hat j.s, the radius<br />

of influence (1) of the stress is also equal to<br />

1192

Fig.1 Frost Heave Around<br />

a Pile (a) and' Under a Loading Plate (b)<br />

frost depth H. The temperature, moisture and<br />

stress fields for the above two cases are quite<br />

similar, so that frost heave of the surrounding<br />

soil subjected to a pile's restraint is very<br />

similar to that of the subgrade soil around the<br />

edge of a loading plate subjected to the plate's<br />

restraint. As a result, the total frost heaving<br />

Eorces for the two cases should be roughly equal.<br />

For comparis<strong>on</strong>, the total tangential frost heaving<br />

forces <strong>on</strong> a series of model piles and the<br />

total normal frost heaving forces <strong>on</strong> a series of<br />

loading plates with the same diameters as the<br />

piles, were measured at Wangjia Frozen Soil -.<br />

Field Stati<strong>on</strong> (where the soils are of medium<br />

frost susceptibility).The observed values were<br />

shown in Table I.<br />

TABLE 1<br />

Observed Values of Total Tangential Frost<br />

Heaving Force <strong>on</strong> a Series of Files and<br />

Total Normal Frost 'Heaving Force <strong>on</strong><br />

Loading Plates with the Same<br />

Diameters as the Piles<br />

'<br />

values of normal frost heaving forces <strong>on</strong> plate<br />

foundati<strong>on</strong>s have been c<strong>on</strong>ducted in recent years.<br />

Since the test plates are all small and the<br />

boundary, c<strong>on</strong>diti<strong>on</strong>s are quite different in these<br />

investigati<strong>on</strong>s, the measured values of the force<br />

are so different that they could not be used in<br />

engineering practice. Although there are many<br />

factors influencing normal frost heaving force,<br />

they can be classified in two groups, i,e,,<br />

natural c<strong>on</strong>diti<strong>on</strong>s and engineering c<strong>on</strong>diti<strong>on</strong>s.<br />

The natural c<strong>on</strong>diti<strong>on</strong>s are the prerequisites<br />

for the generati<strong>on</strong> of the force and can be<br />

divided into:<br />

(i)<br />

(ii)<br />

(iii)<br />

Soil characteristics--mineralogical<br />

comp<strong>on</strong>ents, particle compositi<strong>on</strong>, unit<br />

weight, permeability of the underlying<br />

soil, and compressibility of the unfrozen<br />

soil layer:<br />

Moisture c<strong>on</strong>diti<strong>on</strong>s--water c<strong>on</strong>tent and<br />

dissolved salt c<strong>on</strong>tent in soil, groundwater<br />

level, etc.;<br />

Thermal. c<strong>on</strong>diti<strong>on</strong>s--freezing index,<br />

thermal properties of soil, frost penetrati<strong>on</strong><br />

rate, ground thermal regime,etc.<br />

The engineering c<strong>on</strong>diti<strong>on</strong>s which are basic to<br />

Diameter (cm)<br />

50 75 100 125 the magnitude of normal frost heaving force<br />

include foundati<strong>on</strong> shape and size, buried depth,<br />

Total tangential frost heaving applied load, and degree of restraint to frost<br />

14.9 19.4 26.4 35.7<br />

force <strong>on</strong> a pile (x10 N)<br />

heave of the subgrade.<br />

Total normal frost heaving force 15.7 21.6 27.5 36.8<br />

<strong>on</strong> a loading plate (x10 N)<br />

It can bo seeu from Tahlv I ChaL thc values of<br />

the two types of frost heaving forces for a certain<br />

diameter are very close. Therefore, the<br />

tangential frost heaving force <strong>on</strong> piles can be<br />

estimated frum the values of normal frost heaving<br />

force measured <strong>on</strong> loading plates heaving the<br />

same diameters as the piles and under the same<br />

freezj.ng c<strong>on</strong>diti<strong>on</strong>s.<br />

Normal Frost Heaving Force <strong>on</strong> Plate Foundati<strong>on</strong>s<br />

Many experimental investigati<strong>on</strong>s to determine<br />

1193<br />

For engineering purposes, the magnitude of the<br />

normal frost heaving force depends chiefly <strong>on</strong><br />

the degree of the foundati<strong>on</strong>'s restraint and<br />

natural c<strong>on</strong>diti<strong>on</strong>s. If frost heave of the underlying<br />

soil is restricted <strong>on</strong>ly by the Load<br />

applied <strong>on</strong> the foundati<strong>on</strong>, then the normal frost<br />

heaving force is equal to the applied load. If<br />

a foundati<strong>on</strong> is fully restrained to frost-heave<br />

displacement, the magnitude of the normal frost<br />

heaving force depends <strong>on</strong> the base area of thc<br />

foundati<strong>on</strong> and the compressibility of the underlying<br />

unfrozen soil layer. Based <strong>on</strong> statistical<br />

analysis, T<strong>on</strong>g and Yu (1983) presented an empirical<br />

formula c<strong>on</strong>cerning the relati<strong>on</strong>ship<br />

between the loading p1at.e area and normal frost<br />

heaving pressure. To experimentally investigate<br />

the normal frost heaving force as a functi<strong>on</strong> of<br />

loading plate areas, frost heave tests were per-

formed at Wangjia Frozen Soil Field Stat.i<strong>on</strong><br />

a serics of places with results as shown in<br />

Fig.2.<br />

<strong>on</strong><br />

It can be seen from Table I I that the effect of<br />

the surrounding soil <strong>on</strong> the normal frost heaving<br />

force decreases with incrcasing pl~te area, The<br />

cotal normal frost heaving force finally tends<br />

to be the so-called pure normal frost heavi.ng<br />

force without an "additi<strong>on</strong>al" effect. The<br />

Y<br />

magnitude of the'pure"norma1 frust heaving force<br />

is dependent up<strong>on</strong> the compressibility of the underlyi.ng<br />

unfrozen soil. .Its maximum value cannot<br />

exceed the ultimace strength of the soil.<br />

Horiz<strong>on</strong>tal Frost heaving Force Acting <strong>on</strong> RetaininE<br />

Walls<br />

It is well known that at air cemperatures below<br />

O'C, the backfill behind a retaining wall. experiences<br />

freezing in two directi<strong>on</strong>s. Isotherms<br />

in the fill are shown in Fig.3+ Upward frost<br />

heave of the upper porti<strong>on</strong> of the fill does not<br />

refult in large forces acting <strong>on</strong> the wall, But,<br />

Loading plate area. ma<br />

Fiy.2 Loading Plate Area vs Normal<br />

Frost Heaving Pressure<br />

It can be seen from Fig.2 that the normal frost<br />

heaving pressure increases with decrease in<br />

plate area. The reas<strong>on</strong> why higher normal frost<br />

heaving pressures were measured <strong>on</strong> smaller plates<br />

j.s that, while freezing, the plate was subjected<br />

to a so-called "additi<strong>on</strong>al" normal frost heaving<br />

pressure resulting from frost heave of the soil<br />

bey<strong>on</strong>d the edge of the plate. This additi<strong>on</strong>al<br />

pressure decreases with an increase in plate<br />

area. The ratio (in percent) of the fieldmeasured<br />

and calculated "additi<strong>on</strong>al" frost heaving<br />

pressures,Ua , to the total pressures,q, <strong>on</strong><br />

plates with different areas are presented in<br />

Table 11.<br />

TABLE I1<br />

Ratio (in percent) of the Addi-ti<strong>on</strong>al Normal<br />

Frost heaving Pressure (Ua) to Total<br />

Normal Frost Heaving Pressures (ut)<br />

<strong>on</strong> Loading Plates with<br />

Various Areas<br />

Plate areas (m') 0.01 0.25 1.0 4.0 9.0 25.0 100<br />

oa/ut (X) 99# 90.7" 76.31b 60.3* 45.2* 31.5" 18.3%<br />

'$ measured # calculated<br />

'l'hc normal frost heaving f(JrCF: <strong>on</strong> a small plate<br />

is produced mainly by the frost heaving stress<br />

in the surrounding soil and c<strong>on</strong>veyed to the plate<br />

by means of the strength of frozen soil. 111 a<br />

similar way, the tangential frost heaving force<br />

<strong>on</strong> a pile is also caused by thc frost heaving<br />

stress i.n the surrounding soil and c<strong>on</strong>veyed to<br />

the pile by means of the adfreezkng strength<br />

between the pi,le and the soil. Therefore, the<br />

two types of frost heaving fnrces can be mutually<br />

examined and evaluated.<br />

'<br />

Fig.3 Isotherms Behind<br />

a Retaining Wall<br />

due to the wall's restraint it will be subjected<br />

to horiz<strong>on</strong>tal frost heaving forces. The magnitude<br />

of the horiz<strong>on</strong>tal force, like tangential<br />

and normal frost heaving forces, depends <strong>on</strong> the<br />

degree of restraint and the natural c<strong>on</strong>diti<strong>on</strong>s<br />

of frost.heave. When frost; penetrati<strong>on</strong> is relatively<br />

shallow, he horiz<strong>on</strong>tal frost heaving<br />

force <strong>on</strong> a elastic, thin retaining wall can be<br />

calculated based <strong>on</strong> the di,splacement of the wall.<br />

Behind a regid retaining wall, frost heave of the<br />

fill is fully restrained by the well and the displacement<br />

of the wall i.s close to zero. In this<br />

case, the horiz<strong>on</strong>tal frost heaving pressure is<br />

equal to the normal frost heaving pressure under<br />

full restraint. Tts maximum value cannot exceed<br />

the ultimate stength of the frozen soil.<br />

When the isotherms in the soil behind a low<br />

retaining wall (i-e., its height is close to the<br />

frost pcnetrati<strong>on</strong> depth) arc curved 1i.nes and<br />

the frost heaving force is normal to the isotherms,<br />

then the distributi<strong>on</strong> of horiz<strong>on</strong>tal frost heaving<br />

pressure <strong>on</strong> the wall can bc quite variable. If<br />

the back fill is cohesive soil and the groundwater<br />

level is below the ground surface, then the distributi<strong>on</strong><br />

of pressure <strong>on</strong> the wall is as shown in<br />

Fig.4, where h is the exposed height of thc wall,<br />

II is the maxi.mum frost depth, and B is the point<br />

at which the maximum pressure occ.urs.<br />

For a high wall with freezing occurring in two<br />

directiuns, the distributi<strong>on</strong> of horixuntal pres-<br />

1194

7<br />

A<br />

1.<br />

El<br />

(iii)<br />

Fig.4 Distributi<strong>on</strong> of the Horiz<strong>on</strong>tal Frost<br />

Heaving Pressure <strong>on</strong> a Low Retaining Wall (iiii)<br />

sure <strong>on</strong> the wall can be represented as shown in<br />

Fig.5. In this case, the maximum pressure occurs<br />

within secti<strong>on</strong> BC where the isotherms are parallel<br />

to the wall. Points B and C represent major<br />

changes in directi<strong>on</strong> of the isotherms.<br />

by the frost heave of the surrounding<br />

S U J , ~ body, It can be estimaLed or<br />

examlned by comparing it with the normal<br />

frost heaving force acting <strong>on</strong> a loading<br />

plate having the same cross-secti<strong>on</strong>al<br />

area as the pile.<br />

‘The normal frost heaving pressure <strong>on</strong> a<br />

plate foundati<strong>on</strong> decreases with an increase<br />

in plate area. Because of the<br />

substantial influence of frost heave in<br />

the surrounding soil, the normal frost<br />

heaving pressure measured <strong>on</strong> a small loading<br />

plate should not be used in enyineering<br />

practice. The pure normal frost heaving<br />

pressure can be c<strong>on</strong>sidered as the<br />

total normal pressure for a Large plate,<br />

but its maximum value cannot exceed the<br />

ultimate strength of the underlying soil.<br />

The distributi<strong>on</strong> of horiz<strong>on</strong>tal frost<br />

heaving pressure <strong>on</strong> a retaining wall<br />

depends <strong>on</strong> the height of wall. Its maximum<br />

pressure is not greater than the<br />

pure normal frost heaving pressure, for<br />

the same frost depth.<br />

For a rigid high retainl.ng wall with its backfill REFERENCE<br />

fully restrained and assuming the same frost<br />

depth, the maximum horiz<strong>on</strong>tal frost heaving pres- Changjiang T<strong>on</strong>g and Ch<strong>on</strong>gYun Yu, (1983)n<strong>Research</strong><br />

sure is equal to the pure normal frost heaving <strong>on</strong> the frost heaving force of soils. Proc.<br />

pressure. 4th Intern. C<strong>on</strong>f.<strong>Permafrost</strong>,<br />

Washingt3n D.C. Nati<strong>on</strong>al Academy Press 1383.<br />

A<br />

B<br />

I<br />

C<br />

D<br />

I<br />

Fig.5 Distributi<strong>on</strong> of the Horiz<strong>on</strong>tal Frost<br />

Heaving Pressure <strong>on</strong> a High Retaining Wall<br />

CONCLUSIONS<br />

(i)<br />

(ii)<br />

The tangential, normal and horiz<strong>on</strong>tal<br />

frost heaving forces have not <strong>on</strong>ly the<br />

same physical basis but also many similar<br />

characteristics. The magnitude of all<br />

three types depends chiefly <strong>on</strong> the associated<br />

engineering c<strong>on</strong>diti<strong>on</strong>s and<br />

natural factors. Suitable experimental<br />

values for these forces should be chosen<br />

for design based <strong>on</strong> previous engineering<br />

practice.<br />

The tangential frost heaving force acting<br />

<strong>on</strong> a pile foundati<strong>on</strong> is caused chiefly<br />

1195

ON THE DISTRIBUTION OF FROST HEAVE WITH DEPTH<br />

Zhu, Qiang<br />

Water C<strong>on</strong>servancy Department of Gansu Province, China<br />

SYNOPSIS The distributi<strong>on</strong> of frost heave with depth is of great importance in areas which<br />

experience seas<strong>on</strong>al frost. Based <strong>on</strong> the field experiments carried out in Gansu Province since 1979,<br />

this paper classifies the heave distributi<strong>on</strong> into 4 types: high heave ratio layer occuring in the<br />

upper, lower and middle part of the frozen soil and heave distributed with relative evenness in the<br />

frozen soil. The relati<strong>on</strong>ship between distributi<strong>on</strong> patterns and water-soil c<strong>on</strong>diti<strong>on</strong>s is discussed<br />

and an explanati<strong>on</strong> using the principle of water migrati<strong>on</strong> is presented. The c<strong>on</strong>cept of so-called<br />

''major heave layer" is correct <strong>on</strong>ly in the closed freezing system. In the open system various types<br />

of heave distributi<strong>on</strong> may occur depending <strong>on</strong> the water supply c<strong>on</strong>diti<strong>on</strong>s. The author also provides<br />

a mathematical model to verify the effect of ground water <strong>on</strong> the heave distributi<strong>on</strong>.<br />

INTRODUCTION<br />

In areas which experience seas<strong>on</strong>al frost, the<br />

distributi<strong>on</strong> of frost heave with depth is of<br />

great importance for determining the depths of<br />

foundati<strong>on</strong>s and the thickness of sand-gravel<br />

required for subsoil replacement. In the past,<br />

it was assumed that more than 2/3 of the heave<br />

is c<strong>on</strong>centrated in the upper 1/3 to 1f2 part of the<br />

frozen soil, in the so-called "major heave<br />

layer". Some investigators in c<strong>on</strong>structi<strong>on</strong><br />

engineering have presented data to prove the<br />

existence of this type of distributi<strong>on</strong> and derived<br />

design criteria for shallow foundati<strong>on</strong>s.<br />

Since late 1970's, however,investigators in the<br />

field of hydraulic engineering, such as wang<br />

(1980), Zhu (1981) have pointed out that there<br />

are different types of heave distributi<strong>on</strong> according<br />

to soil and ground water c<strong>on</strong>diti<strong>on</strong>s.<br />

The "major heave layer" type is <strong>on</strong>ly a special<br />

case under specific c<strong>on</strong>diti<strong>on</strong>s. To date there<br />

is no unanimity of views <strong>on</strong> the classificati<strong>on</strong><br />

of the heave distributi<strong>on</strong> types and their relati<strong>on</strong>s<br />

to soil and ground water c<strong>on</strong>diti<strong>on</strong>s.<br />

In Gansu Province, China, under the Anti-Frost<br />

Heave Measures for Canal Lining Program, field<br />

experiments to study seas<strong>on</strong>al frost heave under<br />

various soil and ground water c<strong>on</strong>diti<strong>on</strong>s have<br />

been carried out extensively since 1979. Based<br />

<strong>on</strong> the data from these experiments, this paper<br />

summarizes four frost heave distributi<strong>on</strong> types<br />

and their relati<strong>on</strong>s to soil and ground water<br />

c<strong>on</strong>diti<strong>on</strong>s. A mathematic model of coupled heat<br />

and moisture transfer is applied to verify the<br />

c<strong>on</strong>clusi<strong>on</strong>s of the experiments and the effect<br />

of ground water <strong>on</strong> the heave distributi<strong>on</strong>.<br />

EXPERIMENTAL RESULTS<br />

The field experiments are carried out at the<br />

Zhangye Frost Heave Stati<strong>on</strong>, the Daman Main<br />

Canal, the Minqin Testing Canal and the Ginghui<br />

Main Canal. Each site is characterized by different<br />

soil and water c<strong>on</strong>diti<strong>on</strong>s. Based <strong>on</strong> the<br />

312 sets of data obtained at these sites,it was<br />

determined that the actual heave distributi<strong>on</strong>s<br />

can be classified into four types depending <strong>on</strong><br />

the positi<strong>on</strong> of the high heave ratio (HHR*)<br />

layer. These include heave distributi<strong>on</strong> where:<br />

a) the HHR layer located at the upper half of<br />

the frozen soil, b) the HHR layer at the lowef<br />

half of the frozen soil, c) the HHR layer is<br />

located in the middle half of the frozen soil<br />

and d) heave is distributed with relative evenness.<br />

These four types referred to as type A ,<br />

B, C and D respectively. Am<strong>on</strong>g them, A and B<br />

are the most comm<strong>on</strong> making up 80% of the 312<br />

sets of data. A brief account of the c<strong>on</strong>diti<strong>on</strong>s<br />

of the test sites and heave distributi<strong>on</strong>s at<br />

each site are given in the following secti<strong>on</strong>s.<br />

Zhangye frost heave stati<strong>on</strong><br />

The soil at the Zhangye Stati<strong>on</strong> can be divided<br />

into five types:heavy silty loarn,sandy loam,fine<br />

sand and loam and sandy loam overlain by a coarse<br />

sand layer. The ground water table at each site<br />

are artificially c<strong>on</strong>trolled at depths of 1, 1.5<br />

and 2.5 m, respectively. A total of 15 testing<br />

units c<strong>on</strong>sisting of combin,ati<strong>on</strong> of soils and<br />

ground water c<strong>on</strong>diti<strong>on</strong>s were instrumented to<br />

measure frost penetrati<strong>on</strong>, soil temperature,soil<br />

moisture and heaving. The results from the experiments<br />

can be seen in Table I. The results<br />

indicate that when the ground water teble is<br />

close to the surface, such as in unit 100-1,2,3<br />

and 150-1,2,the heave distributi<strong>on</strong>s bel<strong>on</strong>g to<br />

type B, regardless of soil type. An example of<br />

this type of heave is shown in Fig.1. For deeper<br />

ground water c<strong>on</strong>diti<strong>on</strong>s, the main distributi<strong>on</strong><br />

type is A. For the loam and sandy loam covered<br />

with coarse sand, the distributi<strong>on</strong> mainly bel<strong>on</strong>gs<br />

to type B despite the varying ground water<br />

Heave ratio equals to Ah/AH, where Ah and AH<br />

represent the heave and the thickness, respectively,<br />

of the same layer.<br />

1196

, TABLE I<br />

Heave Distributi<strong>on</strong> Types in Zhangye<br />

Frost Heave Stati<strong>on</strong><br />

Unit Numbers<br />

of distribut i.<strong>on</strong> ty es<br />

number Total A B C E<br />

100-1 to 544 15 15<br />

150-1,2,4,5 6 6<br />

250-1,2 3 3<br />

250-4,5 4 4<br />

**The number before dash denotes the water depth<br />

in cm, the number after dash denotes soil<br />

types:<br />

1-heavy silty loam; 2-sandy Loam; 3"sand:<br />

4-loam under coarse sand: 5-sandy loam<br />

under coarse sand.<br />

TABLE 11<br />

Statistics of Heave Distributi<strong>on</strong> Types<br />

in Daman Main Canal<br />

Locati<strong>on</strong> of Numbersof distributi<strong>on</strong> types<br />

heave measur.ernent Total A B C D<br />

NS* upper haef 20 10 2 I 7<br />

NS* lower half 20 12 3 5<br />

bottom 22 21 1<br />

SS** -lower half 23 21 2<br />

SS upper half 25 23 2<br />

* NS: north- facing slope, that is the sun-exposed<br />

side and is warmer.<br />

**Ss: south facing slope, that is the shade side<br />

and is colder.<br />

e<br />

E<br />

&Or<strong>on</strong>nd<br />

water tahln<br />

Fig.1 Distributi<strong>on</strong> of Heave Ratio and<br />

Water C<strong>on</strong>tent of Unit 100-1 in Zhangye<br />

Frost Heave Stati<strong>on</strong><br />

depth ranging from 100 to 250 cm.<br />

Daman main canal<br />

This is a c<strong>on</strong>crete lined canal with subsoil<br />

mainly c<strong>on</strong>sisting of clay and heavy silty loam,<br />

replaced to various depths by sand-gravel. The<br />

ground water table varied from 0.5 m at the<br />

beginning of winter to 1.5 m at the end of winter.<br />

Table I1 summarizes the results and indicate<br />

the heave distributi<strong>on</strong> is mainly type B,<br />

which amounts to 71% of the data observed. It is<br />

apperenr. in the data from the north facing slopes<br />

that heave distributi<strong>on</strong> is also effects by positi<strong>on</strong><br />

relative to the ground water table. The<br />

shorter the distance between freezing fr<strong>on</strong>t and<br />

the ground water table, the higher the heave<br />

ratio. An example of test result from Daman<br />

Main Canal is shown in Fig.2.<br />

Ginnhui main canal<br />

The ground water table at the Ginghui Main Canal<br />

is deeply seated, so the freezing process is<br />

similar to a closed system. The suhsoil is a<br />

Fig.2 Distributi<strong>on</strong> of Heave Ratio and<br />

Water. C<strong>on</strong>tent of Point No.04 in Secti<strong>on</strong><br />

No.2, Daman Main Canal<br />

TABLE I11<br />

Statistics of Heave Distributi<strong>on</strong> Types<br />

in Ginghui Main Canal<br />

Locati<strong>on</strong> of Numbers of distributi<strong>on</strong> types<br />

heave measurement Total A B C D<br />

WS* upper half 19 17 2<br />

WS lower half 30 30<br />

bottom 10 7 3<br />

ES** lower half 30 18 2 10<br />

ES upper half 20 17 1 2<br />

* WS: west slope, the colder side.<br />

+*ES: east slope, the warmer side.<br />

loess with vertically developed fissures alluwing<br />

rapid downward drainage. The results arc<br />

shown in Table 111. The results indicate that<br />

over 80% of the site are characterized by type<br />

A heave distributi<strong>on</strong>, This type of heave is<br />

1197

very predominant <strong>on</strong> the colder west slopes where<br />

it makes up 96% of the total (Fig.3).<br />

Fig.3 Distributi<strong>on</strong> Curve of Heave Ratio<br />

and Water C<strong>on</strong>tent of WS Lower Half in<br />

Secti<strong>on</strong> No.1, Ginghui Main Canal<br />

Fig.4 Distributi<strong>on</strong> of Heave Ratio and<br />

Water C<strong>on</strong>tent of South Facing Slope in<br />

Secti<strong>on</strong> No.2, Minqin Testing Canal<br />

Minain testing canal seated ground water table, we can 'see from the<br />

The depth of ground water table of the Minqin soil moisture profile shown in Fig.3 that a high<br />

Testing Canal is about 4 m under the canal botmoisture<br />

c<strong>on</strong>tent z<strong>on</strong>e corresp<strong>on</strong>ding to the HHR<br />

tom. The soil is heavy silty loam and silty<br />

layer is present in the upper part of the frozen<br />

clay with poor drainage capability. The data soil. This z<strong>on</strong>e is caused by the increase of<br />

are shown in Table IV. When no replacement by moisture which occurs during freezing. Under<br />

sand takes place, the distributi<strong>on</strong> types are<br />

this layer, the moisture c<strong>on</strong>tent decreases and<br />

mainly A and D. In the case of replacement by ade-wateringz<strong>on</strong>e is present corresp<strong>on</strong>ding to a<br />

sand, the distributi<strong>on</strong> mainly bel<strong>on</strong>gs to type low or n<strong>on</strong>-heaving layer. The de-watering is'<br />

B, A typical. example of experimental resulta<br />

from a site with subsoil replacement by sand is<br />

shown in Fig.4.<br />

TABLE IV<br />

Heave Distributi<strong>on</strong> Types in<br />

Minqin Testing Canal<br />

Locati<strong>on</strong> of Numbers of distributi<strong>on</strong> types<br />

heave measurement Total A B C Ir<br />

~ ~<br />

without subsoil replacement<br />

NS upper half 6 1 2<br />

NS lower half 8 7<br />

bottom a 3<br />

SS lower half 8 2<br />

SS upper half 12 4<br />

With subsoil replacement by sand<br />

NS upper half 4. 4<br />

NS lower half . 4 3<br />

bottom 4 3<br />

SS lower half 4 4<br />

SS upper half 4 4<br />

1 2<br />

1<br />

4 '1<br />

6<br />

a<br />

HEAVE DISTRIBUTION VERSUS SOIL-GROUND WATER<br />

CONDITIONS<br />

1<br />

1<br />

due to two mechanisms: 1) as a result of seepage<br />

from the canal, the moisture in the upper part<br />

of subsoil is greater than that in the lower.<br />

The moisture transfers downward under the gradient<br />

of moisture c<strong>on</strong>tent and the gravity force,<br />

which is the main mechanism of de-watering in<br />

the well drainage capability soil; 2) since<br />

ground water table is quite deep, the source of<br />

water migrati<strong>on</strong> during freezing can <strong>on</strong>ly originate<br />

from the moisture redistributi<strong>on</strong> in a thin<br />

z<strong>on</strong>e beneath the HHR layer. According to the<br />

observed data, the thickness of de-watering<br />

layer affected by the redistributi<strong>on</strong> is about<br />

30 to SO cm. If it is assumed that all of the<br />

moisture causing 5 cm heaving originates from<br />

this layer, a loss of 8% water c<strong>on</strong>tent in the<br />

Lower 40 cm can be expected, In areas with<br />

shallowly seated ground water tables, no dewatering<br />

in the moisture profile ig observed.<br />

On the c<strong>on</strong>trary, the freezing fr<strong>on</strong>t approaches<br />

closer to the ground water table, the soil moisture<br />

c<strong>on</strong>tent increases rapidly as a result of<br />

water movement from the water table. Moisture<br />

c<strong>on</strong>tent exceeding 100% (by weight) were measured<br />

in the frozen soil below Daman Main Canal<br />

invert, Based <strong>on</strong> the results from Zhangye Frost<br />

Heave Stati<strong>on</strong>, correlati<strong>on</strong> curves of the heave<br />

ratio versus ground water depth have been determined.<br />

The equati<strong>on</strong>s for the curves for<br />

each soil type is given below.<br />

heavy silty loam ~=60.5exp(-0.01462) (1)<br />

In order to have a thorouah understandinR of sandy loam n=2a4/2 + 0.2 (2)<br />

heave distributi<strong>on</strong> at each site, it is neces- fine sand q=65.2/(2-10) + 0.15 (3)<br />

sary to study the change of soil moisture profjles<br />

during freezing. In the case of deeply<br />

1198

where q is heave ratio, in percentage; Z is the<br />

distance between the ground water table and the<br />

freezing fr<strong>on</strong>t in cm.<br />

When the subsoil is partially replaced by sand<br />

and/o,r gravel, no water migrati<strong>on</strong> occurs in the<br />

upper layer and the sec<strong>on</strong>d mechanism of dewatering<br />

menti<strong>on</strong>ed previously does not occur.<br />

De-watering resulting from gravity force may<br />

occur depending <strong>on</strong> the drainage capacity of the<br />

original subsoil. If the soil is very heavy<br />

and the drainage is poor, such as in the case<br />

of Minqin Testing Canal, the moisture c<strong>on</strong>tent<br />

in the original soil is large enough to support<br />

the water migrati<strong>on</strong>. then a HHR layer will<br />

appear directly below the sand-gravel layer, as<br />

shown in Fig.4. When the ground water is shallow.<br />

existence of a upper sand-gravel layer<br />

does not change the upward water supply at all,<br />

thus the HHR layer will appear in the lowest (iii)<br />

part of the frozen soil, as shown in Fig.2.<br />

MATHEMATICAL MODEL<br />

Besed <strong>on</strong> the unsaturated soil water movement,<br />

Zhang and Zhu (1983) have determined a numericalanalytical<br />

method for solving the coupled heat<br />

and moisture transfer equati<strong>on</strong>s. Using this<br />

method, the heave distributi<strong>on</strong> of a silty loam<br />

under shallow and deep ground .water c<strong>on</strong>diti<strong>on</strong>s<br />

has been calculated and is shown in Fig.5. The<br />

Figure shows that heave distributi<strong>on</strong> differs’<br />

significantly according to different ground<br />

water c<strong>on</strong>diti<strong>on</strong>s, this pettern corresp<strong>on</strong>ds<br />

closely to the experimental results.<br />

(iv)<br />

types. When the ground water is shallowly<br />

seated, the heave distributi<strong>on</strong> is<br />

characterized by the high heave ratio<br />

layer occurred in the lower half of the<br />

frozen soil (Type B), When the local<br />

ground water is deeply seated and the<br />

soil. has a good drainage capability,<br />

the heave distributi<strong>on</strong> is characterized<br />

by the high heave ratio layer occurred<br />

in the upper half of the frozen soil<br />

(Type A), when the soil is heavy, the<br />

heave distributi<strong>on</strong> is characterized by<br />

the high heave ratio layer in the middle<br />

half of the frozen soil (Type C) or by<br />

heave being distributed with relative<br />

evenness (Type D). Am<strong>on</strong>g theee distributi<strong>on</strong><br />

types, Type A and Type B are most<br />

comm<strong>on</strong>ly occurred.<br />

When the upper soil i s replaced by sand<br />

and/or gravel, the high heave ratio<br />

layer will generally occur in the lower<br />

half o f the frozen layer (Type B). When<br />

the ground water is deeply seated, high<br />

heave ratio layer will occur directly<br />

below the sand-gravel layer in the top<br />

of the original soil material. When<br />

the ground water is shallowly aeated,<br />

high heave ratio layer will occur in<br />

the lower part of the frozen soi1,close<br />

to the ground water table.<br />

The heave ratio observed in the layer<br />

near the ground water table i s much<br />

greater when the high heave ratio layer<br />

is in the lower half of thesfrozen layer<br />

(Type B ) than when it is-in the upper<br />

half of the frozen layer (Type A).<br />

Heave ratio (8)<br />

0 IO 20 50 40 50<br />

ACKNOWLEDGEMENT<br />

The author would like to thank Fu Shining,Wang<br />

Zh<strong>on</strong>gjing, Wu Fuxie and Huang Janlan for their<br />

c<strong>on</strong>tributi<strong>on</strong>s to the testing and data processing.<br />

This work was supported by the Water C<strong>on</strong>servancy<br />

, .,. Department of Gansu Province.<br />

REFERENCES<br />

-<br />

,.<br />

Fig.5 Results of Heave Distributi<strong>on</strong> for<br />

a Silty Loam under Shallowly and Deeply<br />

Seated Ground Water, as Calculated According<br />

to Method Presented by Zhang<br />

and Zhu (1981)<br />

CONCLUSION<br />

Wang, X. (1980). A study <strong>on</strong> the freezing and<br />

heaving under different ground water depth<br />

and soil c<strong>on</strong>diti<strong>on</strong>s. J. of Glaciology and<br />

Cryopedology, Vo1.3, No.2.<br />

Zhu, Q. (1983). Frost heave characteristics of<br />

the c<strong>on</strong>crete canals and the measure of replacing<br />

soil in Gansu Province. Proceedings<br />

of 2nd Nati<strong>on</strong>al C<strong>on</strong>€. <strong>Permafrost</strong> (selecti<strong>on</strong>),<br />

Lanzhou.<br />

Zhang, S. and Zhu, Q. (1983). A study <strong>on</strong> the<br />

calculati<strong>on</strong> of frost heave. Proc. 4th Int.<br />

C<strong>on</strong>f. <strong>Permafrost</strong>, Fairbanks.<br />

(i) The result of this paper indicate that<br />

various types of the frost heave distributi<strong>on</strong><br />

may exist rather than <strong>on</strong>e<br />

single type.<br />

(ii) The heave distributi<strong>on</strong> observed at four<br />

field sites may be classified into four<br />

1199

TRIAXIAL COMPRESSIVE STRENGTH OF FROZEN SOILS<br />

UNDER CONSTANT STRAIN RATES<br />

Zhu, Yuanlinl and D.L. Carbd<br />

1Lanahou Institute of Glaciology and Geocryology, Academia Siniea, Lanzhou, China<br />

W.S. Army CRREL, Hanover, NH 03755, U.S.A.<br />

SYNOPSIS Triaxial compressive strength tests were c<strong>on</strong>ducted<br />

<strong>on</strong> remolded, saturated Fairbanks<br />

silt and Northwest sand taken from,Alaska under various c<strong>on</strong>stant strain rates ranging from<br />

5.27~10- to 9.84~10-~s" and c<strong>on</strong>fining pressures up to 3.43,MPa at -2'C. The average dry densities<br />

of the samples tested were 1.20 g/cm for silt and 1.52 g/cm for sand, respectively. It was found<br />

that within the range of c<strong>on</strong>fining pressure employed the maximum deviator stress, (CJ~-Q~),,,, for the<br />

silt did not vary with Ua, i.e., its angle of int,ernal fricti<strong>on</strong> 4-0 and its shear strength Tzcohesi<strong>on</strong><br />

C. For a given temperature and dry density, the value of C inc.reased with increasing strain<br />

rate. However, the maximum deviator stress for frozen sand increased srgnificantly with increasing<br />

0,; and the increase was not linear, indicating that at a given temperature and strain rate, the<br />

values of C and Q for frozen sand depended up<strong>on</strong> the range of normal stress (I. At the temperature<br />

tested and ~,=1.04~10-~s-~, the values of C and 4 for the sand varied as follows: C-1.62 MPa and<br />

d1=22.8' for 053.1 MPa, and Cs2.30 MPa and $=12.1' for Ok3.1 MPa. The test results also showed that<br />

the axial failure strain for silt was independent of a,, but varied with el. It changed abruptly<br />

at a strain rate of about 10-4-10-5~-1 , indicating that a transiti<strong>on</strong> of deformati<strong>on</strong> mode occured at<br />

this strain rate. Whereas, the failure strain for sand increased with increasing 03, The initial<br />

tangent modulus of frozen silt and sand seemed to decrease slightly with increasing hydrostatic<br />

pressure, presumably owing to the pressure-meltifig of ice. Significant dilati<strong>on</strong> at larger strains<br />

was observed for the sand samples, but not for the ailt samples.<br />

INTRODUCTION<br />

The design of stable underground structures in<br />

cold regi<strong>on</strong>s and artificially frozen-ground supporting<br />

structures requires the knowledge of<br />

strength and deformati<strong>on</strong> behaviour of frozen<br />

soils under the acti<strong>on</strong> of both c<strong>on</strong>fining (hydrostatic)<br />

pressure and vertical load, i.e., at<br />

a complex stress state. In the past two decades,<br />

therefore, more attenti<strong>on</strong> has been paid to the<br />

research <strong>on</strong> the stress-strain behaviour of frozen<br />

soils under triaxial stress. While many<br />

researchers have studied this subject from various<br />

aspects, detailed studies are still required<br />

to gain a better understanding of the<br />

'subject.<br />

The objective of this study was to investigate<br />

the effect of c<strong>on</strong>fining pressure and strain rate<br />

<strong>on</strong> the stress-strain behaviour of disturbed,<br />

frozen saturated Fairbank silt and Northwest<br />

sand, The testing temperature was -2'C. The<br />

average try densities of the samples,tested were<br />

1.20g/cm for the silt and 1.52 g/cm for the<br />

sand, and their corresp<strong>on</strong>ding water'c<strong>on</strong>tent were<br />

42.7% and 25-33, respectively. The desired c<strong>on</strong>fining<br />

pressures and cross-head speeds employed<br />

are shown in Table I.<br />

MATERIAL AND SPECIMEN PREPARATION<br />

Material<br />

The material used in this investigati<strong>on</strong> are a<br />

remolded Fairbanks Fox tunnel silt (FTS) and a<br />

remolded Northwest (Irvine) sand (NWS) taken<br />

from Alaska. The grain size distributi<strong>on</strong> curves<br />

and physical properties of the materials are<br />

shown in Fig.1 and Table 11.<br />

TABLE I<br />

C<strong>on</strong>fining Pressure and Croas-Head Speed Used<br />

Silt samples Sand samples<br />

C<strong>on</strong>f ining<br />

Pressure 0, 0.49, 0.98, 1.96 0, 0.98, 1.96, 3.43<br />

0Q"P)<br />

Cross-head<br />

speed 10, 1. 0.1, 0.01, 0.005 1<br />

Specimen preparati<strong>on</strong><br />

The samples tested were made by using a gang<br />

mold, machined from acrylic plastic, which has<br />

a capacity of forming 19 cylindrical specimens<br />

at <strong>on</strong>e time. The details of specimen preparati<strong>on</strong><br />

(including compacting, saturating, freezing and<br />

trimming) were described by the authors (1987).<br />

By using the dual source y-ray technique with<br />

the help of J. Ingersoll, it is known that the<br />

distributi<strong>on</strong> of density and moisture al<strong>on</strong>g the<br />

specimen lhngth was quite uniform.<br />

In order to prevent the pressurizing liquid per-<br />

1200

TABLE I1<br />

Physical Properties of the Materials Tested<br />

Plastic Liauid Plastic Specific Organic Specific<br />

I<br />

FTS 34.2 38.4 4.2 2.680 5.5 35.0<br />

I<br />

NWS<br />

- c<br />

2.710<br />

-<br />

TEST RESULTS<br />

The curves of deviator stress<br />

(U,-U,)<br />

VB axial<br />

strain (EI) for FTS and NUS under various 03<br />

and strain ratee (i ) are presented in Fig.2 ,<br />

and 3, respectively: ' As is comm<strong>on</strong>ly defined. '<br />

Grain rizc. mm<br />

Fig.1<br />

Grain Size Diatributi<strong>on</strong>.Curves<br />

meatihg into a specimen and ice subllmati<strong>on</strong><br />

during a test, each specimen was sealed with a<br />

piece of rubber membrane and steel end caps.<br />

The nominal size of the prepared specimens was<br />

70 mm in diameter by 152 mm l<strong>on</strong>g.<br />

TESTING PROCEDURE AND APPARATUS<br />

The triaxial c<strong>on</strong>stant cross-head speed compressi<strong>on</strong><br />

tests were c<strong>on</strong>ducted <strong>on</strong> a screw-driven<br />

universal testing machine in 8 cold room, which<br />

allowed specimens deforming under various c<strong>on</strong>stant<br />

cross-head.speeds. All specimens were<br />

tempered and pressurized at the desired temperature<br />

and c<strong>on</strong>fining pressure for at least 24<br />

hours before testing. The axial force acting<br />

<strong>on</strong> a specimen during the movement of cross-head<br />

was measured through a multi-range load cell<br />

with an accuracy of 0.5% of full scale. The deformati<strong>on</strong><br />

was measured with a DCDT (direct current<br />

displacement transducer), havLng a sensitiv-<br />

.ity of 2.5xlO-'mrn. The c<strong>on</strong>fining pressure,which<br />

was provided by a compressor and transmitted to<br />

the specimen through a 50% by weight glycerolwater<br />

soluti<strong>on</strong>, was measured with a PLC pressure<br />

transducer. The temperature of the working liquid<br />

in triaxial cell (taken as the temperature of<br />

specimen after reaching equilibrium) was measured<br />

with a thermistor positi<strong>on</strong>ed inside the<br />

cell. The measurements showed that the temperatures<br />

were held c<strong>on</strong>stant with a fluctuati<strong>on</strong> of<br />

less than i0.05'C. The volume change of a specimen<br />

during a test was measured with a volumetric<br />

tube.<br />

I<br />

I<br />

0 10 20 30<br />

I<br />

&.X<br />

n, = p.RRMPa<br />

I I<br />

0 10 20 30<br />

%. %<br />

Fig.2 Curves of Deviatoric Stress vs<br />

Axial Strain for FTS<br />

the peak of the (Ol-ua) vs El<br />

curves is defined<br />

as the failure of the specimens, so that the<br />

deviator stress corresp<strong>on</strong>ding to the peak is<br />

defined as the deviatoric peak (maximum)strength<br />

(O~-U~)~, and the axial strain and elapsed time<br />

at ( ~ ~ -represent 0 ~ ) ~ the strain at failure<br />

(Elm) and the time to failure (tm), respectively.<br />

The test results of (u,-u,)~. ~ , m , t and initial<br />

tangent modulus Ei, together wftf test c<strong>on</strong>diti<strong>on</strong>a,<br />

E~ and a,, are summarized in Table 111.<br />

1201

TABLE 111<br />

Summary of the Test Results and C<strong>on</strong>diti<strong>on</strong>s<br />

Applied C<strong>on</strong>fining Maximum Axial Time to Initial<br />

Sample strai pressure, deviator strain at failure, tangent<br />

number rate , E, 63 stress, failure, t, modulus,<br />

F243<br />

F242<br />

F244<br />

F227<br />

F228<br />

F236<br />

F230<br />

F237<br />

F229<br />

F235<br />

F233<br />

F232<br />

F234<br />

F231<br />

F239<br />

m a<br />

F241<br />

F240<br />

Fairbanks Silt<br />

0 2.79<br />

0<br />

0<br />

1.71<br />

0.97<br />

0.49. 2.75<br />

0.49 1.64<br />

0.49<br />

0.49<br />

1.15<br />

1.06<br />

0.49 0.97<br />

0.49<br />

0.98<br />

0.94<br />

2.67<br />

0.98 1.70<br />

0.98 1.18<br />

0.98 0.95<br />

0.98<br />

1.96<br />

0.94<br />

2.84<br />

1.96 1.66<br />

1.96 1.19<br />

1.96 0.94<br />

10.33<br />

10.38<br />

3 .a4<br />

9.37<br />

9,40<br />

3.67<br />

3.43<br />

4.07<br />

4.00<br />

10.43<br />

10.75<br />

3.77<br />

3.43<br />

3.31<br />

10.37<br />

10.61<br />

3.03<br />

4.09<br />

1.75<br />

16.2<br />

620<br />

1.67<br />

15.0<br />

60.5<br />

111<br />

638<br />

1084<br />

1.80<br />

17.2<br />

60.9<br />

520<br />

1047<br />

1.85<br />

16.32<br />

50.5<br />

668<br />

430<br />

580<br />

530<br />

500<br />

500<br />

380<br />

440<br />

410<br />

350<br />

560<br />

480<br />

560<br />

390<br />

390<br />

480<br />

460<br />

480<br />

380<br />

Northwest Sand<br />

~250 1.02~10-* 0 4.84 3.48 5.67 980<br />

N247 1.04x10-" 0.98 6.09 10.67 17.2 960<br />

N245 1.04x10-' , 1.96 6.76<br />

N246 1.04~10"' 1.96 6.59<br />

N249 1.05~10-~ 3.43 7.41<br />

11.36 18.2 940<br />

13.70 22.0 920<br />

12.96 20.5 790<br />

DISCUSSION<br />

Fig.3 Curves<br />

Axial Strain<br />

e. 0"<br />

of Deviatoric Stress vs<br />

for NWS<br />

Effect of c<strong>on</strong>fininn pressure <strong>on</strong> the stressstrain<br />

behaviour of frozen soils<br />

It is seen from Fig.2 that all of the deviatoric<br />

stress-strain curves for a certain strain rate<br />

and various C J ~ are quite similar. It means that<br />

c<strong>on</strong>fining pressure does not significantly affect<br />

the deviatoric stress-strain behaviour of frozen<br />

silt. All of these curves have a wide "plateau",<br />

indicating that the silt samples behaved as a<br />

typical ductile (plastic) failure mode under<br />

various u,, i.e., the samples underwent plastic<br />

flow after a small quasi-elastic strain (

Deviatoric peak strength<br />

A plot of the reciprical of deviatoric peak<br />

strength, l /(u~-Ua)~, vs strain rate in semilogarithm,<br />

under various for FTS is shown in<br />

Fig.4. It is clear from this figure that the<br />

where tA=llO min is a reference time-to-failure<br />

corresp<strong>on</strong>ding to the deflecti<strong>on</strong> point of the<br />

curve in Fig.5. O"-1.02 MPa is the peak strength<br />

for t,=tA , and c1 is the slope of the curve in<br />

Fig.5 and has a value of 0.23 when tmbtA and<br />

0.04 when tm2tA.<br />

Q u.49<br />

Fig.4 Plot<br />

for FTS<br />

of l/(u1-U3),,, v8 log E l<br />

variati<strong>on</strong> of (U1-Ua)m with il for the silt does<br />

not depend up<strong>on</strong> og. Thus, the peak strength,<br />

(ol-09)m. as a functi<strong>on</strong> of strain rate, for<br />

frozen silt under various oar can be described<br />

by the following equati<strong>on</strong> which is similar to<br />

the uniaxial compressive strength equati<strong>on</strong> presented<br />

by the authors (1984):<br />

where &: =2.6~10-'s-'is a reference strain rate<br />

corresp<strong>on</strong>ding to the deflecti<strong>on</strong> point of the<br />

curve in Fig.4, u '=0.98 MPa is the deviatoric<br />

peak strength for kl-k'l, and B is the reciprical<br />

of the slope of In i, v8 l/(ul -0 ) curve and<br />

has a valre of 9.1 MPa when Slk:6; mand 28.8 MPa<br />

when 6 1 SE r'.<br />

From Fig.4 the deviatoric peak strength as a<br />

functi<strong>on</strong> of strain rate for the silt can be<br />

also described by the following expressi<strong>on</strong> which<br />

is similar to Vialov's strength-loss equati<strong>on</strong>:<br />

Fig.5 Log-log Plot of ( u1-u3 ), vs t,<br />

for FTS<br />

Shear strength<br />

The Mohr-circles and envelopes for FTS under<br />

various strain rates were plotted in Fig.6, in<br />

which the tensile Mohr-circles were plotted<br />

based <strong>on</strong> the authors' tensi<strong>on</strong> test data (1986).<br />

Explicitly, the angles of internal fricti<strong>on</strong>, $,<br />

for the silt within the range of c<strong>on</strong>fining pressure<br />

employed under various strain rates are all<br />

equal to zero. Thus. the Coulomb equati<strong>on</strong> for<br />

1. MPa<br />

6, =9.55x IO'S"'<br />

4<br />

where parameter B has a value of 2.5~10-2s"<br />

when & ~2.6xlO-~s-' and 1O'a-l when Elf12.6~<br />

lodes-<br />

1 . Note that the independent variable in<br />

eq.(2) is strain rate, but not the time-to-€ailure<br />

as is in Vialov's equati<strong>on</strong>.<br />

The deviatoric peak strength as a, functi<strong>on</strong> of<br />

time to failure, tm, €or FTS under various 03<br />

was plotted in Fig.5 in logarithm. It is explicit<br />

that the variati<strong>on</strong> of the peak strength,<br />

(ol-Oa),, with time to failure €or the silt is<br />

not dependent up<strong>on</strong> u9 and can be evaluated by a<br />

power-law expressi<strong>on</strong>:<br />

Fig.6<br />

Mohr-circles and Rnvelopea for FTS<br />

1203

frozen silt is reduced to<br />

i.e., the shear strength (T) for frozen silt<br />

equals to its cohesi<strong>on</strong> (C), which is equal to a<br />

half of the maximum deviator stress.<br />

Similar results were reported by Chamberlain<br />

(1972) <strong>on</strong> a glacial till at -1O'C. Ouvry (1985)<br />

reported that the maximum deviatoric stress for<br />

frozen clay even decreased slightly with increasing<br />

c<strong>on</strong>fining pressure at various temperatures<br />

and strain rates. This is due to the fact<br />

that the pressure-melting of ice in frozen soils<br />

increases the thickness of unfrozen water film<br />

around soil particles, and thus decreases their<br />

interparticle fricti<strong>on</strong> and cohesi<strong>on</strong>.<br />

For a given temperature the cohesi<strong>on</strong> (C) of a<br />

soil varies with strain rate. The values of C<br />

for FTS at -2'C under various strain rates were<br />

given in Table IV.<br />

TABLE IV<br />

Values of Cohesi<strong>on</strong> C for ITS at.-2'C<br />

as follows: C=1.62 MPa and 4-22.8' when OS3.l<br />

MPa, and C-2.30 MPa and ,$=12.3' when 023.1 MPa.<br />

The latter value of 9 is very close to the value<br />

(,$=12.4') obtained by Parameswaran et al. (1981)<br />

<strong>on</strong> frozen medium sand under similar strain rate.<br />

Based <strong>on</strong> the geometric relati<strong>on</strong> of Mohr-cfrcles<br />

and their comm<strong>on</strong> tangent, the values of C and<br />

9 can be also determined analytically (thus,<br />

more accurately) in terms of the following relati<strong>on</strong>s<br />

(Tereaghi and Peck, 1968):<br />

where parameters a and tga can be determined<br />

from the data shown in Fig.8 by linear regressi<strong>on</strong><br />

analysis. The values of C and ,$ for NWS<br />

obtained from the test data in terms of eq.(6)<br />

and (7) are as follows: Cm1.61 MPa and ,$=22.6'<br />

when 0350.98 MPa and C-2.26 MPa and 4-12.2"<br />

when U9ZO.98 MPa. They are very close to those<br />

obtained graphically from Flg.7.<br />

E l(8-l)<br />

9.55~10-~ 1.04~10"~ 1 .O~X~O-~ 1 .05x10a<br />

56<br />

I<br />

I<br />

C(MPa) 1.39 0.84 0.59 0.48<br />

The Mohr-circles and envelope for NWS B at<br />

4 = 1.04 Y IO4S<br />

strain rate of 1.04~10-~s-~ were plotted in - 1-<br />

Fig.7, in which the tensile strength data were<br />

from Bayer (unpublished). Obviously, the shear<br />

strength of Erozen sand can be evaluated by the 0 1 2 3 4 6 8 7 8<br />

.general form of Coulomb equati<strong>on</strong>: (Q + q ) m 2,MPa<br />

However, it is seen from Fig.7 that the envelope<br />

is not a straight line, but a'broken-line within<br />

a certain range of normal pressure, U. Therefore.<br />

the values of C and ,$ in eq.(5) is dependent<br />

up<strong>on</strong> the range of normal pressure for a<br />

given temperature and strain rate. The values<br />

of C and ,$obtained graphically from Fig.7 are<br />

a MPa<br />

Fig.7 Mohr-circLesandEnvelope for NWS<br />

Axial strain at failure<br />

The variati<strong>on</strong> of axial strain at failure (Elm)<br />

with strain rate for FTS under various Us was<br />

shown in Fig.9. An abrupt change of the failure<br />

strain with strain rate for the silt was observed<br />

occuring at a atrain rate between and<br />

Whereas, the failure strains rgmain<br />

almost the same for both ~,>lO-'a" and El<<br />

10-5s-1. with the averaged values of 10.2% for<br />

the former and 3.7% for the latter. This might<br />

imply that a transiti<strong>on</strong> of the mode of defromati<strong>on</strong><br />

for the silt occured at this strain rate.<br />

A similar phenomena for sand was observed by<br />

Baker et al. (1981) at B strain rate of 3x<br />

10-4 -1<br />

S .<br />

Fig.10 shows the failure strain as a functi<strong>on</strong><br />

of ug for both NWS and FTS at a strain rate of<br />

1.04~10-~s-~. It is seen that the failure<br />

strain for silt is independent of Og, but it increases<br />

with increasing 0 3 for sand (especially<br />

at lower c<strong>on</strong>fining pressures), accounting for<br />

1204

I_ NWS<br />

Fig.11 Initial Tangent Modulus vs<br />

Strain Rate in Logarithim €or FTS<br />

Fig.9 Variati<strong>on</strong> of Axial Strain at<br />

Failure with Strain Rate for FTS<br />

I<br />

0,. MPm<br />

Fig.10 Axial Strain at Failure vs<br />

C<strong>on</strong>fining Pressure<br />

Fig.12 Initial Tangent Modulus vs<br />

C<strong>on</strong>fining Pressure<br />

the increase in interparticle fricti<strong>on</strong> of coarsegrained<br />

soil under the effect of c<strong>on</strong>fining pressure.<br />

Initial tanRent modulus<br />

The variati<strong>on</strong> of initial tangent modulus (Ei)<br />

with strain rate for FTS under various 43 waa<br />

illustrated in Fig.11. 1tis.exgIicit that the<br />

initial tangent modulus for the silt does not<br />

vary with strain rate at the test c<strong>on</strong>diti<strong>on</strong>s.<br />

It has an average value of 460 MPa at the test<br />

temperature (-2'C).<br />

Fig.12 shows the variati<strong>on</strong> of Ei with US for<br />

both NWS and FTS. I't is seen from this figure<br />

that the initial tangent modulus for the medium<br />

sand is about twice as great as that for the<br />

silt at the given temperature and strain rate,<br />

The initial tangent moduli for both sand and<br />

silt decrease slightly with increasing c<strong>on</strong>fining<br />

pressure, owing to the pressure-melting of Ice<br />

in frozen samples.<br />

Volumetric strain<br />

The volumetric strain (AvV/vo) VE axial strain<br />

curves for both NWS and FTS are plotted in Fig.<br />

13. As was expected, the coarser grained NWS<br />

underwent remarkable dilati<strong>on</strong> as observed by<br />

Chamberlain et al. (1972) for Ottawa banding<br />

sand under high c<strong>on</strong>fining pressures. A small<br />

amount of volume decrease (IAv/vol

CONCLUSIONS<br />

It can be c<strong>on</strong>cluded from this investigati<strong>on</strong><br />

C<strong>on</strong>fining pressure does not affect the<br />

deviatoric stress-strain curves for<br />

frozen silt, but significantly increases<br />

the plasticity and strain hardening<br />

of frozen sand within the range<br />

of c<strong>on</strong>fining pressure employed.<br />

The angle of internal fricti<strong>on</strong> (b) is<br />

equal to zero for frozen silt: it varies<br />

with the range of u3 for frozen medium<br />

sand: 2122.6" when ~~$0.98 MPa and<br />

4-12.2 when 0~S0.98 MPa.<br />

A sudden change of the axial strain at<br />

failure with strain rate was observed<br />

occurin at a strain rate between lo-'<br />

and 10-'s- I for frozen silt at -2"C,<br />

indicating that a transiti<strong>on</strong> of the mode<br />

of deformati<strong>on</strong> and/or failure may occur<br />

at this strain rate.<br />

The axial strain at peak stress does<br />

not depend up<strong>on</strong> c<strong>on</strong>fining pressure for<br />

frozen silt, but increases with increasing<br />

c<strong>on</strong>fining pressure for frozen<br />

sand, especially at low c<strong>on</strong>fining pressure.<br />

The initial tangent modulus of frozen<br />

soil is not dependent up<strong>on</strong> strain rate,<br />

but slightly decreases with increasing<br />

c<strong>on</strong>fining pressure because of the<br />

pres~ure-melting of ice. It has an<br />

average value of 460 MPa for silt and<br />

960 MPa for medium sand at -2°C.<br />

Remarkable dilati<strong>on</strong> in triaxial compressi<strong>on</strong><br />

was observed for the coarser<br />

grained soil, but almost no volume<br />

changes were measured €or the finer<br />

grained soil.<br />

teats <strong>on</strong> frozen sand, Proceedings<br />

Fourth Canadian <strong>Permafrost</strong> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>,<br />

p. 387-393..<br />

Bayer,J., Investigati<strong>on</strong> into compressi<strong>on</strong> and<br />

tensile strength of frozen sand and silt,<br />

USA CRREL Technical Note (unpublished).<br />

Chamberlain, E.J., Groves, C. & Perham. R.<br />

(1972), The mechanical behaviour of frozen<br />

earth materials under high pressure triaxial<br />

test c<strong>on</strong>diti<strong>on</strong>s, Geotechnique. "01.<br />

22, No.3, p.469-483.<br />

Ourvy, J.F. (1985), Results of triaxial compressi<strong>on</strong><br />

tests and triaxial creep tests<br />

<strong>on</strong> an artificially frozen stiff clay,<br />

Proceedings of the 4th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> symposium<br />

<strong>on</strong> Ground Freezing, Vol.11, p.207-<br />

212.<br />

Parameswaran, V.R. & J<strong>on</strong>es, S.J. (19al), Triaxial<br />

testing of frozen sand, Journal of<br />

Glaciology, Vo1.27, No.95, p.147-156.<br />

Sayles, F.H. (1974), Triaxial c<strong>on</strong>atant strain<br />

rate tests and triaxial creep tests <strong>on</strong><br />

frozen Ottawa sand, USA CRREL Technical<br />

Report 253.<br />

Zhu, Y.L. & Carbee, D.L. (1984). Uniaxial compressive<br />

strength of frozen silt under<br />

c<strong>on</strong>stant deformati<strong>on</strong> rates, Cold Regi<strong>on</strong>s<br />

Science and Technology. 9(1984), 3-15.<br />

Zhu, Y.L. & Carbee, D.L. (L986), Tensile<br />

strength of frozen silt, Journal of Glaciology<br />

and Geocryology. Vo1.8, No.1, P.<br />

15-28,<br />

Zhu, Y.L. & Carbee, D.L. (1987), Creep and<br />

strength behaviour of frozen silt in<br />

uniaxial compressi<strong>on</strong>, USA CRREL Report<br />

87-10.<br />

of<br />

ACKNOWLEDGEMENTS<br />

This study was sp<strong>on</strong>sored by the U.S.Army Corps<br />

of Engineers at the Cold Regi<strong>on</strong>s <strong>Research</strong> t5<br />

Engineering Laboratory. The authors wish to<br />

express their appreciati<strong>on</strong> and thanks for the<br />

technical advice and instructive discussi<strong>on</strong><br />

from Dr. A. Assur, Messrs W. Quinn. E, Chamberlain,<br />

F. Saylea, D. Cole, Dr. M. Mellor and Dr.<br />

Y.C. Yen. We also would like to thank Msssrs<br />

J. Bayer, J. Rajkowski, J. Ingeraoll and G.<br />

Durell for their technical support and instrumentati<strong>on</strong><br />

assistance, Thanks are also given to<br />

Dr. T.H.W. Baker for review of this paper.<br />

REFERENCES<br />

Andersland, O.B. I% Alnouri, I. (1970), Timedependent<br />

strength behaviour of frozen<br />

soils. Jnl Soil Mech. Fdns Div. Am. SOC.<br />

Civ. Engrs 96, SM4, 1249-1265.<br />

Baker, T.H.W., J<strong>on</strong>es, S,J. & Parameswaran, V.R.<br />

(1981), C<strong>on</strong>fined and unc<strong>on</strong>fined compressi<strong>on</strong><br />

1205 b

LONG TERM SETTLEMENT TEST (3 YEARS)<br />

FOR CONCRETE PILES IN PERMAFROST<br />

B.A. Bredesenl, 0. Puschmannl and 0. Gregersenz<br />

ISelmer-Furuholmen Anlegg a.s, Oslo, Norway<br />

2Norwegian Geotechnical Institute, Oslo, Norway<br />

SYNOPSIS. Prefabricated c<strong>on</strong>crete piles in drilled holes have been used for founaati<strong>on</strong>s for heavy<br />

c<strong>on</strong>crete buildings at Svalbard. The pile bearing capacity calculati<strong>on</strong>s were based <strong>on</strong> North-American<br />

experience. The test was carried out in order to gain own experience in local soil c<strong>on</strong>diti<strong>on</strong>s. The,<br />

test site in L<strong>on</strong>gyarbyen was chosen close to future building aites where we anticipated poor ground'<br />

c<strong>on</strong>diti<strong>on</strong>e. See Fig. 2.<br />

We also wanted to test the performance of cast-in-glace reinforced c<strong>on</strong>crete piles. The testad castin-place<br />

pile with anti freeze agents and 15% shorter length had the eamm settlemente as the prefabricated<br />

grouted pilee and they can be recommended for future c<strong>on</strong>structi<strong>on</strong> projects.<br />

The objective was to establish the load settlement curve for l<strong>on</strong>g term loads for that specific Soil<br />

and the prevailing permafrost temperatures. The settlements are compared against curves of settlements<br />

in ice and ice rich silty sails fiom Nix<strong>on</strong> and McRoberts. See Fig. 12.<br />

The l<strong>on</strong>g term settlement for 40 t load, was 0.5 mm per year (12.5 cm in 25 yeare).<br />

SOIL CONDITIONS<br />

The aoil c<strong>on</strong>diti<strong>on</strong>s at the test site are shown<br />

<strong>on</strong> Fig. 3. The top layer which c<strong>on</strong>sists of sand<br />

and gravel, has a varying thickness over the<br />

area. The investigati<strong>on</strong>s showed a variati<strong>on</strong><br />

fram 2.5 m to 6.0 m. Underneath, to a depth of<br />

more than 10 m. the soil c<strong>on</strong>sists of a sediment<br />

of silt and clay. The amount of fines is gradually<br />

increasing with depth. High water c<strong>on</strong>tent<br />

indicates z<strong>on</strong>es of Ice rich material. The<br />

salinity is low, from 0.8 to 1.6 grams/litre,<br />

i.e. the sedimentati<strong>on</strong> took place in brackish<br />

water.<br />

TEST PROCEDURE<br />

We wanted, to the greatest extent, to duplicate<br />

the pile installati<strong>on</strong>s of the c<strong>on</strong>structed '<br />

builclinge at L<strong>on</strong>gyarbyen. These are without<br />

frost heave protecti<strong>on</strong>.<br />

The frost acti<strong>on</strong> in the active layer has<br />

influence <strong>on</strong> the performance of the pilea.<br />

However, because of the stability of the test<br />

structure <strong>on</strong>ly <strong>on</strong>e of the test piles was given<br />

froat heave protecti<strong>on</strong> to a depth of 100 cm.<br />

1206

SAND<br />

with gravel<br />

SILT<br />

clayey<br />

sandy<br />

CLAY<br />

silty<br />

sandy<br />

Fig. 3 Soil profila at test site<br />

The teat was performed in full scale. The 3<br />

piles were podti<strong>on</strong>ed in a triangle 600 cm<br />

apart. 3a8 Fig. 4.<br />

Three holes with diamet8r 35 cm were drilled,<br />

using an air track with downhole drill. Two<br />

prefabricated piles, Hercules H420. 7 and 10 m<br />

l<strong>on</strong>g, were installed using cement-send grout.<br />

The third pile was a cast-in-place reinforced<br />

c<strong>on</strong>crete pile, 6 m l<strong>on</strong>g. The c<strong>on</strong>crete mix wae<br />

spacial c<strong>on</strong>crete with anti freeze agents.<br />

(Reec<strong>on</strong> N<strong>on</strong>set 400). See Blgs 6 and 7 .<br />

0.9<br />

0.8<br />

0.9<br />

1.0<br />

1.6<br />

1.0<br />

1.5<br />

1.1<br />

1.1<br />

1.3<br />

a<br />

The drilling took place 83-10-21 and 83-10-28.<br />

The piles were grouted 87-11-07 at +16*C. A<br />

c<strong>on</strong>crete slab <strong>on</strong> top of the 3 piles was cast and<br />

was loaded with gravel after 10 weeks 84-01-19.<br />

To avoid end bearing, piles 1 and 3 were<br />

installed with a cushi<strong>on</strong> of styrofoam, Pile 2<br />

was installed with a load cell to register end<br />

4.<br />

bearing .<br />

The test was run 3 years using 40 t load per<br />

pile and 1 year using 60 t load. However, for<br />

60 t load the test structure got a aidesway<br />

making the settlement measurements impossible.<br />

MEASUREMENTS<br />

The reference pile for settlement measurements<br />

was c<strong>on</strong>structsd using a prefabricated c<strong>on</strong>crete<br />

pile with a special protecti<strong>on</strong> in the active<br />

layer. d8 Fig. 6.<br />

The settlements were read using Wild N3 precisi<strong>on</strong><br />

niveller from two sidts of each pile and<br />

with 12 readings for each settlement number.<br />

The two measurements were d<strong>on</strong>e from 2 different<br />

instrument positi<strong>on</strong>s (see Fig. 4 ), and they<br />

corresp<strong>on</strong>ded very well. The measuring accuracy<br />

is within 0.04 mm.<br />

The temperature maasurements were read using<br />

thermocouples with digital termameter Jenway tc<br />

2000 type 8015 and copper/c<strong>on</strong>stantan wire.<br />

The first 2 years settlements and temperatures<br />

were recorded 4 times a year.<br />

STAOL 1. LOA8 407 PER. PILL<br />

STAOE 2. LOAD IOT PER. PILE<br />

PREClllON<br />

NIVCLLER<br />

SECTION<br />

REFERENCE PILE -/<br />

- PLAN<br />

Fig. 4 Pile loading syatam<br />

1207

PILE 1<br />

(PREFAB.)<br />

PILE 2<br />

(PREFAB.)<br />

P-ILE 3<br />

(CAST - IN - PLACE)<br />

Fig. 6<br />

View of tested piles<br />

1983 - FREEZE-BACK<br />

STAFF FOR<br />

PRECISE<br />

LEVELLING<br />

PREFAB. PILE<br />

The piles were installed 1 November 1983 at air<br />

temperature +16OC. The ground temperatures<br />

during freeze-back is shown in Big. 8, and the<br />

positi<strong>on</strong> of the thermocouples is shown <strong>on</strong><br />

Fig. 7. The cast-in-glace c<strong>on</strong>crete (Rssc<strong>on</strong> N<strong>on</strong>set<br />

400) cures at freezing temperatures. A<br />

laboratory teat after f days at +50 to +B0C in a<br />

freezer gave cube eompreerai<strong>on</strong> values 27 MPa for<br />

the c<strong>on</strong>crete. For cast-in-place piles with air<br />

temperature +16DC, the curing of the c<strong>on</strong>crete<br />

above ground will govern the time for loading<br />

the piles. The heat from the curing did not<br />

seem to effect the freeze-back time much. Both<br />

types of piles could have been loaded after 3<br />

weeks at that time of the year. The loading was<br />

applied after 10 weiks.<br />

Fig. 6 Reference pile<br />

PIPE OW. 360"<br />

" OREASE INSIDE<br />

WITH<br />

1984 - LONG TERM SETTLEMENT INCLUSIVE<br />

COMPRESSION OF THE PILE<br />

C<strong>on</strong>crete is a compressible material and the<br />

first year the settlement of the piles in the<br />

permafrost was partly caused by the elastic and<br />

permanent compressi<strong>on</strong> of the c<strong>on</strong>crete pile. The<br />

total pile cap settlement of 2.1 mm per year is<br />

1208

BbWE 018mm.<br />

REINFORCING<br />

CONCRETE C46<br />

CONCRETE C46<br />

PREFAB. CONCRETE<br />

PILE 1 AND 2<br />

CAST - IN - PLACE CONCRETE<br />

PILE 3<br />

Fig. 7 Cross secti<strong>on</strong> af tested piles<br />

I PIKFAU. WE 1 A M 2<br />

-7 \<br />

MONTHLY MEAN ANI TEMPERATIMES<br />

Fig. 8 Freeze-back temperatures at 4 m depth<br />

Fig. 9 Temperature observati<strong>on</strong>s<br />

partly caused by compressi<strong>on</strong> of the pile<br />

material as the load gradually is transferred<br />

from the ground surface to the permafrost al<strong>on</strong>g<br />

the pile. St takes time for the forces to be<br />

transferred down to the bottom of the pile and<br />

the bottom of the pile may <strong>on</strong>ly be partially<br />

loaded. See Fig. 11,<br />

I<br />

I<br />

THE THERMOCOUPLES ARE PLACED 60 MU<br />

FROM THE FACE OF THE DRILLED HOLE<br />

(SEE FIR. 7 )<br />

Fig. 10 Temperature observati<strong>on</strong>s 1984<br />

The first da+ the 40 t load is applied, the<br />

compressi<strong>on</strong> acts <strong>on</strong>ly <strong>on</strong> the upper meters of the<br />

pile. The modulus of elasticity compares well<br />

with the measured 1 day compressi<strong>on</strong> values (Fig.<br />

11) 23 September 1986.<br />

The compressi<strong>on</strong> of the pile itself is reduced as<br />

time pass and <strong>on</strong>e would expect decrease in<br />

settlement for the lata m<strong>on</strong>ths of 1984.<br />

However, this trend is counterbalanced by<br />

increased settlement due to increasing thaw<br />

depth.<br />

1209

40T LOAD<br />

1<br />

60T LOAD<br />

7.11 19.1 3.4 3.7 7.11 16.1<br />

I I I<br />

1HM<br />

r: I" I<br />

.<br />

/ /<br />

y,,,<br />

12Y 16.1 I 23.9 I<br />

-.. -<br />

', \ , PILL z<br />

I<br />

PROTECTION<br />

2"<br />

THAWING DEPTH t7H<br />

FROST HEAVE FDRCE<br />

FROST MAW FORCE<br />

LESS THAN COT<br />

3 ' PLE 1 PLE 2 PILE<br />

Fig. 11<br />

Pile cap settlements<br />

NlXON AND McROBERTS<br />

1<br />

FIG. 9. Review of pile load test data T = -1 *C to -2.5 'C (1 psi = 6.9 kNh4 1 in./ycar =<br />

2.54 cm/year).<br />

Fig. 12 Diagram from Nix<strong>on</strong> and McRoberts (see reference list) Supplemented with test data from<br />

t<strong>on</strong>gyarbyen<br />

1210 I

1985 - FROST HEAVE<br />

The c<strong>on</strong>crete in the piles do not transfer tensi<strong>on</strong><br />

so <strong>on</strong>ly the rTinforcing bars must transfer<br />

the frost heave force in excess of the 40 t<br />

load. That is the reas<strong>on</strong> why the settlement<br />

curve has a humpback the winter 1985, See Fig,.<br />

11 *<br />

The fall temperatures of 1984 was extremely high<br />

(see Fig. 9) and resulted in temperatures at<br />

+l.tiOC at 4 m depth during freeze up and thawing<br />

to 2.5 m depth. The frost heave force must have<br />

been in excess wf 40 t acting <strong>on</strong> the 35 cm<br />

diameter pile and 250 cm length. Pile no. 3 had<br />

insulati<strong>on</strong> <strong>on</strong> length 100 cm and have more reinforcing<br />

steel and therefore got less frost<br />

heave.<br />

1986 - LONG TERM SETTLEMENT<br />

The summer/fall temperatures of 1985 was normal<br />

and resulted in a frost heave force less than<br />

40 t. The settlement curve for 1986 with 0.5 mm<br />

per year therefore depicts the l<strong>on</strong>g term settlement<br />

with maximum thaw depth of approximately<br />

1.5 m. This totals 12.6 cm in 25 years. See<br />

Fig. 11.<br />

EVALWATION OF TEST DATA<br />

1.<br />

2.<br />

3.<br />

4.<br />

9.<br />

For 40 t load and mean pile shaft stress<br />

0.06 MPa the l<strong>on</strong>g term settlement for pilea<br />

600 cm l<strong>on</strong>g ie 0.6 mm per year (1986). Then<br />

the frost heave forces are not acting <strong>on</strong> the<br />

piles. The mean ternpetature at depth 4 m is<br />

i4.5oC over that time. Sea Fig. 10.<br />

The ground is an ice poor silt, and for comparis<strong>on</strong><br />

the settlement data is plotted into<br />

the curves from Nix<strong>on</strong> and McRoberts for ice<br />

rich silt in Fig. 12.<br />

The cast-in-place pile is slightly better<br />

than the slurried piles. The cast-in-place<br />

pile and the slurried piles have the same<br />

settlement rate when the cast-in-place pile<br />

has 15% less surface area.<br />

The first year the pile cap settlement was<br />

2.1 mm without frost hcave influence. This<br />

includes elastic and permanent compressi<strong>on</strong><br />

of the c<strong>on</strong>crete pile itself.<br />

The increase of pile length from 675 cm to<br />

1006 cm did not reduce the settlement rate.<br />

The reas<strong>on</strong> moat likely is that because the<br />

c<strong>on</strong>crete is highly compressible the bottom<br />

of the l<strong>on</strong>g pile is <strong>on</strong>ly partially loaded.<br />

On the other hand the prefabricated pile is<br />

partially eccentric in the hole and the<br />

quality of the grouting could be less effective<br />

an l<strong>on</strong>g piles.<br />

The settlement curve has been affected by<br />

frost jacking. The calculated frost heave<br />

force is 54 t. Calculated adfreeze b<strong>on</strong>d<br />

atresses is 0.16-0.20 MFa.<br />

The calculated average adfreeze b<strong>on</strong>d stress<br />

during frost heave is higher for the castin-place<br />

pile (0.20 MPa) than for the<br />

slurried prefabricated piles (0.16 MPa).<br />

This indicates better quality for this<br />

cuncrete with anti freeze agents.<br />

Frost heave protecti<strong>on</strong> should be c<strong>on</strong>sidered<br />

for building purposes to avoid differential<br />

settlement. The protectian could be wrapped<br />

around the pile to break the adfreeze b<strong>on</strong>d<br />

or the ground surface could be insulated to<br />

reduce the thawing depth.<br />

6. The use of cast-in-place piles can be recommended.<br />

The cast-in-place pile and the<br />

slurried prefabricated piles had very sinilar<br />

settlement characteristics. The mix<br />

design for the c<strong>on</strong>crete with anti freeze<br />

agents (Rcsc<strong>on</strong> N<strong>on</strong>set 400) and the slurry<br />

design were sufficient to transfer the forces.<br />

The same slurry mix is used €or previous<br />

pile installati<strong>on</strong>s at L<strong>on</strong>gyarbyen.<br />

The use of cast-in-place piles is preferable<br />

to withstand lateral forces applied above<br />

ground because the column above ground then<br />

can have the same cross secti<strong>on</strong> as the<br />

drilled hole. Cast-in-place piles can also<br />

be heavily reinforced for lateral forces.<br />

7. The slurry mixture cement, filler, sand<br />

4:2:10 used for the prefabricated piles did<br />

transfer the forces very well. 23 September<br />

1986 the piles were given additi<strong>on</strong>al loading<br />

af 20 t, resulting in approximately equal<br />

elastic deformati<strong>on</strong> 0.4 mm for all piles.<br />

The thawed depth then was approximately<br />

150 cm. The time between measurements was<br />

24 hours.<br />

8. For 60 t loading the test rigg got a<br />

sidesway so the measurements had to be terminated.<br />

Tht maximum thawing depth then was<br />

1.50 m. For 40 t loading and maximum<br />

thawing depth 2,50 m the test rigg was<br />

stable.<br />

9. End bearing for Pile 2 was not readable for<br />

this small settlements.<br />

REFERENCES<br />

Crory. F.E. (1982). Piling in Frozen Ground.<br />

American Society of Civil Engineers.<br />

Proceedings, Vol. 108, No. TC1, pp. 112-124.<br />

Ellingbe, 0. and J.A. Finstad (1976).<br />

Peler i permafrost. Hovedoppgave. Norges<br />

tekniske hegskole. lnstitutt for geoteknikk<br />

og fundamenteringslare. 2 vols.<br />

Ladanyi, B. (1980). Field Tests of Foundati<strong>on</strong>s<br />

in Permakrost. Litterature review. Report<br />

prepared for Nati<strong>on</strong>al <strong>Research</strong> Council.<br />

Canada.<br />

Nix<strong>on</strong>, J.F. and E.C. McRoberts (1975). A<br />

design approach for pile foundati<strong>on</strong>s in<br />

permafrost. Canadian Geotechnical Journal,<br />

Val. 13, No. 1, pp. 40-57.<br />

Phukan, A. (1985). Frozen Ground Engineering.<br />

Prentice-Hall, Englewood Cliffs, N.J. 3368.<br />

121 1

TANGENTIAL FROST HEAVING FORCE ON REINFORCED<br />

CONCRETE PILES OF HIGHWAY BRIDGE<br />

Dai, Buimin and Tian, Deting<br />

Instituti<strong>on</strong> for Heil<strong>on</strong>giiang Provincial Highway and Transportati<strong>on</strong> <strong>Research</strong>, Harbin, China<br />

SYXOI'S I S Experiments and their results <strong>on</strong> tangential frost heaving force for the reinforced<br />

~.tlnt.~-t~tr pi Lcs ui highway bridges, the c<strong>on</strong>diti<strong>on</strong>s and parameters of stabilizati<strong>on</strong> <strong>on</strong> anti-heaving,<br />

~ n t l thc Int~thud and corresp<strong>on</strong>ding cucffici.ents to emend the standard frost depth of soils are chief.ly<br />

d c s c 1- i h c ti .<br />

I N II~OI~L'CTIOA' EXPERIMENTS ON TANGENTIAL FROST FORCES<br />

HEA<br />

Frost. f-ailurcs have been rgidcly existed in In-situ Tests<br />

bridses and culvcrt engineerings in the northern There are 28 piles for mechanical testing in<br />

reyicrns, China. ttith the investigati<strong>on</strong>s <strong>on</strong> some total, five of them have a diameter of 25 cm,<br />

rcinforced c<strong>on</strong>crete piles, we found there were and three-d37 cm, two-d50 cm, tw0-d75 cm,<br />

more than forty rnet.ers of beam bridges within thirteen-d80cm,two-dlOO<br />

cm, and <strong>on</strong>e- d 125 cm, resapproximate<br />

1000 meters being subjected to the<br />

pectively.<br />

frost f,lilures in varying degrees (Photo 1 and<br />

1). Xormal transportati<strong>on</strong>, as a c<strong>on</strong>sequence,<br />

Fully restrained steel frame against reversed<br />

has been influenced and so heavy losses have<br />

compressi<strong>on</strong> were used here, in which there are<br />

transverse girders, anchor piles, test piles<br />

and mechanical testing apparatus.<br />

The results are shown in Table I.<br />

TABLE I<br />

beerr suffered. For this reas<strong>on</strong>, it has been<br />

determined to be <strong>on</strong>e of the primar! research<br />

itcms sincc 1981. Experiments have been made<br />

intensively uti the magnitude of Tangential<br />

Frost Heaving Forces; Parameters and 'lethod of<br />

the Checki 11s Calculati<strong>on</strong> <strong>on</strong> Anti-heaving stahilizati<strong>on</strong><br />

in the Pile Foundati<strong>on</strong> Designs;<br />

Yethod ~ n Cul-resp<strong>on</strong>ding d<br />

Coefficients to Emend<br />

5tandord Frost. Depths for J veat-s. And these<br />

rcsults have been passed b!- the technical apprrllscll,<br />

\

TABLE 1.1<br />

Results From.Mode1 Tests<br />

-<br />

Geometric scales Total tangential frost Maximum unit tangential Average unit tangential<br />

heavingforce,KN frost heaving force,kpa frost heaving force,kpa<br />

1:2 26.3 381 84<br />

1:4 4.0 430 SO<br />

1: 10 1.06 66 32<br />

Wide slabs,two-6 m spans:<br />

doubledm c<strong>on</strong>crete piles<br />

d-80 cm. L8.8 m<br />

Clay the at depth of No 179<br />

Wide slabs, two-6 m spans;<br />

double-olum c<strong>on</strong>crete piles,<br />

d=70 cm, X=6rn<br />

Silty sand at 0-7 m;<br />

mid-sand at 7-9 m;<br />

stiff clay at 9-16 m<br />

Yes<br />

>lo8<br />

Wide slabs, three-6 m spans;<br />

double-column c<strong>on</strong>crete piles,<br />

d=70 cm, X=14 m<br />

ditto<br />

No<br />

Laboratory model tests<br />

The model tests were performed with three geometric<br />

scales, i.e., 1:2; 1:4; and 1:lO. Table I1<br />

indicates the results.<br />

Rating calculati<strong>on</strong>s to frost heaving bridge piles<br />

According to static equilibrium, the rating calculati<strong>on</strong>s<br />

were made to some frost-heaving bridge<br />

piles as follows (Table 111).<br />

To sum up, an analytical curve of average unit<br />

tangential frost-heaving force vs. ratio of<br />

subsoil frost heave is c<strong>on</strong>structed (Fig*l).<br />

heaving force €or the reinforced c<strong>on</strong>crete piles<br />

are given, as shown in Table IV.<br />

For the purpose of being clear <strong>on</strong> the effect of<br />

pile diameter <strong>on</strong> the tangpntial frost heaving<br />

force, the field tests were completed under the<br />

same freezing c<strong>on</strong>diti<strong>on</strong>, However, there are<br />

very little influences of pile diameters <strong>on</strong> unit<br />

tangential frost-heaving forces, it can be seen<br />

in Table V.<br />

TABLE V<br />

Values of Unit Tangential Frost Heaving<br />

Force vs. Pile Diameter<br />

Diameter of testing 50 75 100 125<br />

piles, cm<br />

Unit tangential 66 frost 58 56 58<br />

heaving force, kpa<br />

ACTION OF TANGENTIAL FROST HEAVING FORCE ON PILE<br />

FOUNDATION<br />

When frost heave of whole bodies of piles occurs,<br />

i.e.,<br />

T > P t G t F (1)<br />

Fig.1 Unit tangential Frost-heaving Force as a<br />

Functi<strong>on</strong> of Ratio of Frost Heave<br />

.: Data from Qing-an; 0: from Wan-jia;<br />

X: from rating calculati<strong>on</strong>s; A : from<br />

L<strong>on</strong>g-feng Experimental site, Daqing (Institute<br />

for Heil<strong>on</strong>gjiang Low Temperature Architecture,<br />

1981)<br />

As c<strong>on</strong>sistent with Fig.1 and the five-grade<br />

classificati<strong>on</strong> which we have put forward for<br />

seas<strong>on</strong>al frost soil in highway bridge and culvert,<br />

suggested values of tangential frost-<br />

Pile's Being Pullen Apart<br />

A<br />

Where T is the total tangential frost heaving<br />

force, in KN; P is the dead load acting <strong>on</strong><br />

single pile, in KN; G is its own weight of pile<br />

body, in KN; and F is fricti<strong>on</strong> resistance of<br />

unfrozen-soils <strong>on</strong> piles. G1 is its own weignt<br />

of pile body above the separated positi<strong>on</strong>, at<br />

which a pile is pullen apart, in KN; F1 is the<br />

TABLE IV<br />

Magnitude of Unit Tangential Frost-heaving Force Proposed<br />

Classificati<strong>on</strong> N<strong>on</strong>-heaving Weak-heaving Medium-heaving Str<strong>on</strong>g-heaving Severe-heaving<br />

of soils soil soil soil soil<br />

Ratio of frost<br />

heave (X)<br />

0- I<br />

1-3.5 3.5-6<br />

6-1 3 13<br />

Unit tangential 0-1 5<br />

frost heaving<br />

force, kpa<br />

15-50 50-80<br />

80-160 160-240<br />

. . . . . -. -.<br />

Note: 1. For precast bridge pile with smooth surface it needs multiply by 0.8;<br />

2. Values in Table IV are the means under true frost penetrati<strong>on</strong>, so emendati<strong>on</strong> must be made<br />

while a standard frost depth is provided;<br />

3. Values within a particular range as above can be obtained through interpolati<strong>on</strong>.<br />

1214

fricti<strong>on</strong> resistance of the unfrozen soils above the practice.<br />

the separated positi<strong>on</strong>, in KN; A is th: secti<strong>on</strong>a1<br />

area of the separated secti<strong>on</strong>, in m ( the<br />

2. Chosing the different coefficients for the<br />

secti<strong>on</strong>al area of tensile reinforcement when checking calculati<strong>on</strong>s <strong>on</strong> frost-heaving bridge<br />

the reinforced c<strong>on</strong>crete is c<strong>on</strong>cerned); and R is piles, we are able to find out which coefficient<br />

the ultimate tensile strss of materials, in kpa. is mostly in accord with the practical situati<strong>on</strong><br />

of frost heave.<br />

CALCULATION ON ANTI-HEAVING STABILIZATION OF<br />

FILE FOUNDATION<br />

C<strong>on</strong>diti<strong>on</strong>s of the anti-heaving stabilizati<strong>on</strong><br />

Based <strong>on</strong> the analysis of tangential frost-heaving<br />

force <strong>on</strong> pile foundati<strong>on</strong> menti<strong>on</strong>ed above, the<br />

two basic c<strong>on</strong>diti<strong>on</strong>al equati<strong>on</strong>s (3) and (4)<br />

must be taken into c<strong>on</strong>siderati<strong>on</strong> simultaneously,<br />

and <strong>on</strong>ly so, the stabilizati<strong>on</strong> against frost<br />

heave would be assured for the reinforced c<strong>on</strong>crete<br />

piles inseas<strong>on</strong>al frost regi<strong>on</strong>s,<br />

P t G t F SK.T (3)<br />

a= K.T - P - GI - FL Io] (4)<br />

A<br />

Where K is the assurance coefficient of structure<br />

with the value of 1.2 for statically determinate<br />

structures, or 1.3 for statically indeterminate<br />

structures;o is the theoretical<br />

stress for a checked secti<strong>on</strong>, in kpa; and [(r]<br />

is the allowable stress of materials, in kpa.<br />

Determinati<strong>on</strong> of total tangential frost-heavinq<br />

force<br />

When the measured frost depth is available,<br />

then<br />

T Ta'U*Hp + T~*U'H~~ (5)<br />

From above, a formula is established to determine<br />

the fricti<strong>on</strong>al resistance of a frost-heaving<br />

pile,<br />

Where T~ is the ultimate fricti<strong>on</strong>al resistance<br />

of each soil layer under the freezing fr<strong>on</strong>t,<br />

acting against the sides of piles, in kpa; Li<br />

is the thickness o f each layer of soils, in m.<br />

Determinati<strong>on</strong> of the dead weight of the pile<br />

body<br />

The effects of the dead weight of the pile body<br />

have come to an end far before the test <strong>on</strong> its<br />

vertical supportability of a pile is proceeded<br />

with. In other words, the Ti value obtained from<br />

the tests, i.e., the so-called ultimate fricti<strong>on</strong>al<br />

resislance of soils around bored pile,<br />

provided by "The Standard Specificati<strong>on</strong>s of the<br />

Foundati<strong>on</strong> of Highway Bridge Operati<strong>on</strong>s and<br />

designs of People's Republic of China", much<br />

obviously, is totally resulted, from the external<br />

load (or test load), no effects from the dead<br />

weight of the pile body involved again. Hence,<br />

the entire weight of a pile should be taken into<br />

account during the calculati<strong>on</strong> <strong>on</strong> the fricti<strong>on</strong>al<br />

resistance against a frost-heaving pile (the<br />

floating volumetric weight used for the soil<br />

that lies both below the freezing fr<strong>on</strong>t and the<br />

level of under ground water).<br />

if not (and with the presumpti<strong>on</strong> of no ice EMENDATION OF STANDARD FROST DEPTH OF SOILS<br />

formed in river beds during winter), then<br />

T = Ta'U*Zo'Czo (6)<br />

From looking into the large amount of data collected<br />

and the test results <strong>on</strong> frost heave susceptibility<br />

for a varity of soils, it is indicated<br />

that there is such a fairly close relati<strong>on</strong>-<br />

Where -ra is unit tangential frost-heaving force<br />

ship between the frost depth and its own frost<br />

heave susceptibility. The frost depth gets smalof<br />

soils, in kpa; U is the circumferential ler with increases of its frost heave susceplength<br />

of a pile, in m; Hp is the measured frost tibility (see Fig.2)<br />

depth, in m; TI is the unit tangential frost-<br />

Based <strong>on</strong> the aforementi<strong>on</strong>ed and the further anaheaving<br />

force of ice, in kpa; Hpl is the thick- lyses, we c<strong>on</strong>sider it is reas<strong>on</strong>able and thereness<br />

of ice layer from field measurement, in m: fore permissible to put forward for the varia-<br />

Zo is the standard frost depth in a certain ti<strong>on</strong> of emending coefficients for standard frost<br />

regi<strong>on</strong>, in m, and CEO is a coefficient for<br />

depths against frost heave ratio as shown in<br />

emending standard frost depth.<br />

Fig.3.<br />

Determinati<strong>on</strong> of fricti<strong>on</strong> resistance for the Subsequently, according<br />

to such a linear envelopfrost<br />

heaving bridge piles ing relati<strong>on</strong>, the emending coefficients to stand-<br />

. ard frost depth can be determinated by theequa-<br />

In order to solve this problem, we have made ti<strong>on</strong>,<br />

quite a few experimental studies and analyses<br />

as follows :<br />

C, = 1 - Kd (8)<br />

1. We adopted some intermediate-and small-sized<br />

bridges in severe heaving soils, for which we Where Kd is frost heave ratio of subsoil in<br />

of cfllculated thcir depths pile embedment by<br />

decimal.<br />

means of the trial-and-error procedure with<br />

different coefficients, then we could find C<strong>on</strong>sidering the c<strong>on</strong>venience<br />

to practical applicawhich<br />

coefficient is the most c<strong>on</strong>formable to ti<strong>on</strong> of calculati<strong>on</strong> by the equati<strong>on</strong> (81, we sug-<br />

1215

TABLE VI<br />

Magnitude of Emending Coefficients to Standard Frost Depth<br />

Classificati<strong>on</strong> N<strong>on</strong>-heaving Weak-heaving Medium-heaving Str<strong>on</strong>g-heaving Severe-heaving<br />

of soils soil soil soil s<br />

Emending<br />

coefficient<br />

1 .o 0.95 0.9 0.85 0.75<br />

Ratio of frost heave. 0"<br />

gest the specific magnitude of emending coefficientsto<br />

standard frost depth (Table VI).<br />

CONCLUSION<br />

I<br />

Fig.2 Graph of Frost Depths as a Functi<strong>on</strong><br />

of Frost Heave Susceptibility:<br />

' - Clay; o - Fine sand;<br />

A -Coarse sandy soil, and<br />

a - Clay-gravel.<br />

(i)<br />

(ii)<br />

(iii)<br />

The unit tangential frost-heaving forces<br />

for the reinforced c<strong>on</strong>crete piles, were<br />

obtained from the in-situ testa <strong>on</strong> 28<br />

tested piles with different diameters,<br />

experienced for 3-5 years. Moreover,it<br />

has already got througn the supplement<br />

and proof by the rating calculati<strong>on</strong> to<br />

frost heaving bridges. Therefore, the<br />

results could be trustworthy.<br />

C<strong>on</strong>cerning the reinforced c<strong>on</strong>crete<br />

bridge piles built in the str<strong>on</strong>g and<br />

extra str<strong>on</strong>g frost heaving soils, the<br />

tangential frost heaving-forces are<br />

frequently their c<strong>on</strong>trol load. So checking<br />

calculati<strong>on</strong> <strong>on</strong> Anti-heaving heaving<br />

stability must be given in the process<br />

of designing, proceeding by means of the<br />

procedure with its formula and parameters<br />

set forth in this paper.<br />

The methods and coefficients for emendati<strong>on</strong><br />

to standard frost depth were also<br />

from a large amount of in-situ tests.<br />

Hence, it is quite certain for them to<br />

be used.<br />

REFERENCES<br />

X<br />

XY<br />

Fig.3 Variati<strong>on</strong> of Emending Coefficients with<br />

Frost Heave Susceptibility of Subsoil:<br />

o Data from Qing-an Experimental Field;<br />

X - From Kaiyuan Experimental Field,<br />

bel<strong>on</strong>ging to Instituti<strong>on</strong> for Lian-ning<br />

Provincial Water C<strong>on</strong>servancy (Wang Xirao,<br />

(1980).<br />

Instituti<strong>on</strong> for Heil<strong>on</strong>gjiang Low Temperature<br />

Architecture, etc.: "Deciding <strong>on</strong> the Magnitude<br />

of Tangential Frost Heaving Force in<br />

Design, (1981), p.1-5.<br />

Ministry of Communicati<strong>on</strong>s: "JTJ024-85, Standard<br />

Specificati<strong>on</strong>s of the Foundati<strong>on</strong> of Highway<br />

and Bridge Operati<strong>on</strong>s and Designs of the<br />

People's Republic of China", the People's<br />

Communicati<strong>on</strong> Press, (1985), p.63.<br />

Wang Xirao, (1980), Experimental Studies <strong>on</strong> the<br />

Freezing and Frost Heave Susceptibility<br />

' under Different Underground Water Level and<br />

Different Soils, in collecti<strong>on</strong>: "Journal of<br />

Glaciology and Geocryology", VoL.2, No,3,<br />

p. 40-45.<br />

1216

PERFORMANCE OF TWO EARTHFILL DAMS AT LUPIN, N.W.T.<br />

s. Dufourl and I. Wolubecz<br />

'Geoc<strong>on</strong> Inc. (Lavalin Inc.), Yellowknife, Northwest Territories, Canada (now with<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Development <strong>Research</strong> Centre, Ottawa, Ontario, Canada)<br />

*=<strong>on</strong> Inc., (Lavalin Inc.), Regina, Saskatchewan, Canada<br />

SYNOPSIS Several earthfill dams were c<strong>on</strong>structed to enclose a Watershed and form a mine tailings<br />

p<strong>on</strong>d in a cold permafrost area with relatively poor subsurface c<strong>on</strong>diti<strong>on</strong>s. Foundati<strong>on</strong> materials<br />

included frozen sands and fractured bedrock which would be difficult to seal should they thaw. The<br />

<strong>on</strong>ly c<strong>on</strong>structi<strong>on</strong> material available locally was a pervious sand. A frozen core dam with liner was<br />

designed to maintain the foundati<strong>on</strong> sands and Eractured bedrock frozen, and hence watertight. The<br />

frozen core and foundati<strong>on</strong> ensure that c<strong>on</strong>taminants do not escape from the p<strong>on</strong>d and that seepage<br />

pressures do not cause internal instability of the structure. While predicti<strong>on</strong>s of the ground<br />

thermal regime evoluti<strong>on</strong> showed that frozen c<strong>on</strong>diti<strong>on</strong>s would be maintained, very little published<br />

data was found to document the behaviour of frozen dams over cold psrmafrost.<br />

An extensive m<strong>on</strong>itoring programme was initiated shortly after the c<strong>on</strong>structi<strong>on</strong> of the earth dams to<br />

document the evoluti<strong>on</strong> of the thermal regime within the earthfill structures.<br />

This paper discusses the results o€ four years of m<strong>on</strong>itoring the thermal regime in the embankment<br />

and its foundati<strong>on</strong>s at two dam secti<strong>on</strong>s, each <strong>on</strong> different thermal c<strong>on</strong>diti<strong>on</strong>s. The first secti<strong>on</strong><br />

corresp<strong>on</strong>ds to the locati<strong>on</strong> of a 5 rn deep talik while the sec<strong>on</strong>d secti<strong>on</strong> is located over virgin cold<br />

permafrost.<br />

INTRODUCTION<br />

The Lupin Gold Mine is located <strong>on</strong> the west<br />

shore of C<strong>on</strong>twoyto Lake, Northwyt Territories,<br />

at about 65' 41' North, 111 12' West,<br />

or approximately 380 km northeast of Yellowknife<br />

and 1300 km north of Edm<strong>on</strong>t<strong>on</strong> (see<br />

Figure 1). The mine site is about 150 km<br />

north of the treeline in an area characterized<br />

by low relief, a poorly developed drainage<br />

pattern, numerous shallow lakes and cold<br />

permafrost.<br />

Several mill tailings and effluent retenti<strong>on</strong><br />

dams were built during the 1981 summer<br />

seas<strong>on</strong>. The mill complex was completed for<br />

the first gold bulli<strong>on</strong> to be cast in May 1982<br />

and impoundment started at that time.<br />

This paper discusses the thermal changes in<br />

two of the darns and their performance in<br />

general from c<strong>on</strong>structi<strong>on</strong> in 1981 to the Fall<br />

of 1987. The c<strong>on</strong>tinuous thermal m<strong>on</strong>itoring<br />

was possible because of the owner's interest<br />

in detailed m<strong>on</strong>itoring of the dams ana the<br />

assistance of the Government of Canada.<br />

1217<br />

BACKGROUND INFORMATION<br />

Geology and Geomorpholoa<br />

The C<strong>on</strong>twoyto Lake area lies within the TJpland<br />

unit of the Kazan physiographic regi<strong>on</strong> of the<br />

Canadian Shield. The area was glaciated<br />

during the Pleistocene Epoch and evidence of<br />

two ice movement periods are reported (Rlake,<br />

1963 and Tremblay, 1976). The thin overburden<br />

is predominantly a silty sand till occasi<strong>on</strong>ally<br />

overlain by glaciofluvial and glaciolacustrine<br />

sand and gravel deposits. Eskers and<br />

aband<strong>on</strong>ed beaches are comm<strong>on</strong> landforms but<br />

relatively impervious clays and silts do not<br />

occur near the Lupin Mine. Redrock bel<strong>on</strong>gs to<br />

the Yellowknife Supergroup of the Archean<br />

Epoch. The rock c<strong>on</strong>sists of a mixture of low<br />

grade metamorphosed argillite, siltst<strong>on</strong>e,

slate, greywacke and quartzite, generally<br />

phyllite (Tremblay, 1976).<br />

Relief at the site is generally low, 31evati<strong>on</strong>s<br />

in the project area range between 470<br />

and 505 m above mean sea level. The rolling<br />

ground surface is marked by numerous rock outcrops<br />

and block fields.<br />

The area has numerous shallow lakes and marshy<br />

depressi<strong>on</strong>s. The drainage pattern is disorganized<br />

and poorly defined but ultimately,<br />

streams lead to C<strong>on</strong>twoyto Lake.<br />

Climate<br />

The mean annual air temperature at C<strong>on</strong>twoyto<br />

Lake is -12.1”C. M<strong>on</strong>thly mean daily temperatures<br />

are shown <strong>on</strong> Figure 2. Freezing temperatures<br />

may OCCUP during any m<strong>on</strong>th of the<br />

year. On average, there are 280 days with<br />

frost (daily minimum temperature O’C or lower).<br />

The average €reezing and thawing indices<br />

are estimated as 5100 and 6RS0C-days, respec-<br />

Canada, 1975). The summer m<strong>on</strong>ths (mid-June to<br />

August) have the greatest precipitati<strong>on</strong> w-ith<br />

most rainfall in the €orm of a faint annoying<br />

mist (Tremblay, 1976).<br />

DESIGN<br />

Site Selecti<strong>on</strong><br />

The toxicity of the tailings e€fluent and the<br />

fragile northern envir<strong>on</strong>ment necessitated<br />

careful selecti<strong>on</strong> of the tailings disposal<br />

site. The tailings p<strong>on</strong>d was to be designed<br />

€or total impoundment oE tailings, mill<br />

effluent and precipitati<strong>on</strong>s (rain, runor€ and<br />

snow meltwater) during the first years of its<br />

life untiltreatment requirements would be<br />

established.<br />

The most suitable site €or a tailings p<strong>on</strong>d was<br />

found about 4.5 km from the plant. The 614 ha<br />

watershed was formed by damming the intermittent<br />

outlet of the basin at Dam 1A and five<br />

saddles which c<strong>on</strong>nected at various elevati<strong>on</strong>s<br />

with adjoining watersheds (see Figure 3 ).<br />

The tailings slurry is c<strong>on</strong>veyed from the plant<br />

by heat traced pipeline. The slurry is discharged<br />

in the northeast sector of the tailings<br />

area and solids are not expected to accumulate<br />

against the dams in the northwest and<br />

west sectors. Hence, good. quality water<br />

retaining dams are required. It should be<br />

noted that Internal Dam J, shown <strong>on</strong> Figure 3,<br />

was built in 1985 as a new water management<br />

plan was implemented.<br />

Dam Secti<strong>on</strong><br />

..<br />

A S 0 N D J F M A M J J<br />

M0NT-I OF YEAR<br />

FYGURE 2. MONIWLY MEAN DAILY ’E”’IURES.<br />

COhTWOYID LAKE. NWT<br />

The stratigraphy al<strong>on</strong>g the dam alignments<br />

basically c<strong>on</strong>sists of a thin organic layer, up<br />

to 45 cm thick, underlain by sandy till and<br />

bedrock. A typical log is shown <strong>on</strong> Figure 4.<br />

The till ranges in thickness from zero at rock<br />

outcrops to an estimated 7 m at valley bottoms.<br />

The till is a silty sand with gravel<br />

and c<strong>on</strong>tains occasi<strong>on</strong>al cobbles and boulders.<br />

tively. About the end of September, snow<br />

falls and ice forms <strong>on</strong> lakes. Normally, snow<br />

melts by the end of June except where it<br />

drifts, and ice break-up <strong>on</strong> C<strong>on</strong>twoyto Lake<br />

does not occur before the sec<strong>on</strong>d week of July.<br />

The freezing and thawing indices have averaged<br />

5094 and 821°C-days respectively during the<br />

period 1982 to 1987. Indices for each seas<strong>on</strong><br />

are :<br />

Year peeze Thaw<br />

hug I-JUl 31 C-days C-days<br />

81-82 4979 -<br />

82-83 5707 767<br />

83-84 4604 1049<br />

84-85 5293 800<br />

85-86 5190 702<br />

86-87 4788 788<br />

The mean yearly total precipitati<strong>on</strong> is 275 mrn<br />

half of which falls as snow (Znvir<strong>on</strong>ment<br />

1218

The coveredbedrock is generally competent<br />

phyllite with a frost-weathered (fractured)<br />

z<strong>on</strong>e extending 1.5 to 3 m deep.<br />

The silty sand dam foundati<strong>on</strong> and the thin<br />

overburden cover <strong>on</strong> fractured bedrock could<br />

pose substantial seepage and stability problems<br />

for a water-retaining dam <strong>on</strong> an unfrozen<br />

foundati<strong>on</strong>. In view of the cold permafrost<br />

regime, it was deemed that seepage could be<br />

mitigated with a frozen dam core and foundati<strong>on</strong>.<br />

The thermal aspects are discussed in<br />

the next subsecti<strong>on</strong>.<br />

Because of the short c<strong>on</strong>structi<strong>on</strong> seas<strong>on</strong> and<br />

to spread capital outlay, stage building of<br />

the dams was to be implemented. In 1981, the<br />

stage I dams were built to elevati<strong>on</strong> 485 m<br />

from selected and compacted thawed silty sand<br />

overburden with an impermeable liner <strong>on</strong> the<br />

upstream side (Figure 5). The valley floor<br />

was at approximately el. 478 and 480 m at Dams<br />

1A and 2 respectively. The liner was provided<br />

to stop seepage through the dams during the<br />

first few years until the foundati<strong>on</strong> permafrost<br />

aggraded into the dam core. The sec<strong>on</strong>d<br />

dam stage, to elevati<strong>on</strong> 486.5 m, was built in<br />

August 1984 with random borrow end-dumped from<br />

the crest <strong>on</strong> the downstream side. The two<br />

largest dams, 1A and 2, are about 8.5 and 6.5<br />

m high respectively at: the present. It is now<br />

planned'to maintain this c<strong>on</strong>figurati<strong>on</strong> €or the<br />

remainder of the projected mine life. Details<br />

of the c<strong>on</strong>structi<strong>on</strong> are described by Dufour et<br />

al. (1988).<br />

Thermal Aspects<br />

19-<br />

P<br />

PERFORMANCE<br />

B<br />

B<br />

I I<br />

The soil and rock are permanently frozen, The<br />

thickness of the active layer varies from 0.60<br />

m in thickly vegetated areas to about 2.5 m in<br />

barren areas. Few ice lenses were found in<br />

the frozen ground foundati<strong>on</strong> material. The<br />

largest ice layer observed was 80 nun thick:<br />

others were smaller than 25 m. The measured<br />

undisturbed mean annual ground temperature is<br />

about -9'C. At the time of c<strong>on</strong>structi<strong>on</strong>, thaw<br />

beneath the intermittent creek at Darn 1~ is<br />

believed to have reached through the overburden<br />

and fractured bedrock, to sound rock at<br />

a depth of 4 to 5 m. The initial ground temperatures<br />

of the talik were not measured. It<br />

is also estimated that in thermally undisturbed<br />

areas at all dams, perhaps 2 nl of the<br />

foundati<strong>on</strong> sand had thawed by the end of c<strong>on</strong>structi<strong>on</strong><br />

which included organics stripping.<br />

Case histories of low head water retaining<br />

structures <strong>on</strong> permafrost are scarce in the<br />

literature (Johnst<strong>on</strong>, 1969; Fulwilder, 1973:<br />

Roy et al., 1973: Biyanov, 1975). The <strong>on</strong>ly<br />

relevant case history is from the Crescent<br />

Lake Dam near Thule, Greenland (Fulwilder,<br />

1973) which ,shows a similar dam under similar<br />

climatic c<strong>on</strong>diti<strong>on</strong>s froze completely in two<br />

winters.<br />

The scarcity of applicable case histories and<br />

the importance of developing and maintaining a<br />

frozen core Led to the implementati<strong>on</strong> o€ a<br />

ground temperature m<strong>on</strong>itoring programme.<br />

General<br />

Mill tailings and effluent producti<strong>on</strong> began in<br />

May 1982. The water level fluctuati<strong>on</strong>s in the<br />

lower tailings p<strong>on</strong>d for the period May 1, 1982<br />

to December 1987 are shown <strong>on</strong> Figure 6. The<br />

peak in 1983 corresp<strong>on</strong>ds to spring runoff followed<br />

by summer evaporati<strong>on</strong>. During the summers<br />

of 1985 and 1986, water was siph<strong>on</strong>ed from<br />

the p<strong>on</strong>d over Dam 1A to be discharged in the<br />

envir<strong>on</strong>ment. The water quality was at acceptable<br />

standards for discharge to take place an3<br />

thus avoid raising the dams which were at<br />

minimum freeboard.<br />

Several sets of thermistor strings were installed<br />

in May 1982, April 1983, October 1983,<br />

April 1985 and August 1987 as described in<br />

Dufour et al. (1988). Current thermistors are<br />

installed to depths varying between 15 m and<br />

25 m at the two secti<strong>on</strong>s discussed below.<br />

Locati<strong>on</strong>s of the thermistor string's are shown<br />

.<strong>on</strong> Figures 3, 7 and 8. Two secti<strong>on</strong>s of interest<br />

were instrumented: Dam 2 which was huilt<br />

<strong>on</strong> virgin permafrost and the part of Dam 1A<br />

which was built over the basin outlet. In<br />

July 1982, the creek secti<strong>on</strong> of Dam 1A became<br />

important when seepage took place throuqh the<br />

talik, located beneath the creek, and apDeared<br />

<strong>on</strong> the downstream toe of the dam. Immediately,<br />

two l<strong>on</strong>g thick silty sand apr<strong>on</strong>s were<br />

placed <strong>on</strong> the upstream and downstream sides of<br />

the dam to lengthen the seepage path. It is<br />

believed, based up<strong>on</strong> piezometric observati<strong>on</strong>s<br />

during drilling, that most: of the seepage took<br />

place through the upper 2 m of bedrock which<br />

1219

P<br />

0<br />

N<br />

D<br />

E<br />

L<br />

V<br />

E L<br />

E L<br />

E<br />

V<br />

A<br />

T<br />

I<br />

0<br />

N<br />

(tu)<br />

NOTTOSCALE<br />

is highly fractured. It should be noted that<br />

both the upstream and downstream toes of Dam<br />

1A were kept clear of snow (which normally<br />

drifts to about 2 m deep) through the winters<br />

of 1983-84 and 1984-85.<br />

GROUND TEMPERATURE OBSERVATIONS<br />

- Dam 2<br />

The fill and the thawed top part of the foundati<strong>on</strong><br />

soils froze completely during the first<br />

winter. At mid-summer 1982, thermistors showed<br />

a dam core temperature of -1'C at elevati<strong>on</strong><br />

482.5 m. By the summer of 1987 the temperature<br />

at the same locati<strong>on</strong> was down to -3'C,<br />

see Figure 10.<br />

The evoluti<strong>on</strong> of the ground temperatures is<br />

shown <strong>on</strong> Figures 9a to 9c. The deep sensors<br />

beneath the core (strings D2-5 and 02-6) show<br />

a cooling trend since c<strong>on</strong>structi<strong>on</strong>, see Eigures<br />

9b ana 9c. Both the cold, permafrost<br />

regime and the level o€ water impoundment<br />

affect the ultimate steady-state ground temperature.<br />

The three comp<strong>on</strong>ents of Figure 9<br />

also show that seas<strong>on</strong>al variati<strong>on</strong>s are felt to<br />

a depth of about 18 m. This is significant in<br />

that dam fill temperatures (0 to 6 m deep)<br />

vary too much €OK making reliable year to year<br />

1220

comparis<strong>on</strong>s with <strong>on</strong>ly a €ew years data.<br />

entire thermal regime must be c<strong>on</strong>sidered.<br />

The<br />

The 1986 p<strong>on</strong>d drawdown and c<strong>on</strong>sequent withdrawal<br />

of the o<strong>on</strong>d away from the crest appears<br />

to have caused a 0.4'C temperature drop at 20<br />

m beneath the dam crest (elevati<strong>on</strong> 466 m), see<br />

Figure 9c.<br />

Figure 10 illustrates the isotherms during<br />

Uqust 1987. The critical part of the foundati<strong>on</strong><br />

beneath the core, the silty sand and<br />

fractured rock, is colder than -5°C and the<br />

dam core itself is clearly subject to great<br />

annual temperature variati<strong>on</strong>s. A natural late<br />

some 100 m downstream of the dam probably influences<br />

the positi<strong>on</strong> of the -4'C isotherm.<br />

A series o€ ground probing radar surveys calibrated<br />

<strong>on</strong> the thermistor strings indicated<br />

that all of Dam 2 and its foundati<strong>on</strong> are well<br />

frozen (Laflhche et al., 1988).<br />

Dam 1A - Creek Secti<strong>on</strong><br />

Figures lla to lld show the evoluti<strong>on</strong> of the<br />

ground temperatures at the secti<strong>on</strong> of Dam 1A<br />

located over the former talik. It is also<br />

useful to relate the underground patterns surveyed<br />

by ground probing radar to the thermistor<br />

results to understand the complex thermal<br />

regime (see radar survey results this c<strong>on</strong>ference<br />

in Laflbche et al., 1988).<br />

Rased <strong>on</strong> preliminary thermistor readings and<br />

seepage observati<strong>on</strong>s during the summer of<br />

1982, it is believed that the dam fill froze<br />

during the first winter (1982-83) but not the<br />

foundati<strong>on</strong> talik. Ground temperature readings<br />

taken in 1933 show that the foundati<strong>on</strong> was<br />

just below O'C at the top and just above O'c<br />

at bedrock (not illustrated herein).<br />

All curves <strong>on</strong> Figure 11 show a cooling trend,<br />

hence gradual freeze-back of the talik (8.5 to<br />

12.5 m deep at D1A-11 and -12; to about 6.5 m<br />

deep at DIA-~O). An excepti<strong>on</strong> is the 3.9 m<br />

deep sensor at D1A-10, the downstream toe,<br />

where a talik remnant remains. Heat €low<br />

trends indicate this remnant will eventually<br />

disappear. There is a marked decrease in<br />

ground temperature after the p<strong>on</strong>d water was<br />

drawn down in 198.5. At thermistor D1A-12,<br />

18 m beneath the crest, the ground temperature<br />

decreased from -1.5 to -2.2'C (Figure lld).<br />

It is interesting to note that the foundati<strong>on</strong><br />

beneath the dam crest did not have a large<br />

seas<strong>on</strong>al fluctuati<strong>on</strong> until 1985 (pre-1985 data<br />

not reported herein). This is attributed to<br />

the .unfrozen soil and bedrock reducing the<br />

depth of seas<strong>on</strong>al temperature Variati<strong>on</strong>8 and<br />

thus having a warming influence <strong>on</strong> the<br />

overlying soil. The depth of 'zero seas<strong>on</strong>al<br />

variati<strong>on</strong>s is about 18 m.<br />

The talik at the instrumented secti<strong>on</strong> Eroze<br />

hack during the winter of 1984-85, four years<br />

after c<strong>on</strong>structi<strong>on</strong>. There is little doubt<br />

that snow clearing at the dam toes played a<br />

large role in the raFid freeze-back of the<br />

talik. The lowering o€ the p<strong>on</strong>d instead of<br />

4<br />

- 3.9m ..... 1 7.m ---<br />

12.41~<br />

1221

the raising oE the dams was also timely and<br />

beneficial for freeze-back of the talik.<br />

The isotherms shown <strong>on</strong> Figure 12 illustrate<br />

the thermal regime as of September 1987. The<br />

dam fill is comfortably below O'C although<br />

within the depth of large seas<strong>on</strong>al variati<strong>on</strong>s.<br />

A bulb colder than -5'C extends from<br />

the downstream area into the central dam foundati<strong>on</strong><br />

where the talik used to be. Readings<br />

discussed above show this bulb is still expanding<br />

(cooling). The -3'C isotherm does not<br />

go far beneath the upstream shell which was<br />

influenced by the former talik and the relatively<br />

warm p<strong>on</strong>d water. The new thermistor<br />

string (~1~-15), added to the secti<strong>on</strong> in<br />

August 1987, shows the O'C isotherm is about 4<br />

m deep and the -1 'C isotherm some 10 m deep,<br />

The data suggests the freezing point in the<br />

p<strong>on</strong>d might be depressed at least to -0.3-C.<br />

CONCLUSIOPJS<br />

The results o€ the ground temperature m<strong>on</strong>itoring<br />

at the Lupin tailings dams show the feasibility<br />

of the frozen core c<strong>on</strong>cept for watertightness<br />

in a cold permafrost regime. By<br />

utilizing a frozen core, the c<strong>on</strong>structi<strong>on</strong> can<br />

be inexpensively carried out using local earth<br />

materials which would be permeable in the un-<br />

€rnzen state. The fill itself froze permanently<br />

in the first year even where a talik<br />

was present. The talik froze back in the<br />

fourth winter after c<strong>on</strong>structi<strong>on</strong> with the help<br />

of snow clearing. The unscheduled drawdown of<br />

the p<strong>on</strong>d the summer following the winter<br />

during which the talik froze back has also had<br />

a positive effect up<strong>on</strong> cooling of the dam<br />

foundati<strong>on</strong>.<br />

At Lupin the p<strong>on</strong>d water level has changed<br />

drastically in the first five years operati<strong>on</strong>s.<br />

When at minimum freeboard, the water<br />

was higher than the bottom of the active layer<br />

and the PVC liner helped to stop seepage. ~n<br />

the design of an unlined frozen core dm,<br />

great care must be taken to ensure that the<br />

impounded water level will not be higher than<br />

the active layer <strong>on</strong> the dam crest or its abutments.<br />

In additi<strong>on</strong> it should be noted that<br />

even intermittent creeks can have significant<br />

taliks beneath them. Taliks are preferred<br />

seepage paths and, under certain circumstances,<br />

could cause serious instabilty when<br />

not recognized and dealt with.<br />

The evaluati<strong>on</strong> of the thermal regime at any<br />

secti<strong>on</strong> requires deep thermistors and several<br />

years of data because of the larp depth of<br />

seas<strong>on</strong>al variati<strong>on</strong>s. It was shown that<br />

although frozen fill c<strong>on</strong>diti<strong>on</strong>s were achieved<br />

early and although shallow depth temperatures<br />

appear to be similar from year to year, a<br />

stable thermal reqlme was not reached six<br />

years after c<strong>on</strong>structi<strong>on</strong>. The many factors<br />

influencing the dams' thermal regime include:<br />

climate, snow cover and p<strong>on</strong>d level.. The snow<br />

was cleared during two winters to successfully<br />

assist freeze-back of the talik at Dam 1A. It<br />

is not believed snow removal will be required<br />

again. The timely drawdown of the p<strong>on</strong>d<br />

(carried out instead of dam raising) has<br />

allowed the dam and its foundati<strong>on</strong> to cool<br />

further.<br />

1222<br />

ACKNOWLEDGEMENT<br />

The authors wish to gtatefully acknowledge the<br />

cooperati<strong>on</strong> and aasistanoe of all Echo Bay<br />

Mines Ltd. envir<strong>on</strong>mental and corporate staff..<br />

This research was supported in part by c<strong>on</strong>tracts<br />

from the Nati<strong>on</strong>al <strong>Research</strong> Council of<br />

Canada and Energy, Mines and Resources<br />

Canada, Dr. Alan Judge of the Geological<br />

Survey of Canada is to be thanked for his<br />

support of the work.<br />

REFERENCES<br />

Biyanov, GF (1975). Dams <strong>on</strong> permafrost.<br />

234pp. U.S. Army, CRREL, Oraft Transl.<br />

TL 555.<br />

Blake, WJr. (1963). Notes <strong>on</strong> glacial geology,<br />

northeastern District of Mackenzie.<br />

12pp. Geol. Sur. of Canada, Paper 63-28.<br />

Dufour, SI Judge, AS, Lafl'eche, P ( 1988).<br />

Design and M<strong>on</strong>itoring of Earth<br />

Embankments over <strong>Permafrost</strong>. Proc. 2nd<br />

Int. C<strong>on</strong>€. <strong>on</strong> Case Hist. in Geotech.<br />

Eng., St-Louis, Miss., U.S.4.<br />

Envir<strong>on</strong>ment Canada, Atmospheric Envir<strong>on</strong>ment<br />

(1975). Canadian Normals, Temperature,<br />

1941-1970. Volume l-SI, 198pp. NO.<br />

U.S.C. 551-582 (711, Downsview, Ontario.<br />

Fulwilder, CW (1973). Thermal regime in an<br />

Arctic earthfill dam. Proc. 2nd Int.<br />

C<strong>on</strong>f. <strong>on</strong> Perm., Yakutsk, U.S.S.R., North<br />

Am. C<strong>on</strong>tributi<strong>on</strong>, U.S. Nati<strong>on</strong>al Academy<br />

of Sciences, 622-628.<br />

Johnst<strong>on</strong>, GH (1969). Dykes <strong>on</strong> permafrost,<br />

Uelsey Generating Stati<strong>on</strong>, Manitoba.<br />

Can. Geot. Jour. (61, 2, 129-157.<br />

Laflbche, PT,) Judge, AS, Pil<strong>on</strong>, JA (1988).<br />

The the'use of ground probing radar in<br />

the design and m<strong>on</strong>itoring of water<br />

retaining embankments in permafrost.<br />

This Proc. V Int, - C<strong>on</strong>f. <strong>on</strong> Perm.,<br />

Tr<strong>on</strong>dheim, Norway.<br />

Roy, MI Larochelle, PI Anctil, C (1973).<br />

Stability of dyke embankments at mining<br />

sites in the Yellowknife area. 78 pp.<br />

Dept. of Indian and Northern Affairs,<br />

Ottawa, Ontario, Canada. ALUR Rpt. 72-<br />

$73-31.<br />

Tremblay , LP ( 1976). Geology of northern<br />

C<strong>on</strong>twoyto Lake Area, Oistrict of<br />

Mackenzie. 56pp. EMR Canada, Geol.<br />

Sur. of Canada, Memoir 381.<br />

,I

ROADWAY EMBANKMENTS ON WARM PERMAFROST<br />

PROBLEMS AND REMEDIAL TREATMENTS<br />

D. Esch<br />

Alaska Department of Transportati<strong>on</strong> - <strong>Research</strong> Secti<strong>on</strong>, Fdrbankq Alaska, USA<br />

SYNOPSIS M<strong>on</strong>itoring studies <strong>on</strong> eight experimental road embankment secti<strong>on</strong>s c<strong>on</strong>structed <strong>on</strong> warm (0" to -1" C)<br />

permafrost .fn the interior of Alaska, have provided a basis for design-life performance predicti<strong>on</strong>s. Expertmental<br />

features evaluated have included insulati<strong>on</strong> and peat layers, toe berms, air c<strong>on</strong>vecti<strong>on</strong> cooling ducts, thermosyph<strong>on</strong>s,<br />

solar screens, and geofabric reinforcement. Thermal adjustments and surface movements of these embankments have<br />

c<strong>on</strong>tinued to occur over the full design llfe. It has been c<strong>on</strong>cluded that the majority of l<strong>on</strong>g-term embankment problems<br />

occur as a result of excessive net warming of the side-slopes. The greatest reducti<strong>on</strong>s in thawing and movements came<br />

from solar screens and snow c<strong>on</strong>trol sheds <strong>on</strong> the side-slopes.<br />

INTRODUCTION<br />

Road embankment performance studies <strong>on</strong> "warm" permafrost,<br />

defined as having an average temperature above -1' C were<br />

initiated near Glennallen, Alaska in 1954 when five<br />

highway cross-secti<strong>on</strong>s were instrumented to record<br />

surface and subsurface temperatures. Paving was first<br />

placed <strong>on</strong> the roadway at these sites in 1957 and observati<strong>on</strong>s<br />

c<strong>on</strong>tinued until 1960 (Greene et al. , 1960) The<br />

study at Richards<strong>on</strong> Highway Mile 130 dem<strong>on</strong>strated that in<br />

splte of the dark asphalt surface and the fact that<br />

average annual air temperatures were as high as -3" C,<br />

full annual refreezing was occurrSng beneath the paved<br />

roadway surfaces, and average roadway surface temperatures<br />

were similar to those at undisturbed permafrost<br />

sites. The primary thermal effect of the roadway surface<br />

was that of greatly increasing the seas<strong>on</strong>al variati<strong>on</strong>s in<br />

surface temperatures, which resulted in a much thicker<br />

active layer beneath the road. The active layer thickness<br />

at the study sites averaged 2.0 m beneath the gravel<br />

roadway surface and 3.1 m after the pavement was placed<br />

in 1957.<br />

The first North American installati<strong>on</strong> of subgrade insulati<strong>on</strong><br />

over warm permafrost, using extruded polystyrene<br />

foam, was c<strong>on</strong>structed near Chitina, Alaska in 1969 (Esch,<br />

1973). Temperature, settlement, and thaw depth m<strong>on</strong>itoring<br />

work has c<strong>on</strong>tinued at the Chitina site through 1987.<br />

The data have dem<strong>on</strong>strated that warming of the roadway<br />

slopes, caused by the combined effects of summertime<br />

heating of the exposed gravel , and the wintertime insulating<br />

snow cover, is the primary problem with both<br />

insulated and uninsulated embankments <strong>on</strong> warm permafrost.<br />

These observati<strong>on</strong>s have since been c<strong>on</strong>firmed at four<br />

other Interior Alaska sites, where additi<strong>on</strong>al records of<br />

roadway and slope surface temperatures have been made<br />

(Esch, 1983).<br />

In summary, the roadway side-slope surfaces have been<br />

found to generally become much warmer than either the<br />

travelled roadway surface or the adjacent undisturbed<br />

ground surfaces. In all cases studied in warm permafrost<br />

areas, the slope surfaces have averaged significantly<br />

warmer than 0" C and have warmed to average up to +5" C,<br />

As a result, progressively deeper annual thawing of the<br />

permafrost occurs and taliks develop beneath slope and<br />

ditch areas, causing slope area settlements and ultimately<br />

resulting in a loss of lateral and vertical support<br />

for the roadway itself (Esch, 1983; McHattie, 1983).<br />

1223<br />

Surface and<br />

Air Temperature Observati<strong>on</strong>s<br />

Highway pavement and side-slope mean annual surface<br />

temperatures, and freezing and thawing seas<strong>on</strong> n-factors<br />

measured at Interior Alaska sites <strong>on</strong> warm permafrost are<br />

summarized by Tables 1 and 2. As can be seen from these<br />

summaries, the average annual pavement surface temperatures<br />

have ranged from 3.1' to 4.4" C above the average<br />

air temperatures, while the embankment slope temperatures<br />

have averaged from 4.0" to 7.7" C warmer than the air.<br />

Annual alr temperatures. far most of the paved highway<br />

system in the Interior of Alaska are represented by two<br />

l<strong>on</strong>g-term recording sites located at the University of<br />

Alaska near Fairbanks and at Big Delta. located about 150<br />

km east of Fairbanks. Data for these sites from 1931<br />

through 1986 are shown by Figure 1, which indicates<br />

several multi-year periods of warmer than normal average<br />

air temperatures. Since pavement temperatures exceed<br />

average air temperatures by 3 to 4" C, there is the<br />

TABLE 1 - Road Surface and Slope Surface Annual<br />

Temperature Averages for sites in Interior Alaska.<br />

AnwlAveraw Terrperatures (C")<br />

site<br />

I<br />

Period & Roaky %E<br />

Chittna 1971-72 -4.5' -1.4' -0.6"<br />

Canyw, Creek 1975-77 -4.6' -1.1" t2.9"<br />

B<strong>on</strong>anza Cwk 1975-79 -2.7" M.5" "*<br />

II<br />

south Slop It<br />

"- 6.0"<br />

I1<br />

"- +1 I<br />

North Slope "<br />

go<br />

Peger Road 1982-83 -3.3" t1.1" *"<br />

TABLE 2 - Side-Slope n-Factors for Alaskan Sites.<br />

- Site<br />

Slope-Face<br />

Period & Height Bearing n-Freeze n-Thaw<br />

-<br />

Chitina N 1971-72 3:l 2.1 m S 30" W 0.70 1.33<br />

Cam Ck 1974-77 3:l 1.4 m S 45" W 0.39 1.37<br />

BoMnta Ck 1975-79 21. 7.0 m S 10" E 0.45 1.72<br />

south Slope<br />

Bawnza Ck 1975-79 2:l 7.0 nl N 10" W 0.40 1.02<br />

NDrth Slope

etain after thawing. Such soils wil drain, c<strong>on</strong>solidate,<br />

and compress after thawing. Thaw-stable (low<br />

moisture c<strong>on</strong>tent) permafrost. soils, by c<strong>on</strong>trast, wil<br />

compress and yield elastlcally after thawing, but do not<br />

generally present significant embankment stability<br />

problems. Gravels, sands and inorganic loessial silts<br />

are frequently found in a thaw-stable state, in Interior<br />

Alaska. Unfortunately, thaw-unstable permafrost<br />

c<strong>on</strong>diti<strong>on</strong>s occur more often than not, and some embankment<br />

instability must nearly always be antlcipated.<br />

Embankments <strong>on</strong> permafrost typically require corrective<br />

maintenance either because of excessive settlements of<br />

the top surface or because settlement movements of the<br />

side slopes result in lateral spreading and cracking of<br />

the embankment (Fig. 3).<br />

FIGURE 1. Interior Alaska maan annual air temperatures<br />

at Fafrbanks (UES) and Big Delta (After Juday, 1983).<br />

potential for average annual pavement temperatures to<br />

rise above 0" C. This would be expected to result in<br />

progressively deeper thawing and talik development<br />

beneath the pavement. Due to the elevated temperatures<br />

typical of roadway slopes, there is almost a certainty<br />

that average slope temperatures wil rise well above 0" C<br />

and that destructive annually deepening thawing wil<br />

always occur beneath the embankment slopes <strong>on</strong> warm<br />

permafrost.<br />

Five different thermal problems which can lead to embankment<br />

distress and failure should be c<strong>on</strong>sidered in embank'<br />

ment design work, as discussed in the following secti<strong>on</strong>s:<br />

Current forecasts of global warming trends expected as a<br />

result of the increasing atmospheric c<strong>on</strong>centrati<strong>on</strong> of<br />

carb<strong>on</strong>-dioxide and methane also should be c<strong>on</strong>sidered in<br />

the thermal design of embankments. Kellogg (1983) has<br />

summarized possible future global and arctic mean surface<br />

temperatures, as shown by Figure 2. These forecasts<br />

indicate a warming trend expected for the Arctic of<br />

roughly 1' C every 10 years. As most of Alaska falls<br />

into the sub-arctic climate z<strong>on</strong>e, a rise of 1" C every 10<br />

to 20 years appears possible and embankments whfch are<br />

presently thermally stable may not always remain so,<br />

Catlnrlrl Polar hqimr<br />

Massfve Subsurface<br />

Ice<br />

The worst situati<strong>on</strong> for thaw-instability of embankments<br />

results from the occurrence of massive near-surface ice<br />

deposits, since thawing of ice results in a total lack of<br />

support, Annual thaw-settlements must then be anticipated<br />

until either additi<strong>on</strong>al thermal resistance is added to<br />

the embankment or the ice has entirely melted away. A<br />

sec<strong>on</strong>d problem of embankments overlying ice is that the<br />

creep rate of ice under shear stress is much higher than<br />

that for frozen soil, and creep movements may lead to<br />

excessive settlements even if there is no thawing of the<br />

ice.<br />

Inadequate Thermal Resistance<br />

Surface settlements from permafrost thaw and c<strong>on</strong>solidati<strong>on</strong><br />

beneath a roadway can result from three different<br />

problems. The first and most obvious is that of inadequate<br />

thermal resistance to protect the underlying<br />

permafrost from the maximum annual thaw z<strong>on</strong>e. The<br />

predicti<strong>on</strong> of thaw depths beneath paved surfaces can be<br />

EMBANKMENT PROBLEMS<br />

d<strong>on</strong>e easily with acceptable accuracy by using the modified<br />

Berggren calculati<strong>on</strong> method, (Braley, 1984) as well<br />

As inferred by the previous discussi<strong>on</strong>s of air, roadway as by more elaborate methods. However, for the disc<strong>on</strong>surface,<br />

and side-slope temperature trends, various tinuous permafrost areas of Alaska, where seas<strong>on</strong>al<br />

problems must be anticipated in the design of embankments thawing indices are as high as 2000' C days, seas<strong>on</strong>al<br />

over thaw-unstable permafrost soils. The term "thaw-un- thaw depths exceeding 6 meters must be anticipated when<br />

stable" soils refers to permafrost soils with higher embankment materials are gravels with relatively low<br />

moisture c<strong>on</strong>tents in the frozen state than the soil can moisture c<strong>on</strong>tents. For<br />

1 I224<br />

more typical embankments c<strong>on</strong>-

structed with silty gravels over organic silt foundati<strong>on</strong><br />

soils, annual thaw depths fall within the range of<br />

2.5 to<br />

4.5 m. By using polystyrene foam insulati<strong>on</strong>, the annual<br />

thaw depth can be reduced to less than 2 m (Esch, 1973;<br />

1983).<br />

Heat Gains from Flowing Water<br />

Water flowing through the active layer beneath the<br />

embankment can cause thawing in excess of that expected<br />

from heat c<strong>on</strong>ducti<strong>on</strong> from the road surface. In practice,<br />

it is very difficult to design for the heat input of<br />

flowing water beneath an embankment. The designer would<br />

need to know the temperature, time, history, source,<br />

flowrate, and flow directi<strong>on</strong> of each water source, as<br />

well as the permeability of the embankment and foundati<strong>on</strong><br />

soils. Roadways are usually designed to avoid p<strong>on</strong>ding<br />

and l<strong>on</strong>gitudinal flows by providing drainage culverts<br />

through the embankment at appropriate locati<strong>on</strong>s. Bey<strong>on</strong>d<br />

these water c<strong>on</strong>trol efforts, embankment designers typically<br />

ignore the potential for heat gain from flowing<br />

water. Observati<strong>on</strong>s indicate to the author that c<strong>on</strong>cerns<br />

over thawing from temporarily p<strong>on</strong>ded or flowing water<br />

have been overstated in the past, and that this is<br />

generally a minor factor in+poor embankment performance.<br />

Net Surface Warming<br />

permafrost thaw. The embankment must taper to zero<br />

thickness at the toe of the slope and the sloped surfaces<br />

also typically result in increased solar heat gain <strong>on</strong> at<br />

least <strong>on</strong>e side of the fill. The embankment slopes also<br />

have a thickened snow cover due to drifting and to<br />

plowing from the road surface. Al of these factors<br />

combine to cause the slopes to become much warmer than a<br />

road surface which is maintained free of snow in winter.<br />

The typical embankment slope is inclined toward net<br />

warming and progressive thawing even if north-facing.<br />

Al embankment slopes m<strong>on</strong>itored in warm permafrost<br />

regi<strong>on</strong>s have dem<strong>on</strong>strated mean surface temperatures<br />

significantly warmer than 0" C, and have resulted in<br />

annually deepening thaw z<strong>on</strong>es and talik development. The<br />

results of thawing beneath the slopes are downward and<br />

outward slope movements and ultimately the lateral<br />

spreading and cracking failure of the roadway surface<br />

(Fig. 3). However, in spite of the almost universal<br />

thaw-progressi<strong>on</strong> and tali k development beneath the<br />

roadway slopes, roadway surface failure by spreading and<br />

l<strong>on</strong>gitudinal cracking is a maintenance problem <strong>on</strong> less<br />

than 20% of roadways <strong>on</strong> warm permafrost. The most<br />

thaw-unstable permafrost soils appear to result in the<br />

most severe spreading failures, but the critical soil<br />

c<strong>on</strong>diti<strong>on</strong>s have not yet been defined.<br />

REMEDIAL TREATMENTS<br />

In general, subsurface temperatures tend to average When faced with the multitude of potential embankment<br />

nearly the same as the overlying road surface whenever problems and failure mechanisms in warm disc<strong>on</strong>tinuous<br />

the active layer soil c<strong>on</strong>ductivities are reas<strong>on</strong>ably permafrost areas, the designer has several opti<strong>on</strong>s. The<br />

similar in the frozen and thawed states. Therefore, first (and most frequently used) is simply to admit that<br />

whenever surface temperatures average significantly excessive embankment movements and distress are going to<br />

higher than 0" C the annual thaw depth wil exceed the occur, and build a structurally adequate but thermally<br />

;nnual depth of refreezing. Residual thaw z<strong>on</strong>es or inadequate embankment; requiring the maintenance engineer<br />

tal iks" wil then develop beneath the roadway. After to repair the distress as it occurs. Structural adequacy<br />

this process starts, additi<strong>on</strong>al heat enters the ground for carrying maximum truck loadings wil require no more<br />

each year and causes additi<strong>on</strong>al thawing of the than 1 m of fill thickness. By frequent maintenance<br />

permafrost, and an unending annual cycle of thawing and patching and leveling, passable paved roadways can be<br />

roadway settling begins to occur.<br />

achieved under the worst permafrost c<strong>on</strong>diti<strong>on</strong>s. The most<br />

cost-effective approach for thermally inadequate road<br />

As stated previously, paved road surface temperatures in embankments may be to maintain a gravel-surfaced roadway<br />

Interior Alaska have averaged approximately 4 C warmer for a number of years following c<strong>on</strong>structi<strong>on</strong>. The<br />

than the mean annual air temperature. Mean annual air routine regrading required to remove potholes and<br />

temperatures in this regi<strong>on</strong> typically range from -1" to corrugati<strong>on</strong>s also serves to level sags and to fill cracks<br />

-5" C, resulting in pavement surfaces which average very as they occur. Gravel surfaces also typically result in<br />

close to, or slightly above 0" C. A series of unusually slightly decreased annual thaw depths as compared to<br />

warm years such as occurred between 1976 and 1981 (Fig. paved surfaces, reducing the magnitude of annual settle-<br />

2) would therefore be expected to result in tal ik devel-<br />

ments. However, the maintenance costs required for<br />

opment and progressive settlement of many of the roadway higher traffic levels and speeds frequently mandate an<br />

secti<strong>on</strong>s c<strong>on</strong>structed over permafrost. Observati<strong>on</strong>s of asphalt paved surface and require the design engineer to<br />

instrumented roadway secti<strong>on</strong>s during this period have c<strong>on</strong>sider a number of alternatives for minimizing roadway<br />

shown net warming and talik development at some sites and distress from thaw-unstable permafrost foundati<strong>on</strong>s, Ten<br />

not at others. If the climate of the Arctic warms by different remedial treatments which have been used and<br />

several degrees as predicted over the next half century,<br />

evaluated by the Alaska Department of Transportati<strong>on</strong> are<br />

then progressive tali k development and roadway settlement<br />

discussed below:<br />

distress must be anticipated throughout the Interior<br />

Alaska. Some minor changes in average surface tempera- Subgrade Insulati<strong>on</strong><br />

ture can be achieved by using light-colored aggregates or<br />

white painted surfaces, but generally the designer must<br />

In 1969, the first expanded polystyrene plastic foam<br />

design for the surface albedo of the available paving insulated roadway over permafrost in North America was<br />

aggregates.<br />

c<strong>on</strong>structed at a site near Chitina, Alaska (Esch, 1973).<br />

The first insulated airfield was also c<strong>on</strong>structed in 1969<br />

at Kottebue, Alaska. Since that time six additi<strong>on</strong>al<br />

Side-Slope Warming<br />

highways, totaling 2.94 km, and four airfield runway<br />

secti<strong>on</strong>s have been similarly insulated, These secti<strong>on</strong>s<br />

The final problem to c<strong>on</strong>fr<strong>on</strong>t the designer is that of have generally performed quite well, with full annual<br />

excessive warming of the embankment side-slopes, The<br />

refreezing beneath the paved surfaces even though the<br />

c<strong>on</strong>sequences of removing the natural surface vegetati<strong>on</strong><br />

underlying permafrost temperatures are as high as -0.3" C<br />

mat and thereby causing accelerated thawing of the<br />

(Esch, 1986). However, insulati<strong>on</strong> has not c<strong>on</strong>trolled<br />

underlying permafrost have been widely reported. The<br />

progressive permafrost thawing beneath the side-slopes at<br />

placement of a thin gravel embankment <strong>on</strong> top of the<br />

any site, and some lateral spreading and cracking has<br />

organic mat wil result in the same effect by compresoccurred<br />

in the shoulder areas at some of these sites.<br />

si<strong>on</strong>, thereby altering the summertime thermal balance,<br />

reducing evapo-transpirati<strong>on</strong> cooling, and accelerating<br />

1225

Peat Underlays<br />

In 1973, a 90 m length of roadway, located in a<br />

permafrost cut secti<strong>on</strong> southeast of Fairbanks <strong>on</strong> the<br />

Richards<strong>on</strong> Highway, was c<strong>on</strong>structed using a 1.2 to 1.5 m<br />

thick layer of peat as a thermal underlayer (McHattie,<br />

1983). Peat is of particular value as a thermal protecti<strong>on</strong><br />

layer over permafrost because its frozen c<strong>on</strong>ductivi-<br />

'ty may be twice its thawed c<strong>on</strong>ductivity. As a result,<br />

peat acts to increase heat flow out of the ground during<br />

freezing and to reduce heat flow into the ground during<br />

the thawing seas<strong>on</strong>. The net results of peat's c<strong>on</strong>ductivity<br />

change and its high latent heat are to reduce the<br />

thaw depth and to cause the mean annual temperature of<br />

the underlying permafrost to be significantly lower than<br />

that of the overlying road surface.<br />

At the study site the peat showed a significant benefit<br />

in causing net l<strong>on</strong>g-term heat removal, and in preventing<br />

talik development beneath the roadway. A similar adjacent<br />

roadway secti<strong>on</strong> c<strong>on</strong>structed without peat resulted in<br />

net warming and talik development (Fig. 4), accompanied<br />

by progressive settlement of the road surface. Beneath<br />

the side-slope and ditch areas, however, the peat<br />

underlayer was of no significant thermal benefit, and<br />

talik development has been progressive and rapid (Fig,<br />

4). Site data indicate that temperatures at the underlying<br />

permafrost surface have been lowered by approximately<br />

0.5' C by the peat placement.<br />

This study has served to dem<strong>on</strong>strate the thermal advantages<br />

of both artificially placed and naturally occurring<br />

peat layers beneath embankments. The benefits of the<br />

Peat are maximized when it is located high in the active<br />

layer and as near to the surface as practical. However,<br />

roadway strength c<strong>on</strong>siderati<strong>on</strong>s generally require that<br />

peat layers be covered by at least <strong>on</strong>e meter of fill<br />

thickness because of the low elastic modulus of this<br />

material.<br />

Embankment Berms<br />

Soil berms, placed to protect the lower embankment slopes<br />

from accelerated thawing, have been extensively used and<br />

investigated in Alaska. These berms are typically<br />

c<strong>on</strong>structed of silty soils which result in a reduced<br />

seas<strong>on</strong>al thaw depth as compared to gravels. The performance<br />

of 1.8 m thick berms at Parks Highway sites near<br />

Fairbanks has been reported by (Esch, 1983). M<strong>on</strong>itoring<br />

of berms movements over the 12 year period following<br />

c<strong>on</strong>structi<strong>on</strong> has dem<strong>on</strong>strated that such berms are of very<br />

minor value ,in retarding embankment movements (Fig. 5).<br />

In effect, berms perform much the same as the roadway<br />

side-slopes, and also create additi<strong>on</strong>al surface areas at<br />

temperatures averaging well above 0' C. The berms at the<br />

B<strong>on</strong>anza Creek site have resulted in net warming and tali k<br />

development in the lower slope areas, and have settled so<br />

that the original 1.8 m berm height has been reduced by<br />

30% to 50% in 12 years. These berms also progressively<br />

moved outward by 0.5 to 1.0 m as a result of embankment<br />

spreading forces, indicating that they are of little or<br />

no value in resisting such movements. The use of plastic<br />

foam insulated berms was also investigated at this site,<br />

and insulati<strong>on</strong> reduced the berm movements <strong>on</strong>ly slightly.<br />

Soil waste materials were used as a thin (0.7 m) berm at<br />

a road site over tundra in the Atigun valley <strong>on</strong> the<br />

Dalt<strong>on</strong> Highway. Although underlaid by cold (-4" C)<br />

permafrost, the berms at this site resulted in rapid<br />

thawing and settlement, and the development of thaw-p<strong>on</strong>ds<br />

al<strong>on</strong>gside the roadway after 2 to 3 years. L<strong>on</strong>g-term<br />

projecti<strong>on</strong>s for the B<strong>on</strong>anza Creek site indicate the same<br />

problem may eventually occur at that locati<strong>on</strong>.<br />

A recently completed study of the .effects of periodic<br />

maw removal from berm areas (Zarling, 1987) dem<strong>on</strong>strated<br />

that the mean annual surface temperature of the top of a<br />

berm could be lowered to approximately 0" C by this<br />

method, thereby retarding or eliminating the progressive<br />

annual thawing which occurs beneath berms which remain<br />

',snow-covered in winter.<br />

Normal Embankment<br />

6.lm Berm<br />

-9 LOrIg1n.I Qround Uno<br />

I 1 I I 1 I<br />

14 17 20 23 26 20<br />

Approxlmatr Diatance from Centerline (meters)<br />

FIGURE 4. <strong>Permafrost</strong> thaw depths and taliks beneath FIGURE 5. Thaw depths beneath lower embankment Slopes<br />

normal and peat-insulated embankments. with and without berms at B<strong>on</strong>anza Creek roadway Site.<br />

1226

Air-Cooling Ducts<br />

The use of corrugated metal pipes as natural c<strong>on</strong>vecti<strong>on</strong><br />

air-cooling systems to remove heat and refreeze embankment<br />

side-slope areas in winter, has been investigated at<br />

two sites in Alaska (Esch, 1983; Zarling, 1987). Criteria<br />

for design of these systems are now being evaluated<br />

based <strong>on</strong> the performance of an installati<strong>on</strong> of 0.6 m<br />

diameter ducts <strong>on</strong> the Alaska Highway near Gardiner Creek.<br />

The duct system inlets are elevated to just above the<br />

maximum snow level, leading to nearly horiz<strong>on</strong>tal 22 to 45<br />

m l<strong>on</strong>g heat exchange secti<strong>on</strong>s buried parallel to the<br />

roadway in embankment toe berms. The warmed air exits<br />

from vertical exhaust stacks up to 3.5 m in height. Such<br />

systems have dem<strong>on</strong>strated some significant cooling and<br />

stabilizing effects but have also been adversely affected<br />

by minor settlements which caused localized water p<strong>on</strong>ding<br />

within the ducts. This p<strong>on</strong>ding restricts the air flow<br />

and the resultant cooling performance. In c<strong>on</strong>structi<strong>on</strong>,<br />

care must be exercised to properly locate these ducts,<br />

prevent water entry and p<strong>on</strong>ding from minor duct settleto<br />

ments.<br />

Thermosyph<strong>on</strong> Devices<br />

Themosyph<strong>on</strong>s are sealed tubes which c<strong>on</strong>tain both gaseous<br />

and liquid phases of some compound such as amn<strong>on</strong>ia,<br />

fre<strong>on</strong>, propane or caqp<strong>on</strong>-dioxide. These devicesl: also<br />

tccasi<strong>on</strong>ally called heat pipes", "thermotubes , and<br />

thermopjles" serve as efficient heat exchangers between<br />

the air and the subsurface Soils. They functi<strong>on</strong> <strong>on</strong>ly<br />

when the top (radlator) porti<strong>on</strong> is cold enough to cause<br />

c<strong>on</strong>densati<strong>on</strong> of the internal gas. The c<strong>on</strong>densate then<br />

flows down the tube and re-evaporates up<strong>on</strong> c<strong>on</strong>tact with<br />

any porti<strong>on</strong> being harmed by the surrounding soil. Under<br />

optimum winter c<strong>on</strong>diti<strong>on</strong>s of heat transfer the entire<br />

thermosyph<strong>on</strong> wil . be cooled to the temperature of the<br />

ambient air, causjng the freezing and cooling of the<br />

soils surrounding the buried porti<strong>on</strong>. These devices have<br />

been successfully installed in inclined boreholes beneath<br />

permafrost related settlement areas <strong>on</strong> the Bethel , Alaska<br />

airport runway (McEadden, 1985) and <strong>on</strong> Farmers' Loop Road<br />

near Fairbanks. An installati<strong>on</strong> <strong>on</strong> the Huds<strong>on</strong> Bay<br />

Railway in Ontario as reported by Hayley (1983) wil also<br />

be of interest to the reader.<br />

and installing these devices,<br />

By properly designing for<br />

a significant refreezing<br />

and lowering of the temperature of permafrost may be<br />

achieved during the winter seas<strong>on</strong>. However, the designer<br />

must still anticipate and allow for the maximum seas<strong>on</strong>al<br />

thawing since thermosyph<strong>on</strong>s are inactive whenever the air<br />

temperature exceeds the subsurface soil temperatures.<br />

In wintertime it was observed that white-painted secti<strong>on</strong>s<br />

would also frequently accumulate surface frost while<br />

adjacent normal pavements would not.<br />

Slope Coverings<br />

Because of the extreme warming of roadway slopes, and the<br />

related problems of settlement, lateral spreading and<br />

cracking which result, some extreme soluti<strong>on</strong>s are justified<br />

in severe problem areas. The most extreme, passive<br />

treatment possible is to totally protect the slopes from<br />

solar radiati<strong>on</strong> and also to prevent any snow from accumulating<br />

<strong>on</strong> the surface in winter. To evaluate the benefits<br />

of this treatment, a secti<strong>on</strong> of the B<strong>on</strong>anza Creek<br />

experimental road embankment was covered with wood framed<br />

snow shed/solar screen. structures (Fig. 6). Temperatures,<br />

thaw depths, and movements of the covered and<br />

normal embankments slopes were observed for two years and<br />

recently reported by Zarling and Braley (1987). Thaw<br />

depth observati<strong>on</strong>s dem<strong>on</strong>strated that the sheds were able<br />

to c<strong>on</strong>trol and reverse the progressive thawing trends<br />

comm<strong>on</strong> to all other normal, insulated and bermed slopes.<br />

The mean annual slope surface temperatures were reduced<br />

from a normal slope value of 3.9" C to a value of -2.3" C<br />

beneath the sheds. The mean annual air temperature<br />

during this period was -3.4" C, indicating that the<br />

desired result had been achieved, with slope surfaces<br />

cooled by 6.2"C <strong>on</strong> a yearly average.<br />

Reflective Surfaces<br />

The benefits of different colored aggregates and of white<br />

and yellow paint in lowering roadway surface temperatures<br />

were intensively studied <strong>on</strong> Peger Road fn Fairbanks<br />

(Berg, 1985). The benefits of white paint applied to<br />

roads with settlement problems were also studied and<br />

reported by Reckard (1985). In the Peger Road study, the<br />

surface temperatures were recorded for a two year period<br />

<strong>on</strong> seven different surface treatments, whlch included Embankment Reinforcement with Geotextiles<br />

white and yellow paint, and rock chip-seals, with white<br />

marble, normal aggregate, and dark basalt aggregates. At The potentials for c<strong>on</strong>trolling the sags, dips, and cracks<br />

this site the white painted roadway secti<strong>on</strong> had a mean in roadways which are distressed from thawing permafrost<br />

annual surface temperature of -0.5" C compared to normal are being evaluated a sertes of field trials of geopavement<br />

at +1.1" C and air at -3.3" C. Two problems fabric reinforced embankments. These studies, Funded by<br />

with painted surfaces were observed. The paint was very the Alaska Department of Transportati<strong>on</strong>, have investigatslippery<br />

during rain, as compared to normal pavements, ed the effectiveness of different types and strengths of<br />

and also wore away rapidly under high traffic so that reinforcement for spanning subsurface voids, and for<br />

annual repainting would be required. This treatment preventing lateral spreading and cracking of embankments<br />

method would be effective in reducing thaw depths and <strong>on</strong> thaw-weakened foundati<strong>on</strong>s. Testing has dem<strong>on</strong>strated<br />

lowering surface and subsurface temperatures <strong>on</strong> low- that very high strength plastic grid and strap materials<br />

volume roads, but could <strong>on</strong>ly be used safely for secti<strong>on</strong>s can support embankments and span voids as wide as 2<br />

where stopping and turning movements were not required. meters, although allowance must be made for c<strong>on</strong>siderable<br />

1227

initial surface deformati<strong>on</strong> (Kinney, 1986). Voids<br />

created by thawing ice masses wider than 2 meters, or<br />

located al<strong>on</strong>g the edges of the embankment where anchorage<br />

of the reinforcement <strong>on</strong> both sides of the sag is not<br />

possible, wil c<strong>on</strong>tinue to create problems even with this<br />

approach. The reinforcement of embankments by using <strong>on</strong>e<br />

or more layers of geotextile to prevent spreading and<br />

cracking appears to hold the most promise, and several<br />

field evaluati<strong>on</strong>s are currently underway to test this<br />

approach.<br />

Preliminary Thawing or Excavati<strong>on</strong> of<br />

Thaw-Unstable Layers<br />

Active and passive pre-thawing methods may be effectively<br />

used to thaw and c<strong>on</strong>solidate unstable permafrost layers<br />

prior to c<strong>on</strong>structi<strong>on</strong>. The thaw-accelerati<strong>on</strong> effects .of<br />

stripping organic layers and of applying thin gravel pads<br />

with darkened surfaces and surface coverings have been<br />

investlgated and reported by Esch (1984). Pre-thawing<br />

for a period of <strong>on</strong>ly <strong>on</strong>e or two thawing seas<strong>on</strong>s prior to<br />

c<strong>on</strong>structi<strong>on</strong> can greatly reduce future thaw-related<br />

settlements from shallow ice-rich permafrost layers.<br />

However this method wil not provide much benefit when<br />

deep subsurface ice deposits exist. Settlement problems<br />

may also be avoided by excavati<strong>on</strong> and replacement of<br />

ice-rich foundati<strong>on</strong> soils, This method is occasi<strong>on</strong>ally<br />

used when problem soils are 1 imited to shallow depths and<br />

time is not available for more ec<strong>on</strong>omical pre-thawing<br />

operati<strong>on</strong>s. Large bulldozers with rippers are effective<br />

at excavating frozen soils. This operati<strong>on</strong> is most<br />

efficiently d<strong>on</strong>e when air temperatures are slightly below<br />

freezing to avoid the obvious thaw-related water and<br />

tracti<strong>on</strong> problems.<br />

SUMMARY AND SUGGESTIONS ON THE "IDEAL" EMBANKMENT DESIGN<br />

In 'the design of road embankments <strong>on</strong> warm permafrost,<br />

many structural and thermal c<strong>on</strong>siderati<strong>on</strong>s should be<br />

taken into account, and several design alternatives are<br />

available. Embankment top surfaces may become too warm<br />

and side-slope surfaces are almost certain to warm<br />

greatly, followed by talik development al<strong>on</strong>g both sides<br />

of the roadway, Embankments <strong>on</strong> thaw- unstable permafrost<br />

are likely to remain in some state of moti<strong>on</strong> for an<br />

indefinite period. N<strong>on</strong>e of the 15 road embankment<br />

secti<strong>on</strong>s m<strong>on</strong>itored by the Alaska Department of Transportati<strong>on</strong><br />

have ever reached a state of stabtlity in temperatures<br />

or in resistance to movement.<br />

If first costs were not a critical factor, the "ideal"<br />

embankment for warm permafrost may be <strong>on</strong>e which 'has<br />

nearly vertical slopes which do not accumulate snow, and<br />

the slopes should also be shielded or screened from the<br />

summer sun. The road surface would be separated thermally<br />

as far as possible from the subgrade soils. This<br />

could be achieved by insulati<strong>on</strong>; or by allowing air to<br />

circulate through a system of ducts or through a porous<br />

layer somewhere beneath the pavement. By these means the<br />

embankment wwld tend to approach the mean annual air<br />

temperature rather than some elevated temperature as now<br />

occurs, The embankment might also be reinforced with<br />

geo-fabrics to resist lateral spreading. While these<br />

treatments might not all be feasible, they are suggested<br />

to guide the designers thoughts toward implementing the<br />

results of road embankment research for warm permafrost<br />

c<strong>on</strong>diti<strong>on</strong>s.<br />

REFERENCES<br />

Berg, R (1985). Effect of Color and Texture <strong>on</strong> the<br />

Surface Temperature of Asphalt C<strong>on</strong>crete Pavements.<br />

Alaska Department of Transportati<strong>on</strong> (DOT) <strong>Research</strong><br />

Report, AK-RD-85-16.<br />

Braley, W A (1984). A Pers<strong>on</strong>al Computer Soluti<strong>on</strong> to the<br />

Modified Berggren Equatt<strong>on</strong>. Alaska DOT Report,<br />

AK-RD-85-19.<br />

C<strong>on</strong>nor. B (1984). Air Duct Svstems for Roadwav<br />

Stabilirati<strong>on</strong>.over Permafrist Areas. Alaska-DOT Report,<br />

AK-RD-84-10.<br />

Esch, D C (1973). C<strong>on</strong>trol of <strong>Permafrost</strong> Degradati<strong>on</strong><br />

Beneath a Roadway by Subgrade Insulati<strong>on</strong>. Proc.<br />

<strong>Permafrost</strong> - 2nd Intl. C<strong>on</strong>f., 608-622.<br />

Esch, D C (1983). Evaluati<strong>on</strong> of Experimental Design<br />

'<br />

Features for Roadway C<strong>on</strong>structi<strong>on</strong> over <strong>Permafrost</strong>.<br />

Proc. <strong>Permafrost</strong> - 4th Intl. C<strong>on</strong>f. , 283-288.<br />

Esch, D C (1984). Surface Modificati<strong>on</strong>s for Thawing of<br />

<strong>Permafrost</strong>. Alaska DOT Report, AK-RD-85-10.<br />

Esch, D C (1986). Insulati<strong>on</strong> Performance Beneath Roads<br />

and Airfields in Alaska. Alaska DOT Report,<br />

AK-RD-87-17.<br />

Greene, G W, Lachenbruch, A & Brewer, M (1960). Some<br />

Thermal Effects of a Roadway <strong>on</strong> <strong>Permafrost</strong>: Geological<br />

<strong>Research</strong>, 1960, U.S. Geological Survey Professi<strong>on</strong>al<br />

Paper 400-8, 6141-8144.<br />

Hayley, D W. et a1 (1983). Stabilizati<strong>on</strong> of Sinkholes <strong>on</strong><br />

the Huds<strong>on</strong> Bay Railroad. Proc. <strong>Permafrost</strong> - 4th Intl.<br />

C<strong>on</strong>f, , 468-473.<br />

Juday, G P (1983). Temperature Trends in the Alaska<br />

Climatic Changes Record. Proc. C<strong>on</strong>f. of Potential<br />

Effects of Carb<strong>on</strong> Dioxide Induced Changes in Alaska;<br />

Misc. Publ. 83-1, Sch. of Agr., Univ. of AK Fairbanks,<br />

76-91.<br />

Kellogg, W W (1983). Possible Effects of Global Warming<br />

<strong>on</strong> Arctic Sea Ice, Precipitati<strong>on</strong>, and,Carb<strong>on</strong> Balance.<br />

Proc. C<strong>on</strong>f. <strong>on</strong> Potential Effects of Carb<strong>on</strong> Dioxide<br />

Induced Changes in Alaska; Misc. Publ. 83-1, Sch. of<br />

Agr., Univ. of AK Fairbanks, 59-66.<br />

Kinnev. T C (1986). Tensile Reinforcement of Road<br />

Embhnkments <strong>on</strong> Polyg<strong>on</strong>al Ground. Alaska DOT Report,<br />

AK-RDyB6-29.<br />

McFadden. T (19851. Performance of the Thermotube<br />

<strong>Permafrost</strong>'Stabilizati<strong>on</strong> System in the Airport Runway<br />

at Bethel, Alaska. Alaska DOT Report, AK-RD-86-20.<br />

McHattie, R L & Esch, D C (1983). Benefits of a Feat<br />

Underlay Used in Road C<strong>on</strong>structi<strong>on</strong> <strong>on</strong> <strong>Permafrost</strong>. Proc.<br />

<strong>Permafrost</strong> - 4th Intl. C<strong>on</strong>f. 826-831.<br />

Reckard, M K (1985). White Paint for Highway<br />

Thaw-Settlement C<strong>on</strong>trol. Interim Report, Alaska DOT<br />

Report, AK-RD-85-16.<br />

Krzewinski, T G & Tart, R G. Thermal Design<br />

C<strong>on</strong>siderati<strong>on</strong>s in Frozen Ground Engineering. ASCE<br />

M<strong>on</strong>ograph.<br />

Zarling, J P & Braley, A W (1987). Thaw Stabilizati<strong>on</strong> of<br />

Roadway Embankments C<strong>on</strong>structed Over <strong>Permafrost</strong>. Alaska<br />

DOT Report, FHWA-AK-RD-87-20.<br />

1228

REMEDIAL SOLUTIONS FOR PIPELINE THAW SETTLEMENT<br />

J.E. Ferrelll and H.P. Thomas2<br />

1Alyeska Pipeline Service Company<br />

2Woodward-Clyde C<strong>on</strong>sultants, 701 Sesame Street, Anchorage, Alaska 99503 USA.<br />

SYNOPSIS<br />

Because of the elevated temperature of the oil, the trans Alaska pipeline was buried <strong>on</strong>ly in<br />

soils which were initially thawed or thaw stable. Applicati<strong>on</strong> of this criteri<strong>on</strong> resulted in<br />

burial of same 600 km of the line. Starting two years after startup, several short, segments of<br />

the buried line were identified which were experiencing thaw settlement. In resp<strong>on</strong>se to this, a<br />

suite of remedial soluti<strong>on</strong>s was developed to address the range of c<strong>on</strong>diti<strong>on</strong>s al<strong>on</strong>g the alignment.<br />

These included overburden relief, underpinning, relevelling, grouting, ground freezing, remoding<br />

and rerouting. The paper describes these remedial soluti<strong>on</strong>s and their applicati<strong>on</strong>, and<br />

summarizes several case histories.<br />

INTRODUCTION<br />

The trans Alaska pipeline cuts across the<br />

breadth of the State of Alaska starting from<br />

the barren northern arctic coastal plain at<br />

Prudhoe Bay and terminating in the southern<br />

ice-free port of Valdez. In its 1287-kilometer<br />

length, the warm oil pipeline traverses bath<br />

c<strong>on</strong>tinuous and disc<strong>on</strong>tinuous permafrost, and<br />

n<strong>on</strong>-permafrost, regians in the extreme southern<br />

end (see Figure 1) . The operating temperature<br />

for the 122-cm-diameter pipe varies from 62OC<br />

for receipt of the oil at Prudhoe Bay to 49'C<br />

at the Valdez Terminal facility. The pipeline<br />

is operated by Alyeska Pipeline Service<br />

Campany. At the present time, the pipeline is<br />

transporting 238,000 cubic meters of crude ail<br />

per day or 24 percent of the total USA domestic<br />

biL producti<strong>on</strong>. It is important to minim iz e<br />

disrupti<strong>on</strong> of this producti<strong>on</strong>.<br />

During the design and c<strong>on</strong>structi<strong>on</strong> phases,<br />

extensive soil investigati<strong>on</strong>s were performed to<br />

assure that the pipe foundati<strong>on</strong> material would<br />

support the warm pipe during operati<strong>on</strong>. Over<br />

8000 boreholes were drilled and 600 test pits<br />

were excavated to evaluate the foundati<strong>on</strong><br />

c<strong>on</strong>ditians. Extensive analysis of the data was<br />

performed to determine the safest and most<br />

ec<strong>on</strong>omical routing. During the pipe ditch<br />

excavati<strong>on</strong>, a c<strong>on</strong>tinuous foot-by-foot log was<br />

recorded to further assure the integrity of the<br />

design. Where these soil investigati<strong>on</strong>s<br />

indicated that the resulting thaw strains would<br />

be too severe OS a buried pipe, the pipe was<br />

elevated <strong>on</strong> a pile faundati<strong>on</strong>. In a few cases<br />

where an aboveground pipeline was not practical<br />

due to avalanche ox envir<strong>on</strong>mental factors, the<br />

pipe was buried either heavily-insulated or<br />

lightly insulated with an active mechanical<br />

refrigerati<strong>on</strong> system. At the end of<br />

c<strong>on</strong>seructi<strong>on</strong>, the pipeline c<strong>on</strong>sisted of 611 km<br />

of buried pipe and 676 kn of aboveground pipe.<br />

Even with the extensive soil investigati<strong>on</strong>s,<br />

small ice-rich areas were undetected in the<br />

c<strong>on</strong>tinuous and disc<strong>on</strong>tinuous permafrost z<strong>on</strong>es.<br />

These ice-rich areas became evident as the thaw<br />

bulb started to grow after the start of oil<br />

flow in mid-1977 (Thomas & Ferrcll, 1983) * k<br />

typical thaw bulb cross secti<strong>on</strong> is shown in<br />

Figure 2.<br />

Fig. 1.<br />

Route Of Trans Alaska Pipeline<br />

Fig. 2.<br />

Thaw Bulb Cross-Secti<strong>on</strong><br />

1229

In 1979, after two years of operati<strong>on</strong> and a<br />

period of rapid thaw bulb grawth, two oil leaks<br />

occurred in the buried pipe at Mileposts (MP)<br />

166 and 734. At MP 166, the pipe had settled<br />

1.2 n over a i20-m span as a result of thawing<br />

of massive ice in bedrock in a high mountain<br />

pass area and, at NP 734, the pipe hac settled<br />

'1.7 m over a 90-m span as a result of thawing<br />

of an ice-rich "permafrost island" in an<br />

otherwise thawed envir<strong>on</strong>ment (Johns<strong>on</strong>, 1981) .<br />

The leaks were c<strong>on</strong>tained by full-encirclement<br />

sleeves welded to the pipe with the annulus<br />

between the pipe wall and the sleeve filled<br />

with cement grout.<br />

Figure 3 shows the sleeve installed at MP 166.<br />

These sleeves allowed oil flow to resume.<br />

However, because they could not tolerate future<br />

pipe movements, pipe settlement had to be<br />

arrested. Based rnalnly <strong>on</strong> availability of<br />

c<strong>on</strong>tingency stockpiled material and equipment,<br />

expedient repair designs were implemented due<br />

to time c<strong>on</strong>straints. Both designs c<strong>on</strong>sisted of<br />

piles to carry the pipe loads, downarag loaas<br />

and other Loads which could result in further<br />

pipe movement.<br />

In 1982, Woodward-Clyde C<strong>on</strong>sultants was<br />

retained to summarize experience to date and<br />

develop new c<strong>on</strong>ceptual designs which could<br />

satisfy the aforementi<strong>on</strong>ed criteria. The goal<br />

of the designs was to assure uninterrupted<br />

throughput, low risk of pipeline damage,<br />

BELOUGROUND STABILITY PROGWU.1<br />

c<strong>on</strong>trolledrestraint <strong>on</strong> the exposed buried<br />

pipe, and be the most ec<strong>on</strong>omical with the<br />

C<strong>on</strong>current with repair of the two leaks, a inherent risks. These designs would also be<br />

line-wide extensive geotechnical investigati<strong>on</strong> c<strong>on</strong>strained by weather, river breakups,<br />

was initiated to locate other buried pipe<br />

permits, and availability of men, material, and<br />

segments which could also be experiencing thaw equipment. Since their development, these<br />

settlement but which had not yet damaged the c<strong>on</strong>tingent designs have significantly sped<br />

pipe sufficiently to cause leaks. This investigati<strong>on</strong>s,-evaluati<strong>on</strong>, and repairs.<br />

lnvestigativo program identified additi<strong>on</strong>al<br />

settled segments in the years from 1979 to<br />

1988. Ten of these have been successfully<br />

stabilized, beginning in 1980, before severe REMEDIAL SOLUTIONS, THEIR APPLICABILITY, AND<br />

pipe damage occurred, and an additi<strong>on</strong>al segment CASE HISTORIES<br />

is proposed for repair in 1988. The balance of<br />

the settled segments had <strong>on</strong>ly minor pipe The optimal remedial soluti<strong>on</strong> for a given pipe<br />

strains and are being m<strong>on</strong>itwred via settlement segment depends <strong>on</strong> a number af factors.<br />

m<strong>on</strong>itoring rods affixed to the top of the pipe, Especially important am<strong>on</strong>g these are (1) the<br />

instrumented pigs, and remote sensing (McDevitt amount of pipe settlement and resulting state<br />

and Cole, 1988). The necessity for a repair of pipe curvature at the time the problem is<br />

was determined by calculating pipe curvature<br />

identified, and (2) thc potential for future<br />

change fram the as-built pipe profile to the pipe settlement and its rate.<br />

12310<br />

present pipe profile determined from a closelyspaced<br />

top-of-pipe survey (Simm<strong>on</strong>s and Alto,<br />

1988).<br />

Defined as that value of pipe curvature<br />

corresp<strong>on</strong>ding to <strong>on</strong>set of buckling, critical<br />

buckling curvature (K 1 is based <strong>on</strong> results of<br />

iull-scale pipe buck'ixing testing (Bouwkamp &<br />

Stephen, 1973). If a value of 85 percent ox<br />

more of K was measured, Alyeska has proceeded<br />

to stabilfge the settled pipe <strong>on</strong>e by of several<br />

measures. Both the stabilized and<br />

n<strong>on</strong>-stabilized settlement areas are being<br />

manitored <strong>on</strong> a regular basis. Data from the<br />

stability m<strong>on</strong>itoring program have shown that<br />

the thaw bulb growth as of 1988 is slow and<br />

little additi<strong>on</strong>al pipe movement is occurring.<br />

As part of the early belowground stability<br />

investigati<strong>on</strong>, available c<strong>on</strong>structi<strong>on</strong><br />

geotechnical informati<strong>on</strong> and operati<strong>on</strong> data,<br />

were evaluated. As questi<strong>on</strong>ed segments were<br />

identified, m<strong>on</strong>itoring rods were installed <strong>on</strong><br />

top of the pipe and instrumented soil boreholes<br />

were drilled al<strong>on</strong>g-side the pipe. If the rods<br />

revealed a settled area or the soil aata and<br />

thermistors identified ice-rich permafrost, a<br />

more-detailed geotechnical investigati<strong>on</strong> was<br />

initiated to determine the foundati<strong>on</strong><br />

parameters. However, the repair design was<br />

often delayed because the results from further<br />

drilling and soil testing could use up several<br />

weeks of the short c<strong>on</strong>structi<strong>on</strong> seas<strong>on</strong>. It<br />

became evident that, if a c<strong>on</strong>ceptual repair<br />

design could be identified early <strong>on</strong>, the<br />

investigati<strong>on</strong> program could be better focused<br />

and investigati<strong>on</strong> and repair designs could<br />

thereby proceed <strong>on</strong> parallel courses. Tt was<br />

decided in 1981 that a suite of feasible repair<br />

designs from which Alyeska could pattern the<br />

geotechnical investigati<strong>on</strong> would reduce<br />

investigative cost and design time and<br />

facilitate implementati<strong>on</strong> of remedial measures.<br />

These Repair C<strong>on</strong>tingent Designs could also<br />

identify x'equired materials (especially<br />

l<strong>on</strong>g-lead items) and required Soil3 informati<strong>on</strong><br />

for implementati<strong>on</strong>.

As shown in Table 1, an urgent situati<strong>on</strong> is <strong>on</strong>e Most effective for spbns of 15 tu 75 m,<br />

where pipe curvature is close to buckling and overburden relief can be dsed in c<strong>on</strong>juncti<strong>on</strong><br />

rapid additi<strong>on</strong>al settlement is expected. In with relevelling (see later discussi<strong>on</strong>) and may<br />

such a situati<strong>on</strong>, the optimal remedial soluti<strong>on</strong> be temporary or permanent. Since<br />

the pipe<br />

would probably be <strong>on</strong>e which quickly arrested often needs to be uncovered to establish survey<br />

pipe settlement or relevelled the pipe<br />

targets and inspect it for possible wrinkles,<br />

(relieved pipe strains). If the settlement and the additi<strong>on</strong>al cost of providing overburden<br />

pipe strains kould not be alleviated, the relief may be small. If sufficient ground<br />

problem area could be bypassed with a remute. slope is available, surface drainage may be<br />

For another segment where pipe strains axe not permanently directed away from the excavati<strong>on</strong><br />

presently severe, a more measured resp<strong>on</strong>se such as was d<strong>on</strong>e at PIP 416. In flat terrain with a<br />

as mitigating the cause of the thawing might be high water table, the excavati<strong>on</strong> can be<br />

appropriate. If thaw strains were high but regraded using lightweight backfill.<br />

future thaw settlement was not expected,<br />

relevelling the settled pipe is appropriate. Underpinning<br />

Lastly, where settled segments are identified<br />

with low pipe strains and no or little future The principle of underpinning is to limit<br />

settlement, Alyeska has elected to perform<br />

periodic level surveys of the rods attached to<br />

the buried pipe.<br />

Following review of a large number of possible<br />

remedial soluti<strong>on</strong>s, Alyeska adopted the<br />

following c<strong>on</strong>tingency designs, based <strong>on</strong><br />

technical feasibility, likelihood of success,<br />

relative ec<strong>on</strong>omics, and ease of c<strong>on</strong>structian.<br />

Once these c<strong>on</strong>cepts were adopted, investigative<br />

costs have dropped from abaut 35 to about 10<br />

percent of the repair cost. Usually a<br />

combinati<strong>on</strong> of the fallowing c<strong>on</strong>tingent designs<br />

have been utilized by Alyeska. Table IT<br />

summarizes the applicati<strong>on</strong>s of the c<strong>on</strong>cepts.<br />

Overburden Relief<br />

further pipe strain by supporting the pipe at<br />

discrete points. As menti<strong>on</strong>ed earlier, after<br />

sleeves were placed cn the pipe at MP 166 and<br />

134 in 1979, the pipe was underpinned using<br />

Vertical Suppart Members (VSEl's) and Alyeska<br />

standard aboveground support hardware (see<br />

Figure 3). Even though cover depths were<br />

reduced at both sites, the weight of the<br />

backfill was still a significant porti<strong>on</strong> of the<br />

load which the VSM's had to support. Aiso,<br />

because the warm pipe remains in c<strong>on</strong>tact with<br />

the soil, the thaw bulb c<strong>on</strong>tinues to grow and<br />

causes additi<strong>on</strong>al downdrag loads <strong>on</strong> the VSM's.<br />

Thermal device.s could be used in the VSM's, but<br />

their effectiveness is limited by the coupled<br />

proximity of the warm pipe. At MP 200.2,<br />

underpinning was utilized to stop further pipe<br />

settlement. At this site, the piles also<br />

supported a crossbean which was used as a<br />

reacti<strong>on</strong> surface to jack against €or<br />

relevelling the pipe to reduce curvature. A5<br />

an additi<strong>on</strong>al benefit, the piles were used as<br />

temporary>swldier piles for a braced excavati<strong>on</strong><br />

to expose the pipe in the active river channel.<br />

As the oil-filled pipe tries to span over a<br />

developing settlement z<strong>on</strong>e of finite length, it<br />

behaves Like a beam and the weight of the soil<br />

backfill <strong>on</strong> top of the pipe comprises a major<br />

part of the laad it must carry. Far this<br />

reas<strong>on</strong>, settled pipe has been observed<br />

to<br />

rebound significantly as a result of removing<br />

pipe backfill. Early experience with this was Relevellinq<br />

at 1IP 416 (see Figure 4) and 720 in 1981 when<br />

cover was removed fram above the pipe. At MP The principle in relevelling is to relieve pipe<br />

720 , 1.8 m of cover was removed over a length distress by bringing the pipe into a shape with<br />

of about 46 m which resulted in the pipe less severe bending c<strong>on</strong>diti<strong>on</strong>s. In practice,<br />

springing up 31 cm with associated reducti<strong>on</strong> in this is d<strong>on</strong>e by first rem0vir.g the overburden<br />

pipe strains. SmaLl amounts of rebound have from. the pipe and then lifting the pipe at<br />

also been observed at other sites.<br />

discrete points using sidebooms or pressurized<br />

air bags. The pipe is lifted up to its<br />

originai profile ox possibly above to allow for<br />

c<strong>on</strong>tinued settlement. Finally, a lean mix<br />

grout bedding is placed beneath the pipe. (The<br />

pipemayor may not be reburied.) Careful<br />

c<strong>on</strong>trol is required during the lifting apd,<br />

because the pipe is generally in compressi<strong>on</strong>,<br />

lateral restraint must be maintained throughout<br />

the process.<br />

As relevelling is not a thermal soluti<strong>on</strong>, the<br />

thaw bulb c<strong>on</strong>tinues to grow and this could<br />

require a sec<strong>on</strong>d cycle of Lifting to be d<strong>on</strong>e in<br />

the future. At MP 720 (see Figure 51, the pipe<br />

was lifted 10 cm higher than its original<br />

profile to allow for future Settlement.<br />

Alyeska has found that relevelling is best used<br />

where pipe scttlement is neasly complete and,<br />

like most of the other available techniques, it<br />

may be difficult tc use in river crossings.<br />

However, relevelling has been utilized by<br />

Alyeska in seven of the ten repairs performed<br />

between 1980 to 1987. First used ir. 1986, the<br />

pig. 4. Unburied and ~ ~ ~ e Pipeline - ~ u ~ pressurized ~ ~ air ~ bag t lifting ~ ~ technique (see<br />

at Milepost 416<br />

Figure 6) appears to be especially cost.-<br />

1231

TABLE I<br />

REMEDIAL SOLUTIONS MATRIX<br />

Pipe Potential for<br />

Curvature Future<br />

Possible Remedial<br />

K Settlement Objective Soluti<strong>on</strong>s<br />

High High Arrest pipe settlement Reroute, relevel<br />

1'85% Kcr)<br />

and relieve pipe<br />

and underpinning,<br />

strain<br />

remode<br />

nigh LOW Relieve pipe strains Overburden relief,<br />

relevel<br />

LOW High arrest pipe settlement underpinning, maintain<br />

permafrost<br />

LOW LOW M<strong>on</strong>itor pipe settlement Periodic m<strong>on</strong>itoring<br />

surveys<br />

SUEWRY TABLE - THAW SETTLEMENT PROBLEMS AND SOLUTIONS<br />

1980 - 1988<br />

Depth Pipe 8 of Potential<br />

Mile-<br />

of Settle- Critical for Throughpost<br />

Cover ment Span Cuxvature Future<br />

Repair<br />

Put<br />

(Date) Area - (m) (m) (m) ( K ~ ~ ) Settlement Soluti<strong>on</strong>s LOSS<br />

Remarks<br />

167.2 Atigun<br />

(6/801 Pass<br />

2<br />

0.76<br />

152 N/A High Drainage, grouting, NO Thermal erosi<strong>on</strong> problem - main-<br />

( low) qround freezing. tain permafrost.<br />

416 Fairhanks<br />

(8/811<br />

2<br />

0.95<br />

146 83% (60% High Overburden relief, NO Remoded pipa is fully restrained.<br />

aEter re-<br />

A/G ramode,<br />

bound)<br />

underpinning.<br />

720 T<strong>on</strong>sina<br />

(9/81)<br />

1.7<br />

0.46<br />

55 64% (c501 L<strong>on</strong> Overburden relief, No Ground surface regraded. Pipe<br />

after re-<br />

relevelling using<br />

elevatian raised 10 cm higher<br />

bound)<br />

sidebooms .<br />

than original profile.<br />

168.4 Atigun<br />

(4/82) Pass<br />

2<br />

1.76<br />

76 1708 LOW Relevelled using No<br />

sidebooma.<br />

200.2 Dietrich<br />

(3/83) River<br />

3.5<br />

0.91<br />

44 180% High Pile underpinning Slight Located beneath active river<br />

and cable supports. flow channel. Later replaced by<br />

Relevelling by jack- reduc- MP 200.6 reroute.<br />

' ing against cross ti<strong>on</strong><br />

beam.<br />

730.2 T<strong>on</strong>sina<br />

13/83)<br />

3<br />

0.61<br />

122 140% Low Relevelling using No Unsettled pipe haunches were<br />

sidebooms. Lowered slightly to improve<br />

curvature.<br />

46 North<br />

(10/83) Slope<br />

3<br />

0.76<br />

67 150% LOW Relevelling using NO Little further settlement<br />

sidebooms.<br />

expected.<br />

200.6 Dietrich<br />

(11/84) River<br />

4.6<br />

4.6<br />

81 1200% High Remode to A/G, xe- 6:day Beneath active river channel,<br />

est. route around ar*a. shut- pipe was never exposed.<br />

down<br />

601 McCallum<br />

19/66] Creek<br />

3<br />

0.79<br />

46 160% Low Relcvelling using No No remsininq permafrost.<br />

airbags.<br />

158 Atigun<br />

(10/86) River<br />

4<br />

1.07<br />

46 120 to LOW Relevelling usiny NO NO remaining petmatroat. In<br />

160% airbags.<br />

active floodplain.<br />

167.4-<br />

167.6 Atigun<br />

17/88] Pass<br />

2<br />

0.9-<br />

1.0<br />

91- 60 to High Relevel, repair N<strong>on</strong>e Proposed work for 1988. Pipe has<br />

122 70% (15 em/ damaged insulati<strong>on</strong>, ex- 50-cm-thick insulati<strong>on</strong> broken by<br />

est. yr.1 improve drainage. pectcd acttlemant.<br />

1232

installed or. either side of a buried segment,<br />

pipe settlement war, halted and some minor<br />

rebound was noted.<br />

At MP 167, Alyeska. used a 350-k1.I portable<br />

freezing plant to circulate chilled brine<br />

through 268 vertical freeze pipes installed <strong>on</strong><br />

bath sides of the pipeline (see Figure 7) . TO<br />

maintain the recreated frozen z<strong>on</strong>e, 133 heat<br />

pipes were then installed, <strong>on</strong>e in every other<br />

freeze pipe (Thomas et al, 1982). In additi<strong>on</strong>,<br />

heavy pipe insulati<strong>on</strong> is generally required and<br />

groundwater flow velocities need to be<br />

negligible or reduced to less than about<br />

2 rnfday by means of grouting. At MP 167, there<br />

was 60 cm wf insulati<strong>on</strong> surrounding the pipe<br />

and, as menti<strong>on</strong>ed previously, groundwater flow<br />

was c<strong>on</strong>trolled by water shut-off qroutinq.<br />

Grouting<br />

Fig. 6. Air Bag for Pipe Lifting Fig. I. Grwund Freezing at Milepost 167<br />

Grouting can be used for soil improvement or<br />

for actual pipe lifting. At MP 167 (Rtigun<br />

Pass) where c<strong>on</strong>vective thawing was a problem,<br />

grauting was effectively used to (1) create a<br />

barrier to groundwater flaw (seepage cutoff),<br />

and (2) to reduce the permeability of pervious<br />

soils in the thaw bulb.<br />

Although it has not yet been used by Alyeska<br />

for pipe lifting, displacement grauting appears<br />

to be a promising relevelling technique,<br />

especially in areas with difficult access such<br />

as river crossings. For its use, a closelyspaced<br />

array of top-of-pipe survey paints would<br />

be required to assurec<strong>on</strong>trol of the lift<br />

operati<strong>on</strong>.<br />

Ground Freezing<br />

Refrigeratian may be used tw refreeze the thaw<br />

bulb or to keep the thaw bulb from increasing.<br />

in size. Both mechanical and passive<br />

techniques have been ut-ilized. Mechanical<br />

refrigerati<strong>on</strong> is mainly useful as a temporary<br />

measure. Free-standing thermosyph<strong>on</strong>s or heat<br />

pipes are the passive technique Alyeska has<br />

used. First used as a remedial measure before<br />

oil flow at MP 723 (fleuer et all 1981) , Alpfska<br />

eliminated heat flow into the remaining<br />

permafrost and allowed the piles with their<br />

heat pipes to refreeze the ground for<br />

pile<br />

suppart. The pipe was securely fastened to the<br />

support beams and is fully restrained.<br />

has c<strong>on</strong>structed several heat pipe test secti<strong>on</strong>s<br />

in different types of terrain. In <strong>on</strong>e test At MP 200.6, further addressed in the following<br />

secti<strong>on</strong> where clasely-spaced heat pipes were<br />

secti<strong>on</strong>, the buried pipe was remoded to<br />

1233<br />

Rernadinq<br />

The elevated c<strong>on</strong>structi<strong>on</strong> mode used to support<br />

nearly half of the pipeline was specifically<br />

designed for traversing ice-rich permafrost<br />

areas. Because it decouples the warm pipe from<br />

the -frozen ground, remclding to elevated could<br />

appear to be an obvious soluti<strong>on</strong> to a pipe<br />

settlement problem. However, because raising<br />

the pipe profile 3 IX (or more) generally<br />

requires a shutdown of the pipeline or a tricky<br />

stopple and bypass operati<strong>on</strong>, Alyeska ha6 opted<br />

for rernoding <strong>on</strong>ly as a last-resort soluti<strong>on</strong>.<br />

Remoding to aboveground was used at r1P 416<br />

where the pipe was pile-supported at its<br />

rebounded proflle and the ground surface was<br />

excavated to 60 cm below the bottom of pipe<br />

(see Figure 4). This in effect remoded the<br />

pipeline without interrupting the oil flow.<br />

Mast of the pipe settlement (thawing<br />

permafrost) areas are also areas of high ground<br />

water. MP 416 was unique in thiG respect in<br />

that it was in a sidehill situati<strong>on</strong> and the<br />

excavati<strong>on</strong> could be drained, The remoded pipe

aboveground and, rerouted around the problem<br />

area using typical Alyeska designs and<br />

hardware.<br />

Reroutinq<br />

An alternate soluti<strong>on</strong> may be to bypass an<br />

especially-severe problem area. Depending <strong>on</strong><br />

ground c<strong>on</strong>diti<strong>on</strong>s in the mea, the reroute<br />

could be in the buried or elevated mode. The<br />

reroute requires a shutdown or stopple and<br />

bypass and is usually justified <strong>on</strong>ly in<br />

resp<strong>on</strong>se to a problem not amenable to other<br />

:eluti<strong>on</strong>s. The IIP 200.6 repair (see Figure 8)<br />

is an example of a reroute because of high pipe<br />

strain rates and the difficulty of adequately<br />

arresting further settlement. Simm<strong>on</strong>s and<br />

Ferrell (1986) have described this repair in<br />

det.a i 1 .<br />

have been carried out without interrupting<br />

the oil flow. Other buried segments are<br />

being m<strong>on</strong>itored regularly for possible<br />

future remedial acti<strong>on</strong>.<br />

The pipeline segments that have been<br />

stabilized since the first repairs in 1979<br />

amount to less than 0.2 percent of the<br />

611 km of buried pipeline.<br />

ACKNOWLEDGEMENTS<br />

The authors wish to thank Alyeska, the operator<br />

of the trans Alaska pipeline, for permissinn to<br />

publish this paper and the Owners of TAPS for<br />

their c<strong>on</strong>currence. We also thank colleagues<br />

who reviewed draft versi<strong>on</strong>s of the paper for<br />

their helpful comments and suggesti<strong>on</strong>s.<br />

I,,<br />

Fig. 8.<br />

CONCLUSIONS<br />

Hilepost 200 Pipeline Reroute.<br />

Even with a very extensive subsurface<br />

investigati<strong>on</strong> program, occasi<strong>on</strong>al sporadic<br />

occurrences of ice-rich permafrost nay be<br />

undetected in otherwise initially-thawed,<br />

or thaw-stable areas.<br />

In view af this, it is highly desirable to<br />

have a variety of remedial soluti<strong>on</strong>s for<br />

pipe thaw settlement developed for buried<br />

segments of a warm pipeline c<strong>on</strong>structed in<br />

arctic and/or subarctic regi<strong>on</strong>s.<br />

No single mluti<strong>on</strong> is likely to be best<br />

for all situatians. The optimal soluti<strong>on</strong><br />

will depend <strong>on</strong> pipe settlement/ curvature,<br />

local permafrost characteristics,<br />

anticipated pipe settlementslsettlement<br />

rates, topographic setting, logistics and<br />

other factors.<br />

Based <strong>on</strong> Alyeska's operating experience,<br />

overburden relief followed by relevelling<br />

using pressurized air bays appears to be<br />

<strong>on</strong>e of the more successful and ec<strong>on</strong>omical<br />

REFERENCES<br />

Bouwkamp, J.G. and Stephen, R.11. (1973) , "Large<br />

Diameter Pipe Under Combined Loading,"<br />

ASCE Transportatian Engineering Journal,<br />

August .<br />

Heuex, C.E., Krzewinski, T.G. and Netz, 11.C.<br />

(1981), "Special Thermal Design to Prevent<br />

Thaw Settlement and Liquefacti<strong>on</strong>,"<br />

Proceedings of Fourth Canadian <strong>Permafrost</strong><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, Calgary, Alberta, March 2-6.<br />

Johns<strong>on</strong>, E.R.<br />

(1981) , "Busied- Oil Pipeline<br />

Design and Operati<strong>on</strong> in the Arctic -<br />

Less<strong>on</strong>s Learned <strong>on</strong> the Alyeska Pipeline:"<br />

37th Petroleum and Mechanical <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>,<br />

Dallas , Texas.<br />

McDevitt, P.G. and Cole, G.E. (1988),<br />

"Profiling the Trans Alaskan Pipeline<br />

Buried Pipe IJsing the Heath TSI Pipe<br />

Locator," Proceedings of API Pipeline<br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, HQUStOn, Texas, April 26-27.<br />

Simm<strong>on</strong>s, G.G. and Ferrell, J.E. (1986),<br />

"Alyeska Reroutes Trans-Alaska Pipeline at<br />

MP 200 ," Proceedings of Fourth<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> Cold Regi<strong>on</strong>s<br />

Engineering, ASCE, Anchorage, Alaska,<br />

February 24-26.<br />

Simm<strong>on</strong>s, G.G. and Alto, J.V. (1988),<br />

"Calculati<strong>on</strong> of Pipeline Curvature by<br />

Polynomial Approximati<strong>on</strong> Using Discrete<br />

M<strong>on</strong>itoring Points," <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> Pipeline Infrastructure,<br />

ASCE, Bost<strong>on</strong>, Massachusetts, June 6-7.<br />

Thomas, H.P., Johns<strong>on</strong>, E.R., Stanley, J.M.,<br />

Shuster, J.A. and Pearsun, S.W. (1982),<br />

"Pipeline Stabilizati<strong>on</strong> Project at Atiqun<br />

Pass," Proceedings of Third <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

Symposium <strong>on</strong> Ground Freezing, Hanover, New<br />

Hampshire, June 21-24.<br />

remedial techniques.<br />

Thomas, 1l.P. and FerreL1, J.E. (1983) I<br />

As a result of Alyeska's settlement "Thermokarst Features Associated with<br />

m<strong>on</strong>itoring program, ten 50- tn 150-m-l<strong>on</strong>g Buried Secti<strong>on</strong>s of the Trans-Alaska<br />

buried seqments have been stabilized <strong>on</strong> Pipeline, I' Proceedings of Fourth<br />

the trans Alaska pipeline sincc 1980.<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> c<strong>on</strong>ference <strong>on</strong> <strong>Permafrost</strong>,<br />

llearly all of these stabilizati<strong>on</strong> projects Fairbanks, Alaska, July 17-22.<br />

1234

A FROZEN FOUNDATION ABOVE A TECHNOGENIC TALIK<br />

I.E. Guryanov<br />

Permafmst Institute, Siberian Branch of the U.S.S.R. Academy of Sciences, Yakutsk, U.S.S.B.<br />

SYNOPSIS A hitudy is made of the combined influence of an unfrozen area that has formed<br />

in the permafrost surrounding a warm pit shaft and of hollow box foundati<strong>on</strong>s ventilated with<br />

outdoor air during the wintertime, up<strong>on</strong> the temperature regime and load-carrying of capacity<br />

the baaes of surface pit buildings. The feasibility of a stable, frozen base that is bounded ox<br />

partially supported by an unfrozen axe&, ia dem<strong>on</strong>strated. Data <strong>on</strong> the reliability and ec<strong>on</strong>omical<br />

profitableness of stxuotural-and-technologioaL designs of foundati<strong>on</strong>s are given.<br />

The range of problems c<strong>on</strong>cerning the building<br />

of pit aurfaces in the Far North involves<br />

structures for which - when the thawing of the<br />

bases is not acceptable - it ia also unfeasible<br />

to retain earth materials in the frozen<br />

atate. Such a kind of projects axe headgear<br />

buildings (headfxamesj. Under the acti<strong>on</strong> of<br />

the warm pit ahaft there forms a vertical talik<br />

below them, throughout the depth of the<br />

shaft within the permafrost. If the headframe<br />

is supported by earth materials which, while<br />

thawing; subside or lose their strength,<br />

then the necessity of maintaining them in the<br />

frozen state, combined with the inevitable formati<strong>on</strong><br />

of a talik, means that c<strong>on</strong>venti<strong>on</strong>al<br />

methods of retaining the permafrost are inapplicable.<br />

Experience has ahown that the use of the foundati<strong>on</strong>s<br />

outside of the unfrozen area leads to<br />

an increase in weight of socle atructuxes<br />

Fig.1 Schemes for Tower Headframe Building<br />

which overlap the talik as well as in the wo- Foundati<strong>on</strong>8 and Their Thermal Interacti<strong>on</strong><br />

pe of c<strong>on</strong>structi<strong>on</strong> work <strong>on</strong> the building. Coo- with <strong>Permafrost</strong>. The + and - aigns refer<br />

ling collars such as fore-shafts (Novikov,<br />

to the ambient temperature.<br />

19593 failed also to provide the expected ei- a piles foundati<strong>on</strong>e with a surface cellar;<br />

fect in an attempt to get the base frozen. In b - hollow ventilated foundati<strong>on</strong>s.<br />

the case of keeping technologically needed<br />

warm underground spaces, it evidently becom8a<br />

necesaary to have available the foundati<strong>on</strong>s<br />

for the structure as a whole, with a high apa- In view of the complexity of the general Pormutial<br />

rigidity and high thermal lag that provi- lati<strong>on</strong> and crudeness of initial data, ths prodes<br />

for a c<strong>on</strong>atantly frozen atate of earth ma- blem of heat exchange between the founda"c<strong>on</strong><br />

terials at the footing. Piles OX pier Poundati<strong>on</strong>s<br />

with a aurface cellar andeep box foundati<strong>on</strong>s<br />

(Fig. 1) exemplify alternative methods<br />

for laying the foundati<strong>on</strong>s for headframes<br />

when c<strong>on</strong>structi<strong>on</strong> work ia proceeding by the<br />

principle 1 CHnn II-18-76. In c<strong>on</strong>trast to thevariant<br />

of a surface cellar that forms B temperature<br />

field at the footing close to a natural<br />

field, box foundati<strong>on</strong>s which axe ventilated<br />

with outdoor air during the wintertime, &re<br />

also examined as being a factor of c<strong>on</strong>trolling<br />

the temperature regime of permafrost by c<strong>on</strong>aidering<br />

an example of structural developments<br />

as d<strong>on</strong>e by th.is author in the design of a northem<br />

mine.<br />

1235<br />

a<br />

\<br />

0<br />

and earth ttiaterlals is visualized by dividing<br />

it into two problems which are solved indepen<br />

dently but are related by bounaary c<strong>on</strong>diti<strong>on</strong>s<br />

and results, name1 (a) heat exchange in the<br />

founaati<strong>on</strong>, and (by heat exchange in earth materials.<br />

Soluti<strong>on</strong>s of both problems are abtained<br />

by iterati<strong>on</strong>.<br />

We replace the three-dimensi<strong>on</strong>al problem of<br />

heat exchange by a two-dimensi<strong>on</strong>al, axisymmetrcictll<br />

problem, in order to perform computati<strong>on</strong>s<br />

<strong>on</strong> a medium-scale computer, which leads to some<br />

overestimati<strong>on</strong> of the calculated temperature of<br />

earth materiale ana to a relevant reeerve of<br />

load-carrying capacity of the base. Rectangulsr<br />

foundati<strong>on</strong>s and equivalent round foundati<strong>on</strong>s<br />

6

2-2<br />

2-2<br />

3900<br />

+<br />

3200<br />

1-1<br />

1 700 &<br />

600 600 600 & 700<br />

Big.3 Box Foundati<strong>on</strong> of Headframe No. 2<br />

and its Calculated Schema (Dashes) in the<br />

Axieyrnrnetxlcal Problem of Beat Exchange.<br />

Pig.2 Box Poundati<strong>on</strong> of Weadframe No. 1<br />

and its Calculated Scheme (dashes) in the<br />

Axisymmetric Problem of Neat Exchange.<br />

for headframes No. 1 and No. 2 of the mine indicated<br />

are shown in pig^ 2 and 3, reapectively,<br />

and their geometrical characteristics are<br />

given in Table I.<br />

TABLE I<br />

Outer Surface F and Volurrie V of Headframe<br />

Poundat i<strong>on</strong>s<br />

Variant Headframe No. 1 Headframe 110.2<br />

31, .2 v, .3 F, .2 v, m 3<br />

Rectangular 1 930 1 145 998 564<br />

Hound 1 980 1 136 996 563<br />

the problem of heat exchange between the bu ilding-and<br />

its base was c<strong>on</strong>structed with a seas<strong>on</strong>al<br />

change of the kind of boundary c<strong>on</strong>diti<strong>on</strong>s.<br />

A warm period (from 16 April to 15 October)<br />

corresp<strong>on</strong>ds to the warming of the base<br />

due to the c<strong>on</strong>tiguoua headframe spaces, while<br />

a cold period (from 16 October to 15 April)<br />

corresp<strong>on</strong>ds to the cooling of the baae due to<br />

mechanical ventilati<strong>on</strong> of the underground spacea<br />

with outdoor air.<br />

Boundary C<strong>on</strong>diti<strong>on</strong>a for the Warm Period<br />

During a warm period of the year underground<br />

spacee of headframes should be tightly cloQed,<br />

and c<strong>on</strong>ducti<strong>on</strong> through protecti<strong>on</strong> etxucturee<br />

together with radiati<strong>on</strong> and c<strong>on</strong>vecti<strong>on</strong> in the<br />

QiF volume of a hollow foundati<strong>on</strong> are the Pactors<br />

of heat losses into the base. C<strong>on</strong>vective<br />

heat exchange is brought about by the vertical<br />

walls of the cellar <strong>on</strong> the aide of the shaft<br />

that la ventilated with a warm air, with the-,<br />

resultant effect defined by the functi<strong>on</strong> (Graber<br />

et d., 1958):<br />

Nu O.I(Gr*Prj 1/3, (1)<br />

The structures are supported by permafroat eug-<br />

Linoks of 0.17 total moisture c<strong>on</strong>tent having<br />

a layered-latticed cryogenic structure. The<br />

thermal Characteristics of earth materials were<br />

taken according to CHdI 11-18-76; the initial<br />

temperature waa -1.3OC throughout the calculated<br />

depth of the foundati<strong>on</strong>s. The soluti<strong>on</strong> of<br />

1236<br />

where Iuu, Gr, and Pr axe the Nusaelt, Grasshof'<br />

and Prandt criteria. B'uncti<strong>on</strong> (1) holds<br />

true when GrmPx 3 2.109 but ie also applicable<br />

for the foundati<strong>on</strong> c<strong>on</strong>sidered, for which<br />

Gr.Pr 16.3XlOl6 Subject to the Nusselt<br />

criteri<strong>on</strong>

where d, is the heat transfer coefficient,<br />

W/(m2 *IC); E is the height of the wall; and<br />

1 is the coefficient of heat c<strong>on</strong>ducti<strong>on</strong> of air,<br />

W/(m.@i functi<strong>on</strong> (1) yields the expressi<strong>on</strong> for<br />

the coefficient of C<strong>on</strong>vective heat transfer<br />

which. is independent of the size of the underground<br />

space :<br />

where 3 Is kinematic viscosity of the ah,<br />

2<br />

m /s; 7 is free fall accelerati<strong>on</strong>, m/c2; and<br />

8,and 8, are the air temperature and the<br />

wall. rsurfaoe temperature, K, respectively.<br />

In doing the calculati<strong>on</strong>s, the temperature was<br />

averaged for each m<strong>on</strong>th, with the values of<br />

the coefficlents of c<strong>on</strong>vective heat transfer<br />

for the callax for the entire warm period being<br />

the following: through radiati<strong>on</strong> - d, =<br />

= 1.49 W/(m2*K), and through c<strong>on</strong>vecti<strong>on</strong> - d, =<br />

P 2.15 W/(rn2*K). The total heat resistance<br />

B, = ( d, + d, )'I = 275 m2*K/kW,<br />

is by an order of magnitude lower than the resistance<br />

to heat transfer to the protecti<strong>on</strong><br />

structures. Therefore, <strong>on</strong>ly c<strong>on</strong>ductive heat<br />

exchange waa simulated <strong>on</strong> the computer, with<br />

the introducti<strong>on</strong>, however, of an daiti<strong>on</strong>al<br />

llequivalenttt protecti<strong>on</strong> layer, whose heat c<strong>on</strong>ducti<strong>on</strong><br />

was determined from the total heat resistance<br />

of the undergound apaces, while heat<br />

capacity was additive for the mass of all the<br />

foundati<strong>on</strong> etructurea withln the space (see<br />

Figs 4 and 5) .<br />

For the <strong>on</strong>aef date of the warm period, the mean<br />

temperature, of the Itequivalent" layer is equal<br />

to the air temperature in the cellar. On the<br />

inner surface of the layer the temperature is<br />

due to c<strong>on</strong>tiguous technological volumes (+lO°C).<br />

Fig.4 Calculated Temperature E'ield at<br />

the Baee of Headframe No. 1 for mid-<br />

October; dashes denote the siotherms<br />

for April.<br />

where h, c 1.75 W/(m.;C) is the coefficient<br />

of heat c<strong>on</strong>ducti<strong>on</strong> of frozen ground, and AZ is<br />

The air temperature within the pit shafts that the interval between the points at which the<br />

heat the footing <strong>on</strong> the sides, is +7OC for temperature wae measured, m.<br />

beadframe No. 1. and +2OC Pox headframe No. 2,<br />

iwith the coefficient of c<strong>on</strong>vective heat trans- Stabilizati<strong>on</strong> of the temperature regime of<br />

I) fer <strong>on</strong> the headframe surface being d = 17.4 earth materials at the foundati<strong>on</strong>e begins not<br />

latex than during 10 years of exploitati<strong>on</strong> of<br />

/I iV/( m2 OK).<br />

the structures, and there is <strong>on</strong>ly a minor difference<br />

between the aubsequent temperatures<br />

Boundary C<strong>on</strong>diti<strong>on</strong>s of a cola Period<br />

of earth. materials over a l-yeas cycle for a<br />

Temperature calculati<strong>on</strong>B and ventilati<strong>on</strong> heat 30-year period of forecasting, Therefore, the<br />

measurements are matched by successive appro- Table 2 data corresp<strong>on</strong>d to every year within<br />

ximati<strong>on</strong>s. To begin with, we assume that the the interval indicated.<br />

mean rise in air temperature while moving<br />

through the undexground space is 205e of the va- We determine the total heat losses into the<br />

lue of its subzero temperature; then we calcu- ventilated underground space from the founlate<br />

the heat exchange between the foundati<strong>on</strong> dati<strong>on</strong> earth materials and from the headframe<br />

ana earth materials in the first approximati<strong>on</strong>; building for the period of a single air ex-<br />

The resulto of the calculati<strong>on</strong>, viz. tampera- chan e to be t = 7.56 rnin for the cellar and<br />

ture fielde at the footing, allow us to deter- t = f .59 min for headframes iio. 1 and No. 2,<br />

mine the m<strong>on</strong>thly mean temperature gradients with the throughput of the fane being given.<br />

A8 /Ai! and heat flows within earth materi- Heat losees of earth materials through the axi<br />

als at the foundati<strong>on</strong> footing, <strong>on</strong> the whole symmetrical foundati<strong>on</strong> with its outer surface<br />

(Table 2). The tabular values of heat flows P (Table 1) for a period t, estimated as qH=<br />

are determined from the expreesi<strong>on</strong><br />

=-Z(TcBt, are given in Table 3. The table also<br />

presents heat losses from the headfr'ame I'OQ~ZIS<br />

W a - A, AG/b ,<br />

into the hollow foundati<strong>on</strong> Qe , as dstermined<br />

1237

TABLE 2<br />

Calculati<strong>on</strong> of Beat Flows at the<br />

Headframe Bases (1st Approximati<strong>on</strong>)<br />

Headframe Paratnetere November' December January February March<br />

As/Ait,K/m 4.26 5 * 6'7 5.69 4.38 2.07<br />

No. 1 ZJ , W/n2 -7 - 46 -9.92 -9.96 -7.66 -3.62<br />

"7.72 W/m 2<br />

A f3 /Aa ,K/m 4.55 6.06 6.17 4.93 2.63<br />

No. 2 w*, W/m2 -7.96 -10.61 -10.81 -8.64 -4.60<br />

x.= -8.52 W/m2<br />

* ' I<br />

I<br />

!<br />

I<br />

"_<br />

1-<br />

t<br />

TABLE 3<br />

Parameters of Heat Exohange in Ventilated<br />

Underground Spaces<br />

x<br />

7-<br />

a<br />

".<br />

Fig.5 Calculated Temperature Field<br />

Baae of Headframe Iio. 2 for Mid-October;<br />

dashes denote the isotherms for April.<br />

I - c<strong>on</strong>tour of the "equivalent11 layer.<br />

I<br />

at the<br />

by normalizing methode of c<strong>on</strong>atructi<strong>on</strong> heat<br />

engineering,as well as the temperature difference<br />

averaged over the time interval of t3. single<br />

air exchange in the volume VI: AB =<br />

= ( q.+ Qe )/ c ~ V ,. Unlike the CH,n II-3-'79<br />

technique, taking into account the n<strong>on</strong>-stati<strong>on</strong>arity<br />

of heat exchange at the time of cooling<br />

of the inner found ti<strong>on</strong> structures with a volume<br />

of 400 and '72 m 4 of headframos No. 1 and<br />

1238<br />

No. 2 increases the t~mperafure-differences in<br />

the air to a value A8 . In order to rehder<br />

the temperature of the aLr aurxounding the foundati<strong>on</strong><br />

from inlslde more exact, it La neceesary<br />

to specify more exactly the coefficient<br />

of heat transfer that is originally taken the<br />

same as that in the shaft. Heat tranefer from<br />

the cellar floor La cowiaered to be a total<br />

<strong>on</strong>e, owing to the forced horiz<strong>on</strong>tal movement<br />

of the air and free c<strong>on</strong>vecti<strong>on</strong> vertically because<br />

the cooled surface of the foundati<strong>on</strong> plate<br />

faces"upwaxd. Heat transfer in the cam of<br />

forced flow round the plate is characterized<br />

by the Merkel functi<strong>on</strong> (Shosin, 19471:<br />

NU a 0.0568Pe 0.78 , (4)<br />

where Pe ia the Pecl& number. Hence, from (2)<br />

and (4) the coefficient of c<strong>on</strong>vective heat<br />

trEinsfer in the case of forced air cooling<br />

al<strong>on</strong>g the length E- 35 m for the foundati<strong>on</strong><br />

of headframe NO. I is de= h *Nu/, 0.56 w/<br />

/(m2.K).<br />

Free air C<strong>on</strong>veFti<strong>on</strong>, with the valuesl of the<br />

Graahoi and Prandtl numbers being 2-107 e<br />

r Gr*Pr -= 1 1012, is described -,according<br />

to M.A.likheev (Shorin, 1952) - by a functi<strong>on</strong><br />

of the form (1) with the coefficient 1.35.<br />

Therefore, as in the cme c<strong>on</strong>aidered above,<br />

with the actual value of Er*Pr = 5.9~109, the<br />

size of the vertical c<strong>on</strong>vectl<strong>on</strong> z<strong>on</strong>e are not<br />

involved in describing the process, and the<br />

value of the coefficient of c<strong>on</strong>vective heat<br />

transfer by formula (3 with a correcti<strong>on</strong> of<br />

1.35 is dc- 5.38 W/(m 3 .K).<br />

On the other hand, according to results<br />

repor-

ted by Griffits and navies (Shorin, 1947), the<br />

coefficient of c<strong>on</strong>vective heat transfer in the<br />

air of horiz<strong>on</strong>tal plates, with their heated<br />

surfaces facing upward, ish<br />

frame and axe quite unusual because of a lateral<br />

heat source and the absence of the seaso-<br />

Because both estimates of free c<strong>on</strong>vecti<strong>on</strong> do nally unfrozen layer, October has been taken<br />

not differ significantly, the total coefficient as the calcuLated m<strong>on</strong>th for which the temperatures<br />

of earth materials are the greatest.<br />

of c<strong>on</strong>vective heat transfer <strong>on</strong> the inner curface<br />

of the foundati<strong>on</strong>s is taken to be: d = Temperature fields at the base of the headfra-<br />

= dm + d, x 6.0 W/(m<br />

2<br />

mes in October as well a8 for the coldest<br />

.K).<br />

m<strong>on</strong>th (April) are presented in Figs 4 and 5.<br />

The more precise boundary c<strong>on</strong>diti<strong>on</strong>s permit us<br />

to calculate the temperature fields at the<br />

headframe basas in the sec<strong>on</strong>d approximati<strong>on</strong><br />

aB well aB the relevant heat flows at fo- the<br />

undati<strong>on</strong> footing (see Table 4).<br />

TABLE 4<br />

stability of a natural permafrost situati<strong>on</strong>,<br />

are specified at the upper edge of the regi<strong>on</strong><br />

(Guryanov and Demchenko, 1984). Temperature<br />

fluctuati<strong>on</strong>s of earth materials are attributab<br />

le to the influence of the shaft and the head-<br />

The figures show that the permafrost boundary<br />

undergoes seas<strong>on</strong>al variati<strong>on</strong>s <strong>on</strong>ly at the cen<br />

ter of the foundati<strong>on</strong>s but rsmaine unchanged<br />

in its principal part that produces a c<strong>on</strong>ic<br />

surface within the mass al<strong>on</strong>g the shaft.<br />

Calculati<strong>on</strong> of Heat Flows at the Headframe Bases (2nd Approximati<strong>on</strong>)<br />

Headframe Parameters November December January February March<br />

A 8 /A2 ,K/m 2.51 4.53 5.18 4.37 2.40<br />

NO. I W, W/m2 -4 39 -7.93 -9.06 -7.65 -4.20<br />

Wc = -6.65 I/m 2<br />

A fl/AZ,K/m 3.17 5.13 5.73 4.07 2 .a4<br />

NO. 2 v, W/m2 -5 55 -9.00 -10.04 -0.53 -4.97<br />

x= -7.62 #/m2<br />

The difference in values of heat flowa of the The calculati<strong>on</strong>a have astabliahed that beneat<br />

1st and 2nd approximati<strong>on</strong>s (Tables 2 and 4) the footing of box foundati<strong>on</strong>s which are venleads<br />

to changes in the calculated temperatu- tilated with cold outdoor air, there forma a<br />

re of the Poroed air by not more 0.3OC, than z<strong>on</strong>e of stable subzero temperatures a8 low as<br />

which aoes not exceed the accuracy to which it -6OC at the base of headframe No. 1 (Fig. 4)<br />

ia specified and c<strong>on</strong>trolled. Therefore, the and -4OC at the base of headframe No. 2 (Pig.<br />

2nd approximati<strong>on</strong> boundary c<strong>on</strong>diti<strong>on</strong>s axe fi- 5). Toward the end of the warm period the z<strong>on</strong>e<br />

nal.<br />

of unfrozen ground immediately at the footin<br />

of the foundati<strong>on</strong>s expands as much as <strong>on</strong>e-<br />

Calculated Temperature Regime of Eaxth Mate- third of its size. However, most of the foorial<br />

8<br />

ting area (more than 80%) ia c<strong>on</strong>stantly sup-<br />

The soluti<strong>on</strong> of the problem of c<strong>on</strong>ductive heat ported by frozen earth materials low with subtransfer<br />

in earth materiaie has been carried zero temperature, i.e., with a given ventilaout<br />

numerically by a niethod of heat balances, ti<strong>on</strong> regime the c<strong>on</strong>diti<strong>on</strong>s for surface and<br />

with proper account of phase transformati<strong>on</strong>s melt water infiltrati<strong>on</strong> into the base of the<br />

of ground moiature at OOC. The vertical cxoss- headframes and al<strong>on</strong>g the shafts are ruled ou<br />

secti<strong>on</strong> of a cylindrical calculated regi<strong>on</strong> is<br />

rectangular in shape with a hollow at the ori- Load-Carrying Capacity of Headframe Bases<br />

gin of coordinates corresp<strong>on</strong>ding to the foun- Estimating the load-carrying capacity of the<br />

dati<strong>on</strong> c<strong>on</strong>figurati<strong>on</strong>. Separati<strong>on</strong> into calcula- bases is complicated by a multitude of factors,<br />

ted blocks near the foundati<strong>on</strong>s is shown in namely the n<strong>on</strong>uniform temperature field, irre-<br />

Pigs 4 and 5. The depth (89 m) and the radius . gular variati<strong>on</strong> of the characteristics of<br />

(IO7 m) of the calculated regi<strong>on</strong> rule out the earth nlateriale, and arbitrary durati<strong>on</strong> of the<br />

heat flows outwards.<br />

loade. Therefore, bearing in mind predomi- the<br />

nance of clayey ground with low internal fri<br />

In the foregoing discussi<strong>on</strong>, we have described ti<strong>on</strong>, our c<strong>on</strong>siderati<strong>on</strong> has incorporated <strong>on</strong>ly<br />

the boundary o<strong>on</strong>diti<strong>on</strong>s for c<strong>on</strong>tact with the <strong>on</strong>e, generalized characteristic of frozen<br />

Poundati<strong>on</strong>. The coefficient of c<strong>on</strong>vective heat ground, vie. the equivalent, marginally l<strong>on</strong>g<br />

transfer and the temperature in the shaft (3rd b<strong>on</strong>d C . Table 5 gives the calculated values<br />

-kind boundary c<strong>on</strong>diti<strong>on</strong>s) are specified for of the b<strong>on</strong>d taking into account experimental<br />

the c<strong>on</strong>four of the supports. The surface tempe- results <strong>on</strong> earth materials -3OC at a8 well an<br />

rature of round and snow (1st-kind boundary the functi<strong>on</strong>al. dependence of their strength<br />

c<strong>on</strong>diti<strong>on</strong>ay, verified via a calculati<strong>on</strong> for <strong>on</strong> temperature according to CHnllJ-18-76.<br />

1239<br />

\

TABLE 5<br />

Equivalent B<strong>on</strong>d of Earth Materials as a Functi<strong>on</strong><br />

of Temperature<br />

8, OC -0.3 -0.5 -1.0 -1.5 -2.0 -3.0 -4.0 -5.0 -6.0<br />

c, kPa 160 240 340 420 480 . 600 680 760 840<br />

The main load-carrying structures of box foundati<strong>on</strong>s<br />

which ensure their bend stability at<br />

the time of thawing of the central z<strong>on</strong>e of the<br />

base, are l<strong>on</strong>gitudinal wall beanie of the foundatl<strong>on</strong>e<br />

al<strong>on</strong>g axes 2 and 4 of headframe No. 1<br />

(Fig. 2) and al<strong>on</strong>g axes 1 and 3' of headframe<br />

No. 2 (Fig. 3). The beam structures prsdetermine<br />

the investigati<strong>on</strong> of the load-carrying<br />

capacity of the bases for plane deformati<strong>on</strong><br />

and, hence, the transiti<strong>on</strong> to actual dimensi<strong>on</strong>s<br />

of the foundati<strong>on</strong>s. Plane deformati<strong>on</strong> in<br />

the presence of an axisymmetrical temperature<br />

fleld is advantageous as the approximati<strong>on</strong><br />

that underrates the load-carrying capacity.<br />

The load-carrying capacity of headframe bases<br />

was investigated numerically al<strong>on</strong>g trajectoriee<br />

of marginal shears of a disc<strong>on</strong>tinuoua soluti<strong>on</strong><br />

of the problem of plaeticity theory for<br />

a wedge. This soluti<strong>on</strong> yielda the expressi<strong>on</strong><br />

for limiting distributed load normal to the<br />

side of an acute-angle wedge with the opening<br />

2d (Rabotnov, 1979;:<br />

f = 2C (1 - C OSW j. (5)<br />

The oharacteristics of the defining equati<strong>on</strong>s<br />

of the problem (sliding lines) lie in the<br />

field of soluti<strong>on</strong>s at the angle of 45O to the<br />

side of the wedge. The bisectrix of the angle<br />

2d is the disc<strong>on</strong>tinuity line of normal stresses.<br />

The opening angles of the calculated<br />

wedge have been determined from the slope of<br />

the zero isotherm: d = 36O40' fox headframe<br />

No. 1 and d P 40°50' for headframe No. 2.<br />

Calculated schemes for foundati<strong>on</strong>s axe presented<br />

in b'igs 6 and '7. The diagrams of limiting<br />

shear stresses T,, calculated from the actual<br />

temperature of earth materials as well as equivalent<br />

b<strong>on</strong>d according to Table 5, are'c<strong>on</strong>structea<br />

al<strong>on</strong>g the sliding lines marked at 1 m intervals<br />

horiz<strong>on</strong>tally, starting from the edge of<br />

the foundati<strong>on</strong> footing. The character of the<br />

diagrams indicates that the n<strong>on</strong>uniformity Of<br />

the stress field within the ground.maas is<br />

Lower as compared with the n<strong>on</strong>uniformity of<br />

the temperature field.<br />

Diagrams of limiting pressurea 9, equal to<br />

the vertical projecti<strong>on</strong> of increments of total<br />

stresses <strong>on</strong> the characteristics, are plotted<br />

in Pigs 6 and 7 for the total load-carrying<br />

capacity of the bases /1/ and for additi<strong>on</strong>al<br />

pressurea /2/ as the differences of the loadcarrying<br />

capacity and own weight of earth ma-<br />

On inserting the mean equivalent b<strong>on</strong>d of the<br />

base E as the ratio of total resistence to<br />

shear al<strong>on</strong>g the characteristics to their length<br />

it is easy to find, using formula IS), the theoretical<br />

value of limiting load 9 <strong>on</strong> the base<br />

terials. Their values were used for calculating<br />

the limiting pressures fox equal-sized<br />

rectangular dingxarns which average curvilinear,<br />

-total yc, and additi<strong>on</strong>al g,, <strong>on</strong>es (Table 6).<br />

1240<br />

pig.6 Calculated Scheme for Limiting<br />

Equilibrium in Earth lateriala of the<br />

Base of Headframe No. 1.<br />

The diagrame of limiting shear streesea<br />

axe plutted at the sliding lines, and<br />

the diagrams of limiting preasures axe<br />

plotted al<strong>on</strong>g the foundati<strong>on</strong> footing.<br />

I<br />

2 - total limiting pressure;<br />

additi<strong>on</strong>al pressure.<br />

TABLE 6<br />

Calculated Pressures Below Foundati<strong>on</strong><br />

Footing of Headframes, kPa

for a stripe of a breadth of 1 m.<br />

In Table 6 the quantity m - ec,/q is the measuxe<br />

of closeness of the calculated scheme to<br />

ita theoretical analogue and, while being leas<br />

than unity, is aL~o the safety coefficient of<br />

limiting pressure. The values of I -m are twice<br />

&a small aa root-mean-rrquare departures of<br />

the caloulated diagrams ZnP from theoretical<br />

<strong>on</strong>es, l.e., numerical aoluti<strong>on</strong>s <strong>on</strong> the chaxactexisticsl<br />

possess a c<strong>on</strong>vergence margln. The<br />

reliability of the foundati<strong>on</strong>-base system is<br />

evaluated by the ratio of limiting presaure<br />

qC2to mean stress p beneath the footing of<br />

the support z<strong>on</strong>e from c<strong>on</strong>atant and temporal<br />

loade: k IP 9 c2 /p . In comparis<strong>on</strong> with the mean<br />

coefficient of reliability (Table 6) its values<br />

from marginal preaaueea at the edge of the<br />

talik (Figs 6 and 7) pxedeterrnini the overall<br />

limiting state , are higher: k = 227 and k<br />

= 3.78. Thus, mhematixati<strong>on</strong> of the calculati<strong>on</strong>s<br />

that combines soluti<strong>on</strong>s of the problem8<br />

of a different dimensi<strong>on</strong>al representati<strong>on</strong> is<br />

justified in view of the high value6 of the<br />

reliability coefficient.<br />

Tabla 7 compares the total coat estimates of<br />

two variants of foundati<strong>on</strong>s that were worked<br />

out in the design of an underground mine.<br />

TABLE 7<br />

Fig.7 Calculated Scheme ror Limiting<br />

Equilibrium in Earth Materiale at the<br />

Base of Headframe No. 2. POP explanati<strong>on</strong>o<br />

refer to Fig. 6.<br />

Capital Outlays for C<strong>on</strong>structi<strong>on</strong> of Foun- wing of earth materials at the footing is rule<br />

dati<strong>on</strong>s, Thousands of Roubles<br />

out, owing to the large own mass of the cooled<br />

roundati<strong>on</strong>s whlch is advisable to increase ,<br />

round the periphery of the footing.<br />

Headframe Pilee foundati<strong>on</strong>s Box foundati<strong>on</strong>s 3. The permafrost that is boundad ox partially<br />

supported by an unfrozen z<strong>on</strong>e, ax0 able to ~er-<br />

No. 1 3 413.9 1 002.6<br />

ve aa a safe base, provided that the tempexs-<br />

No. 2 302.4 359 3<br />

fure stability, in c<strong>on</strong>juncti<strong>on</strong> with the c<strong>on</strong>f<br />

gurati<strong>on</strong> of the frosen mass at the base of the<br />

structure, is determined by the etrctural-andtechnological<br />

design of the foundati<strong>on</strong>e. With<br />

such an approach, the stability of the ba8e<br />

For the mine as a whole, box foundati<strong>on</strong>s of the and the reliability of the foundati<strong>on</strong>s are<br />

headframes guarantee a decrease in investments both, guaranteed.<br />

by 2 434.4 thousands of roubles &a well as in<br />

annual exploitati<strong>on</strong> costa by 100 thousands of<br />

roubles. However, whereas for headframelweighing<br />

173 MN the increaae in cost of the founda- REFERENCES<br />

ti<strong>on</strong>s i~l very substantial, ox by 3,4 times,<br />

then for headframe No. 2 weighing 53 MN it Is CHHII 11-18-76, (1977). Osnovaniya i fundamenty<br />

<strong>on</strong>ly 6% because for light-weight headframee, na vechnomerzlykh gmntakh, 46 p., Moscow:<br />

the desired increase in the volume of ventila- Striizdat.<br />

ted underground spaces becomes unprofitable.<br />

CHH~ 11-3-79, (1979). Stritel'naya teplotekhnika,<br />

32 p., Moscow: Striizdat.<br />

Graber, G., Erk, S. and Grigull, W. (1958).<br />

CONCLUSIONS<br />

Osnovy ucheniya o teploobmene, 566 p.,<br />

Moscow: Izd. inostr. liter.<br />

1. Structures of box foundati<strong>on</strong>s, ventilated<br />

with the outdoor air during the wintertime, gua-<br />

Guryanov, I.E. and Demchenko, R.Ya. (1984).<br />

rantee the required temperature regime of the<br />

Merzlye grunty pri inzhenernykh vozdeietviyakh,<br />

106-116, Novosibirsk: Nauka.<br />

permafrost at the base as well aa ita stability.<br />

These are advantageous foundati<strong>on</strong>e because lo- Novikov, F.Pa. (1959). Temperaturny rezhlm merads<br />

<strong>on</strong> the base are transmitted directly by the zlykh gornykh porod za krepyu ehakhtnykh<br />

load-carrying box of the cellar, and the lower StVUlOv, 98 p.9 MOSCOW: Izd. AN SSSR.<br />

stages of the cellar lie at technological Levels,<br />

without the need to lift them, which is<br />

Rabotnov, Yu.N. (1979). Pekhanika deformiruem<strong>on</strong>eeded<br />

in the case of a surface ventilated cel- go tverdogo tela, 744 pa, Moscow: Nauka.<br />

lar.<br />

Shorin, S.N. (1947). Teploperedacha, 227 p.,<br />

2. During a warm period of the year, the tha-<br />

Izd.min.kom.khoz. (19521, Ibid. 339 p.,<br />

Goastriizdat. Moscow-Leningrad.

ASSESSMENT OF KEY DESIGN ASPECTS OF A 150 FOOT<br />

HIGH EARTH DAM ON WARM'PERMAFROS'F<br />

T.A. Hammerl, T.C. Krzewinskiz and G.G. Booth3<br />

IDarnes & Moore, Portland, Oreg<strong>on</strong><br />

ZLakehead Testing Laboratory, Duluth, Minnesota<br />

JCominn, Alaska, Anchorage, Alaska<br />

SYNOPSIS Recently a 150 foot (50 meter) high earth dam embankment was designed to be built in an<br />

area underlain by relatively warm permafrost. Since few earth dams of this size have been c<strong>on</strong>structed<br />

<strong>on</strong> permafrost, special design details and a positive performance m<strong>on</strong>itoring scheme were incorporated<br />

in the design. This paper presents some design parameters, criteria and aspects unique to '<br />

warm permafrost envir<strong>on</strong>ment. Primary site selecti<strong>on</strong> and the geotechnical investigati<strong>on</strong>s are also<br />

covered in the paper.<br />

INTRODUCTION<br />

Development of the Cominco Alaska, Incorporated<br />

(CAI) Red Dog Mine will require the c<strong>on</strong>structi<strong>on</strong><br />

of a sea port with port facilities, a 54 mile<br />

l<strong>on</strong>g access road between the port and the ore<br />

deposit, and the mine facilities which include<br />

a tailings dam, water supply dam, mill facilities<br />

and waste c<strong>on</strong>tainment areas for waste<br />

material. In 1982, a preliminary boring program<br />

was performed for the purpose of selecting<br />

mine support facility locati<strong>on</strong>s. With this<br />

data, the locati<strong>on</strong> of the tailings dam was selected.<br />

From June through August, 1984, Dames &<br />

Moore carried out the sec<strong>on</strong>d of several geotechnical<br />

investigati<strong>on</strong>s at the proposed sites as<br />

well as investigated site alternatives for the<br />

Red Dog Mine facilities. During 1984, the tailings<br />

dam was investigated with a boring and<br />

testing program performed to obtain design level<br />

geotechnical data (Dames & Moore, 1984). A 150<br />

foot high earth tailings dam embankment was subsequently<br />

designed. Incorporated into the design<br />

was the fact that the dam was to be built<br />

<strong>on</strong> relatively warm permafrost (Dames & Moore,<br />

1987). The design included instrumentati<strong>on</strong> of<br />

the dam to m<strong>on</strong>itor performance of the embankment<br />

throughout its design life. Figure 1 i s a<br />

detailed site plan of the tailings dam embankment<br />

and its associated seepage collecti<strong>on</strong> dam.<br />

GEOLOGY<br />

basin. Near-shore clastics and open marine<br />

carb<strong>on</strong>ates were deposited from Dev<strong>on</strong>ian to<br />

early Mississippian times. In the late Mississippian,<br />

an extreme carb<strong>on</strong>ate platform c<strong>on</strong>taining<br />

a large black shal-e basin (including the<br />

Red Dog Deposit) developed. Turbidite flows,<br />

tuffaceous sediments and volcanic rock indicate<br />

tect<strong>on</strong>ic and magmatic activity also occurred<br />

during this time. Stable marine c<strong>on</strong>diti<strong>on</strong>s<br />

existed from the Pennsylvanian through the<br />

early Jurassic and resulted in the formati<strong>on</strong> of<br />

shales, cherts, and limest<strong>on</strong>es. Extensive tect<strong>on</strong>ic<br />

activity occurred from the Jurassic to<br />

the late Cretaceous. Thick flysch sequences<br />

accumulated in the newly formed basins and<br />

troughs, The detritus was from systect<strong>on</strong>ic<br />

volcanoes and the-uplifted Paleozoic rocks.<br />

Afterwards, several periods of over-thrusting<br />

occurred, whereby plates of near-surface rocks<br />

were thrust over each other. The cumulative<br />

northward displacement exceeded 150 miles (265<br />

Kilometers) in the regi<strong>on</strong>, These thrust plates<br />

were highly deformed by tight folds and lowangle<br />

thrusts. These events, al<strong>on</strong>g with<br />

erosi<strong>on</strong>, resulted in the formati<strong>on</strong> and topography<br />

of the De L<strong>on</strong>g Mountains.<br />

The proposed tailing dam <strong>on</strong> South Fork Red Dog<br />

Creek is underlain by interbedded Cretaceous<br />

shale and sandst<strong>on</strong>e. The dark grey to brown<br />

sandst<strong>on</strong>e appears as boudins (or "sausage"<br />

shapes) within the dark gray shale matrix.<br />

Slickensides are comm<strong>on</strong> throughout the formati<strong>on</strong><br />

in this area.<br />

The Red Dog Mine project site is located at<br />

approximately Latitude 67" h6' north and<br />

L<strong>on</strong>gitude 162" 58' west in the De L<strong>on</strong>g Mountains<br />

of northwestern Alaska. Elevati<strong>on</strong>s in the site<br />

area range from 750 feet (250 meters) above MSL<br />

al<strong>on</strong>g Red Dog Creek to more than 2,000 feet<br />

(667 meters) above MSL <strong>on</strong> the western side of<br />

Red Dog Valley.<br />

The northeast-trending<br />

extensively deformed,<br />

sediments deposited du<br />

regressive cycle in a<br />

GEOTECHNICAL INVESTIGATIONS<br />

The general area where the tailings dam embankment<br />

will be c<strong>on</strong>structed was first drilled in<br />

1982 when three borings were advanced at the<br />

locati<strong>on</strong>s indicated <strong>on</strong> Figure 1. In 1984, 10<br />

additi<strong>on</strong>al borings were advanced within the<br />

De L<strong>on</strong>cl Mountains include footprint of the dam for the purpose of obtainlate<br />

Paieozoic to Mesozoic ing design level subsurface data. Both vertical<br />

ring a transgressive-<br />

and inclined boreholes were augered and/or<br />

large intrac<strong>on</strong>tinental cored to depths ranging from 30 to 150 feet<br />

1242

(IO to 50 meters) for the purpose of logging<br />

subsurface soil and thermal c<strong>on</strong>diti<strong>on</strong>s, measuring<br />

in-situ soil and rock permeabilities, and<br />

obtaining undisturbed soil and rock samples for<br />

identificati<strong>on</strong> and laboratory testing.<br />

SITE CONDITIONS<br />

The proposed locati<strong>on</strong> of the tailings dam wil<br />

be across the south fork of Red Dog Creek<br />

approximately 1,100 feet (367 meters) upstream<br />

(south) from the c<strong>on</strong>fluence with the main branch<br />

of Red Dog Creek. The site plan <strong>on</strong> Figure 1<br />

c<strong>on</strong>tains c<strong>on</strong>tour lines which show general topographic<br />

and drainage features of the area. Bedrock<br />

outcrops are present al<strong>on</strong>g the west side of<br />

the creek.<br />

Vegetati<strong>on</strong> at the site c<strong>on</strong>sists mainly of a low<br />

growir!g, well-drained tundra mat with low bush<br />

vegetati<strong>on</strong> growing near and al<strong>on</strong>g the creek.<br />

Bedrock outcrops and exposed colluvial soils<br />

are present al<strong>on</strong>g the steeper areas and alluvial<br />

deposits are exposed within the creek channel.<br />

SUBSURFACE CONDITIONS<br />

The borings revealed that a similar general<br />

subsurface profile exists throughout the site,<br />

which can be described as follows. The three<br />

borings <strong>on</strong> the west side of the creek, but not<br />

within the creek floodplain (SS-5-84, SS-6-84<br />

and SS-7-84) revealed a profile c<strong>on</strong>sisting of<br />

1/4 to two feet (8 to 60 cm) of Peat or organic<br />

silt over five to seven feet (1.7 to 2.3 meters)<br />

of highly weathered bedrock which graded more<br />

competent with depth. The weathered z<strong>on</strong>e<br />

(upper eight feet-2.7 meters) c<strong>on</strong>tained a large<br />

quantity of excess ice (to 60%).<br />

The two borings within the creek floodplain<br />

(SS-8-84 and SS-12-84) encountered a four to<br />

eight foot (1.3 to 2.2 meter) alluvial layer<br />

above the bedrock, The alluvium at boring<br />

SS-8-84 was cleaner (GP) than that found in<br />

55-12-84 (GM), which is to be expected since<br />

SS-8-84 was within the present creek channel<br />

while $5-12-84 was slightly to the south of the<br />

existing creek channel.<br />

The three borings <strong>on</strong> the east side of the creek<br />

(SS-9-84, SS-10-84 and SS-11-84) revealed a<br />

profile c<strong>on</strong>sisting of zero to four feet (6 to<br />

1.3 meters) of peat and organic silt over four<br />

to fifteen feet (1,3 to 5 meters) of colluvial<br />

soils over weathered bedrock which graded more<br />

competent with depth. Going upslope (east) the<br />

peat and colluvial layers decreased in thickness.<br />

The bedrock encountered in all the borirlgs. c<strong>on</strong>sisted<br />

of graylblack shales interbedded with<br />

sandst<strong>on</strong>e. Joints and fractures generally filled<br />

with calcite were present in the rock. Numerous<br />

gouge z<strong>on</strong>es were also present throughout<br />

the bedrock strata, but appeared to be disc<strong>on</strong>tinuous<br />

within the site area drilled.<br />

The near surface soils were frozen in a1 1 boreholes<br />

drilled. The so ils above the competent<br />

bedrock surface genera lly c<strong>on</strong>tained visible ice<br />

which occurred as individual ice crystals or inclusi<strong>on</strong>s,<br />

ice coatings <strong>on</strong> particles, as random<br />

or irregularly oriented ice formati<strong>on</strong>s, or as<br />

ice lenses greater than <strong>on</strong>e-inch (2.5 cm) thick.<br />

The per,centage ice, by volume, ranged from 4%<br />

to 60% (soils <strong>on</strong> the west side of the creek c<strong>on</strong>tained<br />

a much higher percentage of ice than the<br />

soils located <strong>on</strong> the east side). Borings SS-8-<br />

84 and SS-12-84 are located within the creek's<br />

thaw bulb and were found to be unfrozen below a<br />

depth of about 30 feet (IO meters) and eight<br />

feet (2.7 meters) respectively. Some visible<br />

ice was noted within the intact bedrock above a<br />

depth of about 30 fe,et (IO meters) but the<br />

frozen bedrock generally did not c<strong>on</strong>tain visible<br />

ice.<br />

LABORATORY TESTING<br />

Soil samples were tested to classi'fy the soils,'<br />

encountered and determine thetr physical and<br />

engineering characteristics. The laboratory<br />

testing program included sample inspecti<strong>on</strong>,<br />

sample photography, soil classificati<strong>on</strong>,<br />

moisture-density measurements, mechanical and<br />

hydrometer grain-site analyses, Atterberg limits<br />

tests, c<strong>on</strong>stant head permeability tests, thaw<br />

c<strong>on</strong>solidati<strong>on</strong> tests and direct shear and triaxial<br />

shear strength-tests.<br />

FOUNDATION MATERIALS<br />

Soils: Three classificati<strong>on</strong>s o-f soils were encountered<br />

across the site which are 1) surficial<br />

silts and organics, 2) colluvial soils, and 3)<br />

alluvium. Since all surficial silts and organics<br />

wjll be stripped prior to placement of the<br />

fills, properties of those materials were not<br />

determined. A battery of laboratory tests were<br />

performed <strong>on</strong> the colluvial and alluvial soils,<br />

the highly weathered bedrock and embankment<br />

material (Borrow) to determine the average physical<br />

and engineering properties.<br />

THERMAL CONDITIONS<br />

A total of ten thermistor strings have been installed<br />

at the tailings dam site for the purpose<br />

of m<strong>on</strong>itoring ground temperatures. The<br />

data Indicates the area is underlain by very<br />

warm permafrost with temperatures an the east<br />

abutment rangin from about 30'F to 31.5"F<br />

(-0.3 to -1.l'CT. The west abutment ground<br />

temperatures are somewhat colder (27'F/-2.8OC<br />

at depth) which is probably due to the more<br />

northerly exposure of the west abutment, Two<br />

thermistor strings located in the creek floodplain<br />

indicate the creek's thaw bulb is about<br />

60 feet (20 meters) deep.<br />

DESIGN CONSIDERATIONS<br />

Several design c<strong>on</strong>cerns were identified relative<br />

to specific site c<strong>on</strong>diti<strong>on</strong>s. They were<br />

the extreme climatic c<strong>on</strong>diti<strong>on</strong>s, the poor properties<br />

of the near-surface foundati<strong>on</strong> materials<br />

and the availability of c<strong>on</strong>structi<strong>on</strong> material.

. ><br />

L<br />

FIG. 1 TAILINGS DAM SITE PLAN AND INSTRUMENT LOCATIONS<br />

'\<br />

Climatic c<strong>on</strong>diti<strong>on</strong>s at the site dictate that a<br />

material was not available in significant quanstrict<br />

c<strong>on</strong>structi<strong>on</strong> schedule be followed, Foun-<br />

tities, so a synthetic liner design was utilized<br />

dati<strong>on</strong> excavati<strong>on</strong> and backfilling for starter<br />

to c<strong>on</strong>trol seepage loss through and beneath the<br />

dam, seepage collecti<strong>on</strong> dam and cutoff trenches, dam.. The synthetic liner will cover the upas<br />

well as c<strong>on</strong>structi<strong>on</strong> of the temporary diver- stream face of the dam and will also be extended<br />

si<strong>on</strong> dam will be completed during the winter<br />

into a trench cut into rock to minimize seepage<br />

c<strong>on</strong>structi<strong>on</strong> seas<strong>on</strong> which normally runs November under the embankment. A 100-mil-thick high<br />

to May. The fill placement and compacti<strong>on</strong> for<br />

density polyethylene liner was selected for use<br />

various comp<strong>on</strong>ents of the tailing dam will be<br />

as the impermeable liner. As a safety factor<br />

performed during winter m<strong>on</strong>ths, which dictates<br />

against the unlikely situati<strong>on</strong> where leaks formthat<br />

careful quality c<strong>on</strong>trol procedures must be ed in the liner, a filter drain was designed<br />

followed.<br />

al<strong>on</strong>g the entire upstream slope so any seepage<br />

through the liner and into the filter drain<br />

Because the stability of the tailing embankment will be removed by pumpback wells.<br />

secti<strong>on</strong> may be affected under thawing c<strong>on</strong>diti<strong>on</strong>s,<br />

certain design features had to be c<strong>on</strong>sidered.<br />

The dam was designed to be c<strong>on</strong>structed in six<br />

Near-surface soil and highly weathered shale<br />

stages as illustrated <strong>on</strong> Figure 2. To minimize<br />

foundati<strong>on</strong> material c<strong>on</strong>tain ice and, when thawed, the impact of thaw strain or creep settlement,<br />

will have relatively low strength and high com-<br />

Stage 1 was designed to be c<strong>on</strong>structed <strong>on</strong> a<br />

pressibility. Should thawing occur, excess pore.<br />

foundati<strong>on</strong> excavated to competent bedrock.<br />

If<br />

pressures may be experienced during the time<br />

settlement was allowed to occur al<strong>on</strong>g the upimmediately<br />

following loading induced by embank- stream face of the dam, damage and/or rupture<br />

ment placement, Thus, either the embankment<br />

of the liner could occur.<br />

secti<strong>on</strong> will require relatively gentle side<br />

I<br />

slopes or the near-surface soils and upper, ice-<br />

A knowledge of the thermal regime of the tailing<br />

rich shales must be removed.<br />

dam and impoundment area is necessary for proper<br />

design in a permafrost z<strong>on</strong>e, The tailing dam<br />

Adequate borrow for c<strong>on</strong>structi<strong>on</strong> of the embank- has been designed with a synthetic liner coverment<br />

was located and is therefore not a major<br />

ing the upstream face, as well as with a cutoff<br />

c<strong>on</strong>cern. However, suitable impervious core<br />

trench through the upper foundati<strong>on</strong> materials,<br />

1244

FIG. 2 TAILINGS DAM SECTION STAGED TO MAXIMUM HEIGHT<br />

and thus is c<strong>on</strong>sidered to be a relatively impervious<br />

dam c<strong>on</strong>structed over a permafrost foundati<strong>on</strong>.<br />

For this type of c<strong>on</strong>structi<strong>on</strong>, it was antfcipated<br />

that thaM penetrati<strong>on</strong> would be mainly<br />

downward below the reservoir and the upstream<br />

slope, and laterally from the reservoir into the<br />

structure and foundati<strong>on</strong>. Furthermore, permafrcst<br />

c<strong>on</strong>diti<strong>on</strong>s wil gradually advance into the<br />

dam secti<strong>on</strong> over the life of the operati<strong>on</strong>.<br />

Modeling the thermal regime i s complex due to<br />

the interacti<strong>on</strong> of many factors, combined wjth<br />

the fact that some phenomena affecting the thermal<br />

state such as seepage volumes and heat Input<br />

from tailings are not well defined. These thermal<br />

changes are further complicated by the proposed<br />

stage c<strong>on</strong>structi<strong>on</strong> of the dam which may<br />

occur over a period of ten years or more.<br />

Because of the anticipated permafrost degradati<strong>on</strong>,<br />

seepage underflow was an important c<strong>on</strong>siderati<strong>on</strong>.<br />

A seepage analysis was performed under<br />

the c<strong>on</strong>servative assumpti<strong>on</strong> that a n<strong>on</strong>-frozen<br />

z<strong>on</strong>e wil exlst beneath the cutoff extending to<br />

a depth of 50 feet (17 meters). The seepage<br />

analysis c<strong>on</strong>sidered the presence of n<strong>on</strong>-frozen<br />

z<strong>on</strong>es within the streambed prior to dam c<strong>on</strong>structi<strong>on</strong>.<br />

Based <strong>on</strong> the maximum calculated seepage<br />

flows from material underlying the tailings p<strong>on</strong>d<br />

bottom, a toe drainage pipe system was incorporated<br />

into the design.<br />

ENGINEERING ANALYSIS<br />

The stability of the proposed tailing dam was<br />

evaluated for static and seismic c<strong>on</strong>diti<strong>on</strong>s<br />

using the computer program STABLZ. Stability<br />

analyses were performed <strong>on</strong> critical secti<strong>on</strong>s o'f<br />

the dam to determine the minimum width of foundati<strong>on</strong><br />

excavati<strong>on</strong> required and to evaluate different<br />

slope c<strong>on</strong>figurati<strong>on</strong>s for various stages of<br />

dam c<strong>on</strong>structi<strong>on</strong>. Based <strong>on</strong> these analyses, it<br />

was computed that the starter dam (upstream and<br />

downstream faces) and the upstream face of the<br />

main dam could be safely c<strong>on</strong>structed at a slope<br />

of 2:l with varying degrees of soil excavatipn.<br />

Similarly, the downstream face of the main dam<br />

could be safely c<strong>on</strong>structed at a slope of 4:l.<br />

The soil properties outlined earlier were used<br />

in the analyses. A design horiz<strong>on</strong>tal earthquake<br />

accelerati<strong>on</strong> of 0.059 was used for the dynamic<br />

analyses.<br />

Excess pore fluid pressures are expected to<br />

develop in the foundati<strong>on</strong> soils with placement<br />

of embankment fill. This increase in pore fluid<br />

pressure is related to the height of fill by<br />

the single parameter Ru. An Ru value is defined<br />

as the ratio between: 1) the total pore water<br />

pressure, and 2) the wet unit weight of a material<br />

times the height of material above the point<br />

under c<strong>on</strong>siderati<strong>on</strong>. For these analyses, the<br />

excess pore pressure developed during thawing<br />

was taken to be equivalent to 66% of the total<br />

height of fill in areas where c<strong>on</strong>structi<strong>on</strong> of<br />

the dam will be over ice-rich colluvial soils.<br />

The two loading c<strong>on</strong>diti<strong>on</strong>s c<strong>on</strong>sidered in the<br />

analyses were 1 ) end-of-c<strong>on</strong>structi<strong>on</strong>, and 2)<br />

l<strong>on</strong>g-term. For the first c<strong>on</strong>diti<strong>on</strong>, seepage<br />

from the thawing ice-rich soil and any seepage<br />

through material underlying the dam and impoundment<br />

is c<strong>on</strong>sidered sufficient to accelerate<br />

local thawing of the foundati<strong>on</strong> materials. For<br />

l<strong>on</strong>g term c<strong>on</strong>diti<strong>on</strong>s, it was assumed all excess<br />

pore pressure had dissipated and the foundati<strong>on</strong><br />

material had fully c<strong>on</strong>solidated,<br />

In later stages of the embankment, fill material<br />

will be placed over ice-rich foundati<strong>on</strong> material.<br />

To predict settlement, it was estimated<br />

that the total ice c<strong>on</strong>tent of an average 15-foot<br />

1245

thick soillhighly weathered shale horiz<strong>on</strong> within<br />

the foundati<strong>on</strong> area was about seven percent.<br />

The tundra and surficial soils were c<strong>on</strong>sidered<br />

as being removed. Total thawing within the subsurface<br />

profile will result in about <strong>on</strong>e foot<br />

(30 em) of estimated subsidence due to the dissipati<strong>on</strong><br />

of the melted ice. Greater subsidence<br />

are expected in subsurface profiles c<strong>on</strong>taining<br />

higher ice c<strong>on</strong>tents. Subsidence of as.much as<br />

two feet (60 cm) or more may be expected in<br />

some locati<strong>on</strong>s within the foundati<strong>on</strong> area*<br />

Hydrologic and hydraulic analyses were completed<br />

to assist with the design of the seepage collecti<strong>on</strong><br />

system, the tailing dam and associated<br />

emergency spillways. The U.S. Army Corps of<br />

Engineers generalized computer program Flood<br />

Hydrograph Package (HEC-1) was used to develop<br />

inflow hydrographs, peak flow rates, runoff<br />

volumes, and to route hydrographs through the<br />

reservoir (U.S. Army Corps, 1981). A similar<br />

program for analysis of water surface profiles<br />

(HEC-2) was utilized to evaluate spillway flow<br />

characteristics (U.S. Army Corps, 1982).<br />

INSTRUMENTATION<br />

The l<strong>on</strong>g-term stability of both the seepage dam<br />

and the tailing dam is dependent up<strong>on</strong> assumed<br />

pore water pressures in the foundati<strong>on</strong> material,<br />

the positi<strong>on</strong> of a phreatic surface in the embankment,<br />

if any, and permafrost c<strong>on</strong>diti<strong>on</strong>s.<br />

High excess pore pressure and/or permafrost<br />

degradati<strong>on</strong> beneath the embankment could influence<br />

the l<strong>on</strong>g term stability of the dam.<br />

Therefore, it was c<strong>on</strong>sidered important that the<br />

tailing embankment be instrumented so that<br />

deviati<strong>on</strong>s from anticipated behavior of the<br />

embankment could be detected and appropriate<br />

measures be designed to compensate for such<br />

deviati<strong>on</strong>s. Piezometers and thermistors were<br />

specified to be installed in the dams to m<strong>on</strong>itor<br />

subsurface water levels and temperature variati<strong>on</strong>s<br />

to verify the design assumpti<strong>on</strong>s.<br />

Pressure-type piezometers were specified to<br />

m<strong>on</strong>itor seepage and pore pressure buildup within<br />

the potentially weak foundati<strong>on</strong> soils and to<br />

m<strong>on</strong>itor the phreatic surface within the rockfill<br />

embankment.<br />

Measurement of the subsurface temperature variati<strong>on</strong>s<br />

before and after c<strong>on</strong>structi<strong>on</strong> of the<br />

starter dam and subsequent embankment raises<br />

will be evaluated by installing thermistor<br />

strings to depths of about 100 feet (33 meters)<br />

below the base of the dam. The thermistor<br />

strings will be installed in sealed PVC pipe<br />

casing filled with silic<strong>on</strong>.<br />

Figure 1 illustrates the locati<strong>on</strong>s of the instruments<br />

scheduled for installati<strong>on</strong> within the<br />

embankment.<br />

impoundment, and staged c<strong>on</strong>structi<strong>on</strong>, a quantitative<br />

analysis of the thermal performance beneath<br />

the embankment could not provide reliable<br />

results. Rather, simplified thermal procedures<br />

were utilized to predict permafrost aggradati<strong>on</strong><br />

into the dam secti<strong>on</strong> by the time the ultimate<br />

dam secti<strong>on</strong> is c<strong>on</strong>structed. Liner tears, larger<br />

than anticipated flows through the underlying<br />

rock beneath the cutoff trench, or other factors<br />

could significantly alter the predicted thermal<br />

regime. Therefore, a positive m<strong>on</strong>itoring<br />

scheme was developed to detect any deviati<strong>on</strong>s<br />

from the assumed thermal and hydrologic c<strong>on</strong>diti<strong>on</strong>s<br />

as early as possible, so corrective measures<br />

could be instigated in a timely manner.<br />

REFERENCES<br />

Dames & Moore, 1984, Report of Geotechnical<br />

Investigati<strong>on</strong> for the Red Dog Mine Tailings<br />

Dam, prepared for Cominco Alaska, Inc,<br />

December 3, 1984.<br />

Dames & Moore, 1987, Design Report, Proposed<br />

Tailings Dam, Red,Dog Mine Development for<br />

Cominco Alaska, Inc, July 1, 1987.<br />

U.S. Army Corps of Engineers, 1981, Hydrologic<br />

Engineering Center, User's Manual, Flood<br />

Hydrograph Package, HEC-1.<br />

U.S.<br />

Army Corps of Engneers, 1982, Hydrologic<br />

Engineering Center, User's Manual, Water<br />

Survace Profiles, HEC-2.<br />

ACKNOWLEDGEMENTS<br />

The project described in this paper was performed<br />

as part of the Red Dog Mine development<br />

project in Northwest Alaska. The authors wish<br />

to acknowledge Cominco Alaska, Incorporated,<br />

for permitting the authors to use the data presented<br />

in this paper as well as Cominco's<br />

project representatives, Mr. T<strong>on</strong>y Vecchio and<br />

Mr, Jerry Booth, who assisted us and m<strong>on</strong>itored<br />

our work throughout the project.<br />

SUMMARY<br />

The design of a 150 foot high tailing dam embankment<br />

at Red Dog was complicated by the fact that<br />

poor foundati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s and fragile permafrost<br />

is present across the site. Due to the<br />

complexity of the hydrology, the predicted general<br />

degradati<strong>on</strong> of permafrost within the<br />

1246

~ ~~~~~<br />

PERMAFROST SLOPE DESIGN FOR A BURIED OIL PIPELINE<br />

A J. Hanna and E.C. McRoberts<br />

Hardy BBT Limited, Alberta, Canada<br />

SYNOPSIS<br />

The Interprovincial Pipe Line from Norman Wells, NWT to Zama, Alberta traverscs<br />

many permafrost slopes. The paper reviews the slope stability design approach for this buried oil<br />

pipeline and presents a range of design parameters. A summary of the design c<strong>on</strong>figurati<strong>on</strong>s is<br />

also provided.<br />

INTRODUCTION<br />

During April 1985, Interprovincial Pipe Line<br />

Limited began delivery of oil through the<br />

300 mm diameter Norman Wells pipeline 868 km<br />

south to Zama, Alberta. Disc<strong>on</strong>tinuous<br />

permafrost occurs over a large proporti<strong>on</strong> of<br />

the pipeline route varying in thickness up to<br />

50 m. The pipeline is fully buried but the<br />

properties of Norman Wells crude allow the oil<br />

to be discharged at -2O C thereby restricting<br />

thermal input into the surrounding soil.<br />

A<br />

descripti<strong>on</strong> of this project has been provided<br />

by Pick et a1 (1984).<br />

From Norman Wells south the pipeline parallels<br />

the east bank of the Mackenzie River for<br />

500-km, crossing many tributary creeks and<br />

rivers. While the route was located so as to<br />

avoid major areas of known inatability.<br />

permafrost slopes were unavoidable. In total<br />

over 165 slopes were identified as requiring<br />

geotechnical evaluati<strong>on</strong> and site specific<br />

design resp<strong>on</strong>se. The purpose of this paper is<br />

to present background informati<strong>on</strong> and the<br />

design methodology used in slope stability<br />

evaluati<strong>on</strong>s for the Norman Wells pipeline.<br />

OVERVIEW OF DESIGN APPROACH<br />

The slope stability design process began with<br />

the classificati<strong>on</strong> of likely failure modcs.<br />

Following terminology established by earlier<br />

studies of permafrost slope failures<br />

(McRoberts, 1978), a matrix relating likely<br />

failure modes with thermal c<strong>on</strong>diti<strong>on</strong> was<br />

developed, Table I * For frozen slopes, shear<br />

through permafrost is associated with specific<br />

geological c<strong>on</strong>diti<strong>on</strong>s (McRoberts and<br />

Morgensternr 1974) that were largely avoided<br />

by the pipeline. C<strong>on</strong>venti<strong>on</strong>al slope stability<br />

analysis methods and c<strong>on</strong>trol measures were<br />

adopted for unfrozen or n<strong>on</strong>-permafrost slopes<br />

and are not c<strong>on</strong>sidered further. The major part<br />

of the design effort was therefore directed<br />

towards assessing thawing permafrost slopes.<br />

Skin flows or planar movements can develop as<br />

an active layer forms or penetrates deeper<br />

than normal beneath the thermally disturbed<br />

'<br />

"_<br />

TABLE I<br />

"""I<br />

Failure Modes<br />

Thermal C<strong>on</strong>diti<strong>on</strong><br />

Failure Frozen Unfrozen Thawing<br />

Mode$<br />

Skin/Planar 0 X X<br />

Plug 0 0 X<br />

Ditch Backfill 0 X X<br />

~eep Seated X X 0<br />

X-posaible c<strong>on</strong>diti<strong>on</strong>. 0-unlikely c<strong>on</strong>diti<strong>on</strong>.<br />

permafrost right of way (ROW). Excess pore<br />

pressures develop at the thaw fr<strong>on</strong>t and can<br />

lead to unstable c<strong>on</strong>diti<strong>on</strong>s depending up<strong>on</strong><br />

rate of thaw, ice c<strong>on</strong>tent, type of soil and<br />

slope inclinati<strong>on</strong>. As thaw proceeds deeper<br />

into the slope, two dimensi<strong>on</strong>al effects can be<br />

c<strong>on</strong>sidered as a "thaw plug" develops. This<br />

thaw plug is c<strong>on</strong>fined by undisturbed<br />

permafrost terrain adjacent to the ROW. Ditch<br />

backfill placed during winter c<strong>on</strong>structi<strong>on</strong><br />

operati<strong>on</strong> may also become unstable and<br />

fs<br />

another form of a thaw plug.<br />

While this paper c<strong>on</strong>centrates <strong>on</strong> the<br />

geotechnical methods and procedures used for<br />

analytical designr other elements of the<br />

design approach were important and are<br />

c<strong>on</strong>sidered briefly as follows. Slope design<br />

began during alignment locati<strong>on</strong> and where<br />

possible and practical, the centreline was<br />

located <strong>on</strong> previously cleared slope segments<br />

that had already experienced geothermal<br />

disturbance and thawing. In additi<strong>on</strong>, areas<br />

Of known instability were avoided and field<br />

rec<strong>on</strong>naissance was undertaken to check slopes<br />

for signs of instability or thermal erosi<strong>on</strong>.<br />

All major permafrost sl.opes were dril.led 86<br />

well as a representative selecti<strong>on</strong> of other<br />

slopes. The slope catalogue, terrain<br />

analyses, and general knowledge of the route<br />

was relied an to establish likely soil and ice<br />

c<strong>on</strong>diti<strong>on</strong>s in slopes which were not drilled.<br />

It was later possible to c<strong>on</strong>firm these<br />

assumpti<strong>on</strong>s to some extent during the<br />

1247

c<strong>on</strong>structi<strong>on</strong> phase through inspecti<strong>on</strong> of ditch<br />

walls. The permafrost soils encountered were<br />

subdivided into three major soils groups<br />

permitting a generalizati<strong>on</strong> of important soils<br />

properties for stability analyses.<br />

The anal.ytica1 design phase had two basic<br />

comp<strong>on</strong>ents which were tor (1) determine which<br />

slopes should be stable, and (2) establiah<br />

practical mitigati<strong>on</strong> techniques<br />

potentially unstable slopes. It was also for<br />

recognized that several aspects of the<br />

c<strong>on</strong>structi<strong>on</strong> phase were an important comp<strong>on</strong>ent<br />

of the slope design approach. Firstly,<br />

a<br />

series of clearing and c<strong>on</strong>structi<strong>on</strong><br />

specificati<strong>on</strong>s were developed which would help<br />

to minimize the impact in sensitive terrain.<br />

Sec<strong>on</strong>dly, during c<strong>on</strong>structi<strong>on</strong> it was<br />

anticipated that close m<strong>on</strong>itoring of actual<br />

c<strong>on</strong>diti<strong>on</strong>s as encountered in the pipeline<br />

ditch and in cuts would, if required, allow<br />

for design refinements and changes if<br />

necessary. It was recommended as an integral<br />

part of the design approach that <strong>on</strong>ce the<br />

pipeline went into operati<strong>on</strong> a m<strong>on</strong>itoring<br />

program should be instituted and c<strong>on</strong>tingency<br />

plans for remedial acti<strong>on</strong> should be available.<br />

SOIL TYPES AND DESIGN INPUTS<br />

The permafrost soils al<strong>on</strong>g the Norman Wells<br />

pipeline were subdivided i nto three broad<br />

categories as follows:<br />

Ice Rich Clay (IRC)<br />

Frozen glaciolacustrine silt S , clayey silt and<br />

silty clay soils, fine ara i ned colluvium or<br />

slope wash derived soils- were classified as<br />

being ice rich clay. Such soils typically<br />

have water c<strong>on</strong>tents greater than 25 to 30%,<br />

plastic limits from 17 to 25%, and liquid<br />

limits between 35 and 70%. Thaw settlement<br />

tests <strong>on</strong> these soils indicate that at water<br />

c<strong>on</strong>tents of less than 20 to 24% little, if<br />

any, thaw settlement will occur. IRC $Oil5<br />

are rarely encountered with water c<strong>on</strong>tents<br />

le66 than the 20 to 24% range within the depth<br />

of influence of geothermal effects caused<br />

by<br />

disturbance of the terrain. There was no ice<br />

poor clay category adopted for design<br />

purposes. In some slopes, high water c<strong>on</strong>tents<br />

in the order of 50% or greater, visible ice<br />

c<strong>on</strong>tents greater than 30 to 50% and thick ice<br />

lenses were encountered.<br />

Locati<strong>on</strong><br />

"_ TABLE I1<br />

Summaly_of Ice - Rich Clay<br />

""<br />

Direct Shear Test Results<br />

"""I""<br />

C'<br />

I PL 3.5<br />

Sans Sault Test Site 3.5<br />

Hanna Creek 4.1<br />

Billy Creek 6.9<br />

Great Bear River 3.5<br />

Willowlake River 4.1<br />

Martin River 3.5<br />

East Simps<strong>on</strong> Crossing 2.5<br />

Naylors Landing 1.7<br />

9'<br />

Deg.<br />

26.5<br />

30.5<br />

26.7<br />

24.5<br />

26,O<br />

27.5<br />

24.5<br />

30.5<br />

29 .O<br />

Design Value 3.5 24.5<br />

c"<br />

2<br />

kPa cm /a<br />

7.0~10"<br />

2. ~ x I O - ~<br />

7 . OX~O-~<br />

6 . OX~O-~<br />

2. S X ~ O - ~<br />

degree of fabric and to impose a stress<br />

history of over-c<strong>on</strong>solidati<strong>on</strong> (Nix<strong>on</strong> and<br />

Morgenstern, 1973) * Therefore, the laboratory<br />

observati<strong>on</strong> of a coheli<strong>on</strong> intercept is<br />

reas<strong>on</strong>able and can be relied <strong>on</strong> in the field.<br />

Design strength parameters, c' = 3.5 kPa and<br />

#'= 24.5O were selected for IRC soils.<br />

In order to undertake an analysis<br />

of excess<br />

pore pressure effects, the coefficient of<br />

c<strong>on</strong>solidati<strong>on</strong> (c ) is required. A summary of<br />

test results is'given in Table I1 following<br />

interpretati<strong>on</strong> methods presented by McRoberts<br />

et al (1978).<br />

Ice Poor Till (IPT)<br />

""<br />

These tills are dense soils with water<br />

c<strong>on</strong>tents typically less than 10 to 15%. Thaw<br />

settlement tests indicate that tills with<br />

these low water c<strong>on</strong>tents will not settle <strong>on</strong><br />

thawing and, in fact, exhibit a minor tendency<br />

to swell. In some frozen slopes a minor<br />

comp<strong>on</strong>ent of dense frozen sands or silty sands<br />

can occasi<strong>on</strong>ally be encountered. For analysis<br />

purposes these well draining soils were<br />

c<strong>on</strong>sidered equivalent to ice poor till. All<br />

strength data €or till has been assembled <strong>on</strong><br />

Figure 1, with the average strength line<br />

established for design indicated. Data for c<br />

A summary of direct shear tests <strong>on</strong> initially<br />

frozen ice rich clay samples that were thawed<br />

when -sheared, is given in Table 11. Triaxial<br />

test data from some of these sites established<br />

lower bound strength parameters, c' - 12 kPa<br />

and 9' = 27.5O. Roggensack (1977) presenteg<br />

triafial data of c' = 6.9 kPa and 9' = 26.5<br />

for silty clay from the Mountain River area<br />

and c' - 3.5 kPa and @' - 34O from the Fort<br />

Simps<strong>on</strong> regi<strong>on</strong>. All direct shear testing was<br />

undertaken at extremely low strain rates and<br />

at in situ normal stresses. For these tests a<br />

cohesi<strong>on</strong> intercept was always obtained. This<br />

cohesi<strong>on</strong> intercept would not be expected<br />

in<br />

normally c<strong>on</strong>solidated clay soils. However,<br />

the influence of <strong>on</strong>e or more freeze-thaw<br />

cycles is to densify the soil, impart some<br />

Figure 1.<br />

Strength data for ice poor till<br />

1248

varles over a wide range from as low as<br />

4 x loe4 cm2/s to a high of 2 x cm2/sa<br />

An average c is in the range of 5 x to<br />

2v<br />

1 x cm /s.<br />

Ice Rich Till (IRTL<br />

An intermediate category of ice rich till was<br />

adopted for design purposes. This<br />

classificati<strong>on</strong> was used for till sails which<br />

have some visible ice and higher water (ice)<br />

c<strong>on</strong>tents.<br />

severe damage to the surface mat) and the<br />

expected thaw depth is about 4 to 6 m in 25<br />

years . A relatively undisturbed slope<br />

(removal of trees <strong>on</strong>ly) may thaw from about 1<br />

to 4 m in 25 years, and in some instances, the<br />

permafrost does not appear to degrade at all.<br />

Therefore, it is desirable for the pipeline to<br />

be c<strong>on</strong>structed with a minimum amount of ground<br />

surface disturbance. More detailed<br />

interpretati<strong>on</strong> indicates that the width of the<br />

disturbed ROW influences thaw depth. This is<br />

in accordance with theory, although the effect<br />

is difficult to quantify because of<br />

uncertainty in the permafrost temperature.<br />

Available data (Figure 3) indicates that<br />

limiting the ROW width can reduce the<br />

l<strong>on</strong>g-term thaw depth. Figure 4 presents the<br />

dasign thaw depth progressi<strong>on</strong> used for the<br />

13 m wide ROW selected for c<strong>on</strong>structi<strong>on</strong> <strong>on</strong><br />

ice-rich slopes.<br />

1<br />

Figure 2.<br />

areaa<br />

Thaw degradati<strong>on</strong> beneath cleared<br />

Depth of Thaw Observati<strong>on</strong>s<br />

A fundamental comp<strong>on</strong>ent of stability analyses<br />

is the thaw depth following tree clearing and<br />

c<strong>on</strong>structi<strong>on</strong>. Field observati<strong>on</strong>s from the<br />

central Mackenzie Valley (Figure 2) indicate<br />

moderate degradati<strong>on</strong> for a disturbed slope<br />

(i.e., complete removal of vegetati<strong>on</strong> and<br />

5 10 I5 20<br />

THAW SEASON SINCE CONSTRUCTION<br />

i<br />

Figure 4.<br />

Design thaw progressi<strong>on</strong><br />

Failures in Thawinq "" Slop5<br />

Figure 3. Thaw depth versus width of clearing<br />

1249<br />

During the late 1970's a detailed program of<br />

field investigati<strong>on</strong>, laboratory testing and<br />

analyses of thawing slopes was undertaken in<br />

the Mackenzie River Valley. As part of this<br />

study five slopes, which had failed in a skin<br />

flow or planar mode due to a variety of<br />

surface disturbance effects, wer<br />

investigated, Table 111. All these slopes are<br />

IRC category and from 13' to 19' in<br />

inclinati<strong>on</strong>. Once failure began, slope angles<br />

in the order of 8' to 12O were formed.<br />

Adjacent slopes, in what appeared <strong>on</strong> a vSsual<br />

basis to be identical soils, were stable <strong>on</strong><br />

inClinatiOnS of to loo. These data taken<br />

together suggest that slopes in the order of

I<br />

TABLE-LIT<br />

Summary of Skin Flow Failures<br />

"""<br />

Site<br />

Disturbance Effect Slope.Angle (Degrees)<br />

Initial Failed Adjacent<br />

TO Stable<br />

Sans Pipeline test installati<strong>on</strong>, winter c<strong>on</strong>structi<strong>on</strong>,<br />

Sault mechanical tree 16 clearing 11 9<br />

Hanna Creek Forest fire with deep burn in dry surface organics 16 10-12 4<br />

Billy Creek and Ground toe erosi<strong>on</strong> fire<br />

19 10 10<br />

Martin River Highway ROW clearing and springthaw traffic 13 9 6<br />

Naylors Hand clearing<br />

of tree3 for navigati<strong>on</strong> marker<br />

Landing Mackenzie River 8 1018<br />

go to 10' or less are likely to be stable as<br />

l<strong>on</strong>g as gross disturbance to the surface cover<br />

is avoided,<br />

Pore Pressures in Till<br />

For IPT soils, the low water (ice) c<strong>on</strong>tents<br />

and the tendency of the soils to actually<br />

swell during thaw settlement tests, suggest<br />

that low pore water pressures would be<br />

encountered in thawing slopes. Piezometers<br />

and standpipes were installed in boreholes<br />

drilled during the slopes investigati<strong>on</strong><br />

programs in existing thaw bulbs of depths from<br />

1.0 to about 5.0 m. Figure 5 plots all<br />

observed data in terms of the pore pressure<br />

ratio m, as defined in Figure 5, versus the<br />

depth of thaw, d . This data indicates that in<br />

most cases very low pore pressure c<strong>on</strong>diti<strong>on</strong>s<br />

were observed.<br />

"I<br />

FOR THAW MPTH 3 16m 115') m 15 I I<br />

C4LCUL4TEO REL4TIVE TOSLIP a<br />

SURFACE 4T46m.THt: CRITICAL DEPTH<br />

X-WATER LEVEL DEEPER THAN<br />

THnW DEPTH<br />

OL".X"-Y""i2." ".* ~<br />

W"<br />

0 IO 20 30 40 so 60 70<br />

DEPTH OF TH4W lMETER5i<br />

Figure 5 . Pore pressures in thawed till slopes<br />

SLOPE DESIGN<br />

A major design decisi<strong>on</strong> was to establish the<br />

cut-off angle, below which thawing would not<br />

result in unstable slopes. Several factors<br />

had to be c<strong>on</strong>sidered. Firstly, the impact of<br />

c<strong>on</strong>structi<strong>on</strong> disturbance and ROW width was<br />

I<br />

80<br />

judged to be relevant. It was felt that a<br />

13 m ROW, with hand clearing of trees and<br />

minimal surface disturbance would support<br />

steeper slopes than a 20 m ROW with complete<br />

removal of surface organics and insulating<br />

layer. Sec<strong>on</strong>dly, the desirable factor of<br />

safety (FS) for static loading c<strong>on</strong>diti<strong>on</strong>s was<br />

in the range, 1.25 to 1.5. Seismic loading<br />

was also c<strong>on</strong>sidered, by applying a 12%<br />

horiz<strong>on</strong>tal accelerati<strong>on</strong>, and a pseudostatic<br />

factor of safety equal to or greater than<br />

unity was judged necessary. As -thaw proceeds,<br />

a transiti<strong>on</strong> from infinite slope to thaw plug<br />

mechanism had to be c<strong>on</strong>sidered. The relative<br />

influence of moderate effective cohesi<strong>on</strong>, for<br />

example c' = 3.5 kPa for IRC, was important at<br />

shallow thaw depths. The influence of excess<br />

pore pressure generati<strong>on</strong> became l.ess with<br />

subsequent thaw seas<strong>on</strong>s (McRoberts et a1<br />

1978). Finally the empirical evidence from a<br />

range of failed slopes had to be c<strong>on</strong>sidered.<br />

The l<strong>on</strong>g--shallow or planar nature of a thawing<br />

slope in a cleared pipeline ROW can be readily<br />

analyzed by an infinite slope method. For<br />

thawing slopes in soils such as ice poor tills<br />

the c<strong>on</strong>venti<strong>on</strong>al form of the analysis,<br />

Equati<strong>on</strong> I, Figure 6 can be used. In IRC and<br />

IRT slopes, excess water pressures generated<br />

by thawing of the frozen soil must be<br />

incorporated into the appropriate form of the<br />

equati<strong>on</strong> to obtain Equati<strong>on</strong> 2, Figure 6<br />

(McRoberts, 1978)- For the thaw plug case,<br />

where a cleared ROW of finite width is<br />

C<strong>on</strong>sidered, there will be increased side shear<br />

resistance al<strong>on</strong>g the edges of the thaw bulb<br />

corresp<strong>on</strong>ding roughly to the width of the ROW.<br />

This increased resistance can be incorporated<br />

into the infinite slope stability equati<strong>on</strong>, to<br />

produce a more general. form, Equati<strong>on</strong> 3,<br />

Figure 6 (McRoberts, 1978).<br />

An example of the applicati<strong>on</strong> of this method<br />

is as follows. C<strong>on</strong>sider an IRC slope with<br />

design parameters as summarized in Table 11,<br />

and refer to Fiaure 6 for terms and eauati<strong>on</strong>s.<br />

For a badly disturbed surface, the geothermal<br />

analysis indicated a= 6.1 x cm/s1'2 com-<br />

pared to a value of a = 3.4 x cm/s 1/2<br />

where about 240 mm of peat cover is left<br />

1250

+<br />

INFINITE SLOPE<br />

NOEXCESS PORE PRESSURES<br />

C' (I-rn +) tanel<br />

FS .."._"<br />

8d sine coae<br />

tan e<br />

I<br />

c', 0' Effective strers strtnqtn U Unit weiqnt Of soil<br />

d - Depth of thaw KW - Unit weignt of wotmr<br />

e - Slope <strong>on</strong>gle rnd- Phreatic surface<br />

C<strong>on</strong>structi<strong>on</strong><br />

c<strong>on</strong>diti<strong>on</strong><br />

Feat Removal<br />

Row Width<br />

soil Category<br />

IRC<br />

IRT<br />

IPT<br />

TABLE IV<br />

Cut-Off Angles for "mwing Slopes<br />

N<strong>on</strong> Insulated<br />

Backfill<br />

Wheel<br />

Nil Colaplcte Cmplete Backhm Ditcher<br />

to 20 m 13 m to 20 m Spoil Spoil<br />

9 e 7 4 1<br />

13 12 11 7 10<br />

18 18 17 10 14<br />

1' = I-Iw , R- -/2<br />

- OT A c<strong>on</strong>atant (crn/s"') cy - Coefflegsnt of<br />

c<strong>on</strong>soildatl<strong>on</strong> crnz/a<br />

THAW PLUG<br />

, FS - 6 ( sec e cnscce + 2 (9)<br />

cosec e ) +<br />

) ........<br />

KO Eorth pressure coefficient<br />

S - Width of thaw plug<br />

0.8 4 factor to occount for the n<strong>on</strong>-rectanqular thaw bulb<br />

Figure 6. Thaw stability analysis<br />

intact. For a c of 1 X IOm3 cm2/s, the R<br />

value ranged fro; 0.34 to 0.61. In the<br />

immediate vicinity of the pipeline ditch it is<br />

clear that some significant disturbance will<br />

be caused. Accordingly, a value of R-0.47 was<br />

selected for the first thaw seas<strong>on</strong> in IRC<br />

slopes. Other design inputs were a thaw depth<br />

of 2.4 m and a ratio 'y'/~= 0.5. For the<br />

infinite slope equati<strong>on</strong> an FS of 1.47 is<br />

predicted for a 9' slope. Assuming c' = 0<br />

the FS = 1.0. With subsequent thaw Beas<strong>on</strong>e<br />

thaw proceeds deeper according to Figure 4.<br />

The influence of c' becomes less, but is more<br />

than offset by thaw plug effects and a reduced<br />

equivalent R value.<br />

The initial design c<strong>on</strong>figurati<strong>on</strong> c<strong>on</strong>sidered a<br />

13 m ROW and limited surface disturbance. A<br />

cut-off angle of go was adopted for IRC<br />

slopes. This value was c<strong>on</strong>sistent with<br />

experience <strong>on</strong>, or adjacent to, documented skin<br />

flow failures. &s the design evolved,<br />

c<strong>on</strong>structi<strong>on</strong> practice requiring a wider ROW<br />

and peat removal was accommodated. For a<br />

wider ROW and complete peat removal the cutoff<br />

angle for IRC slopes was reduced to 7O. A<br />

summary of the design cut-off angles is<br />

presented in Table IV.<br />

Th@ stability of the backfill in the pipeline<br />

trench was also c<strong>on</strong>sidered. It was<br />

anticipated that either backhoes or wheel<br />

ditchers would be used to excavate the<br />

pipeline ditch. Material excavated by backhoe<br />

was likely to be larger and more irregularly<br />

- 3<br />

sized than ditcher spoil. Maintaining a<br />

stable ditch c<strong>on</strong>figurati<strong>on</strong> was required in<br />

order to prevent lateral retrogressi<strong>on</strong> of<br />

thawing permafrost and for drainage and<br />

erosi<strong>on</strong> c<strong>on</strong>trol. Design cut-off angles<br />

established for excavated spoil used as ditch<br />

backfill are given in Table IV.<br />

Pipeline ROW segments with inclinati<strong>on</strong>s<br />

greater than the cut-off angles required<br />

mitigative acti<strong>on</strong>. In some IRC slopes ground<br />

ice c<strong>on</strong>tents were sufficiently high that the<br />

design recommendati<strong>on</strong> was to essentially<br />

eliminate thaw below the naturally occurring<br />

active layer. Otherwise, the mitigative<br />

design tolerated some thaw a6 l<strong>on</strong>g a6 minimum<br />

factors of safety were obtained. A variety of<br />

soluti<strong>on</strong>s were c<strong>on</strong>sidered, including a<br />

gravel/synthetic insulati<strong>on</strong> sandwich, wo.od<br />

chips and a wood chip/synthetic insulati<strong>on</strong><br />

sandwich. Design procedures for such a method<br />

were developed by McRoberts and Nix<strong>on</strong> (1977).<br />

The method accounts €or the retarding<br />

influence of insulati<strong>on</strong> <strong>on</strong> the rate<br />

of thaw<br />

and excess pore pressure generati<strong>on</strong> and the<br />

surcharge effect from a free draining layer,<br />

such as gravel, increasing the mobilized<br />

effective shear strength.<br />

Wood chips were selected as the primary design<br />

mode for several reas<strong>on</strong>s as documented by<br />

McRobertg et a1 (1985) who also presented the<br />

geothermal c<strong>on</strong>siderati<strong>on</strong>s involved with wood<br />

chip design. Heat generati<strong>on</strong> within the wood<br />

chips was recognized in predicting the<br />

geothermal perrormance of the wood chip<br />

insulati<strong>on</strong>.<br />

The slope stability design proceeded using the<br />

infinite slope method, as modified for<br />

insulati<strong>on</strong> effects by McRoberts and Nix<strong>on</strong><br />

(1977). An FS of at least 1.5 was required<br />

and the thickness of wood chips necessary to<br />

maintain a minimum FS of 1.5 over a design<br />

life of 25 years was obtained, see insert to<br />

Figure 7. For example, for a 12' IRC slope a<br />

600 mm thickness of wood chips was predicted<br />

for the case of a 13 m ROW with no peat<br />

removal and with an average<br />

of 150 mm peat<br />

assumed present. The design predicti<strong>on</strong>s<br />

allowed for variati<strong>on</strong>s in c<strong>on</strong>structi<strong>on</strong><br />

practice. These modificati<strong>on</strong>s were based <strong>on</strong><br />

the predicted increase in depth o€ thaw<br />

c<strong>on</strong>sequent up<strong>on</strong> increases in ROW width and<br />

peat removal. For example, if a 600 mm wood<br />

.- chip thickness is required for the "13 m ROW +<br />

Peat" case, the predicted maximum al.lowahle<br />

1251

thaw depth is 2.4 m. For the "Peat Removal t<br />

20 m ROW" case, Figure 7, 1000 mm of wood<br />

chips ate requited to maintain the same depth<br />

of thaw below the wood chips.<br />

In some instances mitigative acti<strong>on</strong> was also<br />

necessary where cross-slope grading was<br />

required to provide a level working surface<br />

for pipeline installati<strong>on</strong> operati<strong>on</strong>s. Side<br />

hill cuts were designed to 2.5 horiz<strong>on</strong>ta1:l.O<br />

vertical in unfrozen or ice poor soil. Cuts<br />

were made vertical in ice rich terrain. Some<br />

l<strong>on</strong>gitudinal slopes had side cuts and if the<br />

slope required insulati<strong>on</strong> the wood chips were<br />

ramped up and over the side cut.<br />

WOOD CHIP THICKNESS Imml<br />

0 300 600 900 1200 IS00<br />

0<br />

cou Id not be satisf ied. Fina ~lly, the design<br />

stipulated some ground temperature and pore<br />

pressure m<strong>on</strong>itoring.<br />

In the spring of 1985, c<strong>on</strong>structi<strong>on</strong> of this<br />

first fully buried oil pipeline in permafrost<br />

terrain was completed. Slope stability<br />

designs and wood chip surface insulati<strong>on</strong><br />

c<strong>on</strong>tinue to provide thermal protecti<strong>on</strong> to<br />

permafrost slopes susceptible to instability<br />

due to thawing. To date, the performance of<br />

slopes has been satisfactory with the<br />

excepti<strong>on</strong> of minor erosi<strong>on</strong> problems and the<br />

stability of side cuts aggravated by<br />

n<strong>on</strong>-adherence to design specificati<strong>on</strong>s. The<br />

majority of the wood chip insulati<strong>on</strong> has<br />

performed as assumed in the design. Some heat<br />

generati<strong>on</strong> persisted <strong>on</strong> a localized basis <strong>on</strong><br />

certain slopes (Pick, 19871, however, these<br />

situati<strong>on</strong>s have been rectified.<br />

REFERENCES<br />

/<br />

McROBERTS, E.C., FLETCHER, E., & NIXON, J.F.<br />

(1987). Thaw c<strong>on</strong>solidati<strong>on</strong> effects in<br />

degrading permaftoat. Third Intl. C<strong>on</strong>f.<br />

<strong>Permafrost</strong>, Vol 1, pp 694-699.<br />

McROBERTS, E .e., HANNA, A.J., & SMITH, ;I.<br />

(1986). M<strong>on</strong>itoring of thawing permafrost<br />

slopem: Interprovincial Pipe Line. NRCC<br />

Tech. Memo 139, pp 133-151.<br />

Figure 7. Design insulati<strong>on</strong> requirements<br />

Mitigative measures in the form of select<br />

granular backfill, ditch plugs, surface<br />

diversi<strong>on</strong> berms and breaks in the backfill<br />

mound were used to c<strong>on</strong>trol potentially adverse<br />

drainage c<strong>on</strong>diti<strong>on</strong>s al<strong>on</strong>g the ROW. Seeding<br />

and fertilizing was another important means of<br />

reducing erosi<strong>on</strong> potential.<br />

CONCLUDING<br />

""<br />

3EMARKS<br />

The slope stability design for the Norman<br />

Wells Pipeline Project incorporated geothermal<br />

and stability analyses as well a6 empirical<br />

informati<strong>on</strong> <strong>on</strong> previously failed slopes. The<br />

stability analyses were based up<strong>on</strong> the<br />

infinite slope theory which was modified to<br />

incorporate the effects of pore pressure<br />

generati<strong>on</strong> and dissipati<strong>on</strong>, the effects of<br />

a<br />

thaw plug and a layered profile, accounting<br />

for the surcharge and insulating effects<br />

of<br />

the wood chips. The design itself presented<br />

some restricti<strong>on</strong>s to c<strong>on</strong>structi<strong>on</strong> practice,<br />

such as a narrower ROW, and also provided for<br />

field design changes if these restricti<strong>on</strong>s<br />

1<br />

McROBERTS, E.C. (1978). Slope stability in<br />

cold regi<strong>on</strong>s. Geotechnical engineering<br />

for cold regi<strong>on</strong>a. McGraw Hill Book Co.,<br />

Editors: Andersland, O.B. and Anders<strong>on</strong>,<br />

D.M.<br />

McROBERTS, E.C., 6 MORGENSTERN, N.R. (1974).<br />

Stability of slopes in frozen soil.<br />

Mackenzie Valley, N.W.T., Vol IT,<br />

pp 554-559.<br />

McROBERTS. E.C., L NIXON, J.F. (1977).<br />

Ex.tensi<strong>on</strong>s to thawing slope stability<br />

theory. Proceedings Sec<strong>on</strong>d Intl.<br />

Symposium <strong>on</strong> Cold Regi<strong>on</strong>s Engineering,<br />

University of Alaska.<br />

NIXON, J.F., & MORGENBTERN, N.R. (1973). The<br />

residual stress in thawing soila. Can.<br />

Geot. Jnl., Vol. 10, p. 571.<br />

PICK, A.R. (1987). Use of wood chips for<br />

permaftoat slope stabilizati<strong>on</strong>. CSCE<br />

Centennial C<strong>on</strong>f., M<strong>on</strong>treal, May 19-22,<br />

1987.<br />

PICK, A.R., SANGSTER, n., & SMITH, J. (1984).<br />

Norman Wells pipeline project. Proc.<br />

ASCE/CSCE Third Intl C<strong>on</strong>f. <strong>on</strong> Cold<br />

Regi<strong>on</strong>s Engineering. April 4-6,<br />

Edm<strong>on</strong>t<strong>on</strong>, pp 11-18.<br />

ROGGENSACK, W.D. (1977). Geotechnical<br />

properties of fine-grained permafrost<br />

soils", Ph.D. Thesis, University of<br />

Alberta, Alberta.

A METHOD FOR CALCULATING THE MINIMUM BURIED<br />

DEPTH OF BUILDING FOUNDATIONS<br />

Jiang, H<strong>on</strong>gju and Cheng, Enyuan<br />

Oilfield C<strong>on</strong>structi<strong>on</strong> Design and <strong>Research</strong> Institute of Daqing Petroleum Administrative Bureau<br />

SYNOPSIS<br />

A method for calculating the minimum buried depth of building foundati<strong>on</strong>s in<br />

seas<strong>on</strong>al 1y frozen ground is presented. The method is based <strong>on</strong> the principle that the frost heave<br />

defo.rmat i<strong>on</strong> of a foundati<strong>on</strong> should not exceed the allowable deformati<strong>on</strong> of the building. The method<br />

has been applied to the design of four experimental buildings with satisfactory results.<br />

INTRODUCTION<br />

When the buried depth of a building foundati<strong>on</strong><br />

c<strong>on</strong>structed in seas<strong>on</strong>ally frozen ground is less<br />

than the maximum frost penetrati<strong>on</strong>, a frozen<br />

layer will occur under the foundati<strong>on</strong>. If the<br />

soil i s frost susceptible, the overlying building<br />

foundati<strong>on</strong> will be lifted due to frost heaving<br />

of the ground. Observati<strong>on</strong>s have shown that<br />

frost penetrati<strong>on</strong> under a building foundati<strong>on</strong><br />

is variable: hence, the amount of frost heave of<br />

the subsoil beneath the foundati<strong>on</strong> may be n<strong>on</strong>uniform,<br />

resulting in differential deformati<strong>on</strong><br />

of the building. When this exceeds the allowable<br />

deformati<strong>on</strong>, the walls of the building will tilt,<br />

with possibly permanent demage resulting,<br />

The maximum thickness of frozen ground under a<br />

foundati<strong>on</strong>, for which the frost heave deformati<strong>on</strong><br />

does not exceed the allowable deformati<strong>on</strong><br />

of the building, is defined as the allowable<br />

thickness [dl . The minimum buried depth (h) of<br />

a foundati<strong>on</strong> in c<strong>on</strong>siderati<strong>on</strong> of frost heave is<br />

defined a5 the difference between the calculated<br />

frost penetrati<strong>on</strong> (H) and the allowable thickness<br />

[dl of frozen layer beneath the foundati<strong>on</strong>,<br />

i.e.<br />

h = H - [dl (1)<br />

CALCULATED FKOST DEPTH OF SUBSOILS<br />

The calculated frost depth of subsoil refere to<br />

the maximum actual frost depth of the soil under<br />

foundati<strong>on</strong> after c<strong>on</strong>structi<strong>on</strong> of the building.<br />

Based up<strong>on</strong> field observati<strong>on</strong>s for many years,<br />

this may be estimated by<br />

H = mh'$T.Zo (2)<br />

where mh--an empirical coefficient dependent<br />

up<strong>on</strong> the frost susceptibility of the<br />

soil;<br />

influence coefficient of heating in<br />

buildings un frost depth; and<br />

Z,--the so-called standard frost depth in<br />

the c<strong>on</strong>structi<strong>on</strong> area [I].<br />

The values of mh and $T can be determined from<br />

Tables I and 11.<br />

TABLE I<br />

Values of the Coefficient mh in eq.(Z)<br />

Frost-susceptibility<br />

N<strong>on</strong> Ils 1% 1.1<br />

Weak l%12% 0.85<br />

N<strong>on</strong>-frost-susceptible<br />

fine sand:<br />

Saturated H,S 1.5m 0.85<br />

Wet l.5m2.5m 1.2<br />

Note: (1) Hw--groundwater level before<br />

freezing;<br />

(2) 'I --frost heave ratio of subsoil.<br />

TABLE II<br />

Values of the Coefficient $T in eq.(2)<br />

Relative height of<br />

Values of BT<br />

building floor above<br />

ground surfact At the corner of At the middle of<br />

Ah, cm peripheral wall peripheral wall<br />

S 30 0.85 0.7<br />

375<br />

>75<br />

1.0 0.8<br />

1 .o 1 .o<br />

Note:(l) When m<strong>on</strong>thly mean temperature in building<br />

is lower than 10°C, $ ~=1 for heated<br />

building; d~~=I.l for unheated buildings.<br />

(2) The dividing of the corner and the middle<br />

of a peripheral wall is the same as<br />

mh<br />

1253

stated in the Standard of Foundati<strong>on</strong><br />

Design in Industrial and Civil Architecture<br />

(TJ7-74).<br />

(3) The values in this table are incorporated<br />

in the modified versi<strong>on</strong> of<br />

.Standard of Foundati<strong>on</strong> Design in industrial<br />

and Civil Architecture 1985.<br />

METHOD FOR CALCULATING THE ALLOWABLE THICKNESS<br />

OF FROZEN LAYER UNDER BUILDING FOUNDATION<br />

Based <strong>on</strong> our investigati<strong>on</strong>, the allowable frozen<br />

layer thickness, [dl, under a building foundati<strong>on</strong><br />

can be calculated by<br />

[As1 (l+!)<br />

[dl =<br />

(3)<br />

:.x<br />

where [As]--the allowable deformati<strong>on</strong>. For a <strong>on</strong>estory<br />

brick building, [.As] is taken<br />

as 10 mm; for a multi-story building,<br />

[As] is 15 mm.<br />

ij --the mean frost heave ratio of subsoils<br />

c<strong>on</strong>cerned. It can be determined<br />

from in-situ observati<strong>on</strong>al<br />

data, or from Fig.1 if there are no<br />

data.<br />

1 --a coefficient to account for the<br />

effect of load <strong>on</strong> the frost heave.<br />

It is determined from Fig.2.<br />

Fig.1 Distributi<strong>on</strong> of Frost Heave Ratio<br />

Al<strong>on</strong>g Frost Depth €or the Subsoil of:<br />

(1) n<strong>on</strong>-frost heave, (2) weak frost heave,<br />

(3) medium frost heave, (4) high frost<br />

heave, and (5) very high frost heave.<br />

CALCULATION OF THAW SETTLEMENT OF THE FROZEN<br />

LAYER BENEATH FOUNDATION ALLOWED IN WINTER<br />

Field observati<strong>on</strong>s of experimental foundati<strong>on</strong>s<br />

Fig.2 The Coefficient vs. Frost Depth Beneath Foundati<strong>on</strong>s<br />

with Various Applied Loads:<br />

a--0 kPa, b--30 kPa, c--80 kPa, d--130 kPa, and e--180 kPa<br />

for: (1) weak, (2) medium, (3) high, and (4) very high frost<br />

susceptible subsoils.<br />

1254

have sho\;n that the subsoils beneath the foundati<strong>on</strong>s<br />

settle due to thawing after experiencing<br />

frost heave in \si-nter. After the frozen layer<br />

under a foundati<strong>on</strong> completely thawed, the level<br />

of t.he foundati<strong>on</strong> base was not the same as<br />

before frost heave, but was lower. For foundati<strong>on</strong>s<br />

riith the same buried depth and similar<br />

soil c<strong>on</strong>diti<strong>on</strong>s, the higher the applied load,<br />

the less the frost heave deformati<strong>on</strong>, but the<br />

greater the t-hawed settlement. The tests also<br />

sho~ed that the greater the frost-heaving ratio<br />

of the soil, the more the thawed settlement is,<br />

vhen the applied load is the same. Because the<br />

amount of thaw settlement under foundati<strong>on</strong>s is<br />

greater than the frost heave, the design of a<br />

foundati<strong>on</strong> should be based not <strong>on</strong>ly <strong>on</strong> determinati<strong>on</strong><br />

of the allowable thickness of froz'en<br />

soil under the foundati<strong>on</strong> from eq.(3), but also<br />

<strong>on</strong> the thaw settlement o€ the frozen layer estimated<br />

from the following criteri<strong>on</strong><br />

vhere Asp is the ultimate thaw settlement of<br />

the frozen layer underneath the foundati<strong>on</strong>, and<br />

R is the so-called "thaw settlement ratio",<br />

defined as the ratio of Asp/[d] in percent. The<br />

value of B may be determined from Fig.3.<br />

nrl cracks or damage.<br />

CONCLUSIONS<br />

(i) Observati<strong>on</strong>s <strong>on</strong> experimental buildings<br />

showed that the actual deformati<strong>on</strong> was<br />

less than the calculated value. Therefore,<br />

based <strong>on</strong> this, the proposed method<br />

€or calculating the minimum buried depth<br />

of foundati<strong>on</strong> in c<strong>on</strong>siderati<strong>on</strong> of soil<br />

susceptibility is reliable.<br />

(ii)<br />

(iii)<br />

(i1i.i)<br />

In calculating the minimum buried depth<br />

of foundati<strong>on</strong>s by the proposed equati<strong>on</strong>s,<br />

the change of frost susceptibility of<br />

subsoil due to an incrt!ase in wather<br />

c<strong>on</strong>tent and/or a rise of the water table<br />

during operati<strong>on</strong> of the building should<br />

be taken into c<strong>on</strong>siderati<strong>on</strong>.<br />

The proposed method for calculating the<br />

minimum buried depth of foundati<strong>on</strong>s in<br />

seas<strong>on</strong>ally frozen subsoil c<strong>on</strong>siders not<br />

<strong>on</strong>ly the freeze-thaw susceptibility of<br />

subsoilsb,uL also other various factors<br />

so as to make Lhe determined minimum<br />

buried depth reas<strong>on</strong>able.<br />

Compared to other available design methods,<br />

the buried depth of foundati<strong>on</strong> determined<br />

by the proposed method is 40-<br />

90 cm less, i.e., a reducti<strong>on</strong> of 20-50X<br />

in routine design depth. As a c<strong>on</strong>sequence,<br />

the cost of foundati<strong>on</strong> engineering<br />

can be greatly reduced.<br />

REFERENCE<br />

Standard of Foundati<strong>on</strong> Design in Industrial and<br />

Civil Architecture (TJ7-74). Chinese<br />

Architec,ture Publishing House, 1974.<br />

Fig.3 Thaw Settlement Ratio Bvs. Applied<br />

Load for:<br />

(A) weak, (B) medium, (C) high, (D)<br />

very high frost susceptible subsoil.<br />

VERIFItATION OF THE METHOD<br />

Al.though eqs.(l) and (3) were developed from<br />

reas<strong>on</strong>able assumpti<strong>on</strong>s, and the parameters used<br />

were determined from field tests, the reliability<br />

in engineering practice must be verified.To this<br />

end, four experimental <strong>on</strong>e-story brick houses<br />

were designed with the above method, c<strong>on</strong>structed<br />

in the summer of 1984 and put into use in Xovember<br />

of the year. Tho deformati<strong>on</strong>s of the houses<br />

were measured periodically. In additi<strong>on</strong>, 36<br />

experimental buildings c<strong>on</strong>structed before 1984<br />

were also checked according to the equati<strong>on</strong>s.<br />

The results of observati<strong>on</strong>s and calculati<strong>on</strong>s<br />

showed that all of the huildings(either <strong>on</strong>estory<br />

or multi-story) for which the foundati<strong>on</strong><br />

buried depth c<strong>on</strong>formed to the above method, h8d<br />

1255

PROTECTION OF WARM PERMAFROST USING CONTROLLED<br />

SUBSIDENCE AT NUNAPITCHUK AIRPORT<br />

E.G. Johns<strong>on</strong> and E.P. Bradley<br />

Department of Transportati<strong>on</strong> and Public Facilities, State of Alaska<br />

SY NOPS IS The selected alignment for the Nunapitchuk Airport required that it be c<strong>on</strong>structed over<br />

virgin tundra underlain by warm permafrost c<strong>on</strong>sisting of massive ice and ice-rich silt. If not<br />

adequately c<strong>on</strong>sidered, the resulting thaw would cause settlement differentials of several m. The<br />

c<strong>on</strong>cept of c<strong>on</strong>trolled subsidence was used to reduce such settlements to a tolerable level. The<br />

design included 1.22 rn of embankment with 0.15 m of insulati<strong>on</strong> board placed 0.61 m from the surface.<br />

Thermal calculati<strong>on</strong>s using iterati<strong>on</strong>s of the Modified Berggren Equati<strong>on</strong> indicated that the<br />

settlement could be as much as 0.15 m in 20 years in the underlying permafrost. Embankment<br />

c<strong>on</strong>structi<strong>on</strong> was completed the spring of 1985. As of September 1987, no thaw had occurred in the<br />

underlying permafrost as predicted by the initial calculati<strong>on</strong>s. It appears that the embankment is<br />

performing as designed.<br />

INTRODUCTION<br />

Nunapitchuk is an Eskimo village of<br />

approximately 350 residents located al<strong>on</strong>g the<br />

shore of the Johns<strong>on</strong> River approximately 40 km<br />

west-northwest of Bethel, Alaska. No roads<br />

service Nunapitchuk and prior to the<br />

c<strong>on</strong>structi<strong>on</strong> of the airport, the nearest<br />

airport was a 6 km boat or snow machine trip.<br />

During spring breakup and fall freeze-up travel<br />

was severely limited, making the delivery of<br />

freight and mail very unreliable. Medical<br />

emergencies had to be evacuated to Bethel by<br />

helicopter during these periods.<br />

CLIMATOLOGY<br />

The climate is more marine than c<strong>on</strong>tinental<br />

which tends to lessen the daily temperature<br />

extremes. The nearest weather stati<strong>on</strong> is at<br />

Bethel from which the following data were<br />

recorded. During June and July the temperature<br />

rises noticeably under the influence of warmer<br />

c<strong>on</strong>tinental air. Extremeo air temperatures<br />

recorded ranged between -47 C in January and<br />

32O C in June. The average last day of<br />

freezing is May 30 and the average first day of<br />

freezing is September 9. The annual mean air<br />

temperature is -1.7' C. Annual precipitati<strong>on</strong><br />

averages 0.43 m with August, the wettest m<strong>on</strong>th,<br />

averaging slightly over 0.15 m. Snow fall<br />

averages 1.25 m per year with a maximum amount<br />

of 1.46 m recorded in January 1952.<br />

GEOLOGY ~ N TOPOGRAPHY<br />

D<br />

Nunapitchuk is located in the southeast porti<strong>on</strong><br />

of a major physiographic divisi<strong>on</strong> of Alaska<br />

termed the Yuk<strong>on</strong>-Kuskokwim Lowland, which is a<br />

porti<strong>on</strong> of a vast delta formed by the Yuk<strong>on</strong> and<br />

Kuskokwim Rivers (Figure 1). Pleistocene delta<br />

deposits comprised of silt and sand, and<br />

Holocene floodplain alluvium deposited by the<br />

Kuskokwim River are the two main c<strong>on</strong>tributors<br />

to the surficial geology in the vicinity of<br />

Figure 1 Locati<strong>on</strong> Map<br />

Nunapitchuk. A water well, drilled near the<br />

Bethel airfield, encountered 130 m of<br />

predominately frozen deltaic sediments.<br />

Nunapitchuk has been mapped as lying in the<br />

area underlain by c<strong>on</strong>tinuous permafrost.<br />

The Nunapitchuk Airport is located<br />

approximately three-quarters of a mile<br />

northeast of the village <strong>on</strong> the north side of<br />

the Johns<strong>on</strong> River (Figure 2). The airport is<br />

situated <strong>on</strong> some of the <strong>on</strong>ly high ground in the<br />

area that c<strong>on</strong>tains sufficient room to develop<br />

an airport facility. Even so, the average<br />

airport elevati<strong>on</strong> is less than two m above the<br />

surrounding lakes and sloughs.<br />

1256

Figure 2<br />

SOILS<br />

Airport Layout<br />

A subsurface field investigati<strong>on</strong> of the<br />

proposed alignment was c<strong>on</strong>ducted in February<br />

and March of 1983 by pers<strong>on</strong>nel from the Alaska<br />

Department of Transportati<strong>on</strong> and Public<br />

Facilities (DOT/PF) Materials Secti<strong>on</strong> (Pavey,<br />

1983). Five test holes were placed al<strong>on</strong>g the<br />

alignment of the proposed embankments. The<br />

holes were advanced using a Mobile E-24 auger<br />

drill. The test holes were sampled using<br />

modified Shelby tubes - standard Shelby tubes<br />

with carbide chips brazed to the tip to provide<br />

cutting teeth. A fifth test hole was drilled<br />

with solid flight auger. Samples were taken<br />

from the auger flights.<br />

Frost polyg<strong>on</strong>s were evident al<strong>on</strong>g the northern<br />

Gr Org/SI w/wood<br />

and southern thirds of the runway alignment.<br />

Test holes advanced al<strong>on</strong>g the alignment<br />

encountered a layer of frozen organics that<br />

overlaid ice or silt and ice combinati<strong>on</strong>s<br />

c<strong>on</strong>taining an estimated 50% or more visible Figure 3 Test Hole<br />

ice. The silt and ice also c<strong>on</strong>tained organic<br />

matter. Figure 3 provides a profile of an embankments, special design c<strong>on</strong>Gderati<strong>on</strong>s were<br />

example test hole.<br />

employed. Several embankment soluti<strong>on</strong>s were<br />

initially evaluated: 1) 1.2 m of silty sand<br />

A subsequent field investigati<strong>on</strong> was c<strong>on</strong>ducted material, 2) embankment with 0.10 to 0.15 m of<br />

in November, 1983 to locate a suitable source insualti<strong>on</strong>, and 3) embankment with a passive<br />

of embankment material. The nearest site was refrigera ti<strong>on</strong> system (thermosyph<strong>on</strong>s) without<br />

identified <strong>on</strong> a gently rolling barren plain insulati<strong>on</strong>.<br />

approximately 10 km northeast of the proposed<br />

airport (Figure 4). The usable porti<strong>on</strong> of the To estimate the l<strong>on</strong>g term settlement for the<br />

borrow site c<strong>on</strong>tained sand to silty sand that various design alternatives the thermal porti<strong>on</strong><br />

was perennially frozen a varying depths below<br />

the active layer. However, the relatively low<br />

moisture c<strong>on</strong>tent and silt c<strong>on</strong>tent as well as<br />

the laboratory compacti<strong>on</strong> test results<br />

indicated that this site was the most viable<br />

for use as embankment fill <strong>on</strong> the project.<br />

DES I GN<br />

The scope of the project included embankment<br />

c<strong>on</strong>structi<strong>on</strong> of a 36.6 by 762 m runway safety<br />

area, a 12.2 by 621 m taxiway, a 30.5 by 61 m<br />

aircraft parking apr<strong>on</strong>, and a 4.3 by 366 m<br />

access road (Figure 2). All embankments were<br />

designed to be c<strong>on</strong>structed by overlaying the<br />

natural ground cover. Due to ice rich<br />

materials below the surface of the proposed<br />

1257<br />

Sta.<br />

M.C.* 156.0%<br />

M.C.= 54.6%<br />

I% Grl<br />

12% Sa<br />

87% Si<br />

T.H. 2<br />

9+00 R/WE<br />

02/2W83<br />

Ice W/SQmO Sa<br />

Bn Org w/wood<br />

of a roadway life-cycle costing computer<br />

program developed by Woodward-Clyde C<strong>on</strong>sultants<br />

-(Kulkarni et dl., 1982) for the Alaska<br />

Department of Transportati<strong>on</strong> and Public<br />

Facilites was used. The program uses<br />

iterati<strong>on</strong>s of the Modified Berggren Equati<strong>on</strong><br />

(USA Army, 1968) for multiple years, taking<br />

into account the amount of thaw c<strong>on</strong>solidati<strong>on</strong><br />

and embankment settlement that will occur in a<br />

given year. To do this, the program calculates<br />

the settlement based <strong>on</strong> the input of initial<br />

and final void ratios and subtracts the<br />

settlement from the thickness of the<br />

c<strong>on</strong>solidating layer. The thermal properties of<br />

the c<strong>on</strong>solidated layer are adjusted to account<br />

€or the change in moisture c<strong>on</strong>tent. The<br />

program also calculates any talik that may form

TIME - YEARS<br />

c<br />

0.4<br />

I-<br />

Figure 5 Embankment Settlement Due to<br />

Underlying Silt <strong>Permafrost</strong> Thaw<br />

Figure 4<br />

Borrow Area and Haul Route<br />

in the thawed permafrost from <strong>on</strong>e year to the<br />

next and inputs into the calculati<strong>on</strong>s as a<br />

thawed layer.<br />

In the absence of air temperature at the site,<br />

air temperature data recorded at the Bethel<br />

Airport (Alaska DOT/PF, 1982 ) 40 km eastsoutheast<br />

of Nunapitchuk was used as input to<br />

the program. The average freezing index for<br />

Bethel is 1957OC-days with and average air<br />

thawing index of 137l0C-days which results in<br />

an average annual temperature of -1.7O C. A<br />

surface n-factor of 1.4 was chosen based <strong>on</strong><br />

back-calculated results €or gravel surfaced<br />

runways (Esch, 1984) .<br />

Two subsurface c<strong>on</strong>diti<strong>on</strong>s were analyzed and<br />

were selected to provide a range of expected<br />

thaw settlements. The first included a<br />

subsurface soil permafrost with 67% moisture<br />

c<strong>on</strong>tent with an estimated strain of 50% up<strong>on</strong><br />

thawing (Nels<strong>on</strong>, et al., 1983). The other<br />

included a layer of pure ice as would be found<br />

in the ice wedges. Both were overlain with 0.5<br />

feet of peat. The silty sand and sand<br />

embankment was to be c<strong>on</strong>structed in the frozen<br />

c<strong>on</strong>diti<strong>on</strong> with a 40% moisture c<strong>on</strong>tent and an<br />

estimated 25% c<strong>on</strong>solidati<strong>on</strong> up<strong>on</strong> thawing.<br />

Thermal properties of the soils were based <strong>on</strong><br />

data developed by Kefsten, 1949. Calculati<strong>on</strong>s<br />

were performed for the c<strong>on</strong>servative sand<br />

embankment alternative. The design<br />

alternatives were evaluated for each c<strong>on</strong>diti<strong>on</strong>:<br />

1) no insulati<strong>on</strong>, 2) 0.10 m of insulati<strong>on</strong>, and<br />

3) 0.15 m of insulati<strong>on</strong>. Figures 5 and 6 show<br />

the results of the calculati<strong>on</strong>s with cumulative<br />

embankment settlement plotted versus time in<br />

years. These show that for the uninsulited<br />

secti<strong>on</strong> the expected settlement was 3.7 m in 20<br />

years; for 0.10 m insulati<strong>on</strong> board, 0.24 m; and<br />

0.15 m of insulati<strong>on</strong> board, 0.15 m. The<br />

thermosyph<strong>on</strong> alternative was assumed to<br />

experience negligible settlement.<br />

1258<br />

0<br />

TIME - YEARS<br />

I ,o 1.5 20<br />

1<br />

0.10 METERS INSULATION-)<br />

v) 0.15-.<br />

E<br />

w<br />

k-<br />

w<br />

ai<br />

I 0.30.-<br />

k<br />

3<br />

t<br />

W<br />

0.45-<br />

I-<br />

3<br />

1 1 IN<br />

7.8 METERS<br />

15YEgRS<br />

0.60<br />

Figure 6 Embankment<br />

underlying Ice Thaw<br />

-0.15 METERS INSULATION<br />

settlement Due to<br />

After cost estimates and 20 year settlement<br />

rates for the three proposed soluti<strong>on</strong>s were<br />

assembled, a minimum 1.22 m embankment secti<strong>on</strong><br />

with 0.10 m of insulati<strong>on</strong> board placed 0.61 m<br />

below the top of the finished subgrade was<br />

selected as the basic bid €or the project. An<br />

additi<strong>on</strong>al 0.05 m of insulati<strong>on</strong> was bid as an<br />

additive alternate. The basic bid had an<br />

e timated quantity of insulati<strong>on</strong> board of 3,512<br />

m9 with an additivg alternate potentially<br />

adding another 1,755 m .<br />

Since access to the borrow area was across<br />

lakes and sloughs, the kmbankment had to be<br />

c<strong>on</strong>structed in the winter. Because of this and<br />

the anticipated l<strong>on</strong>g term settlements, an<br />

insulati<strong>on</strong> board with a minimum density of<br />

37.64 Kg/m3 and a minimum compressive strength<br />

of 418.8 kPa was specified. The insulati<strong>on</strong>

oard was also required to have a maximum water<br />

absorpti<strong>on</strong> 0.6% by volume (ASTM D2842-69) and a<br />

aximum thermal c<strong>on</strong>ductivity of 0.030 cal/m-hr-<br />

% .<br />

To m<strong>on</strong>itor embankment settlement, settlement<br />

platforms were intalled to -rest <strong>on</strong> the natural<br />

ground prior to c<strong>on</strong>structi<strong>on</strong> of the embankment.<br />

Each was fitted with a center rod driven 4 m<br />

into the natural ground for reference.<br />

Prior to the placement of the Eirst lift of<br />

material over the original ground, snow was<br />

removed down to the existing vegetative mat<br />

(tundra). During snow removal, specificati<strong>on</strong>s<br />

required the c<strong>on</strong>tractor to utilize low ground<br />

pressure equipment in order to minimize any<br />

damage to the tundra. Any c<strong>on</strong>solidati<strong>on</strong> or<br />

tearing of the tundra would reduce its<br />

insulative value thus allowing a faster<br />

degradati<strong>on</strong> of the underlying permafrost.<br />

Since the embankments were to be c<strong>on</strong>structed<br />

during the winter, it was anticipated that<br />

frozen chunks of material would be incorporated<br />

into the embankments. However, the size of the<br />

chunks were specified not to exceed 0.45 m in<br />

any dimensi<strong>on</strong> with a 0.15 m layer of unfrozen<br />

material placed directly below and above the<br />

insulati<strong>on</strong>. The purpose of the lower 0.15 m<br />

lift of unfrozen material was to provide a<br />

level surface with c<strong>on</strong>tinuous bearing for<br />

placement of the insulati<strong>on</strong> boards. The upper<br />

unfrozen 0.15 m lift would reduce the damage<br />

from frozen material as it was placed <strong>on</strong> the<br />

insulati<strong>on</strong>,<br />

It was anticipated that the frozen chunks of<br />

material incorporated in the embankment could<br />

not be initially compacted to maximum density.<br />

To account for the expected settlement of the<br />

embankment material up<strong>on</strong> thawing, it was<br />

specified that the c<strong>on</strong>tractor c<strong>on</strong>struct all<br />

embankments 0.31 m higher than finish subgrade<br />

elevati<strong>on</strong>s shown <strong>on</strong> the plans. If the 0.31 m<br />

of c<strong>on</strong>solidati<strong>on</strong> was not realized, then new<br />

grades and elevati<strong>on</strong>s were to be established in<br />

the field by the Engineer.<br />

Since moisture c<strong>on</strong>trol for the embankment<br />

material would be difficult during the winter<br />

m<strong>on</strong>ths, the specificati<strong>on</strong>s required that the<br />

c<strong>on</strong>tractor route his earthmoving equipment over<br />

the frozen embankment material in an effort to<br />

break and compact the frozen chunks.<br />

Compacti<strong>on</strong> testing was waived <strong>on</strong> embankment<br />

material placed during freezing weather.<br />

However, material placed above the insulati<strong>on</strong><br />

board was required to be compacted when thawed<br />

using .the necessary equipment to achieve a<br />

minimum of 95% laboratory density.<br />

After completi<strong>on</strong> and acceptance of the<br />

embankments to finish subgrade, the design<br />

called for the c<strong>on</strong>structi<strong>on</strong> of a 0.15 m lift of<br />

crushed aggregate surface course to be placed<br />

over the runway, taxiway, access road and<br />

apr<strong>on</strong>. Material required for the aggregate<br />

surface course had to be obtained from a source<br />

over 200 km from the project. Barging of the<br />

material provided the <strong>on</strong>ly viable means of<br />

transporting the aggregate surface course<br />

material.<br />

1259<br />

Due to the favorable bids <strong>on</strong> the basic c<strong>on</strong>tract<br />

which included 0.10 m of insulati<strong>on</strong> board , the<br />

additive alternate of 0.05 m of additi<strong>on</strong>al<br />

insulati<strong>on</strong> board was also awarded. The total<br />

bid for the project was $2,917,810.00 (USA).<br />

CONSTRUCTION<br />

After the tundra and surrounding sloughs and<br />

lakes had frozen sufficiently (early February<br />

1985) to support earthmoving equipment, the<br />

c<strong>on</strong>tractor of€ loaded his equipment from the<br />

barge and proceeded to c<strong>on</strong>struct a 10 km haul<br />

road from the borrow area to the airport.<br />

Minimal work was required for the haul road as<br />

the smooth slough and lake ice provided<br />

excellent road surfaces and the tundra between<br />

was level enough that <strong>on</strong>ly minor grading was<br />

necessary.<br />

On February 25, the c<strong>on</strong>tractor began hauling<br />

and placing the embankment three days after<br />

commencing the stripping of unusable material<br />

from the borrow area. The size of the frozen<br />

silty-sand chunks placed in the embankment<br />

beneath the insulati<strong>on</strong> board were generally<br />

kept below 0.45 m in any dimensi<strong>on</strong> as required<br />

in the specificati<strong>on</strong>s. The chunks larger than<br />

0.45 m in any dimensi<strong>on</strong> were bladed off to the<br />

embankment slopes. The 0.15 m of material<br />

placed directly below and above the insulati<strong>on</strong><br />

was not entirely thawed as required by the<br />

specificati<strong>on</strong>s due to the variati<strong>on</strong>s in<br />

moisture c<strong>on</strong>tent of the silty sand and the<br />

mixing of frozen and unfrozen material at the<br />

borrow area during stockpiling. However ,<br />

enough unfrozen material was available beneath<br />

the insulati<strong>on</strong> board to ensure a good bearing<br />

surface. Above the insulati<strong>on</strong> board the first<br />

lift of material placed had to be increased in<br />

thickness from the specified 0.15 m to<br />

approximately 0.45 m. This prevented the<br />

frozen chunks from shoving the insulati<strong>on</strong> board<br />

during placement.<br />

The insulati<strong>on</strong> board used in the project was ,<br />

Dow Chemical Company Stytrofoam HI 60. Due to<br />

the large quantity of insulati<strong>on</strong> board required<br />

and the arctic winter c<strong>on</strong>diti<strong>on</strong>s in which it<br />

had to be placed, the c<strong>on</strong>tractor obtained 0.08<br />

by 0.61 by 2.4 m boards rather than the<br />

standard 0.05 by 0.61 by 2.4 m boards. By<br />

reducing the insulati<strong>on</strong> to two layers rather<br />

than three, the manual labor was 30% less and<br />

the chance of damaged boards was reduced.<br />

During this first phase of c<strong>on</strong>structi<strong>on</strong>, the<br />

weather was typical for the winter m<strong>on</strong>ths at<br />

Nunapitchuk. Temperaturee varied from -37 OC<br />

to 3' C. The c<strong>on</strong>structi<strong>on</strong> of the embankment<br />

And insulati<strong>on</strong> was started in March 19, 1985<br />

with completi<strong>on</strong> <strong>on</strong> April 10, 1985. The frozen<br />

material above the insulati<strong>on</strong> was allowed to<br />

thaw and then graded and compacted before<br />

placement of the aggregate surface layer.<br />

INSTRUMENTATION<br />

TO m<strong>on</strong>itor and evaluate the performance of the<br />

runway embankment, two thermistor strings were<br />

installed in the fall of 1985. The strings<br />

were fabricated in such a way that the point at<br />

which the string penetrated the insulati<strong>on</strong> was<br />

1.22 m away from the point at which the<br />

measurements were to be taken. To do this and

EMBANKMENT<br />

SURFACE<br />

. . . .- .<br />

THERMISTOR<br />

STAGGERED INSULATION<br />

JOINTS<br />

15cm I nsu1ati<strong>on</strong>I<br />

Embankment<br />

STRING<br />

Frozen Peat<br />

I<br />

.. .<br />

ELEVATION<br />

Frozen Silt<br />

Figure 7 Thermistor Detail to Prevent Thermal<br />

Short Through Insulati<strong>on</strong><br />

measure the temperatures above the insulati<strong>on</strong>,<br />

a cable was c<strong>on</strong>structed with two ends - <strong>on</strong>e<br />

above the insulati<strong>on</strong> and <strong>on</strong>e below (Figure 7).<br />

This was to prevent a thermal short through the<br />

insulatiori from occuring at the point of<br />

interest. In each cable 13 YSI 440034<br />

thermistors were used.<br />

To install each cable, the silty sand above the<br />

insulati<strong>on</strong> was removed exposing six of the<br />

upper layer 0.075 m thick boards of insulati<strong>on</strong><br />

which were removed. This exposed <strong>on</strong>e complete<br />

board of the Lower layer of insulati<strong>on</strong> which<br />

was also removed. The underlying silty sand<br />

layer was totally frozen, indicating that no<br />

thaw had occurred through the summer of 1985.<br />

A 1.5 m boring was then drilled adjacent to the<br />

edge of the removed insulati<strong>on</strong> panel with a<br />

Survgyor Drill. The adjacent boards of 37.64<br />

Kg/m insulati<strong>on</strong> were able to support the drill<br />

stand and down pressure from the blade of the<br />

tractor without noticeable compressi<strong>on</strong>. The<br />

lower end of the thermistor string was placed<br />

in the hole and run al<strong>on</strong>g the surface of the<br />

exposed silty sand to the other edge of the<br />

panel and brought up through the joint (Figure<br />

7). The lower board was replaced and the cable<br />

run across the lower insulati<strong>on</strong> layer to the<br />

next joint and up to the surface of the<br />

insulati<strong>on</strong>. The upper end of the cable was<br />

placed al<strong>on</strong>g the top of the insulati<strong>on</strong> back to<br />

the boring and brought to the surface of the<br />

embankment as the hole was backfilled. The<br />

cable was then extented to the edge of the<br />

embankment in a trench al<strong>on</strong>g the top of the<br />

insulati<strong>on</strong>, ending in a multiple positi<strong>on</strong><br />

switch.<br />

EVALUATION<br />

Figure 8 shows the temperatures of thermistor<br />

string No. 2 <strong>on</strong> April 21 and October 15, 1987.<br />

The output switch <strong>on</strong> string No. 1 could not be<br />

located and it was later learned that it had<br />

Figure 8<br />

Embankment Temperature Profiles<br />

been destroyed during c<strong>on</strong>structi<strong>on</strong>. The May<br />

readings <strong>on</strong> thermistor string No. 2 show the<br />

silty sand embankment to be completely refrozen<br />

both above and below the insulati<strong>on</strong>. The<br />

October readings also show no thaw below the<br />

insulati<strong>on</strong>. Two test pits were dug and the<br />

thaw below the insulati<strong>on</strong> was measured in both<br />

to be 0.10 m. Calculati<strong>on</strong>s using the thermal<br />

properties for the silty sand indicated a thaw<br />

depth of 0.15 m. If the sand is assumed to<br />

settle 25%, these numbers are in reas<strong>on</strong>able<br />

agreement.<br />

CONCLUSIONS<br />

At this point in time, it appears that the<br />

c<strong>on</strong>cept of c<strong>on</strong>trolled subsidence (Berg, 1971)<br />

or allowing limited settlements of an insulated<br />

embankment over the life of the project and releveling<br />

the surface as needed, will be<br />

successful.<br />

ACKNOWLEDGMENTS<br />

The authors would like to thank V. S. Rader for<br />

his help with the thermal calculati<strong>on</strong>s and T.<br />

R. Ottley for performing the materials<br />

investigati<strong>on</strong>.<br />

REFERENCES<br />

Alaska Department of Transportati<strong>on</strong> & Public<br />

Facilities, (1983), Nunapitchuk Airport<br />

Staff Report, Internal report.<br />

Alaska Department of Transportati<strong>on</strong> & Public<br />

Facilities, (1984), Nunapitchuk Airport<br />

c<strong>on</strong>structi<strong>on</strong> plans and specificati<strong>on</strong>s.<br />

Alaska Department of Transportati<strong>on</strong> & Public<br />

Facilities, (1989-861, Daily & weekly<br />

c<strong>on</strong>structi<strong>on</strong> reports.<br />

1260

*-rotectl<strong>on</strong> of Warm <strong>Permafrost</strong> Using C<strong>on</strong>trolled Subsidence<br />

at Nunapitchuk Airport<br />

Berg, R.L., (1971), C<strong>on</strong>trolled subsidence of<br />

embankments <strong>on</strong> permafrost, Paper for<br />

Advanced Foundati<strong>on</strong> Engineering Class,<br />

University of Alaska, Fairbanks.<br />

Esch, D.C., (1986), Evaluati<strong>on</strong> of insulated<br />

highway and airport embankments. Alaska<br />

Departmeht of Transportati<strong>on</strong> and Public<br />

Facilities Report No. AK-RD-86-34.<br />

Kersten, M.S., (1949) , Thermal properties of<br />

soils. Univ. of Minnesota, Engineering<br />

Experiment Stati<strong>on</strong>, Bull. 28.<br />

Kulkarni, R., Saraf, C. Finn, F., Hilliard, J.<br />

and Van Til, C., (1982), Life cycle<br />

costing of paved Alaskan highways, Vol. I<br />

& II., Alaska Department of Transportati<strong>on</strong><br />

& Public Facilities, Report No. AK-RD-83-<br />

6.<br />

Nels<strong>on</strong>, R.A. , Luscher, U., Ro<strong>on</strong>ey, L.W. and<br />

Stramler, A.R., (1983), Thaw strain data<br />

and thaw settlement: predicti<strong>on</strong>s for<br />

Alaskan soils, Proceedings of the Fourth<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>,<br />

Fairbanks, pp. 912-917.<br />

Pavey, D.R., (1983), Centerline and borrow<br />

materials report for Nunapitchuk Airport,<br />

Alaska Department .of Transportati<strong>on</strong> and<br />

Public Facilities.<br />

U.S. Departments of the Army and Air Force,<br />

(19661 Arctic and Subarctic<br />

c<strong>on</strong>structi<strong>on</strong> -calculati<strong>on</strong> methods fox<br />

depths of freeze and thaw in soil. TM-5-<br />

852-6.<br />

1261

THERMAL PERFORMANCE OF A SHALLOW UTILIDOR<br />

F.E. Kennedy, C. Phetteplace, N. Humist<strong>on</strong> and V. Prabhakar<br />

Dartmouth College, Banover, New Hampshire, USA<br />

SYNOPSIS The thermal performance of a shallow burial utilidor design in central Alaska was studied<br />

by both field measurements and an analytical (finite element) model. Temperatures within the utilidor<br />

and in the soil surrounding it were m<strong>on</strong>itored from mid-1985 until mid-1587. The utilidor interior te<br />

eratures remained well above O'C even in the coldest weather and soil beneath and adjacent to the utilidor<br />

remained unfrozen, The pattern of ground freezing in the immediate vicinity of the utilidor was<br />

significantly affected by heat flowing from the utilidor, but ground temperatures more than 6 about m<br />

from the utilidor were relatively unaffected. The transient finite element analysis gave very good p<br />

dicti<strong>on</strong>s of Soil temperatures in the utilidor reqi<strong>on</strong>.<br />

INTRODUCTION<br />

utilidor. A preliminary analysis of the utilidor<br />

which had been d<strong>on</strong>e prior to c<strong>on</strong>structi<strong>on</strong><br />

A comm<strong>on</strong> method of utility distributi<strong>on</strong>, es- (Phettepldce, et al, , 1986) indicated that temppecially<br />

in cold climates, is the utility cor- eratures below freezing could occur within the<br />

ridor, or utilidor. The utilidor could c<strong>on</strong>tain utilidor during the coldest winter m<strong>on</strong>ths. That<br />

water and sewer pipes, electric and teleph<strong>on</strong>e analysis prompted the designers to add extra<br />

cables, and pipes for high temperature water or insulati<strong>on</strong> around the c<strong>on</strong>crete utilidor and to<br />

steam and c<strong>on</strong>densate. In very cold regi<strong>on</strong>s, add an uninsulated steam trace inside the utilsuch<br />

as Alaska, measures must be taken to keep idor which would heat the interior when necesthe<br />

utilidor's interior temperatures above sary. The purpose of the present study was to<br />

freezing and to limit heat loss from the util- 1) determine whether those measures were<br />

idor during winter. These measures could in- successful in keeping utilidor temperatures<br />

clude insulati<strong>on</strong> of the utilidor and inclusi<strong>on</strong> above freezing and whether the steam trace was,<br />

of steam traces to heat the water and sewer in fact, required, and 2) study the soil temppiping<br />

eratures around the utilidor to see what effect<br />

Utility corridors can be built either above the heat sources in the utility corridor had <strong>on</strong><br />

or below ground. Buried utilidors have a those temperatures. The locati<strong>on</strong> of the 0°C<br />

distinct thermal advantage in severe climates. isotherm which separates frozen from unfrozen<br />

High c<strong>on</strong>structi<strong>on</strong> costs, however, al<strong>on</strong>g with soil was of particular interest.<br />

high groundwater levels, interference with<br />

existing utilities, or the presence of perma- The work involved two phases: 1) a field<br />

frost may preven the deep burial of utilidors. study involving instrumentati<strong>on</strong> of the utilidor<br />

Excavati<strong>on</strong> in permafrost is costly and problems with sensors to measure actual heat flows and<br />

could occur if a heated utilidor was placed in temperatures, and 2) a numerical model of the<br />

such soils. One of the few analyses of buried thermal performance of the utilidor and surutilidor<br />

performance in a permafrost regi<strong>on</strong> was rounding soil. The thermal analysis was used to<br />

that of Zirjacks and Huang (1983), which des- calculate temperatures where sensors could not<br />

cribed an underground utilidor in Barrow, be placed and to predict accurate temperature<br />

Alaska. Excavati<strong>on</strong> of the permafrost for that profiles in the soil surrounding the utilidor.<br />

utilidor required c<strong>on</strong>siderable blasting. Although<br />

the utilidor was insulated and heated by<br />

hot water, utilidor air temperatures frequently UTILIDOR SYSTEM AND INSTRUMENTATION<br />

dropped below O°C during cold weather.<br />

An alternative to above-ground or deep burial The porti<strong>on</strong> of the utilidor system being<br />

utilidor designs is a shallow burial design in studied c<strong>on</strong>tains all utilities with the exwhich<br />

the bulk of the corridor is below ground cepti<strong>on</strong> of electrical power lines, which are<br />

but its top cover is at or above ground surface overhead. The utilidor is over 2 kilometers<br />

level, While the initial cost of c<strong>on</strong>structi<strong>on</strong> l<strong>on</strong>g and was c<strong>on</strong>structed 1984 in and 1985 in an<br />

of the shallow burial design would be much less area of interior Alaska which lies in a disthan<br />

that of the more typical deep burial c<strong>on</strong>tinuous permafrost z<strong>on</strong>e (Williams, 1970).<br />

design, problems could occur due to exposure of The soil at that locati<strong>on</strong> is predominantly<br />

the top of the utilidor to extreme climatic gravel, covered by a thin (< 25 cm) layer of<br />

c<strong>on</strong>diti<strong>on</strong>s. One such shallow utilidor has peat. The groundwater level at the site is<br />

recently been c<strong>on</strong>structed in interior Alaska, approximately 2.5 m below grade and all utilidor<br />

where the outside air temperature could drop to excavati<strong>on</strong> was well above that level.<br />

as low as -5OOC in winter. The purpose of this The utilidor is a rectangular c<strong>on</strong>crete tunnel<br />

work was to study the thermal behavior of that with a 250 cm by 80 crn interior cross secti<strong>on</strong>.<br />

1262

Rigid<br />

Ins1<br />

it yl<br />

BC<br />

Figure 1. Cross secti<strong>on</strong> of utilidor at site A, showing placement Of<br />

temperature sensors. A11 numbers refer to thermocouples<br />

except 114 and 115, which are heat flow sensors.<br />

The 15 cm thick walls of the utilidor have 5 cm acquisiti<strong>on</strong> system. The main comp<strong>on</strong>ent of this<br />

of extruded polystyrene insulati<strong>on</strong> <strong>on</strong> their system wad located in the mechanical room of a<br />

exterior surface; the 10 cm lid is lined with 5 building served by the utilidor. The thermocm<br />

of extruded polystyrene insulati<strong>on</strong> and 1.25 couples were c<strong>on</strong>nected to a waterpqoof "extender<br />

crn of plywood <strong>on</strong> its interior surface. The 20 chassis" at each site. These c<strong>on</strong>verted the<br />

cm thick base of the utilidor is uninsulated. analog signals from the sensor3 into digital<br />

The pipes and c<strong>on</strong>duits within the utilidor arc signals.. The' digital signals were transmitted<br />

supported at regular intervals by supports which via a multic<strong>on</strong>ductor communicati<strong>on</strong> cable from<br />

keep the pipes at least 15 cm above the c<strong>on</strong>crete each extender chassis to the main frame data<br />

floor. Figure 1 shows a cross secti<strong>on</strong> of the acquisiti<strong>on</strong> system. Since site a was approxutilidor<br />

at <strong>on</strong>e of the sites studied.<br />

imately 225 meters from the mechanical room<br />

The steam, c<strong>on</strong>densate and water pipes within where the data acquisiti<strong>on</strong> was located and the<br />

the utilidor are insulated, The 30 cm. diameter other site was over 300 meters away, such a<br />

steam pipe is covered with 5 crn of fiberglass system greatly reduced the cost of extending the<br />

insulati<strong>on</strong>. The c<strong>on</strong>densate pipe (15 cm much more expensive thermocouple wires. Another<br />

diameter) is wrapped with 3.75 cm of fiberglass reas<strong>on</strong> for using this system was the ability of<br />

insulati<strong>on</strong>. The 30 cm water pipe is insulated the extender chassis to operate in the extreme<br />

with 3.75 cm of polyisocyanurate. The fire envir<strong>on</strong>mental c<strong>on</strong>diti<strong>on</strong>s found within the<br />

(water) and sewer pipes are uninsulated. An utilidor system.<br />

uninsulated 2.5 cm steam trace was also in- The data acquisiti<strong>on</strong> system was microstalled<br />

within the utilidor to heat the util- processor c<strong>on</strong>trolled and fully programmable.<br />

idor in the event that below freezing temp- This allowed for a great deal of flexibility in<br />

eratures were encountered in its interior. data acquisiti<strong>on</strong>. Data were recorded <strong>on</strong><br />

Thermostatic c<strong>on</strong>trol was used <strong>on</strong> each segment of magnetic tape for ease of transfer to our<br />

the steam trace to reduce energy c<strong>on</strong>sumpti<strong>on</strong>. computer for reducti<strong>on</strong> and analysis. Data also<br />

The steam trace was not activated during the could be printed <strong>on</strong> site by the data acquisiti<strong>on</strong><br />

course of this study.<br />

system to allow for periodic inspecti<strong>on</strong> of<br />

During the c<strong>on</strong>structi<strong>on</strong>, two secti<strong>on</strong>s of the utilidor and data acquisiti<strong>on</strong> system operati<strong>on</strong>s.<br />

utilidor and the soil around those secti<strong>on</strong>s were Data acquisiti<strong>on</strong> began at both site9 in<br />

extensively instrumented with thermocouples and August 1985 and were collected nearly<br />

heat flow sensors. About fifteen thermocouples c<strong>on</strong>tinuously until. July 1987.<br />

and two heat flow sensors were installed within<br />

the utilidor at each of the two sites. The<br />

locati<strong>on</strong>s of the thermocouples and heat flow<br />

'sensors within the utilidor at site A are shown<br />

in Figure 1. In additi<strong>on</strong> to the instrumentati<strong>on</strong><br />

6m<br />

within the utilidor, over fifty thermocouples<br />

were positi<strong>on</strong>ed in the soil around the utilidor<br />

1<br />

at each site and two more thermocouples were<br />

used to m<strong>on</strong>itor the outside air temperature. 1<br />

The locati<strong>on</strong>s of soil thermocouples at site A<br />

Utilidor<br />

are shown in Figure 2. The soil thermocouple<br />

strings were implanted in the summer of 1985<br />

#I<br />

and, while drilling holes for those thermocouples,<br />

frozen ground was encountered at depths<br />

Thermocouple<br />

ranging from 2 to 3.5 m. Several of the<br />

thermocouple locati<strong>on</strong>s were in the frozen<br />

ground. All thermocouples were made with<br />

20-gage copper c<strong>on</strong>stantan thermocouple wire and<br />

were read to a resoluti<strong>on</strong> of approximately f<br />

0.1OC. The heat flow sensors had a sensitivity<br />

of 63 W/m2 mv.<br />

The sensors at each af the two sites were<br />

m<strong>on</strong>itored c<strong>on</strong>tinuously by an automatic data<br />

1263<br />

t 1<br />

Figure 2. Buried thermocouple cable locati<strong>on</strong>s;<br />

I )

TEMPERATURE MEASUREMENTS<br />

from a warm manhole, whereas a nearby warm<br />

manhole seems to have c<strong>on</strong>tributed to warmer<br />

Temperature and heat flow data were collected utilidor temperatures at site A.<br />

throughout the winter of 1985-86 and 1986-87. The relative stability of the utilidor<br />

Due to space limitati<strong>on</strong>s <strong>on</strong>ly a small porti<strong>on</strong> of' temperatures was also maintained during the<br />

the data is presented here.<br />

winter of 1986-87, which was more severe than<br />

The winter of 1985-86 was unusually mild at the <strong>on</strong>e preceding it. Plots of outdoor air<br />

the utilidor site in central Alaska, with out- temperature and utilidor air temperature at site<br />

door temperatures a the utilidor site averaging A are shown in Figure 4 €or the period 2 March<br />

above normal and seldom dropping below -30°C. to 18 March 1987, Despite large variati<strong>on</strong>s in<br />

The variati<strong>on</strong> in outdoor temperature during the outdoor temperatures, which reached as low as<br />

period 7 December 1985 to 21 January 1986 is -37OC, the utilidor air temperature remained<br />

shown in Figure 3, based <strong>on</strong> temperatures quite stable at between 34°C and 39'C at site A.<br />

measured daily at midnight and no<strong>on</strong>. C<strong>on</strong>sid- Again, temperatures inside the utilidor at site<br />

erable variati<strong>on</strong> in air temperature is evident, B were lower, reaching a minimum of 12'C <strong>on</strong> a<br />

especially during December 1985. The utilidor night in early March that was of <strong>on</strong>e the coldest<br />

interior temperatures at each of the instru- nights of the year. It was apparent from the<br />

mented sites were found to be much higher than measurements that, even in the coldest weather<br />

outside air temperatures. Figure 3 shows the and at the coldest site instrumented, the<br />

air temperature inside the utilidor at site A utilidor interior remained well above freezing<br />

during the same 1 1/2 m<strong>on</strong>th period. It can be without the need for a steam trace.<br />

seen that the interior temperatures at this site<br />

"r<br />

were quite stable throughout the period,<br />

generally remaining between 35OC. and 40°C.<br />

Interior temperatures at the other site (site B) '<br />

were also stable but were lower, ranging from<br />

13OC to 16OC in a cool corner of the utilidor<br />

and to 25OC nearer the steam pipe. The lower<br />

temperatures at site I3 were due to the fact that<br />

site B was nearer the end of the steam distributi<strong>on</strong><br />

circuit, so steam temperatures were lower<br />

there and the steam and c<strong>on</strong>densate pipes were<br />

smaller. In additi<strong>on</strong>, site B was relatively far<br />

_I<br />

Utilidor air tempersturea<br />

40t 120<br />

tnW E<br />

'OI<br />

0-<br />

4<br />

PE<br />

w<br />

n<br />

p -10.<br />

Outside air temperatures<br />

-20 '<br />

- 30<br />

-40 L<br />

I 1 I 1 1<br />

7 b C 17 Dec 27 Dec 6Jan 16-Jen 2 Mar 7 Mar 12 Mar 17 Mar<br />

DAYS<br />

DAYS<br />

Figure 3. Measured outside air temperatures and Figure 4. Measured outside air temperatures and<br />

utilidor air temperatures at site A<br />

utilidor air temperatures at site A<br />

during period from 7 Dec 1985 to 21<br />

during period from 2 Mar 1987 to 18<br />

Jan 1986. Readings taken daily at<br />

Mar 1987. Readings taken daily at<br />

00:30 and 12:30.<br />

00:12 and 12:12,<br />

1264

A study of the utilidor interior temperature:<br />

and heat flow measurements showed that both<br />

steam and c<strong>on</strong>densate return pipes c<strong>on</strong>tributed<br />

heat to the utilidor interior, with the heat<br />

flow from the steam pipe being about 25% greater<br />

than that from the c<strong>on</strong>densate pipe at site A.<br />

There was slightly more heat flow from the steam<br />

pipe at site B than at A, even though the steam<br />

pipe temperature was .lower at site B, but there<br />

was substantially less heat flow from the much<br />

cooler and smaller c<strong>on</strong>densate pipe at site E.<br />

C<strong>on</strong>siderable heat from the utilidor flowed<br />

into the surrounding soil, as was evident from<br />

measurements of soil temperatures. The thermocouple<br />

data were used to c<strong>on</strong>struct isotherms in<br />

the soil regi<strong>on</strong> around the utilidor and examples<br />

of the isotherms are shown in Figures 5 and 6.<br />

The dashed lines in Figure 5 are isotherms<br />

determined from measured soil temperatures at<br />

site A <strong>on</strong> 12 December 1985, while isotherms at<br />

the same site <strong>on</strong> 12 March 1987 are shown in<br />

Figure 6. It should be noted that the isotherms<br />

were c<strong>on</strong>structed <strong>on</strong>ly in the regi<strong>on</strong> enclosed by<br />

the 50 thermocouples shown in Figure 2, so they<br />

d<strong>on</strong>'t extend deeper than about 4 m below the<br />

ground surface and d<strong>on</strong>'t include the soil immediately<br />

adjacent to the utilidor. By comparing<br />

the December and March data it can be<br />

seen that the O'C isotherm was at a greater<br />

depth later in winter, but no freezing was<br />

observed in the soil beneath the utilidor even<br />

late in winter. Similar results were noted at<br />

site B, although the soil temperatures were<br />

slightly lower beneath the utilidor at site B.<br />

It is apparent from the isotherm spacing that<br />

there was a substantial amount of heat flowing<br />

radially outward from the utilidor and upward<br />

toward the colder ground surface at both sites.<br />

1.27<br />

M<strong>on</strong>itoring of all of the soil thermocouples<br />

began late in the summer of 1985 just after the<br />

utilido-r went into operati<strong>on</strong>. With two excepti<strong>on</strong>s,<br />

all of the thermocouples showed an<br />

increase in temperature during the August-<br />

September period and the <strong>on</strong>es that had been<br />

implanted in frozen ground had increased to<br />

above DOC by the end of August. Two Of the<br />

thermocouples that had been implanted in frozen<br />

soil at site B. however, remained at a c<strong>on</strong>stant<br />

temperature of -0.3'C throughout the two-m<strong>on</strong>th<br />

period just after installati<strong>on</strong>. Those thermocouples<br />

were located 2 m laterally from the<br />

utilidor at 3.5 to 4 m depth, After heat from<br />

the utilidor started reaching the two thermocouples,<br />

though, in late September 1985, those<br />

two temperatures started rising slowly and had<br />

reached above O°C by the end of November. They<br />

never again dropped below O°C during the remainder<br />

of the two-year study. It should be<br />

noted that the soil drill had encountered<br />

difficulty penetrating the frozen ground to<br />

depths greater than 3.75 m at that locati<strong>on</strong>.<br />

Based <strong>on</strong> these observati<strong>on</strong>s, it was c<strong>on</strong>cluded<br />

that there. had been a small patch of permafrost<br />

at that locati<strong>on</strong>, beginning at a depth of just<br />

over 3 m, but it thawed when heat from the<br />

utilidor reached it. N<strong>on</strong>e of the other soil<br />

thermocouples showed indicati<strong>on</strong>s of being in<br />

permafrost either' before or after the utilidor<br />

was in operati<strong>on</strong>. There was very little<br />

settlement of the utilidor of the soil around<br />

the utilidor. Comparis<strong>on</strong> of soil temperatures<br />

from the summer of 1985 with those measured in<br />

the summer of 1987 showed that locati<strong>on</strong>s within<br />

3 m of the utilidor were warmer by at least two<br />

degrees in 1987 than they had been at the time<br />

of utilidor c<strong>on</strong>structi<strong>on</strong> two years earlier.<br />

0.11<br />

E<br />

-1.06<br />

K<br />

Y<br />

-2- 22<br />

;<br />

5<br />

\ \ \<br />

-\<br />

,\<br />

\<br />

28<br />

;i<br />

-5.71<br />

X - DISTANCE (METERS)<br />

Figure 5 , Isotherms in soil around utilidor at<br />

site A <strong>on</strong> 12 Dec 1985. Dashed lines<br />

were determined from thermocouple<br />

readings at 0O:OO. Solid lines are<br />

based <strong>on</strong> finite element model<br />

predicti<strong>on</strong>s.<br />

-4.54<br />

-5.71<br />

/<br />

-6.87 1 I I I I I<br />

-6.87 -5.78 -4.54 -3.38 -2.21 -1.05 8.11 I.'<br />

X - DISTANCE (METERS)<br />

Figure 6. Isotherms in soil around utilidor at<br />

Site A <strong>on</strong> 12 Mar 1987. Dashed lines<br />

were determined from thermocouple<br />

readings at 0O:OO. Solid lines are<br />

based <strong>on</strong> finite element model<br />

predicti<strong>on</strong>s.<br />

1265

~<br />

x,<br />

Temperatures at a c<strong>on</strong>trol cable located 6 m from<br />

the utilidor were less affected by the presence<br />

of the utilidor, but were very slightly higher<br />

in July 1987 than they had been in August 1985.<br />

Although the measured data provided<br />

c<strong>on</strong>siderable informati<strong>on</strong> about temperatures and<br />

heat flows in and around the utilidor, more<br />

informati<strong>on</strong> was desired, especially in those<br />

locati<strong>on</strong>s where instrumentati<strong>on</strong> hadn't been<br />

installed. This informati<strong>on</strong> was obtained from<br />

an analytical model of heat transfer in the<br />

regi<strong>on</strong> of the utilidor.<br />

ANALYTICAL STUDY<br />

The finite element method was chosen for this<br />

analysis Of temperatures in the regi<strong>on</strong> surrounding<br />

the utilidor. A preliminary study of<br />

the temperature distributi<strong>on</strong> was carried out<br />

early in the utilidor design phase (Phetteplace<br />

et ala, 1986). Although that analysis proved<br />

useful in the design of the utilidor, its<br />

temperature predicti<strong>on</strong>s did not str<strong>on</strong>gly agree<br />

with data measured after the utilidor was<br />

c<strong>on</strong>structed. The preliminary analysis was a<br />

steady state analysis and it used boundary<br />

c<strong>on</strong>diti<strong>on</strong>s and soil properties that were <strong>on</strong>ly<br />

rough estimates. It was c<strong>on</strong>cluded that a<br />

transient thermal model was necessary in order<br />

to achieve improved accuracy (Phetteplace et<br />

aL., 1986) . In the present s.tudy a tyanslent<br />

analysis was run, with effects of soil freezing<br />

included,<br />

The finite element program used here was<br />

Thermap, a code that was developed at Dartmouth<br />

and had proven to give good temperature predicti<strong>on</strong>s<br />

for a wide variety of heat c<strong>on</strong>ducti<strong>on</strong><br />

problems (Glovsky, 1982). The program was<br />

modified for this project to account for latent<br />

heat effects in melting and freezing (Prabhakar,<br />

3987). The phase change algorithm used in the<br />

modified code was an efficient 'form of an<br />

equivalent heat capacity scheme developed<br />

recently by Hsiao and Chung (1986).<br />

Before applyin9 the program to the utilidor<br />

problem, an extensive numerical study was made<br />

of the effect of soil properties and boundary<br />

c<strong>on</strong>diti<strong>on</strong>s <strong>on</strong> soil temperatures in a <strong>on</strong>edimensi<strong>on</strong>al<br />

heat transfer situati<strong>on</strong> near the<br />

utilldos (Prabhakar, 1987). The soil whose<br />

thermal properties gave the best approximati<strong>on</strong><br />

to the measured temperatures in the soil near<br />

the utilidor was a coarse-grained soil with 10%<br />

moisture c<strong>on</strong>tent and. a dry unit mass of 2.2<br />

g/cm3. That soil type agrees well with soil<br />

prevalent at the utilidor site. Properties Of<br />

such a soil were tabulated by Lunardini (1981).<br />

The finite element mesh used in the final<br />

utilidor analysis for site A is shown in Figure<br />

7. It included 424 nodes and 387 elements.<br />

Fifty-<strong>on</strong>e of the nodes were at the same locati<strong>on</strong>s<br />

as buried thermocouples and they are shown<br />

by circles in Figure 7.. Because of symmetry,<br />

<strong>on</strong>ly half of the utilidor and the soil <strong>on</strong> that<br />

side were studied. The boundary c<strong>on</strong>diti<strong>on</strong>s<br />

included: zero heat flux c<strong>on</strong>diti<strong>on</strong>s <strong>on</strong> right<br />

and left sides, c<strong>on</strong>vecti<strong>on</strong> to ambient outside<br />

air at the top surface of the utilidor, measured<br />

thermocouple readings as prescribed temperature<br />

boundary c<strong>on</strong>diti<strong>on</strong>s <strong>on</strong> the inside wall of the<br />

utilidor and the top surface of the snow-covered<br />

ground, and an assumed c<strong>on</strong>stant temperature<br />

1266<br />

I<br />

I I I I 1 I<br />

I<br />

I I 1 t<br />

7 .O -2.75 1.5<br />

X - DISTANCE (METERS)<br />

Ficpre 7. Finite element mesh for thermal<br />

analysis of utilidor and surroundhg<br />

soil. Circles indicate thermocouple<br />

locati<strong>on</strong>s.<br />

boundary at a depth of 15 m below the ground<br />

surface.<br />

A transient analysis was run using the<br />

measured soil temperatures at the beginning Of a<br />

6-week test period as initial c<strong>on</strong>diti<strong>on</strong>s.<br />

During the transient analysis the C<strong>on</strong>stant<br />

temperature c<strong>on</strong>diti<strong>on</strong>s at the ground surface and<br />

utilidor wall, al<strong>on</strong>g with the ambient air<br />

temperature, were changed regularly to Corresp<strong>on</strong>d<br />

with measured values. Time steps for<br />

the transient analysis were chosen to insure<br />

that the freeze fr<strong>on</strong>t did not skip Over any<br />

elements during a single time increment.<br />

Computed temperature distributi<strong>on</strong>s at site A<br />

are shown by the solid .lines (isotherms) in<br />

Figures 5 and 6 for two representative days, 12<br />

December 1985 and 12 March 1987, respectively.<br />

Comparis<strong>on</strong> of the measured and predicted temperatures<br />

shows very good agreement, not just <strong>on</strong><br />

those two days but throughout the time periods<br />

studied (Prabhakar, 1987). In general, predicted<br />

temperatures differed by less than l0C<br />

from measured values and the locati<strong>on</strong>s of the<br />

O°C isotherm were nearly exactly the same as<br />

those determined from measured temperatures.<br />

In fact, the <strong>on</strong>ly temperatures which differed by<br />

more than 0 .l°C from measured values were those<br />

for several. thermocouple locati<strong>on</strong>s directly<br />

beneath the utilidor, and the exact locati<strong>on</strong>s of<br />

those thermocouples is questi<strong>on</strong>able because the<br />

thermocouple cable was disturbed during c<strong>on</strong>structi<strong>on</strong>.<br />

Agreement with measured soil temperatures<br />

was much better for these transient

analyses than had been the case for the earlier<br />

steady-state analysis (Phetteplace, et al.<br />

1986).<br />

The isotherms presented in Figures 5 and 6<br />

offer c<strong>on</strong>vincing evidence that no freezing<br />

occurs in the soil beneath or adjacent to the<br />

utilidor, irrespective of outdoor air<br />

temperature or time of year. The analysis<br />

predicts that soil temperatures reached 2'C or<br />

higher at depths down to at least 15 m in the<br />

regi<strong>on</strong> within 6 meters of the utilidor at site<br />

A. These temperatures would have a very<br />

significant effect <strong>on</strong> the annual patterns of<br />

freezing and thawing the of soil in that regi<strong>on</strong>.<br />

ACKNOWLEDGEMENTS<br />

The authors acknowledge and thank the<br />

following pers<strong>on</strong>s for their c<strong>on</strong>tributi<strong>on</strong>s:<br />

S. Lederman of the U .S. Army Corps of Engineers<br />

Alaska District, whose cooperati<strong>on</strong> and knowledge<br />

of the study sites were invaluable; H. Barger,<br />

Eiels<strong>on</strong> Energy Engineer, who was instrumental in<br />

obtaining funding and m<strong>on</strong>itoring the data<br />

collecti<strong>on</strong> system; and, finally, the W.S. Air<br />

Force for providing the funding for the field<br />

study.<br />

CONCLUSIONS<br />

REFERENCES<br />

The measurements and predicti<strong>on</strong>s of this work<br />

showed that temperatures within and around this Glovsky, R.P. (1982).<br />

Development and<br />

shallow utilidor did not drop below freezing at Applicati<strong>on</strong> of Thermap. Master of<br />

the sites instrumented, even during the cold<br />

Engineering Thesis, Thayer School of<br />

winter weather in central Alaska. The presence Enginepring,Dartmouth College,Hanover,NH.<br />

of a large steam pipe, even though it was insu- Hsiao, J.S. and Chung, B.T.F. (1986).<br />

An<br />

lated, kept utilidor interior air temperatures<br />

Efficient Algorithm for Finite Element<br />

above 30°C throughout the year at site A and<br />

Soluti<strong>on</strong>+to Two-Dimensi<strong>on</strong>aL Heat Transfer<br />

above 10°C at the colder site, site B. A steam<br />

with Melting and Freezing. ASME Journal of<br />

trace placed within the utilidor for emergency<br />

Heat Transfer (108), 462-464.<br />

heating of the corridor proved to be unneces- Lunardini, V. J. (1981). Heat Transfer In<br />

sary. Temperatures in the soil beneath and<br />

Cold Climates, Van Nostrand Reinhold, New<br />

adjacent to the utilidor were also kept above<br />

York<br />

O'C by heat c<strong>on</strong>ducted from the warm utilidor. Phetteplace,G., Richm<strong>on</strong>d,P. and Humist<strong>on</strong>,N.<br />

Soil temperatures beneath the utilidor at site A<br />

(1986). Thermal Analysis of a Shallow<br />

increased to above 2OC to depths of at Least 15<br />

Utilidor., Presented at 77th Annual<br />

m, preventing any freezing of that soil. There<br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> of <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> District Heating<br />

was evidence that a small patch of permafrost<br />

and Cooling Associati<strong>on</strong>, Asheville, NC.<br />

was initially present at a depth of slightly Prabhakar, V. (1987). Heat Transfer from<br />

over 3 m near the utilidor at site B. Whereas<br />

Utilidors. Master of Engineering Thesis,<br />

the temperature at that locati<strong>on</strong> had been<br />

Thayer School bf Engineering, Dartmouth<br />

c<strong>on</strong>stant at about -0.3OC for an extended period College, Hanover, NH.<br />

at the time of utilidor c<strong>on</strong>structi<strong>on</strong>, <strong>on</strong>ce heat Williams, J.R. (1970). Ground Water in the<br />

from the utilidor reached that regi<strong>on</strong> the<br />

<strong>Permafrost</strong> Regi<strong>on</strong>s of Alaska, U .S.<br />

temperature increased slowly to above O°C and<br />

Geological Survey Professi<strong>on</strong>al Paper # 696<br />

remained above freezing throughout the remainder Zirjacks, W.L. and Hwang, C.T. (1983)<br />

of the two-year study. At lateral distances of<br />

6 m from the utilidor the ground froze to depths<br />

of greater than 3 m during the winter, but even<br />

there the soil temperatures were slightly<br />

influenced by heat c<strong>on</strong>ducted from the utilidox<br />

and at greater depths the temperature remained<br />

above O'C.<br />

The transient finite element analysis used to<br />

predict temperatures around the utilidor proved<br />

to be quite accurate. Predicti<strong>on</strong>s of soil<br />

temperatures and O°C isotherm locati<strong>on</strong> agreed<br />

very well with measured values. At present the<br />

analysis relies <strong>on</strong> the specificati<strong>on</strong> of measured<br />

utilidor wall temperatures as time-varying<br />

boundary c<strong>on</strong>diti<strong>on</strong>s. Since those temperatures<br />

are not usually known a priori to the designer,<br />

the program is currently more useful as an<br />

analysis tool than as an aid in design. A more<br />

complete study of heat transfer within the<br />

utilidor is planned, with the goal being a<br />

better understanding of heat transfer coefficients<br />

from the various heat sources, such as<br />

steam pipes. This would eliminate the need for<br />

measured utilidor temperatures and would<br />

increase the effectiveness of the program as a<br />

utilidor design aid.<br />

Underground Utilidors at Barrow, Alaska: A<br />

Two-Year History. Proc. 4th Int'l C<strong>on</strong>f <strong>on</strong><br />

<strong>Permafrost</strong>, Nati<strong>on</strong>al Academy Press,<br />

Washingt<strong>on</strong>, DC, 1513-1517<br />

1267

CONSTRUCTION OF HYDROS IN COLD CLIMATE:<br />

ACHIEVEMENTS AND PROBLEMS<br />

L.I. Kudoyarov' and N.F. Kriv<strong>on</strong>ogovaz<br />

Whe V.V. Kuibyshev MISI, Moscow, USSR<br />

%The B.E. Vedeneev VNIIG, Leningrad, USSR<br />

SYNOPSIS Specific features of hydros under design, c<strong>on</strong>struAi<strong>on</strong> and operati<strong>on</strong> in cold climate are c<strong>on</strong>sidered<br />

to dem<strong>on</strong>strate the advances and urgent problems in estimating engineering geocryological c<strong>on</strong>diti<strong>on</strong>s of their foundati<strong>on</strong>s:<br />

-. lav-out and desian - soluti<strong>on</strong>s enswing safe performance of embankment and c<strong>on</strong>crete dams built <strong>on</strong> frozen and<br />

thawing foundati<strong>on</strong>s are looked into.<br />

Water powr resDurces of the Swi& Wrth are estimated<br />

to be 1,400 TWhr which accounts for 3746 of the total<br />

USSR hydro power resources. The swere climate, complex<br />

engineering geological c<strong>on</strong>diti<strong>on</strong>s (to a large extent<br />

determined by geocryological situati<strong>on</strong>), Lack of material<br />

bases in the uninhabited regi<strong>on</strong>s together with transport<br />

problems are resp<strong>on</strong>sible for difficulties in the development<br />

of the northern hydro power engineering, On the<br />

other hand, these very factors have stimulated the drive<br />

for finding new promising and. ec<strong>on</strong>omically effe'dtive solutio-<br />

rehted to the design and c<strong>on</strong>structi<strong>on</strong> of hydros in<br />

the Soviet North. The engineering geological c<strong>on</strong>diti<strong>on</strong>s<br />

are aggravated primarily due to the evoluti<strong>on</strong> of permafrost.<br />

At the valley stretches wedging into rock formati<strong>on</strong><br />

the transforming role of cryogen.esis shows up as the<br />

occurrence of upheaved z<strong>on</strong>es in the rock masses with<br />

inEerior physico-mechrlaical properties. Widespread <strong>on</strong><br />

the *ep slopes of the dam abutmefits and forebay porti<strong>on</strong>s<br />

of the reservoirs are st<strong>on</strong>e streams revealing their<br />

instability caused by the excavati<strong>on</strong> and change of rock<br />

thermal c<strong>on</strong>diti<strong>on</strong>s in the process of c<strong>on</strong>structi<strong>on</strong>. When<br />

dealing with semirocks distinguished for high ice c<strong>on</strong>tent<br />

and n<strong>on</strong>-uniform cryogenic structure <strong>on</strong>e may expect the<br />

rapid rise of deformability and loss d strength at Wir<br />

thawing, n<strong>on</strong>-uniform thermal settlements and thermkarst<br />

manifestati<strong>on</strong>s. B-ides, vdley slopes may c<strong>on</strong>tain the<br />

beds of weak argillaceous rock or there may be slideinduced<br />

displacements suspended by permafrost. It is<br />

quite natural, therefor%. to foresee the loss of local or<br />

general stability of the slopes or activati<strong>on</strong> of slides at<br />

the change of thermodynamc c<strong>on</strong>diti<strong>on</strong>s. This possibility<br />

is duly allowed for 'by the specialists implementing innovative<br />

designs which ensure the stability of slopes and<br />

reduce seepage losses. Mawry hydraulic structures ore<br />

designed to be built <strong>on</strong> loose frozen formati<strong>on</strong>s different<br />

from <strong>on</strong>e another not <strong>on</strong>ly by the c<strong>on</strong>situent rocks but,<br />

what is more important, by the cryogenic structwe and<br />

properties. If this is the case, the frozen-type hydraulic<br />

structure is adopted. This type of struchre is c<strong>on</strong>sidered<br />

to be the best from the safety and envir<strong>on</strong>mental points<br />

of view, though if the fouh&ti<strong>on</strong> is formed by the thick<br />

strata of clastic rocks their thawing is unavoidable and,<br />

therefore, the foundati<strong>on</strong> treatment procedure must be<br />

based <strong>on</strong> the detailed c<strong>on</strong>siderati<strong>on</strong> for the rock behaviour<br />

in the process of thawing. All this c<strong>on</strong>diti<strong>on</strong>s the selecti<strong>on</strong><br />

of the damsite, layout and design of the structure5<br />

and the relevant c<strong>on</strong>structi<strong>on</strong> techniques.<br />

Experience gained in crmting designs<br />

houses, spilhvays and other structures,<br />

of dpms, power<br />

both being elabo-<br />

rated and already realized, enables the lay-out problems<br />

to be solved for practically all climatic, topographic and<br />

geological c<strong>on</strong>diti<strong>on</strong>s.<br />

In so doing, the lay-out soluti<strong>on</strong>s adopted are meant not<br />

<strong>on</strong>ly to make for smooth operati<strong>on</strong> of str~tures built <strong>on</strong><br />

heterogeneous thawed-froza foundati<strong>on</strong>s with timdependent<br />

properties but to do as little harm as possible to the<br />

easily injured northern nature. Tk heaviest and most<br />

heat-releasing structures are advisable to be c<strong>on</strong>structed<br />

either in the talik z<strong>on</strong>es or <strong>on</strong> the frozen rocks undisturbed<br />

by upheaval. In this case speck1 attenti<strong>on</strong><br />

should be paid to the treatment of foundati<strong>on</strong>s, especially<br />

if the latter are formed mostly by argillaceous rocks<br />

This is important since at the year-round c<strong>on</strong>strudi<strong>on</strong><br />

the large number of operati<strong>on</strong>s is performed at subzero<br />

air temperatures which results in freezing of thawed<br />

rocks and hence in the change of their c<strong>on</strong>dti<strong>on</strong>s and<br />

properties. To c<strong>on</strong>trol this process is <strong>on</strong>e of the most<br />

vital tasks which need to be substrpntiated by comprehmsive<br />

scientific studies prior to c<strong>on</strong>structi<strong>on</strong>.<br />

Also of primary importance in the hydraulic engineering<br />

of the Extreme North is the elaborati<strong>on</strong> of new sientificd.ly<br />

sod mnstructi<strong>on</strong> schemes. Numerous investigati<strong>on</strong>s<br />

in this field, including those performed with participati<strong>on</strong><br />

and under guidance of the authors, have dem<strong>on</strong>strated<br />

that as far as water retaining atrudures are c<strong>on</strong>cmed<br />

<strong>on</strong>e of WE most pr<strong>on</strong>lisirg diredi<strong>on</strong>s is the applicati<strong>on</strong> of<br />

c<strong>on</strong>structi<strong>on</strong> schemes permitting of easy c<strong>on</strong>trol of heat<br />

exchange processes. C<strong>on</strong>strwti<strong>on</strong> of dam shells kng<br />

rockfill does not involve any .difficulties. Its excawti<strong>on</strong>,<br />

transportati<strong>on</strong> and placemnt in ungraded wnciti<strong>on</strong>s are<br />

d<strong>on</strong>e in the same mannw as outside t l North- ~ Climtic<br />

Z<strong>on</strong>e. Rockfill can be placed in the shells in hi& lifts<br />

or in layers with subsequent compacti<strong>on</strong>. When using nurainic<br />

soils which have nearly optimum compositi<strong>on</strong> the<br />

dams mn be c<strong>on</strong>structed either by dry methods or by<br />

dumping tl-E soil into mter. 'Ihe6e techriqueg were repeatedly<br />

tested in practice and proved to be good from the<br />

design and c<strong>on</strong>structi<strong>on</strong> point2 of viav.<br />

AQrisable to be c<strong>on</strong>structed in the North ore embankment<br />

dams built from soil and mimi ( soil and n<strong>on</strong>-soil) materials<br />

with sklls made of ungraded st<strong>on</strong>e and impervious<br />

elements made of local soil materials or realizd in the<br />

form of steel diaphraglllS, steel membranes, asphaltic ad<br />

precast c<strong>on</strong>crete diaphragn& Ala remmnlended are em<br />

bankment dams Imving impewious elements in the furrrl<br />

of ice-soil \\ails and "frozcn ct1rtains" created snd inairr<br />

1268

tained Ivith the aid of air, fluid and steam-and-fluid setups.<br />

In tile latter case the design of the c<strong>on</strong>tact z<strong>on</strong>e<br />

behveen an impervious element and a thawed-frozen foundati<strong>on</strong><br />

liable to n<strong>on</strong>-uniform defornlati<strong>on</strong>s needs special<br />

c<strong>on</strong>siderati<strong>on</strong>.<br />

As is !vel1 known, erlibanlcment dam foundati<strong>on</strong> settlements<br />

and self-compacti<strong>on</strong> of soil in the c<strong>on</strong>structi<strong>on</strong> and postc<strong>on</strong>structi<strong>on</strong><br />

periods sllall not cause hazardous deformati<strong>on</strong>s<br />

of ilnpervious elements, drains, transiti<strong>on</strong> z<strong>on</strong>es and<br />

rigid members of other structures linked to the daw body.<br />

Neither c<strong>on</strong>centrated seepage paths nor dangerous piping<br />

z<strong>on</strong>es shall appear in the dam.<br />

Proceeding from the above c<strong>on</strong>siderati<strong>on</strong>s tha "Code for<br />

designing embankment dams in the Northern Climatic<br />

Z<strong>on</strong>e" recommends the design density of soil to be adopted<br />

so that the design settlements of different parts of<br />

the dam would be close to each other by absolute value,<br />

lvhereas relative settlements of the crest in the operati<strong>on</strong><br />

period Iuould not exceed 2-2.5% of the dam height at a<br />

given cross-secti<strong>on</strong>. The above recommendati<strong>on</strong> pertains<br />

to the embankment dams to be c<strong>on</strong>structed from soil materials<br />

<strong>on</strong>ly.<br />

Experience shows that in the c<strong>on</strong>structi<strong>on</strong> of thawed-type<br />

embankment dam it is not feasible to build a core or<br />

membrane entirely of thawed soils; the <strong>on</strong>ly possible design<br />

is s pie-like structure formed by interstratified z<strong>on</strong>es<br />

of thawed, frozen and cooled below O°C saline soils.<br />

That is why to meet the requiremants <strong>on</strong> permissible sewements<br />

it is necessary to regulate temperature canditi<strong>on</strong>s<br />

of impervious elements and determine, with or without the<br />

allowance made for salinity, the ultimate temperature c<strong>on</strong>diti<strong>on</strong>s<br />

at which the settlement rates and values are well<br />

within the allowable limits both in the c<strong>on</strong>structi<strong>on</strong> and.<br />

post-c<strong>on</strong>structi<strong>on</strong> periods, Ivliulti-purpose studies <strong>on</strong> the<br />

method of c<strong>on</strong>shcti<strong>on</strong> of the Kolymskaya temporary and<br />

stati<strong>on</strong>ary dams have made it possible to refine the requirements<br />

<strong>on</strong> soil materials and techniques of, their placement<br />

in the dam body. The c<strong>on</strong>structi<strong>on</strong> procedure modifled<br />

accordingly enabled optimum temperature c<strong>on</strong>diti<strong>on</strong>s to<br />

be maintained so that the core could be kept in thawed<br />

c<strong>on</strong>diti<strong>on</strong> a5 early a5 at the c<strong>on</strong>structi<strong>on</strong> stage. This, in<br />

turn, resulted in uniform deformati<strong>on</strong>s at the c<strong>on</strong>solidati<strong>on</strong><br />

of all parts of the structure thereby ensuring its safe<br />

thermal stress-strain state. L<strong>on</strong>g-term investigati<strong>on</strong>s of<br />

the temperature c<strong>on</strong>diti<strong>on</strong> chnges and ice formati<strong>on</strong> in<br />

rockfill shells of the Kolymskaya, Vilyiskaya and Khantaiskaya<br />

dams permitted of assessing the effect of these<br />

processes 011 the thermal stress-strain state of the dam<br />

and c<strong>on</strong>trolling them by placing surface soil layers of<br />

predetermined grain-size compositi<strong>on</strong> and thickness.<br />

LDamy soil5 <strong>on</strong> the major part of the USSR North-East<br />

are known for high ice and silt c<strong>on</strong>tents, which determiw<br />

es the scarcity of soil material suitable for c<strong>on</strong>structing<br />

impervlous elements. It looks promising, therefore, to make<br />

the latter from n<strong>on</strong>-soil materials, e*g. from steel. In particular,<br />

impervious diaphragms can be made from steel<br />

plates or l o w carb<strong>on</strong> steel piles of more than 10-12 mm<br />

thickness. Given an anticorrosive ymil, epoxy, bitumen<br />

or asphaltic coating such elements may last 200 years,<br />

To provide for joint deformati<strong>on</strong> of the diaphragm and the<br />

shells it is most reas<strong>on</strong>able to ensure its free c<strong>on</strong>tact<br />

with the sides through the medium of bitumen keys,<br />

The dams with steel membranes may be recommended at<br />

high heads. Their advantage resides in the shell being<br />

dry to the downstream water level. This increases the<br />

shell seismic stability, whereas the membrane attains<br />

greater freedom of deformati<strong>on</strong>s collaborating with the<br />

shell, which c<strong>on</strong>tributes to the safety and relaxes the requirements<br />

<strong>on</strong> material placement. c<strong>on</strong>structi<strong>on</strong> of dams<br />

with steel seepage c<strong>on</strong>trol elements is best suited to the<br />

c<strong>on</strong>diti<strong>on</strong>s of the North.<br />

When designing the Adychanskaya power plant to be c<strong>on</strong>struded<br />

under extremely Severe c<strong>on</strong>diti<strong>on</strong>s, am<strong>on</strong>g other<br />

versi<strong>on</strong>s the dams with steel diaphragms have been suggested.<br />

In this case, due to severity of climate, the steel<br />

structwes are proposed to be bolt-c<strong>on</strong>nected. Owing to<br />

excepti<strong>on</strong>al transportati<strong>on</strong> difficulties the volumes of outside<br />

materials have to be cut short. C<strong>on</strong>sequenELy, a precast<br />

c<strong>on</strong>crete diaphragm has been suggested. The diaphragm<br />

parts (5-7 kg plates) can be made of c<strong>on</strong>crete<br />

protected with heat-and-darrpproof mats, of impre~ted<br />

c<strong>on</strong>crete ad lightweight c<strong>on</strong>crete. The design of joints<br />

sealed with cold-resistant materials permits of some dP<br />

formati<strong>on</strong>. At small heads such dams turn out to be preferable<br />

to all other kinds of "dam of the North".<br />

The versi<strong>on</strong> with an asphaltic c<strong>on</strong>crete diaphragm c<strong>on</strong>si&<br />

ered in several design projects of northern dam, is being<br />

realized at the Boguchanskaya dam c<strong>on</strong>structicn. It<br />

features the following special merits: an msy-to-realize<br />

design admitting of complex rnechaniati<strong>on</strong> with the use<br />

of standard road-building equipen6 smal quantities of<br />

outside materials ( bitumen up to 8%), high waterproofness<br />

and deiormability of we material wen at marked<br />

settlements of the dam body( resting <strong>on</strong> thawing ice-rich<br />

foundati<strong>on</strong>) and- at seisnic effects.<br />

The extreme severity of Magadan district known for occurrence<br />

of thick strata of permafrost rocks .calls for maximum<br />

adaptability of a heat-accumulating power structure<br />

to the existing natural complex.<br />

Of much practical and theoretical interest in the c<strong>on</strong>structi<strong>on</strong><br />

of natural and artificial ice-soil impewious elements<br />

(by forced or gravity water delivery) is the ascertainment<br />

of relati<strong>on</strong>ship between temperature c<strong>on</strong>diti<strong>on</strong>s of the<br />

rocks, seepage rate and self-l-ealing of cracks and pores<br />

with ice (Le freezing up of, the seepage paths) . The<br />

Latter procss is seemngly governed by the cbaracter and<br />

degree of cracking, porosity, ice cuntent and ice ladeness<br />

of the rocks as well as by the rigidity of ternperawe<br />

c<strong>on</strong>diti<strong>on</strong>s.<br />

Soils are maintained in frozen c<strong>on</strong>diti<strong>on</strong> by natural cold<br />

or by artificial cooling with air, fluid and steamand-fluid<br />

set-ups used to create "frozen Mns" in the dad body<br />

and part of the foundati<strong>on</strong>.<br />

There also exists a theoretically substantiated procedwe<br />

for c<strong>on</strong>structing impervious elements by dumping frozen<br />

soils in cold water or phcing them in dry c<strong>on</strong>diti<strong>on</strong> and<br />

then pouring with water. It has been found that c<strong>on</strong>solidati<strong>on</strong><br />

of such soils proceeds better than that of thawed<br />

soils and their further freezing is easier. The new tedniques<br />

have been tested in practice and look very promising<br />

for power c<strong>on</strong>structi<strong>on</strong> in the Soviet No&-East.<br />

In view of extremely irregular northern river discharges<br />

of great c<strong>on</strong>cern are the problem of their passing espe<br />

cially in the c<strong>on</strong>structi<strong>on</strong> periods. These problem need<br />

further studies The radically new design soluti<strong>on</strong>s being<br />

susested are not yet approved for practical uses and<br />

hence require amprehensive mechanical and hydraulic<br />

investi@ti<strong>on</strong>s to optimiz the designs of hydroele&ic<br />

plant water c<strong>on</strong>veyance structures. Almost all maju- types<br />

of c<strong>on</strong>crete danq with exoepticn of arch and mdti-ard7<br />

<strong>on</strong>es, have been realized in the LSSR regi<strong>on</strong>s chracterized<br />

by severe climatic c<strong>on</strong>diti<strong>on</strong>s.<br />

Experience gained in design, corlstructi<strong>on</strong> and operati<strong>on</strong><br />

of c<strong>on</strong>crete dams located in these regi<strong>on</strong>s shows that<br />

:their stresses, strength and durability depend greatly <strong>on</strong><br />

terrperatu-e effects. All other things being equal, it leads<br />

1269

to a somewhat greater volume of c<strong>on</strong>crete in such dams<br />

as compared to those c<strong>on</strong>structed in mild clirrlntic c<strong>on</strong>diti<strong>on</strong>s.<br />

As far as c<strong>on</strong>crete volume is c<strong>on</strong>cerned, the main types<br />

of c<strong>on</strong>crete dams <strong>on</strong> rock foundati<strong>on</strong>s built in the<br />

USSR are quite comparable with the best specimens Of<br />

foreign dams realized under more favourable c<strong>on</strong>diti<strong>on</strong>s.<br />

It can be positively stated that for mass c<strong>on</strong>crete c<strong>on</strong>venti<strong>on</strong>al<br />

gr vity dams the c<strong>on</strong>crete c<strong>on</strong>sumpti<strong>on</strong> of<br />

0.76-0.77 m 3 per t<strong>on</strong> (force) of hydrostatic pressure is<br />

a limiting value from the strength c<strong>on</strong>siderati<strong>on</strong>s. This<br />

value can be reduced <strong>on</strong>ly if the dam design envisages<br />

an upstream face membrane, preliminary compressi<strong>on</strong> of<br />

c<strong>on</strong>crete, arrangement of widened intercolumnar joints or<br />

large l<strong>on</strong>gitudinal recesses, etc.<br />

The specific c<strong>on</strong>sumpti<strong>on</strong> of c<strong>on</strong>crete at the Zeyskaya<br />

mass c<strong>on</strong>crete buttress dam practically equals Wmi at the<br />

Ust-Ilimskaya mass c<strong>on</strong>crete gravity dam but is well<br />

over the specific c<strong>on</strong>swpti<strong>on</strong> at the Ihipu dam being<br />

c<strong>on</strong>structed in Brazil-Paraguay. It is likely that the c<strong>on</strong>structi<strong>on</strong><br />

of a mass c<strong>on</strong>crete buttress diim under rigorous<br />

climatic c<strong>on</strong>diti<strong>on</strong>s can be cost-effective if it results<br />

in 15-20% reducti<strong>on</strong> of the material c<strong>on</strong>sumpti<strong>on</strong><br />

capacity as compared to a mass c<strong>on</strong>crete gravity dam<br />

(to compensate for the higher unit job price of c<strong>on</strong>creting<br />

which rises due to the increase of c<strong>on</strong>crete c<strong>on</strong>sumpti<strong>on</strong><br />

at the deepened parti<strong>on</strong>s) . For cost-effective<br />

mass c<strong>on</strong>crete buttress dams the yecific c<strong>on</strong>sumpti<strong>on</strong><br />

of c<strong>on</strong>crete should be 0.60-0.65 m per t<strong>on</strong> ( force) Of<br />

hydrostatic pressure.<br />

The designs are elaborated of highly reliable and durable<br />

impervious membranes and complex therrmhydroinsulating<br />

facings of asphaltic lightweight c<strong>on</strong>crete, foam plastics<br />

and foam asphalt with reinforced c<strong>on</strong>crete and glass-reinforced<br />

plastic enclosure. Also elaborated are the designs<br />

of deformati<strong>on</strong> joint sealings and methods for design<br />

calculati<strong>on</strong> of plastic thermohydminsubting facings.<br />

A 200 m2 experimental strip of such facing ‘has been<br />

c<strong>on</strong>structed and tested for 3 years at the Andizhanskaya<br />

dam. The tests have dem<strong>on</strong>strated that in plastic lightweight<br />

asphaltic c<strong>on</strong>crete wen 2-3 mm cracks and joints<br />

undergo self-healing thus restoring waterproofness. of the<br />

facing. The tests of ehnkment facings <strong>on</strong> the Barents<br />

Sea and Sea of Okhotsk and thermohydroinsulating facings<br />

at the Vilujskaya dam c<strong>on</strong>ducted for 10 years have<br />

c<strong>on</strong>firmed high reliability of thermahydroinsulati<strong>on</strong> and its<br />

protective enclosure.<br />

C<strong>on</strong>structi<strong>on</strong> Of hydraulic structwes in cold clirrate is a<br />

complicated task which cab for innovative organiati<strong>on</strong>ak<br />

technological and design soluti<strong>on</strong>s.<br />

The relative steel c<strong>on</strong>sumpti<strong>on</strong> at the existing”native<br />

dams and at the Sayano-Shushenskaya arch-gravity<br />

Qm which is under c<strong>on</strong>structi<strong>on</strong> is, <strong>on</strong> the average,<br />

around 10 kg/m.<br />

Am<strong>on</strong>g most promising dams planned to be c<strong>on</strong>structed<br />

<strong>on</strong> good rivers of Siberia and Soviet Far East, providing<br />

the engineering-geological c<strong>on</strong>diti<strong>on</strong>s are favourable,<br />

is a gravity dam of composite profile ,built of compact<br />

c<strong>on</strong>crete or heat-insulated polymer c<strong>on</strong>crete with the<br />

crest and core made of stiff lean c<strong>on</strong>crete. The compact<br />

or polymer c<strong>on</strong>cretes ensure waterpmohess of the<br />

dam and protect it from seas<strong>on</strong> variati<strong>on</strong>s of the ambient<br />

air temperature. Besides, they form the main ( seepage-c<strong>on</strong>trol)<br />

element. of the structure.<br />

One of the problems encountered at the c<strong>on</strong>structi<strong>on</strong><br />

of c<strong>on</strong>crete dams in severe climatic c<strong>on</strong>diti<strong>on</strong>s is the<br />

performance of grouting operati<strong>on</strong>s to provide grout curtains<br />

in the foundati<strong>on</strong> and to seal the joints.<br />

So far the elaborati<strong>on</strong> of joint grouting techniques at<br />

subzero temperatures ampunted to We selecti<strong>on</strong> of special<br />

cold-resistant grouts and different vlays of warming<br />

the joints. Grouting of c<strong>on</strong>structi<strong>on</strong> joints preceeded by<br />

hydrodefrosting is c<strong>on</strong>sidered to be promising. This method<br />

has been tested at the Zeyskaya and Sayano-Shushenshya<br />

dams and, according to the imrestiigati<strong>on</strong> results,<br />

proved to be rather simple and inexpensive.<br />

In the c<strong>on</strong>structi<strong>on</strong> OC dams <strong>on</strong> soils susceptible to settling<br />

under thermal effects, where th,e foundati<strong>on</strong> should<br />

be kept frozen, P frozen-up dam with cooling system ensuring<br />

its integrity is required. Arrangemmt of thermoinsulating<br />

curtains cutting off frozen c<strong>on</strong>crete dams from<br />

reservoirs presents some difficulties. In this case thermohydroinsuhting<br />

hcings of and impewious membranes<br />

in the c<strong>on</strong>crete dams and other reinforced c<strong>on</strong>crete<br />

structures appear to be rather effective. The dams so<br />

protected can be built of low-cement c<strong>on</strong>crete with reked<br />

requirements <strong>on</strong> wterproohess, frost and crack<br />

resistance.<br />

1270

STUDY OF SOME GEOTECHNICAL ASPECTS EFFECTING<br />

CONSTRUCTION IN GLACIAL REGIONS OF HIMALAYAS<br />

D.S. Lalji and R.C. Pathak<br />

Dte of Engg (Def R&D Ow), Kashmir House, New Delhi, India<br />

SYNOPSIS The higher morphogenic tracts of lofty snow bound Himalayas possess the largest<br />

glacier resources in the world, outside the Polar regi<strong>on</strong>s. Besides the perennial ice cover,<br />

vast reaches of Himalayas come under periglacial envir<strong>on</strong>ment. Due to unique orographical<br />

features of the Himalayas, the' lithotecbnic z<strong>on</strong>es like Pir Panjal, Great Himalayas and Trans<br />

Himalaya ranges receive maximum snow precipitati<strong>on</strong> whereas Zanskar and Ladakh ranges almost<br />

receive no snow-fall. In the Western Himalayas, the snow fall pattern is primarily governed<br />

by Western Disturbances. In the present paper terrain evaluati<strong>on</strong>, pavement and foundati<strong>on</strong><br />

c<strong>on</strong>structi<strong>on</strong> problems of the permafrost and periglacial regi<strong>on</strong>s have been attempted. Icing<br />

phenomen<strong>on</strong>, de-icing techniques and the freeze-thaw cycles haw been highlighted. The salient;<br />

geomorphological and aeotechnical expressi<strong>on</strong>s have been studied ,with a veiw especially to<br />

analyse coli regi<strong>on</strong> c<strong>on</strong>structi<strong>on</strong> problems.<br />

fNTRODUCTION<br />

The remote high-altitude areas of North<br />

Western tracts of most enchanting Himalayas<br />

inherit some of the largest glacier<br />

and permafrost resources in the world.<br />

The unique orography and the litho-tect<strong>on</strong>ic<br />

structure of the lofty . regi<strong>on</strong>s<br />

of Himalayas exposes a varied and vivid<br />

type of geotechnical studies under varying<br />

seas<strong>on</strong>al envir<strong>on</strong>ment. Besides the perennial<br />

ice cover, vast reaches of Himalayas<br />

come under periglacial snow cover. Notwithstanding<br />

with the fact that human<br />

spatial pattern, flora and fauna is sparse<br />

in the extreme- ly cold regi<strong>on</strong>s, the<br />

bare essential need of communicati<strong>on</strong>s<br />

means like tracks, pavements, shelters<br />

etc. poses a gigantic task especially<br />

under adverse climatic c<strong>on</strong>diti<strong>on</strong>s. The<br />

problems arc further aggra- -vated by<br />

the presence of numerous devastating<br />

and active snow-ice avalanches.<br />

In the present study the various geomorpholo-<br />

gical and geotechnical expressi<strong>on</strong>s<br />

have been looked into with a view to<br />

analyse the identified cold regi<strong>on</strong> problems<br />

and offer some viable soluti<strong>on</strong>s<br />

to keep up the normal functi<strong>on</strong>al aspects<br />

of the populace. The terrain evaluati<strong>on</strong><br />

of the regi<strong>on</strong>, the de-icing techniques<br />

and foundati<strong>on</strong> parameters of the<br />

periglacial and permafrost regi<strong>on</strong>s have<br />

been highlighted. The c<strong>on</strong>structi<strong>on</strong> techniques<br />

of pavements and suitable type<br />

of habitats al<strong>on</strong>gwith essential supportlng<br />

services are discussed and suitably presented<br />

in the paper after thorough ground<br />

checks and physical<br />

rec<strong>on</strong>nainances<br />

with the helps of large scale topographical<br />

survey maps.<br />

REVIEW OF .LITERATURE<br />

The inaccessible, unapproachable and<br />

hostile terrain of the Himalayas poses<br />

challenging tasks in carrying out geotechnicalstudies<br />

and maintaining communicati<strong>on</strong>s.<br />

However, unde-terred by the cold<br />

climatic haiards, Indian Scientists' and<br />

gebtechnical engineers have accepted<br />

the challenges and have made commendable<br />

progress and tackled permafrost engineering<br />

problems with success. The mehrological<br />

and envir<strong>on</strong>mental effects save<br />

been studied in detail by the weather<br />

scientists (Pradhan et.a1.,1977).<br />

The effect of vege- tati<strong>on</strong> and slope<br />

stability aspect of peri- glacial regi<strong>on</strong>s<br />

of Western Himalayas have been analysed<br />

(Pathsk71987)Pathak et.al, 1987). The<br />

snow and ice technology of snow bound<br />

regi<strong>on</strong>s have been amply studied by the<br />

author ( Lalji D'.Singh et.a1.,1977).<br />

Deicing and anti-icing problems of the<br />

roads and pavements have been attempted<br />

since early seventies by the scientists<br />

of Snow & Avalanche Study Establishment<br />

(SASE) and engineers of Border Roads<br />

Organi- sati<strong>on</strong> (BRO) ,The various techniques<br />

of de-icing prahtlced by the above<br />

organisat-, i<strong>on</strong>s have been presented (Annua1<br />

SASE Report 1974-75, 1980-81).<br />

Vombatkere (1985) has studied the l<strong>on</strong>g<br />

term behaviour of glacial ice and also<br />

has organised for c<strong>on</strong>structi<strong>on</strong> of a bailey<br />

bridge at the altitude of 5580 m (1986).<br />

Freeze-thaw cycle ( Pathak et.al. 1987)<br />

and frost-heaving has been studied for<br />

pavement c<strong>on</strong>structi<strong>on</strong> etc. In somewhat<br />

similar scenar'io Dayal( 1985) has reported<br />

a frost acti<strong>on</strong> study for trasmissi<strong>on</strong><br />

line routes between Labrador and Newfound-<br />

1271

Land, Canada. Also, terrain evaluati<strong>on</strong><br />

and geotech- nical appreciati<strong>on</strong> has been<br />

accounted for by the above author for<br />

the same regi<strong>on</strong> (Dayal, 1980).<br />

One of the main reas<strong>on</strong>s For instability<br />

in glacial soils seems to be the loss<br />

of buttressing support by the ice, coupled<br />

with excessively high regimes of ground<br />

water. Another potentially unstable<br />

situati<strong>on</strong> is the <strong>on</strong>e often associated<br />

with soliflucti<strong>on</strong> sheets or lobes widely<br />

encountered in periglacially modified<br />

terrains (Eyles, 1983). The shelters<br />

made of corrugated gulvanised ir<strong>on</strong> sheets,<br />

c<strong>on</strong>tainerised versi<strong>on</strong>, <strong>on</strong> ground or <strong>on</strong><br />

sledges 9 have been time tested. The<br />

habitats have been even tried in Antarctic<br />

regi<strong>on</strong>s and are found very useful. under<br />

the severe climatic hazards. The authors<br />

even recommend the above shelters for<br />

other permafrost regi<strong>on</strong>s of the world.<br />

has been depicted at Fia. 2, the base of<br />

which is around 4200 m. Outside the permafrost<br />

regi<strong>on</strong>s fall the periglacial areas<br />

which also poses the similar problems of<br />

extreme cold effects. A good knowledge<br />

of terrain characteristics eventually<br />

determines the evoluti<strong>on</strong> and geotechnical<br />

aspects of periglacial landform.<br />

TERRAIN EVALUATION AND CLIMATOLOGY<br />

The Himalayas display fantastic variati<strong>on</strong>s<br />

of geology, geomorphology, climate and<br />

vegetati<strong>on</strong>. The lithotect<strong>on</strong>ic z<strong>on</strong>es of<br />

Western Himalayas exhibit unique orographical<br />

features. The Southern aide of<br />

the Himalaya is humid with luxuriant flora<br />

whereas the Northern side is arid, barren<br />

and wears a look of desert. The Pir Panjal,<br />

Great Himalaya and Trans Himalaya<br />

ranges receive more snow precipitati<strong>on</strong><br />

whereas Zanskar' and Ladakh ranges are<br />

almost bare coming under low pressure<br />

belt of Western disturb- ances mainly<br />

reap<strong>on</strong>sible for snow pracipi- tati<strong>on</strong>.<br />

The glacial regi<strong>on</strong> is generally above<br />

the snow line around 4500111. The study<br />

area which is situated in the Northern<br />

part of . Jammu & Kashmir (J&K) is shown<br />

'in Fig. 1. A typical permafrost glacier regi<strong>on</strong><br />

In the winter and most part of the year<br />

the water bodies in these regi<strong>on</strong>s are frozen.<br />

Only during summer, snow and ice melts<br />

and high flood level is recorded in the<br />

valley rivers. The safe tracks and roads<br />

have been c<strong>on</strong>structed generally . al<strong>on</strong>g<br />

the river and foothills of the valley mountains.<br />

The path is sometime encountering<br />

snow and ice avalanches and passes at a<br />

height of 5600 m. The glaciated regi<strong>on</strong><br />

experiences artic type climate which is<br />

primarily governed by the orography.<br />

The orographical features could also be<br />

obsevered in FiR-1. De-icing and snow<br />

clearance is very often required in the<br />

area.<br />

Fig. 1<br />

Lithotect<strong>on</strong>ic Z<strong>on</strong>es of Himalaya<br />

DE-ICING<br />

Good amount of work all over the world<br />

has been d<strong>on</strong>e for de-icing operati<strong>on</strong>s by<br />

adding chemicals to c<strong>on</strong>trol ice and snow<br />

c<strong>on</strong>diti<strong>on</strong>s. Anti-icing techniques, using<br />

uncrushed rock salt, coal dust and use<br />

of abrasive material is also prevalent.<br />

Imminent am<strong>on</strong>g them are the several investigate<br />

and agencies ( Allied chemical, 1958F<br />

Brohm and Edwards,l960~Schneider, 1960).<br />

Most comm<strong>on</strong>ly used chemicals are sodium<br />

chloride and calcium chloride. ' In the<br />

present scenario authors have used urea<br />

also in additi<strong>on</strong> to the above two salts<br />

in early seventies for de-icing purposes.<br />

Primarily using chemicals the eutectic<br />

compositi<strong>on</strong> i.e. c<strong>on</strong>centrati<strong>on</strong> of the soluti<strong>on</strong><br />

that posses5 the lowest freezing point,<br />

is important. The eutectic temperature<br />

i.e. temperature at the eutectic point<br />

is of relevance. Calcium chloride water<br />

system remains liquid at temperatures as<br />

low as -5I0C, which is <strong>on</strong>ly -21OC in case<br />

of sodium chloride. A comparative chart<br />

1272

of sodium chloride, calcium chloride and<br />

urea are drawn at FiR. 3(a). Fig 3(b) represents<br />

the melt rate comparis<strong>on</strong> between<br />

coaldust with soil as anti-icing measures.<br />

It was observed that melt rate of sodium<br />

chloride is more than the calcium chloride<br />

and 60% melting is achieved within 90 minutes<br />

time interval. Though initial. melt<br />

rate of calcium chloride is faster because of<br />

!Iw<br />

W<br />

I<br />

ratez<br />

Y<br />

- Fb Cl<br />

"". c1 Clr<br />

--+ UREA<br />

0 20 10 60 w3 100<br />

TIME -<br />

Fig. 3 (a) Melt Rate of Ice Using Chemicals<br />

30000<br />

i<br />

g 2 0000<br />

Q-""<br />

Fig. 3 (b)<br />

TIME +<br />

Melt Rate with Coal Dust And Soil<br />

itsexo-thermic reacti<strong>on</strong>, imparting additi<strong>on</strong>al<br />

heat energy. For achieving similar results,<br />

almost double spread rate of urea has to<br />

be used. In Fig, 4, a vehicle loaded with<br />

c<strong>on</strong>tainer is shown passing through after<br />

deicing operati<strong>on</strong>.<br />

In Fig 5, a J<strong>on</strong>ga vehicle is approaching<br />

the bridge c<strong>on</strong>structed at the height of<br />

5580m <strong>on</strong> the glacier. Deicing trials with<br />

sodium chloride using salt spreader was<br />

compared with the mannual spreading rate<br />

at the critical stretches in J&K under<br />

minimum temperature c<strong>on</strong>diti<strong>on</strong> of - 1 7 O C .<br />

Use of coal dust and abrasives is effective<br />

when adequate heat is received from solar<br />

Fig. 5 A J<strong>on</strong>ga Crossing Bridge at ht of 55<br />

effective in c<strong>on</strong>trolling the ice formati<strong>on</strong><br />

al<strong>on</strong>g the side drains<br />

of culverts. (Refer Fig,<br />

and<br />

6)<br />

in the moui-th<br />

CONSTRUCTION OF PAVEMENTS<br />

Tracks and roads are the most vital arteries<br />

of an efficient communicati<strong>on</strong> system. Frost<br />

susceptability of the perma- frost regi<strong>on</strong>s,<br />

subgrade soil c<strong>on</strong>diti<strong>on</strong> and freeze-thaw<br />

'cycle pheno-men<strong>on</strong> of the periglacial envir<strong>on</strong>ment<br />

plays a very significant role for design<br />

and c<strong>on</strong>structi<strong>on</strong> of the pavment. As is<br />

generally observed in the mountainous tract<br />

the roads/tracks passes through saddles/peaks<br />

of at places but normally it is al<strong>on</strong>g the<br />

foothills or near the bed of ,the valley.<br />

Some of the salient factors viz, periglacial<br />

solifluxi<strong>on</strong>, frost susceptability, freezing<br />

and new line OC approach adopted in Indian c<strong>on</strong>diti<strong>on</strong>s<br />

of western Himalayan Regi<strong>on</strong>.<br />

1273

~~<br />

ROLD -+<br />

Apart from the icing methods cited before<br />

by<br />

bhemical means, the following practical approach<br />

has been resorted to for most of the length of road<br />

stretch in the Shyok-Nubra valley and Ladakh (J&K). regi<strong>on</strong><br />

i) Realignment of the route has been d<strong>on</strong>e to avoid<br />

icing formati<strong>on</strong>.<br />

ii),The surfacial small channels have been diverted<br />

away from the road towards valley side.<br />

iii) Wherever possible culverts/bridges have been<br />

c<strong>on</strong>structed to avoid small channels/river-icing<br />

features.<br />

iv) At some places earth-boulder embanlanents<br />

ah0 have been used to avoid ground icing<br />

phenomen<strong>on</strong>.<br />

v) On the main valley glacier, <strong>on</strong>ly pedestrian<br />

tracks have been able to c<strong>on</strong>struct at the first<br />

instance due to presence of many crevasses.<br />

vi) A peculair patch of glacier t<strong>on</strong>gue, 9hl<br />

width, crosses the road at site of 553Gm<br />

altitude, which was initially tackled by<br />

imbedding boulders/glacial till <strong>on</strong> the pavement<br />

porti<strong>on</strong>. Since the boulders and other debris<br />

materials had recurrent sinking due to thermal<br />

regime,a bailey ridge was IateE<strong>on</strong>structed at<br />

this sjlteto finally over come this difficulty.<br />

(Refer Fig. 5)<br />

TABLGI<br />

Soil Classificati<strong>on</strong> for Frost Susceptability<br />

Soil - CRREL, 86-14)<br />

Locati<strong>on</strong> Type Mechanical AnaLysislCBR Valu Frost Sus-<br />

(samples) of %passing by weight bnsdsoak ceptability<br />

mm mm micr<strong>on</strong><br />

Stati<strong>on</strong> SW - SM 73.70 56.08 10.54 7 12.0 L-M (LOW to<br />

'A' S-Sand 6 12.5 edium)<br />

Fig. 6. Layout of Placing Rocksalt<br />

The road c<strong>on</strong>structi<strong>on</strong> activity of is recent origin in the<br />

study area which comprises mainly of Shyok-Nubra valley (5530m)<br />

and Indus valley Z<strong>on</strong>es, Since road 'comunicati<strong>on</strong>s<br />

are still developing in this regi<strong>on</strong>, most of part pavement<br />

is WBM type and runs through dry river bed and lower<br />

foot hill slopes. Black topped porti<strong>on</strong> in exist comparatively<br />

in habited areas. As has been observed earlier,<br />

the area experiences severe winter <strong>on</strong>slaught during 3<br />

to 4 m<strong>on</strong>ths (Nov-Pkr) . When the maximum temperature is<br />

also at subzero near the glacier area. The area is essentially<br />

experiencing glacial and periglacial climatic<br />

c<strong>on</strong>diti<strong>on</strong>s. Andersland, et.al. (19781, Phukan (1985) and<br />

Chamberlain ( 1986) have amplyanalysed the geotechnical<br />

problms of frost-heave, periglacial' aoliflucti<strong>on</strong>, frostsuszptability<br />

etc.<br />

A<br />

The mechanical analysis of frozen/unfrozen soil has<br />

been d<strong>on</strong>e in the laboratory to ascertain its susc~- frost<br />

tability and also CBR Values found out. The data thus Geotechnical C<strong>on</strong>structi<strong>on</strong> Measures<br />

obtained has been further evaluated by m<strong>on</strong>ograph suggested<br />

by Chamberlain (1986). The soil is found to be marginally<br />

Generally the road alignment is chocsen to<br />

suscptible <strong>on</strong>ly as sand percentage is mre than silt.<br />

avoid difficult stretches and water bodies. A<br />

These results are tabulated in Table-I. The frost pene- bailey bridge designed and c<strong>on</strong>structed over a<br />

trati<strong>on</strong> depth, proposed by Aldrich and Painter (1953)<br />

al<strong>on</strong>gwith freezing index is presented in Table-11. The<br />

The values of frost penetrati<strong>on</strong> observed and computed<br />

for three experimental stati<strong>on</strong>s are in reas<strong>on</strong>able agreement.<br />

The base thickness of the pavement has been determined<br />

by the method of reduced subgrade frost penetrati<strong>on</strong><br />

as suggested by Lobacz et .al. ( 1973). The active<br />

layer exists upto Im depth from top surface in the<br />

glacierized regi<strong>on</strong> of Nubra valley.<br />

1<br />

TABLE-I1<br />

Freezing Index and Frost Qenetrati<strong>on</strong> Depths<br />

-<br />

Locati<strong>on</strong> Freezing Index Depth of Frost<br />

Penetrati<strong>on</strong> (m)<br />

Computed lobserve<br />

Site A<br />

(Alt. 5600 m)<br />

500 1 .o 0.9<br />

Site B<br />

(Alt. 4300 rn)<br />

400 0.8 0.6<br />

Site C<br />

(Alt. 4500 m)<br />

300 0.7 0.5<br />

Pass o f altitude 5603m is the highest improvised<br />

bridge in the world (Vombatkere, 1985; 1986).<br />

The movement of the ice body .recorded is<br />

negligible. A typical valley road is depicted<br />

at Fig. 7 . To reduce the frost acti<strong>on</strong>, the follow<br />

in$ measures have been taken :<br />

i) Clean sand or n<strong>on</strong>-frost susceptible soil<br />

(NFS) has been put to replace the susceptible<br />

soil.<br />

ii) Additi<strong>on</strong>al drainage measures have been c<strong>on</strong>si<br />

dered for unexpected wet areas which<br />

are a potential source of moisture migrati<strong>on</strong><br />

1274<br />

." -7

iii) In the valley, low cost roads <strong>on</strong> phenomen<strong>on</strong>. In permarpast regi<strong>on</strong>s, foundamorainic<br />

soil has been c<strong>on</strong>structed. ti<strong>on</strong>s are generally placed below the frost<br />

iv) To cater for loss of buttressing penetrati<strong>on</strong> depth or active layer. The major<br />

ice support, cross drainage has c<strong>on</strong>siderati<strong>on</strong> to be taken into account are<br />

<br />

been provided at places.<br />

depth of supporting soil strata structure,<br />

thermal regime of ground, level of moisture<br />

v) Due to low brittleness of glacial c<strong>on</strong>tent causing s)inkage/swelling of soil,<br />

sandy tills, slope failures are<br />

problems of ice masses and proper drainage.<br />

very less. Slopes of 2.5 to In the present c<strong>on</strong>text of rocky and coarse<br />

1 is generally suitable and Provided. sa6ndy soil ice lenses formati<strong>on</strong> is verv<br />

less ,- therefore, normal shallow foundatibi<br />

upto a depth of two-third of frost penetrati<strong>on</strong><br />

has been taken for c<strong>on</strong>structi<strong>on</strong> purposes.<br />

At Some places foundati<strong>on</strong>s have been laid<br />

by cutting ice/snow to about <strong>on</strong>e metre depth.<br />

A bottom course of wire netting, corru- gated<br />

ir<strong>on</strong> sheets and then cross members of wooden<br />

sleeper grillage has been provided to cater<br />

for even distributi<strong>on</strong> of super structure<br />

load. Leaving a hollow space underneath the<br />

superstructure and grillage foundati<strong>on</strong> minimises<br />

differential settlment and active layer<br />

acti<strong>on</strong>. A c<strong>on</strong>venti<strong>on</strong>al type of step foundati<strong>on</strong><br />

has been provided for a high altitude shelter<br />

made of corm- ga,&ed gulvanised ir<strong>on</strong> sheets<br />

with transverse and vertical steel truss<br />

members as depicted in Fig, 8. About 0.8<br />

m to 1 m deep foundati<strong>on</strong>, is c<strong>on</strong>sidered adequate<br />

to withstand the load of super structure.<br />

A bottom course of 15 to 20 cms of clean<br />

sand has been used to nullify frost heaving<br />

Durable shelters are pre-requisites for acti<strong>on</strong>. Calcium chloride is mixed in cement<br />

the cold regi<strong>on</strong>s to withstand the <strong>on</strong>slaught in suitable proporti<strong>on</strong> forproper b<strong>on</strong>dage,<br />

of wind, snow load etc. Adequate insulati<strong>on</strong> In all high altitude structures a small<br />

is desirable to keep the inside temperature entrance is made before the main module for<br />

comfortable. Good amount of research and acclimatisati<strong>on</strong> purposes. A t t h e p 1 a c e 0 f<br />

development has been d<strong>on</strong>e towards this end<br />

to achieve the desired results. In the Westdamp<br />

‘proof course level an insul- ati<strong>on</strong> clothern<br />

countries the type of shelters or habi-<br />

/material is placed and then flooring has<br />

tats used are I‘ box and cylinderical c<strong>on</strong>tainbeen<br />

c<strong>on</strong>structed, Apart from the indigenous<br />

improvisati<strong>on</strong>s,Indian Nati<strong>on</strong>al Building code<br />

ers placed<br />

above ground, partially buried<br />

or totally underground etc. In Indian scenario<br />

all these types may not besuitable due<br />

to its difficult means of communicati<strong>on</strong><br />

and envir<strong>on</strong>mental effects. In the present<br />

c<strong>on</strong>text the Indian scientists have used<br />

portable high altitude shelters and c<strong>on</strong>tainerised<br />

modules for various types of accommodati<strong>on</strong><br />

required apart from arctic tentages<br />

TK! &werir61’”s”d@iHe %@XXY u&~”,err,~ g ~ k ~ l<br />

rally prefabricated aluminium alloy, prefabricated<br />

fibre reinforced plastic or glass<br />

material (FRP or GRP), FRP sandwitched panels<br />

having insulati<strong>on</strong> and fire resistant phenolic<br />

foam have been used and found suitable.<br />

The comp<strong>on</strong>ents designed and used are light<br />

and helicopter-portable. The roof has slope<br />

of 1 5 O to 30° <strong>on</strong> either side to cater for<br />

snow loads. The total infrastructure is<br />

designed to withstand 100 to 150 kmph of<br />

wind speed. In Fig. 4, a loaded c<strong>on</strong>tainer<br />

accommodati<strong>on</strong> is shown being transported<br />

<strong>on</strong> a lorry 3 t<strong>on</strong>ner over a permafrost<br />

regi<strong>on</strong>.<br />

Foundati<strong>on</strong> of the shelters in high altitude<br />

area poses peculiar problems. Digging <strong>on</strong><br />

glacier ice is very difficult. Taking into<br />

account all such odds, the foundati<strong>on</strong> generally<br />

has been prepared <strong>on</strong> morainic till<br />

soil with small crib-piers and <strong>on</strong> timber<br />

grillage. This also is helpful in minimising<br />

differential or unequal settlement due to<br />

melt freeze or gradual glacier movement<br />

1275<br />

also has been adhered to during c<strong>on</strong>structi<strong>on</strong>s<br />

as., far as possible, Suitable drainage has<br />

been provided especially in saturated glacial<br />

till areas.<br />

Fig, 8 Temporary Shelter of ~ ~ ~ Sheets ~ u<br />

ESSENTIAL SERVICES<br />

At i~ h altit de id extr mely cold clim tic<br />

c<strong>on</strong>dliq<strong>on</strong>s, &e supportfng services Bike<br />

water supply, cooking, power generati<strong>on</strong>,<br />

sewage and human waste disposal becomes a<br />

difficult problem. Since prevailing low<br />

pressure hinders in normal cooking, tinned<br />

and semi-pre-cooked food.has been found quite<br />

useful and recommended. For water, melting<br />

of ice and snow has to be resorted in suitable<br />

ice melting e ui ments. Abluti<strong>on</strong> a d se a e<br />

poses special Feature. use of polyt%ene M S<br />

etc. for human waste disposal is quite comm<strong>on</strong>.

Some new design of incinerators are being used for<br />

sewage disposal which also acts as anti-polluti<strong>on</strong>device.<br />

In the Indian c<strong>on</strong>diti<strong>on</strong>s for heating<br />

small cabins special type of kerosene burners with<br />

exhaust pipes are in use.<br />

CONCLUSIONS<br />

The lofty mountains of Western Himalayas are replete<br />

with numerous glalcier and poses tremendous challenges<br />

for keeping open and maintaining the vital lines of<br />

communicati<strong>on</strong>s. To c<strong>on</strong>struct shelters, pavements and<br />

provide essential services for thinly populated<br />

permafrost and periglacial regi<strong>on</strong>s, is all the more a<br />

gigantic task in adverse climate c<strong>on</strong>diti<strong>on</strong>s. However,<br />

appreciating the terrain characteristics, geomorphology<br />

and geotechnical expressi<strong>on</strong>s, the following few<br />

salient c<strong>on</strong>clusi<strong>on</strong>s have been arrived :- at<br />

i) Analysis of terrain evaluati<strong>on</strong>, orography and<br />

synoptic weather system, western disturbances,<br />

help in appreciati<strong>on</strong> of precipitati<strong>on</strong> and<br />

deducti<strong>on</strong> of geotechnical param@ters.<br />

ii) Deicing by mechanical means using chemical<br />

salts has been found very effective for<br />

road ice melting. Rock salt in gunny bags is<br />

useful for c<strong>on</strong>trolling ice formati<strong>on</strong> in<br />

the side drains during early winter periods.<br />

iii) Use of clean sand or n<strong>on</strong> frost susceptible<br />

soil and proper drainage are c<strong>on</strong>sidered very<br />

suitable for minimising frost acti<strong>on</strong> and<br />

periglacial soli-fluxi<strong>on</strong>.<br />

iv) Proper leveling of glacier mor&ic soil with<br />

timber grillage or crib foundati+<strong>on</strong>s has been<br />

tried with success. Foundati<strong>on</strong>s <strong>on</strong> dug-in<br />

glacier ice with bottom course of geotextiles,<br />

corrugated galvaniaed ir<strong>on</strong> sheets and timber<br />

grillage cross members have been found functi<strong>on</strong>al.<br />

v) Precooked food, speical kerosene burners for<br />

heating and incinerator type sewage disposal<br />

techniques have been found very effective.<br />

ACKNOWLEDGEMENTS<br />

Authors are very grateful to the higher authorities<br />

of Defence <strong>Research</strong> & Development Organisati<strong>on</strong> (DRDO)<br />

and various Establishments/Instituti<strong>on</strong>s for providing<br />

all facilities to. carry out this study. Special<br />

thanks are due to Shri SS Gulati and Shri GP Nautiyal<br />

for excellent secretarial assistance.<br />

REFERENCES<br />

Aldrich, H.P. and Painter, H.M. (1953). Analytical<br />

studies of freezing and thawing of soils. Tech<br />

Report 42, ACFEL, U.S.A.<br />

Allied Chemical (1958). Calcium Chloride. Bull.<br />

No 16, Tech. and Engg. Ser. Ind. Chem. Div.<br />

Morristown, N.S.<br />

Andersland, O.B. and Anders<strong>on</strong>, D.W. (1978). Geo-.<br />

technical Engineering for Cold Regi<strong>on</strong>s. Mc+Graw<br />

Hill Book Co., New York, U.S.A.<br />

Annual Reports of SASE (1980-81), Manali, India.<br />

Brohm, D.R. and Edwards, H.R. (1960). Use of Chemicals<br />

and abrasives in Snow and Ice removal from<br />

highway Res. Board, NAS-NRC Pub., 761, Washingt<strong>on</strong> D.C.<br />

Chamberlain, J. Fdwin (1986). Evaluati<strong>on</strong> of selected<br />

Frost-susceptability Task Methods. CRREL Report<br />

86-14 (U1S.A.).<br />

of<br />

Dayal, U. (1980). Terrain Evaluati<strong>on</strong> and Eeotechnical<br />

studies for 800 miles l<strong>on</strong>g transmissi<strong>on</strong> line<br />

routes. Proc. 6th S.E.A. C<strong>on</strong>f. wn Soil Engg.<br />

Taipei, China.<br />

Dayal, U. (1985). Estimati<strong>on</strong>ofheavingandfrost<br />

forces <strong>on</strong> Transmissi<strong>on</strong> Tower Foundati<strong>on</strong>s. Indian<br />

Geotechnical C<strong>on</strong>f. (I.G.C.-85), Dec 16-18,<br />

Roorkee, India.<br />

Eyles, N. (1983). Glacial Geology, Pergam<strong>on</strong> Press<br />

Tor<strong>on</strong>to, Canada.<br />

La1 ji D. S., Sharma, S . S. and Upadhyay, D.S. ( 1977).<br />

Gap in know how <strong>on</strong> Snow and Avalanche Technology.<br />

P.P. 163-171. Int.Workshop<strong>on</strong>Ice,Snowand<br />

Avalanche, Manali, India.<br />

Lobacz, E.F., Gilman, G.D. and Htrm<strong>on</strong>; F.B. (1973).<br />

Corps of Engineers, Design of Highway pavements<br />

in Areas of seas<strong>on</strong>al frost. Proc. of Synp. <strong>on</strong><br />

Frost Acti<strong>on</strong> <strong>on</strong> Roads, Oslo, P.P. 142-152.<br />

Pathak,R.C. (1987). Geotechnicai Aspects of Snowpack<br />

stability of Himalayan Regi<strong>on</strong>. Proc.<br />

of<br />

Int. Sym. <strong>on</strong> Avalanche Formati<strong>on</strong>, Movement and<br />

Effects. IRHS, Pub. No 162. Davos, Switzerland.<br />

Pathak, R.C., Rao, A.P.R. (1987). Some Applied Geomorphological<br />

aspects of Slope stability of<br />

Himalayan Regi<strong>on</strong> - A case study. Int. Sym. <strong>on</strong><br />

Geomorphology and Envir<strong>on</strong>mental Management,<br />

Allahabad University, Allahabad, India (In Press).<br />

Phukan, Arvind (1985). Frozen Ground Engineering<br />

Prentice Hall, Inc. New Jersey (U.S.A.).<br />

Pradhan, S.K., Upadhyay, D.S. and Lidoo, P.N. ( 1977) .<br />

ClimatologyofJammuandKashmir.P.P. 19-33.<br />

Int. Workshop <strong>on</strong> Ice, Snow and Avalanche, Manali,<br />

India.<br />

Pers<strong>on</strong>al Communicati<strong>on</strong> with Col. S.S. Sharma and<br />

other scientists of Defence <strong>Research</strong> & Development<br />

Organisati<strong>on</strong> and B.R.O. (1986-87).<br />

Schneider, T.R. (1960). Eidgenossische Institut fur<br />

schnee-und Lawinenfurschung, Weissfluhjoch,<br />

Davos, Switzerland.<br />

Vombatkere, S.G. (1985). On the l<strong>on</strong>g term behaviour<br />

of glacial ice under moving traffic load - A case<br />

study.Journalofglaciology,Vol-31,no 109,<br />

P.P. 169.<br />

Vombatkere, S.G. (1986). BridgeResting<strong>on</strong>anice<br />

body at high altitude. A.S.C.E. Journal, Vol-112,<br />

No 2 June 86, U.S.A.<br />

1276

A SUBGRADE COOLING AND ENERGY RECOVERY SYSTEM<br />

E.L. L<strong>on</strong>g and E. Ysnnak Jr.<br />

Arctic Foundati<strong>on</strong>s, he., Anchorage, Alaska, USA<br />

SYNOPSIS<br />

The Kotzebue Senior Citizen's Cultural Center had experienced foundati<strong>on</strong> distress<br />

due to thaw settlement since c<strong>on</strong>structi<strong>on</strong> in the summer of 1975, The structure was originally<br />

c<strong>on</strong>structed with a c<strong>on</strong>venti<strong>on</strong>al foundati<strong>on</strong> (i.e. heated crawl space) <strong>on</strong> gravel fill over ice-rich<br />

permafrost. A mechanical refrigerati<strong>on</strong> system utilizing 20 horiz<strong>on</strong>tal copper loops was installed in<br />

1976 to circulate a cooled glycol/water mixture beneath a layer of polyurethane insulati<strong>on</strong>. Due to<br />

operati<strong>on</strong>al difficulties, this system <strong>on</strong>ly slowed the permafrost degradati<strong>on</strong> and subsequent<br />

settlement of the structure. In the summer of 1986, the mechanical system was c<strong>on</strong>verted to a<br />

two-phase thermosyph<strong>on</strong> with parallel evaporators and a comm<strong>on</strong> external c<strong>on</strong>denser using carb<strong>on</strong><br />

dioxide as the working fluid, Each of the 20 existing copper loops is utilized as an evaporator.<br />

The heat removed from the subgrade is used to preheat make-up air for the ventilati<strong>on</strong> system.<br />

Existing mechanical refrigerati<strong>on</strong> equipment was utilized to provide back-up refrigerati<strong>on</strong> capability.<br />

Without energy input, the subgrade cooling system now has the capacity to withdraw five times<br />

the heat of the mechanical system. Subsequently, the progressi<strong>on</strong> of thaw beneath the structure has<br />

been reversed.<br />

INTRODUCTION<br />

The village of Kotzebue is located in northwest<br />

Alaska at the north end of the Baldwin<br />

Peninsula between Kotzebue Sound and a<br />

substantial lago<strong>on</strong>. To the east and south of<br />

the lago<strong>on</strong>, low hills dominate the landscape of<br />

the peninsula. West of the lago<strong>on</strong>, a gravel<br />

spit exists up<strong>on</strong> which the majority of the<br />

village's development is clustered. The entire<br />

Baldwin Peninsula lies within the regi<strong>on</strong> of<br />

c<strong>on</strong>tinuous permafrost with the depth to the<br />

base of permafrost being approximately 73<br />

meters in the Kotzebue area (Brown and PiwB,<br />

1973; Ferrians, 1965).<br />

The gravel and sandy gravel deposits that form<br />

the Kotzebue Sound side of the spit are<br />

generally 9 to 12 meters in depth and are<br />

underlain by fine-grained deposits of sand,<br />

silt, clay and organics. The soils in the<br />

hills to the east and south are predominately<br />

ice-rich fine grained deposits. The transiti<strong>on</strong><br />

z<strong>on</strong>e between the coarse grained spit deposits<br />

and the fine grained ice-rich deposits is<br />

interfingered with varying quantities of all<br />

the sail types found in the area and generally<br />

is capped by a tapering strata of granular<br />

soil.<br />

Early structures in Kotzehue were small and<br />

used c<strong>on</strong>venti<strong>on</strong>al footings <strong>on</strong> the gravelly<br />

soils near the beach where they experienced few<br />

foundati<strong>on</strong> problems. As the village grew, the<br />

size of the structures increased and new<br />

c<strong>on</strong>structi<strong>on</strong> was forced east where the<br />

surficial granular deposits were thinner and<br />

frequently interhedded with fine-grained lago<strong>on</strong><br />

sediments, organics and some ice. Even <strong>on</strong> the<br />

better porti<strong>on</strong>s of the spit, as the size of the<br />

structures increased, settlement became a<br />

problem as the thaw bulbs penetrated through<br />

the granular soils into the ice-rich fine<br />

grained material.<br />

The Kotzebue Senior Citizen's Cultural Center<br />

(originally named the Kotzebue Pi<strong>on</strong>eer Home) is<br />

sited east of the main village near the<br />

transiti<strong>on</strong> z<strong>on</strong>e between the gravel and<br />

fine-grained deposits. The main porti<strong>on</strong> of the<br />

structure is a hexag<strong>on</strong> with 18 m l<strong>on</strong>g sides.<br />

Two residential wings are attached to the south<br />

and southwest sides of the hexag<strong>on</strong> and a short<br />

mechanical wing is attached <strong>on</strong> the northeast<br />

side. The single story structure is founded <strong>on</strong><br />

c<strong>on</strong>tinuous footings with c<strong>on</strong>crete stem walls<br />

approximately 1.4 m high. The crawl space<br />

beneath the floor is heated by the underfloor<br />

utilities. The original foundati<strong>on</strong> design did<br />

not provide for maintaining the permafrost<br />

beneath the structure. The structure is shown<br />

<strong>on</strong> Figure 1.<br />

In the fall of 1974, the immediate area of the<br />

building site was stripped of organics down to<br />

in situ granular soils. In the spring and<br />

early summer of 1975, the site was filled with<br />

1 to 2 m of compacted granular material to form<br />

a level building pad (Abbott, 1975). The total<br />

depth of gravel averaged 2.5 m over frozen<br />

sand, silt and organics. By August 1, 1975,<br />

when the subfloor was installed, the south and<br />

southwest wings had settled as much as 5 cm.<br />

EXPLORATION<br />

Initial explorati<strong>on</strong> of the site was c<strong>on</strong>ducted<br />

in 1973 with 23 borings over the general site<br />

area. The majority of the holes were to a<br />

depth of 4.6 m, however, three borings were<br />

1277

MECHANICAL REFRIGERATION<br />

made to depths of 12 and 17 m. Moisture<br />

c<strong>on</strong>tents of less than 30 percent were reported<br />

except for a 1-m ice lens in the southeast<br />

corner of the area at a depth of 1 to 2 m.<br />

Following the observed settlement in August<br />

1975, seven holes were put down around the<br />

structure with depths varying from 3 to 4,6 m.<br />

In January 1976, four additi<strong>on</strong>al holes were put<br />

down to approximately 15 m in depth taking<br />

c<strong>on</strong>tinuous undisturbed samples which were<br />

shipped in the frozen c<strong>on</strong>diti<strong>on</strong> to Cold Regi<strong>on</strong>s<br />

<strong>Research</strong> and Engineering Laboratory (CRREL) at<br />

Fairbanks, Alaska and Hanover, New Hampshire<br />

for analysis. The primary tests c<strong>on</strong>ducted were<br />

water c<strong>on</strong>tent, gradati<strong>on</strong> analysis, density<br />

determinati<strong>on</strong>s, and thaw c<strong>on</strong>solidati<strong>on</strong>.<br />

SETTLEMENT ANALYSIS<br />

Early settlement while the structure was under<br />

c<strong>on</strong>structi<strong>on</strong> was attributed primarily to the<br />

thawing of seas<strong>on</strong>ally frozen soils. It was<br />

also possible that c<strong>on</strong>solidati<strong>on</strong> of loose<br />

gravel fill and compressible soils not stripped<br />

from the site may have c<strong>on</strong>tributed to the<br />

problem (Abbott, 1975). The boring data<br />

obtained in January 1976 for CRREL indicated<br />

that much of the soil to a 15 m depth had<br />

moisture c<strong>on</strong>tents well in excess of 30 percent.<br />

Three of the '4 holes had strata with water<br />

c<strong>on</strong>tents well over 90 percent, while the fourth<br />

hole had strata with water c<strong>on</strong>tents in excess<br />

of 60 percent.<br />

CRREL estimated that total settlements at the<br />

boring locati<strong>on</strong>s were expected to be 10 to 20<br />

cm with thaw to 6 m, 20 to 30 cm with thaw to 9<br />

m, and 45 to 60 cm with thaw to 15 m (Crory,<br />

1976). As a result of the CRREL study, the<br />

State of Alaska Divisi<strong>on</strong> of Buildfngs elected<br />

to mechanically refrigerate the entire<br />

foundati<strong>on</strong> to maintain the permafrost. This<br />

opti<strong>on</strong> was <strong>on</strong>e of five alternatives offered by<br />

CRREL. Plans and specificati<strong>on</strong>s were prepared<br />

and forwarded to the c<strong>on</strong>tractor.<br />

Four ].oops of copper tubing were installed<br />

around the perimeter of the foundati<strong>on</strong> while 16<br />

loops were installed in the bottom of the crawl<br />

space. The loops varied from 107 to 391 m in<br />

length with a total combined length of 4400 m,<br />

of which 3450 m are beneath the heated floor<br />

space. The 2.2 cm outside diameter copper loops<br />

(spaced 0.45 m center to center) were buried<br />

beneath 7.6 cm of sand, 7.6 cm of spray applied<br />

rigid closed cell 2-comp<strong>on</strong>ent urethane foam,<br />

and covered in turn with a layer of spray<br />

applied fireproofing.<br />

Refrigerated ethylene glycol was pumped through<br />

the coils having been cooled with two 11 kw<br />

capacity compressor/chiller packages. Initial<br />

freezeback was to be accomplished with both<br />

compressors running. Following initial<br />

freezeback, the sec<strong>on</strong>d unit would serve as<br />

back-up. Eight fan coil heat transfer units<br />

(unit coolers) in two groups of four were<br />

c<strong>on</strong>nected in parallel to provide outside air<br />

cooling when ambient air temperatures dropped<br />

below -12°C. Switchover from the refrigerati<strong>on</strong>/chiller<br />

unit to the unit coolers was<br />

performed automatically.<br />

In September 1981, a review of the operati<strong>on</strong>al<br />

history of the refrigerati<strong>on</strong> system was<br />

performed and it was determined that the<br />

mechanical system had been operating with less<br />

than 100 percent of all subsystems properly<br />

functi<strong>on</strong>ing. The building manager indicated<br />

that hiring properly trained pers<strong>on</strong>nel to<br />

operate the system was a major problem. The<br />

turnover rate for operators was so high that<br />

new operators were almost always being trained.<br />

The refrigerati<strong>on</strong> system, with its subsystems,<br />

was a complicated operati<strong>on</strong> which required<br />

c<strong>on</strong>tinual m<strong>on</strong>itoring and maintenance to<br />

functi<strong>on</strong> properly. This amount of "Tender<br />

Loving Care" could not be obtained from short<br />

term operators. Because the system was Located<br />

in a somewhat remote city in Alaska, there were<br />

often delays involving ordering and delivery of<br />

repair items and scheduling of repairmen. Of<br />

course, any time the system was inoperative,<br />

subgrade warming and thawing took'place.<br />

It was estimated that the mechanical system<br />

cost $2300.00/rn<strong>on</strong>th to operate in the summer<br />

and $1200.00/m<strong>on</strong>th~in the winter (1981 costs).<br />

Assuming 44 m<strong>on</strong>ths of summer operati<strong>on</strong> and 74<br />

m<strong>on</strong>ths of winter operati<strong>on</strong>, the total annual<br />

operating cost for the mechanical system was<br />

$19,350.00 (U.S.) in 1981. Additi<strong>on</strong>ally,<br />

periodic re-leveling was still. being performed<br />

as settlement c<strong>on</strong>tinued at a slower rate.<br />

In 1983, the State of Alaska turned the<br />

operati<strong>on</strong> of the Kotzebue Pi<strong>on</strong>eer Home over to<br />

the Kotzebue community where it became the<br />

Kotzebue Senior Citizen's Cultural Center<br />

managed by Maniilaq Corp. In June 1984,<br />

Maniilaq advertised for a re-design of the<br />

refrigerati<strong>on</strong> system. The system accepted was<br />

a c<strong>on</strong>versi<strong>on</strong> of the circulating glycol soil<br />

cooling system to a two-phase passive system<br />

(thcrmosyph<strong>on</strong>) which used the exjsting<br />

mechanical refrigerati<strong>on</strong> and unit cooler system<br />

as back-up.<br />

1278

EVALUATION OF MECHANICAL SYSTEM<br />

The total heat transfer through the floor was<br />

estimated using temperature measurements<br />

acquired <strong>on</strong> June 26 & 27, 1984. After the<br />

total heat transfer was known, the pressure<br />

drop through the system and the performance of<br />

the unit coolers was estimated.<br />

The old system performance has been approximated<br />

by combining an equati<strong>on</strong> which defines a row<br />

of infinite circular holes at equal depth and<br />

equal spacing in a semi-infinite solid, and an<br />

equati<strong>on</strong> which defines a row of infinite<br />

circular holes in midplane of an infinite plate<br />

(Heuer, 1985), as shown in Figure 2.<br />

glycol. Thc overall thermal c<strong>on</strong>ductance of the<br />

unit cooler using glycol was calculated as 0.93<br />

kw/"C. The manufacturer predicted a c<strong>on</strong>ductance<br />

of 5.20 kw/"C when using R-22 as the<br />

refrigerant c<strong>on</strong>densing in a unit cooler.<br />

The average m<strong>on</strong>thly air temperature in Rotzebue<br />

reaches a minimum of -2O'C. At this temperature,<br />

the glycol would be cooled 6.1°C with thc<br />

compressor off and <strong>on</strong>e unit cooler operating.<br />

If the two unit coolers were operated in<br />

parallel, the glycol would be cooled to -4.4'C.<br />

The use of the system without the compressor<br />

was practical <strong>on</strong>ly when the air temperature was<br />

below -15°C.<br />

Ru=<br />

d,u > D<br />

G, n K, N<br />

C02 PASSIVE REFRIGERATION<br />

The passive refrigerati<strong>on</strong> system was designed<br />

to remove heat from the underlying soil during<br />

the winter so that the depth of 'thaw in the<br />

summer will be acceptable. Also the permafrost<br />

would be brought back up to the seas<strong>on</strong>al frost<br />

depth. The system was designed to use carb<strong>on</strong><br />

dioxide as the primary refrigerant. The carb<strong>on</strong><br />

dioxide evaporates in the underfloor tubing and<br />

the vapor flows to the primary and heat reclaim<br />

c<strong>on</strong>denser units, where it c<strong>on</strong>denses and flows<br />

back down to the underfloor tubing. This cycle<br />

c<strong>on</strong>tinues as l<strong>on</strong>g as the temperature beneath<br />

the floor is warmer than outside ambient air<br />

temperture (L<strong>on</strong>g, 1963; Bunchko, et all 1973).<br />

With a maximum crawl space temperature of 21"C,<br />

an annual depth of thaw was calculated to be<br />

1.1 m using the Modified Berggren equati<strong>on</strong>.<br />

FOR Rd OR G, TRANSPOSE u's<br />

NOMENCLATURE:<br />

AND d's<br />

d = Downward Distance to Heat Source<br />

D = Diameter<br />

K = Thermal C<strong>on</strong>ductivity<br />

p. = Spacing<br />

N = Length<br />

q = Heat Flow Rate<br />

R = Thermal Resistance<br />

T = Temperature<br />

u = Upward Distance to Heat Source<br />

SUBSCRIPTS:<br />

d = Downward<br />

e = Evaporator<br />

u = Upward<br />

R FIGURE 2<br />

Determinati<strong>on</strong> of Soil Thermal Resistance<br />

The primary c<strong>on</strong>denser was custom manufactured<br />

using finned radiators that are normally fitted<br />

to commercially available two-phase thermosyph<strong>on</strong>s<br />

and is shown <strong>on</strong> Figure 3. The c<strong>on</strong>dyctance<br />

of the primary c<strong>on</strong>denser system is 3.6<br />

kw/"C at an average winter air velocity of 6.0<br />

m/sec (Zarling and Haynes, 1985). The c<strong>on</strong>ductance<br />

of the heat reclaim c<strong>on</strong>denser (Figure 4 )<br />

is 1.6 kw/'C when providing 2.4 l/sec of<br />

make-up air to the ventilati<strong>on</strong> system.<br />

The average rate of heat removal from the floor<br />

and the ground was found to be 25 kw with the<br />

coils at -4.4"C. There are 20 loops, so the<br />

average heat flux per loop was 1.25 kw.<br />

The performance of the air cooled unit cooler<br />

was determlncd by knowing the heat flux and the<br />

temperature difference between tho air and<br />

1279

- VAPOR ,PRIMARY<br />

CONDENSER<br />

HEAT )<br />

RECLAIM<br />

CONDENSER<br />

1<br />

VAPOR MANIFOLD<br />

I<br />

LIQUID MANIFOLD<br />

BACK-UP CONDENS<br />

wp<br />

CONDENSER<br />

FIGURE 5<br />

Schematic of the Back-up C<strong>on</strong>densing System<br />

FIGURE 4<br />

Schematic of Passive Carb<strong>on</strong> Dioxide System<br />

A schematic diagram of the passive carb<strong>on</strong><br />

dioxide system is shown <strong>on</strong> Figure 4. Valves<br />

have been provided to permit isolati<strong>on</strong> of any<br />

<strong>on</strong>e loop in case a leak should develop. A<br />

Coriolis type mass flow meter and a pressure<br />

gauge were installed in early February 1988 to<br />

accurately m<strong>on</strong>itor the heat flow of the entire<br />

system as well as the individual loops.<br />

Heat transfer permits over 200 kw through the<br />

passive system al<strong>on</strong>e. Once the permafrost has<br />

recovered to the seas<strong>on</strong>al depth of thaw, annual<br />

cooling will be 470 x 106 kJ for an average<br />

rate of approximately 22 kw. The heat transfer<br />

available to preheat the make-up air for the<br />

Senior Center ventilati<strong>on</strong> system will be 140 x<br />

106 kJ for an average rate of preheating of 7.7<br />

kw .<br />

BACK-UP CONDENSIN& SYSTEM<br />

The back-up c<strong>on</strong>densing system can make use of<br />

the two existing 11 kw unit packages to provide<br />

refrigerati<strong>on</strong> during the summer m<strong>on</strong>ths if it<br />

should ever be required. The compressor/chiller<br />

packages utilize R-502 refrigerant. The<br />

R-502 is c<strong>on</strong>densed in the compressor secti<strong>on</strong> by<br />

evaporating R-22 which is c<strong>on</strong>densed in the<br />

existing unit coolers located outside the<br />

structure. By utilizing R-22 instead of pumped<br />

glycol, the c<strong>on</strong>ductance of the unit coolers has<br />

been increased more than five times. The<br />

evaporating R-502 in the chiller secti<strong>on</strong><br />

c<strong>on</strong>denses the R-12 which then evaporates in the<br />

back-up c<strong>on</strong>denser c<strong>on</strong>densing C02. The back-up<br />

c<strong>on</strong>denser also serves as a manifold to feed<br />

carb<strong>on</strong> dioxide c<strong>on</strong>densate to each of the 20<br />

copper loops under the floor. All c<strong>on</strong>densate<br />

transport is by gravity feed and no pumps are<br />

required. The circuits for the back-up<br />

c<strong>on</strong>densing system are shown <strong>on</strong> Figure 5. Note<br />

that R-I 2, R-22 , and R-502 axe fluorocarb<strong>on</strong><br />

refrigerants. Each refrigerant was selected<br />

for its performance over specific temperature<br />

and pressure ranges. The R-22 and R-12 systems<br />

are operating as thermosyph<strong>on</strong>s while the R-502<br />

vapor is compressed and re-expanded for cooling<br />

of the chiller.<br />

CONCLUSIONS<br />

The passive system used to replace an active<br />

glycol system has stopped the degradati<strong>on</strong> of<br />

the permafrost and within a few years will<br />

effect complete recovery of the permafrost.<br />

Operati<strong>on</strong>al and maintenance costs <strong>on</strong> the<br />

passive system are nil compared to the<br />

mechanical system. Preheating of make-up air<br />

will further reduce the utility cost of the<br />

Kotzebue Senior Citizen's Cultural Center.<br />

The successful c<strong>on</strong>versi<strong>on</strong> of a mechanical<br />

refrigerati<strong>on</strong> system to a passive (thermosyph<strong>on</strong>)<br />

system offers another alternative to the<br />

high maintenance and energy requirements of<br />

mechanical systems.<br />

REFERENCES<br />

Abbott, R.D., Bestwick, L.K. (1975). Preliminary<br />

Subsurface Investigati<strong>on</strong>, Differential<br />

Settlement, Kotzebue Pi<strong>on</strong>eers Home,<br />

Kotzebue, Alaska. Shann<strong>on</strong> E, Wils<strong>on</strong>, Inc.,<br />

Fairbanks, Alaska.<br />

Brown, J.E. and P6w6, T.L. (1973). Distributi<strong>on</strong><br />

Of <strong>Permafrost</strong> In North America And Its<br />

Relati<strong>on</strong>ship To The Envir<strong>on</strong>ment: A<br />

Review, 1963-1973. Proc. 2nd Int'l C<strong>on</strong>f.<br />

<strong>Permafrost</strong> - North American C<strong>on</strong>tributi<strong>on</strong>,<br />

71-100.<br />

Buchko, N.A., Onosovskiy, V.V., and Sokolov,<br />

V.S. (1973). Liquid-Vapor Heat Transfer<br />

Devices Of The 'L<strong>on</strong>g' Thermo-Pile Type For<br />

Cooling And Freezing The Ground When<br />

Building In Regi<strong>on</strong>s With Harsh Climates.<br />

Proc. 2nd Int'l C<strong>on</strong>f. <strong>Permafrost</strong>. - USSR<br />

C<strong>on</strong>tributi<strong>on</strong>,

Crory, F.E. (1976). Final Report <strong>on</strong> Foundati<strong>on</strong><br />

Investlgati<strong>on</strong> for Kotzebue Pi<strong>on</strong>eer Home,<br />

Kotzebue, Alaska. CRREL, Hanover, New<br />

Hampshire.<br />

Ferrians Js., O.J. (1965). <strong>Permafrost</strong> Map of<br />

Alaska. U.S. Geological Survey, Washingt<strong>on</strong><br />

D.C.<br />

Heuer, C.E., L<strong>on</strong>g, E.L., and Zarling, J.P.<br />

(1985). Passive Techniques for Ground<br />

Temperature C<strong>on</strong>trol. Thermal Design/C<strong>on</strong>siderati<strong>on</strong>s<br />

In Frozen Ground Engineering.<br />

ASCE, 72-154.<br />

L<strong>on</strong>g, E.L. (1963). The L<strong>on</strong>g Thermopile. Proc.<br />

1st Int'l C<strong>on</strong>f. <strong>Permafrost</strong>. Nat'1,Academy<br />

of Sciences, 487-491.<br />

Zarling, J.P. and Haynes, F.D. (1985). Therrnosyph<strong>on</strong><br />

Devices and Slab-On-Grade Foundati<strong>on</strong><br />

Design. State of Alaska, Dept, of<br />

Transportati<strong>on</strong> and Public Facilities,<br />

Report No. AK-RD-86-16.<br />

1281

LONG TERM PLATE LOAD TESTS ON MARINE CLAY IN SVEA, SVALBARD<br />

T. Lunnel and T. Eidsmoed<br />

Wffshore Soil Investigati<strong>on</strong> Secti<strong>on</strong>, Norwegian Geotechnical Institute, Norway<br />

2Norwegian State Railways, Drammen, Norway (formerly of NGI)<br />

SYNOPSIS Six instrumented faotings have been installed to depths varying between<br />

1.2 and 2.2 m in the saline Svea clay in order to measure the in situ l<strong>on</strong>g term creep<br />

rate. The shallowest plates are loaded to about 50 kPa and the warmest measured temperature<br />

just below the plates are - 2.5 to - 30 C resulting in a maximum creep rate of 2<br />

- 2.5 mm/m<strong>on</strong>th. which is significantly less than what was predicted based <strong>on</strong> laboratory<br />

teste. The deepest plates are given a maximum load of 134 kPa. The warmest measured temperature<br />

is - 4.50 C and the corresp<strong>on</strong>ding maximum creep rate is 4 mm/m<strong>on</strong>ths, which is<br />

close to what was predicted.<br />

INTRODUCTION<br />

Creep behaviour of foundati<strong>on</strong> permafrost<br />

soil at Svalbard has so far been estimated<br />

based <strong>on</strong> laboratory tests <strong>on</strong> obtained<br />

samples (Furuberg and Johansen, 1983). Using<br />

creep laws (e.g. Ladanyi, 1972) alloWable<br />

footing stress has then been worked out<br />

based <strong>on</strong> the results of the laboratory tests<br />

and assumed ground temperatures. For<br />

Svalbard mast efforts have been c<strong>on</strong>centrated<br />

<strong>on</strong> the saline Svea clay. In order to improve<br />

our knowledge about the in situ creep behaviour<br />

of Svea clay it was decided to carry<br />

out a series of l<strong>on</strong>g term plate load tests<br />

with different fdundati<strong>on</strong> depths and stress<br />

levels. The characteristics of the Svea clay<br />

are described by Gregersen, Phukan and<br />

Johansen (1983).<br />

TEST SITE AND SOIL CONDITIONS<br />

The test site is located at Svea <strong>on</strong><br />

Svalbard. The Svea clay is a marine clay .<br />

with a salt c<strong>on</strong>tent of about 35 g/1 and with<br />

up to 10 mm thick icelenses oriented both<br />

horiz<strong>on</strong>tally and almost vertically.<br />

Laboratory creep tests have been carried out<br />

<strong>on</strong> Svea clay at temperatures of -5°C and<br />

-3OC (Johansen, 1981, Furuberg and Johansen,<br />

1983). The tests are mostly carried out <strong>on</strong><br />

unc<strong>on</strong>fined samples, but some tests are d<strong>on</strong>e<br />

with a cell pressure. Fig. 1 summarizes the<br />

tests d<strong>on</strong>e at a temperature of -3OC. Table 1<br />

includes the interpretati<strong>on</strong> of the test<br />

30<br />

s<br />

$- 20<br />

L<br />

10<br />

0<br />

0 1000 2000 3000 4000 so00<br />

TIME, min<br />

After Furuberg and Johansen 11983)<br />

Fig. 1. NTH’S creep tests <strong>on</strong> Svea clay at<br />

-3OC (after Furuberg and Johansen,<br />

1983).<br />

results from Furuherg and Johansen (1983)<br />

using the creep model of Ladanyi (1972) or<br />

Vyalov et. a1 (1966). It must be emphasized<br />

that there is quite a spread in the data.<br />

Close to the locati<strong>on</strong> of the plates a permafrost<br />

stati<strong>on</strong> has recorded air temperature<br />

and ground temperature down to 3 m below the<br />

soil surface over the last ten years<br />

(Bakkeholi, 1982). Bakkehei and Bandis (1987)<br />

have presented 5-days medium temperature in<br />

air and in the depth interval 0 .0-2.5 rn<br />

below ground level. Fig. 2 shows an example<br />

of these data for 1984.<br />

1282

Table 1. Interpretati<strong>on</strong> of creep tests at<br />

-3OC and -5Oc<br />

t = -3OC<br />

Formula<br />

n = dimensi<strong>on</strong>less exp<strong>on</strong>ent, dependant <strong>on</strong><br />

soil type and temperature<br />

uc = c<strong>on</strong>stant, dependant <strong>on</strong> soil type and<br />

temperature<br />

= c<strong>on</strong>stant dependant <strong>on</strong> soil type, but<br />

independant <strong>on</strong> temperature.<br />

.i = rate of strain<br />

uf = applied stress (kPa)<br />

" I<br />

C<strong>on</strong>crete<br />

plate<br />

0.2m thick<br />

I<br />

I-<br />

9 -2 .5<br />

c3<br />

-3<br />

*o<br />

Fig. 3. Arrangement of footings or plates.<br />

22 mm top-plate<br />

Fig. 2. Temperature recorded at NGI<br />

permafrost stati<strong>on</strong> in 1984.<br />

FOUNDATIONS AND SETUP OF PLATES<br />

0<br />

0<br />

m<br />

Steel column<br />

B200xB mm<br />

Backfill of aravel<br />

The footings or plates are placed in two<br />

groups of three with center distance of 5.8<br />

m as shown <strong>on</strong> Fig. 3. A hole was digged<br />

using a machine to the desired foundati<strong>on</strong><br />

level for each footing. The bottom of each<br />

hole was levelled off with a thin gravel<br />

layer 50 to 200 mm thick. A 1 m diameter, 22<br />

m thick steel plate was placed directly <strong>on</strong><br />

the gravel layer followed by an isolati<strong>on</strong><br />

layer of styrofoam (HD 300). As shown in<br />

Fig. 4 stiffened steel columns ( 4 200 m)<br />

Gravel layer<br />

Fig. 4. Details of footing.<br />

1283

where placed <strong>on</strong> top of the styrofoam. The<br />

steel columns were lubricated with gear oil<br />

and a plastic sheet placed around it in<br />

order to reduce frost heave forces. On top<br />

of the columns a triangular c<strong>on</strong>crete plate<br />

was cast which c<strong>on</strong>stitutes part of the load<br />

<strong>on</strong> the footings. For the shallow footings (2<br />

to 1.2 m depth and 1 to 1.1 m degth)the<br />

c<strong>on</strong>crete plate was 200 mm thick. For the<br />

deeper footings (2.1-2.2 m) the thickness of<br />

the c<strong>on</strong>crete plate was 300 mm. Gravcl was<br />

used to fill back about I m above the<br />

footing, the rest of the excavated hole was<br />

filled up with the orlginal Svea clay.<br />

The footings or plates were installed in<br />

November 1986 and the c<strong>on</strong>crete plates cast<br />

in Docember 1986.<br />

INSTRUMENTATION<br />

Fig. 6 shows schematically the foundatian<br />

depth for each footing and the locati<strong>on</strong> of<br />

the thermistors and the settlement gauges.<br />

Footinps No. 1 and 6 (see Fig. 5 ) have<br />

settlement gauges relative to 0.75 m and<br />

1.75 m below the plate. All the other<br />

footings have settlement measurement gauges<br />

relative to 1.25 m below the plate.<br />

The settlement measurement system c<strong>on</strong>sist Of<br />

an inner rod with a tip of diameter SO mm<br />

which is anchored at required depth. First a<br />

hole with a diameter of 70 mm was drilled<br />

and then the 50 mm diameter tip was frozen<br />

into the bottom of the hole by a mixture of<br />

sand and water. Outside the inne rod i8<br />

mounted a protecti<strong>on</strong> tube from 0.25 m above<br />

the tip to 0.25 m above the footing. The<br />

protecti<strong>on</strong> tube is filled with oil to prevent<br />

the inner rod from freezing. An outer<br />

tube is fixed to the footing. Between the<br />

outer tube and the protecti<strong>on</strong> tube there is<br />

no c<strong>on</strong>necti<strong>on</strong>. As the plate settles relative<br />

to the fixed point, settlements are read<br />

using the NGI precisi<strong>on</strong> settlement gauge<br />

system. Outside the plates a fixed point is<br />

anchored to a depth of 6 m bclow ground<br />

level (adapti<strong>on</strong> after Bozozuk et al, 1963).<br />

As a check <strong>on</strong> the precisi<strong>on</strong> settlement<br />

gauges, settlements of each plate can also<br />

be measured by levelling relative to the<br />

fixed paint.<br />

T20<br />

F(de1.75m) 1 OTi6<br />

oT15<br />

4<br />

I<br />

Dedh of<br />

AS shown in Fig. 5 a number of thermistors<br />

(NTC-type from Fenwal Electr<strong>on</strong>ics) were<br />

installed at various depths below ground<br />

level. The thermistors are read using an<br />

ordinary voltmeter.<br />

The bottom of the steel plate for foundati<strong>on</strong><br />

no. 6 is equipped with two earth pressure<br />

cells, (Ge<strong>on</strong>or vibrating wire type), <strong>on</strong>e in<br />

the centre and <strong>on</strong>e 0.25 m from the center.<br />

LOADING<br />

After the footings were installed and the<br />

c<strong>on</strong>crete plates cast final loading were<br />

delayed until the ground temperatures<br />

reached a normal level. On the 25th April<br />

1987 additi<strong>on</strong>al load was put <strong>on</strong> using 1<br />

mJ c<strong>on</strong>crete blocks as shown in Fig. 3. This<br />

resulted in calculated average c<strong>on</strong>tact<br />

stress for each plate as shown <strong>on</strong> Fig. 3.<br />

MEASUREMENTS<br />

Measurements have been taken at 2-6 weeks<br />

intervals since April, 1987.<br />

Temperatures<br />

Fig. 5. Footing depths and locati<strong>on</strong>s of<br />

thurmistors and settlement gauges.<br />

Fig. 6 show6 the maximum recorded ternperaturc<br />

just below the plate for all<br />

footings in the observati<strong>on</strong> period as a<br />

functi<strong>on</strong> of depth. As a reference the range<br />

of max. temperaturea from the nearby permafrost<br />

stati<strong>on</strong> are included. It can be<br />

observed that the temperatures just below<br />

the footings fall well within the range of<br />

measured values from the permafrost stati<strong>on</strong><br />

over the period 1978 - 1984, In Fig. 7 the<br />

1284

temperature juat below each plate have been<br />

plotted as a functi<strong>on</strong> of time.<br />

Settlements<br />

Fig. 8 shows the settlements as meaaured by<br />

the precisi<strong>on</strong> settlement gauges. Clearly <strong>on</strong>e<br />

of the settlement gauges - F do by some<br />

reas<strong>on</strong> not functi<strong>on</strong> properly. This is c<strong>on</strong>firmed<br />

by the check levelling which was<br />

carried out 4th September. On Fig. 8 we have<br />

also marked the maximum settlement rate in<br />

mm per m<strong>on</strong>th, and at what time it occurs. As<br />

expected this to a large extent coincides<br />

with the maximum temperatures as recorded<br />

just below the plates. From Fig. 8 it can be<br />

observed that after November 1987 there are<br />

no settlements for any of the plates. In<br />

fact plates 1 and 6 show a small heave. The<br />

reas<strong>on</strong> for this may be that some frost heave<br />

forces have acted an the steel columns even<br />

if precauti<strong>on</strong>s were taken to prevent this<br />

(see Chapter 3).<br />

Fig. 6. Temperatures recorded just below<br />

footings compared with warmest 5<br />

day medium temperatures for period<br />

1978-1985.<br />

Earth pressures<br />

As menti<strong>on</strong>ed before plate 6 was equipped.<br />

with two earth pressure cells, <strong>on</strong>e in the<br />

centre and <strong>on</strong>e 250 mm from the centre. The<br />

rr<br />

1987 1988<br />

APR lHAYlJUNE I JULY1 AUGISEPI OCT I NOV I DEC JAN 1 FEB ]MAR<br />

0, q<br />

3mn/m<strong>on</strong>th - man. settlement<br />

a<br />

I<br />

01 .<br />

I PLATE 2 "1<br />

PLATE 2<br />

2.5 mdn<strong>on</strong>th<br />

i.75m depth<br />

0.75111 depth<br />

Z mmh<strong>on</strong>th 1<br />

Y<br />

L<br />

U<br />

-<br />

r n<br />

n<br />

I PLATE &<br />

0-<br />

PLATE 5<br />

-<br />

-. ,.<br />

I I I%,<br />

--- "4<br />

_I<br />

d PLATE 3<br />

E<br />

0<br />

10 - PLATE 4<br />

4 imm/m<strong>on</strong>th<br />

Q -<br />

1 1 1 1 , 1 1 1 1 1 ,<br />

I 1 1 1 1 1<br />

L mn/n<strong>on</strong>th<br />

I<br />

Y<br />

/ --==<br />

APRIHAYIJUNEIJULYIAUGISEP~OCT INOV~DEC JAN IFEB IMAR<br />

1987 ' 1988<br />

J<br />

AFR~HAY LUNE IJULY I AUG ISEPII OCT I NOV I DEC JAN I FEE IMAR<br />

# 1987 1988<br />

Fig. 7. Maximum observed temperatures vs.<br />

depth.<br />

Fig. 8. Recorded settlements.<br />

1285

measured earth pressures have varied little<br />

with time and average values to up Novtmber<br />

1981 are 144 kPa for the middle of the plate<br />

and 137 kPa from center of plate. The theoretical<br />

average c<strong>on</strong>tact pressure below plate<br />

no. 6 is 145 kPa which agree reas<strong>on</strong>ably well<br />

with the measured values and c<strong>on</strong>firm that<br />

the computed additi<strong>on</strong>al stresses are<br />

correct. After November 1987 there is a<br />

significant reducti<strong>on</strong> in the measured earth<br />

pressures. A tentative explanati<strong>on</strong> is, as<br />

menti<strong>on</strong>ed in the last secti<strong>on</strong>, that frost<br />

heave forces have acted <strong>on</strong> the steal<br />

columns.<br />

CQMPARISON BETWEEN MEASURED AND<br />

COMPUTED SETTLEMENT RATES<br />

Fig. 9 compares predicted and recorded<br />

settlement rates for all plates. It can be<br />

observed that for the deepest plates (2.2<br />

and 1.8 m depth) the measured and predicted . -<br />

settlements compares reas<strong>on</strong>ably well. For<br />

the two shallowest plates (1.2 m depth) the<br />

predicted settlements are much larger than<br />

the observed settlements. This may indicate<br />

that the laboratory creep parameters dstermined<br />

from the highest temperatures of - 3oC<br />

are possibly unreliable and some additi<strong>on</strong>al<br />

laboratory tests <strong>on</strong> samples taken lmmediately<br />

below the plates should be performed<br />

at temperatures of - 30C to - 4oC. The present<br />

stress level will be kept for <strong>on</strong>e more<br />

year, then it will be c<strong>on</strong>sidered to increase<br />

the stress level for all footings.<br />

Prior to loading of the plates the maximum<br />

creep rate of each footing was predicted<br />

Lupne (1987) based <strong>on</strong> the fallowing:<br />

a) A ground temperature profile from the<br />

measurements at the nearby permafrost<br />

stati<strong>on</strong> (Fig. 6).<br />

b) Creep parameters from the tests<br />

carried out by Furuberg and Johansen<br />

(1983) and Jahansen (1981). For tem-<br />

per,atures between - 3oC and - SoC,<br />

linear interpolati<strong>on</strong> has been used for<br />

the parameters n and uc.<br />

e) Stress distributi<strong>on</strong> with depth<br />

according to-elastic theory (Janbu,<br />

1971).<br />

Decrease In temperature with depth was taken<br />

into account by dividing the soil below the<br />

plates into layers of 0.2 m thickness. For<br />

each layer the strain rate, e, has been computsd<br />

from the farmula given in table 1. The<br />

total strain rate has then been computhd by<br />

summati<strong>on</strong>. The calculati<strong>on</strong>s show that the<br />

creep sattlements'are virtially c<strong>on</strong>fined to<br />

the upper 0.4 m below the plates.<br />

FOUNDATION PRESSURE, AP, kPa<br />

0 20 40 60 EO 100 120 1M 160<br />

SUMMARY AND CONCLUSIONS<br />

Six footings have been installed to depths<br />

varying between 1,2 and 2.2 m in the saline<br />

Svea clay in order to measure the in situ<br />

l<strong>on</strong>g term creep rate.<br />

The footings have bean instrumented so that<br />

temperature at various depths above and<br />

belaw the plates can be measured. For <strong>on</strong>e of<br />

the footings c<strong>on</strong>tact stresses are also<br />

measured. Settlements of the footings are<br />

measured by precisi<strong>on</strong> settlement gauges<br />

relative to fixed points 0.75 to 1.15 m<br />

belaw the plates.<br />

The two shallowest plates (1.2 m depth) are<br />

loaded by additi<strong>on</strong>al vertical stresses of<br />

52 kPa. The warmest temperature below these<br />

plates are measured to be -2.5 to -3oC and<br />

the corresp<strong>on</strong>ding maximum creep rates are 2<br />

- 2.5 mm/m<strong>on</strong>ths, which are significantly<br />

smaller than what was predicted based <strong>on</strong><br />

laboratory tests.<br />

The three deepest plates (2,2 m depth) are<br />

loaded by additi<strong>on</strong>al vertical stresses of<br />

100 to 134 kPa. The warmest temperatures in<br />

the soil below these plates are measured to<br />

be -4.5oC and the correap<strong>on</strong>ding maximum<br />

creep rates are 1-4 mm/m<strong>on</strong>ths (increasing<br />

with increasing stress), which is reas<strong>on</strong>ably<br />

close to what was predicted based <strong>on</strong> laboratory<br />

tests.<br />

2 10<br />

8<br />

E<br />

1 15<br />

X<br />

Fig. 9. Comparis<strong>on</strong> between predicted and<br />

recorded settlements.<br />

ACKNOWLEDGEMENT<br />

The project described herein is part of a<br />

research program supported by Statoil. The<br />

authors wish to acknowledge Store Norske<br />

Kullkampani, Spitsbergen (SNSK) for<br />

assisting with loglstical support and<br />

following up the measurements.<br />

1286

REFERENCES<br />

1. Bakkehei, S. (1982)<br />

Datainnsamling pB permafroststas<strong>on</strong>en I<br />

Svea, Svalbard Frost i jord, publ. Nr.<br />

24, Oslo.<br />

2. Eakkehai, S. and C. Bandis (1987)<br />

A preliminary analysis of climatic<br />

data from the permafrost stati<strong>on</strong> at<br />

Svea, Spitzbergen Frost I jord<br />

nr. 26, Oslo.<br />

3. Bozozuk, M.. G.H. Johnst<strong>on</strong> and J.J.<br />

Hamilt<strong>on</strong> (1963)<br />

Deap bench marks in clay and permafrost<br />

areas. In Field testing of<br />

soils, ASTM Sp. Tech. Pub. No. 322, p.<br />

265.<br />

4. Gregersen, O., A. Phukan and T. Sohansen<br />

(1983)<br />

Engineering properties and foundati<strong>on</strong><br />

design alternatives in marine Svea<br />

clay, Svalbard. <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g><br />

<strong>on</strong> <strong>Permafrost</strong>, 4. Fairbanks,<br />

Alaska 1983. Proceedings, pp. 384-388.<br />

Also publ. in: Norwegian Gsotechnical<br />

Institute, Oslo, Publ. No. 159, 1985.<br />

5. Furuberg, T. og T. Johansen (1983)<br />

Svealsira sin mekaniske etyrke. Rapport<br />

til NTNF. NTH Rapport No,<br />

F-63.03.<br />

6. Janbu, N. (1971)<br />

Qrunnlag i geoteknikk. Tapir forlag,<br />

Tr<strong>on</strong>dhaim.<br />

7. Johansen, T. (1981)<br />

Krypforsak pb Svealeirc. Rapport til<br />

NTNF. NTH Rapport F.081.05.<br />

8. Ladanyi, B. (1972)<br />

An engineering theory of creep in frozen<br />

soils. Canadian Geotechnical Journal<br />

Vo1. No. 1, pp. 63-79.<br />

9. Lunne, T. (1987)<br />

Arktisk geotcknikk og fundarnentering.<br />

Forutberegnede krypsetninger for<br />

platebelastningsforsmk i Svea. Intern<br />

Rapport 52704-5. 20. januar, 1987.<br />

10. Vyalov, S.S. et. a1 (1966)<br />

Methods of determining creep, l<strong>on</strong>g<br />

term strength and compressibility<br />

characteristics of frozen soil. Nauka<br />

Moscow Nat. Res. Counc. of Canada.<br />

Techn. Trans. 1364 Ottawa, 1969.<br />

1287

MELIORATION OF SOILS OF CRYOLITHOZONE<br />

O.V. Makeev<br />

Institute of Soil Science and Photosynthesis USSR, Academy of Sciences,<br />

Pushchino, Moscow Regi<strong>on</strong>, USSR, 142292<br />

SYNOPSIS Effective complex meliorati<strong>on</strong> of soils with frost in the profile is possible if a simultaneous<br />

c<strong>on</strong>trol of the two processes, namely frost and soil formati<strong>on</strong> is ensured. A number of soils of cryolithoz<strong>on</strong>e<br />

due to the permafrost effect as a factor of soil formati<strong>on</strong> specific cryogenic features, horiz<strong>on</strong>s and regimes,<br />

thus forming new types of soils, the most peculiar of which are cryogenic frozen <strong>on</strong>es.<br />

Specific character of meliorati<strong>on</strong> techniques is increased from the south to the north in the cryolithoz<strong>on</strong>e.<br />

The meliorati<strong>on</strong> technology of the following ecologo-meliorative groups of tundra soils: frozen tundra mineral<br />

gley, frozen tundra bog (peat) gley, coldgenic tundra soils of the bottoms .of dried -up thermokarst lakes,<br />

coldgenic tundra floodplain and frozen tundra surface-gley, as well as recultivati<strong>on</strong> of the soils destroyed<br />

by excavati<strong>on</strong>s; phytomeliorati<strong>on</strong> of the frozen tundra surface-gley soils are described in the present paper.<br />

The data <strong>on</strong> effective meliorati<strong>on</strong> are also presented.<br />

In the northern hemisphere the formati<strong>on</strong> of soils<br />

and soil cover is greatly affected by their annual<br />

freezing. and thawing (Makeev, 1981). The greatest<br />

effect is observed in the northern regi<strong>on</strong>s where<br />

the soil profile often rests <strong>on</strong> permafrost.<br />

Frost as a factor of soil formati<strong>on</strong> accounts for a<br />

number of soil properties including the formati<strong>on</strong> of<br />

their tax<strong>on</strong>s. These soils are c<strong>on</strong>sidered by us to<br />

bel<strong>on</strong>g to a big tax<strong>on</strong>omic group - massif of<br />

freizing-thawing or short-term trawfrost soils including<br />

megaformati<strong>on</strong>s of cryogenic and n<strong>on</strong>cryo- '<br />

genic soils (Makeev, 1986). The megaformati<strong>on</strong> of<br />

the freezing-thawing cryogenic soils includes the<br />

Soils formed mainly in the high northern and<br />

southern latitudes as well as in the corresp<strong>on</strong>ding<br />

z<strong>on</strong>es of mountain systems. The genesis development<br />

and functi<strong>on</strong>ing of such soils are greatly<br />

affected by negative temperatures resulting in phase<br />

transformati<strong>on</strong> of soil moisture into ice and vice<br />

versa. These soils are to have <strong>on</strong>e or several<br />

specific cryogenic horiz<strong>on</strong>s in their profiles and to<br />

develop under c<strong>on</strong>diti<strong>on</strong>s of cryogenic (thermal,<br />

water, biological, etc.) regimes: During this process<br />

both cryogenic and n<strong>on</strong>cryogenic horiz<strong>on</strong>s are<br />

destroyed and their parts can move in various directi<strong>on</strong>s.<br />

The freezing-thawing soils unaffected by the soil<br />

cryogenesis, Le. without profile properties, c<strong>on</strong>tent,<br />

solum and regime characteristics bel<strong>on</strong>g to the megaformati<strong>on</strong><br />

of the freezing-thawing n<strong>on</strong>cryogenic<br />

soils. They include, for example, all the soils with<br />

a short-term and shallow soil profile freezing (sand<br />

rubble, etc.).<br />

The mefaformati<strong>on</strong> of the cryogenic soils includes<br />

two formati<strong>on</strong>s: frozen and coldgenic <strong>on</strong>es,<br />

The frozen formati<strong>on</strong> c<strong>on</strong>sists of the freczing-<br />

-thawing cryogenic soils, the profile of which is<br />

resting <strong>on</strong> permafrost rocks, being reached by the<br />

layer of seas<strong>on</strong>al thawing during winter<br />

these soil are called overfrozen <strong>on</strong>es. Their<br />

rage temperature is negative.<br />

time. Thus,<br />

ave-<br />

hleliorati<strong>on</strong> of the following soils from the formati<strong>on</strong>:<br />

frozen tundra mineral gley, frozen tundra bog<br />

(peat) gley and frozen tundra surface-gley, - is<br />

discussed in the present paper.<br />

The coldgenic soil formati<strong>on</strong> includes the soils, the<br />

profile of which does not rest <strong>on</strong> the permafrost,<br />

:and they have no c<strong>on</strong>tact with the seas<strong>on</strong>al freezing<br />

layer. The presence of cryogenic properties,<br />

horiz<strong>on</strong>s and regimes in these soils Is due to<br />

their lingering and deep seas<strong>on</strong>al freezing the<br />

degree of which depends not <strong>on</strong>ly <strong>on</strong> climatic c<strong>on</strong>diti<strong>on</strong>s<br />

but also <strong>on</strong> granulometric c<strong>on</strong>tent and some<br />

other lactors. According to literature data they are<br />

shown to be in the frozen state not less than 5<br />

m<strong>on</strong>ths. Their mean temperature is positive.<br />

Meliorati<strong>on</strong> of the following soils from the formati<strong>on</strong>:<br />

coldgenic tundra gley <strong>on</strong> the bottoms of<br />

dried-up thermokarst lakes and coldgenic tundra<br />

floodplain, - is discussed in the present paper.<br />

The above-menti<strong>on</strong>ed frozen and coldgenic soils of<br />

the cryolithoz<strong>on</strong>e have the most exhibited complex<br />

of specific features c<strong>on</strong>nected with the frost that<br />

results in specific techniques of their meliorati<strong>on</strong>.<br />

Effective meliorati<strong>on</strong> of the soils with the frost in<br />

the profile is possible under simultaneous c<strong>on</strong>trol<br />

of the two complex processes: frozen and soil<br />

forming, however the task is simplified when the<br />

techniques coinside.<br />

The techniques of c<strong>on</strong>trolling the frozen process in<br />

the soil grounds according to V.A.Kydryavtsev and<br />

E.D.Ershov (1969) are subdivided into €our groups:<br />

a) changing the outer heat exchange; b) c<strong>on</strong>trolling<br />

heat exchange by changing the c<strong>on</strong>tent and<br />

properties of the meliorated thicknesses; c) changing<br />

the temperature regime and heat state of the<br />

1288

meliorated thicknesses by using additi<strong>on</strong>al sources<br />

and runoffs of heat, and d) c<strong>on</strong>trolling temperature<br />

c<strong>on</strong>diti<strong>on</strong>s it1 the rocks deposited lower than the<br />

meliorated thickness. The techniques of c<strong>on</strong>trolling<br />

soil forming process during soil meliorati<strong>on</strong> outside<br />

the cryolithoz<strong>on</strong>e are rather well grounded (Kovda,<br />

1985).<br />

Meliorati<strong>on</strong> of the soils with the frost in the profile<br />

is scientifically based <strong>on</strong> the estimati<strong>on</strong> of the necessary<br />

level of soil heat provisi<strong>on</strong> which can be<br />

energetically evaluated as a part of annual heat<br />

exchange spent <strong>on</strong> heating the soil surface at its<br />

positive temperatures Q o. This part of heat<br />

energy plays the main role in soil formati<strong>on</strong> and<br />

vital activity of organisms. Its increase or decrease<br />

leads to a change both in the soil formati<strong>on</strong> directi<strong>on</strong><br />

and soil bioproducti<strong>on</strong>. Hydrotechnical as well<br />

as n<strong>on</strong>hydrotechnical techniques are used for this<br />

purpose. An artificial change both in heat and<br />

water regimes of the soils provided by all the techniques<br />

results in the increase of soil bioproducti<strong>on</strong>.<br />

Therefore, it is rightfull to speak about hydrotherma;l<br />

meliorati<strong>on</strong>s when these techniques are applied r<br />

in complex. However, in the majority of cases hydrotechnical<br />

meliorati<strong>on</strong>s and am<strong>on</strong>g them -drainage<br />

occupy the leading place.<br />

The n<strong>on</strong>hydrotechnical techniques include<br />

I. Snow meliorati<strong>on</strong>s providing c<strong>on</strong>trol of snow accumulati<strong>on</strong><br />

and snow drive away. The effect of<br />

snow <strong>on</strong> the depth of freezing and thawing is many-<br />

-sided. Due to its high albedo it has a cooling e€fect<br />

and being a thermal insulator in warms the<br />

soil by decreasing efficient irradiati<strong>on</strong>. At a small<br />

thickness of the snow cover it5 cooling effect prevails<br />

over the warming <strong>on</strong>e. Accordingly, complete<br />

snow detenti<strong>on</strong> with the formati<strong>on</strong> of snow drifts<br />

provided due to small field areas, in the forest<br />

z<strong>on</strong>e also preserves soil from str<strong>on</strong>g and deep<br />

cooling and freezing, sharply spring warming up to<br />

a great depth and increases the amount of snow<br />

melting water. After heavy snow winters the snow<br />

drive away is required, it provides a sharp decrease<br />

.of heat spent <strong>on</strong> snow evaporati<strong>on</strong>, an additi<strong>on</strong>al<br />

input of heat into soil and good soil loading<br />

with moisture. In the regi<strong>on</strong> of Vorkuta the snow<br />

drive avay provides the positive heat flow into the<br />

soil by 20-30 days earlier. In the areas with the<br />

near-to-surface ice deposit in the rocks the snow<br />

drive away combined with water drain from the<br />

surface prevents the appearance of thermocarst*<br />

Snow can be removed mechanically or by intensive<br />

thawing. Prol<strong>on</strong>gati<strong>on</strong> of the vegetati<strong>on</strong> period results<br />

in from the snow drive away.<br />

2. Applicati<strong>on</strong> of various covers for soil surfaces<br />

(heat-light- and moisture insulating) is <strong>on</strong>e of the<br />

main comp<strong>on</strong>ents of the thermal soil meliorati<strong>on</strong>.<br />

Coverage with synthetic films decreases the amount<br />

of heat spent <strong>on</strong> evaporati<strong>on</strong> and heat emissi<strong>on</strong><br />

coefficient% detains l<strong>on</strong>g wavelength infrared irradiati<strong>on</strong><br />

and increases heat provisi<strong>on</strong> coefficient of the<br />

seas<strong>on</strong>al-thawing layer. It results in the increase<br />

of heat accumulati<strong>on</strong> in soil (temperature is increased<br />

by 6-8OC) and soil seas<strong>on</strong>al thawing. Effective<br />

irradiati<strong>on</strong> can be decreased by covering<br />

the soil with the film before snowfall, the soil<br />

freezing being delayed by 2-3 weeks. Additi<strong>on</strong>al<br />

thermoinsulati<strong>on</strong> after the snowfall can be provided<br />

with cheap wastes in the form of sawdust, peat,<br />

moss and artificial snow. In Yakutiya foam coverage<br />

gives the positive effect (it increases average tem-<br />

perature of the rocks by<br />

thawing is decrea ed<br />

1.3OC and the depth OP<br />

3-6 times - Gavrilova, 1978).<br />

Covering with an ice-air layer or foam-ice of 35cm<br />

thickness at -20°C, decreases the soil freezing 5<br />

times, i.e. 40 cm instead of 2 m (Merzlotovedeniye,<br />

1981). This group of techniques also includes<br />

colouring the soil surface (blackening, or whitening),<br />

Weakly-moisture-permeable covers (mulch, synthetic<br />

films) decrease the amount of heat spent <strong>on</strong><br />

phase transformati<strong>on</strong> of moisture.<br />

3. The increase of soil roughness by its surface<br />

loosening allows to decrease albedo by 20-30% and<br />

to increase absorpti<strong>on</strong> of short wavelength light<br />

energy, the coefficient of heat c<strong>on</strong>ductance being<br />

c<strong>on</strong>siderably changed as compared with heat capacity.<br />

It probably results in the decrease of soil<br />

temperature. The opposite effect, le. the increase<br />

of the surface layer temperature, can be obtained<br />

by soil packing,<br />

4. Subsoil tillage provides stubble preservati<strong>on</strong> and<br />

in the arable layer it leads to the appearance of<br />

Ithe cavities filled with air which in their turn decrease<br />

heat. emissi<strong>on</strong>.<br />

5. Applicati<strong>on</strong> of row plant growing under row<br />

orientati<strong>on</strong> from the north to the south has a heatting<br />

effect, since the total soil surface is increased<br />

and greater amount of solar energy will be absorbed.<br />

6. Earthing of the frozen bog (peat) gley soils. In<br />

Magadan regi<strong>on</strong> (Korekovtsev, Orlovskaya, 1984)<br />

applicati<strong>on</strong> of 200-300 m3/ha of sand -ice alluvium<br />

provided the increase of the thawing depth at an<br />

average by 4096, +5OG isotherm reached the depth<br />

of 60 cm as compared with 35 cm in the c<strong>on</strong>trol,<br />

7. Rati<strong>on</strong>al forest c<strong>on</strong>cernati<strong>on</strong> and field-protecting<br />

forestry preserve the soil from extreme winter<br />

cooling, decrease inefficient heat expenditures spent<br />

<strong>on</strong> ice thawing and evaporati<strong>on</strong> from soiL Coulisses<br />

of perennial grasses and stubble preservati<strong>on</strong> can<br />

be additi<strong>on</strong>ally used. Culturtechnical practice includes<br />

wood vegetati<strong>on</strong> clearance, hassock cutting<br />

off and st<strong>on</strong>e I.emoving.<br />

8. Placement of agricultural fields <strong>on</strong> downwind,<br />

flat slopes protecting from the north decreases soil<br />

cooling.<br />

9.Applicati<strong>on</strong> of fertilizers including those increasing<br />

cold hardness and frost endurance of plants:<br />

nitrogen <strong>on</strong>es - amm<strong>on</strong>iacal and amm<strong>on</strong>iacal-nitrate<br />

forms; phosphorus <strong>on</strong>es - simple superphosphate,<br />

c<strong>on</strong>taining sulfur; microelement <strong>on</strong>es molybdenum<br />

and nickel forms. In the regi<strong>on</strong>s with cryarid soils<br />

it is necessary to apply microelements, increasing<br />

crop drought-resistance. The soils with high acidity<br />

require liming.<br />

10. Phytomeliorati<strong>on</strong> of soils, For this purpose it is<br />

necessary to select plants and grow new varieties<br />

adapted to the c<strong>on</strong>diti<strong>on</strong>s of the extreme north as<br />

well as to use the productive local grasses <strong>on</strong><br />

pasture and hay lands. Ihe to possible day and<br />

night photosynthesis with the absorpti<strong>on</strong> of not <strong>on</strong>ly<br />

visible but also infrared rays the amount of the<br />

organic matter synthetized under these c<strong>on</strong>diti<strong>on</strong>s<br />

can be compared with that synthetized in a mild<br />

climate.<br />

In the tundra z<strong>on</strong>e the<br />

majority of the techniques<br />

1289

menti<strong>on</strong>ed above can be often used together with<br />

the hydrotechnical meliorati<strong>on</strong>s. Forest c<strong>on</strong>servati<strong>on</strong><br />

and field -protecting forestry are included in<br />

the techniques menti<strong>on</strong>ed above for the z<strong>on</strong>es beginning,<br />

mainly, from forest-tundra <strong>on</strong>e and southward.<br />

The technology of cryolithoz<strong>on</strong>e soil meliorati<strong>on</strong> is<br />

the most specific in the tundra z<strong>on</strong>e and it will be<br />

discussed below, however a number of its elements<br />

can be applied in more southern parts of the cryolithoz<strong>on</strong>e<br />

<strong>on</strong> the soils with the frost in the profile.<br />

This technology has been developed in energy<br />

detail for the groups of soils where drainage plays'a<br />

leading part (Makeev, Vasilevskaya and al., 1981;<br />

Proektirovanie meliorativnykh system na Dal'nem<br />

Vwstoke, 1984). Let us c<strong>on</strong>siger the technology of<br />

the following soils:<br />

1. Frozen tundra mineral gley soils, the profile<br />

of which is resting <strong>on</strong> permafrost with visible ice,<br />

have the depth of seas<strong>on</strong>al thawing of- up to 1.5 m<br />

and the heat provisi<strong>on</strong> of 20.000 kcal/m2 year.<br />

The soils are of loamy, often medium loamy mechanical<br />

c<strong>on</strong>tent characterized by poor water permeability<br />

and frequent thixotropy. Their excessive<br />

water stores are due to underground ice lenses<br />

and overfrost vadose water. They arc situated <strong>on</strong><br />

the slopes of the over-floodplain terraces. Agricultural<br />

development can result in the formati<strong>on</strong> of<br />

thermokarst.<br />

11. Frozen tundra bog (peat) gley soils, the<br />

profile of which is also resting <strong>on</strong> permafrost, have,<br />

however, the depth of seas<strong>on</strong>al thawin<br />

and heat provisi<strong>on</strong> of 15.000 kcaum 8 year. Of 0*4-0,8m The<br />

soils have a peat horiz<strong>on</strong> badly decomposed <strong>on</strong><br />

the top and well decomposed at the bottom. Minerd<br />

ground of various mechanical c<strong>on</strong>tent often thixotropic<br />

underlays this horiz<strong>on</strong>. Excessive water<br />

stores are the same as in the soils of the first<br />

group, but they include gravity supported water<br />

formed during snow melting in the seas<strong>on</strong>al thawing<br />

layer. The soils are situated <strong>on</strong> the depressed<br />

district of the over-floodplain terraces. The threat<br />

of thermokarst is great.<br />

Meliorati<strong>on</strong> of the soils of the 1st and 2nd<br />

groups have to be carried out in two steps. During<br />

the first step (3-4 years) the thawing of the underground<br />

ice is carried out to obtain an even layer<br />

of the seas<strong>on</strong>al thawing, 0.6 and 0.6 m thick in the<br />

1st and 2nd groups, respectively. This aim is<br />

achieved by c<strong>on</strong>structing an open network of canals<br />

being placed at 100-200 m distance from each<br />

other in accord with agricultural needs, Taking into<br />

account possible thermokarst the depth of the canals<br />

should be not less than 1.4-1.6 m. The beginning<br />

of ice melting is provided by sheet preparing,<br />

then as far as the thawing proceeds the repeated<br />

(nqt less than three times during the warm period)<br />

ridging of a thick network off urrous at a depth of<br />

the thawing layer is carried out. The excessive<br />

water is removed from the thermokarst depressi<strong>on</strong>s<br />

which are then planned. It prevents the thermokarst<br />

formati<strong>on</strong> during applicati<strong>on</strong> of soils aEter meliorati<strong>on</strong>.<br />

During the 2nd step a drainage network is<br />

rec<strong>on</strong>structed and an irrigati<strong>on</strong> <strong>on</strong>e is built for<br />

sprinkling. In the soils of the 2nd group 400-500<br />

3<br />

m /mm of mineral ground per ha should be applied<br />

to the arable area.<br />

Building of the roads and hydrotechnical c<strong>on</strong>structi<strong>on</strong>s<br />

is carried out during both the steps. It is<br />

prohibited to remove the soil cover from the routes<br />

inorder to decrease the threat of thermokarst<br />

IIL Coldgenic tundra gley soils of the bottoms<br />

of dried-up thermokarst lakes. <strong>Permafrost</strong> is absent<br />

there but the soils have a tendency towards aggradati<strong>on</strong>.<br />

The depth of the seas<strong>on</strong>al thawing is 1.5 m,<br />

heat provisi<strong>on</strong> 20.000-25.000 kcaum2 year. According<br />

to the mechanical cohtent the soils are loessial<br />

silt clay loam, The bottoms of shallow lakes<br />

have flat slopes.<br />

Meliorati<strong>on</strong> of the soils of the 3d group should be<br />

realized by the c<strong>on</strong>structi<strong>on</strong> of canals for water<br />

discharge from the thermokarst lakes, c<strong>on</strong>trol over<br />

the overgrowth of the lake bottoms with productive<br />

arctic perennial grasses including their undersowing<br />

Arctagrostis broad-leaved, in particular. Liming and<br />

applicati<strong>on</strong> of mineral and organic fertilizers are<br />

required. The yield reaches 30-35 c/of hay per I<br />

ha (Shvirst, 1984).<br />

While operating the drainage systems some measures<br />

should be taken to prevent possible frost aggradati<strong>on</strong><br />

and flooding of the dried-up lakes with<br />

sprin$ floods. After degradati<strong>on</strong> of meadow associati<strong>on</strong>s<br />

it is necessary to flood the lakes and to<br />

begin using the bottoms of other <strong>on</strong>es (grass-fallow<br />

system of landscape rotati<strong>on</strong>).<br />

Iv; Goldgenic tundra floodplain soils. They exhibit<br />

no permafrost, the depth of the seas<strong>on</strong>al thawin$<br />

is 1.5 m, heat provisi n, 25,000-30,000 kcal/m2<br />

year. The majority of these soils except those situated<br />

in the floodplain depressi<strong>on</strong>s has high water<br />

permeability. The soils are systematically flooded<br />

with spring waters and heated with high table<br />

ground waters. This group of soils occupies the<br />

river floodplains. Thermokarst Is absent.<br />

Meliorati<strong>on</strong> of the soils of the 4th group should be<br />

carried out together with flood c<strong>on</strong>trol, preventi<strong>on</strong><br />

of water stagnati<strong>on</strong> and lowering of the ground<br />

wster table. For this purpose a network of canals<br />

is built, depressi<strong>on</strong>s with no runoff are filled with<br />

earth and the surface is levelled. Selected closed<br />

drainage systems may be required. As a result,<br />

50-70 c of high quality fodder per ha is obtained<br />

(Andreev, 1984).<br />

fn the frost regi<strong>on</strong>s of the North the soils destroyed<br />

by excavati<strong>on</strong>s are recultivated and applied<br />

for agricultural need6 (Papernov, Zamoshch, Zakar,<br />

1983). 'The technology preventing the thermokarst<br />

processes is developed. According to it, the total<br />

thickness of the potentially fertile sail, drainage<br />

layer and deposits from silt basins applied to the<br />

recultivated surface must be greater than the depth<br />

of their seas<strong>on</strong>al thawing.<br />

Under c<strong>on</strong>diti<strong>on</strong>s of the East-European tundra in the<br />

regi<strong>on</strong> of Vorkuta according to the method suggested<br />

by the Institute of Biology of the Komi Branch of<br />

the USSR Academy of Sciences the phytomeliorati<strong>on</strong><br />

of the frozen tundra surface-gley soils is successfully<br />

carried out with applicati<strong>on</strong> of relatively<br />

low fertilizer rates. This method c<strong>on</strong>sists of virgin<br />

soil reclamati<strong>on</strong> by discing for cutting the plant cover<br />

and for mixing it with the soiL 'Then local grass<br />

mixtures are sowed and hay-mowing is annually<br />

carried out, The applicati<strong>on</strong> of this method resulted<br />

in the development of about 5.000 ha of the frozen<br />

1290

tundra surface gley in the Vorkuta regi<strong>on</strong>, The hay<br />

harvest of the meadow-foxtail grass mixture and<br />

cane-type canary grass was 15-20 c/ha and up to<br />

100 c/ha, respectively (Zaboeva, Rubtsov, 1985).<br />

CONCLUSION<br />

In the regi<strong>on</strong>s of the Extreme North of the USSR<br />

mainly under c<strong>on</strong>diti<strong>on</strong>s of the perennial cryolithoz<strong>on</strong>e<br />

there are about 6*106 ha of agricultural lands<br />

(Nosov, Vashanov, 1984). Their effective applicati<strong>on</strong><br />

greatly depends <strong>on</strong> meliorati<strong>on</strong>. Hydrotechnicel<br />

and n<strong>on</strong>hydrotechnical techniques of complex meliorati<strong>on</strong><br />

can be applied taking into account the specific<br />

character of soils: cryogenic frozen and coldgenic<br />

<strong>on</strong>es.<br />

The data <strong>on</strong> productivity given above allow to predict<br />

high efficiency but <strong>on</strong>ly in cmse when the quality<br />

of meliorati<strong>on</strong> is drastically increased. Such<br />

negative c<strong>on</strong>sequences of meliorati<strong>on</strong> m6 sec<strong>on</strong>dary<br />

salinizati<strong>on</strong> during excessive irrigati<strong>on</strong>, sec<strong>on</strong>dary<br />

swamping and an increase of the freezing<br />

depth as well as the corresp<strong>on</strong>ding measures<br />

should be c<strong>on</strong>sidered while designing meliorati<strong>on</strong><br />

systems. It is well known that the subarctic soils<br />

&an be greatly destroyed under the anthropogenic<br />

effect therefore special techniques of soil c<strong>on</strong>servati<strong>on</strong><br />

are required.<br />

LITERATURE<br />

Andreev N.G. (1984). Osnovnye napravleniya razvitiya<br />

kormoproizvodshta v rai<strong>on</strong>akh Krainego<br />

Severa. V Knige: Sel'skoe i promyslovoe khozyaistvo<br />

Krainego &vera. Sektsiya pochvovedenie<br />

i agrokhimiya Novosibirsk, Sibirskoe<br />

otdelenie Vseeojuznoi Academii Sel'skokhozyaistvennykh<br />

Nauk (VASKHNIL). str, 64-66,<br />

Gavrilova M.K. (1978). Klimat i mnogoletnee promerzanie<br />

gornykh porod. Kovosibirsk, h'auka,<br />

str. 214.<br />

Zaboeva I.V., Rubtsov M,D, (1985). Zemel'nye resursy<br />

Bol'shezemel'skoi tundry i ikh ispol'sovanie.<br />

- V knige: Problemy pochvennogo criogeneza<br />

Syktyvkar, Komi filial Akademii Nauk<br />

SSSR, str. 6-7.<br />

Kovda V.A. (1985). Pochvennyi pokrov, zemledelie<br />

i melioratsiya Preprint, Pushchino, Nauchnyi<br />

Tsentr Biologicheskikh Issledovanii ( NTsBI)<br />

Akademii Nauk SSSR, str. 25.<br />

Korckovtsev A.S., Orlovskaya K.V. (1984). Vliyanie<br />

tcplovoi melioratsii na svoistva bolotnykh<br />

merzlothykh pochv Magadanskoi oblasti. V<br />

knige: Sel'skoe promyslovoe khozyaistvo Krainego<br />

Severa Eektsja pochvovedenie i agrochimiya,<br />

Novosibirsk, Sibirskoe otdeleniye<br />

VASKHNIL), str.27-29.<br />

Kudryavtsev V.&, Ershov E.D. (1969). Printsipy<br />

upravleniya rnerzlotnym protsessom - V sbornike:<br />

Merzlotnye issledovaniya, vypusk IX,<br />

Moskva, Moskovskii Gosudarstvennyi 'Ciniversitet,<br />

str. 156-157.<br />

Makeev O.V. (1981). Fatsii pochvennogo cryogeneza<br />

i osobennosti organizatsii v nikh pochvennykh<br />

profilei. Moskva, Kauka, str. 88.<br />

Makeev O.V. (1986). Sovremennaya k<strong>on</strong>tseptslya<br />

pochvennogo cryogeneza, evolutsiyya criogennykh<br />

pochv v Golocenr i problemy melioratsii<br />

pochv a merzlotoi v profile. V knige: Evolutaiya<br />

i vozrast pochv SSSR. Pushchino,<br />

NTsBI Akademii Nauk SSSR, str. 37-46.<br />

Makeev O.V., Vasilevakaya .V.D., Volkovintser V.S.,<br />

Elovskaya L.G., Zaboeva LV., Ignatenko LV.,<br />

Kovalev RV., Stepanov A.N., Gershevich V.D.<br />

(1981). Plodorodie i ratsi<strong>on</strong>al'noe iopol'zovanie<br />

pochv Krainego Severa (tundrovaya i lesotundrovaya<br />

z<strong>on</strong>y). - V sbornike: Znachenie<br />

pochvennykh issledovanil v reshenii Prodovol'stvennoi<br />

programmy (doklady General'nogo<br />

simposiuma VI s'eeda Vsesouznogo obshchestva<br />

pochvouedov) , Tbilisi, str. 130-147.<br />

Merzlotovedenie (1981). Moskva, Moskovskii Gosudarstvennyi<br />

Universitet. str. 229.<br />

Nosov SI,, Vashanov V.A. (1984). Osnovnye napravleniya<br />

ratsi<strong>on</strong>el'nogo ispol'zovaniya i okhrany<br />

eemel'nykh resursov Severa V knige: Sell- ,<br />

skoe i promyslovoe khozyaistvo Krainego ,Severa.<br />

Sektsiya pochvovedenie i agrokhimiyer.<br />

Novosibirsk, Sibirskoe otdelenie VASKHNIL,<br />

str. 17-19.<br />

Papernov ZM., Zam<strong>on</strong>hch M.N., Lazar &Ya. (1984)<br />

Osnovnye printsipy, metodika i resul'taty eksperimental'nykh<br />

issledovanii technogeneza i<br />

rekultivatsit usloviyakh Swero-Vostoka.<br />

V acornike: Biologicheskie problemy pochv<br />

sever+ Chast' I, Magadan. str. 293-294.<br />

Proektirovanie meliorativnykh sistem na Dal'nem<br />

Vostoke (1984). Posobie Ministersha vodnogo<br />

khozyaistva SSSR, Vladivostok, str. 8'7.<br />

Shvirst AT. (1984). Isrlsdovaniya PO sozdaniju<br />

senokosov na termokarstovykh p<strong>on</strong>izheniyakh<br />

v subarcticheskoi z<strong>on</strong>e Chukotki, V knige:<br />

Sel'skoe i promyslovoe khozyhisstvo v rai<strong>on</strong>akh<br />

Krainego Sevsra Sektsiya pochvovedenie<br />

i agrokhimiya. Novosibirsk, Sibirskoe otdelenie<br />

VASKHNIL, otr. 10'7-108.<br />

1291

EMBANKMENT FAILURE FROM CREEP OF<br />

PERMAFROST FOUNDATION SOILS<br />

A CASE HISTORY<br />

R. McHattie and D. Esch<br />

Alaska Department of Transportati<strong>on</strong>, <strong>Research</strong> Secti<strong>on</strong>,<br />

Fairbanks, Alaska, USA<br />

SYNOPSIS A roa secti<strong>on</strong> 10.6 meters in height was c<strong>on</strong>structed in 1975 over warm silt permafrost soils near Fairbanks,<br />

Alaska, and was observed to have settled very noticeably after several years of service. Borings were made and<br />

inclinometer and temperature logging casings were installed early in 1983 al<strong>on</strong>g with reference markers for vertical and<br />

lateral movement observati<strong>on</strong>s, Measurements since that time have indicated that creep movements are occurring in the<br />

frozen foundati<strong>on</strong> soils which c<strong>on</strong>tain large massive Ice deposits. Embankment surface settlements have averaged 30 cm<br />

per year since c<strong>on</strong>structi<strong>on</strong>, and measurement points located 9 m outside the embankment toes have been uplifted at a<br />

rate O f 7.5 cm per year. Inclinometer readings have shown that lateral creep movements- of the froten foundati<strong>on</strong> soils<br />

are occurring at depths greater than 13 meters, even though seas<strong>on</strong>al thawing reaches to a depth of <strong>on</strong>ly 6.4 m.<br />

Measurements Indicate the permafrost foundati<strong>on</strong> soil temperatures ,to be very close to -0.4OC.<br />

TO raise and level the roadway in this area to its original height, the embankment was rec<strong>on</strong>structed in 1987 using wood<br />

chips as lightweight fill for replacement of a porti<strong>on</strong> of the embankment s0fl.s. By this means, it was possible to<br />

raise the road surface to Its original elevati<strong>on</strong> while actually reducing the total overburden load <strong>on</strong> the foundati<strong>on</strong><br />

Soils by about 20%. New m<strong>on</strong>itoring equipment has since been installed to m<strong>on</strong>itor the behavior of the rec<strong>on</strong>structed<br />

embankment. Results of all previous m<strong>on</strong>itoring studies are discussed, al<strong>on</strong>g with costs and alternatives c<strong>on</strong>sidered for<br />

repair of this embankment.<br />

described later. The embankment settlements were<br />

BACKGROUND<br />

determined to be caused by plastic creep displacements<br />

In 1975,<br />

of the ice-rich permafrost foundati<strong>on</strong> soils, as<br />

the Alaska Department of Highways completed a<br />

secti<strong>on</strong> of the Parks Highway <strong>on</strong> new alignment across the discussed herein. Creep movements had not previously<br />

been c<strong>on</strong>sidered a problem for roadway embankments.<br />

Al-der Creek valley, approximately 13 km west of<br />

Fairbanks, at latitude 64" 52' North. The valleyrbottom SITE AND SOILS DESCRIPTIONS<br />

soils were perennially frozen, ice-rich silts with<br />

frequent occurrences of massive subsurface ice. Because The Alder Creek valley is a short, U-shaped valley<br />

of c<strong>on</strong>cerns over permafrost thawing and resulting surrounded by low hills. The valley-bottom creek has a<br />

roadway settlements, the 'two shallow cut areas required low flow-rate and is carried beneath the roadway by a 3<br />

at each side of the valley were insulated with m diameter structural steel plate Culvert. The<br />

polystyrene foam and were extensively instrumented and valley-bottom soils were investigated with Several<br />

m<strong>on</strong>itored as reported by Esch (1983). The road auger borings during the roadway design Stage, and found<br />

embankment across the valley bottom had a total length to c<strong>on</strong>sist of gray, slightly organic, perennially froten<br />

of 500 m and varied from 3 to 11 m in helght. To silts with deposits of massive subsurface ice. Moisture<br />

improve the thermal stability, initial road c<strong>on</strong>structi<strong>on</strong> c<strong>on</strong>tents in the silt generally ranged between 25 and<br />

was not permitted until the start of the 1973-74 winter 50%. Extensive moisture c<strong>on</strong>tent and ice occurrence data<br />

freezing seas<strong>on</strong>, and "toe-stabilizati<strong>on</strong>" berms 6 m wide were obtained from the six borings made through the 3 m<br />

by 1.8 m thick were also c<strong>on</strong>structed <strong>on</strong> both sides of thick roadway fill for temperature m<strong>on</strong>itoring cable<br />

the 2:l embankment slopes. installati<strong>on</strong>s at the two nearby insulated embankment<br />

sites (Figure 1). Al six of these instrumentati<strong>on</strong><br />

By 1980, excessive movements of the embankment were borings encountered massive ice, generally at depths<br />

apparent <strong>on</strong> both sides of the valley. In 1982, the between 6 and 14 meters below the new road Surface. One<br />

decisi<strong>on</strong> was made to survey, instrument, and m<strong>on</strong>itor the pre-c<strong>on</strong>structi<strong>on</strong> boring had also been made in 1972<br />

movements in the area of the greatest apparent within 15 m of the maximum settlement area, and<br />

settlements, which by that time had exceeded 2 meters in encountePed <strong>on</strong>ly ice at depths of 2.3 and 6.0.m below<br />

elevati<strong>on</strong> change. Movement reference points, an the original ground surface, with layered and ice silt<br />

inclinometer casing, and a temperature m<strong>on</strong>itoring casing below that depth. From inspecti<strong>on</strong> of these borings One<br />

were installed. Observati<strong>on</strong>s were made several times might c<strong>on</strong>clude that over half of the subsurface "SOilS"<br />

over the following 3 years. Because the maximum in this valley between depths of 3 and 9 m c<strong>on</strong>sisted Of<br />

settlement area had created a vehicle safety hazard due ice masses, with an average ice layer thickness of 3.7<br />

to shortened sight-distances, the roadway was m.<br />

rec<strong>on</strong>structed to its original elevati<strong>on</strong> in 1986 using<br />

wood chips as a lightweight fill-replacement material. Vegetati<strong>on</strong> in the Alder Creek Valley c<strong>on</strong>sists PrimarilY<br />

Sufficient rock-fill was removed from the embankment and of small, stunted, black spruce trees to 5 m in height,<br />

replaced with wood chips so that a significant overall with a ground surface cover of sphagnum moss. The<br />

reducti<strong>on</strong> in embankment weight was achieved, as wil be climate in this area is typical of the dry interior of<br />

1292

HOISTUAE CONTENT (%I<br />

ALDER CREEK UN0,ISTURBEO SITES<br />

0 20 40 80 Bo io0 TEMPERATURE 'C<br />

r r I , I . I , I ~<br />

*<br />

- 9-&"- -o-[r- * ----<br />

r<br />

0<br />

E<br />

6-<br />

0 $<br />

!!I a-<br />

8<br />

13.7m NORTH OF CENTERLINE<br />

B *o"<br />

*<br />

io -<br />

0<br />

0<br />

* O<br />

8<br />

*O<br />

0<br />

0<br />

is -<br />

LEGEND: ICE LAYERS ENCOUNTERED: YEAR<br />

TOP INSULATED CUT 0 STA. 1i02+97 AT 26' LT. FIGURE 2. <strong>Permafrost</strong> temperatures at 9.1 m depth in<br />

0 - BOTTOM INSULATED CUT @ STA. i102t97 AT e<br />

undisturbed forest areas. (six m<strong>on</strong>th running averagesj.<br />

STA. 112it09 AT 24' RT.<br />

I "CLEAR ICE LAYERS 0 STA. i121t09 AT thawing at the toes of the main embankment and to<br />

0 - EXCESSIVE CREEP AREA @ STA* 112i*52 AT provide some added support against rotati<strong>on</strong>al Slope<br />

STA. 1110 8 5TA. 1121+61 AT 24' RT. movements. The wet densities of the rock and silt fi31<br />

a STA. 1109+50 AT C<br />

materials were approximately 2100 and 1750 kg/m ,<br />

respectively. The slopes and. toeberms were seeded and<br />

FIGuRE.1. Subsurface moisture c<strong>on</strong>tents and ice layers the roadway paved in the sumner of 1975 to complete the<br />

in Creek Alder valley borings. original c<strong>on</strong>structi<strong>on</strong>.<br />

Alaska, with short, warm summers and l<strong>on</strong>g, dry winters. INSTRUMENTATION AND MONITORING<br />

freezing and thawlng indices at the Fairbanks airport<br />

recording stati<strong>on</strong> average approximately -3000 and +1800° Soil auger borings were made through both shoulders of<br />

C days, respectively. The mean annual air temperature the embankment in October of 1983, and extended to<br />

is -3.3" C. Precipitati<strong>on</strong> averages 0.28 m/yr, includ- depths of 14.3 and 15.2 m. The borings were made at the<br />

ing the water equivalent of 1.5 m of total snowfall. point<br />

<strong>Permafrost</strong> temperatures typically range between 0" and roadway<br />

of maximum embankment settlement, located near<br />

stati<strong>on</strong> 1110 (<strong>on</strong>e siati<strong>on</strong> = 30.5 m or 100 feet).<br />

-1' C. Two thermocouple and thermtstor strings were The term "roadway stati<strong>on</strong> as used in the text and<br />

installed in nearby undisturbed forest sites in 1975 to flgures of this report indicates the site locati<strong>on</strong> al<strong>on</strong>g<br />

m<strong>on</strong>itor subsurface temperatures away from the influence the roadway centerline as measured from the start of the<br />

of the roadway. Temperatures at a depth of 9.1 m at project (=Stati<strong>on</strong> 0). Both borings indicated that the<br />

these undisturbed sites, which were located approxi- original ground beneath the embankment was still in a<br />

mately 200 m east and west of the area of maximum frozen c<strong>on</strong>diti<strong>on</strong> 10 years after the start of<br />

embankment settlements, are shown by Figure 2. . A c<strong>on</strong>styucti<strong>on</strong>. At this locati<strong>on</strong> and time, roadway<br />

significant (1°C) air temperature warming trend has been surface settlements were in excess of' 2.4 m, yet no<br />

observed in Interior Alaska over the past 11 years, cracking or shear displacements were noted in the<br />

primarily as a result of unusually warm winters. pavement structure, which'was still in excellent c<strong>on</strong>di-<br />

However, the effect of this warming <strong>on</strong> subsurface ti<strong>on</strong>. This fact was the first indicati<strong>on</strong> that plastic<br />

temperatures has small, been flow movements might be occurring in the permafrost<br />

foundati<strong>on</strong> soils.<br />

DESIGN AND CONSTRUCTION OF EMBANKMENTS<br />

An "Inclinometer" casing was installed in the boring<br />

Because of the high subsurface ice c<strong>on</strong>tents, various through the east shoulder of the roadway embankment, and<br />

precauti<strong>on</strong>s were taken to increase the stability of the extended to a depth of 13 meters. The inclinometer<br />

embankment in this area during the original probe is a device which is lowered down a grooved casing<br />

c<strong>on</strong>structi<strong>on</strong>. In preparati<strong>on</strong> for the fill placement, and which indicates the tilt of the casing at selected<br />

all trees and brush were hand-cleared and laid an top of intervals of depth. By taking repeated measurements<br />

the moss cover to avoid any thermal disturbance which over intervals of time,. the change in the lateral<br />

would initiate thawing. The c<strong>on</strong>tractor was then positi<strong>on</strong> of the casing can be measured, and subsurface<br />

required to place an initial 1 m thick layer of movement patterns can be determined. A sec<strong>on</strong>d boring<br />

rock-fill at the start of the 1973-74 winter. This<br />

directly across the roadway, 4.9 m west of the centerinitial<br />

layer was occasi<strong>on</strong>ally cleared of snow during line, was used for installati<strong>on</strong> of a 2.4 cm diameter<br />

the winter to maximize seas<strong>on</strong>al cooling and refreezing plastic pipe which extended to a depth of 13.9 m. The<br />

of the active layer. Comnencing at the start of the Pipe was filled with ethylene glycol and subsequently<br />

1974 thawing seas<strong>on</strong>, the embankment was c<strong>on</strong>structed to used for logging the subsurface temperatures by means of<br />

final grade, 'using weathered schist as the primary fill a thermistor probe.<br />

material. Silt toe berms 6.1 m wide by 1.8 m thick-were<br />

c<strong>on</strong>structed <strong>on</strong> both sides of the embankment to retard<br />

1293

To provide for accurate m<strong>on</strong>itoring of and vertical<br />

SOIL TEMPERATURE ('C)<br />

lateral movements of the embankment and the adjacent<br />

soil surface, a total of 33 movement references were<br />

installed at lateral intervals of approximately 3 m.<br />

-2-1 0 1 2 3 4 5<br />

Pavement surface references were 3 cm-l<strong>on</strong>g survey nails 0-1<br />

driven into the asphalt pavement. Side slope and<br />

adjacent soil movement reference polnts c<strong>on</strong>sisted of 25<br />

cm l<strong>on</strong>g bolts extending up from the centers of 25<br />

-<br />

cm<br />

square aluminum plates which were buried slightly<br />

beneath the soil surface. Movement reference points<br />

were installed in July of 1983 and surveyed at the end 2-<br />

of the thawing seas<strong>on</strong>s in 1984, '85, and '86. Uplifting<br />

of the soil surface outside of embankment the areh was -<br />

observed by installing movement reference plates as far<br />

c<br />

as 9 m out from the toe of the embankment slope into the<br />

lo<br />

undisturbed forest <strong>on</strong> each side of the roadway. b4-<br />

U<br />

Experience has indicated that the m<strong>on</strong>itoring plates<br />

al<br />

should have been extended to at least 20 m outward from E<br />

Y<br />

-<br />

the toe of slope, while the inclinometer casing should<br />

I<br />

have been installed to a much reater depth, perhaps to I-<br />

30 meters or more. The inltia (1975) and final (1986) 86-<br />

embankment cross-secti<strong>on</strong>s are shown by Figure 3 at 0<br />

Stati<strong>on</strong> 1110.<br />

I<br />

LAS-EUILT (1975)<br />

YEARS (1986)<br />

8-<br />

10 -<br />

'<br />

SILT<br />

451 LT. 301 LT. 15n LT. t 15m RT. 30m RT.45n RT.<br />

FIGURE 3. Initial (1975) and 1986 embankment<br />

cross-secti<strong>on</strong>s at Stati<strong>on</strong> 1110 (maximum creep area).<br />

TMPERATURE!<br />

AND MOVEMENT OBSERVATIONS<br />

FIGURE 4. Subsurface temperature-depth profiles<br />

beneath east shoulder of roadway.<br />

Several subsurface temperature profile measurements were<br />

made to determine the maximum depths of freezing and<br />

thawing wlthin embankment. the<br />

These data for 1984 ROADWAY STATION (ft. X 100)<br />

(Figure 4) indicate that the maxfmum freeze and thaw<br />

4 118 i122<br />

de ths were both approximately 5.9 m, and that<br />

emgankment and foundati<strong>on</strong> soils below that depth had<br />

remained frozen. This observati<strong>on</strong> was further c<strong>on</strong>firmed<br />

by the fact that water inside the casing was found to be<br />

frozen at the 5.9 m depth <strong>on</strong> all occasi<strong>on</strong>s when<br />

AS-BUILT &NE 1979<br />

attempting to make inclinometer measurements, Thawing<br />

of the inclinometer casing was required to allow<br />

INSULATION<br />

AT 3.01<br />

lowering the inclinometer probe down the casing.<br />

<strong>Permafrost</strong> foundatl<strong>on</strong> temperatures during 1984 were<br />

found to be approximately -0.2" C at the original ground<br />

surface and -0.4' C at a depth of 4 m.<br />

Elevati<strong>on</strong> surveys of the roadway centerline in the Alder<br />

Creek area were made in 1982 and again in 1985. These<br />

data were used to prepare plots of the centerline<br />

profiles (Fig. 5) and of changes in embankment height<br />

since c<strong>on</strong>structf<strong>on</strong> (Fig. 6). It can be observed from<br />

these plots that excessive embankment settlements were<br />

com<strong>on</strong> throughout this area, partjcularly at locati<strong>on</strong>s<br />

60 to 100 m north and south (right and left respectively<br />

in Figures 5 and 6) of the creek bottom, At these<br />

locati<strong>on</strong>s the embankment heights had been reduced by 18<br />

to 20% by settlements between 1975 and 1982. It is<br />

probable that the valley-bottom permafrost soils were<br />

slightly colder than in the areas slightly up-slope. FIGURE 5. Road centerline elevati<strong>on</strong> profiles in 1975<br />

This may explafn the reduced creep settlements in the and 1985 across Alder Creek valley.<br />

valley-bottom areas. The large 3 m diameter culvert<br />

which carried Alder Creek beneath the road embankment<br />

1294

ROADWAY STATION (ft . X 100)<br />

ALDER CREEK DIP<br />

0.0<br />

1102 1106 1110 1114 Ill0 1122<br />

0.5<br />

rr<br />

v)<br />

L<br />

J 1.0<br />

(u<br />

E<br />

-<br />

+ t.5<br />

5<br />

x<br />

w<br />

F' 2.0<br />

k<br />

W<br />

to<br />

t 2.5<br />

3.0L<br />

INSULATION<br />

FIGURE 6. Settlements al<strong>on</strong>g road centerline across<br />

Alder Creek valley from 1975 to 1985.<br />

was also found to act as an aircooling duct and resulted<br />

in a lowering of temperatures in the soils surrounding<br />

the streambed.<br />

Vertical and lateral movements of the embankment survey<br />

reference polnts are shown by Figure 7. It is apparent<br />

from these plots that the downward movements of the<br />

center of the embankment corresp<strong>on</strong>d to upward and<br />

outward movements in the adjacent undisturbed permafrost<br />

soils beneath the surrounding forest. The roadway<br />

centerline in this area is oriented North, 11" East.<br />

The east facing (or right side) embankment slope would<br />

be expected to be slightly warmer than the opposite<br />

(left) or west facing side. However, except for some<br />

apparent localized thaw-related settlements in the right<br />

side' berm area, the embankment settlements and adjacent<br />

soil uplifting have occurred very symmetrically.<br />

Movements have progressed in nearly equal annual<br />

increments. The seas<strong>on</strong>ality. of the movements and the<br />

movement rates prior to the 1982 surveys have not been<br />

established. However, by comparing the total<br />

settlements since c<strong>on</strong>structi<strong>on</strong> with current rates, it is<br />

apparent that the settlement rate has declined over<br />

time. The 1985 total settlements appear to be the<br />

result of initial vertical movement rates of 0.36 m/year<br />

in 1975 and a reduced rate of 0.25 m/year by 1984.<br />

This decline in rates may be explained at least in part<br />

by the resultant decrease In the total effective<br />

embankment height, from 8.84 m in 1975 to 6.61 m in<br />

1985.<br />

Inclinometer measurements were taken <strong>on</strong> several dates<br />

between October of 1983 and December of 1985. Lateral<br />

movements of the embankment and foundati<strong>on</strong> soils at<br />

different depths are shown' by Figure 8. The pattern of<br />

these movements suggests that the maximum movement z<strong>on</strong>e<br />

is at some depth below the bottom of the casing (13.5<br />

m).<br />

Stresses beneath an embankment <strong>on</strong> an elastic foundati<strong>on</strong><br />

may be estimated by using typical vertical pressure<br />

distributi<strong>on</strong> charts. The initial vertical pressure<br />

increase at the center of the base of the embankment was<br />

calculated to be 220 kPa. The initial resulting<br />

incremental pressure increases al<strong>on</strong>g centerline, at<br />

0.6 L'<br />

FIGURE 7. Vertical and lateral movements of road,<br />

embankment slopes, and adjacent forest structures at<br />

Stati<strong>on</strong> 1110.<br />

depths of 6 and 12 m below the road surface were<br />

calculated to be 211 and 180 kPa, respectively.<br />

However, plastic flow within the permafrost foundati<strong>on</strong><br />

soils, and changes in the geometry of the embankment and<br />

nearby ground surface would cause str4:ses to vary from<br />

those determined for the tnitial elastic" loading<br />

c<strong>on</strong>diti<strong>on</strong>. Further analysis of the compressive and<br />

shear stress states would require finite-element<br />

analyses and is bey<strong>on</strong>d the scope of this report. The<br />

reader is encouraged to apply his own creep analysis<br />

procedures and to test the results against the site data<br />

c<strong>on</strong>tained herein.<br />

I<br />

I<br />

I<br />

1295

introduced into the underlying permafrost soils through<br />

DEFLEC~ION TOWARD EAST (cm) air temperature exposure or through the placement<br />

5 10 warm fill materials. Wood chips were placed in 30 cm<br />

lifts and brought to grade using the com active effort<br />

30m’ LT $dm LT ; ~ SU k~ 30;<br />

provided by the normal trafficking o! dumping and<br />

RT<br />

spreading equipment. Wood chip layer thicknesses were<br />

varied as needed to restore the roadway surface to the<br />

original (1975) elevati<strong>on</strong>s, with a maximum of 5.8 m of<br />

chips placed within the area of greatest settlement.<br />

A total of about 18,600<br />

3<br />

m of wood chips were used to<br />

fill the subexcavated volume. This c<strong>on</strong>structi<strong>on</strong><br />

represented the first placement of such a lightweight<br />

fill in Alaska. Wood types used in the fill included<br />

wood species such as spruce and birch, which are<br />

indigenous to the Fairbanks area. At the start :,f chi;<br />

producti<strong>on</strong>, trees selected for chipping were green<br />

wood but this proved unsat’isfactory since the live<br />

growth did not chip as easily as partSally dried<br />

deadwood, and stockpiles of this green wood material<br />

so<strong>on</strong> had to be ventilated because of heat build-up.<br />

Re-evaluati<strong>on</strong> of the possible wood chip sources resulted<br />

in selecti<strong>on</strong> of relatively dry standing fire-killed<br />

trees from a local 1984 forest fire area. The chips<br />

were produced by a commercial wood chipping machine and<br />

were similar to those -used in decorative landscaping<br />

work. Chips averaged about 2 x 2 x 112 cm in size and<br />

OCT. 20.m3 were purchased at a price in place US $23.60 per of<br />

cubic meter. Producti<strong>on</strong> data indicated that this<br />

material could be produced for a price of $12 to 818 per<br />

FIGURE 8. Lateral soil movements at various depths<br />

cubic meter in future work.<br />

al<strong>on</strong>g vertical inclinometer casing.<br />

After the wood chips and the temporary wintertime<br />

driving surface had been placed in mid-November of 1986,<br />

Repair and rec<strong>on</strong>structi<strong>on</strong> of the embankment was’ found to the fill was allowed<br />

to settle until the resumpti<strong>on</strong><br />

of<br />

be necessary’ by 1985 to restore grades and slghtc<strong>on</strong>structi<strong>on</strong><br />

for the 1987 seas<strong>on</strong>. For estimati<strong>on</strong><br />

distances* In the redesign stages creep movements were pUrpOSeS, a chip post-c<strong>on</strong>structi<strong>on</strong> c<strong>on</strong>solidati<strong>on</strong> factor<br />

c<strong>on</strong>sidered likely to ‘Ontinu@ at the 1985 rate ‘“less of 10% has been suggested by Washingt<strong>on</strong> and Oreg<strong>on</strong> state<br />

the weight Of the embankment Could be reduced Or the highway engineers,<br />

who have wood ,.hips a<br />

temperature of the foundati<strong>on</strong> lowered c<strong>on</strong>siderably. The lightweight fill for swamp crossings. It was found that<br />

potentia’ for ‘ling the permafrost foundati<strong>on</strong> with the wood chip surface had setfled slightly more than 0.3<br />

thermosyph<strong>on</strong>s was re ected based On and the m Over a 6 m<strong>on</strong>th period. C<strong>on</strong>sidering a wood chip fill<br />

decisi<strong>on</strong> as made simp J y to design for a reducti<strong>on</strong> of at<br />

least 10s in the embankment pressure beneath the road Of 5*8 Or less* a Oa3 c<strong>on</strong>solfdati<strong>on</strong><br />

centerline. Settlements in this area <strong>on</strong> both sides of agree with the 10% estimate previously indicated. It is<br />

recognized however that some of the apparent<br />

the creek suggest that the creep movements are roughly c<strong>on</strong>solidati<strong>on</strong> may in fact be c<strong>on</strong>tinuing embankment<br />

proportj<strong>on</strong>al to the embankment pressure.<br />

creep. The final in-place density of the chips was<br />

estimated at 322 kg per cubic meter, and resulted in an<br />

Two alternative fill replacement materials were<br />

c<strong>on</strong>s{dewd. These were molded expanded polystyrene foam Overall embankment pressure reducti<strong>on</strong> Of<br />

6locks. and wood chips, Ec<strong>on</strong>omic comparis<strong>on</strong>s led to<br />

20%.<br />

Of the wood chip and to the The final pavement design analysis over wood the chips<br />

embankment design. In the design analyses the chips<br />

were c<strong>on</strong>servatively assumed to have a maximum wet<br />

was d<strong>on</strong>e based <strong>on</strong> dynamic field falling-weight<br />

deflectometer (FWD) testing and <strong>on</strong> analysis based <strong>on</strong><br />

density of 800 kg/m3, and the desired 10% load reducti<strong>on</strong> elastic theory, A dynamic elastic modulus of 20.7 m Pa<br />

was based <strong>on</strong> this value. The top. 3.3 m of the was calculated for the chip fill layers based <strong>on</strong> the FWD<br />

embankment was scheduled for excavati<strong>on</strong> (average depth) test data and used in the final pavement thickness<br />

and removal prior to the wood chip placement. The chips design analysis. The final pavement structural secti<strong>on</strong><br />

were tapped with a structural layer of gravel and overlying the wood chips included, from top downward, 5<br />

pavement which totaled 1.1 m in thickness; including a 5 cm of asphalt pavement, 15 cm of asphalt treated basic<br />

cm thick hot asphalt pavement surfacing. A thickness of course, 15 cm of crushed g.rave1 subbase, and 76 cm of<br />

1.2 m of fill was provided to cover the sides of the selected schist rock borrow. Lightweight geotextile<br />

wood chip layer to retard air and water entry which layers were placed to separate the rock and gravel<br />

might accelerate decay. borrow layers and to prevent mixing of the<br />

and wood chip layers. The geotextile was added during<br />

RECONSTRUCTION OPERATIONS c<strong>on</strong>structi<strong>on</strong> because mixing problems were<br />

during fill placement over the chips.<br />

Repair of the subsidence area <strong>on</strong> the south side Qf Alder<br />

Creek was undertaken in the late fall of 1986, as part<br />

of the general rehabilitati<strong>on</strong> of a 40 km l<strong>on</strong>g secti<strong>on</strong> of<br />

the Parks Highway. C<strong>on</strong>structi<strong>on</strong> at the slte began in<br />

mid-October, 1986, the removal of the upper 3.3 m of the<br />

existing rock fill over a length of 275 m of roadway<br />

(Stati<strong>on</strong>s 1105 to 1114). The purpose of the late seas<strong>on</strong><br />

c<strong>on</strong>structi<strong>on</strong> was to ensure that minimal heat would be<br />

1296

SUMMARY<br />

Embankment settlements averaging 0.3 m per year have<br />

been observed over a 10 year period for a roadway<br />

embankment orlginally 10.5 m in height. The foundati<strong>on</strong><br />

soils at the site c<strong>on</strong>sist of perennially frozen silts<br />

with massive ice layers. The ice masses are estimated<br />

to exceed 50% of the total subsurface volume below a<br />

depth of 2 to 3 m. <strong>Permafrost</strong> temperatures at this<br />

depth were measured at -0.4'C. Rec<strong>on</strong>structi<strong>on</strong> of the<br />

embankment was d<strong>on</strong>e in 1986 to restore the roadway to<br />

the original elevati<strong>on</strong> after total settlements of 3 m<br />

had occurred.<br />

A wood chlp fill was used In the rec<strong>on</strong>structi<strong>on</strong> to<br />

increase the fill height while lowering the effective<br />

pressure <strong>on</strong> the foundati<strong>on</strong> soils by 20%. The wood chip<br />

layer had a maximum thickness of 5.8 m, and was capped<br />

<strong>on</strong> the top and sfdes by 1.1 and 1,2 m of fill,<br />

respectively. Performance m<strong>on</strong>itoring of the new<br />

embankment wil be d<strong>on</strong>e to record the benefits and<br />

problems of this treatment.<br />

REFERENCES<br />

Esch, D.C. (1983) "Evaluati<strong>on</strong> of Experimental Deslg;<br />

Features for Roadway C<strong>on</strong>structi<strong>on</strong> Over <strong>Permafrost</strong>,<br />

Proceedings, <strong>Permafrost</strong> - Fourth <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>,<br />

pp. 283-288.<br />

1297

CONSTRUCTION OF EARTH STRUCTURES IN PERMAFROST<br />

AREAS BY HYDRAULIC METHODS<br />

P.I. Melnikov, Chang, R.V., G.P. Kuzmin and A.V. Yakovlev<br />

<strong>Permafrost</strong> Institute, Siberian Branch of the USSR Academy of Sciences, Yakutsk, USSR<br />

moPS1s<br />

A PWepeOtiVe teohnology in proposed in the paper of o<strong>on</strong>etruatiag earth<br />

Etl3lOtWee in permafrost me-. Remlts of filL-ecds tests preeented.<br />

Until recent time the eoommio expediency and withdranm *om all the wella <strong>on</strong> a given plot<br />

technical poreibilitiee of c<strong>on</strong>etructing eath and<br />

etrucfrrree (dm, roade, foundati<strong>on</strong>s a d<br />

the ares of- thle plot S I<br />

othesr)<br />

in permafroet meam by a method of draalic<br />

n<br />

degoelti<strong>on</strong> is detemtned by availabi h9 ity of<br />

rrafi.oeen ox thawed k - Vi/S<br />

Iia#r&cr working of%%gkn eartb le usually i-1<br />

carried out from telika below a river bed or a<br />

lake ox from surfacs quarries. Volumes of' Coefficient k may seme aa a criteri<strong>on</strong> for<br />

uaffozen eerth in taliks below the rivere and the technSco-ec<strong>on</strong>omical calculati<strong>on</strong>s.<br />

lakes are, as EL rule, not large. UEI~ of<br />

mxfgca. uasriea ir poseible after a Length<br />

v.<br />

preparetf<strong>on</strong> period em 1.0 ae ter &+en in tKs<br />

Rec<strong>on</strong>mendati<strong>on</strong>s .".(1978, 6-1 5 la<strong>on</strong>ths. Xn<br />

tbis cae c<strong>on</strong>elderable aea~ we withdrawn<br />

from lead-tenure. Beeides, open working may<br />

40<br />

beoeme a aauee of Inteneire fhermokafet<br />

devexopment. All this leads to o<strong>on</strong>sfruofi<strong>on</strong><br />

of eath struetares in permafrost mea by<br />

30<br />

bydk.aatl1~ depoaiti<strong>on</strong> in a very limited number<br />

of cam6 end ia aged mainly for c<strong>on</strong>structi<strong>on</strong><br />

of dame and tailing damp@ according to the<br />

20<br />

data by Kuznetsor et al . ( 1968) and BiyWV<br />

(1975) IO<br />

In thin OOMeCfiOn the Penn&oat Xnetitute Of<br />

the Siberian Branoh of the USSR Academy of<br />

Soiencea prop~~e~i a new feahnology of hydreulia<br />

depositi<strong>on</strong> of earth structuses based <strong>on</strong> 0 40 80 120 160 h,M<br />

underground hydraulic working of the eerth<br />

fxor permdmst through boreholes. Borehole Flg.1 Dependence of the earth volume<br />

hydraulic working ps notable by mall EmQUnt<br />

delivered from <strong>on</strong>e borehole <strong>on</strong><br />

of stripping, simpglicity of equipment used atla<br />

the thicbess of Quaternary<br />

tecbnologlcal flow procese.. StripplPg deposits<br />

permboat ooaeists of is boriM worked.<br />

wells The through borehole8 whioh Witbin<br />

the<br />

Phyaice of the proceae taking place during<br />

the plot being worked are digposed in R ahees- hydraulio working of permafrost come to the<br />

boara order. Dletaaoe between the wells 161 following. Ice cementing b<strong>on</strong>ds of permafrost<br />

determined by the ohhambex dimengi<strong>on</strong>e and<br />

are weakened or completely disturbed as a<br />

interohamber pillare. Tbe volume of earth remI.t of thermal exporure to water.<br />

ob+aiae& *om <strong>on</strong>e chamber depends <strong>on</strong> the Deetruoti<strong>on</strong> of the esrth structural b<strong>on</strong>ds<br />

propertiea and Chioknere of dieperee dqosite after thermal exposure to water ie osaible<br />

whose approximate values are given in Big.1. uith hydreulic nl<strong>on</strong>itor . In tha ome,<br />

men the pecaliaritiea of the borehole depending <strong>on</strong> the water Zeta emperatme and jet<br />

bg&-lj.c working -e c<strong>on</strong>sidered, there should preeewe, earth deatructi<strong>on</strong> takes plme in<br />

be introduced, In OUT opini<strong>on</strong>, 8 yield frbsen c<strong>on</strong>diti<strong>on</strong> at <strong>on</strong>e or another stage of<br />

ooefficient expreeeed by a xatlo of the total ite etrsagth deereaee ox in thawed c<strong>on</strong>diti<strong>on</strong>,<br />

oolums of earth Purely meohdcal deatructi<strong>on</strong> of emairoat<br />

due to ite high momentary strengtf: Fe u~see<br />

high ressure<br />

is shown<br />

2<br />

In a<br />

VI zz by Qofdin et Jets, . (1980). Washout of<br />

i= 1 permdxod with weakened rstructurel is ties<br />

carried out with low pressure water jets<br />

1298

c.---"-\ 5<br />

Fig.3<br />

%eChlloiogieal soheme of borehole<br />

hydraplio working<br />

1,4 - borehole; 2 --cesing pipe; 3 * filler;<br />

5 L. hgdraulio elevator: 6 - rater pipe ; '<br />

7 - pulp 1Sne; 0 - 8 ray=; 9 - wafer;<br />

10 - hose; 11 - ospi $ 7<br />

Fig.2 ,<br />

Scheme of an earth dam hydraulic<br />

depoeiti<strong>on</strong><br />

1 Ulcing stop prima; 2 - borehole;<br />

to<br />

6 - the norki3<br />

underground eavi 9 y boundary; 7 -<br />

column; 4 - water suppl pi e<br />

de ce worki parts3 5 - pu p 1 ne8<br />

divisi<strong>on</strong> boundary between<br />

unfrozen earth.<br />

fYozen and<br />

9 I<br />

!the se uenoe of carrying out preparati<strong>on</strong> work<br />

-a &mulic working prOOe8a ~e ahom <strong>on</strong><br />

Flg.3. !I!he depoeit ia developed as follows.<br />

Biret, a borehole (1) is drilled to the top<br />

boundary of the roduetive layer and then<br />

caeed with pipe 2), the apace bey<strong>on</strong>d the ome<br />

being filled with mud (3) and frozen. Then<br />

a borehole (4) is drilled to the layer bottom,<br />

WepaFatory work is completed by lowering a<br />

hydraulic unit into the borehole (4).<br />

In the hydraulic elevati<strong>on</strong> method of the pulp<br />

supply and jet washout (Big.3) the hyBraulic<br />

instdlati<strong>on</strong> c<strong>on</strong>sists of a supply arrangement<br />

- a hydraulic elevator (5) co-aid water pl e<br />

(6), pulp line (7) and a device for the emti<br />

In a method QS an dr-lift delivem whioh can<br />

combine <strong>on</strong>3 nlth er method of waehbing out of<br />

purmafrasf iy thawing, the hy&rarlie<br />

installati<strong>on</strong> e<strong>on</strong>eiats of a gulp line, an air<br />

eupplg pipe to the lower part of the pulp line<br />

and a water stlpply pi e to the cavity. W&er<br />

Se supplied to the hykaulic inetallatioa *om<br />

natural p<strong>on</strong>ds or from specially built<br />

reservoirs.<br />

Pilot sxperkmente have been emled out <strong>on</strong><br />

plots of siSdlsr type ooarpoeed of fine a d<br />

medium grain BBPBs, of maersive C~YQ~SZCL~:<br />

etructure about 30 rn t4iak with layere 02<br />

ve etatlve remnatm, mupss and mmvel-pebble<br />

maferial. Soile c<strong>on</strong>talo scrub and tree<br />

debria. Tbe volume ric mass of the th<br />

ohangee *om 1.79*103 to 1,94*103 kg/lgraad<br />

moieture varies within 0.19-0.29. Natural<br />

earth temperature at 20 m depth at trro plots<br />

wae anus 2.4 and at two others - minum<br />

1.5 OC. The eeas<strong>on</strong>al than layer reaohed<br />

2.6 m. Them earths ace comparatively easlly<br />

weehed out by a thermal erosi<strong>on</strong> method a d are<br />

Well tsaneporfed by water. Average particle<br />

aize is 0.26 m. Tbe Pall. velocity of these<br />

particles ili &a@& mater, specified by the<br />

hydraulic diameter si!ae, equele 2.7 cm/s.<br />

Thermo-physical epealficati<strong>on</strong>a af eartht<br />

thema1 c<strong>on</strong>duotivitg Sn frozen and uniroaep<br />

state 2.45 and 2.21 W/(m K); heat capwit in<br />

frozen and unffoaen state 1.18 and 1.59 k$/<br />

(k X).<br />

Ky%aulic borehole working waa carried out in<br />

four wells. In three of them jet waahout<br />

1299

1300

STORAGE TANK FOUNDATION DESIGN, PRUDHOE BAY, ALASKA, U.S.A.<br />

B. Nidowicd, D. BruggerG and V. Manikiad<br />

IHarding Laws<strong>on</strong> Associates, Anchorage, Alaska, U.S.A.<br />

ZHarding Laws<strong>on</strong> Associates, San Francisco, CA, U.S.A.<br />

JARCO Alaska, Inc,, Anchorage, Alaska, U.S.A.<br />

SYNOPSIS A Crude Oil Topping Unit (COTU) was c<strong>on</strong>structed in Prudhos Bay, Alaska to<br />

provide aviati<strong>on</strong> fuel, gasoline and diesel to North Slope clients. Recently, ARCO Alaska,<br />

Inc.<br />

redesigned the storage tank farm with the additi<strong>on</strong> of a new 4290 cubic meter welded steel tank and<br />

the relocati<strong>on</strong> of two existing 790 cubic meter tanks. Subsurface soil explorati<strong>on</strong> and laboratory<br />

testing programs were performed to determine the<br />

of two Arctic foundati<strong>on</strong> designs was analyzed using<br />

soil<br />

a<br />

properties at the site. The thermal behavio<br />

two-dimensi<strong>on</strong>al finite element computer<br />

program.<br />

The initial design for support of the 38 degree C crude oil tank c<strong>on</strong>sisted of AISC W24 by 68 beams<br />

spaced <strong>on</strong> 1.2 meter centers in order to provide a 61.0 cm air space between the bottom of the tank<br />

and the top of the gravel pad. The beams were underlain by 22.9 cm of insulati<strong>on</strong>.<br />

\<br />

The initial tank foundati<strong>on</strong> design was revised because of the high coat of structural beams and the<br />

availability of a fin-fan oil cooler in the plant. The final design incorporated the use of the<br />

fin-fan oil cooler to reduce storage tank temperature, and involved founding the tank bottom <strong>on</strong> a<br />

sand cushi<strong>on</strong> underlain by 22.9 cm of insulati<strong>on</strong> placed directly <strong>on</strong> the gravel pad. The temperature<br />

criteri<strong>on</strong> for the storage oil was set at 1.7 degrees C for the winter m<strong>on</strong>ths (November- May),<br />

To c<strong>on</strong>firq this design, additi<strong>on</strong>al thermal modeling was c<strong>on</strong>ducted ueing the new criteri<strong>on</strong>. The<br />

results indicated that the maximum thaw penetrati<strong>on</strong> depth, below the center line of the tank, was<br />

1.3 meters. This depth is above the organic and ice-rich soils. A thaw-settlement of less than 5<br />

cm was predicted, an acceptable c<strong>on</strong>diti<strong>on</strong>.<br />

This paper discusses the alternate design modes investigated and the results of the thermal<br />

analysis.<br />

INTRODUCTION failure in the ice-rich permaf<br />

heated structures are acceptable <strong>on</strong>ly if<br />

The COTU Fuel Storage facility, at Prudhoe Bay, founded <strong>on</strong> a n<strong>on</strong>-frost susceptible fill gad and<br />

Alaska, is located West of the ARC0 Operati<strong>on</strong>s the permafrost integrity is maintained. Pile<br />

center and c<strong>on</strong>sists of ten steel tanks. The foundati<strong>on</strong>s are comm<strong>on</strong>ly used <strong>on</strong> the North<br />

tanks are presently supported <strong>on</strong> gravel pads, Slope, but they are expensive. It is<br />

typically 1.5 meters thick, and are surrounded advantageous to use gravel since it is abundant<br />

by gravel c<strong>on</strong>tainment berms. in the Prudhoe Bay aree.<br />

Due to the increased demand. for product,<br />

additi<strong>on</strong>al tank capacity was needed<br />

at the<br />

facility. ARCO Alaska, Xnc. designed a new<br />

4290 cubic meter tank with a diameter of<br />

approximatcly 24 meters and a height of 9<br />

meters, ARCO also planned to remove two<br />

existing tanka and replace them with two larger<br />

tanks having diameters of 12 meters and heights<br />

of 8 meters. Replacement of the tanks<br />

necessitated removing the existing tanks,<br />

recompacti<strong>on</strong> and placement of additi<strong>on</strong>al fill,<br />

and c<strong>on</strong>structi<strong>on</strong> of the new tanks.<br />

Two significant design c<strong>on</strong>siderati<strong>on</strong>s for<br />

foundati<strong>on</strong>s <strong>on</strong> the North slope of Alaska are<br />

the c<strong>on</strong>tinuous permafrost and the annual<br />

freeze-than cycles of the active layer.<br />

C<strong>on</strong>venti<strong>on</strong>al shallow spread footings do not<br />

perform well because of frost heave from the<br />

active layer and the large potential for creep<br />

The objective of this study was to design a<br />

cost-effective foundati<strong>on</strong> that would preserve<br />

the ice-rich permafrost beneath the tanks<br />

throughout the life of the tanks. To provide<br />

data far use in design, seven borinqa were<br />

drilled and sampled to depths ranging from 5.5<br />

to 8,s meters. Selected samples were tested to<br />

measure their moisture c<strong>on</strong>tent, dry density,<br />

particle size, specific gravity, Atterberg<br />

Limits and freezing point depressi<strong>on</strong>.<br />

PHYSICAL SETTING<br />

The Prudhoe Bay area is located <strong>on</strong> the Arctic<br />

Coastal Plain, a geologic province bounded <strong>on</strong><br />

the north by the Beaufort Sea and <strong>on</strong> the south<br />

by the foothills of the Brooks Range<br />

(Wahrhaftig, 1965). ' Several sea level<br />

fluctuati<strong>on</strong>s due to various glacial epochs hav<br />

occurred al<strong>on</strong>g the Arctic Coastal Plain during

the last 100,000 years, These advances and<br />

retreats of the shoreline have alternatively<br />

flooded and exposed significant porti<strong>on</strong>s of the<br />

North Slope.<br />

The Arctic Coastal Plain is mantled by<br />

unc<strong>on</strong>solidated deposits of the Gubik Formati<strong>on</strong><br />

(Black, 1964) c<strong>on</strong>sisting of lenses and mixtures<br />

of sand, gravel, silt and clay. Though mainly<br />

of marine origin, the Gubik formati<strong>on</strong> has also<br />

been modified by alluvial, lacustrine, eolian<br />

and frost processes.<br />

The principal soil types in the Prudhoe<br />

Bay<br />

area are fluvial sand and gravel deposited by<br />

the Kuparuk-Sagavanirktok River Systems during<br />

the last retreat of the Brooks Range glaciers.<br />

The sand and gravel are overlain by wind-blown<br />

deposits and usually a thin surface mantle of<br />

organic soils and tundra vegetati<strong>on</strong>.<br />

The Prudhoer Bay regi<strong>on</strong> has an arctic coastal<br />

climate. The mean annual air temperature is<br />

-13 degrees C (Walker et al., 1980). Mean<br />

m<strong>on</strong>thly temperatures range from 17 degrees C in<br />

July to -31 degrees C in February.<br />

<strong>Permafrost</strong> underlies the entire Arctic Coastal<br />

Plain. The bottom of the permafrost in the<br />

Prudhoe Bay area is approximately 600 meters<br />

below the surface (Brown and PGwe', 1973).<br />

Thawing during summer m<strong>on</strong>ths usually does not<br />

extend deeper than about 30 cm in undisturbed<br />

tundra areas.<br />

SITE CONDITIONS<br />

Test borings show that most of the tank site<br />

area is covered by gravel fill of varying<br />

thickness. <strong>Research</strong> of published geologic maps<br />

and aerial photographs indicates that the<br />

surf ce c<strong>on</strong>diti<strong>on</strong>s beneath the gravel<br />

fill<br />

c<strong>on</strong>silst of a gently undulating ground surface<br />

supporting typical tundra vegetati<strong>on</strong> of<br />

grasses, sedges, mosses, and low shrubs. The<br />

general area is characterized by poor surface<br />

drainage, many low marshy areas and shallow<br />

wind oriented lakes up to several hundred<br />

acres. The site lies at an elevati<strong>on</strong> of about<br />

9 to 12 meters above mean sea level.<br />

Based <strong>on</strong> the test borings, it was determined<br />

that the three tank sites have similar soil<br />

profiles. In general, sandy gravel fill,<br />

approximately 1.5 meters thick, was found to<br />

overlie ice-rich, n<strong>on</strong>plastic sandy silt and<br />

silty sand to depths of 4 to 6 meters. Beneath<br />

these soils, sand and gravel extend to the<br />

depths explored. Massive ice, in the form of<br />

ice lenses and wedges, was comm<strong>on</strong>ly encountered<br />

within the ice-rich soil.<br />

The fill typically c<strong>on</strong>tains 31 to 64 percent<br />

gravel. 31 to 56 percent sand, and 5 to 12<br />

,percent silt. The moisture c<strong>on</strong>tent of the fill<br />

averages about 8 percent. According to the<br />

Unified Soil Classificati<strong>on</strong> System, the fill is<br />

classified as GP-GM or SP-SM. This fill is<br />

representative of Prudhoe Bay area gravel.<br />

The ice-rich soil had moisture c<strong>on</strong>tents that<br />

varied between 30 and 350 percent. with an<br />

average of about 140 percent. The coarsegrained<br />

sand and gravel underlying these soils<br />

was ice-poor. and had moisture c<strong>on</strong>tents ranging<br />

between 11 and 36 percent.<br />

The freezing point<br />

depressi<strong>on</strong> of the samples tested varied between<br />

-0.1 c to -0-4 c.<br />

DESCRIPTION OF COMPUTER CODE<br />

Computer Code FROSTPB (CRREL, 1984) was used to<br />

model the thermal regime beneath the heated<br />

fuel tanka. FROST2B is a two-dimensi<strong>on</strong>al<br />

computer code that uses a nodal domain<br />

integrati<strong>on</strong>.mode1 of heat and soil-water flow<br />

coupled through isothermal soil-water phase<br />

change. The program can be used<br />

to analyze<br />

two-dimensi<strong>on</strong>al freezinp/thawing problems where<br />

known informati<strong>on</strong> is sufficient to supply the<br />

necessary modeling parameters, boundary<br />

c<strong>on</strong>diti<strong>on</strong>s, and initial c<strong>on</strong>diti<strong>on</strong>s. The key<br />

assumpti<strong>on</strong>s used In the thermal analysis of the<br />

program are:<br />

1. Heat transport in freezing soils<br />

occurs due to c<strong>on</strong>ductive and c<strong>on</strong>vective<br />

processes and follows the general equati<strong>on</strong><br />

of heat transfer in solids and liquids.<br />

Additi<strong>on</strong>ally, the heat transport equati<strong>on</strong><br />

is n<strong>on</strong>linear, as the thermal c<strong>on</strong>ductivity<br />

and heat capacity of the soil-water-airice<br />

mixture is a functi<strong>on</strong> of ice and water<br />

c<strong>on</strong>tent in a freezing and thawing soil, A<br />

volumetric fracti<strong>on</strong> proporti<strong>on</strong> equati<strong>on</strong> is<br />

used to describe the thermal c<strong>on</strong>ductivity<br />

and heat capacity of soil-watar-air-icemixture<br />

as a functi<strong>on</strong> of the volumetric<br />

c<strong>on</strong>tent of each composing c<strong>on</strong>stituent.<br />

2. Soil-water phase change is assumed to<br />

occur isothermally in a partially<br />

saturated soil element. The phase change<br />

model'that couples the heat and soil-water<br />

transport models is based <strong>on</strong> the apparent<br />

specific heat capacity model whereby the<br />

latent heat effects of freezing water are<br />

lumped into the transient heat capacity<br />

term of the heat transport equati<strong>on</strong>.<br />

3. Unfrozen z<strong>on</strong>es are n<strong>on</strong>deformable, and<br />

in freezing z<strong>on</strong>es or frozen Z<strong>on</strong>es,<br />

deformati<strong>on</strong> is due to ice segregati<strong>on</strong> or<br />

lens thawing <strong>on</strong>ly.<br />

4. C<strong>on</strong>stant parameters, such as<br />

porosity, remain c<strong>on</strong>stant with respect to<br />

time: i.e.. freeze-than cydles do not<br />

modify parameters.<br />

5. Hysteresis effects are napligible.<br />

6. Saline exclusi<strong>on</strong> processes are<br />

negligible,<br />

7. Freczina and thawing processes in a<br />

two-dimer s:i<strong>on</strong>.-.- medium occur suck that<br />

there are no internal shear or stress<br />

forces developed between different z<strong>on</strong>es.<br />

DESCRIPTION OF THE BASIC MODEL<br />

The model selected c<strong>on</strong>sists of a 2.4-meter-high<br />

supporting gravel pad with 2 horiz<strong>on</strong>tal: 1<br />

vertical (28:lV) side slopes. The gad is<br />

underlain with a 30.5-cm-thick organic layer<br />

overlying about 4.6 meters of ice-rich soil<br />

overburden. The mechanical and thermal<br />

properties of the soils the model c<strong>on</strong>sists of -<br />

were obtained from the laboratory tests and<br />

1302

proprietary data obtained <strong>on</strong> similar Prudhoe<br />

Bay area soil types. The soil properties used<br />

in the analysis are presented in Table I. In<br />

all but two simulati<strong>on</strong>s, a layer of insulati<strong>on</strong>,<br />

either 15.2 or 22.9 cm in thickness, was<br />

located 30.5 cm beneath the gravel gad surface.<br />

Approximate Time of Year<br />

Measured Ground Surface<br />

Temperature<br />

,< <strong>on</strong> a Gravel Pad<br />

TABLE I.<br />

Soil Properties<br />

Embankment<br />

Property Gravel Organic Overburden<br />

-"<br />

Denrlty (kg/m3), id 1,922 801 1.458<br />

Porosity, 8, 0.3 0.7 0.45<br />

Initial Volumetric Ice C<strong>on</strong>tent 0.099 0.699 0.449<br />

Thermal C<strong>on</strong>ductivlty, K<br />

(W/d 5.23 2.91 2.09<br />

Volurmtric Heat Capacity, C<br />

(J/kg-K) 2.89 1.55 1.55<br />

Freezing Point of Water, OC 0. 0. 0.<br />

Salinity. PPT 0. 0. 0.<br />

Thaw Strain (%) 3 30 30<br />

Elapsed Time (t), Days<br />

- NOTES :<br />

1. Average Air Temperature, T(l), obtained from nineyear<br />

temperature record at Prudhoe Bay, Alaska.<br />

T(1) = 18.9 sin 360 21T It-117) -12<br />

2. Average ground surface temperature, T(2), includes<br />

estimated effects of splar radiati<strong>on</strong>.<br />

T(') * 18.9 sin $& (t-117) -6.5<br />

Mean m<strong>on</strong>thly air temperatures were obtained for<br />

a 9-year period (1970-1978) for the ARC0 Air<br />

Field at Prudhoe Bay, Alaska (Walker et al.,<br />

1980). Figure 1 shows the best fit sinusoidal<br />

curve to these data. Since ground surface<br />

temperatures are required, the air temperatures<br />

must be modified. To modify the air<br />

temperatures, the energy exchange at the<br />

surface must be calculated. This requires<br />

knowledge of several mechanisms including: 1)<br />

c<strong>on</strong>ducti<strong>on</strong> through snow cover, if it exists, 2)<br />

solar (short wave) radiati<strong>on</strong>, 3) l<strong>on</strong>g wave<br />

radiati<strong>on</strong>, 4) evapotranspirati<strong>on</strong>, and 5)<br />

c<strong>on</strong>vecti<strong>on</strong> to the atmosphere (Lunardini, 1981<br />

and Miller, 1975). Unfortunately, sufficient<br />

data were not available to allow for the<br />

development of the heat transfer coefficients<br />

required to calculate the ground surface<br />

temperatures,<br />

To estimate the ground surface temperatures,<br />

actual surfac! temperatures were obtained<br />

(Figure 1) and a sinusoidal ground surface<br />

temperature curve was developed from the data,<br />

Although a c<strong>on</strong>stant correcti<strong>on</strong> was applied<br />

throughout the year, it is recognized that the<br />

difference between the air and ground curves is<br />

not a c<strong>on</strong>stant (Auld, et al., 1978 and<br />

Lunardini, 5978).<br />

The initial temperatures used at various<br />

locati<strong>on</strong>s within the model are discussed next.<br />

Initial internal tank temperatures were fixed<br />

at either 37.8 degrees C or 54.4 degfees C.<br />

Outside the perimeter of the tank, the ground<br />

surface temperature curve, T(2), was used.<br />

Fig. 1 Air and Ground Temperatures<br />

Initial pad surface temperatures beneath the<br />

tank were varied as follows:<br />

1. Fixed at either 37.8 degrees C o\r<br />

54.4 degrees C.<br />

2. Allowed to equal the average air<br />

temperature, T (l), defined <strong>on</strong> Figure 1.<br />

3. Fixed at either 37.8 degrees C OL<br />

54.4 degrees C for the m<strong>on</strong>ths of November<br />

,through May and. allowed to equal the<br />

average air temperature for the m<strong>on</strong>ths of<br />

June through October.<br />

4, Computed by the model assuming a tank<br />

floor temperature of 54.4 degrees C.<br />

5. Fixed at 1-.7 degxees C or 4.4 degrees<br />

C €or the m<strong>on</strong>ths of Mid-September through<br />

mid-May and allowed to equal. the average<br />

air temperature plus 8.3 degrees C for<br />

mid-lag through mid-September.<br />

Because the pad surface beneath the tank is<br />

shaded from the effects of solar radiati<strong>on</strong>, the<br />

air temperatures were used instead of the<br />

ground temperatures. A fixed-temperature<br />

boundary c<strong>on</strong>diti<strong>on</strong> of -10 degrees C was assumed<br />

at the bottom of the model. This temperature<br />

approximates the equilibrium permafrost<br />

temperature <strong>on</strong> the North Slope (Brown and Phd,<br />

1973).<br />

1303

ANALYSIS AND RESULTS<br />

Using the different thermal criteria previously<br />

discussed, thirteen computer simulati<strong>on</strong>s were<br />

performed. Ten o€ the simulati<strong>on</strong>s madeled a<br />

tank supported <strong>on</strong> a raised beam foundati<strong>on</strong>.<br />

The remaining three simulati<strong>on</strong>s modeled the<br />

tank <strong>on</strong> an <strong>on</strong>-grade foundati<strong>on</strong>. The<br />

simulati<strong>on</strong>s were performed for a design life of<br />

20 years. A summary of the results is<br />

presented in Table 11. All references to pad<br />

surface in this discussi<strong>on</strong> refer to the area<br />

directly beneath the tank. The major findings<br />

3f the simulati<strong>on</strong> are as follows:<br />

1. For all cases analyzed. the locati<strong>on</strong><br />

of the thaw fr<strong>on</strong>t stabilizes between 1 and<br />

5 years.<br />

2. Using the c<strong>on</strong>servative assumpti<strong>on</strong><br />

that the pad surface temperature equals<br />

the tank floor temperature (-31.8 or 54.4<br />

degrees C ), we found that the thaw fr<strong>on</strong>t<br />

penetrates the ice-rich soil below the<br />

fill with or without insulati<strong>on</strong>.<br />

3. When the pad surface temperature is<br />

set equal to the ambient air temperature<br />

and no insulati<strong>on</strong> is used (simulati<strong>on</strong>. 41,<br />

the thaw fr<strong>on</strong>t penetrates through the<br />

gravel ped, but equilibrates at the top of<br />

the ice-rich organic layer. If 15.2 cm of<br />

insulati<strong>on</strong> is<br />

placed in the gravel pad<br />

(simulati<strong>on</strong> 6), the thaw fr<strong>on</strong>t remains<br />

within the insulati<strong>on</strong>.<br />

4. The thaw fr<strong>on</strong>t is limited to a<br />

maximum depth of approximately 50.0 cm<br />

below the insulati<strong>on</strong> for a beam foundati<strong>on</strong><br />

underlain by 15.2 cm oi insulati<strong>on</strong> when<br />

the computer program is allowed tp determine<br />

the pad temperatures (Simulati<strong>on</strong> 1).<br />

5. For an <strong>on</strong>-grade foundati<strong>on</strong> and when<br />

the pad temperature is varied during the<br />

summer and winter m<strong>on</strong>ths (Simulati<strong>on</strong>s 11,<br />

12, and 13). the thaw fr<strong>on</strong>t can be<br />

maintained within about 1,2 meters below<br />

the bottom of the insulati<strong>on</strong>.<br />

6. Extending the insulati<strong>on</strong> 61 cm bey<strong>on</strong>d<br />

the tank perimeter is not sufficient to<br />

prevent deep thawing of the outer pad<br />

area.<br />

FOUNDATION DESIGN<br />

Using the results of the thermal analysis, we<br />

selected two foundati<strong>on</strong> systems. One system is<br />

to found the tanks <strong>on</strong> a 15.2-cm-thick timber<br />

deck that is supported <strong>on</strong> AISC W24 by 68 beams<br />

spaced <strong>on</strong> 1.2-meter centers as shown <strong>on</strong> Figure<br />

2. This foundati<strong>on</strong> system will result in a<br />

61.0-cm air space between the bottom of the<br />

tank and the top of the gravel pad. Located<br />

beneath the tank is 15.2 cm of insulati<strong>on</strong><br />

placed 30.5 cm below the top of the gravel pad<br />

surface.<br />

\<br />

TABLE 11.<br />

Computer Slmulati<strong>on</strong> Results<br />

Computer<br />

Slmulatl<strong>on</strong><br />

Number<br />

Insulatl<strong>on</strong><br />

Thickness<br />

, c m<br />

Inltlal Gravel Pad<br />

Surface (Beneath Tank)<br />

Temperature "C<br />

Foundatl<strong>on</strong><br />

Type<br />

Maximum Depth of Thaw<br />

at Tank Center, Meters<br />

One Year Flve Years<br />

Thaw Settlcment<br />

At Tank Center, cm<br />

On@ Year Five Years<br />

1<br />

2<br />

3<br />

4<br />

5<br />

6<br />

7<br />

8<br />

9<br />

10<br />

11<br />

12<br />

13<br />

15.2<br />

N<strong>on</strong>e<br />

15.2<br />

N<strong>on</strong>e<br />

15.2<br />

15.2<br />

15.2<br />

22.9<br />

22.9<br />

15.2<br />

15.2<br />

15.2<br />

22.9<br />

Detemlned by Computer<br />

54.4<br />

54.4<br />

Amblent Air<br />

373<br />

Ambient Alr<br />

Ambient Air: June-Oct<br />

37.8: Nov-May<br />

37.8<br />

hblcnt Air: June-Oct<br />

37.8: Nov-May<br />

Ambient Afr: June-Oct<br />

54.4: NOV-MU<br />

4.4: Mid Sept.-Mfd May<br />

kbient Air tE.3:<br />

Mld Maydld Sept.<br />

4.4: Mid Sept.-Mid May<br />

Pmbient Air t8.3:<br />

Mid Hay-Mld Sept.<br />

4.4: Mid Sept.-Mid May<br />

Ambient Air t8.3:<br />

Mid May-Mid Sept.<br />

Beam<br />

Beam<br />

Beam<br />

Beam<br />

Beam<br />

Beam<br />

Beam<br />

Beam<br />

Beam<br />

Beam<br />

Grade<br />

Grade<br />

Grade<br />

0.9 0.9<br />

4.5 5.5<br />

7.9 4.3<br />

2.1 2.5<br />

2.2 3.5<br />

0.3 0.3<br />

0.9 2.6<br />

1.4 2.0<br />

0.3 0.3<br />

0.9 1.7<br />

0.9 1.4<br />

0.8 1.2<br />

0.6 1.1<br />

2-4 2.4<br />

67,l 97.5<br />

15.2 67.1<br />

6.4 7.6<br />

6.4 45.7<br />

1.2 1.2<br />

2.4 1.5.2<br />

3.1 22,9<br />

1.2 1.2<br />

2.4 5.2<br />

2.4 4.3<br />

2.4 3.7<br />

1.8 3.4<br />

1304

0 ! 2 3<br />

SCALE : METERS<br />

TIMBER DECK<br />

15.2 cm<br />

TANK F11<br />

from June through October and 37.8 degrees C<br />

from November through May. The results<br />

indicated that these warmer temperatures wauld<br />

cause a substantial depth of thaw. Using 22.9<br />

cm of insulati<strong>on</strong> and. the same temperatures<br />

(Simulati<strong>on</strong> 9), the thaw fr<strong>on</strong>t stabilizes<br />

within the insulati<strong>on</strong> ashown in Figure 8 .<br />

2.1. rn 1.5m<br />

L. 3.8 m ! 3-4 rn 1 ! I, TANK RADIUS, R512.2 rn 7<br />

TUNDRA SURFACE ELEV 9.B m -,<br />

DETAIL<br />

NOT TO SCALE<br />

"I""" _"<br />

Fig. 2<br />

W24x88, 1.2 rn 0 .c.<br />

T<br />

30.5 em<br />

::15.2 ern<br />

81.0 crn<br />

Steel Beam Support Design<br />

CLASSIFIED<br />

FILL<br />

INSULATION<br />

CLASSIFIED<br />

FILL<br />

EXISTING<br />

FILL<br />

The results of the thermal simulati<strong>on</strong> for this<br />

design (Simulati<strong>on</strong> 1) are shown <strong>on</strong> Figure 3.<br />

To keep the area beneath the tank perimeter<br />

frozen, the design (Figure 2 ) shows 1.5 meters<br />

of insulati<strong>on</strong> extending outward from the tank.<br />

, 3.8 rn , 3.4 rn , 1 , 1,<br />

1 , I<br />

Ulllll<br />

OVERBURDEN<br />

2.1 m 1.5m<br />

TANK RADIUS. R-12.2 rn<br />

Assumpti<strong>on</strong>s:<br />

Insulati<strong>on</strong> thickness = 15.2 cm<br />

No airflow beneath tank: tank floor temperaturp * 54.4'i<br />

pad surface temperture beneath tank was detemlned by the<br />

computer model.<br />

-4<br />

Ulllll ". 6<br />

-4<br />

Assumpti<strong>on</strong>s:<br />

Insulati<strong>on</strong> thickness = 22.9 cm<br />

' Pad surface temperature beneath tank equals ambient air temperature<br />

June through October and 37.B'C November through May<br />

Fig. 4<br />

Results of Therrfial Analysis for Steel<br />

Beam Design (Shulati<strong>on</strong> 9)<br />

Thaother system of foundati<strong>on</strong> support is to<br />

place the tank directly <strong>on</strong> the gat3 surface, as<br />

shown <strong>on</strong> Figure 5. Insulati<strong>on</strong> is located 30.5<br />

cm below the gravel gad surface. To prevent a<br />

Large thaw bulb from .developing beneath the<br />

tank, the fluid in the tank must be chilled to<br />

at least 4.4 degrees C from mid-September<br />

through mid-May, and modified to equal the<br />

0 1 p g<br />

SCALE : METERS<br />

EXISTIN<br />

SEE DETAIL1<br />

r;<br />

ELEV 11.8 m<br />

TUNDRA SURFACE ELEV 9.0 rn ,<br />

I<br />

DETAIL<br />

NOT TO SCALE<br />

-1 4<br />

Y)<br />

t<br />

-13 w<br />

Ly<br />

.1 2, I<br />

z'<br />

.I 1 0<br />

5<br />

Fig. 3<br />

Results of Thermal Analysis far Steel<br />

Beam Design (Simulati<strong>on</strong> 1)<br />

Since snow buildup, i.e. drifting, may impede<br />

air flow beneath the tank during the winter<br />

m<strong>on</strong>ths. the effects of warmer temperatures were<br />

investigated. In Simulati<strong>on</strong> 7. the pad<br />

temperatures were changed to equal ambient air<br />

"-"-"I<br />

Fig. 5 Pad Support Design<br />

I<br />

EXISTING<br />

FILL<br />

1305

outside ambient air temperature plus 8.3<br />

degrees C from mid-May through mid-September.<br />

This will be accomplished by adding a cooling<br />

system to the tank inflow lines.<br />

The results of the computer analysis indicated<br />

that 15.2 cm of insulati<strong>on</strong> (Simulati<strong>on</strong>s 11 and<br />

12) would provide satisfactory designs.<br />

However, due to the relatively low cost of the<br />

additi<strong>on</strong>al insulati<strong>on</strong>, it was decided to use<br />

22.9 cm of insulati<strong>on</strong> as an additi<strong>on</strong>al factor<br />

of safety.<br />

The results of the thermal analysis performed<br />

<strong>on</strong> this design (Simulati<strong>on</strong> 13) are shown <strong>on</strong><br />

Figure 6. Like the beam design, to keep the<br />

outer area frozen, the design (Figure 5) shows<br />

the insulati<strong>on</strong> extending 1.5 meters outward<br />

from the tank.<br />

61.0 cm<br />

3.8 m .3.5 m 2.8 m. TANK RADIUS, ~ ~ 1 2 m . 2<br />

." I<br />

30.5 cm<br />

I ORQANIC<br />

OVERBURDEN<br />

Assumpti<strong>on</strong>s:<br />

* Insulati<strong>on</strong> thickness -22.9 cm<br />

Pad surface temperature equals 4.1OCfor days 0 to140.and260ta360<br />

and is equal to ambient air temperature plus f1.3~Cfrorn days140to<br />

260 during any given year.<br />

Fig. 6 ,Results of Thermal Analysis for Pad<br />

Support Design (Simulati<strong>on</strong> 13)<br />

DESIGN CONSIDERATIONS<br />

To prevent frost heave, the gravel pad was<br />

c<strong>on</strong>structed of classified fill c<strong>on</strong>sisting of<br />

sand and gravel c<strong>on</strong>taining less that 5 percent<br />

by weight passing the No. 200 sieve size. The<br />

fill was compacted to a minimum of 95 percent<br />

maximum dry density as determined by the ASTM<br />

Method D 1557 laboratory test procedure.<br />

The insulati<strong>on</strong> was installed <strong>on</strong> a smooth, level<br />

bearing surface with the joints staggered and<br />

overlapped to prevent cold leaks, and extended<br />

a minimum of 1.5 meters in all directi<strong>on</strong>s<br />

bey<strong>on</strong>d the tank perimeter, FOAMGLAS celLular<br />

glass insulati<strong>on</strong>, as manufactured by Pittsburgh<br />

Corning Corporati<strong>on</strong>, was used. Although the<br />

thermal properties of this insulati<strong>on</strong> are not<br />

as good as fiberglass, it was selected for its<br />

l<strong>on</strong>g-term stability. Specifically, it does not<br />

break down when immersed in oil. An<br />

impermeable barrier, resistant 3 degradati<strong>on</strong><br />

from petroleum products, was placed <strong>on</strong> top of<br />

the insulati<strong>on</strong> for protecti<strong>on</strong> against fuel<br />

spills.<br />

t<br />

CONCLUSIONS<br />

Warm fuel storage tanks can be c<strong>on</strong>structed <strong>on</strong><br />

the Alaskan North Slope using the design c<strong>on</strong>cepts<br />

presented within this paper. Depending<br />

up<strong>on</strong> the fluid temperatures and pad thickness,<br />

the tank can either be placed directly <strong>on</strong> the<br />

gravel pad or elevated. Instrumentati<strong>on</strong> should<br />

be installed at the time of c<strong>on</strong>structi<strong>on</strong> to<br />

allow for c<strong>on</strong>tinual m<strong>on</strong>itoring of ground<br />

temperatures and settlements.<br />

ACKNOWLEDGEMENTS<br />

The permissi<strong>on</strong> of the COW Owners to publish<br />

this gaper is gratefully acknowledged.<br />

Appreciati<strong>on</strong> is extended to ANVIL Corporati<strong>on</strong>,<br />

project c<strong>on</strong>sulting engineers.<br />

REFERENCES<br />

Auld. et al. 1978. Pad foundati<strong>on</strong> design and<br />

performance of surface facilities in the<br />

Mackenzio Delta. Proceedings of the Third<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>.<br />

Val, 1, pp, 165-771.<br />

Black, R.P. 1964. The Prudhoe Bay Field.<br />

Proceedings of the geological seminar <strong>on</strong><br />

the North Slope of Alaska. pp. LI-LII.<br />

Brown,' R.3.E. and T. L. Piwe. 19" 1.<br />

Distributi<strong>on</strong> of permafrost in North<br />

America and its relati<strong>on</strong>ship to the<br />

envir<strong>on</strong>ment: a review, 1963-1973.<br />

<strong>Permafrost</strong>,<br />

Sec<strong>on</strong>d <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, North American C<strong>on</strong>tributi<strong>on</strong>.<br />

CRREL. 1984, FROST2B - A Nodal Domain<br />

Integrati<strong>on</strong> Model of Two-Dimensi<strong>on</strong>al Heat<br />

and Soil-Water Flow Coupled by Soil-Water<br />

Phase Change. Hanover: Cold Regi<strong>on</strong>s<br />

<strong>Research</strong> and Engineering Laboratory.<br />

Lunardini, V.J. 1981. Heat Transfer in Cold<br />

, Climates. V<strong>on</strong> Nostrand Reinhold Co., New<br />

York.<br />

Lunardini, V.Y. 1978. Theory of N-factors and<br />

correlati<strong>on</strong> of data. Proceedings of the<br />

Third <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong><br />

<strong>Permafrost</strong>. Vol. 1, pp. 40-46.<br />

Miller, T.W. 1975. The surface heat balance in<br />

simulati<strong>on</strong>s of permafrost behavior. ASME<br />

paper 75-WA/HT-66, November.<br />

WahrhaFtig, C. 1965. Physiographic divisi<strong>on</strong>s<br />

of Alaska: a classificati<strong>on</strong> and brief<br />

descripti<strong>on</strong> with discussi<strong>on</strong> of high<br />

latitude physiographic processes. USGS<br />

Professi<strong>on</strong>al Paper 482.<br />

Walker. D.A., et al. 1980. Geobotanical Atlas<br />

of the Prudhoe Bay Regi<strong>on</strong>, Alaska. Report<br />

80-14. Hanoves: Cold Regi<strong>on</strong>s <strong>Research</strong><br />

and Engineering Laboratory.<br />

1306

STUDIES OF PIPELINE INTERACTION WITH HEAVING SOILS<br />

S.Yu. Parmuzinl, A.D. Perelmiter2 and Lye. Naidenokz<br />

1Faculty of Geology, Moscow State University<br />

2AII-Uni<strong>on</strong> <strong>Research</strong> Institute for C<strong>on</strong>structi<strong>on</strong> of Major Pipelines, Moscow, USSR<br />

BYNOPaS<br />

Vertical displacements of underground pipelines due to n<strong>on</strong>unirorm heaving of<br />

freeslng aoils give rise to additi<strong>on</strong>al stresses in the pipe W81LS. The intensity of displacement<br />

in each BpecYic cross-secti<strong>on</strong> of a pipeline depende not <strong>on</strong>ly <strong>on</strong> the magnitude of soil<br />

heaving at the barse, but also ob the Operati<strong>on</strong> of the 'pipeline - soil system, and can be detenained<br />

from the equilibrium Of forces that favor or resist pipe displacement. TPbese forces are<br />

expressed as functi<strong>on</strong>s of the "effective" depth of soil freezing equal. to the difference of depths<br />

at ihich pipe displacement be h a and ends. Three principal cases have been c<strong>on</strong>sidered, In the<br />

first caBe freezing occura <strong>on</strong>fy fmm the soil ~ufpace, in the sec<strong>on</strong>d - <strong>on</strong>ly from the pipe surface,<br />

and in the third - soil is freezing simultaneously from the soil surface and fmm the pipe walls.<br />

For these ca8es a technique has been developed for calculating a pipeline displacement in djfferant<br />

cross-seod<strong>on</strong>s al<strong>on</strong>g itits length at any moment of time starting from the beginning of soil<br />

freeoing, The correctness of this method hae been cocroborated by Laboratom experimente <strong>on</strong> modele<br />

and by comparis<strong>on</strong> with field data.<br />

Vertical. displacemanta of underground pipellnet3 (3) the pipeline lies unfrozen soil that;<br />

due to heaving of fpeeeing soile give rise to<br />

experiences freezing both from the soil<br />

c<strong>on</strong>siderable stresses ixl the pipe walls. The<br />

surface ana pipe walls.<br />

magnitude of these stressea depends <strong>on</strong> variati<strong>on</strong>s<br />

in soil heaving al<strong>on</strong>g the pipelfne.Hence In the firs+ ai these cases, there is no pipeatrangth<br />

calculati<strong>on</strong>s require knowledgg of line displacement until the freezbg fr<strong>on</strong>t has<br />

the magnitude of possible pipelae displacement reached the upper pipe generatrix. When the<br />

in each specific ~ross-~ectl<strong>on</strong>.<br />

freeebg fr<strong>on</strong>t has reached the upper pipe generatrix,<br />

the Boil begins to freeze together with<br />

Analytical'determinatf<strong>on</strong> of pipelhe displace- the pipeline surface. The layer of frozen soil<br />

ment due to its in.teracti<strong>on</strong> with frost-suscep- that has become attached to the pips may drag<br />

tible soils presents a complex problem which the pipelha with it; when it is displaced p-<br />

has not yet been aolved in exact formulati<strong>on</strong>. wards under the acti<strong>on</strong> of relative normal : om#<br />

This paper 'suggests an approximate engineering of frost heaving P, (Fig.1a). This can occur<br />

soluti<strong>on</strong> of displacement problem based <strong>on</strong> calculatiom<br />

of "effective1' of depth freezing soil a 0<br />

c<strong>on</strong>trolled by the difference of freezhg deptha<br />

where pipelbe displacement begins and ends.<br />

Pipeline difiFlaCement begins at mch a depth<br />

of freezing layear for which the forces favordiapla,cemeht<br />

exceed those resisting the moti<strong>on</strong>.<br />

Motl<strong>on</strong> will terminate either when the freezing<br />

process ends or when the forces resistbng displacement<br />

exceed those causing that displacement,<br />

Depending <strong>on</strong> the tempepature regime of the pipeline<br />

aad surrounding soil,. three basic cas=<br />

of interacti<strong>on</strong> axe possible:<br />

(1) the pipeline lies within the layer of<br />

eeaa<strong>on</strong>allg freezing soil and its tempe- .<br />

rature is little different from the<br />

temperature of the host soil;<br />

.. . .. .<br />

(2) the pipeline lies in unfrozen soil and<br />

it6 temperature is below zero at least<br />

durlng Some porti<strong>on</strong> of the year. Soil<br />

freezhng occurs from the pipe suxface<br />

and, depending <strong>on</strong> pipeline temperature, agram of forces that act<br />

seas<strong>on</strong>al or l<strong>on</strong>g-term freezing haloes <strong>on</strong> the pipeline<br />

form;

when the resultant %t of specific freezingtogether<br />

forces (Pft>, applied to the pipelbe<br />

surface in the freezing-together z<strong>on</strong>e, exceeds<br />

the total weight of the pipeline with the<br />

transported item q the weight of unfrozen<br />

P'<br />

soil above the pipe in the pockets and the<br />

shear strength of the unfrozen sod (qeh) at<br />

the segment from the pipe half-diameter to the<br />

bottom of the frozen soil, as well 8s forces<br />

of soil adhesiveness at the lower pipelbe generatriz<br />

9,. If the adhesi<strong>on</strong> forcea are greater<br />

than the rupture strength of uafrozen soil<br />

(qr), then the pipeline displacement occura<br />

together with the soil that has stuck to the<br />

pipe and the value of qr is taken into account<br />

Fn the calculati<strong>on</strong>s. Apart from the loa& menti<strong>on</strong>ed<br />

above <strong>on</strong>e should include the Inteneitg<br />

of vertical ioad (4) in 8 cross-secti<strong>on</strong> due to<br />

the adjoining pipeline segments.<br />

Up to the time when the depth of soil freeob$<br />

has reached the depth of pipeline axis ( ),<br />

!e<br />

the c<strong>on</strong>diti<strong>on</strong> for displacement to begin ia '<br />

written in the form<br />

Here q1 is equal to the smaller of two values,<br />

q, and 9,. The resultant of specifio freezing<br />

forces is determined as has been ShQWn by<br />

Perelmiter et al. (1 $811, from<br />

where<br />

+ P& De sinJ3<br />

p = cos-' 2 3 L L ; ,<br />

De<br />

is a coeff lcient of proport O<strong>on</strong>ality having<br />

0<br />

the dimensi<strong>on</strong> MFa . deg" ; Pft denotea specifie<br />

forces of freezing together at O'C; De is<br />

the external pipe diameter3 tmin is the mean<br />

m<strong>on</strong>thly temperature of soil. surface during the<br />

coldeat m<strong>on</strong>th; Tw is the durati<strong>on</strong> of the<br />

winter period, rt is the time from the beginniag<br />

of freezing to the beginning of displacement;<br />

9 is the depth of frozen layer at<br />

time T .<br />

Formula (2) is derived <strong>on</strong> the assumpti<strong>on</strong>e that<br />

temperature changes linearly with depth the<br />

temperature change at the soil surface during<br />

whter time is described by a harm<strong>on</strong>ic functi<strong>on</strong>,<br />

and the specific forces of freezing depend<br />

linearly <strong>on</strong> soil temperature.<br />

The quantities qa, g,, and qSh are, determined<br />

Prom the following relati<strong>on</strong>e (Perelmiter et al.,<br />

1981) I<br />

(3)<br />

et<br />

I* = s; De 1<br />

(41<br />

where Pa denotes specific forces of adhesi<strong>on</strong><br />

between unfrozen soil and pipeline; 6, et is<br />

the limlting l<strong>on</strong>g-term strength of unfrozm<br />

soil for tensi<strong>on</strong>; g is the accelerati<strong>on</strong> due to<br />

gravity; p soil density above the pipe; ys<br />

is the angle of Internal fricti<strong>on</strong> for unfmmn<br />

soil; C the adhesive force of unfrozen soil.<br />

The valuea of adhesi<strong>on</strong> an l<strong>on</strong>g-term ~trength<br />

of &mzm soil are given Irr a number of publicati<strong>on</strong>s<br />

(Vetrov and K<strong>on</strong>dra 1 2; Rekomen-<br />

datsii ... , 1983; Simta, IbOThe forces<br />

sft and qBh, as can be seen ia (2) and (5) are<br />

the functioas of time (r and of freezing<br />

depth 9. howing the dependence of % <strong>on</strong> C ,<br />

<strong>on</strong>e om find from (I) the time when the pipeline<br />

began to aove and the minimum depth of<br />

freezing ( hpmm ) a% which that moti<strong>on</strong> will<br />

begin. Subsequently, the pipeline and the<br />

surrounding soil move together. Pipeline moti<strong>on</strong><br />

terminates <strong>on</strong> reaching the maximum of soil<br />

freezing (hpmax). The difference batween<br />

and la equal to the "effect,Ive*i thickness<br />

which cauaes pipeline moti<strong>on</strong> ( A ) in the<br />

C~SS-8eCtiOIl c<strong>on</strong>sidered.<br />

A = ( -<br />

Kh (6)<br />

where kh is the coefficient of soil heaving<br />

equal to the ratio of heavlng amount at the<br />

free surface of soil to the maximum freezing<br />

depth; it is determined experimentally.<br />

If calculati<strong>on</strong> by (1) shows *ha$ tpelbe<br />

moti<strong>on</strong> doea not occur before the xeezing fr<strong>on</strong>t<br />

has reached the depth of pipeline axia, <strong>on</strong>e<br />

should examine the equilibrium of forces for<br />

De @ig.lb).<br />

klp s 9 G 5 + 0.5<br />

In that case noma1 forces of heaving s, which<br />

begin to act directly <strong>on</strong> the p$pe are added to<br />

the loads that cause the moti<strong>on</strong>. The forces<br />

that resist moti<strong>on</strong> decrease, because qah = 0.<br />

The c<strong>on</strong>ditioi for equilibrium of forces that<br />

act <strong>on</strong> the pipeline is writiten in the form<br />

I I I<br />

q$t+s,-s,-9p29"0. (7 1<br />

Normal heaving forces under this c<strong>on</strong>ditf<strong>on</strong> are<br />

determbed from<br />

(8)<br />

The coefficient of proporti<strong>on</strong>ality K is<br />

0.6 MN/m3 for soils of medium heaving capacity<br />

1308

.<br />

and 1.0 W/m3 for those of str<strong>on</strong>g heavlng capac<br />

itg (Kisely, 1971 1.<br />

The foice q ft ia determined from (2) when<br />

p+. ,<br />

I<br />

The forces 4 a and 9, are determined from<br />

fable 1<br />

Experimental data and calculated displacement<br />

of experimental tubes<br />

~~ ~<br />

Experimental data<br />

. . ~~~~<br />

. .-<br />

Calculated valuea<br />

snow<br />

anow<br />

E6 25 25.3 173 94.5<br />

17 24 24.2 158 06<br />

9 . 23 23.2 145 79<br />

The magnitude of dis$laaenent is found, as in<br />

the precediag cam, from (7) bowing + as a<br />

Puuati<strong>on</strong> of t.<br />

AS f reeoing pTOCead8, when hp % + 0.5 De,<br />

the pipeline is acted <strong>on</strong> by .%, g~, and q, <strong>on</strong>lg.<br />

TM .dqu~lib,rium of force; 1s written an<br />

a,-ap.t.s=O- 1 (11)<br />

The quantity % is for this case fohd from<br />

= 0.107 K 6 + K De % ('1 2)<br />

where $ le the thickness of frozen a011 under<br />

the lower pipe generatr&.<br />

&a ,experbuent waa carried out to test the method<br />

for oalculating the thickness of the layer a%<br />

which diaplacement be ins. Three I-m lag<br />

steel pipe Begmente zf, 17 and 9 om w diameter<br />

and a wall thiheas 0) 0.6 uu were puk h<br />

the Prosen z<strong>on</strong>e at a depth of 22 cm fmm the<br />

wper generatrix to the soil surface, The SOU<br />

at; the testing site waa rapresentea by silty<br />

loam and had the following characterist CBI<br />

weight humidity 23% P =0.00146 Irg/cm3,<br />

ul, = 15*, C = 0.614 ma. Groundwater table<br />

was at B depth of 30 - 60 cm prior to freesing.<br />

Such soils are classified as str<strong>on</strong>gly frostsusceptible.<br />

To shield the sealed butt ends of<br />

pipee from the acti<strong>on</strong> of heaving forces whan<br />

soil was frozen <strong>on</strong> to the ends, theee were iaeulated<br />

with two layers of pol ethylene. The<br />

freesing depth was determined %y frost-depth<br />

meters of the Danilin system. Observati<strong>on</strong>s of<br />

ptpe moti<strong>on</strong> were ma&. by the geodetic method.<br />

Experbental investigati<strong>on</strong>s have shown that<br />

vertical pipeline moti<strong>on</strong> began in all the three<br />

Cases much earlier than the time when the frost<br />

depth<br />

thiclmess<br />

reached<br />

of froeen<br />

the pipe<br />

soil axiamhThe at minbimum which the<br />

moti<strong>on</strong> of test pipes began In the experiment,<br />

the comparis<strong>on</strong> with the calculated valuea<br />

$Ts , as well aa the calculated the fmm the<br />

beginnbg of freesing until the beginning of<br />

moti<strong>on</strong> ae am given in Table 1.<br />

!<br />

The presence of snow does not affect the value<br />

Of $E), as waa to be expected, but just<br />

ases the time from the beginnixlg of freeuntil<br />

the beghlng of moti<strong>on</strong>.<br />

The opefatian of pipeline8 with a negative ferneratuxe<br />

put into unfmeen soil is accompanied<br />

% y the formati<strong>on</strong> of fro& haloes around them.<br />

Al<strong>on</strong>g .the perimeter of this halo heaving forcab<br />

arlae that have the directi<strong>on</strong> al<strong>on</strong> the normal<br />

to the suFface of freezing (Fig.lo$. The active<br />

part of relative nomal heaving forces Pp,<br />

causing pipeline displacement, is situated<br />

al<strong>on</strong>g the lower semicircle of the cglindrleaL<br />

freezing surface. The heavin forces developing<br />

<strong>on</strong> the upper semicircle o$ the Prosen cg-<br />

Ihder are counterbalanced by the overlying<br />

unfromn SOU when there is no ireeaing of soil<br />

from the t3uTface, and hence are equal to the<br />

wei ht of that soil acting <strong>on</strong> the frosen cg-<br />

1hL.<br />

Pipeline moti<strong>on</strong> ie in that case revented by:<br />

the total weight of the pipe wit% the transported<br />

item and soil frozen an to it (gprs) the<br />

resistance of unfrozen soil above the pipe(@,<br />

aa well as fhe force of fricti<strong>on</strong> afr) of<br />

frozen soil around the pipe with the nurroundiag<br />

dmzen soil due to the fact that the<br />

horiz<strong>on</strong>tal comp<strong>on</strong>ent of f roat-haaviag forces<br />

gives Pise to compacti<strong>on</strong> ("wedging-outs1) of the<br />

surrounding ImProzen soil. It is also neCgsaary<br />

to include the force (4) due to the influence<br />

of the adjoining parts of the pipeline.<br />

The vertical comp<strong>on</strong>ent of fricti<strong>on</strong> force causing<br />

pipe moti<strong>on</strong> is determined by<br />

where Dfs is the diameter of soil frozen <strong>on</strong><br />

to the pipe.<br />

The quantity Pn, which depends <strong>on</strong> the compositi<strong>on</strong>,<br />

texture end properties of the soil, <strong>on</strong><br />

freezing c<strong>on</strong>diti<strong>on</strong>s etc., varies within a wide<br />

range and ie determined experimentally ,whereas<br />

$Pa and q:<br />

are determbed from<br />

1309<br />

1

The force arising from the fricti<strong>on</strong> between<br />

the frozen soil around the pipe and the unfrozen<br />

soil is detembed as the sum of fricti<strong>on</strong><br />

forces arising fmm the horiz<strong>on</strong>tal comp<strong>on</strong>ents<br />

of frost-heavhg forces acting <strong>on</strong> the lmer<br />

and upper semicircles of the frozen cylinder.<br />

The force of fricti<strong>on</strong> is determined from the<br />

following formula (Perelmiter and Pamuzin,<br />

1981):<br />

From the equati<strong>on</strong><br />

4 -'%fa - qi - Ffr 2 4 = 0 (17)<br />

<strong>on</strong>e can fhd the minimum value of $:, and<br />

BO the thickness of soil frozen <strong>on</strong> to the pipe<br />

at which pipeline moti<strong>on</strong> begins. Heavbg will<br />

termbats slmultaneously with Ereezhg; the<br />

diameter of the frozen cylinder wLl1 then be<br />

equal to I$: .<br />

The value of effective frozen-layer thfclmess<br />

c<strong>on</strong>trolling pipeline moti<strong>on</strong> In the momsecti<strong>on</strong><br />

c<strong>on</strong>sidered is equal to<br />

The ma itude of displacement can then be<br />

found Rom (6).<br />

A number of experimenta have bean made <strong>on</strong> the<br />

model. to substantiate the proposed model for<br />

the Snteraclti<strong>on</strong> between the pipeline &d the<br />

frost-susceptible soils that are freezing from<br />

the pipe wall and to determine pipe moti<strong>on</strong> a8<br />

a functi<strong>on</strong> of frost-halo thickless (heavhg<br />

coefficient) . A .pipe of diameter 7.6 cm and<br />

wall thickness 0.5 cm was put into a metal box<br />

4.05~1.5~1.6 m in size that had be filled<br />

with heavy loam (p = 0.00202 kg/&. The<br />

distance fmm the soil surFace to the upper<br />

generatrix of the pipe was 12 cm. The pipe<br />

ends were either clamped in hinges or remalned<br />

free in different; erhents. Cold air of<br />

temperature dO°C,%oCt and -20°C wa8 pumped<br />

into the model pipe. Soil freezbg from the<br />

pipe walls took place under the c<strong>on</strong>diti<strong>on</strong>s of<br />

a free system, i.e., water flow occurred from<br />

below. Water level 3n the device was at a<br />

depth 28-32 cm. Soil humidity varied with*<br />

the range 23 to 27 percant. So51 temperature<br />

wa8 measured with resistance thennometem cI.8.t~ped<br />

rigidly relative $0 the pipe; vertical<br />

pipe moti<strong>on</strong> was determhed 8% eight pohljs<br />

al<strong>on</strong>g the length, Measures were taken to prevent<br />

displacement sensors Prom being frozen to<br />

the frost-halo Soil. Ffg.2 shows experimental<br />

rewlts for the case of unclamped pipe ends.<br />

It can be 88811 that the rate of Oreezbg ai@-<br />

PicantLy affects the magnitude of ptpe displacement.<br />

In all cases, the ma itude of displa-<br />

CemehIj is a Linear functi<strong>on</strong> opthe fmzen<br />

layer depth above the pipe. Hinge clampfn of<br />

the .ends diminishes displacement at the mi8dY.e<br />

of the pipe. Itl that ,case, the heavbg coefficient<br />

varied within 0.14 to 0.21 for differat<br />

freezing rates .<br />

""II<br />

I<br />

3u 1<br />

"1<br />

Pig.2 Dynamics of vertical displaoement of the pipe (A) and<br />

freezing halo thickness below it ( f ) at -6OoC, -N0C and -20°C<br />

(curves with Roman figures I, I1 and 111, reepectivelyj<br />

I - pipe displacement; 2 - change in the depth of freezing below<br />

the pipe up<strong>on</strong> the beginning of upward moti<strong>on</strong> (5 1; 3 - total<br />

depth of freezing below the pipe,<br />

'#<br />

1310

Slusarchuk et al. (1978) described experfmental<br />

investigati<strong>on</strong>s into the moti<strong>on</strong> of 12 m-1-<br />

and 1220 nun in diameter pipe secti<strong>on</strong>s when a<br />

fmst-susceptible sol1 was freezing fmm the<br />

pipe. The heaving coefficient of pipe secti<strong>on</strong>s<br />

was 0.205-0.215, Le. it was close to the values<br />

obtained by us in model studies.<br />

When soil is freesing ajmultaneously from the<br />

surface and from the pipe walls ($ig.ld), the<br />

first thing that occurs is compacti<strong>on</strong> of a<br />

layer of unfmzen soil undes the bottom of the<br />

layer of seas<strong>on</strong>al freezing. The resp<strong>on</strong>se of<br />

that Payer SignWicantly diminishes and (when<br />

It reaches a cerbin thiclmess) completsLy<br />

stops pipelhe heaving until the time when the<br />

soil that in behg frozen from the suTface<br />

comes in c<strong>on</strong>tact wifh the frozen soil around<br />

the pipe. AFter that, when the aoil 28 being<br />

furtiher frozen from the sureace, the pipeline<br />

will begin to move.<br />

Thua the method proposed here can predict the<br />

poasibflity ma magnitude of displacement of<br />

undergmund pipellnes when these interact with<br />

frost-susceptible soils. The relevant formulas<br />

involve the main characteristics of the state<br />

and properties of soils that c<strong>on</strong>trol the intensity<br />

of pipe moti<strong>on</strong> in a specific cross-secti<strong>on</strong><br />

al<strong>on</strong>g the length of" the pipeline. One of the<br />

tasks facing future studies is to omduct natural-size<br />

experbents in feat areas in order<br />

to detemhe the coefficients of soil heaving<br />

fox different pipe diameters the effect of.<br />

the moti<strong>on</strong> of pfpel,$ne clamp& in the soil,<br />

and the load due to the areas adjacent to the<br />

pipeline cross-secti<strong>on</strong> under c<strong>on</strong>siderati<strong>on</strong>.<br />

REFFXENCEFj<br />

Vetrov, Yu.A. & K<strong>on</strong>dra, A.S.(1972). Rezultaty<br />

Issledovaniya lipkosti gruntov. Sb. : Gornye,<br />

stmitelnye i dorozhnye ma8hiny.Vyp.<br />

14, pp.12-18. Kiev.<br />

Kiselev, M,F, (19'71). Meropriyatiya protiv deformatsii<br />

zdaniy i sooxuaheniy ot deistviya<br />

si1 moroznogo vypuchivan'lya fundamentov,<br />

102 pp. Moskva: Izdatelstvo Literatux8<br />

PO stmitelsfvu,<br />

Perelmiter, A.D. & Pamuzin, S.Yu. (1980).<br />

Vzaimodeiatvie truboprovodov a puchinistymi<br />

gruntami. Gb.nauchnykh trudov<br />

m.IIS!Ct R<strong>on</strong>struktsii, metody rascheta gasoprovodov<br />

i sposoby stroitelatva,<br />

pp.57-68. Moakva.<br />

Perelmiter ADD. , PamuzFn, S,Yu. Alekseyev<br />

8.1. Spirid<strong>on</strong>ov , V.V. (19811. Opredelenie<br />

peremeshcheniy i nagruzokl deistvuyushchikh<br />

na truboprovod v puchlnistykh<br />

grwtakh. Nauchno-tekhuicheskig referativny<br />

sbornlk: Sroektirovanie i stroiteiatvo<br />

truboprovodov i gazopromyslovykh<br />

sooruzhenig. Vyp.4, pp.26-33. MoslNa.<br />

Bokomendatsii PO opredeleniuy lipkosti gruntov<br />

v statsi<strong>on</strong>arnykh laboratornykh i polevykh<br />

usloviyakh. (19831, 31 pp. Moskva:<br />

St ro iiadat.<br />

Strota Yu.L. (1980). Issledovaniya prochnosti<br />

giinistogo grunta pri rastgazhenii.<br />

Nauchno-tekhnichesky referativng sbornLklk:<br />

Stmitelstvo i arkhitektura, Seriyya 15:<br />

Inehenarnye ieyskaniya v stroitelstve.<br />

Vyp.4. Otechestvenny opgt, pp.5-9.Moskva.<br />

8lusarchuk, B.A., Clark, J.1, Nlz<strong>on</strong>, J.E.<br />

Morgenstern, R.B. & Gaskin P.N.(19783.<br />

Field test results of a chhlea pipeline<br />

buriea in unfrozen gmund. Proc.3rd @t.<br />

C<strong>on</strong>fr. <strong>on</strong> Permarrost , v.1, 877-8B4, .<br />

Edm<strong>on</strong>t<strong>on</strong>, Canaaa.<br />

131 1

YUKON RIVER BANK STABILIZATION: A CASE STUDY<br />

C.H. Riddle, J.W. Ro<strong>on</strong>ey and S.R. Btedthauer<br />

B&M C<strong>on</strong>sultants, Inc., Anchorage, Alaska 99503 USA<br />

SYNOPSIS: Erosi<strong>on</strong> <strong>on</strong> the right bank of the Yuk<strong>on</strong> River above the Galena Airfield is caused by a<br />

combinati<strong>on</strong> of thermo-erosi<strong>on</strong>al niching of the frozen upper bank, causing massive block failure<br />

and erosi<strong>on</strong> of the failed material by river currents and natural thalweg migrati<strong>on</strong>. The average<br />

annual erosi<strong>on</strong> rate is relatively uniform throughout the '8 km l<strong>on</strong>g bend upstream of Galena,<br />

ran ing from 4-6 m per year. Subsurface investigati<strong>on</strong>s and geotechnical evaluati<strong>on</strong> identified<br />

soif c<strong>on</strong>diti<strong>on</strong>s. the extent of massive ground ice and other geotechnical parameters necessary €or<br />

design and c<strong>on</strong>structi<strong>on</strong> of bank protecti<strong>on</strong>. To limit c<strong>on</strong>tinued erosi<strong>on</strong> of the upper bank by<br />

thermo-qrosi<strong>on</strong>al niching, alternative design c<strong>on</strong>cepts were prepared, each reflecting the different<br />

geotechnical and h draulic c<strong>on</strong>diti<strong>on</strong>s al<strong>on</strong>g the study reach. A c<strong>on</strong>venti<strong>on</strong>al rock revetment was<br />

recommended for tze more stable soil secti<strong>on</strong>. An insulated, rock protected revetment<br />

was<br />

suggested as an alternative for those areas found to have ice-rich soil and high thaw strain<br />

potential.<br />

INTRODUCTION<br />

4.5-7.5 m of frozen silt c<strong>on</strong>taining massive<br />

ice. In all cases, these materiaxs overlie a<br />

Galena, Alaska is located <strong>on</strong> the north bank typically of frozen sand and gravelly sand<br />

an 11 km l<strong>on</strong>g meander of the Yuk<strong>on</strong> River about deposit. This underlying granular material<br />

435 km west of Fairbanks (Fig. 1). The town appears to be thaw stable, where frozen,<br />

of Galena was established around 1919 as a<br />

representing a suitable foundati<strong>on</strong> <strong>on</strong> which to<br />

supply base for galena prospecrs in the<br />

place some form of embankment for upper bank<br />

vicinity. The Civil Aet<strong>on</strong>autics Adminis-<br />

slope protecti<strong>on</strong>.<br />

trati<strong>on</strong> c<strong>on</strong>structed an airfield at Galena in<br />

late 1941 and the airfield was occupied by the C<strong>on</strong>structi<strong>on</strong> of l<strong>on</strong>gitudinal segments of bank<br />

military so<strong>on</strong> after. Although the site was<br />

protecti<strong>on</strong> was felt to be the most practical<br />

known for periodic flooding, the military felt method of completing any significant porti<strong>on</strong><br />

the Galena airfield could best fill their<br />

of this project due to budget restricti<strong>on</strong>s. A<br />

emergencv needs at that time. Following an<br />

656 m l<strong>on</strong>g secti<strong>on</strong> (identified as Phase I <strong>on</strong><br />

ice jam- flood in 1971, which flooded the<br />

Fi . 1) , extending upstream from the sheet<br />

original townsite and nearly overtopped the pi'ie hardpoint, was c<strong>on</strong>structed during the<br />

flood c<strong>on</strong>trol dike around the airfield, much winter and spring of 1986. An additi<strong>on</strong>al 328<br />

of the civilian populati<strong>on</strong> relocated to a new m l<strong>on</strong>g secti<strong>on</strong> (identified as Phase XI<strong>on</strong> Fig.<br />

townsite about 2.5 km upstream of the runway. 1) located in fr<strong>on</strong>t of the new town site is<br />

The new townsite is also in the path of the currently being completed by the Corps.<br />

migrating meander.<br />

Since establishment of the airfield, several<br />

.studies and projects have been completed by<br />

the U.S. Army Corps of Engineers (Corps) in<br />

efforts to c<strong>on</strong>trol erosi<strong>on</strong> in this area.<br />

Specific features within the project study<br />

area are shown in Fig. 1. Most of these<br />

acti<strong>on</strong>s have c<strong>on</strong>centrated <strong>on</strong> protecting the<br />

airfield. In 1984 the exiting sheet pile hard<br />

point was in danger of being flanked due to<br />

erosi<strong>on</strong> upstream of the piles.<br />

Erosi<strong>on</strong> at the old town site is primarily by<br />

wave attack of the upper bank, averaging<br />

1.4-1.8 m per year. From the old town to<br />

slightly upstream of the Galena Airfield<br />

(points A to F <strong>on</strong> Fig. l), the un rotected<br />

upper bank materials c<strong>on</strong>sist of unrozen or<br />

relatively thaw stable frozen silt and sand.<br />

Upstream of the Galena Airfield and extending<br />

to near Beaver Creek (points F to J <strong>on</strong><br />

Fig. l), the shoreline generally c<strong>on</strong>sists of<br />

SITE CONDITIONS<br />

General<br />

Galena lies in a wide floodplain of the Yuk<strong>on</strong><br />

River. Sediments c<strong>on</strong>tained within the plain<br />

are Pleistocene or Holocene fine to<br />

coarse-grained deposits generally exhibiting<br />

distinct thin parallel stratificati<strong>on</strong>. The<br />

floodplain has four physiographic phases or<br />

units. each with distinct permafrost, drainage,<br />

vegetati<strong>on</strong>, and engineering characteristics<br />

(PCwd, 1948). Each of these phases is<br />

temporary (relative to geologic time) and<br />

somewhat evoluti<strong>on</strong>ary in nature due to<br />

permafrost growth, flooding, river meandering,<br />

and associated changes in vegetati<strong>on</strong>. These<br />

phases are readily identifiable from air photos,<br />

based <strong>on</strong> the shape and distributi<strong>on</strong> of<br />

lakes and vegetati<strong>on</strong>. The four phases in

L<br />

order of their ages (youngest to oldest) are Coalescent Phase<br />

the linear, advanced linear, coalescent, and<br />

scalloped phases (Weber and PbwWB, 1970). Each Stunted spruce and birch forests, as well as<br />

phase and its relevance to the erosi<strong>on</strong> c<strong>on</strong>trol developing peat moss tundra, are the primary<br />

project are briefly discussed below. Fig. 1 vegetati<strong>on</strong> <strong>on</strong> the coalescent phase of the<br />

also identifies the various physiographic<br />

floodplain. Linear lakes lying at various<br />

phase transiti<strong>on</strong>s within the Galena vicinity. angles to the Yuk<strong>on</strong> River become interc<strong>on</strong>nected<br />

due to wave acti<strong>on</strong> and cave-ins. Soils<br />

encountered in the lithology of this phase are<br />

micaceous and organic silts. <strong>Permafrost</strong><br />

generally occurs within 0.5 m of the ground<br />

surface. Massive ice is present, but<br />

Linear Phase<br />

The linear phase is characterized by distinct<br />

linear lakes parallel to the river and <strong>on</strong>e<br />

another. This phase is vegetated with grasses,<br />

alder, willows and cott<strong>on</strong>wood trees,<br />

<strong>Permafrost</strong> is generally absent or at depths of<br />

more than 6 m near the river's edge, but rfses<br />

in elevati<strong>on</strong> to 1-1.5 rn depth at the inner<br />

phase boundary. Massive ground ice is<br />

generally absent in the linear phase. This<br />

unit is the lowest lying and forms the most<br />

active part of the floodplain. The linear<br />

phase lithology c<strong>on</strong>sists of well stratified<br />

micaceous siit, sand, and gravel. The<br />

thickness of the linear phase lithology is<br />

thought to be equal to the depths of the Yuk<strong>on</strong><br />

Biver channel,<br />

polyg<strong>on</strong>al ground patterns have not been<br />

served.<br />

Scalloped Phase<br />

ob-<br />

This phase .is characterized by numerous<br />

irregularly shaped lakes, low vegetati<strong>on</strong> <strong>on</strong><br />

thick tundra and integrated drainage patterns.<br />

Some stunted black spruce, larch, birch, and<br />

willows are present. <strong>Permafrost</strong> occurs at 0.3<br />

m below the ground surface in protected areas.<br />

Large ground ice masses are pxesent in the<br />

silt and organic silt soils. Polyg<strong>on</strong>al ground<br />

is apparent in this advanced phase<br />

of<br />

floodplain development.<br />

Advanced Linear Phase<br />

The advanced linear phase is characterized by<br />

distinct linear lakes parallel to predominant<br />

drainage trends. These lakes are becoming<br />

segmented by encroaching vegetati<strong>on</strong>. Sediments<br />

composing this phase are found 1-2 m<br />

above river level and occur in thicknesses of<br />

1.2-4.7 m. Soils composing this alluvial<br />

phase are generally micaceous silts with<br />

relatively rare occurrences of sand and gravel<br />

strata. Vegetati<strong>on</strong> includes alder, birch and<br />

black spruce. <strong>Permafrost</strong> in this<br />

physiographic phase is generally present<br />

within the upper 1 m of the deposit, but is<br />

generally free of massive ice.<br />

DESIGN CONCERNS<br />

Soil Assessment<br />

Subsurface c<strong>on</strong>diti<strong>on</strong>s al<strong>on</strong>g the Galena segment<br />

of the Yuk<strong>on</strong> River have been defined in<br />

general terms during earlier studies completed<br />

by the U. S. Army Corps of Engineers, Pe'wd<br />

(1948) and Corps (1952; 1959) and more specifically<br />

in the study area identified as Phase I<br />

by R&M C<strong>on</strong>sultants (1985). The latter subsurface<br />

investigati<strong>on</strong> supported the design of the<br />

Phase I project and areas where subsequent<br />

slope protecti<strong>on</strong> were anticipated. This<br />

investigati<strong>on</strong> included drilling and sampling<br />

1313

of 10 boreholes; 2 <strong>on</strong> top of the bank and 8<br />

located at river level either near the shore<br />

120-<br />

or the thalweg. Generalized cross-secti<strong>on</strong>s<br />

shOwing soil and thermal c<strong>on</strong>diti<strong>on</strong>s €or Ranges<br />

5, 7 and B are shown in Figs, 2, 3 and 4,.<br />

respectively. These data indicated that the<br />

""L"-L<br />

100-<br />

riverbank between Ranges 4 and 7 c<strong>on</strong>siets of<br />

,approximately 4.5 to 7.5 m of frozen silt<br />

overlying sand and gravelly sand that is<br />

probably frozen inland from near the bank edge<br />

BOand<br />

intermittently frozen outward to the<br />

+<br />

advancing river thalweg. The overlying frozen<br />

I<br />

silt stratum encountered al<strong>on</strong>g the bank in<br />

ORAVELLY SAND<br />

60-<br />

TH-2 and TH-5 (near Ranges 5 and 7, respec-<br />

a SANDY GRAVEL<br />

tivelv) c<strong>on</strong>tained a moderate to low ice<br />

I<br />

c<strong>on</strong>tent. Visual inspecti<strong>on</strong> of the exposed<br />

bank in 1984 indicated the general absence of<br />

I<br />

c<br />

large segments of massive ice within this<br />

area. Significant massive ice was observed in<br />

HORIZONTAL<br />

"" 'yo 200 300<br />

the overlying silt al<strong>on</strong>g the bank from roughly<br />

SCALE<br />

'<br />

metere<br />

10 100<br />

Range 7 to well bey<strong>on</strong>d Range 11. These<br />

observati<strong>on</strong>s correlate with those compiled by<br />

Weber and Pdwd (1970), where they observed Fig. 3 Cross-Sectirm Showing Soil and<br />

that the coalescent and scalloped phases<br />

Thermal C<strong>on</strong>diti<strong>on</strong>s at Range 7 (March<br />

(lying east of roughly Range 7) were ice-rich<br />

1984)<br />

and c<strong>on</strong>tained massive ice,<br />

will.be mixed un€rozen/frozen outo the river<br />

thalweg. These c<strong>on</strong>diti<strong>on</strong>s were noted in three<br />

borings drilled below the river .bank where<br />

I20<br />

TRACE SAND<br />

frozen ground was found at varying depths<br />

35 below the river ice. Penetrati<strong>on</strong> refusal at<br />

depth in other borings also indicated the<br />

presence of deeper lying permafrost below the<br />

100<br />

30 river .<br />

80<br />

60<br />

e<br />

(Y<br />

el<br />

L<br />

tee1<br />

HORIZONTAL 7<br />

SCALE<br />

0 malar.<br />

WD a SAND wlrn \<br />

SOME<br />

GRAVEL TO GRAVELLY SAND<br />

aohd bar Indlcarrr<br />

Irm<strong>on</strong> maledo1<br />

100 200 300 400<br />

50 100<br />

Fig. 2 Cross-Secti<strong>on</strong> Showing Soil and<br />

Thermal C<strong>on</strong>diti<strong>on</strong>s at Range 5 (March<br />

1984)<br />

Permanent thermistor strings were installed in<br />

two test borings. The temperature profiles<br />

identified the apparent variability in the<br />

advance of the thaw bulb into the sand stratum<br />

underlying the silt. Both borings were<br />

located within the coalescent phase of the<br />

floodplain approximately the same distance<br />

behind the top of river bank. Unfrozen<br />

c<strong>on</strong>diti<strong>on</strong>s were found below a depth of 6.9 m<br />

in <strong>on</strong>e test hole. On the other hand, the<br />

sec<strong>on</strong>d test hole was completely frozen through<br />

its entire depth.<br />

Based <strong>on</strong> the limited borehole Informati<strong>on</strong>, it<br />

appears that underlying sands, gravelly sands<br />

and sandy gravels below elevati<strong>on</strong> 30.5 to 33 m<br />

may be present at about the<br />

same level or<br />

slightly lower east of Range 7. While<br />

segments of the underlying granular material<br />

occurs unfrozen at some locati<strong>on</strong>s below the<br />

bank, it is anticipated that most of this<br />

material is frozen behind the bank face and<br />

25<br />

20<br />

l'i<br />

I<br />

1314<br />

kAT<br />

Because of the river bank erosF<strong>on</strong> process and<br />

the relatively rapid northward advancement,<br />

the soil thermal state near the river bank<br />

itself was difficult to predict. Site studies<br />

and thermal modeling by Smith and Hwang (1973)<br />

<strong>on</strong> the Mackenzie River indlcated that the l<strong>on</strong>g<br />

term. thermal process involves a lag in tallk<br />

formati<strong>on</strong> with depth below the river al<strong>on</strong>g the<br />

cut bank side. They also indicate that the<br />

thermal affect of the river <strong>on</strong> the surrounding<br />

ground temperature field depends not <strong>on</strong>ly <strong>on</strong><br />

the strength of the field source but also <strong>on</strong><br />

3<br />

SILTY SAND<br />

INTERLAYERED VI/<br />

OROANIC MATERIAL<br />

~cc0114001 #IumoI 8 driftwood<br />

SILTY SANO __<br />

""""<br />

SILTY SANO<br />

"""" vw WATER<br />

SANDY GRAVEL INTERLAYERED<br />

t2<br />

1 &Izo<br />

1<br />

HORIZONTAL 100 200 SO0 400<br />

'<br />

SCALE 50 IO0<br />

met.,*<br />

Fig. 4 Cross-Secti<strong>on</strong> Showing Soil and<br />

Thermal C<strong>on</strong>diti<strong>on</strong>s at Range B (March<br />

1984)

the length of time available to the thermal<br />

process. C<strong>on</strong>diti<strong>on</strong>s found at Galena are<br />

similar to those reported by Smith and Hwang.<br />

The generalized soil profile developed al<strong>on</strong>g<br />

the bank indicated mixed frozen/unfrozen soil<br />

exists within the near shore below the river<br />

bank.<br />

Thermal Assessment<br />

Similar thermal erosi<strong>on</strong> phenomena of the<br />

Coleville River delta has been reported by<br />

Walker (1983). However, published informati<strong>on</strong><br />

<strong>on</strong> thermal performance of stabilized river<br />

bankswithrelativelyhighseas<strong>on</strong>alwater<br />

level fluctuati<strong>on</strong> is not available. Limited<br />

informati<strong>on</strong> <strong>on</strong> frozen reservoir embankments<br />

indicated that an uninsulated embankment<br />

segment of a dam remained frozen throughout<br />

the entire year (Fulwider, 1973 and B&M<br />

C<strong>on</strong>sultants, 1986) . However, the influence<br />

of c<strong>on</strong>vecti<strong>on</strong> resulting from warm summer river<br />

temperatures and higher flow velocities and<br />

erosi<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s, such as occur at Galena,<br />

would not apply to that case. Various<br />

unpublished thermal studies by Alyeska<br />

Pipeline Service Company evaluated c<strong>on</strong>vectf<strong>on</strong><br />

associatedwithfrozengroundandthawing<br />

slopes. Because of modeling difficulties, the<br />

influence of c<strong>on</strong>vecti<strong>on</strong> was generalized by<br />

c<strong>on</strong>servative assumpti<strong>on</strong>s for c<strong>on</strong>ducti<strong>on</strong> to<br />

simplify the evaluati<strong>on</strong>.<br />

Experience ained by Alyeska in the use<br />

of<br />

insulatl<strong>on</strong> or thermal stabilizati<strong>on</strong> of slopes<br />

is useful. Two installati<strong>on</strong>s at major road Fig. 5<br />

cuts c<strong>on</strong>taining ice-rich soil al<strong>on</strong>g the Dalt<strong>on</strong><br />

Highway, <strong>on</strong>e at Happy Valley <strong>on</strong>" the North<br />

Slope (McPhail et al. , 1975 and Brown and<br />

Kreig, 1983) and the other near Hess Creek<br />

north of Livengood (Ro<strong>on</strong>ey and C<strong>on</strong>do, 1984 and<br />

Mageau and Ro<strong>on</strong>ey, 1984), used insulati<strong>on</strong><br />

materials to retard thermal degradati<strong>on</strong> and<br />

significant slope erosi<strong>on</strong>.<br />

NATURAL<br />

GRANULAR<br />

MATERIAL<br />

GENERALIZED CROSS SECTION<br />

h, 2 0.62m (2.0 tt)<br />

h,- 0.45<br />

SECTION A-A<br />

QRANULAR FILL<br />

/INSULATION<br />

FROZEN SILT<br />

C<strong>on</strong>ceptual Insulated Embankment<br />

Sect i<strong>on</strong><br />

settlement assume that the insulati<strong>on</strong> maintains<br />

its structural and thermal integrity<br />

during the facility design life. Thaw settlement<br />

(TS) estimates in Fig. 6b are for average<br />

total settlement due to thaw; estimates are<br />

based <strong>on</strong> average thaw strain of SOX.<br />

Thermal Analysis<br />

The dashed line estimates in Flg. 6b show thaw<br />

depth and thaw settlement using thermal<br />

The modified Berggren equati<strong>on</strong> was used to c<strong>on</strong>ductivity values averaged between the<br />

analyze the potential thermal performance of<br />

estimates of k for silt - 1.0 W/mK and k for<br />

the embankment design shown in Fig, 5. The<br />

granular embankment material = 2.9 W/mK.<br />

analysis c<strong>on</strong>sidered the influence of uncer-<br />

These estimates represent possible thermal<br />

tainty in estimated (silt) thaw strain and<br />

affects where large amounts of gravel<br />

used a formulati<strong>on</strong> which maintained c<strong>on</strong>sisten-<br />

(embankment) material are needed to fill thaw<br />

cy between thaw strain and latent heat in the<br />

depressi<strong>on</strong>s in the embankment. In all cases<br />

silt. These results were, however, c<strong>on</strong>sidered<br />

thaw depth and thaw settlement estimates<br />

<strong>on</strong>ly suitable for a c<strong>on</strong>ceptual design. Any<br />

decrease with increasing insulati<strong>on</strong> thickness.<br />

further analyses should be based <strong>on</strong> a more<br />

The thermal affect is very significant for no<br />

refined analysis using two-dimensi<strong>on</strong>al<br />

insulati<strong>on</strong> whereas with as 'little as 50 nun of<br />

geometry to c<strong>on</strong>sider end and corner effects.<br />

insulati<strong>on</strong> this affect is c<strong>on</strong>siderably<br />

reduced. With 100 mm and 150 mm of<br />

Results of the preliminary analysis are shown<br />

insulatt<strong>on</strong>, the thermal affect is not<br />

a8<br />

in FFg. 6. These results include estimates of<br />

significant.<br />

the average thaw depth and average thaw<br />

settlement plotted as a functi<strong>on</strong> of thermal Design Interpretati<strong>on</strong><br />

load ('Iz) for four insulati<strong>on</strong> thicknesses: 0 ,<br />

50, 100 and 150 mm. Two values of subgrade FigZ. 6a shows three thermal loads: (1) a<br />

thermal c<strong>on</strong>ductivity (k) were used. Thermal maximum thaw index based <strong>on</strong> CRREL Technical<br />

load is plotted in Fig. 6 as a functi<strong>on</strong> of Report 102 (Aitken, 1963), (2) a 10-year<br />

average surface temperature (ST) load and thermal load, and (3) a 20-year thermal load,<br />

time. The need for insulati<strong>on</strong> to minimize<br />

An equivalent average surface temperature,<br />

effects of thermal degradati<strong>on</strong> is suggested by (ST) of -15.5"C was used for the<br />

10 and<br />

results presented in this figure.<br />

20-year thermal loads. This estimate of ST<br />

represents a c<strong>on</strong>servative value for Galena<br />

Estimates of average thaw depth and thaw<br />

appropriate for a surface thermal disturbance<br />

1315

a. b.<br />

IO<br />

AVERAGE THAW DEPTH ESTIMATE (TD)<br />

p meters I 2 3 4<br />

0 feet 6 4 6 8 IO 12<br />

INSULATION<br />

THICKNESS<br />

150mm(6ln~KX)mm(4 InJ<br />

SOrnm(2 In.)<br />

\ 0<br />

a<br />

""<br />

8<br />

""_<br />

4<br />

-""<br />

2<br />

0<br />

TIME In YEARS (t) meters 0.5 1.0 1.5 2.0<br />

0 faat ; 2 3 4 5 6<br />

AVERAGE THAW SETTLEMENT POTENTIAL (TS)<br />

'Fig. 6<br />

Average Thaw DepthISettlement Analysis and Interpretati<strong>on</strong><br />

of (warm) pennafrost existing at about -1°C.<br />

The corresp<strong>on</strong>ding estimates of average thaw<br />

depth and thaw settlement are shown.<br />

Interpretati<strong>on</strong> of the results based <strong>on</strong> a<br />

the embankment. In particular, further design<br />

thermal load due to an average surface temper- and maintenance efforts should attempt<br />

to<br />

ature of approximately -15.5"C give estimates minimize water from flowing under the<br />

of thaw settlement of the uninsulated silt embankment and insulati<strong>on</strong> (either al<strong>on</strong>g<br />

or<br />

embankment from about 1.7 m to more than 2 m down the bank), Successful performance of the<br />

fn 20 years. Installati<strong>on</strong> of 100 nrm of design assumes and requires <strong>on</strong>going<br />

inaulati<strong>on</strong> would reduce estimated thaw<br />

maintenance of the embankment bench and<br />

settlement in half: reducing the 20-year<br />

adjacent bank, Lack of proper maintenance may<br />

estimated thaw settlement to about 1 m; the<br />

10-yearestimatetoabout 0.5 m, andthe<br />

5-year estimate to less than 0.3 m.<br />

Using the c<strong>on</strong>ceptual embankment design shown<br />

in Fig. 5 there are two alternatives: (1) use<br />

(polystyrene) insulati<strong>on</strong>, and (2) do not use<br />

insulati<strong>on</strong>. Insulati<strong>on</strong> was recommended to<br />

provide adequate stability for any future bank<br />

protecti<strong>on</strong> projects located within either the<br />

coalescent or scalloped physiographic phases<br />

at locati<strong>on</strong>s where ice-rich and significant<br />

thaw settlement c<strong>on</strong>diti<strong>on</strong>s are identified. A<br />

minimum of 50 mm but preferably 100 mm were<br />

suggested to reduce the rate and magnitude of<br />

thaw and resulting settlement. Geo-fabric was<br />

c<strong>on</strong>sidered for placement <strong>on</strong> top of the bank.<br />

A minimum of .45 m of n<strong>on</strong>-frost susceptible<br />

(NFS) granular fill was recommended for<br />

placement <strong>on</strong> top of the fabric. A minimum of<br />

.62 m of fill placed above the insulati<strong>on</strong><br />

would provide protecti<strong>on</strong> from subsequent c<strong>on</strong>-<br />

1316<br />

structt<strong>on</strong> and operati<strong>on</strong>al traffic loads.<br />

Grading and drainage should be performed such<br />

that surface and melt water is diverted from<br />

result in undesirable damage to the proposed<br />

slope protecti<strong>on</strong> scheme and c<strong>on</strong>sequently to<br />

further deteriorati<strong>on</strong> of the river bank and<br />

protecti<strong>on</strong> system. If snow is removed or does<br />

not accumulate <strong>on</strong> the top of the embankment<br />

during winter, thaw and settlement rates and<br />

magnitudes will be reduced.<br />

CONCLUSIONS<br />

Bank protecti<strong>on</strong> soluti<strong>on</strong>s for the Yuk<strong>on</strong> River<br />

at Galena, Alaska were developed to protect<br />

against upper bank thermo-erosi<strong>on</strong>al niching<br />

associated with hydraulic c<strong>on</strong>diti<strong>on</strong>s. C<strong>on</strong>cep"<br />

tual designs accommodated for anticipated<br />

variability in both soil and permafrost<br />

Z<strong>on</strong>diti<strong>on</strong>s. Geotechnical c<strong>on</strong>siderati<strong>on</strong> of<br />

thaw degradati<strong>on</strong> and ground settlement were<br />

related to geologic deposits comprising four<br />

physiographic phases. Relatively c<strong>on</strong>venti<strong>on</strong>al

ank slope protecti<strong>on</strong> was installed <strong>on</strong> a<br />

frozen bank secti<strong>on</strong> wFth low thaw strain<br />

potential. An insulated embankment design was 130<br />

developed for applicati<strong>on</strong> al<strong>on</strong>g those secti<strong>on</strong>s<br />

of the bank where higher ice c<strong>on</strong>tents and thaw<br />

strain potential were encountered.<br />

C<strong>on</strong>structi<strong>on</strong> of approximately 656 m of bank<br />

protecti<strong>on</strong> using the typical secti<strong>on</strong> shown in<br />

Fig. 7, was accomplished within the designated<br />

Phase I area (Fig. 1). The next segment.<br />

identified as Phase I1 <strong>on</strong> Fig. 1, is currently<br />

being c<strong>on</strong>structed by the Corps using a typical<br />

secti<strong>on</strong> similar to that shown in Fig. 7. Fig.<br />

8, is a c<strong>on</strong>ceptual typical secti<strong>on</strong> which has<br />

not been utilized in either c<strong>on</strong>structi<strong>on</strong> phase<br />

since soil ice c<strong>on</strong>tent has been relatively low<br />

within the bank secti<strong>on</strong>s c<strong>on</strong>sidered to this<br />

time. Due to the limited thaw seas<strong>on</strong>s since<br />

commencement of the phased c<strong>on</strong>structi<strong>on</strong><br />

project, performance data are not yet<br />

available.<br />

IPO<br />

110<br />

100<br />

90,<br />

+<br />

u<br />

c<br />

(SUMMLR RIVER ELEV. =<br />

0.43 111 IlEIn4 QRANULAR<br />

LEVELlNO FILLER -40<br />

/I O.Sn (12 In.) ORAVEL<br />

( UNDER INSULATION<br />

100 mm<br />

INSU<br />

-"<br />

FROZEN/UNFROZEN<br />

SAND R GRAVEL<br />

L DEPTH TO STRATUM L<br />

-38<br />

-30<br />

INTERFACE 15 VARIABLE c<br />

*<br />

E<br />

- 31<br />

Fig. 8 Typical Embankment Secti<strong>on</strong> For High<br />

Thaw Strain Soil<br />

McPhail, J. F., McMullen, W.B. and Murfitt,<br />

A.W., (1975). Design and c<strong>on</strong>structi<strong>on</strong> of<br />

roads <strong>on</strong> muskeg in arctic and subarctic<br />

~..-.-*-."<br />

regi<strong>on</strong>s, 16th Annual Muskeg <strong>Research</strong><br />

.<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, NRC of Canada, M<strong>on</strong>treal.<br />

.'.: UNCOMPACTLO MAT<br />

Pdwd. T.L. (1948). Terrain and permafrost,<br />

SAND I ORAVEL<br />

Galena Air Base. Galena, AK: Progress<br />

Report 7, U.S.G.S. <strong>Permafrost</strong> Program,<br />

52p.<br />

RLM C<strong>on</strong>sultants, Inc.. (1986). Vortac dam and<br />

abutment repairs study, Prepared for City<br />

of Kotzebue, AK.<br />

R&M C<strong>on</strong>sultants, Inc., (1985). Galena bank<br />

I 1<br />

stabilizati<strong>on</strong>. Prepared €or Alaska<br />

DOTIPF, Project No. K-83513.<br />

Fcg. 7 Typical Embankment Secti<strong>on</strong> For Low Ro<strong>on</strong>ey, J.W. and C<strong>on</strong>do, A.C. (19841, Hess *<br />

Thaw Strain Soil<br />

Creek thermal erosi<strong>on</strong> test site: Frozen<br />

cut slope surface treatments. 3rd Intl.<br />

. Speciality <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>: Cold Regi<strong>on</strong>s<br />

Engineering, Vol. III., Edm<strong>on</strong>t<strong>on</strong>.<br />

Smith, M.W. and Hwang, C.T. (1973). Thermal<br />

disturbance due to channel shifting,<br />

REFERENCES<br />

Proc. 2nd Intl. <strong>Permafrost</strong> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>,<br />

NAS, pp. 51-59.<br />

Aitken, G.W. (1963). Ground temperature<br />

U.S. Dept. of the Army. (1952). Preliminary<br />

observati<strong>on</strong>s, Galena, AK, U.S. Army<br />

study of erosi<strong>on</strong> c<strong>on</strong>trol Galena Airfield<br />

CRREL, Tech. Report 102, 15p.<br />

AK. Corps, Alaska District, Anchorage,<br />

Brown,,, J., and Kreig, R.A., eds. (1983).<br />

AK.<br />

Guide to permafrost and related features U.S. Dept. of the Amy. (1959). Foundati<strong>on</strong><br />

al<strong>on</strong>g the Elliott and Dalt<strong>on</strong> Highways,<br />

and materials investigati<strong>on</strong>s for erosi<strong>on</strong><br />

Fox to Prudhoe Bay, AK", Guidebook 4 , 4th<br />

c<strong>on</strong>trol of Yuk<strong>on</strong> River, Galena Airport,<br />

Int1. <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>, Alaska<br />

AK ,<br />

DGGS, 230 p.<br />

Walker, W.J. (1983). Erosi<strong>on</strong> in'a perma-<br />

Fulwider, C.W. (1973). Thermal regime in an<br />

frost-dominated delta, Proc. 4th Intl.<br />

arctic earthfill dam, Proc., 2nd Intl.<br />

<strong>Permafrost</strong> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, NAS,<br />

<strong>Permafrost</strong> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, NAS, pp. 622-628.<br />

pp. 1344-1349.<br />

Mageau, D.W. and Ro<strong>on</strong>ey, J.W. (1984). Thermal, Weber, F.R. and Pdwd, T.L. (1970). Surficial<br />

erosi<strong>on</strong> of cut slopes in ice-rich soil,<br />

and engineering geology of the central<br />

Alaska DOTfPF, Report No.<br />

part of the Yuk<strong>on</strong>-Koyukuk lowland, AK.<br />

FWA-AK-RD-85-02.<br />

U.S.G.S.,Map 1-590.<br />

1317

AIRPORT RUNWAY DEFORMATION AT NOME, ALASKA<br />

J.W. Rmneyl, J.E Nix<strong>on</strong>z, C.H. Riddle* and E.G. Johns<strong>on</strong>3<br />

1R&M C<strong>on</strong>sultants, hc., Anchorage, Alaska 99503, USA<br />

*Hardy BBT, Ltd., Calgary, Alberta, Canada T2E 655<br />

3Alaska Dept. of Transportati<strong>on</strong> & Public Facilities, Anchorage, Alaska 99519, USA<br />

SYNOPSIS: The Nome Airport runways were c<strong>on</strong>structed in 1942 <strong>on</strong> a mixture of dredged silts and<br />

sands, and n<strong>on</strong>-dredged, generally frozen silts and organic silts. The dredged materials have<br />

remained unfrozen in many cases, whereas the n<strong>on</strong>-dredged permafKOSt areas may c<strong>on</strong>tain significant<br />

excess ice. The runways were paved initially in 1943, and a c<strong>on</strong>tinual history of vertical pavement<br />

movement has been recorded since. Subsurface investigati<strong>on</strong> and geotechnical evaluati<strong>on</strong> identified<br />

soil profiles, ground thermal regime and other geotechnical parameters necessary for<br />

c<strong>on</strong>ceptual design and c<strong>on</strong>structi<strong>on</strong> c<strong>on</strong>siderati<strong>on</strong>s. All of this data, al<strong>on</strong>g with previous study<br />

results, were utilized to evaluate subsurface and pavement c<strong>on</strong>diti<strong>on</strong>s and to develop alternative<br />

c<strong>on</strong>ceptual designs. Frozen natural deposits appear to be the major significant cause of ground<br />

settlement, whereas the embankment material composed of coarse tailings has a very high frost<br />

heave potential. Additi<strong>on</strong>ally, subsurface drainage systems were found to have an affect <strong>on</strong> the<br />

subsurface soil thermal state.<br />

INTRODUCTION<br />

The Nome, Alaska Airport was c<strong>on</strong>structed by<br />

military c<strong>on</strong>tractors in 1942 as part of the<br />

Alaska-Siberia Lend-Lease (ALSIB) program. The<br />

airport was part of a system of airports used<br />

to ferry lend-lease airplanes to the U.S.S.R.<br />

durin World War 11. Much of the ground<br />

underfying both runways had been dredged and<br />

reworked during previous gold mining activities.<br />

Apparently, initial c<strong>on</strong>structi<strong>on</strong><br />

occurred <strong>on</strong>ly over areas that had previously<br />

been excavated using a bucket dredge and where<br />

ample dredge tailings were available for use as<br />

embankment material. The runways were obviously<br />

completed with haste and without utilizati<strong>on</strong><br />

of modern methods of permafrost<br />

c<strong>on</strong>structi<strong>on</strong>. The runway surfaces have experienced<br />

<strong>on</strong>going vertical deformati<strong>on</strong> since<br />

original c<strong>on</strong>struczi<strong>on</strong>. Patching and major<br />

repairs have been required periodically over<br />

the m3re than forty year use of this facility.<br />

The runways were rec<strong>on</strong>structed Fn 1958-59 with<br />

installati<strong>on</strong> of a major subdrain system. The<br />

runways were rec<strong>on</strong>structed again in 1973-74.<br />

Additi<strong>on</strong>al pavement repairs were made in<br />

1984-85 (Fig. 1).<br />

SITE CONDITIONS<br />

Geologic Setting<br />

The city of Nome is located <strong>on</strong> the south coast<br />

of the Seward Peninsula al<strong>on</strong>g Nort<strong>on</strong> Sound,<br />

about 820 km west of Fairbanks and approximately<br />

885 km northwest of Anchorage (Fig. 1).<br />

Bedrock c<strong>on</strong>sists of Paleozoic schist, gneiss,<br />

marble and metamorphosed volcanic racks, all of<br />

,which are cut by granitic intrusive masses<br />

(Sainesbury et al., 1972). <strong>Permafrost</strong> in the<br />

- 'k .<br />

Fig. 1<br />

Nome Airport Site Map<br />

Nome area has been measured to about 27.5 to<br />

36.5 m in thickness (AEIDC, 1976). Nome<br />

Airport is located about 1.6 km west of the<br />

town of Nome near the mouth of Center Creek<br />

where it c<strong>on</strong>verges with the Snake River<br />

(Fig. 1). Both Center Creek and the Snake<br />

River have been extensively re-routed into<br />

man-made channeh in order to facilitate earlier<br />

dredging activltles and subsequent airport<br />

improvements. Currently. Center Creek runs<br />

al<strong>on</strong>g the west edge of the North-South Runway<br />

and flows through a 1.2 m CMP underneath the<br />

East-West Runway before discharging into the<br />

Snake River (Fig. 1). Also, pipes for a<br />

subdrain system were installed in 1957 under<br />

much of both runways in order to draln shallow<br />

groundwater out of the runway embankment.<br />

1318

METER8<br />

I<br />

PO0<br />

Fig. 3<br />

I<br />

I<br />

too 400 600 100 700 100 so0<br />

Pavement Surface Surveys - A Porti<strong>on</strong> of East-West Runway Centerline<br />

Geologic profiles were prepared during the<br />

recent study (RLM C<strong>on</strong>sultants, 1987) for both<br />

runways showing interpreted soil, bedrock,<br />

groundwater and thermal c<strong>on</strong>diti<strong>on</strong>s, Additi<strong>on</strong>ally,<br />

topographic surveys were performed<br />

al<strong>on</strong>g both runways and plotted al<strong>on</strong>g with prior<br />

survey data. A porti<strong>on</strong> of these centerline<br />

profiles for the East-Weat Runway are shown in<br />

Figs. 2 and 3.<br />

Subsurface Soils<br />

Much of the ground underlying both runways has<br />

been dredged and reworked during previous gold<br />

mining activities. The results of such dredging<br />

was to generally reverse the normal order<br />

of natural depositi<strong>on</strong>. The surficial organic<br />

silts may now be found immediately overlying<br />

bedrock followed by sands and then coarse<br />

tailings at the surface. Undisturbed terrain<br />

soil c<strong>on</strong>sists generally of loess and colluvium<br />

covering Pleistocene till deposits. Outwash<br />

sand and gravel occur in the alluvial stream<br />

1319<br />

valleys. Marine sands and silty sands are<br />

interpreted to interfinger with the terrestrial<br />

deposits. Schist bedrock is generally encountered<br />

below about 7.5 rn in depth.<br />

Groundwater and Surface Drainage<br />

Groundwater was encountered while drilling in<br />

many of the boreholes. Generally, borings that<br />

encountered no groundwater were located in<br />

undredged areas or occurred at locati<strong>on</strong>s where<br />

the borehole encountered generally frozen soil<br />

for the entire depth. Seas<strong>on</strong>al variati<strong>on</strong>s due<br />

to spring snow melt, rainfall or a rise in the<br />

levels of Center Creek and the Snake River may<br />

significantly alter the groundwater depth. In<br />

additi<strong>on</strong>, because of the underlying permafrost<br />

layer, it is felt that the water level repre-<br />

sents a "perched" water table that is highly<br />

influenced by the above-stated seas<strong>on</strong>al variati<strong>on</strong>s<br />

and ground thermal state. Periodically,<br />

atoms <strong>on</strong> Nort<strong>on</strong> Sound raise the level of the<br />

Snake River to within a meter of the runway

surface. This back charges the subdrain system<br />

and fills ditches adjacent to the runway.<br />

Groundwater Elow velocities in some areas have<br />

been estimated to be above minimum values that<br />

make c<strong>on</strong>vective heat flow a significant thermal<br />

effect.<br />

<strong>Permafrost</strong><br />

An initial <strong>on</strong>e-dimensi<strong>on</strong>al thermal simulati<strong>on</strong><br />

was carried out for the period to 1942 1986, to<br />

<strong>Permafrost</strong> was encountered in many of the test determine the. anticipated resp<strong>on</strong>se of an<br />

borings at depths ranging from 2.8 to 9.8 m. unfrozen area of dredged tailings to l<strong>on</strong>g term<br />

Massive ice was encountered in several borings seas<strong>on</strong>al freezing and thawing. The simulator<br />

located,' in n<strong>on</strong>-dredged areas. In additi<strong>on</strong>,<br />

includes phase change and thermal properties<br />

from 2 to 10 percent visible ice was observed for several different soil layers. The surface<br />

in numerous borings as random crystals, coat- air temperature was estimated from a series of<br />

ings <strong>on</strong> particles and stratified formati<strong>on</strong>s. mean m<strong>on</strong>thly temperatures given as data to the<br />

Thermistor data shows that several intervals<br />

program. The simulati<strong>on</strong> predicted that freezewere<br />

observed to be below O°C but the material back should have occurred in all dredged soil<br />

clearly behaved as if unfrozen, based <strong>on</strong> blow areas over the period studied. In fact, this<br />

counts, pushed samples, drilling rate, etc. In has not happened in many areas, indicating that<br />

these situati<strong>on</strong>s. the unfrozen c<strong>on</strong>diti<strong>on</strong> was<br />

some c<strong>on</strong>vective heat flow comp<strong>on</strong>ent must be at<br />

thought to result from soil salinity freezing work. The predicted ground temperature prepoint<br />

depressi<strong>on</strong> or the c<strong>on</strong>vective influence of files agree quite closely with the actual<br />

groundwater flow. Seas<strong>on</strong>al frost was observed temperature distributi<strong>on</strong>s measured in the upper<br />

to be <strong>on</strong> the order of 1.4 to 3.9 m deep with 3 to 4.5 m in December, 1986. The simulati<strong>on</strong><br />

most borings showing 2.1 to 2.7 m of active predicted that frost should have aggraded into<br />

layer. Little to no visible ice was encoun- the ground to a depth of 9 to 12 m.<br />

tered within the active layer.<br />

Some dredged areas of the runway are in the<br />

rocess of freezing back. Examples of this may<br />

{e seen <strong>on</strong> both runways. In the East-West<br />

DESIGN CONCERNS<br />

Runway, a layer of dredged sand overlies a<br />

dredged sandy silt at depth for over a large<br />

Ground Thermal Behavior<br />

proporti<strong>on</strong> of its length. The upper layer of<br />

sand and silty sand appears in most boreholes<br />

A maritime climate provides cool, cloudy<br />

to be unfrozen, whereas the deeper sandy silt<br />

weather for Nome in summer, with frequent rain material appears in most boreholes<br />

to be<br />

storms. In November, the climate changes from frozen. This upper cleaner sand layer appears<br />

maritime to c<strong>on</strong>tinental when the adjacent<br />

to extend to a depth of 4 a 5 m or more. The<br />

Nort<strong>on</strong> Sound freezes. The average freezing<br />

lower sandy silt layer typically occurs about<br />

index for 1951-1976 was about 2624°C-days, and 4.5 m below pavement surface and c<strong>on</strong>tinues to<br />

the average thawing index was about 948"C-days, bedrock at a depth of 7.5 to 9 m. Therefore,<br />

providing a mean air temperature of -4.1"C.<br />

it appears that the coarser-grained dredged<br />

The L<strong>on</strong>g term average prior to 1977 was about materials are not freezing back, at least <strong>on</strong> a<br />

-3.9OC. However, during che seven year period permanent basis, and may be thawing each year<br />

from 1977 to 1983 inclusive, a series<br />

of due to the acti<strong>on</strong> of c<strong>on</strong>vective groundwater<br />

anomalously warm years occurred, in which the flow. The finer grained dredged materials<br />

mean annual temperatures remained c<strong>on</strong>sistently appear to have returned to the permafrost<br />

above the previous l<strong>on</strong>g term average in the c<strong>on</strong>diti<strong>on</strong>, and is likely due to a much lower<br />

range of -3.9 to - 0.3"C.<br />

potential for groundwater flow and c<strong>on</strong>sequent<br />

c<strong>on</strong>vective heat transfer.<br />

From the winter of 1984 to summer of 1985,<br />

readings were taken of air, pavement and gravel From the pavement surface surveys c<strong>on</strong>ducted <strong>on</strong><br />

surface temperatures every 2 hours, and average the runways in the early and late winter of<br />

daily and seas<strong>on</strong>al n-factors were calculated 198611987, the seas<strong>on</strong>al frost heave can, in<br />

(Johns<strong>on</strong>, 1986). The summer n-factors were<br />

part, - be related to the material type present<br />

1.63 and 1.32 for asphalt pavement and gravel, in the upper 3 m in the seas<strong>on</strong>al frost z<strong>on</strong>e.<br />

respectively. The winter n-factor for the<br />

Seas<strong>on</strong>al frost heave is most apparent in<br />

pavement was 1.04. These values together with locati<strong>on</strong>s where the percentage of fine soil<br />

the actual mean m<strong>on</strong>thly air temperatures were particles in the surface embankment tailings is<br />

used in thermal simulati<strong>on</strong>s for the paved<br />

higher. Also, in areas where the dredged sand<br />

runways. It is important to note that all of comes right to the surface, the frost heave is<br />

the mean annual pavement surface temperatures, a minimum. This suggests that the presence of<br />

based <strong>on</strong> l<strong>on</strong>g term historical data and the the embankment tailings with the highest<br />

above menti<strong>on</strong>ed n-factors, are below<br />

0°C. percentage of silt with some clay particles,<br />

Calculati<strong>on</strong>s based <strong>on</strong> heat c<strong>on</strong>ducti<strong>on</strong> will tend corresp<strong>on</strong>ds to the area where frost acti<strong>on</strong><br />

to predict stable permafrost in the l<strong>on</strong>g term appears to be the most severe, as would be<br />

under the paved runway.<br />

expected.<br />

Measurements taken in dredged and n<strong>on</strong>-dredged<br />

areas reveal that ground temperatures in frozen<br />

areas are very close to the freezing point at<br />

depth with mean temperatures between 0 and<br />

-0.6"C. In unfrozen areas, the ground temperatures<br />

at depth are generally within 0 to 0.6"C.<br />

1320<br />

It should be noted that some isolated areas of<br />

significant salinity (2 to 18.8 ppt) were<br />

delineated. In general, however, salinities<br />

appear to be in the range 0 of to 3 ppt, which<br />

is less than <strong>on</strong>e-tenth that of normal sea<br />

water.<br />

The maximum seas<strong>on</strong>al frost heave measured <strong>on</strong><br />

the North-South Runway was approximately<br />

140 mm, whereas <strong>on</strong> the East-West Runway the<br />

equivalent maximum seas<strong>on</strong>al frost heave was<br />

approximately 120 m. On the North-South<br />

Runway, the area of highest seas<strong>on</strong>al frost

I<br />

heave is at Stati<strong>on</strong> 40+00; This is an area of Segregati<strong>on</strong> Potenti+l parameter varied from<br />

relatively thick embankment tailings, and the approximately .17Ox1O1 mmZ/sec"S at a pressure<br />

percentage of fines is around 24% (minus #200 of 43 kPa, to a value of 32x10 mm2/sec0C at<br />

sieve size). Frost heave tests c<strong>on</strong>firmed the the highest test pressure of 144 kPa. These<br />

significant frost susceptibility of this values are indicative of a material of relamaterial,<br />

even though the grain size curve does tively high frost susceptibility. A descripnot<br />

suggest a particularly high degree of frost ti<strong>on</strong> <strong>on</strong> the use of the Segregati<strong>on</strong> Potential<br />

susceptibility.<br />

parameter in frost heave predicti<strong>on</strong>s can be<br />

obtained from Nix<strong>on</strong> (1987). The frost suscep-<br />

In relatively impermeable soils, vertical heat tibility decreases rapidly with increasing<br />

flow by c<strong>on</strong>ducti<strong>on</strong> is the primary mode of heat pressure. Therefore, this material can be<br />

transfer causing seas<strong>on</strong>al freezing and thawing. expected to exhibit significant frost heave<br />

In coarser grained soils, the possibility for under c<strong>on</strong>diti<strong>on</strong>s 'of low overburden pressure.<br />

near horiz<strong>on</strong>tal groundwater flow exists, and a However, as the degree of c<strong>on</strong>finement or<br />

pressure in the ground increases, with depth,<br />

the degree of frost heave susceptibility can b<br />

expected to decrease significantly.<br />

new source of heat becomes available, should<br />

groundwater enter the freezing or thawing<br />

system at temperatures above freezing. As the<br />

dredged channels meander through the study<br />

site, and old river channels are present in the<br />

area, the potential for groundwater flow al<strong>on</strong>g<br />

coarse grained river channels or dredged areas<br />

is extremely high. In additi<strong>on</strong>, a creek has<br />

been diverted through the East-West Runway by<br />

means of a 1.2 m diameter CMP near the intersecti<strong>on</strong><br />

between the two runways. Assuming that<br />

the culvert entrance is not protected by<br />

impermeable soils, then it is very likely that<br />

a significant comp<strong>on</strong>ent of groundwater flow<br />

exists across the East-West Runway parallel to<br />

this CMP. In additi<strong>on</strong>, the sub-drain system<br />

installed in 1957 provides further possibilities<br />

for lateral groundwater flow al<strong>on</strong>g old<br />

drain trenches, that have been backfilled with<br />

more permeable or looser backfilled materials.<br />

In general, the influence of c<strong>on</strong>vecti<strong>on</strong> is to<br />

cause a positive inflow of heat into the system<br />

thereby slowing down or preventing l<strong>on</strong>g term<br />

freeze back of the affected soil, or alternatively,<br />

accelerating the depth of thaw. In<br />

view of the fact that the ground temperatures<br />

in this area are very close to the melting<br />

point, any small positive c<strong>on</strong>vective heat<br />

influx may be resp<strong>on</strong>sible €or significant<br />

deviati<strong>on</strong> in the depth of freezing and thawing<br />

predicted by purely c<strong>on</strong>ductive analyses.<br />

C<strong>on</strong>vective heat flow is likely the explanati<strong>on</strong><br />

why some areas of dredged material have not<br />

frozen back in the 45 years since runway<br />

c<strong>on</strong>structi<strong>on</strong>. Comparis<strong>on</strong> of the pavement<br />

surface surveys carried out In late 1986 with<br />

earlier surveys (Fig. 3) c<strong>on</strong>firms that settlement<br />

of the pavement surface has taken place<br />

over many years, at certain reas<strong>on</strong>ably well<br />

identified settlement areas. These areas<br />

include the seven areas described in the<br />

ADOTIPF report (Johns<strong>on</strong>, 1986).<br />

Frost Heave<br />

A bulk sample of silty, sandy gravel tailings<br />

was collected for frostheavetesting. The<br />

fine fracti<strong>on</strong> of this material was comprised of<br />

micaceous platy particles. The grain size<br />

with distributi<strong>on</strong> 4% clay sizes indicated (minus 11X finer than 0.002 nun). There 0.02 was<br />

mm,<br />

no change in grain size characteristics before<br />

and after the freeze thaw cycles carried out in<br />

this test series. This indicated that weathering<br />

was not c<strong>on</strong>tinuing to take place in the<br />

sample due to freeze-thaw cycles in the laboratory.<br />

The initial water c<strong>on</strong>tent of the soil<br />

was 10.8% and the final water c<strong>on</strong>tent after<br />

four freeze thaw cycles was 8.3%. The sample<br />

was saturated throughout the test process. The<br />

1321<br />

The tailings embankment material is more frost<br />

susceptible than would be expected from the<br />

grain size curve. It is str<strong>on</strong>gly suspected<br />

that this is due to the mineralogy and platy<br />

nature of the silt and fine sand size particles,<br />

That is, material retained <strong>on</strong> the 200<br />

mesh may .have <strong>on</strong>e dimensi<strong>on</strong> equal to the 200<br />

mesh, but the other dimensi<strong>on</strong>s of the platy<br />

particles may be significantly less. Therefore,<br />

the smaller dimensi<strong>on</strong> could c<strong>on</strong>tribute to<br />

an increase in frost susceptibility.<br />

In order to study the near surface seas<strong>on</strong>al<br />

frosc heaving apparently taking place in the<br />

surface dredged tailings, another simulati<strong>on</strong><br />

was carried out as shown in Fig. 4. The<br />

profile assumed was 0.15 m of asphalt overlying<br />

1.7 m of the coarse tailings at a water c<strong>on</strong>tent<br />

of 64. This upper layer was assumed To be<br />

n<strong>on</strong>-frost susceptible, in view of the fact it<br />

is above the water table and likely unsat-'<br />

urated. Below the 2 m elevati<strong>on</strong>, another layer<br />

of coarse tailings was assumed to be present to<br />

a depth of 3.4 m below pavement surface. Below<br />

this, a dredged sandlsilt of 20% moisture<br />

c<strong>on</strong>tent was assumed. Fig. 4 shows the<br />

predicted frost depth from 1969 to the present,<br />

and also shows the predicted seas<strong>on</strong>al frost<br />

heave that would take place as the resukt of<br />

the seas<strong>on</strong>al frost acti<strong>on</strong>.<br />

The seas<strong>on</strong>al depth of frost is shown to vary<br />

between 3.4 and 4.4 rn depending <strong>on</strong> the severity<br />

of the winter. The amount of seas<strong>on</strong>al frost<br />

heave occurring as a result of this is shown to<br />

vary from 30 to 50 mm, again depending <strong>on</strong> the<br />

severity of the winter. C<strong>on</strong>sidering that this<br />

is based <strong>on</strong> a single or average determinati<strong>on</strong><br />

of the frost heave parameters, this appears to<br />

agree reas<strong>on</strong>ably well with the average frost<br />

heave measured over the winter 198611987 by th<br />

topographic surveys (0-140 nun),<br />

One opti<strong>on</strong> for stabilizing the runway surface<br />

may involve pre-thawing of currently frozen<br />

areas c<strong>on</strong>taining ice, and densifying the soil.<br />

One problem with this approach i s the possibility<br />

of re-freezing and frost heave over a l<strong>on</strong>g<br />

period of time in the future after remedial<br />

acti<strong>on</strong> has been taken. The predicti<strong>on</strong> carried<br />

out earlier used historical surface temperature<br />

data to predict l<strong>on</strong>g term frost advance. In<br />

order to project the future freezeback of a<br />

thawed area of silt or sandy silt, another<br />

freezeback simulati<strong>on</strong> was completed using 30<br />

year average surface temperatures, and assuming<br />

these would apply for the future. The same

600<br />

E<br />

E 400<br />

0<br />

><br />

0<br />

2<br />

c PO0<br />

e<br />

L<br />

0<br />

UEDROCK<br />

For the first five years of the simulati<strong>on</strong>, the<br />

frost depth increases but is thawed out each<br />

year. After this time, however, a c<strong>on</strong>tinual<br />

but slowly aggrading permafrost situati<strong>on</strong><br />

develops. The rate of increase in the thickness<br />

of permafrost is approximately 0.2 mlyear,<br />

andthis is anticipatedtoc<strong>on</strong>tinuefor a<br />

further 10 to 20 years. C<strong>on</strong>currently with<br />

this, the rate of frost heave of the pavement<br />

surface is predicted to be approximately 12 mm<br />

per year decreasing tg 3 mm per year due to the<br />

increasing stress <strong>on</strong> the frost fr<strong>on</strong>t with<br />

increasing depth. Therefore, it is anticipated<br />

that up to 150 mm of heave could occur over a<br />

20 to 30 year period beneath a pavement and<br />

insulatl<strong>on</strong> layer. It is seen therefore that<br />

the use of insulati<strong>on</strong> will not prevent gradual<br />

permafrost aggradati<strong>on</strong> in these circumstances.<br />

However, the rate of frost advance and the rate<br />

of frost heave are reduced to some extent.<br />

This predicti<strong>on</strong> is c<strong>on</strong>sidered to be <strong>on</strong>ly valid.<br />

in areas where there is almost no possibility<br />

of c<strong>on</strong>vective heat flow.<br />

0 s IO I5 20<br />

Ti rn e, yeors<br />

COARSC<br />

TAILINQS<br />

W"lO%<br />

TAILINBS<br />

Fig. 4 Frost Heave Due to Freezeback of<br />

Prethawed Area<br />

sequence of embankment tailings over dredged<br />

sandy silt was simulated, and the frost heave<br />

properties for both layers below. 2 m were<br />

assumedthesame.Thissimulati<strong>on</strong>indicated<br />

that up to 0.3 m of frost heave could be<br />

expected over a 20 year period following the<br />

start of freezeback at depth, During the same<br />

period, a frost depth of around 9 m would be<br />

predicted. As no frost heave data are available<br />

for the lower sandfsilt layers, this heave<br />

predicti<strong>on</strong> may be <strong>on</strong> the high side. In additi<strong>on</strong>,<br />

c<strong>on</strong>vective effects may reduce the of rate<br />

freezeback, or prevent it altogether. C<strong>on</strong>sidering<br />

that some of this frost heave would be<br />

of a relatively uniform nature and would be<br />

damped or* smoothed aut by the surface embankment<br />

layers, this was not felt,to be a significant<br />

drawback to the pre-thawing and possible<br />

re-freezing opti<strong>on</strong> c<strong>on</strong>sidered later. In either<br />

case, the predicted strain due to freezeback<br />

using these frost heave properties varies from<br />

about 4% to 2% at later times. This is c<strong>on</strong>siderably<br />

less than 10 to 20% thaw strain potential<br />

that is currently estimated for some<br />

frozen organic silt layers.<br />

C<strong>on</strong>siderati<strong>on</strong> was given to the possibility of<br />

using a relatively thick layer of polystyrene<br />

insulati<strong>on</strong> buried beneath the pavement surface<br />

thawing for preventi<strong>on</strong> effects.<br />

of In l<strong>on</strong>g order term to understand freezing and<br />

the<br />

possible effects insulati<strong>on</strong> would have <strong>on</strong> l<strong>on</strong>g<br />

term freezeback beneath a thawed or pre-thawed<br />

area, a simulati<strong>on</strong> of an unfrozen subgrade was<br />

carried out, incorporating a 100 mm layer of<br />

insulati<strong>on</strong> buried beneath 0.6 m of embankment<br />

fill and asphalt. This is the same profile and<br />

surface c<strong>on</strong>diti<strong>on</strong>s as usedintheprevious<br />

analysis with the additi<strong>on</strong> of the insulati<strong>on</strong><br />

layer.<br />

1322<br />

Thaw Settlement<br />

Thaw settlement has been particularly apparent<br />

during the warm years that occurred in the<br />

period of 1977 to 1983 inclusive, and the mean<br />

temperatures were c<strong>on</strong>siderably above the l<strong>on</strong>g<br />

term average value. The locati<strong>on</strong>s<br />

of these<br />

settlement areas appear to correlate reas<strong>on</strong>ably<br />

well with the presence of frozen organic silt,<br />

primarily within the undredged natural ground,<br />

havin a reas<strong>on</strong>ably high excess ice c<strong>on</strong>tent.<br />

The tkickness of coarse dredged t-ailings fill<br />

in these areas appears to be around 2.7 m. In<br />

order to study the historical resp<strong>on</strong>se of this<br />

profile to the temperature fluctuati<strong>on</strong>s that<br />

have occurred in the last 20 years, a simulati<strong>on</strong>'<br />

of thaw depth with time was undertaken.<br />

The profile was assumed to be initially stable<br />

permafrost, exposed to the m<strong>on</strong>th-by-m<strong>on</strong>th<br />

temperature fluctuati<strong>on</strong>s. .The moisture c<strong>on</strong>tent<br />

of the coarse dredged tailings was assumed to<br />

be 5% to the 2.7 m depth, although slight<br />

variati<strong>on</strong>s in this value would nor affect the<br />

outcome of the predicti<strong>on</strong>s to any great extent.<br />

The organic silt was initially frozen and a had<br />

water c<strong>on</strong>tent of 50%.<br />

Fig. 5 shows the predicted thaw depth versus<br />

time from 1967 to the present, During<br />

a<br />

typical year, the thaw depth is predicted to<br />

advance to the base of the coarse dredged tailings.<br />

The maximum predicted thaw depth during<br />

the years prior to 1977 is approximately 2.9 m.<br />

This implies that very little penetrati<strong>on</strong> of<br />

the thaw iantherm occurred into the organic<br />

silt. During the 7 warm years (1977 to 1983).<br />

the thaw line gradually increased to a maximum<br />

depth of about 3 m below ground surface, indicating<br />

an increase thaw penetrati<strong>on</strong> of<br />

approximately 0.2 m during this time period.<br />

The moisture cantents and visible excess ice<br />

c<strong>on</strong>tents in this organic silt layer suggest<br />

that a typical thaw strain value of 10 to 15%<br />

is quite reas<strong>on</strong>able for this layer (see Hanna,<br />

et. al. , 1983). If the incremental thaw depth<br />

of 0.2 m is multiplied by a thaw strain of<br />

around 15%, a thaw settlement of around 30 mm<br />

can be predicted.<br />

It is worth noting that the <strong>on</strong> East-West Runway<br />

between Stati<strong>on</strong> 9+00 to 14+00. approximately

Fig. 5<br />

Tlrne, years<br />

Predicted Thaw Depth vs.<br />

(1967-1987)<br />

30 mm of settlement occurred in the years 1983<br />

to 1986, This, in part, can be explained by<br />

the increased thaw depth and thaw strain mechanism<br />

described above. It should be noted that<br />

all of the thaw strain will not necessarily<br />

occur in the seas<strong>on</strong> in which the incremental<br />

thaw occurred, due to time-dependent sec<strong>on</strong>dary<br />

c<strong>on</strong>solidati<strong>on</strong> in the organic stlt deposit. It<br />

must also be acknowledged that some c<strong>on</strong>vective<br />

groundwater flow may have also c<strong>on</strong>tributed to<br />

settlement during the seven year warm period,<br />

together with other settlements occurring prior<br />

to that time. It appears that settlements that<br />

may cause noticeable distress to the runway,<br />

can be induced by increased thawing of<br />

as<br />

little as 0.3 m over a year so. or<br />

CONCLUSIONS<br />

C<strong>on</strong>ceptual design alternatives to correct the<br />

deformati<strong>on</strong> problems at the Nome Runway were<br />

presented in the order of increasing effort<br />

fromminimumsurfacerepairs to major improvement<br />

of the subsurface foundati<strong>on</strong> soil and<br />

rec<strong>on</strong>structi<strong>on</strong> of the runway surfaces and<br />

include the following (RhM C<strong>on</strong>sultants, 1987):<br />

1) Releveling the patching of surface depressi<strong>on</strong>s<br />

and c<strong>on</strong>structing a new pavement<br />

secti<strong>on</strong> in selected areas. Leave the<br />

subdrain system as is.<br />

Relevel and repave surface depressi<strong>on</strong>s<br />

after placement of insulati<strong>on</strong> board.<br />

Place new pavement system Fn selected<br />

areas. Modify subdrain system where<br />

appropriate to enhance subsurface drainage<br />

away from runway. Relocate Center Creek<br />

which crosses the East-West Runway.<br />

Thaw runway foundati<strong>on</strong> soils to bedrock<br />

designated areas (primarily undredged<br />

natural frozen ground). Relevel and<br />

c<strong>on</strong>struct new pavement structure. Modify<br />

drainage svstem as in Alternative 2.<br />

RelocaEe CeAter Creek.<br />

Prethaw runwav foundati<strong>on</strong> soils to bedrock<br />

in designaced areas, densify the<br />

designated areas to full depth utilizing<br />

dynamic compacti<strong>on</strong> or c<strong>on</strong>trolled blasting<br />

techniques, fill to grade and c<strong>on</strong>struct<br />

new pavement structure. Remove existing<br />

subdrain system and replace with perimeter<br />

subdrains. Relocate Center Creek.<br />

Same as Alternate 4. except densify full<br />

length of runways.<br />

Same as Alternate 5 plus insulate full<br />

length of runways.<br />

All six of the above alternatives will provide<br />

some improvement in runway performance.<br />

Alternates 1 and 2 are c<strong>on</strong>sidered to present<br />

further temporary soluti<strong>on</strong>s that do not addre<br />

the problems of time dependent subsurface<br />

foundati<strong>on</strong> soil thaw subsidence or embankment<br />

frost heave. Alternates 3 through 6 address<br />

the. poor foundati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s and offer<br />

various methods for minimizing runway deformati<strong>on</strong>.<br />

In order to assess the effectiveness of using<br />

insulati<strong>on</strong> to minimize thaw into the organic<br />

silt layer, B simulati<strong>on</strong> was carried out REFERENCES<br />

involving a 50 mm layer of insulati<strong>on</strong> and an<br />

organic silt permafrost layer overlain 2.7 by m Alaska Department of Transportati<strong>on</strong> and Publi<br />

of fill. This sequence was simulated over the<br />

Facilities, (1985). Nome Airport layout<br />

period from 1967 to the resent. The depth of<br />

plan. Internal Report.<br />

thaw was found to vary {etween about 1.5 and Arctic Envir<strong>on</strong>mental Informati<strong>on</strong> and Data<br />

2.1 m, or about 1 to 1.5 m below the insulati<strong>on</strong> Center (AEIDC), (1976). Alaska Regi<strong>on</strong>al<br />

layer. The depth of thaw did not penetrate to<br />

Profiles - Northwest Regi<strong>on</strong>, Volume V,<br />

the organic silt layer, and the 50 m insu-<br />

Univ. of Alaska.<br />

lati<strong>on</strong> layer effectively reduced the thaw<br />

Brazo, G., (1982). Engineering geology and<br />

depths by about 1 m. The insulati<strong>on</strong> is partic- soils report, Nome Runway Repairs. Alask<br />

ularly effective in reducing the depths of thaw DOTIPF.<br />

due to c<strong>on</strong>ductive acti<strong>on</strong>, and may be c<strong>on</strong>sidered Hanna, A. et al., (1983). Alaska Highway Gas<br />

in areas where groundwater flow is not c<strong>on</strong>-<br />

Pipeline (Yuk<strong>on</strong> Secti<strong>on</strong>) Thaw Settlement<br />

sidered a significant heat transfer comp<strong>on</strong>ent. Design Approach, Proc. 4th Intl.<br />

<strong>Permafrost</strong> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, Fairbanks.<br />

Johns<strong>on</strong>, E.G., (1986). Ceotechnical report,<br />

investigati<strong>on</strong> and analysis of the Nome<br />

Runway settlement problems, Alaska,<br />

DOTIPF.<br />

Nix<strong>on</strong>, J.F., (1987). Pipeline frost heave<br />

predicti<strong>on</strong>s using the segregati<strong>on</strong> potential<br />

frost heave method, Proc. ASME 6th<br />

Intl. Symposium <strong>on</strong> Offshore Mechanical<br />

and Arctic Engineering.<br />

RhM C<strong>on</strong>sultants, Inc. (1987). Nome Airport<br />

Runway Repair Study, Vol. I, 11, 111.<br />

Prepared for the Alaska, DOT/PF.<br />

Sainesbury, C.L., Hummel. C.L.. and Huds<strong>on</strong>,<br />

T., (1972). Rec<strong>on</strong>naissance geologic map<br />

of the Nome Quadrangle, Seward Peninsula,<br />

AK, U.S.G.S. open-file report.<br />

1323

PHYSICAL MODEL STUDY OF ARCTIC PIPELINE SETTLEMENT<br />

T.S. Vins<strong>on</strong>l and AX. Palmer2<br />

'Oreg<strong>on</strong> State University, Corvallis, OR 97331, USA<br />

2Andrew Palmer and Associates Ltd., L<strong>on</strong>d<strong>on</strong>, England SWlP 1QF<br />

SYNOPSIS: A physical model study was c<strong>on</strong>ducted to investigate the effect of (1) arching and lateral<br />

load transfer, and (2) soil/pipe interacti<strong>on</strong> phenomena <strong>on</strong> arctic submarine pipeline settlements.<br />

Typical field c<strong>on</strong>diti<strong>on</strong>s were represented to be a 75 cm diameter pipeline, with a 1.6 cm wall. at a<br />

burial depth of 3.0 m, underlain by ice-rich permafrost at a depth of 8.5 m. With time, the warm<br />

Oil in the pipeline may thaw the ice-rich permafrost to produce settlements of approximately 0.3 to<br />

0.9 m. Based <strong>on</strong> an analysis of the test results obtained in the model study, pipeline displacements<br />

were observed to increase as the width of the settlement mass increased and the depth to the<br />

settlement mass decreased; centerspan displacements of the pipeline were substantially greater than<br />

quarterspan displacements; surface settlements directly above the pipeline were less than surface<br />

settlements over the settlement mass adjacent to the pipeline.<br />

INTRODUCTION<br />

It is likely in the future that submarine pipelines<br />

will be c<strong>on</strong>str,ucted offshore of the north<br />

coast of Alaska. One of the areas where pipelines<br />

may be needed is Harris<strong>on</strong> Bay. Surveys<br />

have shown that subsea permafrost exists under<br />

the bay out to a water depth of at least 25 m<br />

(some 20 km from the shoreline) and that the<br />

permafrost boundary may be as shallow as 5 m<br />

below the mudline. A pipeline to shore will be<br />

at a depth of approximately 3 to 5 m below the<br />

mudline to protect it from ice scour and the<br />

pipeline trench may be backfilled. Thermal<br />

calculati<strong>on</strong>s indicate that a warm pipeline may,<br />

in time, thaw permafrost several tens of meters<br />

below. If the permafrost is ice-rich, thaw<br />

settlement will occur and will be followed by<br />

deformati<strong>on</strong>s within the unfrozen seabed soil<br />

that surrounds the pipeline. The pipeline will<br />

deform with the soil, and there is a possibility<br />

that the deformati<strong>on</strong> may be severe enough<br />

to damage the pipeline. To avoid damage to the<br />

pipeline it may be necessary to heavily insulate<br />

the pipeline, to prethaw the permafrost, or<br />

to support the pipeline independently, but<br />

these measures are likely to be expens,ive.<br />

An analysis of the influence of thaw c<strong>on</strong>solidati<strong>on</strong><br />

settlements <strong>on</strong> pipeline stresses and deformati<strong>on</strong>s<br />

will be part of the design process.<br />

It is essential that this analysis not be unduly<br />

oversimplified or overc<strong>on</strong>servative. There<br />

is a risk that an oversimplified analysis may<br />

generate pessimistic c<strong>on</strong>clusi<strong>on</strong>s which in turn<br />

would lead to the adopti<strong>on</strong> of costly and difficult<br />

c<strong>on</strong>structi<strong>on</strong> alternatives (such as prethawing).<br />

There is a sec<strong>on</strong>dary risk that regulatory<br />

authorities may adopt an unduly c<strong>on</strong>servative<br />

design approach, and that it may become<br />

part of regulati<strong>on</strong>s.<br />

One of the important factors in a pipeline settlement<br />

analysis is the extent to which the<br />

pipeline follows the thaw strain in the soil<br />

beneath. More directly, it is important to<br />

know if a thaw settlement of (say) 0.1 m in the<br />

thawed regi<strong>on</strong> necessarily induces 0.1 m movement<br />

in the soil immediately under the pipeline,<br />

or in the pipeline itself. Preliminary<br />

work by Walker et al. (1983), indicates there<br />

ace several factors that mitigate the effect <strong>on</strong><br />

the pipeline. For example, the frozen ice-rich<br />

regi<strong>on</strong> has a limited horiz<strong>on</strong>tal extent, and<br />

thaw c<strong>on</strong>solidati<strong>on</strong> leads to settlement in the<br />

z<strong>on</strong>e above (surrounding the pipeline) which is<br />

partially c<strong>on</strong>strained by the resistance to deformati<strong>on</strong><br />

of the soil to either side of the<br />

z<strong>on</strong>e. This arching phenomen<strong>on</strong> transfers the<br />

weight of the pipeline and the soil around it<br />

laterally, so that vertical movements are<br />

smaller than they would be if the thawed regi<strong>on</strong><br />

were of infinite extent. Further, the stiffness<br />

of the pipeline itself transfers loads<br />

horiz<strong>on</strong>tally, and further reduces settlement.<br />

Studies of the Interprovincial Norman Wells to<br />

Zama Lake pipeline (Nix<strong>on</strong> et a1 ., 1984) have<br />

reached a similar c<strong>on</strong>clusi<strong>on</strong>.<br />

OBJECTIVES AND SCOPE OF THE RESEARCH PROGRAM<br />

The objective of the research program reported<br />

herein is to investigate the effect of (1)<br />

arching and lateral load transfer, and (2)<br />

soil/pipe interacti<strong>on</strong> phenomena, <strong>on</strong> submarine<br />

pipeline settlements, using physical models<br />

tested <strong>on</strong> a centrifuge. The scope of the research<br />

program is limited to the results obtained<br />

in ten centrifuge tests c<strong>on</strong>ducted at the<br />

Cambridge Geotechnical Centrifuge Facility,<br />

Cambridge, England. The test results obtained<br />

in the program are reported herein. An<br />

analysis of the test results, including a<br />

comparis<strong>on</strong> of the physical model results to the<br />

results of an analytical model, will be made in<br />

the future.<br />

1324

~ ~~~<br />

CENTRIFUGAL MODELING IN GEOTECHNICAL ENGINEERING<br />

To accurately model soil/structure interacti<strong>on</strong><br />

phenomena, either analytically or physically,<br />

the stress-strain-strength dependency of the<br />

soil comprising the model <strong>on</strong> the overall stress<br />

state must be addressed. To accomplish this in<br />

a physical model study, a direct equivalence<br />

between the state of stress of a given soil<br />

element at corresp<strong>on</strong>ding points in the fullscale<br />

structure and the model must be achieved.<br />

This will not be the case in c<strong>on</strong>venti<strong>on</strong>al smallscale<br />

modeling in a <strong>on</strong>e gravity envir<strong>on</strong>ment, if<br />

the same materials are used in the model as in<br />

the full-scale structure, unless a model the<br />

same size as the full-scale structure is c<strong>on</strong>structed.<br />

Alternatively, the centrifugal modeling<br />

technique may be employed in which a physical<br />

model is c<strong>on</strong>structed which represents the<br />

field or prototype c<strong>on</strong>diti<strong>on</strong> (i.e ., the same<br />

geotechnical material as the prototype, the<br />

same geometry, the same boundary c<strong>on</strong>diti<strong>on</strong>s,<br />

etc.) to as great an extent as possible. Following<br />

fundamental principles, the model is<br />

c<strong>on</strong>structed at a scale of 1 to n, so that the<br />

length, L, in the model corresp<strong>on</strong>ds to the<br />

length nL in the prototype. The physical model<br />

is then rotated in a centrifuge, with the model<br />

oriented such that the outward radial directi<strong>on</strong><br />

in the centrifuge corresp<strong>on</strong>ds to the vertical<br />

directi<strong>on</strong> in the prototype, at an angular velocity<br />

chosen so that the radial accelerati<strong>on</strong> in<br />

the model is ng, where g is the gravitati<strong>on</strong>al<br />

accelerati<strong>on</strong>. Under this c<strong>on</strong>diti<strong>on</strong> the stresses<br />

and strains induced in the model are the same<br />

as those in the prototype and the settlements<br />

or displacements are scaled in the ratio of 1<br />

to n.<br />

Centrifugal modeling has firmly estab-<br />

lished its place in geotechnical engineering<br />

over the past 15 years and has been employed to<br />

study ice-structure interacti<strong>on</strong> and ice ridge<br />

building (Vins<strong>on</strong> and Wurst, 1985; Clough, et<br />

al., 1986; Clough and Vins<strong>on</strong>, 1986; Palmer, et<br />

a1 ., 1986) , as well as a great number of<br />

c<strong>on</strong>venti<strong>on</strong>al geotechnical engineering problems.<br />

DESIGN CONSIDERATIONS ASSOCIATED WITH SUBMARINE<br />

SOIL/PIPE SETTLEMENT INTERACTION PHENOMENA<br />

The design of submarine pipelines for settlements<br />

associated with thawing ice-rich subsea<br />

permafrost is based up<strong>on</strong> the maximum differential<br />

settlement that may occur at settlement<br />

transiti<strong>on</strong> z<strong>on</strong>es in a submarine deposit. Differential<br />

thaw settlements in subsea permafrost<br />

deposits may be caused by (1) n<strong>on</strong>uniform thaw<br />

depths, or (2) variati<strong>on</strong>s in thaw settlement<br />

soil properties.<br />

For l<strong>on</strong>g span settlement z<strong>on</strong>es'the maximum<br />

pipeline stresses are obviously located in the<br />

vicinity of the transiti<strong>on</strong> boundary; in the<br />

center of the settlement z<strong>on</strong>e, distress to the<br />

pipe is minimized owing to the minimum curvature<br />

of the pipe in this regi<strong>on</strong>. As the settlement<br />

z<strong>on</strong>e decreases in lenyth, the pipe<br />

stiffness becomes increasingly more important.<br />

For short span settlement .z<strong>on</strong>es, the pipe can<br />

bridge the settlement trough and pipe distress<br />

will again be minimized. Allowable soil settlement<br />

is therefore unlimited for short spans.<br />

Between the l<strong>on</strong>g and short span c<strong>on</strong>diti<strong>on</strong> there<br />

is a "critical" span, i.e., a span length for<br />

which distress to the pipeline is maximized<br />

owing to a maximum curvature of the pipeline.<br />

The minimum allowable settlement occurs at the<br />

critical span. An intermediate allowable soil<br />

settlement occurs at l<strong>on</strong>g spans. Nyman (1983)<br />

has determined that the minimum and intermediate<br />

allowable settlement, and the difference<br />

between the lntermediate and minimum allowable<br />

Settlement, increases as the soil cover over<br />

the pipe decreases. Also, the critical span<br />

increases as the depth of soil cover increases.<br />

Deoth<br />

crn at<br />

62.51~ 969<br />

2.5 1.6<br />

5.0<br />

7.5<br />

10.0<br />

12.5<br />

15.0<br />

3.2<br />

4.8<br />

6.4<br />

7.9<br />

9.5<br />

Fig. 1<br />

trctic Ocean<br />

I<br />

3rn<br />

0.'<br />

-<br />

Worst case<br />

IBPF<br />

rn<br />

4.<br />

Standard case<br />

IBPF<br />

zz77-<br />

Pipe Characteristics<br />

.75 cm 9 0.0.<br />

1.6 cm wall thickness<br />

I = 2.6 X lo5 cm4<br />

Oil temperature : 71'C<br />

Oper. press.=10.3 MPa<br />

Estlmotes:<br />

Locked-in load = 1.9~10~ KIPS<br />

Crlt lcol soan = 40 m<br />

-<br />

IT<br />

m Soil Profile-Typical<br />

N<strong>on</strong>-ice b<strong>on</strong>ded permafrost<br />

permafrost (IBPF)"<br />

E, = 5 to 15%<br />

- I.<br />

I 1 Well-b<strong>on</strong>ded frozen sand<br />

E, E 5%<br />

*Typically poorly-b<strong>on</strong>ded<br />

visible ice.<br />

silt Wth<br />

IdealiFati<strong>on</strong> of Field C<strong>on</strong>ditiG:r'2<br />

IDEALIZATION OF FIELD CONDITIONS<br />

An idealizati<strong>on</strong> of representative field c<strong>on</strong>diti<strong>on</strong>s<br />

for arctic offshore pipelines is shown in<br />

Fig. 1. A typical pipeline may be 75 cm outslde<br />

diameter with a 1.6 cm wall. The pipeline<br />

will carry oil at an operating pressure of 10.3<br />

MPa. The pipeline will be buried at a depth of<br />

3 m. The soil c<strong>on</strong>diti<strong>on</strong>s at the site are typically<br />

n<strong>on</strong>-ice b<strong>on</strong>ded permafrost (typically<br />

si1 t) overlying poorly ice-b<strong>on</strong>ded permafrost<br />

(typically silt with visible ice wlth thaw<br />

strains from 5 to 158) overlying well-b<strong>on</strong>ded<br />

frozen sands (with thaw strains of 5%). As a<br />

"worst" case the ice b<strong>on</strong>ded permafrost may be<br />

as shallow as 5.5 m, but a more representative<br />

depth may be 8.5 m. The critical span €or the<br />

pipeline is estimated to be 40 m. .For settlements<br />

occurring at 8.5 m, the critical span<br />

length corresp<strong>on</strong>ds to an approximate settlement<br />

z<strong>on</strong>e span length of 33.5 m (assuming a settlement<br />

spread of 0.7 (horiz.) to 1 (vert.).<br />

1325

Based <strong>on</strong> a preliminary analysis of the thermal<br />

regime associated with the c<strong>on</strong>diti<strong>on</strong> represented<br />

in Fig. 1 the depth of the thaw bulb<br />

beneath the 5.5 m level will be 9 m after 20<br />

years with 2.5 to 5 .O cm of insulati<strong>on</strong>. If<br />

ice-rich permafrost occurs at 8.5 m with thaw<br />

strains from 5 to 15%, the settlement beneath<br />

the pipeline will be approximately 0.3 to 0.9<br />

m. Surrounding the thawed mass is frozen iceb<strong>on</strong>ded<br />

permafrost and overlying n<strong>on</strong>-ice-b<strong>on</strong>ded<br />

permafrost. The pipeline, filled with warm<br />

oil, gpans the mass of thawed ice-b<strong>on</strong>ded permafrost,<br />

the length of which, al<strong>on</strong>g the axis of<br />

the pipeline, varies according to the actual<br />

geometry of the ice-b<strong>on</strong>ded permafrost in the<br />

field. Prom the standpoint of pipeline design<br />

and analysis, the length of the thawed mass is<br />

presumed to be associated with the critical<br />

span for the pipe. Away from the settlement<br />

mass, the pipeline is c<strong>on</strong>sidered to be infinitely<br />

l<strong>on</strong>g.<br />

It is not possible to create a physical model<br />

that exactly duplicates the field c<strong>on</strong>diti<strong>on</strong><br />

described above. C<strong>on</strong>sequently, it is necessary<br />

to idealize the field c<strong>on</strong>diti<strong>on</strong>. It should be<br />

recognized a priori that <strong>on</strong>ly finite pipeline<br />

lengths can be employed in a centrifuge model<br />

c<strong>on</strong>tainer. Further, from an experimental<br />

standpoint, it would be difficult to create a<br />

mass of ice-b<strong>on</strong>ded frozen material and thaw a<br />

porti<strong>on</strong> of the mass with warm oil flowing<br />

through a model pipeline. In fact, from a phenomenological<br />

standpoint, it is not necessary<br />

to produce settlement beneath the pipeline with<br />

a thawed mass; it is <strong>on</strong>ly necessary to have a<br />

mass of material that will settle with time beneath<br />

the pipeline.<br />

As a "first" physical model idealizati<strong>on</strong> of the<br />

field c<strong>on</strong>diti<strong>on</strong>, the thawed mass may be represented<br />

with a compressible saturated clay block.<br />

The clay mass will settle with time under the<br />

high inertial accelerati<strong>on</strong>s created in the<br />

centrifuge. Also, the clay mass geometry is<br />

easily changed to allow different settlement<br />

mass geometries to be investigated in an experimental<br />

program. The incampressible frozen<br />

ice-b<strong>on</strong>ded permafrost surrounding the settlement<br />

mass, and overlying n<strong>on</strong>-ice b<strong>on</strong>ded permafrost,<br />

may be represented with a cohesi<strong>on</strong>less<br />

soil, for example, sand. Sand will experience<br />

<strong>on</strong>ly minor settlement under high inertial<br />

accelerati<strong>on</strong>s and will not settle with time.<br />

Further, sand is easily placed and saturated.<br />

The dimensi<strong>on</strong>s of the model pipe (i.e., diameter<br />

and wall thickness) must be scaled down by<br />

a factor "n". The model pipes should be made<br />

of steel to reflect the field c<strong>on</strong>diti<strong>on</strong> and<br />

filled with oil. If the ends of the pipe are<br />

not fixed at a specified length in the model<br />

c<strong>on</strong>tainer, they will assume an unknown degree<br />

of fixity in the soil surrounding the pipe ends<br />

during an experiment. Recognizing that eventually<br />

the results from the physical model study<br />

may be used to validate an analytical model, it<br />

is desirable to set the c<strong>on</strong>diti<strong>on</strong>s at the ends<br />

of the model pipe. The easiest c<strong>on</strong>diti<strong>on</strong> to<br />

set ia a fixed-end (i .e., no rotati<strong>on</strong> of the<br />

plpe end) .<br />

CAMBRIDGE GEOTECHNICAL CENTRIFUGE FACILITY<br />

The Cambridge Geotechnical Centrifuge Facility<br />

(CGCF).was c<strong>on</strong>structed in 1994, The facility<br />

has been in c<strong>on</strong>tinuous operati<strong>on</strong> since that<br />

time. The general test procedure associated<br />

with a centrifuge model study involves building<br />

a model which represents the field situati<strong>on</strong> as<br />

closely as possible. Next the model in a steel<br />

c<strong>on</strong>tainer is attached to the swinging bucket at<br />

a radius of 4 m from the hub of the centrifuge.<br />

Counterbalance weight is added to the bucket <strong>on</strong><br />

the opposite end of the arm to maintain a gyrascopically<br />

balanced c<strong>on</strong>figurati<strong>on</strong>. The centrifuge<br />

operator then accelerates the centrifuge<br />

to the revoluti<strong>on</strong>s per minute (rpm) corresp<strong>on</strong>ding<br />

to the desired inertial accelerati<strong>on</strong> of the<br />

test. The instrumentati<strong>on</strong> <strong>on</strong> board the model<br />

c<strong>on</strong>tainer is m<strong>on</strong>itored remotely during the test.<br />

The model c<strong>on</strong>tainer and test system employed in<br />

the research program is shpwn schematically in;<br />

Fig. 2. The model c<strong>on</strong>tainer and test system<br />

c<strong>on</strong>sists of an 85 cm diameter, 40 cm high steel<br />

cylinder filled with saturated soil to a depth<br />

of 30 cm. The soil deposit is comprised of a<br />

gravel layer approximately 5 cm in depth underlying<br />

a fine sand approximately 25 cm in depth.<br />

Embedded within the fine sand are clay blocks,<br />

foundati<strong>on</strong> plates, pipe clamps, and model<br />

pipes. Tubular stainless steel extensi<strong>on</strong> rods,<br />

1.7 mn diameter, are attached to the model<br />

pipe, foundati<strong>on</strong> plates, or settlement plates<br />

at settlement points. LVDTs were used to m<strong>on</strong>itor<br />

model pipe soil surface settlement, and<br />

foundati<strong>on</strong> plate movement. Druck miniature<br />

pore water pressure (pwp) transducers were<br />

employed to m<strong>on</strong>itor pore pressure in the compressible<br />

clay blocks<br />

TEST RESULTS<br />

Ten tests were c<strong>on</strong>ducted st the CGCF during the<br />

period March to August, 1984. To c<strong>on</strong>duct a<br />

"modeling of modela" study, two model pipe sizes<br />

were c<strong>on</strong>sidered. Both 7.9 nun O.D. x 0.024 nun<br />

wall thickness and 12.1 mm O.D. x 0.04 nun wall<br />

thickneas stainlesa steel tubular secti<strong>on</strong>s were<br />

commercially available. Given the representative<br />

field c<strong>on</strong>diti<strong>on</strong> selected in the study (re<br />

Fig. 1) for which the full-scale pipeline is 75<br />

cm O.D. x 1.6 cm wall thickness, the ratios of<br />

the full-scale to model pipeline dimensi<strong>on</strong>s<br />

suggest that inertial accelerati<strong>on</strong>s of 96 (re<br />

7.9 mm O.D.) and 62.5 g (re 12.2 nun O.D.) would<br />

be appropriate in the test program. These<br />

levels of inertial accelerati<strong>on</strong> further suggest<br />

the model depth scale given in Fig. 1. For the<br />

7.9 mm model pipe, the depth of overburden is<br />

3.2 cm and for the 12.1 nun, it is 4.9 cm.<br />

An example of the test results from the research<br />

program is given in Fig. 3. During the<br />

c<strong>on</strong>duct of a test, the following resp<strong>on</strong>ses of<br />

the physical model were m<strong>on</strong>itored: (1) model<br />

pipe displacements at center and yuarterspan,<br />

(2) soil surface settlements, (3) porewater<br />

pressure dissipati<strong>on</strong> in the clay blocks, ( 4)<br />

centerspan strains in the model pipe, and (5)<br />

inertial accelerati<strong>on</strong> of the model.<br />

1326

mm<br />

-<br />

(0) pipe displacements C<br />

-<br />

-,<br />

-10.0 A - Centerspan<br />

-12.0<br />

-14.0<br />

B - Quartartpan<br />

C - Fdn Plate<br />

0 - Fdn Plate<br />

I<br />

rnstrnldiv<br />

4b) centerspan strain<br />

3.79 + (c) surface settlement -<br />

mm/dlv - -<br />

(dl porewater pressur<br />

(a) PLAN VIEW<br />

A PWP Transducer<br />

Settlement point<br />

N Strain pages<br />

I<br />

I<br />

LVDT bar sypport<br />

Fig. 3<br />

Example of Test Results<br />

Flg. 2<br />

Model C<strong>on</strong>tainer and Test System<br />

QUALITATIVE EVALUATION OF TEST'RESULTS<br />

Test 1 was c<strong>on</strong>ducted to evaluate test system<br />

deflectl<strong>on</strong>s, soil bed settlements and transducer<br />

performance under high inertial accelerati<strong>on</strong>s.<br />

The results from Test 1 indicate that<br />

approximately 2 nun displacement occurs for all<br />

comp<strong>on</strong>ents of the test system. Approximately 1<br />

mm occurs from 0 to 20 g inertial accelerati<strong>on</strong><br />

and 1 mm occurs from 20 to 100 g. This magnitude<br />

of overall settlement is acceptable.<br />

Test 2 was c<strong>on</strong>ducted to evaluate pipe deflecti<strong>on</strong>s<br />

and fixity €or free span c<strong>on</strong>diti<strong>on</strong>s.<br />

Test 3 was similar but .a surcharge was placed<br />

<strong>on</strong> the model pipes to simulate the field<br />

overburden c<strong>on</strong>diti<strong>on</strong>. The physical model<br />

employed c<strong>on</strong>sisted of dry sand with three model<br />

pipes spanning an excavati<strong>on</strong> in the sand.<br />

Knowing the span length and pipe stiffness,<br />

mass/unit length, and the pipe deflecti<strong>on</strong>s at<br />

several inertial accelerati<strong>on</strong>s, it may be possible<br />

to determine the degree of fixity at the<br />

face of the excavati<strong>on</strong>. Further, the results<br />

from the test provide informati<strong>on</strong> <strong>on</strong> pipeline<br />

resp<strong>on</strong>se wlth no soil overburden load and no<br />

eoil/pipe interacti<strong>on</strong> phenomena in the settlement<br />

z<strong>on</strong>e. The freespan test results appear to<br />

be reas<strong>on</strong>able. As expected, the net plpe dlsplacements<br />

were appreciably less for the pipe<br />

with no surcharge compared to the dlsplacements<br />

for the pipe with a surcharge. The post-Cllght<br />

stiffnesses of the pipes with the surcharges<br />

were approximately equal to the stiffnesses of<br />

the model pipes with no surcharge attached.<br />

Test 4 was c<strong>on</strong>ducted to evaluate pipe detlecti<strong>on</strong>s<br />

at critical span for two settlement mass<br />

widths, and the suitability of c.Lay blocks to<br />

produce settlements beneath model pipelines.<br />

The physical model employed c<strong>on</strong>sisted of saturated<br />

sand with two 7.9 mm diameter model<br />

pipes. Compressible clay blocks were placed<br />

beneath the model pipes to produce settlements<br />

under the high inertial accelerati<strong>on</strong>s for the<br />

test. The wider clay block, 25.4 cm at 96 g<br />

reflected the approximate width of the thaw<br />

bulb that would occur for the representative<br />

field c<strong>on</strong>diti<strong>on</strong>s (re Fig. 1). The narrow<br />

1327

lock, 8.9 cm, reflected a width of block equal<br />

to the depth of overburden to the block level.<br />

A comparis<strong>on</strong> of the pipe deflecti<strong>on</strong>s for the<br />

two c<strong>on</strong>diti<strong>on</strong>s allows a relative assessment to<br />

be made of arching phenomena at two feature<br />

widths, at critical span. Test 5 was c<strong>on</strong>ducted<br />

to evaluate pipe deflecti<strong>on</strong>s at subcritical<br />

span for two feature widths. This test is<br />

essentially the same as Test 4 except 12.2 mm<br />

diameter model pipes were employed with a feature<br />

span length less than critical.<br />

The compressible clay blocks employed in Tests<br />

4 and 5 produced settlements under the model<br />

pip@s, as anticipated. The overall durati<strong>on</strong> of<br />

the flight was limited to 4 hours which proved<br />

veuy satisfactory with respect to c<strong>on</strong>ducting<br />

<strong>on</strong>e test during <strong>on</strong>e work day. For both tests,<br />

model pipeline displacements associated with<br />

settlements of wide blocks (approximately reflecting<br />

the width of the thaw bulb that would<br />

occur €or the field c<strong>on</strong>diti<strong>on</strong>s) may be compared<br />

to pipe displacements that are associated with<br />

settlemen,ts of narrow blocks. The test results<br />

suggest that over the range of widths c<strong>on</strong>sidered,<br />

there is a minor reducti<strong>on</strong> in pipeline<br />

displacement as the feature width narrows.<br />

Test 6 was c<strong>on</strong>ducted to evaluate pipe deflecti<strong>on</strong>s<br />

at critical span for two settlement mass<br />

widths and to verify reproducibility of the<br />

test results. The physical model employed c<strong>on</strong>sisted<br />

of saturated sand with two 7.9 nun diameter<br />

model pipes underlain by compressible clay<br />

blocks. The width and depth of <strong>on</strong>e of the settlement<br />

masses, 8.9 cm, was identical to <strong>on</strong>e of<br />

the masses employed in Test 4. The width of<br />

the other mass 4.5 cm was narrower than the<br />

widths c<strong>on</strong>sidered in Test 4. The results of<br />

the test, when combined with Test 4, allow a<br />

relative assessment to be made of (1) arching<br />

phenomena at three feature widths, at critical<br />

span, and (2) reproducibility of test results.<br />

The results from Tests 4 and 6 may be compared<br />

to assess the reproducibilitiy of the test results.<br />

4t a feature width and depth of 8.9 cm,<br />

and length of 34.9 cm, Tests 4 and 6 indicated<br />

net maximum centerspan pipeline displacements<br />

of 11.3 and 10.9 mm, respectively. This close<br />

comparisi<strong>on</strong> is indeed encouraging. Also, pipeline<br />

displacements for an extremely narrow feature<br />

width c<strong>on</strong>sidered in Test 6 may be compared<br />

to the results obtained in Test 4 , As expected,<br />

net pipeline displacement c<strong>on</strong>tinued to<br />

decrease as the feature width decreased. For<br />

feature widths of 4.5, 8.9, and 25.4 cm, net<br />

maximum centerspan displacements were 4.3, 11.1<br />

(ave.), and 14.5 mm, respectively.<br />

Test 7 was c<strong>on</strong>ducted to evaluate the influence<br />

of the fixity length <strong>on</strong> pipe deflecti<strong>on</strong>s at subcritical<br />

span for a wide settlement mass. The<br />

physical model employed c<strong>on</strong>sisted of saturated<br />

sand with three 12.2 mm model pipes employed<br />

with a feature span length less than critical.<br />

Three pipe clamp grip spacings (52.8, 56.0, and<br />

69.3 cm) were employed to determine if the grip<br />

spacing (i.e. fixity length) influenced pipe<br />

resp<strong>on</strong>se. The 12.2 mm pipes at 62.5 g were<br />

c<strong>on</strong>sidered to be a "worst case" c<strong>on</strong>diti<strong>on</strong>. For<br />

this case, the fixity point is closest to the<br />

feature edge and, therefore, would have the<br />

greatest effect in pipeline resp<strong>on</strong>se if, indeed,<br />

an effect was to be observed. With the<br />

7.9 mm model pipes, the fixity point is further<br />

away from the feature edge and, as a c<strong>on</strong>sequence,<br />

if the fixity length was not important<br />

for the 62.5 g tests., it should not be important<br />

.for the 96 g tests. Finally, in this test<br />

the drainage c<strong>on</strong>diti<strong>on</strong>s for the clay blocks<br />

were changed from double to single drainage.<br />

This change results in a fourfold increase in<br />

the time required to achieve a given degree of<br />

c<strong>on</strong>solidati<strong>on</strong> in the clay block and, hence,<br />

settlement.<br />

The results from Test 7 indicate that differences<br />

in the pipe clamp grip spacing do not<br />

have an appreciable influence <strong>on</strong> model pipe ,<br />

displacements. For the three grip spacings<br />

c<strong>on</strong>sidered, the net maximum centerspan pipe<br />

displacements were 20.4) 21.5 and 19.6 mm, respectively.<br />

The use of a singly drained block<br />

resulted in extremely good c<strong>on</strong>trol of the time<br />

rate of settlement of the clay block and they<br />

were used for the remainder, of the test program;<br />

Test 8 was c<strong>on</strong>ducted to evaluate pipe deflecti<strong>on</strong>s<br />

at critical span at two feature depths<br />

for a given width. The physical model employed<br />

c<strong>on</strong>sisted of 7.9 mm model pipes underlain by<br />

compressible clay blocks at depths of 5.3 and<br />

17.9 cm. The width of the masses, 8.9 cm was<br />

equal to the width of <strong>on</strong>e mass used in Tests 4<br />

and 6. C<strong>on</strong>sequently, the test results, when<br />

combined with Tests 1 and 6, allow a relative<br />

assessment to be made of arching phenomena at<br />

three feature depths.<br />

The results from Test 8, when compared to<br />

results from Tests 4 and 6 indicate that net<br />

centerspan pipeline displacements decrease. with<br />

an increase in the depth of the feature, For<br />

feature depths of 5.3, 8.9, and 17.9 cm, net<br />

maximum centerspan deflecti<strong>on</strong>s were 12.4, 11.1<br />

(ave.), and 6.5 nun, respectively.<br />

Test 9 was c<strong>on</strong>ducted to compare pipe deflecti<strong>on</strong>s<br />

associated with settlement of ice-rich and clay<br />

blocks, The physical model employed c<strong>on</strong>sisted<br />

of saturated sand with two 12.2 mm model pipes<br />

underlain by a compressible clay block (Bay A)<br />

and an ice-rich block (Bay C1. A heat plate<br />

was placed beneath the ice-rich block to thaw<br />

the block. It was recognized that the time<br />

rate and magnitude of settlement for the icerich<br />

block would be different than for the clay<br />

block. If observed pipe deflecti<strong>on</strong>s were found<br />

to be equal at corresp<strong>on</strong>ding block settlements,<br />

then it may be c<strong>on</strong>cluded that the nature of the<br />

settlement mass (i.e. clay versus ice-rich<br />

block) does not influence arching phenomena in<br />

the z<strong>on</strong>e of the pipeline. Settlement at the<br />

block level was not measured. C<strong>on</strong>sequently,<br />

the best indicator of block settlement is the<br />

surface settlement measured over the block. At<br />

comparable surface settlements for the clay and<br />

ice-rich blocks, the net centerspan model pipe<br />

displacements were 4.0 and 5.0 mm, respectively.<br />

This comparis<strong>on</strong> does not necessarily reflect<br />

the c<strong>on</strong>sequences of settlements that occurred<br />

owing to thaw of the ice-rich block prior to<br />

mounting the model c<strong>on</strong>tainer <strong>on</strong> the centrifuge.<br />

Test 10 was c<strong>on</strong>ducted to compare pipe deflecti<strong>on</strong>s<br />

at three span lengths for a wide feature.<br />

The physical model employed c<strong>on</strong>sisted of saturated<br />

sand with three 7.9 mm model pipes underlain<br />

by a large compressible clay block. The<br />

1328

settlement mass span lengths were 24.0, 46.0,<br />

and 34.9 cm. The test results allow an evaluati<strong>on</strong><br />

to be made of the critical span c<strong>on</strong>cept.<br />

Also the results at the assumed critical span<br />

for the pipeline, 34.9 cm may be compared to the<br />

wide feature, 25.4 cm results from Test 4 to<br />

allow an approximate assessment of the reproducibility<br />

of the test results to be made. Finally,<br />

the results from the shortest span length<br />

24.0 cm may be compared to the results obtained<br />

in Test 5 to make an approximate assessment of<br />

"modeling of models" in the test program.<br />

The results from Test 10 indicate that net maximum<br />

centerspan displacements are 8.2, 16.6,<br />

and 18.0 mm for feature lengths of 24.0, 34.gr<br />

and 46.0 cm, respectively. These results suggest<br />

that the "critical span" employed in the<br />

test program may not be correct. Further analysis<br />

of the results from Teat LO are necessary<br />

before a c<strong>on</strong>clusive statement can be made.<br />

At a span length of 34.9 cm, the results from<br />

Test 10 may be compared to the results from<br />

Test 4 to further assess reproducibility of the<br />

results. For a feature width of 25.4 cm (and<br />

span length of 34.9 cm) , net maximum centerspan<br />

displacements were 14.5 nun in Test 4 compared<br />

to 16.6 mm in Test 10.<br />

An approximate assessment of "modeling of<br />

models" may be made by compkring the results<br />

from Test 10 at a span length of 24.0 cm to the<br />

results from Test 5 at a span Length of 37.6 cm<br />

and a feature width of 30.0 cm. At these model<br />

span lengths both tests reflect a span length<br />

in the field of 23 m. The ratio of net maximum<br />

centerspan displacements is 12.9 mm (e37.6 cm)/<br />

8.2 mm (e24.0 cm) = 1.57. This may be compared<br />

to the ratio of inertial accelerati<strong>on</strong>s, namely,<br />

96 g/62.5 g = 1.54. Clearly, there is a very<br />

favorable comparis<strong>on</strong>.<br />

When the settlement was induced by c<strong>on</strong>solidati<strong>on</strong><br />

at a shallow depth below the pipeline, the<br />

surface displacements immediately above the<br />

pipeline were less than the displacements <strong>on</strong><br />

either side. The relative settlement profile<br />

is similar to the displacement profile that<br />

occurs when a pipe is pulled upwards out of the<br />

seabed. In both cases, the vertical force acting<br />

<strong>on</strong> the pipeline is much greater than the<br />

weight of a column of soil whose width is equal<br />

to the pipeline; this is well known in pipeline<br />

mechanics (Boer, et al., 1986; Palmer, 1972).<br />

The analysis required to determine the limiting<br />

vertical force, and therefore the moment induced<br />

in the pipeline, is similar to the analysis<br />

of breakout resistance of buried objects<br />

(Vesic, 1969).<br />

CONCLUSIONS<br />

Ten physical model tests were c<strong>on</strong>ducted at the<br />

CGCF to investigate the effect of (1) arching<br />

and lateral load transfer, and (2) soil/pipe<br />

interacti<strong>on</strong> phenomena <strong>on</strong> arctic submarine pipeline<br />

settlements. Further development of the<br />

technique, and complementary finite-element<br />

analysis, follow from a more detailed understanding<br />

of the stress-strain behavior of the<br />

materials employed and of the interacti<strong>on</strong> between<br />

the pipe surface and the soil.<br />

The experience of this program reinforces c<strong>on</strong>fidence<br />

In the applicati<strong>on</strong> of the centrifuge<br />

technique to soil-structure interacti<strong>on</strong>s<br />

created by thaw settlement, and to pipeline<br />

problems in particular. The technique not <strong>on</strong>ly<br />

gives a clear picture of the overall pattern of<br />

movements, but can be used quantitatively to<br />

assess pipeline strains. It can readily by extended<br />

to cover pipe deformati<strong>on</strong> in the plastic<br />

range. This is important in practice because a<br />

marine pipeline is a robust structure which can<br />

withstand plastic deformati<strong>on</strong>s without distress,<br />

and a limitati<strong>on</strong> to elastic behavior may<br />

be unnecessarily restrictive.<br />

ACKNOWLEDGEMENTS<br />

The authors thank Sohio Petroleum Company for<br />

their support of this program and David Walker,<br />

Andrew Schofield, and Malcolm Bolt<strong>on</strong> €or their<br />

helpful advice and use of the CGCF.<br />

REFERENCES<br />

Boer, B., Hulsbergen, C.H., Richards, D.M.,<br />

Klok, A., and Biaggi, J-P. (19&6), "Buckling<br />

C<strong>on</strong>siderati<strong>on</strong>s in the Design of the Gravel<br />

Cover for a High-Temperature Oil Line,"<br />

Proc. , 18th OTC, Houst<strong>on</strong>, TX, V 4.<br />

Clough, H. and Vins<strong>on</strong>, T.S. (1986), "Centrifuge<br />

Model Experiments to Determine Ice Forces <strong>on</strong><br />

Vertical Cylindrical Structures," Cold<br />

Regi<strong>on</strong>s Science and Technology, V. 12, N. 3. ,<br />

Clough, H., Wurst, P., and Vins<strong>on</strong>, T.S. (19861,<br />

"Determinati<strong>on</strong> of Ice Forces with Centrifuge<br />

Models," Geotech. Test. J., ASTM, V. 9, N. 2.<br />

Nix<strong>on</strong>, J.F., Stuchly, J., and Pick, A.R. (1984),<br />

"Design of Norman Wells Pipeline for Frost<br />

Heave and Thaw Settlement," Proc. , ASME 3rd<br />

Intl. Symp. <strong>on</strong> OMAE, New Orleans, LA.<br />

Nyman, K.J. (19831, "Thaw Settlement Analysis<br />

for Buried Pipelines in <strong>Permafrost</strong>," Proc.,<br />

ASCE Spec. C<strong>on</strong>f. <strong>on</strong> Pipelines in Adverse<br />

Envir<strong>on</strong>ments 11, San DiegO, CA.<br />

Palmer, A.C. (1972), "Settlement of a Pipeline<br />

<strong>on</strong> Thawing <strong>Permafrost</strong>," ASCE, J. of the<br />

Transportati<strong>on</strong> Div., V. 98, N. TE3.<br />

Palmer, A.C., Schofield, A.N., Vins<strong>on</strong>, T.S.,<br />

and Wadhams, P. (19851, "Centrifuge Modelling<br />

of Underwater <strong>Permafrost</strong> and Sea Ice," Proc.,<br />

ASME 4th Intl, Symp. <strong>on</strong> OMAE, Dallas, TX.<br />

Vesic, A.S. (1969), "Breakout Resistance of<br />

objects Embedded in the Sea Bottom, 'I AXE,<br />

Civil Engineering in the Oceans 11.<br />

Vins<strong>on</strong>, T.S. and Wurst, P. (1985). "Centrifugal<br />

Modeling of Ice Forces <strong>on</strong> Single Piles,"<br />

Roc. I ASCE ARCTIC '85: Civil Engin. in the<br />

Arctic Offshore, San Francisco, Ch.<br />

Walker, D.B.L., Hayley, D.W., and Palmer, A.C.<br />

(19831, "The Influence of Subsea <strong>Permafrost</strong><br />

<strong>on</strong> Offshore Pipeline Design," Proc., 4th<br />

Intl. C<strong>on</strong>f. <strong>on</strong> <strong>Permafrost</strong>, Fairbanks, AK.<br />

1329

BETHEL AIRPORT<br />

CTB PAVEMENT PERFORMANCE ANALYSIS<br />

C.L. Vita', J.W. Rwney2 and T.S. Vins<strong>on</strong>3<br />

1Engineering Reliability, Risk and Optimizati<strong>on</strong>, Woodinville (Seattle), Washingt<strong>on</strong> 98W2, USA<br />

2R&M C<strong>on</strong>sultants, Inc., Anchorage, Alaska 99503, USA<br />

3Dept. of Civil Engineering, Oreg<strong>on</strong> State University, Corvallis, Oreg<strong>on</strong> 97331, USA<br />

SYNOPSIS: L<strong>on</strong>g-term performance of the Bethel Airport pavement structure overlying permafrost is<br />

presented. The runway pavement structure, originally c<strong>on</strong>structed in 1958 with an extensi<strong>on</strong> in<br />

1971, c<strong>on</strong>sists of cement treated base (CTB) underlying asphalt c<strong>on</strong>crete (AC). Soil cement usage<br />

in cold regi<strong>on</strong>s, particularly in permafrost areas such as Bethel Airport, is unusual, and thus<br />

provides the focus of interest in the Bethel project. Observati<strong>on</strong>s and analyses indicate use of<br />

CTB at Bethel Airport has been operati<strong>on</strong>ally successful. Compared to untreated crushed gravel<br />

base, CTB provides ec<strong>on</strong>omically and structurally superior pavement performance. Current design<br />

practices for CTB appear suitable for cold regi<strong>on</strong>s. Good c<strong>on</strong>structi<strong>on</strong> c<strong>on</strong>trol and quality remain<br />

essential, as subsequent 1970 c<strong>on</strong>structi<strong>on</strong> deficiencies at Bethel dem<strong>on</strong>strated. There seems be to<br />

no technological reas<strong>on</strong> for inadequate performance of properly designed and c<strong>on</strong>structed CTB in<br />

cold regi<strong>on</strong>s. In fact, the high quality of the 1958 CTB at Bethel has shown adequate performance<br />

for nearly 30 years, and the results of a mechanistic analysis indicates a very l<strong>on</strong>g remaining<br />

fatigue and rutting life for the current CTB pavement structure.<br />

INTRODUCTION<br />

Bethel Airport is located in western Alaska.<br />

approximately 650 km west of Anchorage. The<br />

pavement structure c<strong>on</strong>sists of cement treated<br />

base (CTB) underlying asphalt c<strong>on</strong>crete (AC).<br />

Soil cement usage in cold regi<strong>on</strong>s, particularly<br />

in permafrost areas such as Bethel Airport,<br />

is unusual. Therefore, a study was undertaken<br />

to improve understanding of the applicati<strong>on</strong>. of<br />

soil cement in Alaska by evaluating the CTB<br />

pavement Performance at -Bethel Airport. The<br />

scope of the activities associated with the<br />

study which is summarized here included:<br />

(1) Identificati<strong>on</strong> of pertinent aspects of<br />

the natural soil, thermal, groundwater<br />

and climatological factors:<br />

(2) Identificati<strong>on</strong> of CTB c<strong>on</strong>structi<strong>on</strong><br />

history:<br />

(3) A field and laboratory program to (a)<br />

measure pavement structure and thicknesses<br />

at selected sampling locati<strong>on</strong>s,<br />

(b) obtain AC, CTB, crushed gravel base<br />

(CGB) and subgrade samples of the pavement<br />

for laboratory testing, and<br />

(c) measure deflecti<strong>on</strong>s at sampling<br />

points using Benkelrnan beam procedures;<br />

and<br />

(4) Investigati<strong>on</strong> of the relati<strong>on</strong>ship between<br />

pavement structural characteristics (as<br />

estimated from the field and laboratory<br />

program) and deflecti<strong>on</strong>s using engineering<br />

analysis techniques.<br />

Results from the study (Vita, et al., 1986)<br />

are summarized here.<br />

BETHEL AIRPORT SITE CONDITIONS<br />

Bethel Airport lies in permafrost composed of<br />

frozen Pleistocene delta deposits of silt and<br />

sand and Holocene floodplain alluvium from the<br />

Kuskokwim River. Frozen deltaic sediments are<br />

found to 130 m of depth in a nearby water<br />

well, With an average annual air temperature<br />

of -1.8"C, Bethel has an average freezing<br />

index of about 2440 C degree-days during a<br />

196-day freezing seas<strong>on</strong> and an average thawing<br />

index of about1720Cdegree-daysovera<br />

169-day thawing seas<strong>on</strong>. The airport site is<br />

located 7.2 km west of the Clty of Bethel <strong>on</strong> a<br />

tundra covered sandy ridge lying above the<br />

Kuskokwim River active floodpla\f, Soil<br />

boring data presented <strong>on</strong> 1958 as-built''<br />

drawings for the airport indicate frozen<br />

tundra or organic material overlying frozen<br />

silt, silty sand or sand to the maximum depth<br />

of explorati<strong>on</strong>, 5.5 m below original ground<br />

surf ace.<br />

CONSTRUCTION HISTORY<br />

The present Bethel Airport (Fig. 1) was built<br />

to replace the aging and flood-pr<strong>on</strong>e Civil<br />

Aviati<strong>on</strong> Airport located across the Kuskokwim<br />

River from the City of Bethel. C<strong>on</strong>structi<strong>on</strong><br />

was phased to improve the facility as demands<br />

increased. Four c<strong>on</strong>structi<strong>on</strong> phases are identified<br />

as follows.<br />

Phase I: Initial site c<strong>on</strong>structi<strong>on</strong> was begun<br />

in the summer of 1955 and c<strong>on</strong>tinued through<br />

the summer of 1956. Excavati<strong>on</strong> and subgrade<br />

preparati<strong>on</strong> included stripping of surficial<br />

organic material to expose the underlying<br />

sandy material. Subsequent c<strong>on</strong>structi<strong>on</strong>, into<br />

1957, included c<strong>on</strong>tinued excavati<strong>on</strong> and<br />

grading to complete site rough grading for the<br />

runway, taxiway, parkingapr<strong>on</strong>andrelated<br />

support facilities.

L<br />

BETHEL c<br />

..._."<br />

LEGEND<br />

L TEST LOCATION NUMBER<br />

CORE SAMPLE TAKEN<br />

BENKELMAN BEAM DEFLECTION<br />

ij LIMITS OF ORIGINAL CONST.('!J-<br />

EXTENSION CONS. (470-'711<br />

SCALE IN FEET<br />

SCALE IN METERS<br />

Fig. 1: Bethel Airport Site Map<br />

Phase 11: During July-August 1958 a 150 m<br />

CTB was c<strong>on</strong>structed over the initial 1,220 m<br />

runway and parking apr<strong>on</strong>. The CTB was mixed<br />

in-place using natural sand-silt subgrade<br />

soil. Soils were placed in windrows. A Woods<br />

traveling mixer blended and redeposited the<br />

soil cement mixture. There was some difficulty<br />

keeping the sandy subgrade moist because of<br />

.vertical drainage. Compacti<strong>on</strong> was achieved<br />

using rubber-tired rollers. In some early<br />

c<strong>on</strong>structi<strong>on</strong> locati<strong>on</strong>s inadequate CTB thickness<br />

was found in the center of the lanes. An<br />

extra 25 m of AC was subsequently required<br />

where CTB thickness was c<strong>on</strong>sidered inadequate.<br />

Areas of acceptable CTB thickness were given a<br />

50 nrm to 64 mm AC surface course; secti<strong>on</strong>s of<br />

thin CTB were given a 90 mm surface course.<br />

This completed the initial 1,220 rn runway<br />

segment. hereafter referxed to as the "1958"<br />

c<strong>on</strong>structi<strong>on</strong>,<br />

Phase 111: Airport c<strong>on</strong>structi<strong>on</strong> resumed in areas. Deficiencies were subsequently docuthe<br />

fall of 1968 and included earthwork for a mented. as follows: (1) inc<strong>on</strong>sistent cement<br />

747 m extensi<strong>on</strong> of the runway and an expansi<strong>on</strong> c<strong>on</strong>tent determined from coring and laboratory<br />

of the parking apr<strong>on</strong>.<br />

testing <strong>on</strong> 148 samples, indicating extreme<br />

variability in dtrength and durability of the<br />

The runway pavement c<strong>on</strong>diti<strong>on</strong> was evaluated in base; (2) CTB surface c<strong>on</strong>diti<strong>on</strong>s, grade and<br />

1969 to assess further CTB applicati<strong>on</strong>s<br />

the crown varied significantly: (3) surface<br />

proposed runway extensi<strong>on</strong>.<br />

roughness unsuitable for direct placement of<br />

The pavement<br />

structure was reported to be in genera ly good<br />

c<strong>on</strong>diti<strong>on</strong> with the principal defect being<br />

extensive cracking, mostly reflecti<strong>on</strong> cracks<br />

originating in the soil-cement base; surface<br />

c<strong>on</strong>diti<strong>on</strong> and smoothness being good. Further,<br />

CTB was described as "c<strong>on</strong>structed of good<br />

materials of c<strong>on</strong>sistent quality ... of<br />

above-average compressive and flexural<br />

strength and not particularly suyptible to<br />

the ravages of freeze-thaw cycles. Average<br />

GTB thickness based <strong>on</strong> original c<strong>on</strong>structi<strong>on</strong><br />

1331<br />

records and the 1969 evaluati<strong>on</strong> was 137 m.<br />

Phase IV: C<strong>on</strong>structi<strong>on</strong> began in August 1970<br />

and c<strong>on</strong>sisted of (1) c<strong>on</strong>structing a CTB for<br />

che 747 rn runway extensi<strong>on</strong>, extending the main<br />

a r<strong>on</strong> and widening the runway and taxiway,<br />

(!) overlying the existing runway pavement and<br />

the new CTB with AC. *A 190 um~ CTB was specified<br />

for the runway extensi<strong>on</strong> and wldening<br />

secti<strong>on</strong>s, with a tnm 76 AC surface cover placed<br />

<strong>on</strong> the extensi<strong>on</strong>, and 50 a mm AC surface cover<br />

for the runway widening and overlay of the<br />

existing pavement. Using silty sand as<br />

aggregate, the CTB was mixed in a central<br />

plant, end-dumped, and spread to grade with a<br />

motor grader. CTB was placed between September<br />

10-21, 1970.<br />

At completi<strong>on</strong>. it was apparent the CTB qualit<br />

was highly variable and of questi<strong>on</strong>able<br />

structural capacity and durability in many<br />

the AC surface course: (4) soft pockets,<br />

scaled surface, dislodged and broken chunks of<br />

soil-cement were observed throughout the CTB<br />

c<strong>on</strong>structi<strong>on</strong> area.<br />

Porti<strong>on</strong>s of the 1970 CTB were removed and<br />

replaced with new CTB during the summer of<br />

1971. Paving of the runway was completed<br />

August 21, L971. Phase IV c<strong>on</strong>structi<strong>on</strong> (with<br />

remedial efforts), hereafter termed "1971"<br />

c<strong>on</strong>structi<strong>on</strong>. resulted in completi<strong>on</strong> of the

main runway as it currently exists.<br />

CEMENT-TKEATED PAVEMENT MATERIALS<br />

Cement stabilizati<strong>on</strong> involved mixing soil and<br />

measured amounts of cement and water, compacting,<br />

then letting the mixture harden by cement<br />

hydrati<strong>on</strong>. Cement stabilizati<strong>on</strong> of soils in<br />

roadway and airfield c<strong>on</strong>structi<strong>on</strong> is comm<strong>on</strong> in<br />

temperate climates, In particular, because of<br />

ec<strong>on</strong>omical increases in resistance to pavement<br />

fatigue and subgrade-rutting, CTBs are often<br />

used in asphalt and c<strong>on</strong>crete pavement structures.<br />

Terrel et al. (1979) and Yoder and<br />

Witczak (1975)providediscussi<strong>on</strong>s<strong>on</strong>soil<br />

stabilizati<strong>on</strong> in pavements.<br />

Yet in cold regi<strong>on</strong>s, cement stabilizati<strong>on</strong> is<br />

uncomm<strong>on</strong>. This is due to limitati<strong>on</strong>s of<br />

portland cement availability in remote areas,<br />

and uncertainty about the ec<strong>on</strong>omics and<br />

performance of the stabilized product that<br />

will result if c<strong>on</strong>structi<strong>on</strong> (mixing, compacti<strong>on</strong>,<br />

and curing) operati<strong>on</strong>s must be<br />

c<strong>on</strong>ducted under adverse weather c<strong>on</strong>diti<strong>on</strong>s ,<br />

particularly prol<strong>on</strong>ged freezing temperatures.<br />

Required Cement C<strong>on</strong>tent<br />

Cement amounts required for soil-cement<br />

mixtures is established by durability tests or<br />

unc<strong>on</strong>fined compressi<strong>on</strong> tests. Durability<br />

tests have historically been used to select<br />

cement c<strong>on</strong>tent. Unc<strong>on</strong>fined compressi<strong>on</strong> tests<br />

have recently become comm<strong>on</strong>.<br />

Durability tests subject the soil-cement<br />

mixture to severe volume changes. In the<br />

standard test (PCA. 1971), du licate samples<br />

are subjected to 12 cycles o!! wet-dry (WID)<br />

and freeze-thaw cycling (FIT) and the weight<br />

loss after the cyclic, c<strong>on</strong>diti<strong>on</strong>ing is<br />

measured. The tests are not intended to<br />

simulate actual envir<strong>on</strong>mental c<strong>on</strong>diti<strong>on</strong>s, but<br />

<strong>on</strong>ly cyclic volume changes. The most<br />

ec<strong>on</strong>omical cement treatment level is the<br />

lowest percentage of cement which allows a<br />

stabilized mass to meet the maximum allowable<br />

wei ht loss criteria for an acceptable<br />

sol-cement mixture after 12 cycles of WID and<br />

FIT tests.<br />

Based <strong>on</strong> comm<strong>on</strong>ly acceptable criteria (PCA,<br />

1971), cement-stabilized Bethel soils (1)<br />

should have a weight loss not exceeding about<br />

10 to 14% and (2) would generally require a<br />

cement c<strong>on</strong>tent of about 5 to 12% (by weight)<br />

to meet acceptable WID and FIT weight loss<br />

criteria. Fig. 2 presents Bethel soil durability<br />

test data (RLM, 1972), and indicates<br />

a cement c<strong>on</strong>tent somewhat exceeding 6% would<br />

meet acceptable WID and FIT criteria. Fifteen<br />

Bethel CTB core samples were extracted and<br />

testedinthisstudy.Cementc<strong>on</strong>tentsavera<br />

ed 7.7% f 1.8% and ranged from 5.62 to<br />

11.8% Samples with these cement c<strong>on</strong>tents<br />

(all but <strong>on</strong>e about 6.2%) would be expected to<br />

meet WID and FIT weight loss criteria.<br />

WID and FIT tests may take ,pp to a m<strong>on</strong>th to<br />

c<strong>on</strong>duct. C<strong>on</strong>sequently, short-cut" test<br />

methods have been adopted by many agencies to<br />

determine the suitability of a soil-cement<br />

1332<br />

CEMENT CONTENT-% Of Dry 8011 wt.<br />

Fig. 2: Freeze and Thaw Test<br />

mixture. The most: comm<strong>on</strong> of these is baaed <strong>on</strong><br />

the unc<strong>on</strong>fined compressive strength of a 7-day<br />

moist-cured soil-cement sample (PCA, 1971).<br />

Minimum strength requirements for soil-cement<br />

mixtures range from 1585 kPa to 2068 kPa (PCA,<br />

1971). Other agencies use generally higher<br />

(7-day) values. For example, Witczakk- and<br />

Yoder (1975) list California: 2,758 kPa<br />

(Class B) to 5,170 kPa (Class A), Texas:<br />

4,825 kPa, British: 1,723 kPa (light traffic)<br />

to 2,758 kPa (heavy traffic). They state<br />

these requirements generally provide a durable<br />

mixture and <strong>on</strong>ly in extreme cases is it<br />

necessary to perform durability tests.<br />

Fig. 3 presents 7-day and 42-day compressive<br />

strength data for cement-stabilized Bethel<br />

soils. Bethel sol1 cement c<strong>on</strong>tents somewhat<br />

exceeding 72, giving a 7-day strength of about<br />

2,068 kPa, would meet PCA unc<strong>on</strong>fined compressive<br />

strength criteria. The 42-day strengths<br />

(ranging from about 4,825 kPa to 9,650 kPa at<br />

8Z cement c<strong>on</strong>tent) indicate significant<br />

increases, by a factor of 2 to 4, over the<br />

7-day strengths. The fourteen Bethel CTB<br />

samples taken from the in-service pavement and<br />

tested for this study show atl unc<strong>on</strong>fined<br />

compressive strength of 20,268 kPa * 6,894 kPa<br />

with a range of 6.205 kPa to 29,437 kPa. The<br />

20,268 kPa-average is about2to 4 times<br />

higher than the 42-day strength at 8% cement<br />

c<strong>on</strong>tent and about 9 or 10 times hi her than<br />

the 7-day strength at about 7% to !2 cement<br />

c<strong>on</strong>tent. This data indicates large time-dependent<br />

strength increases for the Bethel CTB.<br />

FIELD AND LABORATORY TESTING PROGRAM<br />

As part of the current study, 'two field<br />

sampling and deflecti<strong>on</strong> surveys were made at<br />

the Bethel Akport main runway, the first<br />

c<strong>on</strong>ducted in October 1984, The subgrade was<br />

unfrozen. Twenty-six sampling locati<strong>on</strong>s were<br />

selected, as shown <strong>on</strong> Fig. 1. From these, 33

Index/physical properties were made in accordance<br />

with the ASTM or AASHTO test procedures.<br />

Resilient moduli of the AC, CTB, CGB, and<br />

subgrade soils and fatigue characteristics of<br />

the AC were determined in accordance with<br />

Walter, et al. (1984). Sample locati<strong>on</strong><br />

numbers are shown <strong>on</strong> Fig. 1.<br />

kig. 3:<br />

CEMENT KINtKWt- % of Prv loll Wt.<br />

compressive Strength of<br />

Laboratory-Made Specimen<br />

samples were recovered and 19 Benkelman beam<br />

measurements made. Laboratory tests were<br />

c<strong>on</strong>ducted <strong>on</strong> 12 AC cores, 15 CTB cores, <strong>on</strong>e<br />

untreated CGB sample, and five subgrade gam-<br />

. The gecmd eurvey was c<strong>on</strong>ducted in May<br />

!les 985 to obtain Benkelman beam measurements<br />

during the Spring break-up period, over a<br />

period of roughly maximum subgrade thaw-weal-'<br />

ening. Data are sunrmarized in Table I.<br />

Informal observati<strong>on</strong>s indicated the runway<br />

pavement was in generally good c<strong>on</strong>diti<strong>on</strong> with<br />

some isolated areas showing signs of distress,<br />

particularly in n<strong>on</strong>-CTB ( ravel base) areas.<br />

Cracking was variable ant included probable<br />

thermal and reflecti<strong>on</strong> cracks.<br />

The laboratory test program was c<strong>on</strong>ducted to<br />

identify (1) index/ hysical properties of the<br />

AC and CTB cores an! soil samples taken during<br />

the field program, (2) resilient moduli of the<br />

AC surface course, CTB material, aggregate<br />

base and aubgrade soil, and (3) fatigue<br />

characteristics of the AC and CTB materials.<br />

Results are summarized in Figs. 4 through 6.<br />

-<br />

-ao<br />

The 1958 AC had higher average density<br />

(approx. 2,330 kg/m3) compared to the 1971<br />

phase (approx. 2,275 kg/m3). The 1958 CTB had<br />

lower average density. cement c<strong>on</strong>tent, and<br />

com resstve strength (approx. 1,884 kglrns.<br />

7. I! and 19,365 kPa, respectively) corn ared to<br />

the 1971 phase (approx. 1,900 kg/m3, l.3X and<br />

21,165 kPa, respectively.) Compressive<br />

strength increases with increasing cement<br />

c<strong>on</strong>tent as shown in Fig. 4. Compresslve<br />

strengths (even compensating for the relatively<br />

l<strong>on</strong>g cure time) are well above strength ,<br />

levels c<strong>on</strong>sidered acceptable to meet durability<br />

criteria (PCA, 1971).<br />

Resilient moduli of AC cores were evaluated at<br />

-5"C, 10°C and 24°C. Results are summarized<br />

in Fi . 5. Resilient moduli for both the 1958<br />

and 1871 cores decrease by nearly a factor of<br />

10 over the 28°C temperature range (approx.<br />

27,580 MPa at: -4°C to approx 3,450 MPa at<br />

24°C). The 1958 c<strong>on</strong>structi<strong>on</strong> hase moduli are<br />

about 10% higher than the 19A phase modulF.<br />

CTB resilient moduli are shown in Fig. 6.<br />

1958 moduli are greater than the 1971 moduli.<br />

For practical purposes, CTB resilient moduli<br />

are temperature-independent.<br />

4<br />

- '\;<br />

\<br />

If-<br />

Pavement C<strong>on</strong>structed 19.58<br />

"<br />

"-Pavement C<strong>on</strong>structed 1971<br />

'.<br />

10.000<br />

25.000<br />

-00,000<br />

5<br />

lo<br />

I I I<br />

-5 0 a 10 I5 40 25<br />

Temperature, "C<br />

Fig. 5:<br />

Il,OOO<br />

10,000<br />

Resilient Modulus Versus Temperature<br />

for Asphalt Pavements<br />

p"<br />

-95<br />

Fig. 4 :<br />

- 1<br />

0 5<br />

1<br />

IO<br />

Cement C<strong>on</strong>tent %<br />

-pa<br />

"I<br />

-10<br />

0<br />

-ch<br />

E<br />

T-<br />

16<br />

Compressive Strength Versus 'Cement<br />

C<strong>on</strong>tent<br />

PAVEMENT PERFORMANCE EVALUATION - MECHANISTIC<br />

APPROACH<br />

Pavement structural performance analysis was<br />

based <strong>on</strong> the mechanistic approach (Mah<strong>on</strong>ey and<br />

Vins<strong>on</strong>, 1983). Calculated strains at critical<br />

locati<strong>on</strong>s in the pavement structural secti<strong>on</strong><br />

are limited to acceptable levels for a specified<br />

number of load repetiti<strong>on</strong>s (i.e., the<br />

design life). Two c<strong>on</strong>diti<strong>on</strong>s are generally<br />

employed to define failure of the roadway<br />

structure: (1) tensile strain (or stress) at<br />

the bottom of the surface layer cannot exceed<br />

a maximum allowable tensile strain for a

specified number of load repetiti<strong>on</strong>s, and (2)<br />

vertical compressive strain at the top of the<br />

subgrade (supporting) layers cannot exceed a<br />

maximum allowable vertical strain for a<br />

specified number of load repetiti<strong>on</strong>s.<br />

Reflecti<strong>on</strong> cracking of the CTB into<br />

and<br />

through the AC surface COUKSB is not analyzed<br />

as part of the mechanistic analysis. Cracking<br />

of a CTB (aswithc<strong>on</strong>cretepavements)is<br />

c<strong>on</strong>sidered inevitable, The attempt is to<br />

c<strong>on</strong>trol cracking and maintain pavement integrity<br />

by providing adequate AC thickness to<br />

limit reflecti<strong>on</strong> cracking, and then maintaining<br />

those cracks that do occur. ,<br />

Stresses, strains and deflecti<strong>on</strong>s in a pavement<br />

structure are predicted using pavement<br />

structure resillent moduli with multilayer<br />

elastic theory (Hicks. 1982). Validity is<br />

establishedbycomparingobservedpavement<br />

deflecti<strong>on</strong>s with predicted deflecti<strong>on</strong>s for<br />

equivalent loading c<strong>on</strong>diti<strong>on</strong>s. To this end. a<br />

predicti<strong>on</strong> was made of the surface deflecti<strong>on</strong>s<br />

for the 1958 and 1971 pavement structure under<br />

the survey load vehicle. For the 1958 pavement,<br />

predicted surface deflecti<strong>on</strong> was<br />

0.287 nun; observed average surface deflecti<strong>on</strong><br />

was 0.279 mm. A similar comparis<strong>on</strong> with the<br />

average 1971 CTB pavement structure indicated<br />

a predicted deflecti<strong>on</strong> of 0.266 rmn and an<br />

average observed deflecti<strong>on</strong> of 0.279 m. The<br />

close agreements for these cases support the<br />

use of material properties and the multilayer<br />

elastic model (program PSAD2A) to (approximately)<br />

assess stresses and strains in the<br />

+-<br />

a +<br />

(1: 1<br />

X<br />

" " ~ ~<br />

Pavornmt C<strong>on</strong>structed IQSB<br />

Pavement C<strong>on</strong>8tructrd 1971<br />

-5 0 5 IO I6 tO<br />

Fig. 6:<br />

Temparature,<br />

OC<br />

.f1,000<br />

-ao.ooo<br />

-25,000<br />

-xo,ooo<br />

-15.000<br />

-10.000<br />

- 0<br />

n.<br />

1<br />

-0<br />

6<br />

Resilient Modulus Versus Temperature<br />

for Cement Treated Baaes<br />

Bethel Airport pavement etructure far other<br />

pavement envir<strong>on</strong>mental c<strong>on</strong>diti<strong>on</strong>s.<br />

Analysie of the pavcment structure life for<br />

fatigue and rutting failure c<strong>on</strong>diti<strong>on</strong>s was<br />

c<strong>on</strong>ducted at critical locati<strong>on</strong>s for Boeing 737<br />

(B737) aircraft loading. Four thermal-envir<strong>on</strong>mental<br />

c<strong>on</strong>diti<strong>on</strong>s were c<strong>on</strong>sidered<br />

as follows:<br />

1) Summer, Unfrozen: T=lO"C in AC and CTB,<br />

unfrozen subgrade.<br />

2) Winter, Frozen: T--4"C in AC and CTB,<br />

frozen subgrade. , .<br />

TABLE I<br />

Asphalt and Cement Treated Base Core Index Properties<br />

1<br />

2<br />

3<br />

4<br />

5<br />

6<br />

8<br />

7<br />

9<br />

10<br />

11<br />

12<br />

13<br />

14<br />

1.5<br />

16<br />

17<br />

la<br />

19<br />

20<br />

21<br />

22<br />

23<br />

24<br />

25<br />

26<br />

147<br />

135<br />

147<br />

157<br />

150<br />

165<br />

175<br />

175<br />

165<br />

140<br />

137<br />

91<br />

91<br />

102<br />

57<br />

76<br />

62<br />

76<br />

145<br />

132<br />

107<br />

107<br />

152<br />

114<br />

140<br />

2,300 132<br />

135<br />

140<br />

117<br />

114<br />

127<br />

112<br />

114<br />

2.360 127<br />

112<br />

2,290<br />

2,347<br />

170<br />

302<br />

213<br />

185<br />

2,276<br />

2,332<br />

249<br />

152<br />

267<br />

196<br />

2,257 127<br />

2,148 201<br />

213<br />

1,863<br />

1,911<br />

1,871<br />

1,879<br />

I, 884<br />

1,874<br />

1,921<br />

1,917<br />

1 ,a29<br />

1,938<br />

1,969<br />

1,914<br />

1,865<br />

1,938<br />

1,853<br />

1,813<br />

1,882<br />

1,945<br />

8.81<br />

6.83<br />

10,36<br />

9.23<br />

7 .OO<br />

6.19<br />

6.96<br />

6.46<br />

11.87<br />

-27.34<br />

-18.62<br />

-29 e 44<br />

-26.20<br />

-15.44<br />

- 6.21<br />

-28.75<br />

-15 * 10<br />

1.64<br />

-27.03<br />

.203<br />

.305<br />

.711<br />

-610<br />

,914<br />

.610<br />

.203<br />

.406<br />

.203<br />

.305<br />

.457<br />

.203<br />

.203<br />

* 102<br />

.508<br />

.610<br />

.914<br />

.610<br />

1.02<br />

.914<br />

.102<br />

.305<br />

.102<br />

.203<br />

.305<br />

.102<br />

.152<br />

1334

3) Spring-Breakup, Shallow-Thaw: T-2'C in<br />

AC and CTB, subgrade thawed to 0.6 m and<br />

frozen below.<br />

4) Spring-Breakup, Deep-Thaw: T=2"C in LC<br />

and CTB, thawing subgrade to infinite<br />

depth .<br />

AC and CTB moduli used in the multilayer<br />

elastic analysis were obtained from Figs. 5<br />

and 6. Frozen soil. moduli were increased by<br />

roughly 300% over unfrozen moduli and thawing<br />

soil moduli reduaed to about 25% of the<br />

unfrozen moduli, Presentati<strong>on</strong> of the results<br />

is given by Vita, et al. (1986). In summary:<br />

1) I At comparable thermal/envir<strong>on</strong>mental<br />

c<strong>on</strong>diti<strong>on</strong>s surface displacements for the<br />

untreated CGB are about twice the displacements<br />

for the CTB secti<strong>on</strong>s.<br />

2) Fatigue failure for the AC layer will not<br />

occur for any reas<strong>on</strong>able number of B737<br />

loadings.<br />

3) Rutting failure in the subgrade will not<br />

occur for any reas<strong>on</strong>able number of B737<br />

loadings,<br />

4) AC temperature does not appreciably<br />

influence the strain or flexural stress<br />

at the bottom of the CTB or vertical<br />

strain <strong>on</strong> the subgrade; AC temperature<br />

does influence the strain at the bottom<br />

of the AC layer.<br />

The operati<strong>on</strong>ally successful use of CTB at<br />

Bethel provides support to the general use of<br />

CTB at other locati<strong>on</strong>s in cold regi<strong>on</strong>s. Of<br />

course, any given candidate locati<strong>on</strong> €or CTB<br />

must be evaluated for case-specified c<strong>on</strong>diti<strong>on</strong>s,<br />

needs, and c<strong>on</strong>straints. For example,<br />

CTB does not have any special advantage in<br />

overcoming adverse effects of subgrade foundati<strong>on</strong><br />

thaw in areas of thaw-unstable permafrost.<br />

However, pre-thawing of subgrade<br />

permafrost several years in advance (as was<br />

d<strong>on</strong>e for the Bethel runway) may, in the right<br />

siruati<strong>on</strong>, improve foundati<strong>on</strong> soil performance.<br />

Further, the performance of CTBin<br />

poorly draining soils (unlike Bethel soils)<br />

with a high groundwater table is unknown.<br />

Also, in cases where abundant crushed gravel<br />

is locally available. there may no be ec<strong>on</strong>omic<br />

advantage to CTB. Finally, where a su erior<br />

natural subgrade exists, there may !e no<br />

advantage to CTB.<br />

CTB experience at Bethel indicates that in<br />

poor subgrade areas where gravel is not<br />

ec<strong>on</strong>omically available, CTB can provide a<br />

cost-saving soluti<strong>on</strong> which will c<strong>on</strong>tribute to<br />

high quality pavement performance. Following<br />

proper planning, design, c<strong>on</strong>structi<strong>on</strong> and<br />

maintenance, CTBs can be used in cold regi<strong>on</strong>s<br />

to effect superior ec<strong>on</strong>omy and l<strong>on</strong>g-term<br />

pavement performance.<br />

SUMMARY AND CONCLUSIONS<br />

Observati<strong>on</strong>s and anal ses indicate that the<br />

use of cement treateg base, CTB, at Bethel<br />

Airporthasbeenoperati<strong>on</strong>allysuccessful.<br />

Corn ared to untreated CGB. CTB gives ec<strong>on</strong>omicayly<br />

and structurally superior pavement<br />

performance.<br />

In all cases of CTB use, proper design and<br />

c<strong>on</strong>structi<strong>on</strong> is essential to a successful<br />

product. Current design practices for<br />

CTB<br />

appear suitable for cold regi<strong>on</strong>s. Good<br />

c<strong>on</strong>structi<strong>on</strong> c<strong>on</strong>trol and quality are essential,<br />

as the 1970 c<strong>on</strong>structi<strong>on</strong> seas<strong>on</strong> deficiencies<br />

at Bethel dem<strong>on</strong>strated.<br />

There seems to be no special technological<br />

reas<strong>on</strong>s for inadequate performance of properly<br />

designed and c<strong>on</strong>structed CTB in cold regi<strong>on</strong>s.<br />

In fact, the high quality of the 1958 CTB at<br />

Bethel has shown adequate performance for<br />

nearly 30 years, and the results of the<br />

mechanistic analysis described above indicates<br />

a very l<strong>on</strong>g remaining fatigue and rutting life<br />

for the current CTB pavement structure.<br />

Reflecti<strong>on</strong> cracking, a comm<strong>on</strong> and general<br />

t<strong>on</strong>diti<strong>on</strong> of all CTB pavements, is generally<br />

c<strong>on</strong>trolled with adequate AC thickness to<br />

reduce surface cracking and crack sealing, as<br />

part of routine maintenance. Surface cracking<br />

<strong>on</strong> the Bethel Airport runway includes thermal<br />

cracking effects (similar to those found, for<br />

example, in the Fairbanks area) and<br />

CTB-induced reflecti<strong>on</strong> cracking. However, CTB<br />

particular problem at Bethel.<br />

CITED REFEmNCES<br />

Hicks, R.G. (1982). Use of Layered Theory in ,<br />

the Design and Evaluati<strong>on</strong> of Pavement<br />

1<br />

Systems, Report No. FHWA-AK-RD-83-8,<br />

Alaska DOTPF.<br />

Mah<strong>on</strong>ey, J. and Vins<strong>on</strong>, T.S., (1983). A<br />

mechanistic approach to pavement design<br />

in cold regi<strong>on</strong>s, Proc. 4th Intl. C<strong>on</strong>fer-<br />

ence <strong>on</strong> <strong>Permafrost</strong>. NAS.<br />

Portland Cement Associati<strong>on</strong> (PCA), (1971).-<br />

Soil-Cement Laboratory Handbook, Skokie.<br />

R&M Engineering h Geological C<strong>on</strong>sultants<br />

(R&M) , (1972). Bethel Airport, Stage V<br />

C<strong>on</strong>structi<strong>on</strong>, Rept. to AK. Div. of<br />

AviaGi<strong>on</strong>.<br />

Terrel, R.L., et a1 (1979). Soil Stabilizati<strong>on</strong><br />

in Pavement Structures, A User's Manual,<br />

- 2 vols., USDOT, FHWA-IP-80-2.<br />

Vins<strong>on</strong>, T.S., Mah<strong>on</strong>ey, J.P.. and Kaminski,<br />

J.J. (1984). Cement stabilizati<strong>on</strong> for<br />

road c<strong>on</strong>structi<strong>on</strong> in cold regi<strong>on</strong>s, Proc.<br />

-3rd Intl. Cold Regi<strong>on</strong>s Engineering<br />

Specialty <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, Edm<strong>on</strong>t<strong>on</strong>.<br />

Vita, G.L., Vins<strong>on</strong>. T.S., and Ro<strong>on</strong>ey, J.W.<br />

(1986). Bethel Airport CTB-AC Pavement<br />

Performance Analysis, Report No.<br />

AK-RD-86-31, Alaska DOTPF.<br />

Walter, Y..<br />

Brickman, A.M., Hicks, R.G., and<br />

Vins<strong>on</strong>, T.S. (1984). Installati<strong>on</strong> Operati<strong>on</strong><br />

and Maintenance Procedures for<br />

Repeated Load Triaxial and Diametral Tes<br />

S stems, Transportati<strong>on</strong> <strong>Research</strong> Report<br />

ST-1, 0 reg<strong>on</strong> State University.<br />

Yoder, E.J. and Witczak, M.W. (1975).<br />

Principles of Pavement Design, 2nd ed.,<br />

Wiley, New York.<br />

reflecti<strong>on</strong> cracking does not appear to be a 1335

A NEW METHOD FOR PILE TESTING AND DESIGN<br />

IN PERMANENTLY-FROZEN GROUNDS<br />

Pile Testing, Relaxati<strong>on</strong>, Permanently-Frozen Grounds,<br />

Pile Design, Variable Loading, Base Temperature<br />

S.S. Vyalod and Yu.S. Mirenburg2<br />

1Mosmw Engineering-C<strong>on</strong>structi<strong>on</strong> Institute, Moscow, USSR<br />

2Northern Affiliate of <strong>Research</strong> Institute for Foundati<strong>on</strong>s and Underground Structures,<br />

USSR’s Gmtroi, Vorkuta, USSR ,<br />

SYNOPSIS Traditi<strong>on</strong>al methods o$ pile testing are very laborious and lengthy. A new,<br />

dynamometric method of testing haa been developed, enabling testing time to be reduced end<br />

data to be obtained necessary for a l<strong>on</strong>g-term predicti<strong>on</strong> of the carrying capacity of the pile<br />

and its aettlinf under the impact of both c<strong>on</strong>stant and time-variable loading. Theoretical and<br />

experimental va idati<strong>on</strong> of the new method of testing, testing procedure and.date processing,<br />

as well as pile design from the results of the tests,<br />

I~5TRODUC’PION<br />

Teste <strong>on</strong> full-size piles prove to be a particularly<br />

reliable and trustworth somce of<br />

data for predictiw the settling and carrying<br />

capacity of pile foundati<strong>on</strong>s in frozen<br />

Reaucti<strong>on</strong> grounds. However of testin aucb time teets can<br />

are be ver l<strong>on</strong>g.<br />

achfeved<br />

by going ovex from fraditi<strong>on</strong>al tests by<br />

atepincreasing loading to relaxagi<strong>on</strong> tests.<br />

One of such testing methods Is the dynamometric<br />

method developed by the authors<br />

(Vyalov, Yeroshenko, Mirenburg, 1977).<br />

DEBIGN FORMULAE<br />

To be able to obtain from test results a poaaibility<br />

for predicting the settling S and<br />

the carrying capacity F of piles for any<br />

variati<strong>on</strong> of vertical lolding N(t) in time<br />

t we have worked our; and employed a formula<br />

comprising instantaneoua and time-varying<br />

th F and deformeti<strong>on</strong>al A charac-<br />

~%ics opt the pile foundati<strong>on</strong> ttyalov,<br />

Mirenburg, 1984).<br />

For a c<strong>on</strong>stant load N this foxmula has the<br />

i0m:<br />

where A , A 1 , F and % are parameters<br />

to be d8tedined in’the te8ts. ’<br />

Dependence (1) reflects the physical 6sp18ncB<br />

of the pile aett’ling prooesa due to loadin .<br />

Thus, 88 loading N approaches B (N+Butf<br />

the settling S increasee without! bound<br />

fig.1-c). In accoraance with the work<br />

Gexsevanov, 1917), this determines P as<br />

a maximum resistame, thus enabling ib’to<br />

be represented in the form (2).<br />

tnl<br />

where the firat term inthe right-hand side<br />

stands for instantaneoua settling linearly<br />

depending <strong>on</strong> the load, and the sec<strong>on</strong>d term -<br />

the creep aettlirq with the time-varying<br />

characteristics F and A described by<br />

the universally-lcn% depen&&cea<br />

Fig.l<br />

A family of curves described by<br />

the dependence (4);<br />

a. Relaxati<strong>on</strong> curvei b. Isoqhf<strong>on</strong>es~<br />

c. L<strong>on</strong>g-term strength curve!<br />

d. Creep cuxves.<br />

1336

Furthermore, in the limit N-0<br />

('I) becomes linear with respect<br />

the Punchi<strong>on</strong><br />

to loading N<br />

settling at the end of the step, instantaneous<br />

increments of pile settling AS anu hydrojack<br />

pist<strong>on</strong> run-out ah during'pile Loading<br />

wich the next step loadoare recorded. These<br />

data, as shown in fig.3-c, permit elastic<br />

characteristics of the setup A and of the<br />

pile four.dati<strong>on</strong> A, to be detedned.<br />

which, to a certain extent, reflects a lineax<br />

deformati<strong>on</strong> of the baae under small loads.<br />

Substituting (2) and (3) in ('I) leads to a<br />

generalized dependence of settling up<strong>on</strong><br />

loading<br />

The families of creep curves, Isochmnes and<br />

the l<strong>on</strong>g-term strength curve describea by<br />

the expressi<strong>on</strong> (4), as seen from fig.1, corresp<strong>on</strong>a<br />

in shape to the experimental <strong>on</strong>es<br />

end, as revealed by DUX inveatigati<strong>on</strong>a, with<br />

an accuracy sufficient for practicaL calculati<strong>on</strong>s<br />

quantitatively reflect deformati<strong>on</strong><br />

processes and variati<strong>on</strong>a of strength cbaractaristics<br />

of frozen grounda (Vyelov, Mixenburg,<br />

F~kin, 197 ), basas of diea (Vyalov, Yiren-<br />

19807 and piles (Vyalov Mirenbuq<br />

QWj, a8 well as of t9, aattiing of buddings<br />

<strong>on</strong> these gfounds ( lrenburg, Fedoseev,<br />

, 1:' I.<br />

1982).<br />

This enabled the depen;$ance (4) to 'be put at<br />

the basis of the elaborated procedure and<br />

the analysis OP results of the dynamometric<br />

pile testing method.<br />

stage 1<br />

'E 1<br />

I<br />

stage d<br />

T&BTING PROCEDURE!<br />

The tesbing procedure divides into two stages<br />

(fig.).<br />

The fzrst stage involves testa <strong>on</strong> the piles<br />

by a step-Increasing load with a brief applicati<strong>on</strong><br />

(4-8 hr) of steps. ,In this case<br />

the loading is brought up to the values of<br />

N close to the maximum loading <strong>on</strong> the pile<br />

prn corresp<strong>on</strong>ding to the step aurati<strong>on</strong> t to<br />

b'8'determined from the formula (2) for tC= t,<br />

s mm<br />

0<br />

I<br />

The value of P will be determined during<br />

testing by plobking the variati<strong>on</strong> of pile<br />

settling S et the end of the step versus<br />

the Load N at this step In xectifying cooxdinates<br />

N/S-N (f ig.3-a). As follows from<br />

the formula (I), the segment cut off by the<br />

plot ab the x-axis determines P' , On the y-<br />

-axis, according to the same Perkti<strong>on</strong>ship (I),<br />

the plot cuts off a seGment corresp<strong>on</strong>ding to<br />

the vcllue of the inverse dsformati<strong>on</strong>al characteristic<br />

A' for the step durati<strong>on</strong> t<br />

In the proc&s of stage I, apart from Ehe pile<br />

Fig.2<br />

Deformati<strong>on</strong> of testing set-up<br />

and pile during.. testing(a,b,c)<br />

and plotted varlatl<strong>on</strong>s of the<br />

load N(d) anu progress of<br />

sett1j.m s(e) . . <strong>on</strong> a full-size<br />

ele Pile, N255; 2. Bracing, 3. Hydrojack,<br />

4. Hydrojack pist<strong>on</strong><br />

run-out meter, 5. Pressure<br />

gauge, 6. Reference system,<br />

7. Pile settling meter.<br />

1337

Once the C<strong>on</strong>diti<strong>on</strong> (5) has been fulfilled and<br />

the load N, has been maintained during the<br />

tLme of a step t , oil feed to the hydrojack<br />

is terminated an8 testing c<strong>on</strong>tinues at stage<br />

I1 with the hydrojak pist<strong>on</strong> run-out height h<br />

fixed for the entire stage.<br />

The roperties of the pile-ground base in<br />

Fig.q-c axe represented by a family of isockr<strong>on</strong>es<br />

for time moments t z 0, t, and<br />

t t4'<br />

A$ the first stage of loading with a step-<br />

-increasing losd the progress of pile settling<br />

corresp<strong>on</strong>ds to the isocbr<strong>on</strong>e t at the<br />

stretch (of 5 up to the load Nm cogresp<strong>on</strong>ding<br />

to the c<strong>on</strong>diti<strong>on</strong> (5).<br />

A t testing stage II the pile settling occurs<br />

due to the effect of elastic forces of the<br />

'Qpile-brace" system and, therefore, the settling<br />

versus load relati<strong>on</strong>ship is linear with<br />

a proporti<strong>on</strong>ality coefficient corresp<strong>on</strong>ding<br />

to the brace rigidity A and is represented<br />

in fig.1-c by.a atraightPline (fg) within<br />

the sectling range El - S4.<br />

Ertxapolati<strong>on</strong> of this'line segment 3~l fax aa<br />

the isochr<strong>on</strong>e t 4 0 allows for the prehiabory<br />

of loading at stage I and enables stage 11<br />

to be examined separately, writing down the<br />

equati<strong>on</strong> of settling progress, according to ,<br />

fig.l-c, in the form:<br />

An equati<strong>on</strong> of the variati<strong>on</strong> of loading in<br />

time N(t) at stage I1 will be obtained by<br />

substituting (4) in (6)<br />

Fig.3. Processing of testing data<br />

for pile @5<br />

a. Determinati<strong>on</strong> of Putand<br />

A ; b. Isochr<strong>on</strong>e t 1<br />

cYtDetexminati<strong>on</strong> ofCA and A *<br />

d. Determinati<strong>on</strong> of Apand a '<br />

In this case the progress of pile settling<br />

is due solely to the effect of elastic forces<br />

of the testing set-up. A t testing stage<br />

I1 the measurement of the Load <strong>on</strong> the pile<br />

with the pressure gauge 5 al<strong>on</strong>e is obligatory.<br />

Measurement of the pile settling S and<br />

hydrojack pist<strong>on</strong> run-out h are just checkc.<br />

The length of testing stage I is determined<br />

by the minimal number of loading steps necessary<br />

Pox analysis. Given a correct cboiae of<br />

step magnitudes, their number is not more<br />

than 7-10, which corresp<strong>on</strong>ds to the time of<br />

'1-3 days.<br />

The length of stage 11 is to be appointed<br />

<strong>on</strong> c<strong>on</strong>diti<strong>on</strong> of obtaining a sufficient number<br />

of experimencal points <strong>on</strong> the relaxati<strong>on</strong><br />

curve for analyais (fig.2-d) and, as a rule,<br />

does not exceed 3-6 days.<br />

The formulae (2) ana (3) will be usea,to find<br />

relati<strong>on</strong>ships between the values of F and<br />

A' determined at stage I and the psxgeters<br />

A:tsnd<br />

I,,<br />

Subatitutiug these parameters in (7) will<br />

give after transformati<strong>on</strong>s the expressi<strong>on</strong><br />

TKEORETICAL VALIDATION OF DATA PIiOCESSZPjG<br />

Our investigati<strong>on</strong>s and the comparie<strong>on</strong> of<br />

fig.1-a with fig.1-c indicate that for prac-<br />

For elaborati<strong>on</strong> ana validati<strong>on</strong> of the proce- tical calculati<strong>on</strong>s we may acce t a prarequiduxe<br />

of data processing for dynamometric tes- tiite about the similarity of tfe eff arts rets<br />

<strong>on</strong> piles let us examine the progress of laxati<strong>on</strong> CUXVB in the "pile-brace" system<br />

pile settling and variati<strong>on</strong>s of loading <strong>on</strong> N(t) and the l<strong>on</strong>g-term strength curve FUt<br />

them in testing, as shown in fig.l-a,b. The with a similitude coefficient q<br />

1338 I

enabling the plot of the expsessi<strong>on</strong> (12) to<br />

be rectified in the coordinates<br />

Design data with respect to carrying capacity<br />

in the Table have been determined from formula<br />

(2) fox the service period t = 50 years.<br />

Design witls respect to deformstib was made<br />

from the formula C4)i.n which to determine the<br />

design loading the pile settling st the end<br />

of the service period t was assumed to be<br />

15 cm, ana for a com2arfe<strong>on</strong> of design loads<br />

derived by calculati<strong>on</strong> witn respect to caxrying<br />

capacity and deformati<strong>on</strong>s the latfer,<br />

according to authorized requirements (Building<br />

Norms and Codes 11-18-76) were muZtiplied<br />

by the safety coefficienta = 1.2 and 6<br />

z 1.1. 8=<br />

The uabulated data pointo a close coxresp<br />

<strong>on</strong>dance between teat- results obtained by epplying<br />

a stepped-increasing load ana dynamometrically.<br />

The latter is seen to be aignificantly<br />

more favourable regards as testing<br />

length, particularly in Comparis<strong>on</strong> with testing<br />

until an arbitrary settling attenuati<strong>on</strong><br />

0.02 mm a day (piles N% 4 and 5).<br />

where a is a segment cut off by the plot in<br />

iig.3-d <strong>on</strong> the g-axial e is the base of natural<br />

lo arithms.<br />

Paramefers A and B ape to be determined<br />

fxom'the exp8essi<strong>on</strong>go(8) and (9).<br />

Thus, the propose@ pile testing method permits<br />

all parameters in the formula (!+) to be<br />

determined.<br />

".HOB<br />

OF PTLE DEIGN<br />

The above formulae for the carrying capacity<br />

(2) and settling (4) of the pile enable verifr<strong>on</strong>s<br />

in loading <strong>on</strong> the pile during service<br />

! o be taken into account. To this end, the<br />

formula (2) is to be substituted in the equati<strong>on</strong><br />

of linear summati<strong>on</strong> of damage (Vyalov,<br />

19781, and the expressi<strong>on</strong> (4) is used in accordance<br />

with the phenomenological theory of<br />

n<strong>on</strong>-linear hereditary creep<br />

EXPERIMENTAL CHXCK<br />

In deducing design formulae of daca process-<br />

'in for dynemometric pile testing some aimplfficsti<strong>on</strong>s<br />

and assumpti<strong>on</strong>s were made for<br />

an experimental check <strong>on</strong> Which in various<br />

ears teats were made <strong>on</strong> <strong>on</strong>e and the same piyes<br />

by applying a step-rising load and dynamometrically.<br />

Comparis<strong>on</strong> of these teat xesults<br />

axe 1is.ted in the Table.<br />

TABLE<br />

Comparis<strong>on</strong> of the Length and Results<br />

of !Pasts by Stepped Loading and<br />

Dynamometrically<br />

!Test 1engthlDesign maximally l<strong>on</strong>g loads<br />

! !<strong>on</strong> a pile according to test-<br />

1 ! in# date, ky<br />

! ! ! dresi$n with i desian with<br />

where 9 is the integrati<strong>on</strong> variable!<br />

However, since the integral in (16) in a closed<br />

form callnot be taken, as a rule, by dividing<br />

the curve N(t) into porti<strong>on</strong>s where loading<br />

can be c<strong>on</strong>sidered invariable, we should<br />

better use a simpler formula (Mixenburg,I9&).<br />

1339<br />

where Nmax is the maximum load <strong>on</strong> the pile;

CONCLUSION<br />

j= t, t- j<br />

(18) ' The above releaticnships quite adequately and<br />

0 c<strong>on</strong>fidently describe the performance of piles<br />

in permanently-frozen grounds and can be used<br />

Using this relati<strong>on</strong>ship, we compared the pro- as a basis fox predicting their settling and<br />

gress of settling in tests <strong>on</strong> pile N.5 by ap- carrying capacity under c<strong>on</strong>stant and timeplying<br />

stepincreasing loading with its pre- varying loads and teznperatures.<br />

dicti<strong>on</strong> fr<strong>on</strong> dynamometric test data. As evi- The proposed dynamometric mcthod o pile testdenced<br />

by fip.4, the values of design settl- ing enables us to obtain within a relatively<br />

ing not badly COPXehte with experimedd. data, period, 5-10 days, all relevat data<br />

particularly at loading range below the maxi- for such a predicti<strong>on</strong>.<br />

mally-l<strong>on</strong>g desigr: load, as determined in the<br />

table Fut 250 kN.<br />

Temperature variati<strong>on</strong>s can be approximately LITERA!CURA<br />

allowed for by introducing ficticious loads Nf<br />

in place of the actual <strong>on</strong>es N, the relatioa- 1. Gersevanov N.Y. (1917). Opredelenie soproship<br />

beheen which is determined by the ratio<br />

tivleniya svay. Zement, 8. 9-11, '<br />

of the carrying capacity of piles, as detek-<br />

Petrograd.<br />

mined in compliance with SNandP P-18-76 under<br />

testing temperature F, aad under the design 2. Pirenburg XU.~. , Fedoseev '91u.S. (1982).<br />

Prognoz osami svaynih fudarnentov V<br />

temperature regime P,:<br />

plasticbnomerzlih gruntah. Reologiya<br />

gruntov i injenernae merzlotovedenie.<br />

Nf =N- Fur (19) Nauka, 8. 159-161. MoSkva.<br />

FLW 3. hlirenburg Yu.S., (19W). Uchet peremennoy<br />

nagruzki i temperaturi pri raschete<br />

funaamentov na vechnornerzlih gruntah.<br />

Osnovaniya fundamnti i mehanika<br />

gsuntov (33, S. 16-18.<br />

N KN<br />

4. SNiP I)-18-76 (1977). Stroitelnie normi i<br />

pravila. Osnovaniya i Pundamenti na<br />

vechnomerzlih gruntah. Stroyi~dat~s.48.<br />

5. Vyalov S.S., Eroshenko V.N., Mirenburg Yu.S.<br />

(1977)..Sposob ispitaniya aesushey sposobnostl<br />

may v gutah. Avtorskoe svidetelstvo<br />

na izobreteuie N 580268 Otkritiya.<br />

Izobreteniya D. 42.<br />

6. Vyalov S.S. (1978). Reoiogicheskie osnovi<br />

rnehaniki gruntov. Visshaya shkola.<br />

8.447. !dOSkva.<br />

7. Vyalov S.S., Mirenburg Yu.S., Fokin V.A.<br />

(1979). 0 vozmojnosti ispoleovanlya<br />

remltatov ispitaniy rnerzlih gruntov na<br />

polauchest dlya raschetov osnovaniya PO<br />

dvum predelnim sostoyaniyam s uchetom<br />

reologicheskih svoystv grmntov. Gidrotehnicheskoe<br />

stroitelstvo v ray<strong>on</strong>ah<br />

vechoy merzloti i surovogo klimata.<br />

Energiya, a.27-31, Leninpad.<br />

8. VyaLov S.S., klirenburg Yu.S. (1980). Osadki<br />

i nesushaya sposobnost osnovaniy, slojennih<br />

slabimi gruntami s uchetom ih nelineynosti<br />

i polzuchesti. VI Dunaysko-<br />

. . Wropeyskaya k<strong>on</strong>ferenziya po mehanike<br />

,i<br />

,. . gruntov i fundaaenfzo-stroeniyu, s.387-<br />

396, Varna, Bolgariya.<br />

9. Vyalov S.S., Birenburg 1u.S. (1984). Prognoz<br />

dlitelnih osadok wsynich furidamentov.<br />

Trudi instituta NII osnovaxiy i podzemnih<br />

sooru j eniy , vip. 74, s. 88-98.<br />

Fig.4, Comparis<strong>on</strong> of full-size plot<br />

for settling progress <strong>on</strong><br />

piie N.5 in stepped loading<br />

with that computed from dynamometric<br />

test data for bhhe<br />

same pile.<br />

a. Stepped variati<strong>on</strong> of loading<br />

in tests ; b. Experimental<br />

test data (1) and design plotted<br />

data (I).<br />

1 340

CLASSIFICATION OF FROZEN HEAVE OF GROUND FOR HYDRAULIC<br />

ENGINEERING IN SEASONAL FROZEN REGIONS<br />

Xie, Yinqi, Wang, Jlanguo and Yian, Weijun<br />

Heil<strong>on</strong>gjiang Provincial <strong>Research</strong> Institute of Water C<strong>on</strong>servancy<br />

SYNOPSIS<br />

In order to satisfy the requirements of hydraulic engineering, the frost heave<br />

.property is classified into five types with absolute values of frost heave amount. On the basis of<br />

statistical analysis, the formulas are provided to calculate frost heave amount which is relative<br />

to the c<strong>on</strong>diti<strong>on</strong>s of density, freezing index, ground water table and surcharge load.<br />

PREFACE<br />

In China, seas<strong>on</strong>al frozen ground mainly distributes<br />

in the south and north temperate z<strong>on</strong>es<br />

and the mountain areas of the north subtropical<br />

z<strong>on</strong>e (Xu and Wang,1983),of which the total area<br />

is about 5.137 milli<strong>on</strong> square kilometers and<br />

takes 53.5% of the area of China. In seas<strong>on</strong>al<br />

frost areas, frost heave of soil has caused a<br />

large number of damages in verying degrees for<br />

various engineering c<strong>on</strong>structi<strong>on</strong>s, such as water<br />

c<strong>on</strong>servancy project, bridge, highway, pipeline.<br />

railway, airport and other buildings.Classificati<strong>on</strong><br />

of frost heave of soil, which ic called the<br />

evaluati<strong>on</strong> of freezing sensitivity in some countries,<br />

reflects the research level and trend in<br />

some degree. Up to now, over <strong>on</strong>e hundred kinds<br />

of classificati<strong>on</strong> methods of soil frost heave<br />

have been suggested in China and abroad, some of<br />

which have been brought into the relevant criteria<br />

(Ministry of Communicati<strong>on</strong>, PRC, 1975;<br />

Nati<strong>on</strong>al C<strong>on</strong>structi<strong>on</strong> Committee, PRC,,1974). In<br />

China, since 1960's, al<strong>on</strong>g with the development<br />

of ec<strong>on</strong>omy, the problem of engineering freeze<br />

damage in seas<strong>on</strong>al frost area has been paid much<br />

attenti<strong>on</strong>. For various trades with the classificati<strong>on</strong><br />

standards of frost heave in seas<strong>on</strong>al<br />

frost area were provided, but there is no any<br />

standard for water c<strong>on</strong>servancy projects.<br />

In recent years, in China and abroad a lot of<br />

research work and engineering practise.have<br />

testified that frost heave of foundati<strong>on</strong> soil<br />

is not <strong>on</strong>ly relative to the factors of soil<br />

particle size. water c<strong>on</strong>tent and ground water<br />

'cable, but also closely related to engineering<br />

measures or c<strong>on</strong>diti<strong>on</strong>s(Chen et al., 1978; T<strong>on</strong>g<br />

et al., 1985). For example, under the prerequisite<br />

of not changing the soil compositi<strong>on</strong>, both<br />

the ground ramming and the additi<strong>on</strong>al load of<br />

c<strong>on</strong>structi<strong>on</strong> will greatly affect the frost heave<br />

property of ground. This shows that, if the<br />

ground soil is regarded as a system, ramming<br />

will change the inner texture of a system, which,<br />

in microscopic view, is that the increase of<br />

soil density changes the frost heave functi<strong>on</strong><br />

of the system. The additi<strong>on</strong>al load, as the<br />

envir<strong>on</strong>mental c<strong>on</strong>diti<strong>on</strong>, al<strong>on</strong>g with the c<strong>on</strong>diti<strong>on</strong>s<br />

of temperature and water will also obvi-<br />

ously change the frost heave functi<strong>on</strong> of the<br />

system.<br />

The authors c<strong>on</strong>sider that a classificati<strong>on</strong> in<br />

frost heave should be faced <strong>on</strong> the following<br />

ptinciples e.i. it should be able to reflect<br />

the features of speciality and engineering, its<br />

quantitative indexes should be clear and direct:<br />

these indexes should be easy to determine. and<br />

could be applied to engineering design practically,<br />

The main c<strong>on</strong>tents of classificati<strong>on</strong><br />

should c<strong>on</strong>tain (1) classifying the frost heave,<br />

(2) the quantitative indexes of classifying '<br />

frost heave, and (3) the determining method of<br />

quantitative indexes.<br />

Selecti<strong>on</strong> <strong>on</strong> indexes for classificati<strong>on</strong> is <strong>on</strong>e<br />

of the key problems. The current classificati<strong>on</strong><br />

principles are mostly based <strong>on</strong> the average frost<br />

heave rate (in America) or the frost heave ratio<br />

(such as Ollove's classificati<strong>on</strong> in Soviet Uni<strong>on</strong>),<br />

the former must be specified in laboratory with<br />

special instruments and foi the latter,the same<br />

frost heave ratio will have quite different: frost<br />

heave amount in the areas of having different<br />

frozen depth. This will make the classificati<strong>on</strong><br />

very c<strong>on</strong>fused. Although the absolute value of<br />

frost heave amount is nor very large, it will<br />

be put into the class of str<strong>on</strong>g frost heave because<br />

of the small frozen depth. In the opposite,<br />

although the absolute value of frost heave<br />

amount is very large, it will be put into the<br />

lower class of frost heave because of the large<br />

frozen depth.<br />

It is obvious that the indexes of specifying<br />

frost heave classes must be clear, and should<br />

be able to directly and quantitat'ively reflect<br />

the possible degree of damage of ground frost<br />

heave to c<strong>on</strong>structi<strong>on</strong>, that is, the "adaptati<strong>on</strong>"<br />

degree for the permissible deforming of ground<br />

soil and c<strong>on</strong>structi<strong>on</strong>s. Thus, it might be better<br />

to apply the absolute value of frost heave<br />

as the quantitative index for classificati<strong>on</strong>.<br />

C<strong>on</strong>sidering that a same frost heave amount may<br />

cause various degrees of damages to different<br />

types of c<strong>on</strong>structi<strong>on</strong>s, and even the sensitivities<br />

of different parts of a c<strong>on</strong>structi<strong>on</strong> to<br />

1341

frost heave are not completely the same, so that<br />

the authors do not adopt the traditi<strong>on</strong>al terms,<br />

such as no frost heave, weak frost heave and<br />

str<strong>on</strong>g frost heave, as the names of various<br />

classes, but classify frost heave into five<br />

classes from weak to str<strong>on</strong>g.<br />

Since the simulati<strong>on</strong> law o f model experiment of<br />

frost in laboratory have been not perfect, the<br />

authors took the indoor experiment as the means<br />

to examine the qualitative effect of various<br />

factord <strong>on</strong> frost heave, and took the frost heave<br />

amount obtained from field work as the quantitative<br />

basis, then proposed the engineering classificati<strong>on</strong><br />

standard of ground frost heave property,<br />

which is suitable to the hydraulic structures<br />

in seas<strong>on</strong>al frost area. The analytical<br />

equati<strong>on</strong>s of claculating frost heave amount<br />

provided in this paper may also be regarded as<br />

the references of making engineering programme<br />

and frost heave forecast for the areas without<br />

observati<strong>on</strong> data.<br />

(ii) ..<br />

(iii)<br />

weigh.<br />

Sandy soil: it c<strong>on</strong>sists of sandy Soil<br />

with a Eine c<strong>on</strong>tent lower than 15% of<br />

total weight.<br />

According to the frost heave amount distributing<br />

with depth, frost heave may<br />

be classified into three types: first,<br />

the frost heave is at the upper part of<br />

soil column; sec<strong>on</strong>d, it is high at the<br />

lower part of soil column: and the third.<br />

it is homogeneuous through the whole<br />

column. In a close system. it can <strong>on</strong>ly<br />

be the first type.<br />

An incfease in density of clayey soil<br />

will obviously reduce the frost heave<br />

amount. The effect of density <strong>on</strong> frost<br />

heave can be expresses with the denaity<br />

reducing coefficient dyand calculated by<br />

means of Eq.(2),<br />

dy= l-EXP[-5.0('Yd-1.35)1 (2)<br />

LABORATORY AND FIELD EXPERIMENTAL RESEARCH ABOUT<br />

THE BASIC RULES OF GROUND FROST HEAVE<br />

In China and abroad, many scientists have made<br />

a lot of experimental research about unitary and<br />

multiple factors affecting frost heave of ground.<br />

For a certain kind of soil with certain texture,<br />

its frost heave amount h is the functi<strong>on</strong> of<br />

mult.iple factors:<br />

h f (F,w,z,Yd,P,,AS,Hf,Vf) (1)<br />

where, F-freezing index:<br />

W-prefreezing water c<strong>on</strong>tent-of soil;<br />

Z-ground water table prefreezing;<br />

yd-density of soil;<br />

Pi-surcharge load;<br />

AS-compress amount of underlain unfrozen<br />

soil;<br />

Hf-frozen depth;<br />

Vf-freezing speed.<br />

For the fixed soil structure, W and Yd are the<br />

major factors of internal structures of system<br />

(Xie, 1982); the envir<strong>on</strong>mental temperature F,<br />

the envir<strong>on</strong>mental water c<strong>on</strong>diti<strong>on</strong> Z and the<br />

envir<strong>on</strong>mental engineering factor Pi are the main<br />

factors in envir<strong>on</strong>mental c<strong>on</strong>diti<strong>on</strong>s, and frost<br />

heave, as a behavior of system, is c<strong>on</strong>trolled by<br />

the major, structural and envir<strong>on</strong>mental factors<br />

as above. In order to provide reliable basis for<br />

the engineering classificati<strong>on</strong> o f ground frost<br />

heave, the'authors have c<strong>on</strong>tinuosuly made experimental<br />

research <strong>on</strong> the basic rules of soil frost<br />

heave for eight years.<br />

Eq.(2) adoptfble to soils with a density<br />

ydk1.35 g/Cm ;<br />

(i.V) Ground water table is <strong>on</strong>e of major envir<strong>on</strong>mental<br />

factors affecting frost heave,<br />

which indicates the freezing type of<br />

system-close or open (Ding, 1983).0nly<br />

for open system, the 1st and 2nd types<br />

of frost heave can occur. A saturated<br />

soil, freezing in an open system will<br />

form the str<strong>on</strong>g frost heave.<br />

(VI The surcharge load Pi, as a. engineering<br />

factor in envir<strong>on</strong>mental c<strong>on</strong>diti<strong>on</strong>, will<br />

str<strong>on</strong>gly restrain the frost heave of<br />

ground. This acti<strong>on</strong> will be weakened<br />

with the increasing of density of ground<br />

soil. The reducing coefficient dp may<br />

be calculated with Eq.(3).<br />

dp = 1 - ebPi (3)<br />

Eq,(3) is adoptable to sofls under 8<br />

surcharge of PiS3.0 kg/cm .<br />

where b-is relative to soil dens i ty, and<br />

may be calculated with the Eq.(4<br />

.,<br />

(4)<br />

The values of b also can be obtai ned<br />

from Fig.1.<br />

(i)<br />

The frost heave property of soil is<br />

closely relative to the particle size<br />

compositi<strong>on</strong>, <strong>on</strong>ly the fine grained soil<br />

possesses the mechanism of causing<br />

str<strong>on</strong>g water migrati<strong>on</strong>. Based <strong>on</strong> the<br />

com~ositi<strong>on</strong> in particle size, soil can<br />

be ilassified into two g roups.<br />

Clayey soil: it c<strong>on</strong>sists of fine-grained<br />

soils and some sandy soi 1s with a fine<br />

((0.05 mm) c<strong>on</strong>tent over 15% of total<br />

Yd (r/cm2)<br />

Fig.1 Dependence of Coefficient b <strong>on</strong> Yd<br />

b-coefficient related to density of soil

THE STATlSTICAL ANALYSIS OF GROUND FROST HEAVE<br />

A statistical analysis was made based <strong>on</strong> the<br />

basic rules of frost heave discussed above, the<br />

data presented at the previous Chinese Nati<strong>on</strong>al<br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>s <strong>on</strong> Hydraulic C<strong>on</strong>structi<strong>on</strong> and Antifreezing<br />

Technics and the Nati<strong>on</strong>al <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>s<br />

<strong>on</strong> <strong>Permafrost</strong>, and those obtained from 43 sites<br />

in the Heil<strong>on</strong>gjiang Province. The extreme values<br />

of frost heave of clayey soil and sandy soil, 671<br />

and 133 in number respectively, were selected<br />

for statistics. These data were from an area<br />

ranging from 36" to 50.2'N and 84" to 132'E,<br />

relative to Xinjiang, Qinghai, Gansu, Jingxia,<br />

Shanxi, Beijing, Hebei, Inner M<strong>on</strong>galia, Lia<strong>on</strong>ing,<br />

Jilin and Heil<strong>on</strong>gjiang Provinces (or sity, aut<strong>on</strong>omous<br />

regi<strong>on</strong>). 98% of the data were obtained<br />

from the testing sites of hydraulic c<strong>on</strong>structi<strong>on</strong>.<br />

Because the geographical range is just same with<br />

the seas<strong>on</strong>ally frozen z<strong>on</strong>e of China, and the data<br />

basicly come from the fields of hydraulic engineering,<br />

it is believed that the data used in<br />

this statistics can present nature of the whole<br />

regi<strong>on</strong>, with a sufficient, universality and<br />

reliability.<br />

The results of correlati<strong>on</strong> analysis o f the extreme<br />

value of frost heave vs temperature and water,<br />

the major factors in envir<strong>on</strong>mental c<strong>on</strong>diti<strong>on</strong>s<br />

and the quantitative calculati<strong>on</strong> method are as<br />

follows:<br />

(i)<br />

For clayey s.oil, the outer envelope line<br />

of the maximum frost heave values is<br />

c<strong>on</strong>formed to the good random normal distributi<strong>on</strong><br />

vs freezing index and northern<br />

latitude, and the frost heave amount<br />

reduces exp<strong>on</strong>entially with ground water<br />

table prefreezing, which can be expressed<br />

with the following equati<strong>on</strong>s,<br />

(1) When north latitude D is known,<br />

(2) When freezing index F is known,<br />

where, ' and h+,max are the possible<br />

hD max<br />

maximum value of frost heave (meter)<br />

corresp<strong>on</strong>ding to D and,F for clayey soil;<br />

both OD and oF are characteristic c<strong>on</strong>stants<br />

and equal to 0.88654; UD and UF<br />

are also characteristic C<strong>on</strong>stants, and<br />

UD=lO, vF=2.4O; Xg and XF are the c<strong>on</strong>versi<strong>on</strong><br />

values of abscissa, and X~=0.2222D,<br />

X~=F/650; D denotes north latitude<br />

(degree); F denotes freezing index which<br />

can be <strong>on</strong>e year observati<strong>on</strong> value or the<br />

average value of years (in OC-day); b is<br />

a characteristic c<strong>on</strong>stant and b--0.70;<br />

X is ground water table prefreezing.<br />

(ii) For sandy soil, the outer envelope line<br />

of the maximum frost heave values is<br />

also c<strong>on</strong>formed to the random normal distributi<strong>on</strong><br />

vs north latitude and freezing<br />

index,<br />

(1) When D is known,<br />

(2) When F is known,<br />

where, hb,max and hb,max are the possible<br />

maximum values of frost heave (in meter)<br />

corresp<strong>on</strong>ding to D and 2 €or sandy soil;<br />

us and& are characteristic c<strong>on</strong>stants,<br />

F<br />

and 0:=0.1773, OC=1.773; Llh and are<br />

F<br />

also characteristic c<strong>on</strong>stants, and<br />

ub=21.3, Uke4.53; x; and X: are the c<strong>on</strong>versi<strong>on</strong><br />

values of abscissa, and X6=0.5D,<br />

xC-F/265; d is c<strong>on</strong>stant, and d=0.107;<br />

t; meanings of D and F are same with<br />

those in Eq.(6).<br />

(iii) By synthetical analysis of relati<strong>on</strong>s of<br />

hp,,,,-F and hD,max"D, it was found .<br />

that the ground frost heave does not<br />

m<strong>on</strong>ot<strong>on</strong>ously increase or reduce with the<br />

envir<strong>on</strong>mental factors F and D, but exist<br />

the "optimum" values of F and D for produci'ng<br />

the maximum frost heave amount.<br />

It is believed that the h will increase<br />

with F or D. However, as F or D c<strong>on</strong>es<br />

up to a critical value, an increase in<br />

F or D will result in a decrease of h,.<br />

This could be explained by the fact widly<br />

recognized that if the frost penetrating<br />

speed is much faster than the velocity<br />

of moisture migrati<strong>on</strong>, the frost heave<br />

would decrease.<br />

(iv)<br />

The frost heave amount c<strong>on</strong>tinuously<br />

changes in space (e,g.hma,-D), and<br />

changes with structure c<strong>on</strong>dltl<strong>on</strong> of soil<br />

(eeg.hmax-Z). To explore the inherent<br />

c<strong>on</strong>necti<strong>on</strong> between the two changing<br />

types the whole regi<strong>on</strong> is divided into<br />

three subregi<strong>on</strong>s for statistical analysis<br />

of maximum frost heave amount hmax of<br />

clayey soil vs Z.<br />

(1) There are 208 samples when 42.5

The synthetical statistical analysis of the<br />

maximum value proved the existence of c<strong>on</strong>tinuity<br />

between the maximum frost heave amount and regi<strong>on</strong>al<br />

factors and water c<strong>on</strong>diti<strong>on</strong>.<br />

heave de signing for the a reas without observati<strong>on</strong>al<br />

data. the authors provided the empirical<br />

formulas for determining classificati<strong>on</strong> indexes<br />

as follows:<br />

Besides, €or the three analytical subregi<strong>on</strong>s,<br />

water reducing coefficients b are a ll -0.7, this<br />

shows that at different geographical locati<strong>on</strong>s,<br />

the influence of water c<strong>on</strong>diti<strong>on</strong> to frost heave<br />

is equivalent. This makes a basis for quantitatively<br />

.evaluating the synthetical effect of latitude,<br />

temperature, and water <strong>on</strong> frost heave.<br />

Through the statistical analysis of the freezing<br />

and frost heave observati<strong>on</strong>al values in natural<br />

c<strong>on</strong>diti<strong>on</strong>, the qualitative rules in laboratory<br />

may be quantitatively explained, and finally, the<br />

basis of engineering classificati<strong>on</strong> may be found<br />

out.<br />

(i) The calculati<strong>on</strong> of frost heave amount<br />

for clayey soil<br />

After knowing the annual freezing index,<br />

the ground water table in first 10 days,<br />

the prefreezing average density in frozen<br />

soil layer and the load born <strong>on</strong><br />

ground, the following formula may be<br />

used to calculate frost heave amount<br />

h = (l-dp)(<br />

I<br />

TIIE ENGINEERING CLASSIFICATION IN FROST . - - HEAVE .-.. - OF . GROUND UNDER HYDRAULIC CONSTRUCTION IN EASONAL<br />

FROST AREA<br />

Through the analysis as above, it could be c<strong>on</strong>sidered<br />

that in seas<strong>on</strong>al frost areas, the frost<br />

heave of ground under hydraulic c<strong>on</strong>structi<strong>on</strong>,in<br />

practise, can be divided into five classes, in<br />

which the absolute amount of frost heave is regarded<br />

as the classificati<strong>on</strong> index (Table I).<br />

TABLE I<br />

Eq.(9) is adtptable to the c<strong>on</strong>titi<strong>on</strong> of<br />

yd51.75 g/cm and Pi~3.0 krn/cm ,<br />

where, dp, dy, hblmax may also be cal-<br />

culated by means of Eq.(2), (3) and (6)<br />

respectively.<br />

If the value of F is difficult to obtain,<br />

frost heave amount may be calculated with<br />

the value of north latitude<br />

The Engineering Classificati<strong>on</strong> of Frost<br />

Heave in Ground Under Hydraulic C<strong>on</strong>structi<strong>on</strong><br />

in Seas<strong>on</strong>al Frost Apea<br />

Standard of<br />

frost heave I I1 I11 VI V<br />

class<br />

Frost heave h ~ 2 2

Z (m) 1.0 2.0 8.0<br />

Fig.2 Normograph for Determining the Maximum Value of Frost Heave of Clayey Soil<br />

hA,max, hi,ma,-maximum value of frost heave based <strong>on</strong> D (latitude,in degree) or<br />

F (freezing index, in 'C-day);<br />

yd-density of soil (in g/cm').<br />

Fig.3 Normograph for Determining the<br />

Maximum Value of Frost Heave of Sandy<br />

Soil<br />

Ministry of Communicati<strong>on</strong>s, PRCI(1975).Standard<br />

of design of highway, bridge and culvert,<br />

People's Publishing House.<br />

Nati<strong>on</strong>al C<strong>on</strong>structi<strong>on</strong> Committee, PRC,(1974).<br />

Standard of foundati<strong>on</strong> design of industrial<br />

and civil architecture TJ7-74, Chinese<br />

Architecture Publishing House.<br />

T<strong>on</strong>g Changjiang and Guan Fengnian, (1985). Frost<br />

heave of ground and the preventi<strong>on</strong> and -<br />

c<strong>on</strong>trol.of frost damage of c<strong>on</strong>structi<strong>on</strong>.<br />

pp.265, Publishing House of Water C<strong>on</strong>servancy<br />

and Electric power, Beijing.<br />

Xie Yinqi, (1982). The explorati<strong>on</strong> of using<br />

prossed soil as the foundati<strong>on</strong> of anti-frost<br />

have. Journal of Building Technics <strong>on</strong> Low<br />

Temperature, ( 1 1 .<br />

Xu Xuezu and Wang Jiacheng, (1983), Preliminary<br />

discussi<strong>on</strong> <strong>on</strong> the distributi<strong>on</strong> of frozen<br />

ground and its z<strong>on</strong>ality in China, Proc.2nd<br />

Chinese Nati<strong>on</strong>al <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>,<br />

3-12, Lanzhou.<br />

'<br />

REFERENCES<br />

,Chen Xiaobai, et a1.,(1978). The preliminary<br />

study about the effect of loading <strong>on</strong> frost<br />

heave (abstract)'. Proc.Symposium <strong>on</strong> Glaciology<br />

and dryopedology, (Cryopedology),<br />

126-127, Lanzhou.<br />

Ding Dewen, (1983). The calculati<strong>on</strong> of freezing<br />

depth and moisture c<strong>on</strong>diti<strong>on</strong> in open system.<br />

Proc.2nd Chinese Nati<strong>on</strong>al <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong><br />

<strong>Permafrost</strong>. 191-196, Lanzhou.<br />

1345

RETAINING WALL WITH ANCHOR SLABS USING IN COLD REGION<br />

Xu, Bomengl and Li, Changlinz<br />

1Northeast Design and Explorati<strong>on</strong> Institute, Ministry of Water Resources and Electric Power, P.R.C.,<br />

74 Beian Road, Changchun, China<br />

2Water Resources Institute of Jilin Province, P.R.C.<br />

SYNOS I3 In recent years, we have c<strong>on</strong>ducted field test of horiz<strong>on</strong>tal frost heaving force<br />

<strong>on</strong> model retaining t.lall, as uell as designed and c<strong>on</strong>structed two retaining walls with anchor slabs<br />

in Jilin province being seas<strong>on</strong>ally frozen area of our country. The tests and applicati<strong>on</strong>s indicate<br />

that the anchored retaining ~rall has such advantages as very light in weigh$, ec<strong>on</strong>omic in material,<br />

well flexible and adjustable to a certain extent to the frost heaving of soil and thus, is <strong>on</strong>e of<br />

the fine structure types to prevent it danaginng duo to acti<strong>on</strong> of horiz<strong>on</strong>tal froat heaving force of<br />

soil behind the wall.lChis paper deals with tho teat results and the behavior of experimental walls.<br />

IITTROJIUCTION<br />

The retaining structure with anchor slabs c<strong>on</strong>sists<br />

of the wall face (including columns and<br />

panels), tie-rods, anchor slabs and soil between<br />

them as shown in Pig.1 . Nuch has been d<strong>on</strong>e <strong>on</strong><br />

the investigati<strong>on</strong> and use of suoh structure in<br />

OUT country since TO'S, hovever, limited basically<br />

to the railway and road engineerings of n<strong>on</strong><br />

frost areas. The retaLnninG nall of anchor slabs,<br />

hovever, using in the hydraulic ingineering In<br />

seas<strong>on</strong>ally frozen z<strong>on</strong>es has -3<strong>on</strong>e features of its<br />

own in additi<strong>on</strong> to meet the c<strong>on</strong>a<strong>on</strong> demands <strong>on</strong><br />

this structure as follovs:<br />

The soil behind the wall freezes in cold<br />

xea'chcr and thaws .in ;am seas<strong>on</strong>s, thus ,<br />

the intcrml stability of thLs atrlzcture<br />

nust be satisfied under acti<strong>on</strong> of earth<br />

pressure in warm seas<strong>on</strong>s and horje<strong>on</strong>tal<br />

frost heaving force in winter.<br />

The retaining structure works under high<br />

water table, the so11 behind the wall<br />

has high moisture c<strong>on</strong>tent. Thus the<br />

horiz<strong>on</strong>tal fr<strong>on</strong>t heavin;; force ,@eater<br />

than that ;>.ctin: <strong>on</strong> the retninine mlZ.<br />

using in other cngineerines is resulted<br />

in. herfore, Lt is nccc ssary to neek<br />

effective measures to reduce the heaving<br />

force and correctly decide its value.<br />

The retaining IKCL~ axe often subjected<br />

to the influence oi" rrater florl,<br />

cccpage<br />

should<br />

ma 11;rdrodyn;mlic ppe:;:jlll*e, v L ~ c ~<br />

1346<br />

be taken into<br />

account in the design.

panels were made smooth (Fig.4). !ha wall was 4<br />

m high. The anchor dabs closer to the vall face<br />

were instaled within the freezing depth rrith the<br />

aim of bearing the frost heavLnE reacti<strong>on</strong> force<br />

and aiding the stability against fxost heaving<br />

force (Fig.5).<br />

4<br />

Fig.2 The Plane Five of U<strong>on</strong>ala<br />

Retaining Struoture<br />

4 u<br />

Fig.5 The Cross Beati<strong>on</strong> of Oaantun<br />

Retaining Struct*we<br />

1347

heaving forco will bo little or not in this<br />

layer. Jith the distance from grovnd swiace<br />

inoreasing and being closer to the gound water<br />

level, and the c<strong>on</strong>finewnt to the frost heaving<br />

of soil bec<strong>on</strong>ing str<strong>on</strong>ger, the frost heaving<br />

preasure grows higher and higher. Nevertheless ,<br />

at the bottou part of the wall, frost c<strong>on</strong>diti<strong>on</strong><br />

chnnges because of the influence of the ground<br />

before the vall, which leads <strong>on</strong> to decrease of<br />

the frost heaving force in this part.<br />

Based <strong>on</strong> the results obtained from field tests<br />

and to simplify computati<strong>on</strong>, the distributi<strong>on</strong><br />

pattern of horiz<strong>on</strong>tal frost heaving force versus<br />

the hight of the 'C.rd1 shown in Pig.7 may be<br />

adopted. Pig.7~ is apalioablo provided that the<br />

frost deyth of ground in fr<strong>on</strong>t of the wall is<br />

less than that in b-ckfill of the waJ.J.,otherwise<br />

the Fig. 7b CM be wed.<br />

When using Fig. 7 to compute the horihnta2 heavirQ<br />

pressure, it is important to detomine<br />

magnitude of the c<strong>on</strong>diti<strong>on</strong>al depth without frost<br />

+%<br />

heaving foroe( hl ), frost-heaving areas (hg, h3)<br />

and the maximum frost heaving pressure ( 6 -),<br />

the magnitudes of which all. have to do with the<br />

water c<strong>on</strong>tent, propepties of the soil as well<br />

as the water table. The str<strong>on</strong>ger the frost<br />

heaving of soil, the Greater is the frost<br />

heaving pressure. Under the identioal o<strong>on</strong>diti<strong>on</strong><br />

of soil proerty, 33 tho water c<strong>on</strong>tent and water<br />

table go up, h2 and emX increase but hl<br />

decreases. I,loreover, the hizher the wall,<br />

the larger the value will be if other factors<br />

remain the 3i~ne..<br />

The results achieved so far have indicated that<br />

the ground would not heave before the water<br />

table reaches a certain distance from the around<br />

surface which ia dcfined as orifioal influential<br />

distance (14,) and mainly dependent up<strong>on</strong> the<br />

capillary height. nccording to the existing<br />

research achiovenent3 (Lu B<strong>on</strong>ang, Lu Kingling,<br />

1348<br />

1986, Wang Xiyao, 1982), El, varies from 1 . 5-2.b<br />

for cohesive soil and 0.5-1.0 m for sandy soil.<br />

Therefore, under the circumstances of high 'cuatex<br />

fable, the following formulae can be used to<br />

decide the values of hl and. h2<br />

hg=H,-Z (11<br />

hl cII-h2<br />

(2)<br />

where Zis the buried depth of underground water<br />

in fr<strong>on</strong>t of the wall: H is the height of wall.<br />

Fig.6 Distributi<strong>on</strong> of the Horiz<strong>on</strong>tal<br />

Frost EIeaving Pressure al<strong>on</strong>g<br />

the Height of the Wall<br />

Pig.7<br />

Dingram for Computing Boriz<strong>on</strong>tal<br />

Frost IIeaving Prensure<br />

In Pi~.7a, the value of h3 may usually be taken<br />

about 50 cm. The maximu horiz<strong>on</strong>tal frost heaving<br />

prassure observed appears at the lower art of<br />

the nods1 retaining walls and has the value

generally from 220 to 240 KPa, Howover, the<br />

retaining wall must be deeigned to mod the<br />

requirements of stabilities against slidhng and<br />

overturning, i.e. the.most important to do it is<br />

to docide the magnitudes of the total, frost<br />

heavtng force and resultant moment. For this<br />

reas<strong>on</strong>, taking the maximum horiz<strong>on</strong>tal frost<br />

heaving pressure 6,x=200 ICPa, the cr5tical<br />

influential distance H,=l,6 m(Wang Xiyao, I982),<br />

h3=0.3 m in accordance with our field teoting<br />

results and the measured value of the capillary<br />

rise, at the same tirim, wing tho distributi<strong>on</strong><br />

PaftQm in Fig.7, we have computed tho maximum<br />

values of the total horiz<strong>on</strong>tal frost heaving<br />

foroe and resultant moment. The oomputed and<br />

observed results are liathd In Table 2.<br />

TABLZ 2<br />

Computed and Observed Values of the<br />

Total Horiz<strong>on</strong>tal Frost Heavlng Force<br />

and Resultant !loment Acting <strong>on</strong> a Unit<br />

'rlidth of the Nodel Retaining Walls<br />

r "<br />

1<br />

I Total. ioroe Reaultant moment I<br />

(m)<br />

(KN)<br />

Wall """""""" -""""-<br />

I<br />

"* observed Computed Observed Computed<br />

"" """""<br />

r-"<br />

A 87.5. 130 50.5<br />

B 159.0 150.0 43.3 71 03<br />

C 141 02 180.0 95.2 103- 3<br />

"""""""""""""""""""-""-<br />

'It oan be seen from Table 2 that the computed<br />

values are generally o<strong>on</strong>servative for the safty<br />

of the wall. Thus, it is adoptable to oompute<br />

horiz<strong>on</strong>tal frost heaving foroe acting up<strong>on</strong> the<br />

retaining wall according to Pig.7 with taking<br />

j<br />

structure, tho horiz<strong>on</strong>tal frost heaving force<br />

under allowable deformti<strong>on</strong> ia calculated according<br />

to Pig.S or fomulne (3) and (4) in dosign.<br />

a . ' ' L<br />

Pig.9 Helati<strong>on</strong> bet~cen Ulowabla<br />

Deformati<strong>on</strong> Rate and Reducing<br />

Coefficient of Eeavinz Sorce<br />

,f0* 5 (3)<br />

c-.bmax (4)<br />

in which m is the reducing coefficient of the<br />

frost heaving force, i,w. the rate of frost<br />

heaving pressure corrosp<strong>on</strong>ding to certain deformati<strong>on</strong><br />

and the maximum frost heaving pressure<br />

under full c<strong>on</strong>finement: f is the allowable rate<br />

of defamati<strong>on</strong>, i.e. the rate of the allowable<br />

deformati<strong>on</strong> at a point and the freely frost<br />

heaving capacity of soil behind the wall.<br />

Ino~d9sto let the struotures have greater safty<br />

factors, the measures of filling soil weak in<br />

*<br />

frost heave qnd fabric bags filled with soil. were<br />

used to reduca frost heaving force.<br />

At D<strong>on</strong>mln l>un.p stati<strong>on</strong>,the opze between panels<br />

and excavati<strong>on</strong> surfszce was partly filled with<br />

As menti<strong>on</strong>ed above, the horiz<strong>on</strong>tal frost heaving<br />

force has the maxircum value while the frost<br />

hoaving of soil is fill c<strong>on</strong>fined. As the wall<br />

with anchor slabs has betterflexibility and deformability,<br />

the frost heaving force will to<br />

certain extent decrease. Based <strong>on</strong> the axiating<br />

test data (T<strong>on</strong>g Changjiang, etc., 1985, Xu Zhen-<br />

&ai, 1996) and in c<strong>on</strong>siderati<strong>on</strong> of the snfty Of<br />

against the back OS the vall (see Yig. 5). To<br />

prove the effect of this method, Icboratory test<br />

<strong>on</strong> made1 ret.=ir,ing wall BXS carried out. The<br />

test resulta listed in Table 3 irldicate that the<br />

tensi<strong>on</strong>of tie-rods when using GeotextiZe bags<br />

filled vith soil is about 281; smaller for the<br />

upper tie-rod and 11:: smaller for the lover tierod<br />

than tlmt without gcotextlle bags.<br />

1349

~ ~<br />

TArYLE 3<br />

Tenaile Strees of Tie-Rods with y d<br />

without Vsi& Geotextile Dag8 (PPa)<br />

iklith bzgs<br />

Upper tie-rod<br />

~"""".... "_ ~<br />

93.1<br />

Lover tie-rod 15707<br />

-. "lI""".~"""I"~""""_..".*".I.~ "-.I"<br />

irpper tie-rod 136.6<br />

without bqp<br />

Lover tie-rod 177.8<br />

"" "_"""~~""""""""<br />

1<br />

previously is of enough security.<br />

DESIGN OF iJCHOH SLAB3<br />

The principle problem of anchor sUb design is<br />

to decide the allotmble pull-ouf force and then<br />

according to tie-rod tensi<strong>on</strong> to determine the<br />

area of anchor slabs and the secti<strong>on</strong> size of<br />

tie-rods. is the length of tie-rods is much<br />

greater than frozen depth, the pull-out strength<br />

of anchor slabs in seas<strong>on</strong>ally frozen area is<br />

still dependent up<strong>on</strong> the reeistanoe of the warm<br />

soil in fr<strong>on</strong>t of the slabs. Tn accordanae with<br />

the c<strong>on</strong>diti<strong>on</strong> of the experimental projeote, we<br />

c<strong>on</strong>ducted pull-out test <strong>on</strong> anchor slabs at the<br />

pump stati<strong>on</strong> of i)<strong>on</strong>gnle* Based <strong>on</strong> the results<br />

(see Table 4) , we took 122.5 D a as .the allowab-,<br />

le value in desi,m.<br />

TABL% 4<br />

Pull-out Strength of Anchor Slabs<br />

in Clayey 9011<br />

Size of anchor slabs( <strong>on</strong>) 40x40 8OxllO<br />

mtinate pull-out force(PJ) 39.2 156.9<br />

Length of tie-rods(m) 6 6<br />

Height of filled soil(m) 2 2<br />

my unit weigth(g/cm3) 1.6 1.6<br />

OPZlUTIOB PElu~oiu~~J:ci3 OP THY 3XXPEIIIIlimTAL<br />

PlOJZCTS<br />

Two experimental. projects have been in proper<br />

operati<strong>on</strong> for 3'and 4 years respoctively and<br />

are still in good c<strong>on</strong>diti<strong>on</strong>. Described in Pig.9<br />

is the distributi<strong>on</strong> of measured and design mximum<br />

values of the horiz<strong>on</strong>tal frost heaving proa-<br />

Sure of J<strong>on</strong>gda retaining uall with anchor slabs<br />

al<strong>on</strong>g the wall heipbt. It OM be observed fr<strong>on</strong><br />

. the picture that tho dwi@ approch doocxihed<br />

3 U m i Y<br />

Fig.9 Distributi<strong>on</strong> of .the rteasuxed ana<br />

Design Naximum Values of the<br />

Boriz<strong>on</strong>fal Frost Heaving Pressure<br />

of D<strong>on</strong>gala Retalnlnng Struature<br />

Hany of retaining struot,ures suffered heavy irabt<br />

damage in cold north regi<strong>on</strong>s. The we of the<br />

retaining wall with anohor slabs provides 8.<br />

secure and feasiable new way for aolving the<br />

frost damage.<br />

The horiz<strong>on</strong>tal frost heaving force is the principle<br />

load acting up<strong>on</strong> the retahknng wall of this<br />

type in seas<strong>on</strong>ally frozen regi<strong>on</strong>s. Tt is feasible<br />

using Fig.7 to compute horiz<strong>on</strong>tal frost heaving<br />

pressure in design. The retainhng structure<br />

with anchor slabs is a flexible <strong>on</strong>e easily adjustable<br />

to-frost h<strong>on</strong>vinp; deformati<strong>on</strong>, hence, it is<br />

Peaslble and secure to take tho froat heaving<br />

force under oertah displacement, ih the meantime,<br />

to fill part of the soil wed< in frost<br />

heaving or place geotextile bags filled with<br />

soil behind the wall to diminish the frost henving<br />

force.<br />

The test and applicati<strong>on</strong>s of the retaining wall<br />

vith anohor slabs hdicate that such structure<br />

also has the advantages as less in mas<strong>on</strong>ry work,<br />

low in cost, high in speed of cbnatructi<strong>on</strong>, able<br />

to be precasted and orected and so <strong>on</strong>.<br />

RZFEBXNCES<br />

lhng Xiyao ( 1982) . The frost heave and its<br />

distributi<strong>on</strong> in different layers influened<br />

by shallow groundwater. Journal of<br />

Glaciology and Eeocryology. Vo1.4, No.2.<br />

1350

xu Bornens, Lu Xingling ( 1906) Influence of<br />

moisture a<strong>on</strong>diti<strong>on</strong> <strong>on</strong> frost hoave in clay,<br />

Journal of Glacioloiry and G-eocryology.<br />

VOl.8,<br />

NO..<br />

T<strong>on</strong>: Chacgjinng, Guan Fengnian (1905) Prost;<br />

heave of soil and treatment of frost damage<br />

of engineering structures. P.95.<br />

Li mangkin, Xu Bomeng, Zhen IJUO (19361.<br />

dxporimenfa<br />

of anchor slab retaining wall for<br />

hydraulic enginewings in seas<strong>on</strong>ally frozen<br />

regi<strong>on</strong>. Joux-hal of Northeant Hydraulic<br />

and Hydroelectric Engineering. No.11.<br />

‘Xu Zhcnghai ( I986 1, Approxinlate calculati<strong>on</strong><br />

of the nomL fro3t heaving foroe acting <strong>on</strong><br />

the base of foundati<strong>on</strong>, Journal Of<br />

Glaciology and Geocryology. Vol,B, Nor3,<br />

1351

THAW STABILIZATION OF ROADWAY EMBANKMENTS<br />

J.P.Zarling,' W.A. Braky2 and D.C. Esch3<br />

%chool of Engineering, University of Alaska Fairbanks<br />

2Institute of Northern Engineering, University of Alaska Fairbanks<br />

3State of Alaska, Dept. of Transportati<strong>on</strong> & Public Facilities<br />

SYNOPSIS The thermal degradati<strong>on</strong> of permafrost beneath Alaskan roads leads to expensive<br />

maintenance and repair costs. This study evaluated two .methods to stabilize the thaw. Snow<br />

sheds were built al<strong>on</strong>g two secti<strong>on</strong>s of roadways to shade the ground during summer and prevent<br />

snow from acting as an insulating blanket during winter. The sec<strong>on</strong>d method c<strong>on</strong>sisted of removing<br />

snow during the winter m<strong>on</strong>ths to reduce surface temperature. The res'ults show Chat the<br />

snow sheds were more effective in decreasinq the ground surface temperatures and, as such, the<br />

c<strong>on</strong>cept could be further developed.<br />

INTRODUCTION<br />

The existence of permafrost in northern regi<strong>on</strong>s<br />

has required highway engineers to carefully<br />

examine the effect of c<strong>on</strong>structi<strong>on</strong> <strong>on</strong> the<br />

thermal regime of the ground. In both c<strong>on</strong>tinuous-and<br />

disc<strong>on</strong>tinuous permafrost areas, changing<br />

the ground surface c<strong>on</strong>diti<strong>on</strong> can lead to<br />

thaw degradati<strong>on</strong> of the underlying permafrost,<br />

and subsequent thaw c<strong>on</strong>solidati<strong>on</strong> and settlement<br />

in ice-rich soils. It is well established<br />

that in most northern locati<strong>on</strong>s, a .5OC to 5°C<br />

temperature difference exists between the mean<br />

annual air and ground surface temperatures.<br />

This difference is a functi<strong>on</strong> of slope and<br />

surface orientati<strong>on</strong>, vegetative and snow cover,<br />

ground thermal properties, meteorological<br />

c<strong>on</strong>diti<strong>on</strong>s, and surface and subsurface drainage.<br />

For example , shading the ground surface<br />

from the summer time sun and removing the<br />

insulating snow cover during the winter m<strong>on</strong>ths<br />

should result in the mean annual soil surface<br />

temperature (MASST) approaching equality with<br />

the mean annual air temperature.<br />

If these<br />

modificati<strong>on</strong>s result in lowering the MASST<br />

below O"C, permafrost will tend to be formed or<br />

thaw degradati<strong>on</strong> of the permafrost will be<br />

prevented or stopped.<br />

insulating the ground from the cold air. When<br />

the side slope thaw fr<strong>on</strong>t penetrates into<br />

ice-rich permafrost, c<strong>on</strong>solkdati<strong>on</strong> ana thaw<br />

settlements occux. The effects of this settlement<br />

are sliding or rotati<strong>on</strong> of the slopes and<br />

cracking of the surface.<br />

Air duct systems (Zarling et al., 1983) have<br />

been used as an attempt<br />

to mktigate this<br />

problem. The c<strong>on</strong>cept is to bury a duct or pipe<br />

in each side-slope near the toe of the roadway<br />

with its ends open to the atmosphere. Cold air<br />

by either natural or forced c<strong>on</strong>vecti<strong>on</strong> will<br />

flow through the pipe, cooling and freezing the<br />

surrounding ground. Other alternatives have<br />

been the use of insulati<strong>on</strong> placed in the toe of<br />

fill and c<strong>on</strong>structi<strong>on</strong> of a berm at the toe of<br />

fill (Esch, 1983). However, n<strong>on</strong>e of these<br />

treatments have yet proven totally effective in<br />

preventing slope thawing and movements.<br />

In disc<strong>on</strong>tinuous permafrost areas, the MASST of<br />

the paved roadway may be above OOC. In this<br />

case, no amount of insulati<strong>on</strong> or fill will<br />

prevent thaw degradati<strong>on</strong>, <strong>on</strong>ly SLOW it down.<br />

Berg et al. (1983) have applied white and<br />

yellow paint and several other surface treatments<br />

to pavements in an attempt to lower the<br />

In the cooler Arctic regi<strong>on</strong>s the most comm<strong>on</strong> MASST. As their study dem<strong>on</strong>strated, a painted<br />

method of protecting a roadway c<strong>on</strong>structed over roadway surface does yield a lower surface<br />

permafrost against thaw settlement is through temperature, but traffic quickly degrades the<br />

the use of gravel fill of sufficient depth to high solar albedo of the surface. Additi<strong>on</strong>alc<strong>on</strong>tain<br />

the active layer. As the MASST in- ly, there are safety c<strong>on</strong>siderati<strong>on</strong>s when using<br />

creases the required fill thickness increases. painted roadway surfaces which become slippery<br />

The use of fill becomes unec<strong>on</strong>omical as the when wet.<br />

MASST approaches O T . The fill thickness can<br />

be reduced through the use of rigid foam<br />

This study addresses two snow management<br />

plastic insulati<strong>on</strong> (Esch, 1973, 1983). Al- schemes in an attempt to achieve colder roadway<br />

though the fill will protect the permafrost<br />

slope surface temperatures. The scope of the<br />

beneath the center of the roadway, the sloping project was to build snow sheds al<strong>on</strong>g two<br />

of the fill to zero thickness at the toe of the secti<strong>on</strong>s and to remove the snow cover al<strong>on</strong>g <strong>on</strong>e<br />

embankment allows this regi<strong>on</strong> to experience<br />

secti<strong>on</strong> of roadway embankments. The snow sheds<br />

thaw degradati<strong>on</strong>. This is further exacerbated were designed to shade the ground surface from<br />

by plowing snow from the roadway during winter, the sun during summer and to prevent the snow<br />

which increases the thickness of snow cover <strong>on</strong> cover from insulating the ground surface during<br />

the side-slopes and the toe z<strong>on</strong>e, further<br />

winter,<br />

1352

~<br />

+ Tf<br />

THEORETICAL CONSIDERATIONS<br />

In the vicinity of B<strong>on</strong>anza Creek, the roadway<br />

alignment required an embankment ranging from<br />

A measure of the annual freezing or thawing<br />

6.7 to 7.6 m in height over frozen muskeg.<br />

potential at the surface of the ground is the Overlying the permafrost at this site is a .3<br />

surface freezing or thawing index. These to .6 m thick layer of peat moss, and scattered<br />

indices are defined as the annual summati<strong>on</strong> of black spruce. Frozen organic silts were<br />

the surface freezing or thawing degree days for present beneath the surficial peat layer.<br />

the freezing or thawing seas<strong>on</strong>.<br />

Frozen water c<strong>on</strong>tents of the silt ranged from<br />

30 to 380%, averaging about 100% by weight of<br />

Because air temperatures and air freezing the dry soil fracti<strong>on</strong>. No massive ice was<br />

(A.F.I.) and thawing (A.T.I.) indices are encountered in prec<strong>on</strong>structi<strong>on</strong> borings. The<br />

generally available for most locati<strong>on</strong>s, empiri- design embankment height was initially believe<br />

cal factors known as surface n-factors have sufficient to prevent seas<strong>on</strong>al thaw penetratio<br />

been determined for many surfaces for both the into the underlying permafrost beneath the<br />

freeze and thaw seas<strong>on</strong>s in order to relate paved roadway. However, side slope thawing and<br />

surface to air temperatures (Lunardini, 1981). related slope movements were anticipated. To<br />

Surface n-factors are defined as the ratio of retard these movements, three different experi<br />

the surface freezing or thawing index to the mental side slope modificati<strong>on</strong>s were selected<br />

air freezing or thawing index. It can be shown for field evaluati<strong>on</strong> when the road was c<strong>on</strong>that<br />

the mean annual surface temperature be can structed. Seven roadway secti<strong>on</strong>s with differestimated<br />

as<br />

ent combinati<strong>on</strong>s of berms, air ducks and<br />

insulati<strong>on</strong> were c<strong>on</strong>structed in 1974 and have<br />

nt(A.T.I.) - nf (A.F.I*)<br />

MASST =<br />

365<br />

Decreasing the surface thaw n-factor and<br />

increasing the surface freeze n-factor will<br />

yield a lower MASST. A measure of a system's<br />

performance in changing the MASST is directly<br />

related to the surface n-factors or surface<br />

freeze and thaw indices.<br />

SITE LOCATIONS AND DESCRIPTIONS<br />

The two sites selected for study were<br />

at<br />

B<strong>on</strong>anza Creek, approximately 50 km west of<br />

Fairbanks, Alaska <strong>on</strong> the Parks Highway, and <strong>on</strong><br />

Farmer's Loop Road, just west of the City of<br />

Fairbanks and adjacent to the University of<br />

Alaska Fairbanks campus.<br />

been m<strong>on</strong>itored since 1975. Vertical and<br />

horiz<strong>on</strong>tal thermocouple strings were installed<br />

and read m<strong>on</strong>thly in each secti<strong>on</strong>, and slope<br />

movement reference stakes have been surveyed<br />

annually, Esch (1983) presented a detailed<br />

analysis of the three methods (insulati<strong>on</strong><br />

layers, air ducts and toe berms) based <strong>on</strong><br />

extensive subsurface temperature and slope<br />

movement observati<strong>on</strong>s. After eight years of<br />

service, the embankment at this site was<br />

seriously distressed due to permafrost thaw and<br />

related slope movements. Lateral movements and<br />

vertical settlements of the slope reference<br />

stakes exceeded 1.5 m vertically and 1.8 m<br />

laterally in some places.<br />

Portable recorders were installed in 1975 at<br />

the B<strong>on</strong>anza Creek site to c<strong>on</strong>tinually measure<br />

surface temperatures of the pavement and of the<br />

2:1 side slopes which faced north and south.<br />

During four years of observati<strong>on</strong>, the annual<br />

surface temperatures were .5OC for the pavement<br />

10cm BRACING<br />

-<br />

PERMAfROSf DEP<br />

t 5<br />

METERS<br />

TC STRING #6-<br />

-TC STRING #7

and 1.9'C and 5.O0C for the north and south<br />

facing slopes, respectively. Average surface<br />

thawing n-factors were 1.05, 0.40 and 0.45,<br />

respectively, for the three suxfaces. The mean<br />

annual air temperature for this period was<br />

-2.7OC. Because n<strong>on</strong>e of seven original (1975)<br />

experimental treatment secti<strong>on</strong>s prQved effective<br />

in preventing slope movements, the snow<br />

shed design was developed and c<strong>on</strong>structed over<br />

the existing instrumented c<strong>on</strong>trol secti<strong>on</strong>.<br />

Figure 1 shows a cross-secti<strong>on</strong> view of the<br />

embankment and of the annual 1984 thaw depth<br />

beneath the snow sheds. The secti<strong>on</strong> selected<br />

for snow removal had a 6 . I m wide toe berm and<br />

had also been instrumented and m<strong>on</strong>itored since<br />

1975.<br />

At the Farmer's Loop site the four lane roadway<br />

was c<strong>on</strong>structed in 1970 by widening an older<br />

two lane secti<strong>on</strong>, originally built in 1963,<br />

crossing a muskeg underlain by permafrost. The<br />

foundati<strong>on</strong> soils at this locati<strong>on</strong> c<strong>on</strong>sist of<br />

ice-rich peat deposits underlain by gray<br />

organic silts with massive ice wedges. The<br />

peat deposits range in thickness from .6 to 3m.<br />

The peat is generally perennially frozen at a<br />

depth of .6 to 1.2 m below the original muskeg<br />

surface, except where heat gain by roadway side<br />

DATA ANALYSIS<br />

slopes has caused progressively deeper thawing.<br />

Temperature data were recorded beginning in<br />

July of 1985 at the B<strong>on</strong>anza Creek site<br />

October of 1985 at the Farmer's Loop<br />

THAW STABILIZATION METHODS<br />

Snow Sheds<br />

Seven snow sheds, each 9.8 m in length by 3.7 m<br />

in width, were c<strong>on</strong>structed adjacent to <strong>on</strong>e<br />

another at the B<strong>on</strong>anza Creek site <strong>on</strong> the south<br />

facing embankment slope. The combined structure<br />

covered a total area of 251m2 (25.6 x 9.8<br />

m) and a length of 25.6 m of embankment slope.<br />

Roof trusses with a 3.7 m span, 1:4 pitch and<br />

1354<br />

.6 m overhang (eave) were c<strong>on</strong>structed of<br />

nominal 5 x 10 cm lumber. The trusses were<br />

erected <strong>on</strong> -6 m centers and supported <strong>on</strong><br />

sleepers placed <strong>on</strong> the ground running down the<br />

roadway side slope. The trusses were then<br />

decked with 1.27 cm thick plywood to form the<br />

roof. Plywood was also nailed <strong>on</strong> the upper and<br />

lower ends, and the l<strong>on</strong>gitudinal wall of the<br />

snow sheds. A gap was left open at the top of<br />

the l<strong>on</strong>gitudinal wall to allow adequate<br />

ventilati<strong>on</strong> while avoiding snow accumulati<strong>on</strong><br />

within the shed. The sheds were oriented with<br />

ventilati<strong>on</strong> gaps facing away Erom the directi<strong>on</strong><br />

of traffic, to prevent plows from throwing snow<br />

into the sheds. Following c<strong>on</strong>structi<strong>on</strong>, the<br />

snow sheds were spray painted white to reflect<br />

,solar radiati<strong>on</strong> during the summer m<strong>on</strong>ths.<br />

Figure 2 shows the pattern of snow accumulati<strong>on</strong><br />

<strong>on</strong> the sheds in March. Note the ventilati<strong>on</strong><br />

openings.<br />

Eight thermocouples were installed to indicat9<br />

air temperatures and ground surface temperatures<br />

inside and outside the snow sheds.<br />

Figure 3 shows the general locati<strong>on</strong> of these<br />

thermocouples. A Campbell Scientific Model 21X<br />

eight-channel portable data logger was located<br />

adjacent to the snow sheds to log temperature<br />

data. Once a m<strong>on</strong>th the temperature dqta were<br />

transferred to a cassette tape, and the lead<br />

acid battery -powering the data logger was<br />

replaced with a fully charged <strong>on</strong>e. The cassette<br />

data tape was then brought back to the<br />

University for data analysis <strong>on</strong> a rnicrocomputer<br />

.<br />

The snow shed c<strong>on</strong>structed at the Farmer's Loop<br />

site measured 4.25 x 7.3 m covering an area of<br />

2<br />

31 m as shown in Figure 4. For this installati<strong>on</strong>,<br />

the trusses were erected perpendicular to<br />

the roadway with c<strong>on</strong>structi<strong>on</strong> and materials<br />

similar to those used at the B<strong>on</strong>anza Creek<br />

site. Air temperature was measured outside the<br />

snow shed in a weather shelter. Ground surface<br />

temperatures were measured at <strong>on</strong>e locati<strong>on</strong><br />

outside the snow shed and two points beneath<br />

the snow shed.<br />

Snow Removal Area<br />

A berm next to the embankment at the B<strong>on</strong>anza<br />

Creek site was kept clear of snow during the<br />

winterof 1985-86. The size of theregi<strong>on</strong><br />

2<br />

cleared was 6 x 21 m or an area of 126 m . The<br />

snow was removed <strong>on</strong>ce a m<strong>on</strong>th if accumulati<strong>on</strong><br />

had occurred.<br />

and<br />

site.<br />

Temperature data were recorded for the entire<br />

thawing and freezing seas<strong>on</strong> between October,<br />

1985 and October, 1986. The output of the<br />

thermocouples was sampled at 60 minute intervals,<br />

and then a daily average was calculated<br />

and stored by the data logger. A microcomput-<br />

er was used to calculate mean m<strong>on</strong>thly soil<br />

surface and air temperatures, and freezing or<br />

thawing degree days as appropriate. The ratio<br />

of surface freezing or thawing degree days to<br />

air freezing or thawing degree days were

STATION 160+20 STATION 166+75<br />

" - 0 - - -<br />

F,<br />

" v<br />

PARKS HIGHWAY FAIRBANKS "+<br />

'\LOPE REFERENCE /O<br />

STAKES<br />

0<br />

0<br />

0<br />

P<br />

'0<br />

0<br />

0<br />

AIR lt<br />

0<br />

SURFAEE<br />

o m<br />

0<br />

0<br />

SJRFAEE<br />

TC<br />

T<br />

N<br />

0<br />

STATION 186+35<br />

TC SIRING 1-3<br />

AIR TE STATION 168+M<br />

0 Tc STRING5 4-7<br />

Figure 3.<br />

B<strong>on</strong>anza Creek snow sheds showing thermocouple placement and slope reference stakes.<br />

TABLE I<br />

Temperatures at the snow sheds ("C)<br />

B<strong>on</strong>anza Creek Farmers<br />

Air Ground Air<br />

M<strong>on</strong>th Amb ient In Shed Exposed In Shed No Snow M<strong>on</strong>th Ambient Exposed In Shed<br />

08/85 12.1 11.3<br />

09/85<br />

10/85<br />

4.7<br />

-8.1<br />

4.4<br />

-1.7<br />

11/85 -20.2 -19.1<br />

12/85 -15.1<br />

01/86 -20.4<br />

-14.2<br />

-19.4<br />

02/86 -14.9 -14.3<br />

03/86<br />

04/86<br />

-15.5<br />

-5.6<br />

-15.6<br />

-6.4<br />

05/86 8.0 6.1<br />

06/86 16.2 14.5<br />

07/86 17.3 16.1<br />

AVG . -3.5 -3.6<br />

_"<br />

"-<br />

15.1 8.3<br />

7.5 3.5<br />

-0.9 -2.1 -"<br />

-4.8 -9.4 -"<br />

-3.2 -8.5<br />

-4.7 -11.9 -8.7<br />

-4.9 -10.0 -10.0<br />

-5.8 -11.8 -10.9<br />

-0.1 -5.8 -4.2<br />

10.1 1.9 8.1<br />

18.4 7.7<br />

"*<br />

20.7 11.0<br />

3.9 -2.3 "-<br />

11/85 -21.5 -3.2 -11.1<br />

12/85 -15.2 -3.7 -9.8<br />

01/86 -21.1 -5.7 -13.1<br />

02/86 -16.7 -6.1 -12.2<br />

03/86 -15.4 -6.7 -12.6<br />

04/86 -4.7 -3.1 -5.4<br />

05/86 8.9 7.8 4.1 -<br />

06/86 16.1 14.1 11.1<br />

07/86 16.9 15.4 13.7<br />

08/86 11.8 10.8 9.8<br />

09/86 6.7 6.2 5.7<br />

10/86 -4.4 0.1 -0.7<br />

AVG . -3.2 2.1 -1.7<br />

calculated for each m<strong>on</strong>th, as well as for the whereas the ground surface in the area where<br />

freezing and thawing seas<strong>on</strong>s. The results of the sheds were subsequently located was 5.O0C,<br />

the data analysis are presented in Table I for ;more than 7 ,T0C above mean annual air temperathe<br />

B<strong>on</strong>anza Creek and Farmer's Loop sites. ture. The l<strong>on</strong>g-term average maximum snow depth<br />

at a site near the study area -56 is cm. It is<br />

B<strong>on</strong>anza Creek Site<br />

interesting to note that the mean annual grou<br />

The data shown in Table T allows an evaluati<strong>on</strong> surface temperature for 1985-86 was 3.9'C<br />

of the performance of the snow sheds at the outside the snow shed <strong>on</strong> the south slope.<br />

B<strong>on</strong>anza Creek site in seducing the ground Therefore, we c<strong>on</strong>clude that the snow sheds ha<br />

surface temperature. The maximum snow depth<br />

had a major effect <strong>on</strong> cooling the ground.<br />

during the winter of the study period was 30.5<br />

cm. The mean annual air temperature for the The n-factor data from 1975-79 and 1985-86 are<br />

period of August 1985 through July 1986 was summarized in Table If for the B<strong>on</strong>anza Creek<br />

-3.5'C, while the average ground surface<br />

site. When ,compared to the undisturbed exposed<br />

temperature beneath the sheds was -2.3OC or slope, the snow sheds approximately doubled t<br />

1.2'C above air temperature. The mean annual surface freeze n-factor and halved the surface<br />

air temperature for the four-year period<br />

thaw n-factor. Improved protecti<strong>on</strong> for the<br />

beginning in 1975 for this site was -2.7OC, underlying permafrost resulted from this<br />

1355

TABLE I1<br />

N-factor comparis<strong>on</strong>s from the 1975-79'data<br />

and the 1985-86 data at B<strong>on</strong>anza Creek.<br />

Exposed Slope Snow Shed Air thawing<br />

1975-79 1985-86 1985-86 and freezing<br />

indices 1985-86<br />

nt 1.72 1.25 0.55 1,767 Co-day<br />

nf 0.40 0.28 0.59 3,068 co-day<br />

increased winter cooling and reduced summer<br />

warming of the ground surface. The exposed<br />

embankment slope surface n-factors for the two<br />

observati<strong>on</strong> periods differed significantly as<br />

shown in Table 11. These differences in<br />

n-factors may be the result oE different solar<br />

exposure due to vegetati<strong>on</strong> growth differences<br />

and sensor positi<strong>on</strong>ing, and to differences in<br />

wintertime snow depths.<br />

Farmer's Loop Site<br />

Data were recorded at the Farmer's Loop Road<br />

snow sheds starting in August of 1985. At the<br />

completi<strong>on</strong> of <strong>on</strong>e annual temperature observati<strong>on</strong>s<br />

cycle, the n-factor data show the same<br />

trend as the data from B<strong>on</strong>anza Creek. Table<br />

111 summarizes this n-factor data.<br />

TABLE 111<br />

N-factor data from the Farmer's Loop snow sheds.<br />

"t<br />

"f<br />

Exposed slope Snow shed Air thawing and<br />

1985-86 1985-86 freezing indices<br />

1985-86<br />

.88 .66 1,649 CO-day<br />

.30 .67 2,976 C'-day<br />

During the test period the mean annual air<br />

temperature, mean annual soil surface temperature-exposed,<br />

and mean annual soil surface<br />

temperature with snow sheds were -3.2OC, 2.1'C<br />

and -1.7"C, respectively. The maximum snow<br />

depth attained at the site during this period<br />

was approximately 30 cm while the l<strong>on</strong>g-term<br />

average maximum at a site near the study area<br />

is 61 cm. Again, the effect of the snow shed<br />

is to reduce the ground surface temperature, in<br />

thiscase by 3.9OC. The meanannualsoil<br />

surface temperature beneath this snow shed is<br />

-1.7'C and as a result, refreezing and<br />

stabilizati<strong>on</strong> of the embankment slope should<br />

occur over a period of time. The surface<br />

thawing n-factor €or the exposed slope is about<br />

<strong>on</strong>e-half the value for the same parameter at<br />

B<strong>on</strong>anza Creek. This is most likely explajned<br />

by the heavier vegetative ground cover, the<br />

lower slope height and the less southerly<br />

exposure of the FarmeY's Loop site.<br />

Snow Removal Area<br />

The benefits of snow removal from the top of<br />

the secti<strong>on</strong> of the embankment berm were not<br />

nearly as notable as at the snow shed secti<strong>on</strong>.<br />

This is to be expected because the snow was<br />

<strong>on</strong>ly removed m<strong>on</strong>thly and the treatment width<br />

was <strong>on</strong>ly 6.1 m. Removal of the snow from the<br />

2:l embankment side slopes was not found<br />

feasible due to the steepness and the presence<br />

of large rocks. Evidence of a benefit from the<br />

snow removal was found during the annual thaw<br />

depth probing surveys, d<strong>on</strong>e in late September<br />

of 1986. At that time a layer of residual<br />

frost approximately 15 cm in thickness<br />

was<br />

encountered beneath the snow cleared areas at a<br />

depth between 1.2 m to 1.5 'm. Probing could<br />

penetrate this layer if c<strong>on</strong>siderable effort was<br />

expended.However, the presenceofresidual<br />

frost from the prior winter at this late date<br />

indicated that the snow removal had the effect<br />

of preventing the further progressi<strong>on</strong> of annual<br />

thawing into the underlying permafrost.<br />

Temperatures recorded at the ground surface <strong>on</strong><br />

the snow removal area did not cover the entire<br />

winter due to equipment problems. Data recorded<br />

are shown in Table I in the "no snow"<br />

column. Extrapolati<strong>on</strong> of this data over the<br />

full seas<strong>on</strong> indicates that the freezing n-<br />

factor resulting from periodic snow removal was<br />

approximately 0.50 and that the average resultant<br />

mean annual surface temperature was very<br />

close to O°C.<br />

At both study sites during the winter seas<strong>on</strong> of<br />

the study period, the snowfall and the maximum<br />

depth of snow accumulati<strong>on</strong> were approximately<br />

half of the l<strong>on</strong>g-term averages of these values.<br />

It could be expected that during a year of<br />

average snowfall the surface freezing index for<br />

exposed ground would be lessened due to the<br />

increase of the insulating ability of the snow<br />

cover. In thia case the usefulness of snow<br />

sheds and snow removal in lowering the MASST<br />

would be accentuated when compared to an area<br />

retaining the natural snowfall through the<br />

winter.

1 .c<br />

0.:<br />

0. c<br />

E<br />

h<br />

-0.5<br />

Y<br />

Y<br />

F -l.O<br />

%. -1.5<br />

-2.0<br />

-2.5<br />

Figure 5.<br />

Maximum annual thaw deaths versus time a at distance of 2.4 m inside of the<br />

embankment toe.<br />

Observati<strong>on</strong>s of Thaw Depth and Slope Movement<br />

At the B<strong>on</strong>anza Creek site, the presence of<br />

previously installed subsurface temperature<br />

sensors permitted an analysis of the effects of<br />

the snow sheds <strong>on</strong> reducing the maximum thaw<br />

depth beneath the side slopes. Figure 5 shows<br />

the changes in thaw depth over time at a<br />

distance of 2.4 m inside of the embankment toe.<br />

Thawing at this locati<strong>on</strong> is especially critical<br />

as the embankment slopes and roadway shoulders<br />

are supported by the soil in this z<strong>on</strong>e. It can<br />

be seen that the additi<strong>on</strong> of the snow sheds<br />

resulted in a reversal of the previous trend<br />

toward deeper thawing each year. In 1986 the<br />

maximum depth of thaw beneath the snow sheds<br />

was observed to be approximately 2.0 m less<br />

than in 1985. This indicates that a thin layer<br />

of permafrost had been formed beneath the<br />

roadway side slope. Calculati<strong>on</strong>s indicate that<br />

the talik in this area would be returned to a<br />

permafrost state in six to eight years. The<br />

shed treatment was the <strong>on</strong>ly method found<br />

successful €or preventing progressively deeper<br />

thawing beneath the lower embankment slopes.<br />

The effectiveness of the sheds in slowing the<br />

slope movements was indicated by annual elevati<strong>on</strong><br />

surveys. Three of the four lower slope<br />

movement reference stakes showed no significant<br />

settlements between the 1984. and 1986 annual<br />

fall surveys. Movements of the roadway surface<br />

in this area were also observed to be significantly<br />

less than in adjacent areas without the<br />

sheds.<br />

CONCLUSIONS<br />

Two methods for reducing the thermal degradati<strong>on</strong><br />

of permafrost al<strong>on</strong>g roadways were evaluated.<br />

Snow sheds lowered the mean annual soil<br />

surface temperature to -2.3OC beneath the sheds<br />

1357<br />

as compared to 3.9OC for the exposed ground. A<br />

low-cost easily deployable system utilizing<br />

this c<strong>on</strong>cept should be developed to stabilize<br />

problem roadway secti<strong>on</strong>s built over n<strong>on</strong>-thaw<br />

stable permafrost. Both man-made and natural<br />

(vegetative cover) systems should be reviewed.<br />

ACKNOWLEDGMENTS<br />

The State of Alaska Department of Transportati<strong>on</strong><br />

and Public Facilities supported this<br />

study.<br />

REFERENCES<br />

Berg, R.I.and Esch, D.C. (1983). Effect of<br />

Color and Texture <strong>on</strong> the Surface Temperature<br />

of Asphalt C<strong>on</strong>crete Pavements. Proc. 4th<br />

Int. Perfmafrost C<strong>on</strong>f., 59-61, Fairbanks.<br />

Esch, D.C. (1973). C<strong>on</strong>trol of <strong>Permafrost</strong> Degradati<strong>on</strong><br />

Beneath a Roadway by Subgrade Insulati<strong>on</strong>.<br />

<strong>Permafrost</strong>: North American C<strong>on</strong>tributi<strong>on</strong><br />

(to the) Sec<strong>on</strong>d <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>,<br />

608-621, Yakutsk, Siberia.<br />

Esch, D.C. (1983). Evaluati<strong>on</strong> of Experimental<br />

Design Features for Roadway C<strong>on</strong>structi<strong>on</strong> over<br />

<strong>Permafrost</strong>. Proc. 4th Int. <strong>Permafrost</strong> C<strong>on</strong>f.,<br />

283-288, Fairbanks.<br />

Lunardini, V.J. (1981). Heat Transfer in Cold<br />

Climates, 731 pp. Van Nostrand Reinhold Co.,<br />

New York.<br />

Zarling, J.P., C<strong>on</strong>nor, B. and Goering, D.J.<br />

(1983). Air Duct Systems for Roadway Stabilizati<strong>on</strong><br />

over <strong>Permafrost</strong> Areas. Proc. 4th<br />

fnt, <strong>Permafrost</strong> C<strong>on</strong>f., 1463-1468, Fairbanks.

METHOD FOR CALCULATING FROST HEAVE REACTION<br />

FORCE IN SEASONAL FROST REGION<br />

Zhou, Youcai<br />

Heil<strong>on</strong>gjiang Provincial Institute of Low Temperahre C<strong>on</strong>structi<strong>on</strong> Science Harbin, China<br />

SYNOPSIS<br />

A method for calculating frost heave reacti<strong>on</strong> force acting <strong>on</strong> enlarged pile foundati<strong>on</strong><br />

is discussed. According to the measured data from Yanjiagang Observati<strong>on</strong> Stati<strong>on</strong>, it is obtained<br />

that the stress due to reacti<strong>on</strong> force caused by tangential frost heave force is distributed<br />

as a power-functi<strong>on</strong> curve within the area of restrained width of the foundati<strong>on</strong>. When the frost<br />

depth is approaching or equal to its maximum value, the restrained width of foundati<strong>on</strong> is about 1.5<br />

times the maximum frost depth. The author had derived 8 formulas for calculating frost heave reacti<strong>on</strong><br />

acting <strong>on</strong> enlarged pile foundati<strong>on</strong> in various c<strong>on</strong>diti<strong>on</strong>s.<br />

INTRODUCTION<br />

The enlarged. pile foundati<strong>on</strong>, which can bear<br />

frost heave reacti<strong>on</strong> force with its enlarged<br />

head, suppresses the tangential frost heave<br />

for.ce acting <strong>on</strong> the pile, so that it has an<br />

effect of self-anchor. It was generally recognized<br />

that the enlarged head was pressed<br />

downwards by the frost heave reacti<strong>on</strong> force.<br />

This theory was put forward at first" by B.E.<br />

dalmatov (1959). In recent years, the frost<br />

heave reacti<strong>on</strong> force is being studyed by the<br />

Third Designing Institute of the Ministry of<br />

Railway and Heil<strong>on</strong>gjiang Provincial Hydraulic<br />

Science <strong>Research</strong> Institute (Sui, 1985). But upto-date,<br />

different views and calculating methods<br />

of t'he frost heave rea-cti<strong>on</strong> force are existed.<br />

For researching the methods of calculating the<br />

frost heave reacti<strong>on</strong> force, experiments <strong>on</strong> the<br />

str<strong>on</strong>g frost-susceptible soils in Yangjiagang<br />

Observati<strong>on</strong> Stati<strong>on</strong> were c<strong>on</strong>ducted, where the<br />

terrain is flat and covered with the fine<br />

grained soil and the amount of the free frost<br />

heave is homogeneous. A test pile with the<br />

cross-secti<strong>on</strong> area of 30x30 cm was buried down<br />

to the depth of 130 cm in Oct. 1983 (Fig.la),<br />

and 3 pile foundati<strong>on</strong>s with the cross-secti<strong>on</strong><br />

area of 30x30 cm and the enlarged plates of<br />

60x60, 90x90 and 120x120 cm, respectively, were<br />

buried down to the depth of 150 cm in July 1984<br />

(Fig.lb,c and d). All of test foundati<strong>on</strong>s are<br />

made of relinforced c<strong>on</strong>crete. Not <strong>on</strong>ly the frost<br />

heave forces are measured with dynamometers but<br />

also the deformati<strong>on</strong>s of the foundati<strong>on</strong>s and the<br />

ground surface in the c<strong>on</strong>strained area of the<br />

foundati<strong>on</strong> are measured. On the basis of analysing<br />

the measured data, 8 formulas are €or<br />

calculating the frost heave reacti<strong>on</strong> force deduced.<br />

Comparing with the formula proposed by<br />

B.E.Dalmatov, these formulas are with a higher<br />

accuracy.<br />

P ) b) C )<br />

Fig.1 Schematic .Diagram of Test<br />

Model Foundati<strong>on</strong>s<br />

CALCULATION OF FROST HEAVE REACTION FORCE ON<br />

ENLARGED PILE FOUNDATION ACCORDING TO TANGEN-<br />

TIAL FROST HEAVE FORCE ON THE PILE FOUNDATION<br />

In calculating it is assumed that the frost<br />

heave amount of any circular cross-secti<strong>on</strong><br />

apart from the lateral surface of the foundati<strong>on</strong><br />

is equal in the c<strong>on</strong>strained area; the c<strong>on</strong>strained<br />

width (radius) around the foundati<strong>on</strong><br />

is equal al<strong>on</strong>g radius,and the soil, temperature<br />

and moisture c<strong>on</strong>diti<strong>on</strong> are tne same in the c<strong>on</strong>strained<br />

range of the pile foundati<strong>on</strong>.<br />

According to the measured data in Yanjiagang<br />

Observati<strong>on</strong> Stati<strong>on</strong> (Zhou, 1985) the frost heave<br />

amount of ground surface al<strong>on</strong>g the radial directi<strong>on</strong><br />

of a foundati<strong>on</strong> within the c<strong>on</strong>strained width<br />

is distributed as an increasing power functi<strong>on</strong><br />

(see curve 1 in Fig.2).<br />

which can be written as<br />

1358

where Ah = AH - AH1<br />

AH - free frost heave amount <strong>on</strong> the<br />

ground surface bey<strong>on</strong>d the c<strong>on</strong>-<br />

nH1-<br />

strained area of foundati<strong>on</strong>;<br />

frost heave amount of theground near<br />

the lateral surface of pile foundati<strong>on</strong>;<br />

L "c<strong>on</strong>strained width of foundati<strong>on</strong>,and<br />

B

The area of the enlarged plate is generally<br />

less than that of the c<strong>on</strong>strained range of foundati<strong>on</strong>,<br />

and the plate is buried bellow frost<br />

Er<strong>on</strong>t. If the frost heave stress <strong>on</strong> freezing<br />

fr<strong>on</strong>t transfers downwarde with the diffusi<strong>on</strong><br />

angle of @',the width of distributi<strong>on</strong> of €rost<br />

heave reacti<strong>on</strong> force at the depth of h from<br />

freezing fr<strong>on</strong>t can be estimated by<br />

Substitute F into the above formula, then<br />

Lh = L + htge"<br />

Substitute Lh for L and Ua for OA, then eq. (5)<br />

becomes<br />

This is the sum of, the vertical stress of the<br />

frost heave reacti<strong>on</strong> forces caused by the tangential<br />

frost heave force <strong>on</strong> the plane with<br />

the width of L and depth,of h beneath freezing<br />

fr<strong>on</strong>t.<br />

If neglecting self-weight pressure of frozen<br />

soil layer, the vertical stress of the frost<br />

heave reacti<strong>on</strong> force at the depth of h and near<br />

the lateral surface of the pile is<br />

rn<br />

1<br />

On t,he plane at the depth of h, the vertical<br />

stress caused by the self-weight pressure of<br />

frozen soil layer per unit area is<br />

Fig.4 Diagram for Calculating the Frost Heave<br />

Reacti<strong>on</strong> <strong>on</strong> a Enlarged Circular Pile Foundati<strong>on</strong><br />

where H is the thickness of frozen soil layer.<br />

When the groundwater table is lower than the en-<br />

After knowing Oa and % the frost heave reacti<strong>on</strong> larged head, the reacti<strong>on</strong> force equati<strong>on</strong> should<br />

be written as<br />

force acting <strong>on</strong> the circular enlarged pile<br />

foundati<strong>on</strong> below freezing fr<strong>on</strong>t with a depth<br />

of h and verge length of t (see Fig.4) can be<br />

PA=2mtIo,[l-1+0(2h)B]+~}+<br />

1 t at'I@ca[l- L(Lp ]+ah) (13)<br />

calculated by<br />

2+8 Lh<br />

PA = 2n(EFp + EhFh><br />

where ,$< 1.0 is a reducti<strong>on</strong> factor<br />

(Iza) gential frost heave force.<br />

of the tan-<br />

where Fh-area of the reacti<strong>on</strong> caused by the<br />

The formulas 12 and 13 show that the relati<strong>on</strong><br />

weight of frozen soil, and ,between the frost heave reacti<strong>on</strong>,force of the<br />

circular enlarged pile foundati<strong>on</strong> and the length<br />

Fh-coordinate of the center of gravity<br />

of verge board is of a parabola. When using<br />

of the area in x axis.<br />

the formulas 12 and 13 to calculate the frost<br />

heave reacti<strong>on</strong> force <strong>on</strong> the enlarged head at<br />

For a curved quadrangle, Fpand E, could be calfreezing<br />

fr<strong>on</strong>t, it is necessary to substitute<br />

culated as follows<br />

L for Lh, OA for oa, ~ T H for oh9 i..e. I<br />

Fp =I Oa[1-~L)8]dx=o,t[1- -(-) tf3 ] p 21TrtlI3 [ 1- It yTH f Tlt'{oA[ 1- -(-) 2 t R ]+yTHI (14)<br />

0 h 1+8 Lh A A Ita L 2+!3 L

where Lh=L + htge' and oa is the vertical frost<br />

heave reacti<strong>on</strong> stress close to the lateral surface<br />

of the pile, which can be calculated by<br />

Calculati<strong>on</strong> of the frost heave reacti<strong>on</strong> force<br />

<strong>on</strong> the square enlarged pile foundati<strong>on</strong><br />

The tangencial frost heave force of the square<br />

enlarge1 pile foundati<strong>on</strong> is c<strong>on</strong>sidered to be<br />

composed of the tangential frost heave forces<br />

at the straight line segments and at the c<strong>on</strong>ners<br />

of the square pile foundati<strong>on</strong>. If not c<strong>on</strong>sidering<br />

the vertical frost heave stress caused by<br />

the weight of the frozen soil layer, the tangential<br />

frost heave force <strong>on</strong> the straight line<br />

segments can be calculated by integrating<br />

formula (3) (areas of A in Fige5): while the<br />

At a depth of h below the freezing fr<strong>on</strong>t the<br />

vertical stress of reacti<strong>on</strong> force caused by the<br />

weight of frozen soil layer per unit area is:<br />

Knowing ua and yh, we can calculate. the frost<br />

heave reacti<strong>on</strong> force <strong>on</strong> the enlarged square pile<br />

foundati<strong>on</strong> at any depth below freezing fr<strong>on</strong>t.<br />

This reacti<strong>on</strong> force is made up of two parts:<br />

<strong>on</strong>e is the reacti<strong>on</strong> force for the straight line<br />

segment (areas of a in Fig.6) and another at<br />

the c<strong>on</strong>ners of the square foundati<strong>on</strong> (areas of<br />

B om Fig.6).<br />

Fig.5 Diagram for Calculating the Tangential<br />

Frost Heave Force <strong>on</strong> a Square Pile Foundati<strong>on</strong><br />

tangential frost heave force at the c<strong>on</strong>ners are<br />

formed a circle (areas of B in Fig.5). Which<br />

can be calculated with formula (4), but the<br />

i.tem of r in the equati<strong>on</strong> of (5) needs to be<br />

canceled, i.e.,<br />

T=4aJ.Lo~[1-(2)B]dx+2n~~<br />

ltfi 2(2+8)<br />

0 - ML=<br />

oA@L[= 4a -+ 2+8] nL (16) Fi$,6 Diagram for Calculating the Frost Heave<br />

Reacti<strong>on</strong> <strong>on</strong> an Enlarged Square Pile Foundati<strong>on</strong><br />

where a - length of sides of the square enlarged pile<br />

foundati<strong>on</strong>.<br />

when not c<strong>on</strong>sidering the weight of frozen soil<br />

layer, the vertical frost heave force close to<br />

the lateral surface of the pile <strong>on</strong> freezing<br />

fr<strong>on</strong>t i.s expressed as:<br />

x<br />

4a XI,<br />

BL[- - -1<br />

l+R 2+0<br />

At a depth of h below freezing fr<strong>on</strong>t the sum of<br />

the vertical stresses of the frost heave reacti<strong>on</strong><br />

force is:<br />

The former can be calculated by integrating the<br />

vertical reacti<strong>on</strong> stresses over the areas, and<br />

the latter can be c<strong>on</strong>sidered as the reacti<strong>on</strong><br />

force acting <strong>on</strong> a square plate with the aide<br />

length of 2t. For c<strong>on</strong>venience it can be c<strong>on</strong>sidered<br />

to be equivalent a circular plate with<br />

a radius of R, and <strong>on</strong> which the reacti<strong>on</strong> force<br />

caused by the tangential frost heave force can<br />

be calculated with eq.(4). Thus, the total<br />

reacti<strong>on</strong> force <strong>on</strong> the enlarged square foundati<strong>on</strong><br />

can be estimated by<br />

P = 4aJt(7,[ l-(p)<br />

0 h<br />

fi]dx + batoh t. 2nEFp f nR'oh<br />

(21a)<br />

In which, R-1.13t; F and &can be cal.cula'ced hy<br />

P<br />

1361

and<br />

2 R<br />

1- --(-)B<br />

2 4 L,<br />

TABLE I<br />

Comparis<strong>on</strong> Between the Calculated and Observed Values<br />

of Frost Heave Reacti<strong>on</strong> for Various Foundati<strong>on</strong>s<br />

Substituting the expressi<strong>on</strong>s of R, Fp and 6<br />

into eq.(Zla), we have<br />

When-the groundwater table is lower than the enlarged<br />

plate, eq.(21) becomes<br />

Verge lengrhvalues of frost heave reacti<strong>on</strong>,xlOhN Error<br />

of enlarged<br />

plate (cm) Observed Calculated (%)<br />

" 15 1.32 1.34 +l. 50<br />

3P 3.10<br />

45 5.25<br />

3.18 t2.70<br />

5.41 +3.12<br />

CONCLUSIONS<br />

If using eqs.(21) and (22) to calculate the<br />

frost heave reacti<strong>on</strong> force <strong>on</strong> freezing fr<strong>on</strong>t it<br />

is necessary to substitute L for Lh# 'JA for ua<br />

and ~ T H for oh in the two equati<strong>on</strong>, i.e.,<br />

COMPARISON BETWEEN THE MEASURED AND CALCULATED<br />

VALUES OF FROST HEAVE REACTION FORCE<br />

The frost heave reacti<strong>on</strong> forces were measured<br />

at the field test stati<strong>on</strong> in 1984-1985, when<br />

the maximum free frost heave amount is 26.78 cm<br />

and the maximum thickness of frozen layer is<br />

147 cm. The observed values of the frost heave<br />

reacti<strong>on</strong> for the three square test foundati<strong>on</strong>s<br />

with the verge length (t) of 15, 30 and 45 cm<br />

are 1.32~104, 3.10~104 and 5.25x104N, respectively.<br />

As the groundwater table at the test site is<br />

lower than the bottom of the test foundati<strong>on</strong>s,<br />

the frost heave reacti<strong>on</strong> force should be calculated<br />

with eq.(22). By using the parameters<br />

of B =0.4, Lh"187.99 cm, a=30 cm, YT=O.O188 N/cmS,<br />

oa=0.03696 MPa, u h-0.02555 MPa and @=O.Y08, 0,817<br />

and 0.725 for t=15, 30 and 45 cm, respectively,<br />

the frost heave reacti<strong>on</strong> forces <strong>on</strong> the test<br />

foundati<strong>on</strong>s were calculated with eq.(22). The<br />

calculated results, together with the observed<br />

values, are shown in Table I. It is seen from<br />

the Table I that the calculated results are in<br />

a good agreement with measured values, indicating<br />

that the formulas for calculating the frost<br />

heave reacti<strong>on</strong> presented are reliable.<br />

ti) When the frost heave reacti.<strong>on</strong> force <strong>on</strong><br />

an enlarged foundati<strong>on</strong> i s calculated <strong>on</strong><br />

the basis of tangential frost heaving<br />

force, the tangential frost heaving force<br />

s-hould nat be reduced if the groundwater<br />

table is higher than the enlarged plate,<br />

whereas it should be reduced according to<br />

the verge length of the enlarged head if<br />

the groundwater table is lower than the<br />

plate.<br />

(ii) At the Yanjiagang Field Stati<strong>on</strong> where the<br />

maximum free frost amount is about 26-28<br />

cm and the maximum frost depth is about<br />

150 cm, the tangential frost heaving<br />

force will be completely balance-d by the<br />

frost heave reacti<strong>on</strong> when the verge<br />

length is not less than 5'5% or 40% of the<br />

thickness of frozen layer as the groundwater<br />

table is higher or lower than the<br />

enlarged plate.<br />

(iii) Investigati<strong>on</strong> shows that the relati<strong>on</strong><br />

between frost heave reacti<strong>on</strong> and the<br />

verge length of englarged plate is parabolic.<br />

REFERENCES<br />

Cui Chenghan and Zhou Kaiji<strong>on</strong>g, (1983). The experimental<br />

research of the frost heave<br />

reacti<strong>on</strong> force, Proc.of Sec<strong>on</strong>d Nati<strong>on</strong>al<br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>, p.260-263,People':<br />

Publishing House of Gansu,<br />

Dalmatov, B.E., (1959), The frost heave of soil<br />

acting <strong>on</strong> c<strong>on</strong>structi<strong>on</strong>s, Baok are translated<br />

by Harbin Industrial University,<br />

C<strong>on</strong>structi<strong>on</strong>-industrial Publishing House.<br />

Panna, E., (1974). The frost heave force acting<br />

<strong>on</strong> the foundati<strong>on</strong> of structures in frost<br />

soil, Canadian Geotechnical of Journal,<br />

Vol.11, No.3.<br />

Sui Xianzhi, (1985), Calculati<strong>on</strong> of frost heave<br />

reacti<strong>on</strong> force <strong>on</strong> the enlarged pile foundati<strong>on</strong><br />

in seas<strong>on</strong>al frozen regi<strong>on</strong>, Journal of<br />

Glaciology and Geocryology, Vo1.7, Nu.4.<br />

Zhou Youcai, (1985), The calculati<strong>on</strong> of frost<br />

heave force according to frost heave deformati<strong>on</strong><br />

in the c<strong>on</strong>strained area of foundati<strong>on</strong>,<br />

Journal of Glaciology and Geocryology,<br />

Vo1.7, No.4.<br />

1362

COLD-MIX ASPHALT CURING AT LOW TEMPERATURES<br />

A.N.S. Beaty and P.M. Jarrett<br />

Royal Military College of Canada<br />

In July 1981 a series of cold-mix asphalt test secti<strong>on</strong>s were canstructed at. CFS Alert,<br />

situated at 820 N in the Canadian North West Territories. The performance of these test<br />

secti<strong>on</strong>s has been m<strong>on</strong>itored with particular reference to the rate of curing, the change .in<br />

strength with age and the l<strong>on</strong>g term effects of the asphalt pavement, both painted white and<br />

unpainted, <strong>on</strong> the permafrost rbgime. The observed data are presented and the pexformance<br />

of cold-mix asphalt in the envir<strong>on</strong>ment of the high Arctic is discussed.<br />

fNTRODUCTION<br />

Asphalt cold-mix is a mixture of unheated<br />

mineral aggregate and emulsified or cutback<br />

bitumen. Mixtures may be prepared either in a<br />

central plant or in place at the paving site<br />

using simple equipment.<br />

The advantages claimed for cold-mix asphalt<br />

include:<br />

- its adaptability to suit the requirements<br />

of a range of aggregate types in varying<br />

weather c<strong>on</strong>diti<strong>on</strong>s.<br />

- ec<strong>on</strong>omy of producti<strong>on</strong> with simple<br />

equipment and unheated aggregate.<br />

field trials and in 1981 a series of full scale<br />

trial secti<strong>on</strong>s at Alert.<br />

The purpose of the present paper is to review<br />

the performance of the full-scale trial<br />

secti<strong>on</strong>s of cold-mix asphalt over the six years<br />

since they were laid and in particular<br />

to<br />

c<strong>on</strong>sider the following:<br />

- rate of curing<br />

- strength variati<strong>on</strong> with time<br />

- effect of asphalt <strong>on</strong> ground thermal regime<br />

- general performance of the paved surfaces<br />

The most important of these advantages arise<br />

from not having to heat the aggregate. This<br />

makes the use of cold-mix asphalt particularly FIELD TEST BECTIONS<br />

attractive at remote northern job sites where<br />

provisi<strong>on</strong> of heating would be difficult and<br />

expensive. The Asphalt Institute (1977) has In July 1981 a seriea'of nine test secti<strong>on</strong>s was<br />

suggested that cold-mix asphalt operati<strong>on</strong>s c<strong>on</strong>structed <strong>on</strong> the runway apr<strong>on</strong> at Alert.<br />

should be limited to temperatures above 1O'C These c<strong>on</strong>sisted of a basecourse of crushed rock<br />

and to good weather c<strong>on</strong>diti<strong>on</strong>s. In the high aggregate, compacted at a moisture c<strong>on</strong>tent of<br />

Arctic, road and runway pavements may have to 6% to a finished thickness of 8cm. Two low<br />

be c<strong>on</strong>structed at remote sites where neither viscosity cht-back bitumens were used, these<br />

the atmospheric temperature nor that of the were an RC-30 and a primer, both produced by<br />

aggregate will normally reach 10°C. However, Gulf Oil. Using a range of binder c<strong>on</strong>tents.<br />

Wocjik, Jarrett and Beaty (1983) and Jarrett, nine mixtures were made by mixing the binder<br />

Beaty and Wocjik (1984) have shown that cold- with unheated crushed rock aggregate at about<br />

mix operati<strong>on</strong>s can be succesfully carried out 4"C, in a Cedar Rapids pug mill having a<br />

at temperatures approaching the freezing point. capacity of 700 t<strong>on</strong>nes per hour. Binder<br />

c<strong>on</strong>tents ranged from 3.5% to 8.7% for the RC-30<br />

The low temperature work referred to arose from mixtures and from 5.0% to 6.4% €or those made<br />

a requirement to study viable methods for the with the primer binder. The mixtures were laid<br />

stabilisati<strong>on</strong> of the unbound aggregate runway in four 3.8 metre wide lanes and compacted with<br />

at Alert, located at 82"30'N, 62'20'W in the a 9 t<strong>on</strong>nes vibrating roller. In order to<br />

Canadian North West Territories as shown in<br />

investigate the effects of the c<strong>on</strong>structi<strong>on</strong> <strong>on</strong><br />

figure 1. In that study the general questi<strong>on</strong> Of the permafrost regime approximately half the<br />

low temperature stabilisati<strong>on</strong> was addressed<br />

surface area was painted white and a series of<br />

using low temperature laboratory testing, pilot thermistors were installed beneath the various<br />

1363

paved secti<strong>on</strong>s and the gravel runway to a<br />

maximum depth of 1.5 metres.<br />

spreading and compacti<strong>on</strong>. Based <strong>on</strong> a maximum<br />

viscosity, for workability, of 100 000<br />

centistokes, suggested by Lefebvre (1966) I a<br />

solvent loss of 43% could be allowed. However<br />

if the ultimate air voids c<strong>on</strong>tent <strong>on</strong> Completi<strong>on</strong><br />

of curing is not to exceed 6% as recommended by<br />

Field (1966) , much less solvent loss during<br />

aerati<strong>on</strong> can be permitted, in fact <strong>on</strong>ly 12%.<br />

Griffin, Miles and Simps<strong>on</strong> (1957) c<strong>on</strong>sidered<br />

that 80% loss of solvent with mixtures made<br />

with RC-30 binder might c<strong>on</strong>stitute full curing.<br />

It may be that at the low ambient temperaturea<br />

prevailing at Alert, full curing corresp<strong>on</strong>ds to<br />

even less than 80% solvent loss, in which case<br />

more than 12% loss could be permitted during<br />

aerati<strong>on</strong> without increasing the final air voids<br />

c<strong>on</strong>tent bey<strong>on</strong>d 6%.<br />

- IO<br />

Y<br />

Y<br />

!i -20<br />

K<br />

I -30<br />

Figure 2<br />

Mean of daily maximum and<br />

minimum air temperatures at CFS Alert<br />

Figure 1<br />

GOW TEMPERATURE CURING<br />

The locati<strong>on</strong> of Alert<br />

During mixing and laying, aerati<strong>on</strong> of the<br />

mixture occurs and solvent is lost.<br />

At low<br />

temperatures this solvent loss during aerati<strong>on</strong><br />

must be limited in order to ensure that the<br />

mixture retains adequate workability €or<br />

1364<br />

The mean daily temperature at CFS Alert is<br />

-18'C. The extreme values of temperature<br />

recorded are -49.4-C'and +ZO.O'C. Figure 2<br />

shows the mean values of daily maximum and<br />

minimum temperatures for each m<strong>on</strong>th. From this<br />

it can be seen that in an average year <strong>on</strong>e<br />

might expect four frost-free weeks and<br />

a<br />

further seven weeks during which the daily<br />

maximum temperature is above the freezing<br />

point. During the brief c<strong>on</strong>structi<strong>on</strong> seas<strong>on</strong>,<br />

the mean daily temperature is about 4°C. These<br />

are the ambient c<strong>on</strong>diti<strong>on</strong>s in which curing of<br />

the asphalt takes place after laying and<br />

compacti<strong>on</strong>.<br />

The degree of curing was determined over a<br />

period of 60 days by direct weighing of<br />

laboratory Marshall specimens cured in a<br />

refrigerator at 4 ' ~ . In additi<strong>on</strong>, samples were<br />

recovered from the field in 1984 and 1987 and<br />

the degree of curing under field c<strong>on</strong>diti<strong>on</strong>s was<br />

determined by chromatography carried out by<br />

Gulf Canada.<br />

These data are combined in figure 3, which<br />

6how8, €or the basic design mixture having an<br />

initial binder c<strong>on</strong>tent of 5.1% by weight of<br />

RC-30, the degree of curing against time for<br />

the six years from 1981 to 1987.

On the assumpti<strong>on</strong> that no significant curing<br />

occurs at temperatures below O'C, there are<br />

approximately 77 day6 per year during which<br />

curing may be expected to take place. Between<br />

c<strong>on</strong>structi<strong>on</strong> in 1981 and sampling in June 1987,<br />

it is estimated that the curing period<br />

therefore corresp<strong>on</strong>ded to approximately 433<br />

days. The figure indicates that some 70% of the<br />

initial solvent had been lost during this<br />

period. Griffin et al (1957) c<strong>on</strong>sider that 80%<br />

loss of solvent might c<strong>on</strong>stitute full curing<br />

for an RC-30 cut-back. Projecti<strong>on</strong> of the<br />

trend of figure 3 would seem to support this<br />

hypothesis.<br />

Log DAYS<br />

Figure 3 Degree of curing versus curing period<br />

behaviour is essentially brittle, it was<br />

inappropriate for bituminous mixtures which<br />

behave viscoelastically. This observati<strong>on</strong> was<br />

based <strong>on</strong> tests at 45 'C for road bases in the<br />

tropics. The work of Gregg, Dehlen and Rigden<br />

(1967) showed that CBR values obtained <strong>on</strong><br />

bituminous mixtures at 20'C were very much<br />

higher than those obtained at 40°C and 60°C as<br />

the binder viscosity is much increased at the<br />

lower temperature. They c<strong>on</strong>cluded that in situ<br />

strength of bitumen-sand bases could be<br />

measured with good repeatability using the CBR<br />

test. In the case of cold-mix asphalt <strong>on</strong>e<br />

might expect more variability between<br />

individual test results due to the presence of<br />

larger aggregate particles in the mixture.<br />

It should be noted that the strain rate in the<br />

CBR test is <strong>on</strong>e-fortieth of that in the<br />

Marshall test and therefore the effective<br />

stiffness of the bitumen in the CBR test will<br />

be much lower than that in the Marshall test.<br />

As the work at Alert was to be carried out' at<br />

4'C a laboratory study was made to determine<br />

whether CBR values correlated with Marshall<br />

stabilities measured at 4 ' ~ . For stabilities<br />

in the range 4000 to 6500 Newt<strong>on</strong>s, the<br />

relati<strong>on</strong>ship:<br />

Harmhall Btability at 4.C = 36.5 CBR + 1925<br />

where stability is in Newt<strong>on</strong>s and CBR is a<br />

percentage was found to hold at 4 'c with a<br />

correlati<strong>on</strong> coefficient of 0.94.<br />

The degre'e of curing was also estimated for<br />

samples recovered in 1984 and 1987, from test<br />

strips c<strong>on</strong>structed with a higher (8.7%)<br />

proporti<strong>on</strong> of RC-30 cut-back binder. In this<br />

case the degrees of curing were 32% and 49%<br />

respectively, after three and six years. A<br />

sample recovered in 1984 from a test strip<br />

c<strong>on</strong>structed with material having 3.5% of RC-30<br />

cut-back as binder was estimated to be more<br />

than 90% cured. Thus it can be seen that the<br />

initial cut-back binder c<strong>on</strong>tent significantly<br />

affects the curing rate.<br />

STRENGTH DEVELOPMENT<br />

S;grrd.ati<strong>on</strong> batween calitornia b e ~ n u r &ti0<br />

u s h a l l stability<br />

Normally the development of the strength of<br />

asphalt during curlng is determined by<br />

laboratory testing of samples recovered by<br />

coring. In the case of Alert, due to the<br />

remoteness of the site and the initial weakness<br />

of some of the cut-back mixtures this was not<br />

possible so it was decided to try to use the in<br />

situ CBR test as an indicator of strength.<br />

Kezdi (1979) has reported that Boromissza and<br />

Gaspat had shown . a correlati<strong>on</strong> between<br />

laboratory CBR values and Marshall stabilities,<br />

although the scatter was said to be excessive.<br />

Hitch and Russell (1976), however, c<strong>on</strong>cluded<br />

that although the CBR test might be appropriate<br />

for cement and some stabilised materials whose<br />

1365<br />

ritu CBR<br />

After c<strong>on</strong>structi<strong>on</strong> and compacti<strong>on</strong> of the test<br />

strips, in situ CBR teste were carried out over<br />

a period of 60 days and subsequently after <strong>on</strong>e,<br />

three and six years in order to observe the<br />

relati<strong>on</strong>ship between strength and time.<br />

Although there is c<strong>on</strong>siderable scatter in the<br />

results the general trend of increasing CBR<br />

with time can be clearly seen. Figure 4 shows<br />

CBR against curing time <strong>on</strong> a log-log basis for<br />

3.5, 5.1 and 8.7% initial binder c<strong>on</strong>tents. The<br />

time plotted is not total elapsed time but<br />

estimated Curing time taken as 77 days per<br />

year. This is the, average number of days <strong>on</strong><br />

which the minimum temperature at Alert exceeds<br />

O'C.<br />

It is believed that the technique of using in<br />

situ CBR tests to m<strong>on</strong>itor the strength gain of<br />

asphalt cold-mix pavements could be further<br />

refined by the development of a family of<br />

temperature - CBR correlati<strong>on</strong> cu.rves. This<br />

would permit measured CBR values to be adjusted<br />

to a standard reference temperature. In the<br />

case of the work reported, the CBR-Marshall<br />

etability correlati<strong>on</strong> was determined <strong>on</strong>ly at<br />

4'C.<br />

MNQ TERN EFFECTS ON THE GROUND THERMAL REQIME<br />

One critical aspect of pavement c<strong>on</strong>structi<strong>on</strong> in<br />

permafrost areas is the effect of c<strong>on</strong>structi<strong>on</strong>

<strong>on</strong> the ground thermal rdgime. This is of<br />

particular c<strong>on</strong>cern in the case of asphalt<br />

pavements due to their capacity for absorbing<br />

solar radiati<strong>on</strong>. The deleterious effects <strong>on</strong><br />

permafrost stability of the absorpti<strong>on</strong> of polar<br />

radiati<strong>on</strong> have been reported by Herri<strong>on</strong> and<br />

Lobacz (1975) by Fulwider and Aitken (1962) and<br />

by others. One approach to minimiaing such<br />

heat absorpti<strong>on</strong> has been to paint the asphalt<br />

surface white in order to reflect rather than<br />

absorb heat. This is the case, for example, at<br />

the US Air Force Base at Thule (Berg and Quinn<br />

, (1977).<br />

r<br />

40 -<br />

a0 -<br />

-,<br />

‘ O o 0 b<br />

‘I<br />

Figure 6<br />

Temperature - depth profiles<br />

beneath unpaved runway in 1981<br />

QENERAL PERFORMANCE OF STABILIBED BICTXONE<br />

Figure 4<br />

Log DAYS<br />

CBR versus curing time<br />

In order to observe the l<strong>on</strong>g term effects at<br />

Alert, thermocouples were installed beneath the<br />

trial secti<strong>on</strong>s and in additi<strong>on</strong> parts of the<br />

surface were painted white.<br />

Figure 5 shows the profile of temperature with<br />

depth below the surface of the unpaved gravel<br />

runway at Alert, €or four different dates<br />

during the Summer of 1981. Figure 6 shows<br />

temperature-depth profiles for unpaved, paved<br />

years and painted, from 1981 paved to 1904. surfaces It can over be the seen three<br />

that<br />

the depth of thaw penetrati<strong>on</strong> beneath the<br />

painted, paved surface was less than that under<br />

the gravel runway by about 10%. Furthermore,<br />

the depth of thaw beneath the painted surface<br />

remained remarkably c<strong>on</strong>stant over three years.<br />

On the other hand, the depth of thaw<br />

penetrati<strong>on</strong> beneath the unpainted, paved<br />

surface was generally greater than that under<br />

the gravel runway.<br />

K)<br />

1366<br />

The trial secti<strong>on</strong>s have been in place for six<br />

years, during which time they have been<br />

subjected to a limited amount o’f ,traffic. This<br />

has included use as a helipad, as a parking<br />

apr<strong>on</strong> for Hercules, transport aircraft and<br />

ground traffic associated with aircraft<br />

arrivals and departures. No systematic<br />

maintenance has been carried out. From visual<br />

inspecti<strong>on</strong> it appears that the secti<strong>on</strong>s at the<br />

design binder c<strong>on</strong>tent of 5 to 5.SI, selectd <strong>on</strong><br />

the basis of a modified Marshall method,<br />

Wojcik, Jarrett and Beaty (1983), have<br />

performed well and c<strong>on</strong>tinue to do so. They<br />

appear to have sufficient strength to support<br />

the traffic and are not visibly deteriorating.<br />

The passage of a tracked vehicle over the<br />

strips shortly after their c<strong>on</strong>structi<strong>on</strong> caused<br />

serious suface damage, but this would normally<br />

be avoidable. The lack of flexibility and<br />

cohesi<strong>on</strong> of the leaner mixtures is beginning to<br />

show in the form of surface crazing. The rich<br />

mixtures c<strong>on</strong>taining more than eight per cent of<br />

RC-30 binder, even after six years are very<br />

soft and <strong>on</strong>ly half cured. They cannot support<br />

traffic in the short summer without rutting.<br />

The field performance of the test secti<strong>on</strong>s has<br />

shown that the binder c<strong>on</strong>tent selected ‘<strong>on</strong> the<br />

basis of the modified Marshall method has<br />

produced a pavement which has performed<br />

satisfactorily and has justified the use of the<br />

method.

has dem<strong>on</strong>strated the validity of the design<br />

approach.<br />

TEMPERATURE PC)<br />

Figure 6 Temperature - depth profiles beneath<br />

unpaved, paved and painted paved Burfaces<br />

COMCLUSIOUB<br />

1. Observati<strong>on</strong>s of the behaviour over time of<br />

cold-mix asphalt in the extreme ambient<br />

c<strong>on</strong>diti<strong>on</strong>s of 82' N have been presented.<br />

2. Under these c<strong>on</strong>diti<strong>on</strong>s the rate of curing of<br />

the mixtures is much less than that observed at<br />

higher ambient temperatures.<br />

3. For a binder c<strong>on</strong>tent in the range 5 - 5.5%<br />

full curing and associated strength gain has<br />

been observed to require from 6 to 10 years.<br />

4. Curing is more rapid for lower binder<br />

c<strong>on</strong>tents and vice versa.<br />

5. Although it is desirable to m<strong>on</strong>itor strength<br />

gain <strong>on</strong> samples recovered by coring, at low<br />

temperatures the in situ CBR test may also<br />

prove useful.<br />

6. Observati<strong>on</strong> of temperatures beneath paved<br />

surfacing has c<strong>on</strong>firmed that if the asphalt<br />

surface is painted white, thaw penetrati<strong>on</strong> is<br />

reduced. C<strong>on</strong>versely thaw penetrati<strong>on</strong> beneath<br />

the black asphalt surface was found to be<br />

greater than that under the untreated gravel<br />

runway. However, in the extreme climate of<br />

Alert the black surface does not appear to be<br />

inducing significant degradati<strong>on</strong> of the<br />

permafrost.<br />

7. The field performance of the trial secti<strong>on</strong>s<br />

made with the 5 to 5.5% optimum binder c<strong>on</strong>tent<br />

as determined by the modified Marshall method<br />

1367<br />

Asphalt Institute (1977). "Asphalt Cold-Mix<br />

Manualtt, MS-14, Asphalt Institute, College<br />

Park, Maryland.<br />

Berg, R.L. and Quinn, W.F. (1977). "Use of a<br />

light coloured surface to reduce seas<strong>on</strong>al<br />

thaw penetrati<strong>on</strong> beneath embankments <strong>on</strong><br />

<strong>Permafrost</strong>ll. Proc. 2nd. Int. Symp. <strong>on</strong><br />

Cold Regi<strong>on</strong>s Engineering, Fairbanks,<br />

Alaska.<br />

Field, F. (1966). "Mix design for bituminous<br />

pavements: method and interpretati<strong>on</strong>t1,<br />

Proceedings, 11th annual c<strong>on</strong>ference,<br />

Canadian Technical Asphalt Associati<strong>on</strong>,<br />

V.XI, pp. 87-106.<br />

Fulwidar, C.W. and Aitken, G.W. (1962). "Effect<br />

of surface colour <strong>on</strong> thaw penetrati<strong>on</strong><br />

beneath an asphalt surface in the arctic."<br />

Proc. 1st Int. C<strong>on</strong>f. <strong>on</strong> the . Structural<br />

Design of Asphalt Pavements, Ann Arbor.<br />

Gregg, J.S., Dehlen, G.L. and Rigden, P.J..<br />

(1967). "On the properties, behaviour and<br />

design of stabilised sand bases.I@ Proc.<br />

2nd. Int. C<strong>on</strong>f. <strong>on</strong> the Structural Design<br />

of Asphalt Pavements, Ann Arbor.<br />

Griffin, R.L., Miles, T.K. and Simps<strong>on</strong>, W.C.<br />

(1957). A curing rate test for cut-back<br />

asphalts using a sliding plate<br />

viscometer" , Proceedings, Associati<strong>on</strong> of<br />

Asphalt Paving Technologists, v. 26, pp.<br />

437-467, Atlanta, Georgia.<br />

Henni<strong>on</strong>, F.B., and LobaczI E.E. (1973). ltCorps<br />

of Engineers technalogy related to design<br />

of pavements in areas of permafrost.I'<br />

Proc. 2nd. Int. C<strong>on</strong>f . <strong>on</strong> <strong>Permafrost</strong>,<br />

Yakustk.<br />

Jarrett, P.M., Beaty, A.N.S. and Wocjik, A.S.E.<br />

(1984) . IfCold-mix asphalt technology at<br />

temperatures below 10"C1l, Proceedings Of<br />

the AsSOCiatiOn of Asphalt Paving<br />

Technologists, Scottsdale, Ariz<strong>on</strong>a.<br />

Kezdi, A. (1979). "Stabilised earth roadsQ1,<br />

Elsevier, Amsterdam.<br />

Lefebvre, J. A. (1966). '*A suggested Marshall<br />

method of design €or cut-back asphaltaggregate<br />

paving mixtures" , Proceedings I<br />

11th Annual <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, Canadian Technical<br />

~sphalt Associati<strong>on</strong>, v. XI, pp. 135-181.<br />

Wojcik, A.S.E., Jarrett, P.M. and Beaty, A.N.S.<br />

(1983). IICold-mix asphalt stabilisati<strong>on</strong> in<br />

cold regi<strong>on</strong>s" , Proceedings IVth<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>,<br />

Fairbanks, Alaska.

PROGNOSIS OF SOIL TEMPERATURE AT THE AREA UNDER CONSTRUCTION<br />

A.L. Chekhovskyi<br />

<strong>Research</strong> Institute of Engineering Site Investigati<strong>on</strong>s, Moscow, USSR<br />

SYNOPSIS Methods and nomograme we proposed to estimate a two-three-dimensi<strong>on</strong>al stable<br />

temperature field when heat sources are freely arranged. To predict or to eatimate a nultivariate<br />

unstable temperature field with or- without a change of soil phase i s supposed to reduce<br />

to solvati<strong>on</strong> of a <strong>on</strong>e-dimensi<strong>on</strong>al problem, For this purpose a piecewise smooth functi<strong>on</strong> of<br />

boundary c<strong>on</strong>diti<strong>on</strong>s is changed to a mean equivalent prescribed by the exp<strong>on</strong>ential law. The proposed<br />

approximate analytical method permita to eatimate multivariate tcrnperaturs field for<br />

real c<strong>on</strong>diti<strong>on</strong>s of town development.<br />

From the very beginning of c<strong>on</strong>structi<strong>on</strong> worka<br />

engineering-geocryological c<strong>on</strong>ditians of the<br />

@rea under c<strong>on</strong>structi<strong>on</strong> are exposed to great<br />

chengee. ThiEc prooass c<strong>on</strong>tinuee when the c<strong>on</strong>structi<strong>on</strong><br />

works are completed,<br />

From B thsrmophysical point of view an area<br />

under c<strong>on</strong>structi<strong>on</strong> presents a combinati<strong>on</strong> of<br />

a number of eream with different heat xeleaew<br />

and heat absorptL<strong>on</strong>. A temperature field of<br />

every hest release or heat absorpti<strong>on</strong> area is<br />

formed under complex affects of natural and<br />

technogenic factora, If c<strong>on</strong>eider a city area<br />

as a whole ita influence <strong>on</strong> a heat field of<br />

permafroat rrtrafa is estimated ae hundreds<br />

metres ana beneath individual districts and<br />

quarters of a city a depth of heat impulees<br />

penetrati<strong>on</strong> reaches doesns metres; under some<br />

buildings it exceeds 10-15 m a local temperature<br />

Pield of every specific point should be<br />

entimated with account of a temperature field<br />

of the area under o<strong>on</strong>atruoti<strong>on</strong> a aa whole.<br />

To eolve different engineering-geological or<br />

building problems of the area under c<strong>on</strong>structi<strong>on</strong><br />

it is neceesary to estimate or to predict<br />

as a stable so unetable temperature field. A<br />

prognosis of R etable temperature field permits<br />

to determine a maximum depth OP perennial<br />

thawing of soile under buildings and structures;<br />

to solve problems of underfloading the<br />

territory under c<strong>on</strong>mtructi<strong>on</strong>; to estimate a<br />

bearing capacity of piles, An unstable temperature<br />

field permits to prognoze development<br />

of oryogenic processes; to eelect an engineering<br />

technology for buildings and structures,<br />

industrial sanitary communicati<strong>on</strong>s, railwaya<br />

and motor roads.<br />

Two-dimensi<strong>on</strong>al temperature field of a city<br />

development can be presented a8 8. ~ w n of in-<br />

tegrals determined a temperature beneath a<br />

centre of the infinite band, i.8. XnaO<br />

... +<br />

A surface temperature is prescribed as a piecewtse<br />

smooth functl<strong>on</strong> T(x> for every interval:<br />

- - + n,, ml + m2, mnel j %,rnn+ - ;<br />

Yodepth<br />

of a temperature c<strong>on</strong>trol point;<br />

T(Yo) - ground temperature at point Yo.<br />

It follows from the foregoing equati<strong>on</strong> that<br />

ell the eourcea of: heat release end heat ab-<br />

Etorpti<strong>on</strong> should be taken into account., but it<br />

presents some difficulties due to their great<br />

number. A computer-aided design shows that<br />

the remote heat sources and hest release can<br />

be neglected when measuring a tempereture with<br />

an accuracy of 0,l OC and a building deneity<br />

variee from 0.2 to 0.8. There i~l a 11 'near<br />

depan ence between a dimensi<strong>on</strong> of a deaign<br />

area (L) and a depth of a point dip (Yo) where<br />

a temperature is meamwed* Pumti<strong>on</strong> graphics<br />

L Q f(Yo) lor tenperature differences in the<br />

intervals of the piecewi8e smooth functi<strong>on</strong> are<br />

presented in Pig. 1. For an effective dertign<br />

of a two-dimensiocal stable tern erature field<br />

aome nomograms are recommended aPig.2). A procedure<br />

of a temperature measuring is a8 follow~.<br />

The Ti<br />

R<br />

values (r'nrr in number)are estimated<br />

depending <strong>on</strong> a depth of point Yo dip;<br />

a distsnce from an origin of coordinates to<br />

mi and a difference in temperatures ( A T) at<br />

mi point. Temperature at point Yo can be deduced<br />

from the formula:<br />

where g - stands for a value of geothermal<br />

gradient, OC/m; for the values To and Tn see<br />

formula (I). Design of a three-dimensi<strong>on</strong>al<br />

1368

In this case practical use of this method is<br />

rather difficult due to the fact that in order<br />

to determine t. it is necessary to eatlmate<br />

J<br />

an area occupied by every aource in every<br />

circular z<strong>on</strong>e. The method can be rather simplified<br />

if estimate circle stretchee crossing<br />

a heat BouFce instead of estimating the arm,<br />

Circles crom a middle of every circular z<strong>on</strong>e,<br />

Temperature t can be deduced from the followj<br />

ing equati<strong>on</strong>:<br />

.1 Dimensi<strong>on</strong> of a design area (Z) depending<br />

<strong>on</strong> a difference in temperature<br />

range8 of a piecewise smooth functi<strong>on</strong><br />

( A T1 and a depth of Y, point I<br />

Tn,"C<br />

3,4 t<br />

where ti - mean temperature of a heat source;<br />

lij- length of a circle stretch CTOSSing<br />

a heat sourcer<br />

A number of calcuhti<strong>on</strong>a based <strong>on</strong> two methods<br />

of the t. estimati<strong>on</strong> fox typical city build-<br />

J<br />

inga showed a difference in temperature t<br />

not mom than 0-10% even under worm c<strong>on</strong>di- .<br />

fi<strong>on</strong>e (small-scale 9nozaic" buildings). Due<br />

to simplified assumpti<strong>on</strong>s we succeeded in c<strong>on</strong>structi<strong>on</strong><br />

of nomograms provided an efficient<br />

design of a three-dimensi<strong>on</strong>al stable temperature<br />

field with an o ti<strong>on</strong>al arrangement of<br />

heat BOUXCBB (Fig, 3yr By these nomograms<br />

Fig.2<br />

Chart for estimati<strong>on</strong> of a two-dimensi<strong>on</strong>al<br />

Btati<strong>on</strong>aFy temperature pattern<br />

( A T 2OC)<br />

stable temperature field with an opti<strong>on</strong>al<br />

arrangement of heat sourcea and heat release<br />

is baaed <strong>on</strong> analytical methods proposed by<br />

Lachenbruch (19571, Balobaev, Shastkevich<br />

(19741, Sheikin (1976). Sheikin's method is<br />

baaed <strong>on</strong> solvsti<strong>on</strong> for a atable temperature<br />

(t,) at a point of homogeneoua ground semiinferval<br />

at depth Z under a centre of a<br />

circle-like souxoe with R radius under 8. temperature<br />

within a circle countour, the tempereture<br />

at thie point exceeds the temperature<br />

within the rest surface by TW. Then we have<br />

an equati<strong>on</strong>: 1<br />

tZ T<br />

Proceed<br />

(1- )*<br />

b v<br />

<strong>on</strong> the assumpti<strong>on</strong> that a temperature affect <strong>on</strong><br />

the point at an adequate depth of aome souxces<br />

arranged at any 8rea but a narrow enough c<strong>on</strong>centric<br />

circular z<strong>on</strong>e can be changed ta an<br />

affect of an equivalent temperature (t.). The<br />

3<br />

t. temperature is a X8Bdt of arithmetic aver-<br />

J<br />

aging temperature of all the source3 with account<br />

of their area occupied in the circular<br />

z<strong>on</strong>e under c<strong>on</strong>siderati<strong>on</strong>.<br />

Fig.3<br />

Chart for estimati<strong>on</strong> of a three-dirnenai<strong>on</strong>al<br />

stati<strong>on</strong>ary temperature pattern.<br />

a temperature at the deaixed point can be deduced<br />

from the following formula:<br />

1369

every circle and t(k) is found by equati<strong>on</strong> approximating zero when spreading at the boundn-1<br />

ary of the deaign area a law let's of aaau<br />

111. Value (1 - z kj) tn is taken from the decrease to be exp<strong>on</strong>ential. Mean temperature<br />

j=1 at the of surface the area under examin<br />

nomogram with account of a definite tempera- (Tmean) is prescribed in the following way:<br />

ture t, (temperature at point Z projected<br />

'I<br />

to the plane). Number Of circles ia 10 for an<br />

accurate design 5 and - for an approximate ATeX$-IIIi/L/2 = 9) (VI<br />

design,<br />

Methods of predicti<strong>on</strong> an unstable temperature where: To-temperature of the surface at point<br />

field of areas under c<strong>on</strong>structi<strong>on</strong> are subdivided<br />

to two groups. The first group envix<br />

ow;<br />

sages design problema of unstable temperature ATj-difference in temperatures of the<br />

field without soil phaBe changes. The sec<strong>on</strong>d subsequent and previous interval<br />

group io known as Stephanls problem including at the point breaks in a piecewise<br />

design methods of an unstable temperature smooth functi<strong>on</strong>, OC;<br />

field with soil phase changes. In case of complicated<br />

distributi<strong>on</strong> OP surfsce temperature<br />

mi-diatance from point x L: o to the<br />

the design is reduced to solvati<strong>on</strong> of e two- i - interval ;<br />

three-dimensi<strong>on</strong>al problem of heat c<strong>on</strong>ductivity.<br />

L - dimensi<strong>on</strong> of a deeian - area. m .<br />

As for a two-dimensi<strong>on</strong>al design area a band<br />

can be distinguished within the built-up terri- It followa from the proposed formula, if at<br />

tory; a width of this band is too mall ae comcentre<br />

of "the design area within an interval<br />

pare to its length. Within thirs band the tem- AL B temperature is Ti and outside of this<br />

perature distributi<strong>on</strong> is a functi<strong>on</strong> of the X<br />

coordinate. Outmide of the built-up area a tern- interval a temperature ia c<strong>on</strong>stant T2 then<br />

pereture is c<strong>on</strong>stant and does not depend <strong>on</strong><br />

coordinates. The problem is solved by uaual<br />

methods under simple boundary c<strong>on</strong>diti<strong>on</strong>s without<br />

soil phase changesc A two-dimensi<strong>on</strong>al pro- -TI. A temperature at the desired point Y<br />

blem of heat c<strong>on</strong>ductivity with free a preaori- can be deduced from the well known formula:<br />

bed functi<strong>on</strong> at the upper border of the half-<br />

-plane waa solved by S,S,Kovner, A problem of<br />

a half-plate and a two-dimanei<strong>on</strong>a1 plate was<br />

solved by A.V.Lykov (1967). But the solvati<strong>on</strong>s<br />

of the Poregoing suthore are so awkward that<br />

cannot be used in pracfieal design. An approximate<br />

solvati<strong>on</strong> of a two-dimensi<strong>on</strong>al. unetable<br />

problem of heat c<strong>on</strong>ductivity with a prescribed<br />

piecewlae amooth temperature at the upper regi<strong>on</strong><br />

under examinati<strong>on</strong> waa effected, for the<br />

first time by L.N,Khrustalev (1971 by reducing<br />

a two-dimensi<strong>on</strong>al problem to <strong>on</strong>e-dimensi<strong>on</strong>al,<br />

The authors of the present paper propose<br />

a method to eolve a two-dimensi<strong>on</strong>al Like<br />

aa three-dimensi<strong>on</strong>el problems of unetable heat<br />

c<strong>on</strong>ductivity <strong>on</strong> the basis of eolving <strong>on</strong>e-dimenat<strong>on</strong>al<br />

problems with aesumpti<strong>on</strong>s differ<br />

from those accepted by L.N.Khrustalev.<br />

If a temperature is determined by Y coordinate<br />

for point X a o the area under examinati<strong>on</strong><br />

can be rather accurately aesumed as a terminal.<br />

Dimensi<strong>on</strong>s of the area are determined by a<br />

range variati<strong>on</strong> of a temperature within thb<br />

limite of the area under examinati<strong>on</strong> and a<br />

depth of the desired point. As a result, for<br />

the pofnta depending <strong>on</strong> coordinate y, when<br />

x = o the <strong>on</strong>e-dimensi<strong>on</strong>al problem of unstable<br />

heat c<strong>on</strong>ductivity can be eolved with an acauracy<br />

sufficient for practice under c<strong>on</strong>diti<strong>on</strong><br />

when a temperature at the boundary of the, mea<br />

under examinati<strong>on</strong> is assumed c<strong>on</strong>stent and de-<br />

where a - coefficient of temperature c<strong>on</strong>ductivlty,<br />

m2/h;<br />

5- time period, h.<br />

Fig.4 represents a design, area for determinati<strong>on</strong><br />

of Tmean when solving a three-dimensi<strong>on</strong>al<br />

problem of unetable heat c<strong>on</strong>ductivity.<br />

Fig.4<br />

Y<br />

t<br />

L/*<br />

1<br />

An example of a design echeme for<br />

estimati<strong>on</strong> of Tmean when solving<br />

a two-dimensi<strong>on</strong>al problem of vari<br />

able thermal c<strong>on</strong>ductivity.<br />

fined ae Tmean. A three-dimenai<strong>on</strong>al problem be Bolved can by<br />

So, the difficulty is a transiti<strong>on</strong> from a<br />

reducing to <strong>on</strong>e-dimensi<strong>on</strong>al. For this purpose<br />

piecewise smooth functi<strong>on</strong> of temperature at the ~ ~ e i ~ u ~ ~ $ ~ 6 ~ ~ a ~ ~ ~ e t ~ ~ ~ ~<br />

boundary of the area undey examinati<strong>on</strong> a to<br />

c<strong>on</strong>stant temperature Tmean. With account of a Value Tmean<br />

I11 depends <strong>on</strong> an area of heat abdegree<br />

of thermal effect of a heat source<br />

Etorpti<strong>on</strong> and heat release stretches; their tem-<br />

1370

persture <strong>on</strong> the surface and some other factora. T2(Y,T )-To i,-erfc(Y/2<br />

Tmean I11 is determined in the following way<br />

(X)<br />

(Pig, 5). All the heat sources and heat rele- . , /erfc(p /2 G2)1<br />

ase sources of the design area 'are projected<br />

Far practisal design is deduced wFth an<br />

insignificant error from Stephan's simplified<br />

formula :<br />

ir<br />

iv<br />

Fig.5<br />

An example of a design mheme for<br />

estimati<strong>on</strong> of Tmean 111 when solving<br />

B three-dimensi<strong>on</strong>al problem of variable<br />

themel c<strong>on</strong>ductivity,<br />

Projecti<strong>on</strong> of the point where a temperature<br />

is determined.<br />

to line 1-1. Tmean is deduced from formula V<br />

for Lines 11-11, TIL-I11 and IV-"IV. Then deduce<br />

T, 1IL.frorn the following equati<strong>on</strong>:<br />

TmeanT'l = 'mean +- f: AT<br />

J = J 2 X ITtmean/ P w X (XI 1<br />

where Y - depth of the desired point of the<br />

temperature design, OC;<br />

Tl- temperature within a thawing z<strong>on</strong>e,<br />

oc ;<br />

T2- temperature within a permafrost<br />

z<strong>on</strong>e, 'IC;<br />

8,- coefficient of temperature c<strong>on</strong>ductivity<br />

of frozen ground, m2/h;<br />

To- initial temperature of top ground,<br />

OC.<br />

To verify validity of the 'askumpti<strong>on</strong>s all, the<br />

deai n results were compared <strong>on</strong> the basis of<br />

the !omgoing methode and with the aid of computers.<br />

When so'lvtng two-dimenei<strong>on</strong>al problems<br />

the discordance does not exceed 10% and 15% -<br />

for the three-dimensi<strong>on</strong>al probleme. The methodrs<br />

propoded to solve unstable problems oP<br />

heat c<strong>on</strong>ductivity have no accurate thsoretiaal<br />

grounda of cour~e. It la evident that<br />

there exist temperature, ground and other Iimitati<strong>on</strong><br />

of the methods deecribed, But their<br />

m e for practical deHign and solvati<strong>on</strong> of predicti<strong>on</strong><br />

problems ie quite evident due to their<br />

simplicity and effiolency,<br />

2 i=l mean. i REFERENCES<br />

Balobaev V. To, Shaatkevich Ju. G. ( 1974 ).Ra-<br />

exp(-mi/LI2 - ml 1<br />

echef k<strong>on</strong>figurateii talikovykh z<strong>on</strong> i etatsi<strong>on</strong>arnogo<br />

temparaturnogo polya gornykh<br />

A tempereture at the desired point Y can be porod pod vodoemami profzvol noj fom,<br />

found by the following equati<strong>on</strong>:<br />

Ozera kriolitoz<strong>on</strong>y Sibiri. 146-72'7.<br />

Novoekbirsk. Nauke.<br />

Lykov A.V., (1967). Teorija feploprovodnoati.<br />

c;c.l-600. Moakva. Vyashaja &kolar<br />

Khrustalev L.N. (1971). Temppsraturnyi rezhirn<br />

vachnbrneralykh gruntov na zastroennoj<br />

Stephan's two-and-three-dimensi<strong>on</strong>al problem<br />

texritorii. c.a.1-168. Moakva: Nauka.<br />

(n<strong>on</strong>-atati<strong>on</strong>ary problem of heat c<strong>on</strong>ductivity Sheikin I.V. (1976). Metod opredelenija atawith<br />

soil phaae changes) i8 ala0 solved by<br />

tai<strong>on</strong>arnogo polja tempsratur v gmnforeducing<br />

to the <strong>on</strong>e-dimensi<strong>on</strong>al problem, Mean<br />

vom massive pri sloehnoj k<strong>on</strong>figurateii<br />

temperature of the aurface IT' is asti-<br />

ietochnikov tepla na ego poverkhnosti.<br />

mean<br />

Inzhenerno-geologicheskie i geokriologimated<br />

by formulae V, VII. Then a positive tern-<br />

cheakie iaaledovanija v Zapadnoj Sibiri.<br />

perature within the interval of positive va-<br />

vyp. 49, 145-155. Moakva: Strojizdat,<br />

lues of the piecewiae arnooth functi<strong>on</strong> is changed<br />

to zero temperature since a major part of Lechsnbruch, A.H. (1957). Threi dimenel<strong>on</strong>el<br />

heat is c<strong>on</strong>sumed by thawing of frozen strata<br />

heat c<strong>on</strong>ducti<strong>on</strong> in permefroet beneath<br />

and the lsaat quantity of heat is o<strong>on</strong>sumed by<br />

heated buildlngs Geol. Surv. Bull.,<br />

warm-up of the n<strong>on</strong>-thawing permafroet, When<br />

7052 13, 50-69.<br />

a mean tempereture <strong>on</strong> the surface of the design<br />

area is determined, a temperature at the<br />

desired point can be found by the well-known<br />

formulae:<br />

1371'

PRESSURE IN RELATION TO FREEZING OF WATER-CONTAINING<br />

MASSES IN A CONFINED SPACE<br />

M.M. Dubina<br />

<strong>Permafrost</strong> Institute, Siberian Branch of the U.S.S.R. Academy of Sciences, Yakutsk, U.S.S.R.<br />

SYNOPSIS Water-to-ice phase traneiti<strong>on</strong> is accompanied by an abruptchange in density,<br />

which causes the volume of water-c<strong>on</strong>taining masses to increase as they are freezing. Such a process<br />

occurring in a c<strong>on</strong>fined space entails a pressure increase in the unfrozen phase aa well a19<br />

loading of the frozen phase and material that reatricts a free deformati<strong>on</strong> of the water-c<strong>on</strong>taining<br />

maas. The level of the stregsea-defosmed state during course the of freezing is able to reach a<br />

value 8UffiCienf for inducing failure of the material locking the mass. Obtaining quantitative<br />

estimates of the stressed-deformed state for auoh kind procemea of i! mandatory for purposes of<br />

tackling problems of maintaining safe servicing of engineering structures and describing the ice<br />

foxmati<strong>on</strong> under natural c<strong>on</strong>diti<strong>on</strong>lir (Pekhoviah, 1983;,hbina and Krasovitaky, 1983; Wood and Goodman,<br />

1975). Previoualy documented casea of a manifestati<strong>on</strong> of ice formati<strong>on</strong> in c<strong>on</strong>fined cavities<br />

determine the upper bound <strong>on</strong> the magnitude of pressures of about two hundrede NIP&, viz. under<br />

c<strong>on</strong>diti<strong>on</strong>e of ice phaae modificati<strong>on</strong>f(Pekhovich, 1983). Under real c<strong>on</strong>diti<strong>on</strong>s %he pressures indicated<br />

axe limited by the manifestati<strong>on</strong> of a variety of thermal, physico-chemical and mechanical<br />

parameeers of ice formati<strong>on</strong>. This paper c<strong>on</strong>eiders eome semlta derived from mathematical aimulati<strong>on</strong><br />

of the development of prererauree of ice formati<strong>on</strong> which yield computati<strong>on</strong>al relati<strong>on</strong>ships<br />

uaeful for making quantitative estlmatea.<br />

FOIiMULATION OF THE PROBLEM<br />

The following c<strong>on</strong>diti<strong>on</strong>s may be categorized a8<br />

<strong>on</strong>es forming ice formeti<strong>on</strong> pxemures. Pixat,<br />

it is the pxeaenae of 8 c<strong>on</strong>fined space that irs<br />

filled with a water-c<strong>on</strong>tainink mass increasing<br />

in ita volume a8 it freepeB. The aecoud neceesay<br />

c<strong>on</strong>diti<strong>on</strong> impliea aatiefying thermodynamical<br />

c<strong>on</strong>diti<strong>on</strong>s for ice formati<strong>on</strong>, inoluding the<br />

poaeible cooling of the water-c<strong>on</strong>taining maw<br />

and the dependence of the phaee-transiti<strong>on</strong> temperature<br />

<strong>on</strong> the preeaure and density of admixtures,<br />

in partioulaf dissolved salta. We ah0<br />

take into c<strong>on</strong>siderati<strong>on</strong> that, in cases of prrctical<br />

applicati<strong>on</strong>s, the model of the process<br />

may be limited to the scope of axial and spherical<br />

symmetry when the freezing prooeao is<br />

proceeding in the directi<strong>on</strong> from the cooled<br />

outer walls of the apace to its center.<br />

In such a way, we c<strong>on</strong>aider the following specifying<br />

system of equati<strong>on</strong>s:<br />

1372

where & , 7;: a,. , and are density, tem- hydrostatic. Such an approach provides a simpl<br />

peratur'e and the coefficients of tenrperature- means to take into account elastic-plastic deand<br />

heat-c<strong>on</strong>ductivity; rand /- are time and formati<strong>on</strong> of cavity-c<strong>on</strong>taining rocka, which<br />

spatial coordinate$ so and 8 are the original seems to be d<strong>on</strong>e first in a paper of Wood and<br />

and current poaiti<strong>on</strong>s of the freezing fr<strong>on</strong>t XB- Goodman (1975). The elastio stage of deformadiua;<br />

tf is c<strong>on</strong>cealed heat of phaae traneiti<strong>on</strong>; ti<strong>on</strong> iB limited by the pressure Level which<br />

w is total moisture c<strong>on</strong>tent; L' = 1, a&,-&SCr), is calculated in the 8ame manner aa d<strong>on</strong>e by<br />

and i = 2, S(r)sr*so are the unfrozen,and fro- Dubina (1986) using the formula<br />

zen z<strong>on</strong>es of 8. freezing water-c<strong>on</strong>taining maas;<br />

i 3 is the frozen z<strong>on</strong>e that includes the<br />

space filled with a freezing mass; T,, is the<br />

natural, undisturbed temperature of frosen soil<br />

involving the space and the cooling temperature<br />

of a cylindrical (spherical) shell of radius<br />

& involving the space, in which T&,Z)n case<br />

I r, ; is the radius of the inner shell pla- where & is rock presswe.<br />

ced at the center of the freezing mass<br />

( 0 6 aL So , which occura for certain variants For the stage of elastio-plastic deformati<strong>on</strong><br />

of engineering practice; 7+ , Tpte) is the of rocka, depending <strong>on</strong> the kind of tl plaeficity<br />

original and current value of temperature of c<strong>on</strong>diti<strong>on</strong>, the xelati<strong>on</strong>ahip (IO) can be obtrithe<br />

water-to-ice phase transiti<strong>on</strong>; C6- and bd ned in the form of a n<strong>on</strong>linear algebraic equaare<br />

admixture salt c<strong>on</strong>centrati<strong>on</strong> and its dif- ti<strong>on</strong> for p . In the case of n<strong>on</strong>compreaaibility<br />

fusi<strong>on</strong> coefficient; k is the distributi<strong>on</strong> coef- of a freezing mas8 and rigidity of its internal<br />

ficient describing the effect of partial ea- boundary in xadiua r-ct this equati<strong>on</strong> simpultim<br />

of admixture salt ( o I k rl ); C" fp) plifies to an explicit relati<strong>on</strong> P(S) which le<br />

is the initial diatributi<strong>on</strong> of admixture salt; given for the Mieees fluidity c<strong>on</strong>diti<strong>on</strong> beceu-<br />

P ( C 1 is the pressure in the given unfrozen Be the expressi<strong>on</strong>s for the Coulomb-Moore COMAti<strong>on</strong><br />

axe unwieldy. Accofdin& to Dubina (19861,<br />

for p>pc I we have<br />

z<strong>on</strong>e that is unable to resist to shear deformati<strong>on</strong>s;<br />

M is the maas of 1 kilomole of solvent;<br />

R is a universal gas c<strong>on</strong>stant; El , $1 , FRi ,<br />

and are the elastic modulus, Poiw<strong>on</strong>'s coefficient,<br />

the yield point, ana angle the of internal<br />

fricti<strong>on</strong>; d~ = i-& /&, ia the coefflcient<br />

ofvolumestrain of the freezing mass<br />

( olv >O j; and P 1 is cylindrical symmetry<br />

and a 2 ie spherical symmetry.<br />

The syetem (1)-(10) involves the following relati<strong>on</strong>ships:<br />

heat c<strong>on</strong>ducti<strong>on</strong> equati<strong>on</strong> (1);<br />

the Stephan c<strong>on</strong>diti<strong>on</strong> at the fr<strong>on</strong>t of a phase<br />

transiti<strong>on</strong> (2); initial and boundary o<strong>on</strong>diti<strong>on</strong>s<br />

of the heat exchange problem (3) and (4); diffusi<strong>on</strong><br />

equati<strong>on</strong> for admixture salt (5) and a<br />

relevant balance equati<strong>on</strong> at the fr<strong>on</strong>t of freezing<br />

(6); initial and boundary c<strong>on</strong>diti<strong>on</strong>s for<br />

the admixture field c<strong>on</strong>centrati<strong>on</strong> (7) and (8); Examinati<strong>on</strong> of (12) suggekt~t an important o<strong>on</strong>-<br />

Equati<strong>on</strong> of ice formati<strong>on</strong> phase diagram (9) ob- CluaiOn about the limitedneare of preeeures in<br />

tainable from the equality c<strong>on</strong>diti<strong>on</strong> for chemi- the cavity due to the quantity &p the<br />

cal potentials at the phaae separati<strong>on</strong> bounda- expressi<strong>on</strong>s for which follow Prom (12) if it ia<br />

ry; and a soluti<strong>on</strong> to the problem of the atres- assumed that S4

REDUCTION TO ORDINARY DIFFERENTIAL EQUATIONS<br />

The ayetem (1)-(10) presented here is too complicated<br />

to be solved, even if proper allowanoe<br />

is made for simplificati<strong>on</strong>s to the mechanical<br />

part of variants (12) and (13) under c<strong>on</strong>siderati<strong>on</strong>.<br />

Numerical estimates can, n<strong>on</strong>ethelesa, be<br />

obtained by further aimplifying the formula-<br />

and k, I w & The notati<strong>on</strong> used is the<br />

following: &, and .Fc0 are the thickness of<br />

the walls and the elasticity modulus of the<br />

ti<strong>on</strong> of the problem. Assuming the unfrozen z<strong>on</strong>e shell that forms the space; and kt and ke are<br />

to have no temperature gradient (i P 11 and thetolums elasticity modulus of the unfrozen<br />

the temperature diatributi<strong>on</strong> in the frozen z<strong>on</strong>e and frozen phases of a freezing mass. The reto<br />

be quasi-atati<strong>on</strong>my (i I 2) and by specify- sults of the calculati<strong>on</strong> for the elastic space<br />

ing the cooling temperature <strong>on</strong> the c<strong>on</strong>- axe marked by solid lines, and those for the<br />

t OUT , we aimpliiy c<strong>on</strong>aidexably the heat elastic-plastic space are shown by dashed liexchange<br />

part of the problem etatemsnt. We also nes. Cases of the absence of salinizati<strong>on</strong> for<br />

simplify the diffuai<strong>on</strong> part asauming both re- the elastic-plastic space are marked by dashgi<strong>on</strong>s<br />

of the freezing mass to have no gradient dot lines. A total of seven calculati<strong>on</strong> vaxias<br />

well aa the abeence of admixture in surroun- ants are shown in Figs 1-4. Variant 1 corresding<br />

rocks, and write the redistributi<strong>on</strong> of p<strong>on</strong>da to curves 1.1-1.3 plotted for three vaadmixture<br />

salt ocourring at the fr<strong>on</strong>t ( ), lues of initial mass c<strong>on</strong>centrati<strong>on</strong>: X. = 2.5;<br />

according to the c<strong>on</strong>centrati<strong>on</strong> balance equa- 5; and 15 kg/m3 for = 263 K. Curves 2 and 3<br />

ti<strong>on</strong> in the unfrozen z<strong>on</strong>e, in the form corresp<strong>on</strong>d to Q-. 1.103 and 0.3~103 MPa for<br />

TH = 268 K and XO 5 15 kg/m3; curves 4 and 5<br />

corresp<strong>on</strong>d to the same values of TM and & but<br />

withx:, a 0. Plots 6 and 7 have been c<strong>on</strong>structed<br />

for an elaatic-plastic model of rocks involving<br />

th cavity, for the aame @,> = 1 MPa$<br />

6 I 5*103 MPa; and X. a 5 kg/m3 for TN I 268<br />

and 263 K. Curven 1-5 also corresp<strong>on</strong>d to freezing<br />

in a eingle ahell for which So = 0.27 m<br />

where & is initial c<strong>on</strong>oentrati<strong>on</strong> that Is and Efo- 2.105 NWa, while the value 3f G3<br />

uniform throughout the entire freezing mase. 5 1.10 MPa corresp<strong>on</strong>ds to & = 2-10' m and<br />

that of 41 0.3~103 MPa corresp<strong>on</strong>ds to 6so =<br />

Bearing in.mj.nd all of the assumpti<strong>on</strong>e made, = 6.7~10-4 rn. The qualitative implicati<strong>on</strong>s of<br />

<strong>on</strong>e is able to reduce the system (1)-(10) to the analysis results regarding the calculati<strong>on</strong>s<br />

two ordinary differential equati<strong>on</strong>s for an el- made in this paper may be summarized a8 follows.<br />

aatic-plaetic model of the behaviour of rocka<br />

*ad foraase of a freezing between two elarjtic<br />

ahella (hxbina, 1986). Equati<strong>on</strong> (9) is the<br />

firef of theee equati<strong>on</strong>e which should inoorporate<br />

the sea<strong>on</strong>d expressi<strong>on</strong> of (81, thue enabling<br />

the unknown C, to be eliminated. Besides<br />

equati<strong>on</strong> (9) should include the explicit relati<strong>on</strong><br />

of P(S)snd C(S) of the form (12) and<br />

(14). The aec<strong>on</strong>d equati<strong>on</strong> is known to have the<br />

form<br />

In the case of a viscous-elastic model for defoxmati<strong>on</strong>,<br />

with the exp<strong>on</strong>ential form rela- of<br />

xati<strong>on</strong> cores 4,. ( , t ), the problem can<br />

also be reduced to aolving ordinary differential<br />

equati<strong>on</strong>a (Dubinand Krasovitsky, 1985).<br />

AN WIPLL CALCULATION<br />

Pig8 1-4 present the calculati<strong>on</strong> results <strong>on</strong> the<br />

axisymmetrical. cam of a water soluti<strong>on</strong> of salt<br />

NaCl freezing in a space produced by an elastic<br />

shell of radius Soor a space in a natural<br />

sook which is c<strong>on</strong>eidered for both an elastic<br />

and elastic-plastic model. In all exampleB the<br />

following parameter are assumed c<strong>on</strong>stant I bo =<br />

1374<br />

P 3600 s; Tp0 = 273 K; Po = 0.1 IVlPa ( 4 being<br />

the pressure scale); A = 8.32~103 J/(K.mole);<br />

N= 0.018 kg/mole; .t! m 334.103 J/kg; ;Ira 2.21<br />

W/(m-K);+ e 1000 kg m3;4 = 910 kg/m3; 40 =<br />

I 0.01 m; Eso I 2.10 f MPa; a m 0; s, = 1 rn;<br />

CONCLUSIONS<br />

1. 1<br />

In the case of the absence of salinizati<strong>on</strong> the<br />

water-c<strong>on</strong>taining mass either is able to Preeze<br />

campletely or the parameters s , p , and<br />

& asawe ateady-state values <strong>on</strong> an infinite<br />

time interval. In the presence of salinizati<strong>on</strong><br />

the parameters S , p , & , and C, assume<br />

steady-state valuea <strong>on</strong> a finite time interval.<br />

In the case where the remaining c<strong>on</strong>diti<strong>on</strong>e<br />

remain unchanged, salinizati<strong>on</strong> reducee<br />

the value of the pressure being evolved, in<br />

proporti<strong>on</strong> to the degree of salinizati<strong>on</strong> but<br />

increases the atsengthening of the material<br />

c<strong>on</strong>taining the freezing mass. Proper account of<br />

plastic deformati<strong>on</strong>s of rocks, with other c<strong>on</strong>diti<strong>on</strong>s<br />

remaining unaltered, reduces c<strong>on</strong>siderably<br />

the level of evolving preseure. When the<br />

CoulombPoore fluidity c<strong>on</strong>diti<strong>on</strong> is applied,<br />

an increase of the angle of internal fricti<strong>on</strong><br />

of rockc3, J3 , lead5 to an increaee in preasu-<br />

xes and time of freezing.<br />

2. Viscous-elastic treatment (Dubinand Kraso-<br />

VitSkY (19851.<br />

When the variability of is taken into account,<br />

the process of freezing proceeds at lower<br />

rates. Without salinizati<strong>on</strong>, the water-c<strong>on</strong>taining<br />

mass freezes completely, with extrema<br />

of the parametere p and %<strong>on</strong> the freezing<br />

interval. If the freezing of a viscous-elastic<br />

maas proceed8 within an elastic space or between<br />

elastic shells, then the mass is able to

1000 2000 3000 To 7000 2000 3000 Z<br />

Fig.1 Behaviour of a Dimensi<strong>on</strong>less Fr<strong>on</strong>t<br />

of Phase Transiti<strong>on</strong>$ as a Functi<strong>on</strong> of<br />

Time To.<br />

Fig.2<br />

Transiti<strong>on</strong> Temperature r, .<br />

The lime Variati<strong>on</strong> of Phaae<br />

PI Mna<br />

80<br />

60<br />

Ol 06<br />

40<br />

4 04<br />

20<br />

402<br />

1000 2000 3000 To<br />

Pig.3 Growth Variati<strong>on</strong><br />

a Functi<strong>on</strong> OP Time.<br />

of Preesure p ae Fig.4 Behavioux of Admixture C<strong>on</strong>oentrati<strong>on</strong><br />

in the Unfrozen Z<strong>on</strong>e C, as a<br />

Functi<strong>on</strong> of Time.<br />

freeze partially, with the parameters S ,P ,<br />

and i& assuming ateady-atate VQlUe8 during a<br />

finite time interval. The presence of rralinizati<strong>on</strong><br />

leada to a partial freezing, with the ma-<br />

1375<br />

nifeatati<strong>on</strong> of the remaining peculiarities<br />

menti<strong>on</strong>ed above.

3. The estimating calculati<strong>on</strong>s we have carried<br />

out in thih paper dem<strong>on</strong>strate the poasibility<br />

of making 8. quantitative predicti<strong>on</strong> of ice formati<strong>on</strong><br />

in c<strong>on</strong>fined spaces taking into amount<br />

the degree of salinizati<strong>on</strong> as well as irreversible<br />

deformatl<strong>on</strong>a of rocks, uaing a relatively<br />

simple technique.<br />

REFEFiRPNCES<br />

Dubina, M.M. and Krasovitsky, B.A. (1983).<br />

Teploobmen i mekhanika vzaimodeietviya<br />

truboprovodov i akvazhin s grunfami. 136<br />

P., 'NOVOBibirak.<br />

Rubina, W.M. (1986). Priblizhenny raschet<br />

zafverdevaniya binarnoi smesi v osesimmetrichnykh<br />

yOmk08fyakh. ZWTF, No. 4,<br />

79-83.<br />

Dubina, M.M. and Krasovitsky, B.A. (1985).<br />

Zamerzanie taloi z<strong>on</strong>y vokrug Bkvazhiny v<br />

merzlykh porodakh a uchetom zavisimoati<br />

temperatury zamerzaniya ot davleniya.<br />

IZhKh, v.X, 122-129.<br />

Pekhovich, A.I. (1983). Osnovy gidroledotermii.<br />

200 p., Leningrad: Energoatomizdat.<br />

Laningr . o td.<br />

Wood, U.B. and Goodman, M.A. (1975). A mechanical<br />

model for permafrost fraeze-back<br />

pressure behavior. SPEJ, v.15, No.4,,<br />

287-301.<br />

1376

ENVIRONMENT PROTECTION FOR MINING<br />

ENTERPRISES IN PERMAFROST REGIONS<br />

E.A. Elchaninov<br />

Skochinsky Institute of Mining, Moscow, USSR<br />

SYmOPSIS Paatexpanding and developingminingindustryin permafrost rkgi<strong>on</strong>s puts<br />

forward a great number of envir<strong>on</strong>ment protecti<strong>on</strong> problems. 'Phe degree of influence of the main<br />

technological processee in mining <strong>on</strong> natural. complexes is defined and classified by investigati<strong>on</strong>s<br />

at the mining enterprises. The paper deals with eome results obtained by the investigati<strong>on</strong>s<br />

of the polluted mine air, the pumped-out mine water, a great amount of waste rock p<br />

<strong>on</strong> the surface, and surface subsidence caused by underground mining affecting natural complexes<br />

The entire complex of natural o<strong>on</strong>diti<strong>on</strong>s under ti<strong>on</strong>s have proved that the affects and influenoe<br />

of separate subsystems and - even less<br />

a wide influence of the technologic aubaystems<br />

forms the background for the industrial acti- so - the interacti<strong>on</strong> of the subsystems can be<br />

vities during mining mineral deposits in the detected and found out but after a l<strong>on</strong>g time,<br />

permafrost regi<strong>on</strong>s. !Che results of thie intar- sometimes 15-20 -years and more.<br />

acti<strong>on</strong> are determined by the character of the<br />

media transformed becauee of the activities By their degree of influence a11 the subsyrsof<br />

mining facilities. So there appears a neces- terne can be divided into the following:<br />

sity to find out what is being transformed and - subsyetems of limlfed inPluenoe (they C~UBB<br />

how it is being d<strong>on</strong>e. !The insufficiently groun- mining subsidence, form rock spoil heape,<br />

ded soluti<strong>on</strong>e of imperfect technology for mi- propagate karat and lakea, eta.)<br />

ning minerals may result grave in c<strong>on</strong>sequences - subsystems of regi<strong>on</strong>al influence (they give<br />

or even irreversible disturbance of envir<strong>on</strong>- birth to the iffluents of gas, heat, c<strong>on</strong>denment.<br />

sate, etc.)<br />

- aubaystems of unlimited influence (they are<br />

Let us c<strong>on</strong>sider the interacti<strong>on</strong> between the resp<strong>on</strong>sible for the iffluents of duat and<br />

mvfroment and 8 mining facility i.e. a col- mine water)<br />

liery<br />

!Che operati<strong>on</strong>al range of the subsyetems of li-<br />

When operating a coal-mining facility c<strong>on</strong>sumes mited influence is restricted by the mine dista<br />

certain volume of fresh air for ventilati<strong>on</strong>, rict or deposit. The subs stems of regi<strong>on</strong>al<br />

takes water out of reselvoira for spraying influence include the efffuents Liable fra- to<br />

system and fire-extinguishing pipelines for vel 50-60 km and more outside the limits of a<br />

the aake of safety, obtain= timber of out fo- mine district. The z<strong>on</strong>e of influence of the<br />

reets to proceed with mining operati<strong>on</strong>s in subsystems of unlimited influence cannot be<br />

workings, extracts minerals and rock out of difinad because their operati<strong>on</strong>al range is not<br />

entrails of the earth, drains gas and water out restricted by any distance.<br />

of rock to provide for normal c<strong>on</strong>diti<strong>on</strong>s of<br />

underground operati<strong>on</strong>s.<br />

Let us c<strong>on</strong>sider briefly the menti<strong>on</strong>ed wbsyetems<br />

At the same time any mining facility cannot<br />

help being a source of polluted air c<strong>on</strong>tain- Both development of mine workings to provide<br />

ing gases, moisture and mineral particles, an access to a mineral and extracti<strong>on</strong> of the<br />

c<strong>on</strong>siderable amount of c<strong>on</strong>taminated under- mineral result in changing the landscape, i.e.<br />

ground water with chemical and biological com- they cause subsidence to form day falls, pits,<br />

p<strong>on</strong>ents, and Pinally great mass of barren<br />

faults, creeping wastes, ravines, etc. Up<strong>on</strong><br />

rock is extracted from any mine and has to be appearing the falls and pits are suffused with<br />

dumped at aome dispoaal area. Each such extrac- water in rain and snow-melting seaa<strong>on</strong>s to form<br />

ti<strong>on</strong> of effluent represents a subsyntem of mi- lakes, heat owerne and ravines.<br />

ning facility - nature interacti<strong>on</strong>.<br />

At he same time as the mineral is mined the<br />

In ita turn each of the subkystemms menti<strong>on</strong>ed goaf and cavities are filled up with the graembarks<br />

<strong>on</strong> interacting with another or several dually caving rocks. The height of rock caving<br />

other similar subsyrrtema to form a whole eys- and the degree of landscape disturbance and<br />

tern of influences up<strong>on</strong> the nature. Investiga- thus that of the geocryological situati<strong>on</strong><br />

1377

depend up<strong>on</strong> the depth of occurence of a mineral<br />

*<br />

Provided the depth of mining doee not exceed<br />

60-90 m it leads to day falls with sheer<br />

brbks. When mining aem8 outcrops under overburden<br />

sediments the day fall depth can be as.<br />

much as the thickness of the extracted mineral's<br />

seam. The day falls are filled up with<br />

top-Boil together with trees and buehes. They<br />

are snowdrifted in winter and filled up with<br />

water in summer to from artificial lakes, and<br />

it deteriorates the pemafroet with wash-out<br />

of their banks to follow. There axe day fall<br />

areas from 3 to 15 thousand sq.m. registered<br />

at mining facilities with hillside landscape.<br />

As the depth of mining increases up to 150-200<br />

m terrah disturbances are come across rarer.<br />

In this case the geomechanical tranefomati<strong>on</strong>s<br />

of the surface lead to formati<strong>on</strong> of moulds of<br />

mbeidence accompanied with small fallsthmugh,<br />

scarps and cracks. The moulds of subsidence<br />

represent a moat'typical form of the<br />

eomechanical transformati<strong>on</strong> of terrain under<br />

fhe influence of mining . AB a mle, their<br />

Bises corresp<strong>on</strong>d to those of the goaf, while<br />

the depth does not exceed the projecti<strong>on</strong> of<br />

the extracted mineral seam thickneaa <strong>on</strong> the<br />

vertical plane.<br />

!We amall falls-through are, developed provided<br />

the cave-in z<strong>on</strong>e reaches the surface, i .e.<br />

the depth of mineral occurrence is less or<br />

equal to the -thioknese of caved rock layere.<br />

H a<br />

Y<br />

(K-1) COSM<br />

L -La the length of extracted<br />

part of the deposit al<strong>on</strong>g the<br />

strike.<br />

With the excepti<strong>on</strong> of the z<strong>on</strong>e of falls the<br />

maximums subsidence of surface-in a displacement<br />

mould reaches 65-90 per cent of the<br />

summed-up thickness of extracted mineral. An<br />

average inclinati<strong>on</strong> of a displacement mould<br />

from its axis is 80-95 mm/m. Fissure gapping<br />

and degree of damage depend <strong>on</strong> the value of<br />

mould of subsidence. !Che first degree of damage<br />

is represented by the cracka and fissure<br />

gappings up to 30 m wide, the sec<strong>on</strong>d degree<br />

- up to 100 mm, the third degree - up to 250<br />

mm the fourth degree - up to 1000 mm, the<br />

fihh degree includes the cracka wider than<br />

1000 mm and day falls.<br />

For example, in a mine with the depth of mining<br />

up to 200-220 m and the summed-up thickness<br />

of coal seams about 12 m the meximum<br />

surface subsidence has reached 7.0 - 7.2 m.<br />

In another mine with the Eturmned-up thicknese<br />

of extracted coal seam8 26-27 m the maximum<br />

depth of the mould of subsidence has reached<br />

17.4 - 18.6 m. Tn the bottom of the mould <strong>on</strong>e<br />

could observe some breaks of surface cover and<br />

cracks and fissure gappings of 0.3 to 2.15 m.<br />

which have collected the water of the seas<strong>on</strong>melted<br />

snow and the Elided-down top-soil peat<br />

layer, and it has lead to superfluous dzainage<br />

and general thawing from 0.7 to 1.9 Y. The<br />

disturbed area has reached 12 milli<strong>on</strong> 8a.m.<br />

where<br />

Y- ie the mineral thickness<br />

extracted<br />

K-is the coefficient of filling<br />

the goaf with caved rock<br />

(1.1 4 K 4 1.5).<br />

The size of a fall-through can be detemined<br />

from the following relati<strong>on</strong>s:<br />

2(&<br />

+ 2Ho* tgET<br />

Bf I 0.5 - Lf . af<br />

L<br />

where Lf-is the width of fall-through<br />

Yv-is the vertical thickness of<br />

mineral 3 M/cosoC<br />

Ho-is the thickness of -overlay-<br />

ing sediments over the mining<br />

operati<strong>on</strong>s<br />

&-is the angle<br />

&- 45' - 0.59 *<br />

of coal Beam dip<br />

af-is the depth of fall-through<br />

Vfis the volume of fall-through<br />

Fig.1.<br />

Scheme of surface disturbance ebove<br />

an extracted coal seam<br />

C<strong>on</strong>secutive mining of several<br />

seams of a mi-<br />

' 1378

nerd result B corresD<strong>on</strong>di .ngly in successive<br />

repeated displacemen%s of the total cover<br />

thickness. Each displacement changes the geocryological<br />

situati<strong>on</strong> and it ia caused by additi<strong>on</strong>al<br />

breaka of the surface and by a redietributi<strong>on</strong><br />

of straine and stresses.<br />

The new moulds with craaks in bottom and walls<br />

are filled up with water. In case the water in<br />

the mould gets completely freezed in winter,<br />

then, there is formed an ice bowl with a lot<br />

of wedge-like ice veins.penetrating the rock<br />

maesif. At the aame the it reduces the general<br />

temperature of the massif and the reducti<strong>on</strong><br />

reaches 0.6 - l.O°C in two years. The radiati<strong>on</strong><br />

balance remains at the previous level.<br />

The vegetati<strong>on</strong> cove,r around the ice lake remains<br />

unchanged, too. If the depth of a reservoir<br />

does not allow the water to get Preezed<br />

to the bottom, then, under the bottom the<br />

permafrost begins melting to form slush which<br />

is quick to sink in the rock massif because of<br />

the water filling up the cracke and fissures.<br />

In the case the radiati<strong>on</strong> balance around the<br />

reservoir undergoes sharp changes. The changes<br />

start from the mould edges with disturbed vegetati<strong>on</strong><br />

cover. In summer the radiati<strong>on</strong> balance<br />

ie a8 high a8 32-37 kcal/sq. cm while usually<br />

it ie 26-29 koal/sq.cm. Every year the destructi<strong>on</strong><br />

wave expands al<strong>on</strong>g the edges of displacements<br />

to force teh vegetati<strong>on</strong> cover to<br />

disappear and to develop themnokarst and<br />

ravines.<br />

The started cryogenic processes caused by the<br />

mining operati<strong>on</strong>s lead to rather intensive<br />

and often fatal damage far the surface not<br />

<strong>on</strong>ly within the allotment, but <strong>on</strong> the adjacent<br />

areaa, the rate of destructi<strong>on</strong> exceeding that<br />

of the cryogenic processes outeida the z<strong>on</strong>e of<br />

mining operati<strong>on</strong>s by doaens of timea.<br />

In order to reduce the harmful influence of<br />

mineral extracti<strong>on</strong> <strong>on</strong> the underworked surface<br />

there have been developed some feohnological<br />

schemes to mine coal Beams without caving or<br />

to provide smooth rock lowering without visible<br />

breaks of the peat cover. All the technological<br />

schemes are divided into 14 groups and 5<br />

types /I/ according to the geocryological and<br />

hydrogeological c<strong>on</strong>diti<strong>on</strong>s with rock stxuctum<br />

and technological c<strong>on</strong>diti<strong>on</strong>s taken into account.<br />

Resorting to the developed technological<br />

schemes haa made it possible to reduce the<br />

dgmage of the surface by 75-90 per cent and to<br />

tllhninafe the formati<strong>on</strong> of the artificial lakes<br />

thermokarsts and large day falls.<br />

During opening, development and mining of a<br />

mineral a c<strong>on</strong>siderable amount of barrea rock<br />

is delivered to the surface and has to be<br />

stored in waste dumps. fiery year a mine is<br />

used to deliver 100-150 thousand cu.rn. of barren<br />

rock to the surface to form enomous refuse<br />

heaps, each occupying an area of 10-15 thousand<br />

sq.m. Each refuse heap ia surrounded with<br />

a protecti<strong>on</strong> z<strong>on</strong>e of Borne 80-90 thousand 8q.m.<br />

Without sanitary protecti<strong>on</strong> the top-soil cover<br />

of the surface is quickly destroyed, the permafrost<br />

ie deteriorated, the rock of the refuae<br />

heap get sunk in the peat cover of the tundra<br />

to squeeze out a circular soil bank around<br />

itself thua providing the c<strong>on</strong>diti<strong>on</strong>s for<br />

alternating the temperature mode of the nextto-surface<br />

layer. (fig. 2)<br />

Fig.2. Scheme of aurface diertuxbance with<br />

a waste dump<br />

New refuse heaps alter the permafroat Bituati<strong>on</strong>s.<br />

The temperature mode of the reiusle<br />

heaps depend8 <strong>on</strong> the air temperature and <strong>on</strong><br />

the oxidati<strong>on</strong> of sulphide knclusi<strong>on</strong>s oome<br />

aoross in coal fines and rock. The oxidatisn<br />

and burning of refuse heap rocks provide an<br />

additi<strong>on</strong>al source of air polluti<strong>on</strong>.<br />

Tn order to reduce the volume of barren rook<br />

delivered to the suxffacs there is a technology<br />

worked out to drive "in-semn developments a d<br />

to mine a mineral without extraoting rock /2/.<br />

For the case when it is hposeible to mine a<br />

mineral wothout extracti<strong>on</strong> of barren rock and<br />

lifting it to the sureace, there ere given<br />

some technical soluti<strong>on</strong>s to utilis8 the barren<br />

rock as building material for road-building<br />

or as filling-up material in the goaf. For<br />

this purpoae 1 cu.m, of out-of-mine rock is<br />

2.0 - 2.5 times cheaper than that of building<br />

material specially produced at ta quarry.<br />

The effluent of ventilati<strong>on</strong> air ie accompanied<br />

with rock and coal flue dust escape, carb<strong>on</strong><br />

dioxide, methane, oxidas, moieture, heat efe.<br />

from the mine workings to the atmosphere. Ita<br />

tranepera~~cy is being changed to blacken the<br />

snow cover at a radius of 35-50 km, or even<br />

150 km in case of str<strong>on</strong>g winds typical of Siberia<br />

and the Far North. About 0.1 - 1.5 per<br />

cent of total daily coal output turned into<br />

dust goea in the air to say nothing of 200-300<br />

thoueand cu.m. of methane, 36-65 thousand cu.<br />

m of carb<strong>on</strong> dioxide, aeveral thousand cu.m of<br />

blasting oxides together with 180-360 thousand<br />

kJ of heat released. The spread coal duat has<br />

diminished the snow albedo by two-three times<br />

to abeoxb more aolar radiati<strong>on</strong> and to make the<br />

snow.thaw 12-17 days earlier. It has resulted<br />

in deeper waming-up of top-soil and increas-<br />

1379

ing of the seas<strong>on</strong>'s thawing from 0.4-0.6 to The preaentday drainage methods are resp<strong>on</strong>si-<br />

0.9-1.1 m at a flat country and from 0.8-1.15 ble for the fact that the mine water is comto<br />

1.6-2.1 m at southern slopes. The century- bined with the inflow water form to the mine<br />

settled heat balance has been upset to lead to discharge water. The drainage water from the<br />

greater swamping, thermokarsts, land slides, boreholes are directed to the workings to be<br />

etc. Besides, the aocelerated anow thawing mixed with water inflow in .the water collect<br />

caueed greater inflow of polluted water into ors and then to be pumped out to the surface<br />

lakes and rivers used as water aupplies. The where it is to undexgo purificati<strong>on</strong> and be<br />

water polluti<strong>on</strong> ha8 provoked aome further discharged.<br />

ehangea to start other subsystems mnning.<br />

Bieh spawningrand waterfowl nestings have been In order to ,cut down the volume of discharge<br />

disturbed, certain plants have been substitu- water to be purified there are intercepti<strong>on</strong><br />

ted b other plants, i.e. sed e and willow- schemes worked out to catch discharge water<br />

herb have substituted moea, cfoud-berry and with the help of advance, raiee and unloading<br />

blueberry. Changes in the vegetative cover boreholes, receiving it in special collectors<br />

influenced migrati<strong>on</strong> of lemming, polar-fox<br />

and delivering it to the surface to be used<br />

and reindeer.<br />

for technical or drinking purposea without<br />

any additi<strong>on</strong>al purificati<strong>on</strong>. The discharge<br />

In order to reduce the harmful effect of the water requires aerati<strong>on</strong> to release dissolved<br />

Ventilati<strong>on</strong> effluent we have developed a comp- gaees and ir<strong>on</strong> dioxide. The drainage boreholes<br />

lex of technical means and measures includi'ng make it possible to intercept about 70 per<br />

a reducti<strong>on</strong> of effluent comp<strong>on</strong>ents by chang- cent of water inflow and <strong>on</strong>ly 30 per cent of<br />

Ing the moiBture c<strong>on</strong>tent and temperature of it is pumped out as diecharge water. Special<br />

the air flow workings, partial methane Cap- OOnditlOns for removal of the discharge water<br />

ture and duet collecti<strong>on</strong> to burn them later are worked out. The discharge water ie direcin<br />

boilers, utiliaati<strong>on</strong> of the hot effluent ted to the z<strong>on</strong>e af natural talica wich are<br />

to heat green-house8 and buildings /3/.<br />

not the fedding z<strong>on</strong>es for water-bearing subpexmafrost<br />

horia<strong>on</strong>es. In case there isno<br />

When mlnlng below permafrost layers pres- the<br />

Bure subpermaimat wafer is often come acrosa.<br />

The drainage to lower their level SB carried<br />

out before development operati<strong>on</strong>s. This leads<br />

to deprese the sub-zero isotherm, i.e. pernafrost<br />

penetratee into the rock massif. The<br />

rock maeeif being undermtnnad, wa the t orbeertag<br />

Level is subjected to destroytng and<br />

wafer is collected in the god. As there is<br />

no circulati<strong>on</strong> of water in the goaf the pemafrost<br />

grows, in caas the water circulati<strong>on</strong> in<br />

the goaf the pemafroet degradee.<br />

!Phe permafrost penetrati<strong>on</strong> into the rock masaik<br />

depends <strong>on</strong> the taperature of the rock,<br />

the degree of mineralizati<strong>on</strong> of the interstitial<br />

water as well as <strong>on</strong> fiseures and texture<br />

of the rook. Tt varies from 1.53 rn to 2.17 rn<br />

a year. As far as the permafroat degradati<strong>on</strong><br />

is c<strong>on</strong>cerned it spreads an fast a6 5.75-8.29<br />

m a year.<br />

Both removal and discharge of the permafrost<br />

wafer exeralse a great effect <strong>on</strong> the eurface<br />

radius of feed<br />

Req<br />

stability. Up to 50 thouaand cu.m. 09 water<br />

outline (fig. 3).<br />

are pumped out and discharged every day. !Che<br />

volume of the pumped-out water grows c<strong>on</strong>stant-<br />

Ly a@ the minig operati<strong>on</strong>s become deeper and<br />

Comouilet explosi<strong>on</strong>s are carried out to heightheir<br />

inundati<strong>on</strong> greater, Discharge of c<strong>on</strong>aiten<br />

the debit of the boreholes. The cavity<br />

dimensi<strong>on</strong>s are determined from the equati<strong>on</strong>:<br />

derable volume of water leads to bank erosi<strong>on</strong><br />

and its polluti<strong>on</strong>, to development of thennokarst,<br />

to disintegrati<strong>on</strong> of engineering efwctures,<br />

and to formati<strong>on</strong> of vast icings at subzero<br />

,temperatures.<br />

k<br />

Besider~, fish spawning8 and bird nestings axe<br />

diaturbed and food fish and game birds tend<br />

to disappear.<br />

In order to reduce or completely elbinate the<br />

injuriuue effects of the water discharge <strong>on</strong><br />

the envir<strong>on</strong>ment there are several technical<br />

soluti<strong>on</strong>s worked out to ahange the approach to<br />

the water discharge and to utilize it either as<br />

technical, OF even drinking water.<br />

z<strong>on</strong>es of natural open taliks the water is<br />

pumped down in the boreholes drilled below the<br />

deposit level. In order to heighten the filtrati<strong>on</strong><br />

and absorpti<strong>on</strong> coefficient of the<br />

pumped-down water we resort do dispersed comouflet<br />

explosi<strong>on</strong>s in the boreholes. The discharge<br />

rate of the boreholes am determined<br />

accroding to the equati<strong>on</strong> /4/:<br />

where c-is the coefficient for rock<br />

cracks<br />

13-is the thickness of the rock seam<br />

to pump water in<br />

Po - P,+e the presaure differential<br />

RI-is the borehole radius<br />

- is the .equivalent<br />

where<br />

dch- is the charge diameter<br />

k - is the coefficient of pemneability.<br />

1380

The maximum radius o f cracks (Rc) is calculated<br />

fromt<br />

R, = k dch<br />

3aking into account the hydrodynwrdc resistance<br />

of seam which'depends <strong>on</strong> the radius of cracks<br />

the equivalent radius is determined as follows;<br />

At present aome technical methods are being<br />

developed to use the water discharged from<br />

mine for transportati<strong>on</strong> of extracted mineral,<br />

for operati<strong>on</strong> OP hydraultc turbines, for<br />

breaking rock and mineral, to c<strong>on</strong>trol. rock<br />

reasure and support a seam exposure or barng,<br />

etc.<br />

P<br />

Applicati<strong>on</strong> of the developed technical methode<br />

has made It polssible to completely eliminate<br />

(Fn some cases) or reduce by 50-60 per cent<br />

the hannf'ul effect of the water diecharge<br />

up<strong>on</strong> the envir<strong>on</strong>ment.<br />

Fig.3.<br />

d!<br />

Scheme of water-collecting boreholes<br />

with artificially heightened crack<br />

formati<strong>on</strong><br />

Not E less hannful effec.t <strong>on</strong> the envir<strong>on</strong>ment<br />

is exercised by felling to satisfy the timber<br />

needs of a miming facility or that of the<br />

pers<strong>on</strong>nel employed by the facility. Under the<br />

permafrost c<strong>on</strong>diti<strong>on</strong>s all the trees are under<br />

~Fzed and it takes greater felling areas to<br />

satisfy the needs. Usually the felling atrew<br />

are quite close to the mining facility. During<br />

Last 25-30 years the felling area has reached<br />

aeveral hundred sq.km. It would'take a century<br />

or more to re-cultivate the treee under these<br />

c<strong>on</strong>diti<strong>on</strong>s. As a rule, the forest-offence<br />

areas gat covered with bushee, become bogged<br />

up with aome kindls of plants substituted by<br />

the other types. In its turn it activatesother<br />

subsyetems such as flora, fauna, eto.<br />

In order to exclude timber for support uae at<br />

the mining facilitiee seveeaal meaaurea have<br />

been developed to use instead of it the hydraulic,<br />

metal and powered supports as well<br />

aa the rock-c<strong>on</strong>solidating c<strong>on</strong>crete and chmical<br />

mixtures, eynthetic resins, cera-c<strong>on</strong>crete,<br />

etc. Applicati<strong>on</strong> of these substitutes and<br />

technical means has allowed a mining facility<br />

to reduce the timber requirements by 80-90 per<br />

cent.<br />

With the type design practice for mineral<br />

mining technology being over according to a<br />

great many of factors of interacti<strong>on</strong> to take<br />

account of the influence of teohnology up<strong>on</strong><br />

nature and the naturela reacti<strong>on</strong> and res <strong>on</strong>se<br />

to this or that technology, if c<strong>on</strong>firms !he<br />

idea o f that the nature and a technology are<br />

the elements of a aingla system. Due to the<br />

feet if is necemary to resort to a systematio<br />

approach. The systematic approach allowfl to<br />

oomprehens3.vel.y understand the nature-techno-.<br />

logical and geotechological ;systeme the<br />

main elements of which are nature and teehnology<br />

This approach posrrbsea a great potential it<br />

because it is directed at formati<strong>on</strong>, first of<br />

all, of a single whole syetm without trying<br />

to ltinscribefi separate technical soluti<strong>on</strong>s in<br />

the nature through a mining technology and to<br />

make their activities agree with the nat;Uml<br />

proceseee. Thus, at preeent the o<strong>on</strong>dithns<br />

have become imminent and urgent when it is<br />

nscessaxy nbt <strong>on</strong>ly to establish a technology,<br />

but to design a geotechnological sya'tem to<br />

completeXy cooperate with the nature. It is<br />

the <strong>on</strong>ly appraoch that givee the opportunity<br />

to forecast If not all, then, a good many of<br />

the detrimental after-effacte of a coal-mining<br />

technology <strong>on</strong> the natural envir<strong>on</strong>ment as up11<br />

am to make arrangamenta to avoid or elimlnate<br />

them<br />

REFERENCES<br />

Provisi<strong>on</strong>al inBtmcti<strong>on</strong>s for choosing supports<br />

of coal-mining workings under the pemafrost<br />

c<strong>on</strong>diti<strong>on</strong>s. MOBCOW, Scochinsky Institute<br />

of linhg, 1979, 40 pp-<br />

Tec&icd schemes for winning and aevelopment<br />

operati<strong>on</strong>s at the collieries of the producti<strong>on</strong><br />

unit "Severovostokugol'l, Moscow,<br />

Scochinsky Institute of Mbining, 1977, 84<br />

PP<br />

Elchaninov E.A. State of art and waya to xeduce<br />

the envir<strong>on</strong>mental dioturbmcea during<br />

mining in pemarrost regi<strong>on</strong>s. In:<br />

'IReeistWce of the eurface against the<br />

technogenic activities in permafrost regi<strong>on</strong>sll.<br />

Yakutsk, Siberian Department of<br />

the USSR Academy of Sclmnces, 1900, pp.<br />

43-49.<br />

Lovlya S.A., Gorbenko, L.A., KO Lan B.L, Tor<br />

pedoing and perforati<strong>on</strong> of !orehoLes.<br />

Yoacow, Goetachidat, 1959.<br />

1381

ARCTIC MINING IN PERMAFROST<br />

H.M. Giegerich<br />

Cominco Alaska Incorporated, Pasndena, Califarnia, USA<br />

SYNOPSIS This paper describes mine c<strong>on</strong>structi<strong>on</strong> and operati<strong>on</strong> in Arctic permafrost at three mining projects by<br />

Cominco Ltd. of Canada - the Black Angel Mine in Greenland, the Polaris Mine in Canada's arctic islands, and the Red<br />

Dog Project in Alaska. A major challenge in Arctic development is to overcome the problem of permafrost, or to use<br />

its unique engineering properties. At Black Angel, minlng is not areatly affected by permafrost, as the rock is<br />

str<strong>on</strong>g with little moisture. Bullding foundati<strong>on</strong> design included c<strong>on</strong>structi<strong>on</strong> <strong>on</strong> frozen glacial fill. The Polaris<br />

Mine has taken advantage of permafrost in underground extracti<strong>on</strong> and support methods. Foundati<strong>on</strong>s for the major<br />

structures were frozen into place to give the stability normally supplied by c<strong>on</strong>venti<strong>on</strong>al c<strong>on</strong>crete. <strong>Permafrost</strong> at<br />

Red Dog is a technological problem, as it is relatively warm. The major design cri,teria are therefore to prevent thaw.<br />

INTRODUCTION<br />

Cominco Ltd. is a Canadian-based mining and<br />

netallurglcal firm which has been developing<br />

and operating mines in northern Canada for 50<br />

years, starting with the C<strong>on</strong> Gold Mine at<br />

Yellowkni.fe. in 1938, and followed by the Pine<br />

Point. leadlzinc operati<strong>on</strong> in 1965. Both of<br />

these mines are in the Northwest Territories<br />

(Figure 1).<br />

More recently, the Black Angel LeadlZinc Mine<br />

started up in 1973, and the Polaris LeadlZinc<br />

operati<strong>on</strong> achieved commerclal producti<strong>on</strong> in<br />

early 1982. Cominco is presently c<strong>on</strong>structing<br />

the Red Dog Lead/Zinc/Silver Mine in Alaska,<br />

and this operati<strong>on</strong> is scheduled to begin<br />

producti<strong>on</strong> in early 1990.<br />

Developing an Arctic mine requires new and<br />

different approaches, to reduce the negative<br />

ec<strong>on</strong>omic effects of climate and locati<strong>on</strong>. One<br />

of the major challenges is permafrost - either<br />

to overcome the related problems, or to<br />

utllize its' unique engineering properties.<br />

The physical characteristics of permafrost<br />

vary with soil type, moisture c<strong>on</strong>tent, and<br />

temperature. Therefore, the relati<strong>on</strong>ship<br />

between these factors wil determine if<br />

permafrost wil be an asset or a liability.<br />

"<br />

Black A m 1 Mine (Underground Mine)<br />

The Black Angel Mine is in Maarmorilik Fjord<br />

<strong>on</strong> the west coast of Greenland, at latltude<br />

710 N, about 500 km north of the <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

Airport at S<strong>on</strong>dre Stromfjord. All pers<strong>on</strong>nel<br />

and air freight are moved between S<strong>on</strong>dre<br />

Stromfjord and the mine by helicopter. Figure<br />

1 shows the locati<strong>on</strong> of airport and mine.<br />

The Black Angel Mine began operati<strong>on</strong> in 1973,<br />

at a mining rate of 600,000 t<strong>on</strong>nes of ore per<br />

year. Total project tlme from approval by<br />

Cominco to commercial producti<strong>on</strong> was 17<br />

m<strong>on</strong>ths.<br />

The mine is in fjord country, wlth steep<br />

cliffs, and a plateau at about 1,000 m.<br />

elevati<strong>on</strong>. The Greenland ice cap comes close<br />

to the edge of the plateau, and the glaciers<br />

discharge Icebergs into the fjords. The<br />

ground is perennially frozen down to<br />

approximately 450 m.. and rock temperatures in<br />

the mine are -lo0 to -12O C.<br />

The Black Angel mineral z<strong>on</strong>e is generally flat<br />

lying and outcrops about 600 meters above sea<br />

level, <strong>on</strong> the face of a steep cliff. Figure 2<br />

is a photograph of the Black Angel Cliff.<br />

1382

structural fill under the slabs-<strong>on</strong>-grade from<br />

Even though the mine itself I s in permafrost, which all material finer than 1 cm was removed<br />

the ground is c<strong>on</strong>sidered to be excellent, as<br />

in order to create volds which would serve as<br />

it i s composed primarily of marble and insulatl<strong>on</strong>. As well. rigid foam insulati<strong>on</strong><br />

1 imest<strong>on</strong>e, and with few faults. As a result, was placed <strong>on</strong> top of the fill and under the<br />

there was little moisture in the initial slab, to ensure that any water <strong>on</strong> top of the<br />

mining areas. However, as the mine advanced slab would not freeze.<br />

deeper into the cliff and under the ice cap,<br />

the development headings ran out The of service buildings at the Black Angel Mine<br />

permafrost, and water was encountered in these which Were built <strong>on</strong> the frozen glacial till<br />

areas. Th'is caused some dlfficultles. as the c<strong>on</strong>sisted of either a pre-engineered<br />

water drainlng back through the existing industrial structure <strong>on</strong> a c<strong>on</strong>crete slab, or a<br />

workings in the permafrost created severe ice prefabricated accommodati<strong>on</strong> unit <strong>on</strong> timber<br />

problems for access and equipmcnt.<br />

footings, The general method of c<strong>on</strong>structl<strong>on</strong><br />

was to excavate the permafrost to below the<br />

Another difficulty was in drllling, both core<br />

active layer (or depth of summer thaw), and<br />

for explorati<strong>on</strong> and percussi<strong>on</strong> for productl<strong>on</strong>,<br />

then backfill with crushed and screened rock,<br />

as the normal method for cooling the bit, plus<br />

as in the c<strong>on</strong>centrator. Rigid foam insulati<strong>on</strong><br />

c<strong>on</strong>trolling dust and recovering the cuttings,<br />

was also placed <strong>on</strong> top of the fill and under<br />

i s to use water. Due to the rock the c<strong>on</strong>crete slabs. This is shown in Figure<br />

temperatures, a brine soluti<strong>on</strong> c<strong>on</strong>sisting of 4,<br />

up to 7% calcium chloride was required. in<br />

order to have a drllling fluid that would not<br />

freeze. This created problems due to cost, as<br />

well as corrosi<strong>on</strong> <strong>on</strong> equipment and Skln rashes<br />

<strong>on</strong> people exposed to the brine. Otherwise,<br />

the operati<strong>on</strong> of the mfne was not particularly<br />

affected by permafrost. Very little backfill<br />

was used to replace the mlned ore, although<br />

some c<strong>on</strong>siderati<strong>on</strong> was given to the<br />

possibility of filling the open stopes with<br />

gravel or waste, and freezing. However, to<br />

date this has not been d<strong>on</strong>e to any great<br />

extent.<br />

The ore storage bins, both in the mine and at<br />

the mil 1 site, were excavatid out of rock,<br />

which also was in permafrost. Again, due to<br />

the low water c<strong>on</strong>tent, no slgnificant freezing<br />

of the stored ore was encountered.<br />

One of the design problems for the Black Angel<br />

The prefabricated accommodati<strong>on</strong> ur ts<br />

plant was the limited area (12 ha.) across the<br />

c<strong>on</strong>structed <strong>on</strong> permafrost were set <strong>on</strong> tln 11'<br />

nbl :r<br />

fjord from the mine, <strong>on</strong> whlch blocks the placed directly <strong>on</strong> top of the<br />

c<strong>on</strong>centrator, power plant, service buildings,<br />

and accommodati<strong>on</strong>s are located (Figure 3).<br />

Much of this site i s covered with an<br />

unc<strong>on</strong>solidated glacial till, permanently<br />

frozen over a marble bedrock. The<br />

c<strong>on</strong>centrator foundati<strong>on</strong>s were excavated out of<br />

rock because of the geotechnical c<strong>on</strong>cerns with<br />

building <strong>on</strong> a frozen base. The <strong>on</strong>ly<br />

c<strong>on</strong>cessi<strong>on</strong> to permafrost was to use a<br />

1383<br />

structural fill, and an air space left under<br />

the bulldings to ensure that heat could not<br />

pass into the fill. Figure 5 shows the<br />

foundati<strong>on</strong> design. A total of 15 buildtngs<br />

were sited <strong>on</strong> the frozen till, using the<br />

methods described above, and of these, there<br />

was <strong>on</strong>ly <strong>on</strong>e significant failure, due to a<br />

subsurface summer water course which was not<br />

detected during the excavati<strong>on</strong> of th<br />

foundati<strong>on</strong>.

The deposlt Is much larger than the Black<br />

Angel Hlne, with greater producti<strong>on</strong>. The<br />

Polarls Mine achieved commercial producti<strong>on</strong> in<br />

March, 1982, just 28 m<strong>on</strong>ths after the<br />

"go-ahead" decisl<strong>on</strong> by Cominco, and is<br />

presently operating at 25% above design rates.<br />

The topography of Little Cornwallis Island i s<br />

rolling, with low relief. The highest point<br />

is 140 m above sea level, and several<br />

freshwater lakes are present, <strong>on</strong>e of which<br />

supplies water for the operatl<strong>on</strong>.<br />

BLA CX ANGEL<br />

PR€FA6R/CAT€D ACCOMMODAt/ON FOUNDA T/ON<br />

I - I<br />

The other aspect at Black Angel which was<br />

affected by permafrost was water supply. Al<br />

fresh water flows cease for five to six m<strong>on</strong>ths<br />

during the winter. There are many fresh water<br />

lakes <strong>on</strong> top of the plateau, which could have<br />

been used as a water source, but the problems<br />

of c<strong>on</strong>structing pipe lines down the steep<br />

cllffs made it difficult to ensure a<br />

dependable water system. Therefore, sea water<br />

was utllized in the process, and potable water<br />

was made in desalinators using waste heat from<br />

the dlesel generator exhaust.<br />

Several innovative steps were taken at<br />

Polaris, including c<strong>on</strong>structi<strong>on</strong> of the main<br />

plant facilities <strong>on</strong> a 30 rn. by 130 m. barge in<br />

southern Canada. This was then towed for<br />

5,000 km. up the west coast of Greenland and<br />

through the Northwest Passage to Little<br />

Cornwallls Island, where it was ballasted down<br />

In a permanent berth, and within two m<strong>on</strong>ths of<br />

arrival was processlng ore (Figure 7).<br />

""""""""<br />

The Polaris Mine (Underground Mine)<br />

The Polaris Mine in northern Canada (Figure 6)<br />

is Comlncols most recent operati<strong>on</strong> in the<br />

Arctic, and is the most northerly metal mine<br />

In the world. Polaris is <strong>on</strong> Little Cornwallis<br />

Island, at latitude 76O, north of the<br />

Northwest Passage, and 1,500 km from the North<br />

Pole (Figure 1). Again, the mine is in<br />

permafrost, down to 400 meters below surface,<br />

with rock temperatures in the upper part of<br />

the ore z<strong>on</strong>e in the range of -loo to -12O C,<br />

about the same as the Black Angel. The ore<br />

also goes down to about 400 m, so the bottom<br />

of the mine will be almost out of the<br />

permafrost.<br />

Other Innovatl<strong>on</strong>s to counteract permafrost, or<br />

to utllize the unique structur<br />

characteristics of permafrost, were also<br />

made. The mineral deposlt itself c<strong>on</strong>sists of<br />

massive sulfide deposits in a karst formati<strong>on</strong><br />

In limest<strong>on</strong>e, with many voids which are filled<br />

with ice. On average, the ore z<strong>on</strong>e c<strong>on</strong>tains<br />

up to 5% ice by volume. Wfthout permafrost,<br />

this would be a difflcult orebody to mine, as<br />

the cementatl<strong>on</strong> provided by the ice is<br />

necessary to overcome the basic Instabillty of<br />

the rock. The perennially frozen c<strong>on</strong>diti<strong>on</strong> of<br />

the Polaris deposit is therefore a distlnct<br />

advantage from the standpoint of mining, and<br />

it is essential that the mine be kept below<br />

freezing temperature at all times. This was a<br />

major c<strong>on</strong>cern during the c<strong>on</strong>ceptual design of<br />

Polaris, and after commencement of operatl<strong>on</strong>,<br />

lt was found necessary to instal 1 a<br />

refrigerati<strong>on</strong> plant in order to cool the<br />

ventllati<strong>on</strong> air entering the mine during the<br />

three warm summer m<strong>on</strong>ths.<br />

The problems encountered at the Black Angel in<br />

using a brine soluti<strong>on</strong> for percussi<strong>on</strong> drl'lling<br />

of the frozen ore were eliminated at Polaris<br />

by drv drlllina. Cuttings are removed with<br />

comp r essed air; and a vacuum system <strong>on</strong> the<br />

drill machine collects dust. However, a brine<br />

solut i<strong>on</strong> is still required in diam<strong>on</strong>d core<br />

drill i ng.<br />

1384

The mining of the underground ore at Polarls The other major structure at Polaris 1s the<br />

also benefited from permafrost and the cold c<strong>on</strong>centrate storage building, which is 230 m.<br />

winter temperatures. The baslc mining plan is l<strong>on</strong>g, 55 m. wlde and 30 m. high. Again, the<br />

a "room-and-pillar" method, whereby the ore is permafrost was utilized by freezing in<br />

removed in open stopes, with pillars of the pre-fabricated footings for the foundati<strong>on</strong>s,<br />

same dimensi<strong>on</strong> left between the openings. The<br />

so that very little expensive c<strong>on</strong>crete was<br />

open area is then filled with waste material<br />

required. A method similar to<br />

from the surface which c<strong>on</strong>tains about 10% accommodati<strong>on</strong>s was applied, except in this<br />

natural moisture, partly as snow. This case the foundati<strong>on</strong>s were a pre-built steel<br />

"backfill" is dumped down 2 m. bored fill grillage set <strong>on</strong> the frozen bedrock. The<br />

raises and spread in the open stopes, and trenches were then backfilled and watered, and<br />

additi<strong>on</strong>al water 1s added to bring the total<br />

the fill allowed to freeze in place, which<br />

moisture c<strong>on</strong>tent up to about 15%. The fill gave the lateral stability required for the<br />

material is allowed to freeze for some m<strong>on</strong>ths foundati<strong>on</strong>s. Figure 10 is a c<strong>on</strong>ceptual sketch<br />

until it becomes str<strong>on</strong>g enough to support the<br />

of this foundati<strong>on</strong>.<br />

roof of the stope, and the intervening pillar<br />

can then be removed, wlth the frozen<br />

llbackfill" supporting the mine. Figure 8<br />

shows this stope and pillar layout.<br />

POLAR/S<br />

CONCENTRATE STORAGE FOUNDAT/ON<br />

WLAR/S MINE<br />

&OPE 6 PILLAR LAYOUT<br />

\<br />

Advantage was also taken of permafrost in the c<strong>on</strong>sidered, including reinforced c<strong>on</strong>crete and<br />

foundati<strong>on</strong>s for the two main <strong>on</strong>-site steel. Finally, it was decided to use the<br />

structures. The accommodati<strong>on</strong> foundati<strong>on</strong>s features in the Arctic that are most comm<strong>on</strong> --<br />

c<strong>on</strong>sist of pre-cast c<strong>on</strong>crete pedestals, set in<br />

cold and permafrost. The dock was built of<br />

trenches dug into an area of weathered sheetpile cells, with crushed rock fill. A<br />

limest<strong>on</strong>e, After the pedestals were clrculating freezing system was installed in<br />

positl<strong>on</strong>ed and aligned, the trenches were<br />

filled with the excavated material. sprinkled<br />

with water, and the foundati<strong>on</strong>s wete frozen<br />

into place. Figure<br />

foundati<strong>on</strong> scheme.<br />

9 shows the accommodati<strong>on</strong><br />

The Polaris dock design was based <strong>on</strong> the<br />

engineering properties of permafrost. The<br />

major technical problem was the excessive<br />

pressure from multi-year ice, plus pressure<br />

ridges in the winter. Various designs were<br />

the fill, and over the following year,<br />

utilizing the winter cold, the broken rock was<br />

c<strong>on</strong>verted to permafrost.<br />

The water supply system at Polaris is also<br />

affected by permafrost. The fresh water<br />

source is a lake two miles from the mine.<br />

There is no ground water inflow because of<br />

permafrost, and recharge depends <strong>on</strong> runoff<br />

<strong>on</strong>ly. Studies indicated that the watershed<br />

would normally have sufficient capacity for<br />

the mine requirements. In the event of a<br />

partlcularly dry period, the supply could be<br />

significantly augmented by the use of snow<br />

fences to collect and retain larger quantities<br />

of snow. To date this has not been necessary.<br />

DOLAR/S<br />

ACCOMMODATION FQUNDATION<br />

eZ5L<br />

1385

"Ṛe<br />

does Hlne (Open Pi<br />

t Mine<br />

The ore reserve at Red Dog dwarfs any other<br />

Cominco resource, with almost 17 milli<strong>on</strong><br />

t<strong>on</strong>nes of Pb and Zn metal, and over 6 milli<strong>on</strong><br />

kg. of silver.<br />

Red Dog is in Northwestern Alaska, at latitude<br />

670 north, and 90 km. inland from the coast of<br />

the Chukchi Sea (Figure 1).<br />

The country around the mineral deposit is<br />

rolling hills, leadlng Into mountains of up to<br />

1,000 m. elevati<strong>on</strong>. (Figure 11) The deposlt<br />

Is at an elevatl<strong>on</strong> of about 300 m., and is in<br />

permafrost, but different from that<br />

encountered in Greenland or the Canadian<br />

Arctlc. The rock temperatures are <strong>on</strong>ly a few<br />

degrees below freezing, so the permafrost Is<br />

relatlvely fraglle, and can be fairly easily<br />

thawed, whlch adds cost to building roads and<br />

erecting structures.<br />

Another effect of the warm permafrost is <strong>on</strong><br />

the road from the portslte to the mlne. The<br />

majority of materlal underlying the road route<br />

is the ice-rich colluvium that can c<strong>on</strong>tain up<br />

to 30% ice, under 30 to 45 cm. of tussocky<br />

tundra. It is essential to preserve the<br />

tundra as an Insulatl<strong>on</strong> so that the frozen<br />

soil will not thaw, and therefore the road Is<br />

designed primarily as a built-up embankment.<br />

A mlnimum of 2.5 m. of fill wlll be placed <strong>on</strong><br />

a geotextlle mat which covers the width of the<br />

road. The purpose of the geotextile is to<br />

reduce the effect of rocks entering the voids<br />

between the tussocks, whlch could damage the<br />

roots and destroy the tundra (Figure 12).<br />

RED DOG PAOJECT<br />

ROAD CROSS-S€C7/ON<br />

f/G I2<br />

.. ... -"".<br />

The other area of the road design that is<br />

affected by permafrost is the foundatl<strong>on</strong>s for<br />

the bridges. These wil be steel piles driven<br />

Into the permafrost, with allowance for<br />

adjustment if any of the piles tend to "Jack"<br />

At Red Dog, in c<strong>on</strong>trast to Polarls, permafrost<br />

under the effect of the seas<strong>on</strong>al freeze-thaw<br />

Is an engineerlng problem. For example, the cycle in the active layer.<br />

mine is overlain with a combinati<strong>on</strong> of<br />

overburden and weathered mineral, ice-rich and<br />

Fresh water flows at Red Dog cease for the<br />

unstable. As well, much of the surface soil colder m<strong>on</strong>ths, simillar to the Black Angel and<br />

c<strong>on</strong>sists primarily of colluvium (wind-blown Polarls. To overcome this, a fresh water<br />

fines), and this materlal serves to create reservoir wlll be formed by an earth-filled<br />

additi<strong>on</strong>al instability, In the mine dam whlch will be c<strong>on</strong>structed in a drainage<br />

operati<strong>on</strong>, the permafrost in the ice-rich basin about 4 miles from the mlne. As well,<br />

Surface material wil require that this be recycle of process water will be maxlmlzed, to<br />

mined <strong>on</strong>ly while frozen. The hlgh moisture reduce fresh water c<strong>on</strong>sumpti<strong>on</strong> and therefore<br />

c<strong>on</strong>tent would make handling this material the required sire of the reservoir.<br />

difficult if ,allowed to thaw. This is<br />

particularly important with the surface The final aspect of permafrost at Red Dog i s<br />

mineralized areas, whlch are high in soluble at the portsite, where the <strong>on</strong>shore solls<br />

heavy metals that have a1 ready created C<strong>on</strong>sist of about 15 m. of gravel, sand, and<br />

significant c<strong>on</strong>tamlnatl<strong>on</strong> in the area, and sllt over bedrock, with up to 30% molsture as<br />

must be kept frozen so that addltl<strong>on</strong>al<br />

leaching wlll not take place.<br />

The plant site will be excavated down to good<br />

rock, to eliminate any c<strong>on</strong>cern in regard to<br />

the stability of the foundati<strong>on</strong>s, if thawed.<br />

The tailing dam will also be built <strong>on</strong><br />

permafrost, but the dam design allows for the<br />

probabi 1 ity that a "thaw bulb" will form under<br />

the taillng p<strong>on</strong>d andam. Therefore, the<br />

design includes flat embankment slopes with<br />

facllities for removing any dralnage water<br />

wlthln the structure.<br />

1386<br />

ice in the upper layers. The oil storage tank<br />

foundati<strong>on</strong>s c<strong>on</strong>sist of 2 m. of fill placed<br />

over the frozen ground, covered by 10 cm. of<br />

insulatl<strong>on</strong>, and with 0.5 m. of fine topplng<br />

over the insulati<strong>on</strong> (Flgure

RED DOG PROJ€CT<br />

O/L TANK FOUNDATION<br />

I<br />

I<br />

However, it is not posslble to c<strong>on</strong>struct the<br />

large c<strong>on</strong>centrate storage bullding at the<br />

shore because of probable creep In the<br />

ice-rich soils under the weight of the<br />

c<strong>on</strong>centrate. Therefore, the c<strong>on</strong>centrate<br />

storage bulldlng wl be located 1,400 m.<br />

inland where there is bedrock under 3 m. of<br />

frozen overburden. The overburden wl be<br />

removed and the c<strong>on</strong>centrate storage building<br />

foundati<strong>on</strong> wl be sited directly <strong>on</strong> the rock.<br />

SummarLnnd-c<strong>on</strong>elusr<strong>on</strong>s<br />

This paper summarizes the c<strong>on</strong>structi<strong>on</strong> and<br />

operati<strong>on</strong> of three minlng projects in the<br />

Arctic regi<strong>on</strong>s, and some of the practical<br />

aspects of dealing with permafrost. It 4s<br />

posslble to take advantage of the englneering<br />

features of perennially frozen sol1 and rock.<br />

However, even If the permafrost 1 s not an<br />

advantage, it must always be cdnsldered, as<br />

problems can be encountered if the<br />

characteristics of permafrost are ignored.<br />

1387

APPLIED STUDY OF PREVENTING STRUCTURES FROM FROST<br />

DAMAGE BY USING DYNAMIC CONSOLIDATION<br />

Han, Huaguang and GUO, Mingzhu<br />

Heil<strong>on</strong>gjiang Provincial Low Temperature C<strong>on</strong>structi<strong>on</strong> Science <strong>Research</strong> Institute, Harbin, China<br />

SYNOPSIS Some applied examples of subsoil treatment by using dynamic c<strong>on</strong>solidati<strong>on</strong> in<br />

buildings with shallow foundati<strong>on</strong>s, large tanks, road and sports ground engineerings have been introducted<br />

systematically in this paper. Our engineering practice shows that this treatment is a new<br />

technique for preventing structure from frost damage reliably and ec<strong>on</strong>omicaly and can be used widely<br />

in future.<br />

INTRODUCTION<br />

Since 1982, a dynamic c<strong>on</strong>solidati<strong>on</strong> c<strong>on</strong>structi<strong>on</strong><br />

method has been used in Daqing, Harbin and other<br />

districts for treatment of frost susceptible<br />

subsoil, and lots of test engineerings were c<strong>on</strong>ducted<br />

at sametime, such as: industrial buildings,<br />

public and dwelling buildings with shallow<br />

foundati<strong>on</strong>,-large oil and gas tanks, water pools,<br />

pipe piers, pipe shelvers, road, large sports<br />

ground and so <strong>on</strong>. Our experimental results and<br />

operati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong> of above various buildings<br />

for years were described and discussed in this<br />

paper.<br />

APPLIED EXAMPLES OF ENGINEER INGS<br />

Shallow foundati<strong>on</strong><br />

Generally speaking, a main p roblem for large<br />

building set up <strong>on</strong> str<strong>on</strong>g frost susceptible subsoil<br />

with shallow groundwater level is to prevent<br />

the buildings from frost damage. A dynamic<br />

c<strong>on</strong>solidati<strong>on</strong> method for improving subsoil such<br />

as silty clay with bog or p<strong>on</strong>d was used in some engineerings.<br />

The brief c<strong>on</strong>diti<strong>on</strong>s of test engineerings<br />

by using dynamic c<strong>on</strong>solidati<strong>on</strong> is<br />

shown In Table I.lt is obvious :hat buildings<br />

with shallow foundati<strong>on</strong> can be set up <strong>on</strong> str<strong>on</strong>g<br />

frost susceptible subsoil as l<strong>on</strong>g as the dynamic<br />

c<strong>on</strong>solidati<strong>on</strong> technique is designed properly and<br />

coefficients are selected correctly.<br />

Anti-heave practice for foundati<strong>on</strong> of unheated<br />

open structures<br />

This kind of structure with a deep frost depth<br />

under foundati<strong>on</strong>, affected by air temperature<br />

directly, is easy to be suffered frost hazard,<br />

especially when the load up <strong>on</strong> foundati<strong>on</strong> bed<br />

is not heavy and its c<strong>on</strong>structi<strong>on</strong> is undertaken<br />

over winter or years. In order to prevent above<br />

structures from frost damage, a treatment of<br />

dynamic c<strong>on</strong>solidati<strong>on</strong> method has been used in<br />

the engineering base in the area of crude oil<br />

tanks. The c<strong>on</strong>diti<strong>on</strong>s of dynamic c<strong>on</strong>solidati<strong>on</strong><br />

used in crude oil tank area is listed in Table<br />

11. From Table I1 we know that even though the<br />

structures set up <strong>on</strong>' the,ground surface with<br />

frost susceptible subsoil, by using dynamic c<strong>on</strong>solidati<strong>on</strong><br />

method, all of tanks have worked<br />

well. Meanwhile, a large amount of materials<br />

and m<strong>on</strong>ey has been saved, What we have to point<br />

out is tank 76 and 77 started to work after c<strong>on</strong>structi<strong>on</strong><br />

for two years: tank 78 was set up in<br />

the next year after subsoil treatment by dynamic<br />

c<strong>on</strong>solidati<strong>on</strong> and started to work in third year;<br />

and all of the tanks were built in the subsoil<br />

with a middle sand or asphalt sand cushi<strong>on</strong> with<br />

a thickness of <strong>on</strong>ly 0.3 to 0.45 m. Pipe piers<br />

and pipe shelvers were directly set up in spring<br />

in the pits with a depth of 1.2 m formed by<br />

dynamic c<strong>on</strong>solidati<strong>on</strong>, They, with a little load,<br />

have been worked well for years without any obvious<br />

frost heave and differential deformati<strong>on</strong><br />

caused by freeze-thawing cycles. As a c<strong>on</strong>clusi<strong>on</strong>,<br />

frost heave of subsoil can be completely<br />

c<strong>on</strong>trolled by using dynamic c<strong>on</strong>solidati<strong>on</strong> and<br />

the treatment subsoil may be c<strong>on</strong>structed in<br />

frozen c<strong>on</strong>diti<strong>on</strong>.<br />

Preventi<strong>on</strong> of frost heave and boil road<br />

The subgrade, pavement, culvent, and bridge of<br />

road will be suffered frost damage in winter,<br />

and will be boiled or deformed differently in<br />

spring, which influences <strong>on</strong> transportati<strong>on</strong>, c<strong>on</strong>structi<strong>on</strong><br />

serviously in cold regi<strong>on</strong>s. For preventing<br />

road engineering from frost damage, the<br />

dynamic c<strong>on</strong>solidati<strong>on</strong> method has been used for<br />

treatment of subgrade.<br />

Test secti<strong>on</strong>s in two roads have been c<strong>on</strong>ducted<br />

in Daqing city. One of them named United road<br />

hfd a test length of 270 m and an area of 3300<br />

m . The secti<strong>on</strong> was set up <strong>on</strong> the subsoil of<br />

clay and sandy clay with a sandy gravel pavement.<br />

It used to be stopped working because of frost<br />

heave and boil until rebuilding with a c<strong>on</strong>crete<br />

pavement in 1984. The next secti<strong>on</strong> named Zh<strong>on</strong>gqi<br />

road had a length of 100 m, an area of 2500<br />

m , and was set up <strong>on</strong> the subsoil of sandy clay,<br />

silt and sandy, with asphalt pavement which<br />

replaced by c<strong>on</strong>crete pavement in 1985.<br />

The observati<strong>on</strong> results in both test secti<strong>on</strong>s<br />

with or without treatment subgrade by dynamic<br />

1388

I<br />

~~~ ~~~ ~ ~~<br />

TABLE I<br />

The C<strong>on</strong>diti<strong>on</strong>s of Test Engineering Ease by Using Dynamic C<strong>on</strong>solidati<strong>on</strong><br />

Engineering geologic Bearing capacity (MPa) Frost susceptibility Foundati<strong>on</strong> depth<br />

Projects c<strong>on</strong>diti<strong>on</strong>s BR AR BR AR BR AR<br />

(m)<br />

Notes<br />

dwelling silty m sandy c1ay:l quarry rammed quarry<br />

building thick groundwater:<br />

0. oast<strong>on</strong>e<br />

st<strong>on</strong>e in<br />

82, 82+ 0.5 m below the<br />

0.25 str<strong>on</strong>g no strip strip 1985<br />

0.12<br />

(six- surface footing<br />

storied 2.8-3.0 1.5<br />

dwelling silty sandy clay of<br />

quarry quarry rammed<br />

buildinn 0.5-1.0 m thick<br />

st<strong>on</strong>e st<strong>on</strong>e in<br />

5-1, 2 covered by €ill soil or strip 1984<br />

(six- of 0.8-1.2 m, 0.06- 0.22- rein- footing<br />

storied) groundwater talbe 0.12 0.25<br />

str<strong>on</strong>g no<br />

forced 1.5<br />

zf 0.8 m below the c<strong>on</strong>crete<br />

surface<br />

strip<br />

footing<br />

3.0<br />

labora-<br />

fill miscellaneous<br />

quarry quarry<br />

tory and silt 0 06- 0.15- of<br />

st<strong>on</strong>e st<strong>on</strong>e in<br />

(four- 1.0-1.5 m thick, 0.10 0.16 heave no footing footing 1986<br />

storied) groundwater 0.5 m of<br />

2.5 1.4<br />

below the surface<br />

dorm<br />

soil fill of 0.8- quarry quarry<br />

building 1.0 m in the upper, st<strong>on</strong>e st<strong>on</strong>e in<br />

(five- silty sandy clay of<br />

and footing 1986<br />

storied) 3-4 m below 0.08- str<strong>on</strong>g 0.18- weak<br />

rein- 1.5<br />

0.10 0.20 forced<br />

c<strong>on</strong>crete<br />

footing<br />

1.0<br />

training reed p<strong>on</strong>d fill and rammed pile<br />

center silty sandy clay of<br />

building 1.5-2.5 m thick<br />

c<strong>on</strong>crete 1985<br />

(seven- underlain by silty 0.06- 0.16-<br />

and<br />

storied) sand, groundwater 0*10 0.18 str<strong>on</strong>g no quarry<br />

table of 0.8 m<br />

st<strong>on</strong>e<br />

below the surface<br />

footing<br />

2 .o<br />

Notes: BR = before rammed<br />

AR = after rammed<br />

. .~ ""<br />

c<strong>on</strong>solidati<strong>on</strong> method are listed in Table 111, before the c<strong>on</strong>solidati<strong>on</strong> to 1.55 to -1.89 t/m'<br />

from which we know that the frost heave of sub- after the c<strong>on</strong>solidati<strong>on</strong>, and the void ratio is<br />

grade can be reduced greatly after the treatment. 0.55 to 1.42 before the c<strong>on</strong>solidati<strong>on</strong> and 0.45<br />

C<strong>on</strong>squently, boiling can be avoided also.<br />

to 0.75 after c<strong>on</strong>solidati<strong>on</strong>. The distributi<strong>on</strong><br />

of dry density and void ratio al<strong>on</strong>g depth is<br />

shown in Fig.1 and Fig.2.<br />

MAIN PROPERTIES OF FROST SUSCEPTIBLE SUBSOIL Water c<strong>on</strong>tent<br />

AFTEK A TREATMENT OF DYNAMIC CONSOLIDATON<br />

After dvnamic c<strong>on</strong>solidati<strong>on</strong>, the pore water pres-<br />

The properties of subsoil will be changed great- sure wiil be increased because the stress field<br />

ly after a treatment of dynamic c<strong>on</strong>solidati<strong>on</strong>,<br />

of subsoil is changed. The cracks in soil mass<br />

because the subsoil layer will be compressed<br />

will be occured while shock energy reaches a<br />

suddenly with a seftlsment of several to dozens<br />

critical value which makes free water, capillary<br />

centimeters while acted by kinetic energy of ram. water and some weak bound water in soil expelled<br />

al<strong>on</strong>g the cracks. The experimental results show<br />

After dynamic c<strong>on</strong>solidati<strong>on</strong>, the density of sub- that water 'Ontent is around 28 to 32z before<br />

soil will be increased with its porosity decreasthe<br />

c<strong>on</strong>solidati<strong>on</strong> with a maximum of 64%, and 16<br />

ing, The statistical results show that the<br />

to 23% with a maximum of28% after c<strong>on</strong>solidati<strong>on</strong>.<br />

density Qf subsoil is from 1.13 to 1.63 t/m' .

C".,n<br />

I r<br />

eroaea ay sol^ ana U,LU V.1IJ L dIIIlIICU<br />

steel tank acid in 1984<br />

tank 78<br />

rammed<br />

steel tank<br />

in 1984<br />

fill of 3-4 m<br />

soil<br />

rammed<br />

pipe shelf underlain by silty 0.08 0.15 heave no 2-3 1.6 in 1983<br />

1-22 sandy clay<br />

-<br />

pipe<br />

pier<br />

1-0<br />

TABLE I11<br />

The C<strong>on</strong>diti<strong>on</strong>s of Test Road Secti<strong>on</strong> by Using Dynamic C<strong>on</strong>solidati<strong>on</strong><br />

bgineering geologic Frost susceptibility<br />

Projects c<strong>on</strong>diti<strong>on</strong>s Pavement structure<br />

unrammed rammed<br />

subgrade was composed c<strong>on</strong>crete pavement mean mean rammed<br />

of sandy clay, ground- with thickness oE heave heave in 1984<br />

Uni<strong>on</strong> water table was 0.5 m 0.24 m underlain ratio ratio<br />

road belrn &.&a;or~inal by sand and gravel of 69.4% of 3.77%<br />

sand md gravel pavement<br />

was broken by boiling<br />

surface covered with c<strong>on</strong>crete pavement 100% decreased rammed<br />

sandy clay, silt sand; of 0.24 m thick, (assumed) by 40-50%, in 1905<br />

Zh<strong>on</strong>gqi I groundwater table was underlain steel<br />

road 0.5 m below the dregs, lime soil<br />

surface; asphalt and white lime<br />

pavement was boiled soil<br />

Permeability and nroundwater level<br />

The observati<strong>on</strong> results, obtained in door and in<br />

situ with tweleve engineering projects, show that<br />

the coefficient of permeability of soil decreases<br />

obviously after dynamic c<strong>on</strong>solidati<strong>on</strong>. In comm<strong>on</strong><br />

case, the coefficient of permeability of clay<br />

after the c<strong>on</strong>solidati<strong>on</strong> is less than 1x10-6 cm/s<br />

with a minimum of 1~10-~ cm/s. C<strong>on</strong>squently, it<br />

is an impermeable layer within the subsoil without<br />

any sand intercalati<strong>on</strong>. The groundwater<br />

level descends gradually from the beginning of<br />

ramming, and stays below the impermeable layer,<br />

Some observati<strong>on</strong> results are listed in Table IV.<br />

tests in laboratory have been c<strong>on</strong>ducted. The<br />

experimental results indoor are listed in<br />

Table V and the observati<strong>on</strong> results in situ are<br />

listed in Table VI, from which the frost heave<br />

of subsoil might be reduced or eliminited by<br />

using dynamic c<strong>on</strong>solidati<strong>on</strong>, Our experimental<br />

results show that the relati<strong>on</strong> between frost<br />

susceptibility of clayey soil after the c<strong>on</strong>solidati<strong>on</strong><br />

and ramming energy per squre meter<br />

is very close. The more the ramming energy per<br />

meter is, the less the frost heave ratio of subsoil<br />

is (see Fig.3).<br />

Frost<br />

susceptibility of foundati<strong>on</strong><br />

CONCLUSJONS<br />

In order to understand the frost susceptibility Our engineering prac.tice and experimental reof<br />

subsoil after dynamic c<strong>on</strong>solidati<strong>on</strong>, some sults show that the frost susceptibility<br />

of<br />

investigati<strong>on</strong>s in situ and frost susceptibility<br />

1390

. I icient<br />

Yig.1 The Distributi<strong>on</strong> of Dry Density and<br />

Void Ratio Al<strong>on</strong>g Depth for Dorm<br />

Fig.2 The Distributi<strong>on</strong> of Dry Density and<br />

Void Ratio Al<strong>on</strong>g Depth for billing Building<br />

TABLE IV<br />

The Changes of Groundwater Level before and<br />

after Dynamic C<strong>on</strong>solidati<strong>on</strong><br />

Projects<br />

Groundwater level (m)<br />

unrammed rammed<br />

Fig.3 Frost Heave Patio vs Ramming<br />

Energy Per Squre Meter<br />

Power plant 1.3 6.4<br />

Stable crude oil tank area 1.5 6.0<br />

Pipe ahelf 1.5 5.6<br />

Frozen ground testing stati<strong>on</strong><br />

in L<strong>on</strong>gfeng 0.3 4.8<br />

Uni<strong>on</strong> road in L<strong>on</strong>gfeng 0.3 3.0<br />

belling building<br />

0.8 5.9<br />

Office building 0.3 3.9<br />

belling building 82 and 83 0.5 6.2<br />

Training centre 0.3 3.9<br />

Daqing sports ground 0.6 3.7<br />

Laboratory 0.3 3.9<br />

Dorm 0.6 Ir.3<br />

frost susceptible subsoil in seas<strong>on</strong>a 1 frost regi<strong>on</strong>s<br />

may be reduced or eliminated a fter dynamic<br />

c<strong>on</strong>so lidati<strong>on</strong> while the uroDer coeff<br />

and<br />

ramming technology are selected reas<strong>on</strong>able with<br />

a given shock energy.<br />

kers: Mr.Tang Xiaobo, Mr..Wang G<strong>on</strong>gshan, Mr. Yu<br />

Guor<strong>on</strong>g, Mr. Zhu Liping, Mr. Deng Runhui and Mr,<br />

Qi Huayi in Daqing Design Institute of Chemical<br />

Industry and Mr. Wang Zuer<strong>on</strong>g in the First<br />

Architecture Company of Daqing city.<br />

Analysing cryogenic texture of rammed soil frozen<br />

in open system with undirecti<strong>on</strong>al freezing,<br />

we know that the ice c<strong>on</strong>tent was little without<br />

water accumulati<strong>on</strong> and ice segregati<strong>on</strong> in soil.<br />

C<strong>on</strong>squently, the treatment of subsoil by using<br />

dynamic c<strong>on</strong>solidati<strong>on</strong> is a new way for preventing<br />

structures from frost damage and increasing<br />

bearing capacity of subsoi.1. This c<strong>on</strong>structi<strong>on</strong><br />

method is very simple and can be used widely, so<br />

it is a valuable and practical technology.<br />

REFERENCE<br />

Wu<br />

Ziwang and Zhang Uiayi, (1982). Strength of<br />

frozen soil and its destructive power,<br />

Proceedings of I1 Nati<strong>on</strong>al <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong><br />

<strong>Permafrost</strong>, p.275-280.<br />

ACKNOWLEDGEMENTS<br />

The authors are grateful to the following cowor-<br />

1391

TABLE V<br />

The Results of Susceptibility Test in Laboratory<br />

Projects Sampling Number of Ratio of frost Mean frost heave<br />

depth(m) test heave (X) ratio ( X)<br />

2 19.0<br />

Before<br />

0.5-1.1 4<br />

5 20.7<br />

21.8 20.5<br />

rammed<br />

3<br />

1.1-1.5<br />

6 11.4<br />

Daqing<br />

sports 0.5-1.0 8 2.33<br />

ground 9<br />

After<br />

rammed<br />

1 .o-1.5<br />

10<br />

12<br />

15<br />

3.03<br />

I1 5.02<br />

1.5-1.8 13 5.07 4.64<br />

14 3.20<br />

Dorm<br />

Before 0.1-0.3 1 14.8<br />

.rammed 0.3-0.6 2 24.6<br />

19.7<br />

0.3-0.5 3 0.85 2.0<br />

After 5 3.03<br />

rammed 4 0.35<br />

0.5-0.7 2.0<br />

6 3.60<br />

1 -1.2<br />

1.0-1.5 3 0.39 0.1<br />

Dwelling After 5 0.98<br />

building<br />

rammed<br />

.1.5 2 -0.64<br />

4 -1.24<br />

-0.94<br />

TABLE VI<br />

The Results of Frost Susceptibility Observati<strong>on</strong> in Situ<br />

Projects<br />

Frost heave ratio ( W)<br />

Unrammed<br />

Rammed<br />

Frozen grouhd<br />

test stati<strong>on</strong> 9.3 0.8<br />

in L<strong>on</strong>gfeng<br />

Uni<strong>on</strong> road<br />

in L<strong>on</strong>gfeng<br />

Dwelling<br />

building<br />

6.94 3.77<br />

3.82 -1.4<br />

Crude oil<br />

tank area<br />

str<strong>on</strong>g<br />

heave<br />

-0.6<br />

1392

EFFECT OF HEATING ON FROST DEPTH BENEATH FOUNDATIONS OF BUILDING<br />

B<strong>on</strong>g, Yuping and Jiang, H<strong>on</strong>gju<br />

Oilfield C<strong>on</strong>structi<strong>on</strong> Design and <strong>Research</strong> Institute, Daqin Petroleum Administrative Bureau,<br />

Daqing, Heil<strong>on</strong>gjiang Province, People's Piepublic of China<br />

I<br />

SYNOPSIS This study was started in 1960's and then c<strong>on</strong>tinued at the beginning of 1980's.<br />

The purpose of this study was to determine the design values of Mt factor for eveluating the heating<br />

effect when the difference in elevati<strong>on</strong> between indoor and outdoor surface (Ah) was great than<br />

45 cm. The frost depth of 11 selected houses was detected and.the Mt values were calculated for<br />

the houses with different values of Ah. The relati<strong>on</strong>ship between Mt and Ah was found to be in a<br />

linear functi<strong>on</strong>. The heating still significantly affected the frost depth both at the corner of<br />

outside walls and the middle secti<strong>on</strong> of north facing walls when Ah was less than 75 cm. The Mt<br />

values were close to <strong>on</strong>e at northwest corner and in fracti<strong>on</strong> at the middle secti<strong>on</strong> of northern wall<br />

when Ah was equal to 75 cm.<br />

INTR0.DUCTION<br />

The study of the effect of heating <strong>on</strong> frost<br />

depth in subsoils i s of great significance for<br />

the stability of structure foundati<strong>on</strong>s in seas<strong>on</strong>al<br />

frozen regi<strong>on</strong>s. The ec<strong>on</strong>omical and reas<strong>on</strong>able<br />

design and c<strong>on</strong>structi<strong>on</strong> of foundati<strong>on</strong>s<br />

mainly depend <strong>on</strong> how well this study is carried<br />

out. Therefore, observati<strong>on</strong>s <strong>on</strong> the real structures<br />

have been started from 1960's and then<br />

c<strong>on</strong>tinued in the period from 1981-to 1986. Some<br />

results have been brought into the Standard of<br />

Foundati<strong>on</strong> Design in the Industrial and Civil<br />

Architecture (TJ7-74) and its revised editi<strong>on</strong><br />

in 1985. This paper is t o discuss the elemental<br />

results of this study.<br />

TEST AND OBSERVATION<br />

To understand the effect of house heating <strong>on</strong><br />

frost depth, the observati<strong>on</strong>s have been c<strong>on</strong>ducted<br />

<strong>on</strong> the selected houses under operati<strong>on</strong>.<br />

The structure of those houses is made up of<br />

brick-wood or brick-c<strong>on</strong>crete with single or<br />

multiple storeies, which is popular in China.<br />

This type of houses was usually using strip<br />

foundatian and brick wall. Indoor floor was<br />

directly built <strong>on</strong> ground surface. Thermocouples<br />

or indicators of frost depth were buried beneath<br />

both inside and outside walls and around the<br />

foundati<strong>on</strong>s. The observati<strong>on</strong>s <strong>on</strong> the eleven<br />

selected houses lasted in a period of ten years<br />

from 1961 to 1965 and from 1981 to 1986 and a<br />

lot of reliable data were collected.<br />

follows:<br />

Unevenness of frost penetrati<strong>on</strong> during freezinR<br />

The observed data show that the frost penetra .<br />

ti<strong>on</strong> of soils al<strong>on</strong>g the outside wall of foundati<strong>on</strong><br />

is developed unevenly, The base soils are<br />

Eirstly frozen beneath the four corners and<br />

beneath the middle secti<strong>on</strong> of the wall. The '<br />

time reaching to the maximal frost depth is also<br />

different, In a testing house, for instance,the<br />

maximal frost depth was reached <strong>on</strong> Mar.28 at<br />

northwest corner, <strong>on</strong> Mar.20 at the middle secti<strong>on</strong><br />

of the northern wall and <strong>on</strong> Feb.20 at the<br />

middle secti<strong>on</strong> of the southern wall, respectively.<br />

The frost penetrati<strong>on</strong> depth is the least<br />

at the middle secti<strong>on</strong> of the southern wall and<br />

its date reaching to the maximal frost depth is<br />

about <strong>on</strong>e m<strong>on</strong>th earlier than that at the middle<br />

secti<strong>on</strong> of the northern wall, The difference<br />

of frost depth in soils between two adjacent<br />

observed points of the foundati<strong>on</strong> reaches to<br />

the maximum in the middle ten days of Feb.when<br />

the frost depth of soilsreaches to 90% as deep<br />

as its maximum<br />

The thawing process of frozen soils around the<br />

outside wall foundati<strong>on</strong> is opposite to the process<br />

of freezing. Thawing at the middle secti<strong>on</strong><br />

of the southern wall occurs about two m<strong>on</strong>ths<br />

earlier than that at the northern wall. Thawing<br />

occurred at the middle secti<strong>on</strong> of the wall is<br />

earlier than that at the corner, and thawing<br />

occurred at the northern corner is the latest<br />

with about three m<strong>on</strong>ths later than that at the<br />

middle secti<strong>on</strong> of the southern wall.<br />

Unevenness of the maximal frost depth around<br />

the outside wall foundati<strong>on</strong>s<br />

FEATURES OF EFFECT OF HEATING ON FROST DEPTH The frost depth is deeper<br />

at four corners and<br />

much shallow at the middle of the foundati<strong>on</strong>.<br />

From the observed data <strong>on</strong> the eleven selected The date reaching to the maximal frost depth<br />

test houses, the features of the effect of changes with places, The observed data of a<br />

heating <strong>on</strong> frost depth could be summarized as test house are shown in Table I. A significant<br />

1393

TABLE I<br />

Maximal Frost Depth Observed at a Test House<br />

Locati<strong>on</strong> Southern wall middle of NE.<br />

E.wall corner<br />

No I I1 I11 IV V VI<br />

hmax 160 13.5.3 153.1 176.7 145.9 170.20<br />

D Mar.5 Feb.20 Feb.23 Mar.10 Mar.5 Mar.20<br />

Locati<strong>on</strong> Northern wall NW. niddle of<br />

corner W .wall<br />

. .<br />

*<br />

outdoor<br />

outdoor<br />

4.<br />

indoor<br />

No VI1 VI11 IX X X1 0<br />

hmax 157.4 168.5 177.3 180.2 166.7 190<br />

D Mar.20 Mar.20 Mar.20 Mar.20 Mar.20 Mar.20<br />

Note: hmax-the maximal frost depth,cm;<br />

"the date reaching to the maximal frost depth.<br />

thaw depth has occurred at the southern wall<br />

when the maximal frost depth is just reached at<br />

the eastern, northern and western walls. The<br />

maximal frost depth of the test house is shown<br />

in Fig.1. It can be seen that the places with<br />

remarkable changes in frost depth are at eastern<br />

and western gables, and at both ends of<br />

southern and northern lengthwise walls with the<br />

distance of 4 m from the corners (especially,<br />

at the ends of corners in the southern wall).<br />

Difference in the maximum frost depth between<br />

inside and outside of an outside wall foundati<strong>on</strong><br />

Observati<strong>on</strong>s show that the frost depth at inside<br />

of an outside wall foundati<strong>on</strong> is less than that<br />

at outside, and the difference in frost depth<br />

between inside and outside at corners o f an outside<br />

wall foundati<strong>on</strong> is less than that at the<br />

middle secti<strong>on</strong> of the foundati<strong>on</strong> (see Fig.2).<br />

From the three features of frost depth menti<strong>on</strong>ed<br />

above beneath foundati<strong>on</strong>s of the outside wall of<br />

a heating house, it is understood that the dif-<br />

Fig.2 Difference of Frost Depth Between<br />

Inside and Outside a of Foundati<strong>on</strong><br />

A: at the corner<br />

B: at the middle secti<strong>on</strong><br />

ferential deformati<strong>on</strong> of houses will<br />

be caused by frost heave and thaw settlement<br />

during freezing and thawing processes of subsoils,<br />

If the differential deformati<strong>on</strong> of house<br />

exceeds a critical limit, the cracks in house<br />

will be caused. Therefore, it is necessary to<br />

know the three features in the study <strong>on</strong> the<br />

stability of foundati<strong>on</strong>sin the seas<strong>on</strong>al frozen<br />

ground.<br />

DETERMINATION OF THE INFLUENCING COEFFICIENT OF<br />

HEATING ON FROST DEPTH<br />

The frost depth of subsoils beneath foundati<strong>on</strong><br />

Fig.1 Maximum Frost Depth in cm for a Test House<br />

(determined <strong>on</strong> Mar.20,1963)<br />

1394

+ .<br />

is redu.ced by the indoor heating of houses in<br />

winter. The reducing degree could be expressed<br />

as follows, which is so-called the influencing<br />

coefficient of heating <strong>on</strong> frost depth.<br />

Mt - Hh<br />

where Hh-the measured frost depth at the outside<br />

of the outside wall foundati<strong>on</strong> of a<br />

building;<br />

Hn-the frost depth of soils near by the<br />

building in natural c<strong>on</strong>diti<strong>on</strong>s with<br />

the bear surface (without snow or<br />

vegetati<strong>on</strong> cover). Note that Hh and Hn<br />

should be measured at the same time.<br />

The value of Mt is influenced by the fol<br />

factors:<br />

owing<br />

Influence of the indoor temperature<br />

For the unheated house, the Mt value at he<br />

corner of a house equals to <strong>on</strong>e, or even slightlv<br />

Greater than <strong>on</strong>e. But for the heated house.<br />

the-frost depth of subsoils beneath the foundatti<strong>on</strong><br />

is reduced. There are, for instance, two<br />

houses with the brick floor and the elevati<strong>on</strong><br />

difference of 30 cm between indoor and outdoor<br />

surface, the indoor temperatures of the two<br />

houses are 7.6 and 14°C (mean air temperature of<br />

Jan. and Feb.) respectively. The Mt values at<br />

northern corner of the houses are 0.94 and 0.84,<br />

respectively.<br />

Influence of elevati<strong>on</strong> difference between indoor<br />

and outdoor surface<br />

As shown in Table TI, the more the elevati<strong>on</strong><br />

difference (Ah) between indoor and outdoor surface,<br />

the greater the Mt value.<br />

TABLE I1<br />

Values of Mt €or Different Ah<br />

Ah 0 sn 50 7n<br />

Mt value 0.82 0.86 0.90 1.0<br />

Influence of the locati<strong>on</strong> al<strong>on</strong>n a foundati<strong>on</strong><br />

The values of Mt calculated from the data observed<br />

at a test house with Ah=30 cm in 1963-1964<br />

are shown in Table 111. As shown in Table 111,<br />

the Mt value at the corner is greater than that<br />

at the middle secti<strong>on</strong> of a wall, and for the<br />

middle secti<strong>on</strong>, the Mt value at the northern<br />

wall is greater than chat at the southern wall.<br />

In determiningthedesign values of Mt, the three<br />

factors menti<strong>on</strong>ed above should be c<strong>on</strong>sidered.<br />

But, for the general houses used for living and<br />

working, the indoor air temperature in winter<br />

is usually i.n the range of 15 to 18'C, i.e.,<br />

the temperature difference is <strong>on</strong>ly 3"C, so that<br />

the influence of temperature <strong>on</strong> M t value is<br />

insignificant. Therefore, the elevati<strong>on</strong> difference<br />

(Ah) and the locati<strong>on</strong> al<strong>on</strong>g foundati<strong>on</strong><br />

are the more important factors for determining<br />

TABLE I11<br />

Mt Values at Different Locati<strong>on</strong>s l<strong>on</strong>g a Foundati<strong>on</strong><br />

Locati<strong>on</strong> NW. Middle of SW. Middle of<br />

corner W.wall corner S .wall<br />

Mt value 0.84 0.62 0.80 0.50<br />

Locati<strong>on</strong> SE. Middle of NE. Middle of.<br />

corner E.wal1 corner N.wal1<br />

Mt<br />

Mt values.<br />

value 0.69 0.55 0.77 0.65<br />

For the engineering purpose, the two "representative"<br />

values of Mt are adequate. One is the<br />

Mr. value at the northern corner and another at<br />

the middle secti<strong>on</strong> of the northern wall. To determine<br />

the values of Mt, the frost depth al<strong>on</strong>g<br />

the outside wall foundati<strong>on</strong>s of the eleven<br />

testing houses was observed. The calculated<br />

values of Mt were shown in Table IV. Fig.3 shows<br />

the relati<strong>on</strong>ship between the Mt value and the<br />

TABLE IV<br />

Calculated Values of Mt for 11 Test Houses<br />

TVD~O€ Indoor NW. Mt Year of Type<br />

Ah fibor temp. cor- Mid- observa- of house<br />

( cd<br />

("C) ner dle of ti<strong>on</strong><br />

Y.wFI11<br />

0.00 c<strong>on</strong>crete 10-18 0.82 0.50 1982-84 two-storey<br />

brick<br />

30 0.94 0.77 1962-63<br />

30 brick 10-16 0.88 1962-63 single-storey<br />

30<br />

0.84 0.66 1963-64 brick-wood<br />

50 9-17 0.84 0.66 1982-83<br />

50 c<strong>on</strong>crete 9-17 0.98 0.79 1983-84 single-storey<br />

75 10-19 1.01 0.62 1982-83 brick-c<strong>on</strong>crete<br />

75 0.94 1983-84<br />

75 c<strong>on</strong>crete 13-18 0.93 0.70 1983-84 five-storey<br />

75<br />

75<br />

1.00<br />

0.93<br />

0.73 1984-85<br />

1984-85<br />

brick-c<strong>on</strong>crete<br />

elevati<strong>on</strong> difference (Ah) between the floor and<br />

natural ground surface, which is plotted from<br />

the data shown in Table IV.<br />

From figure 3 it can be seen tant the relati<strong>on</strong>ship<br />

between Mt and Ah i s nearly linear. The<br />

higher the value of Ah, the greater the value<br />

of Mt. The heating influence <strong>on</strong> frost depth is<br />

very obvious when Ah is less then 75 cm. It is<br />

obvious at the middle secti<strong>on</strong> of the wall and<br />

less obvious at the northern corner when Ah is<br />

equal to 75 cm.<br />

For the design value of Mt, it is described in<br />

the Standard of Foundati<strong>on</strong> Design in the Industrial<br />

and Civil Architecture (TJ7-74) that the<br />

1395

REFERENCE<br />

The Standard of Foundati<strong>on</strong> Design in the Industrial<br />

and Civil Architecture TJ7-74<br />

(1974). Beijing, Publishing House of<br />

Architecture Industry.<br />

Fig.3 Relati<strong>on</strong>ship Between Mt and<br />

A: at the northwestern corner<br />

B: at the middle secti<strong>on</strong> of the northern wall<br />

h<br />

value of Mt is equal to 0.85 at the corner of<br />

the outside wall and 0.70 at the middle secti<strong>on</strong><br />

of the outside wall, respectively, when the<br />

house is directly built <strong>on</strong> ground surface. By<br />

using those stipulati<strong>on</strong>s, even if. these houses<br />

are operated for a l<strong>on</strong>g period of ten years,<br />

they are stable, it proved that those stipulati<strong>on</strong>-s<br />

are safe and reliable. According to the<br />

stipulati<strong>on</strong>s J.n the Standard TJ7-74. Mt value<br />

equals to <strong>on</strong>e when the indoor temperature during<br />

heating is lower than 10°C and the elevati<strong>on</strong><br />

difference between indoor and outdoor surface is<br />

greater than 45 cm. But according to the data<br />

observed for several years(Fig.3 and Table IV),<br />

when Ah is in the range of 45 to 75 cm, the Mt<br />

values are in the range of 0.84 to 1.01 at the<br />

northern corner and 0,6 to 0.79 at the middle<br />

secti<strong>on</strong> of the northern wall, respectively. It<br />

indicates that heating still has c<strong>on</strong>siderable<br />

influence <strong>on</strong> frost depth when the value of Ah<br />

is in the range of 45 to 75 cm, so that the Mt<br />

values in the Standard TJ7-74 should be revised<br />

and the suggested values are shown in Table V.<br />

TABLE V<br />

The Suggested Values of Mt<br />

tT<br />

Values of Mt at different locati<strong>on</strong>s<br />

Ah (cm)<br />

corners of outside middle secti<strong>on</strong> of<br />

outside wall<br />

5 30 0.85<br />

0.7<br />

-75<br />

1 .o<br />

0.8<br />

>75<br />

1 .o<br />

1 .o<br />

Note: 1) Mt value could be taken by interpolati<strong>on</strong> when<br />

values of Ah are in the range of 30 to 75 cm:<br />

2) Mt values in Table V is available for the<br />

c<strong>on</strong>diti<strong>on</strong> of the indoorfloor directly built <strong>on</strong><br />

the ground surface; (3) The divisi<strong>on</strong> of the<br />

middle secti<strong>on</strong> and the corner is the same as<br />

the descriuti<strong>on</strong> in the remark of Table 19 in

PREDICTION OF PERMAFROST THAWING AROUND MINE WORKINGS<br />

V.Yu. Xzaks<strong>on</strong>l, E.E. Petrovl and A.V.' Samokhinz<br />

1Institute of Mining Engineering of the North, Yakutsk, U.S.S.R.<br />

2Yakutsk State University, Yakutsk, U.S.S.R.<br />

SYNOPEiLS We have derived approximate formulae for predicti<strong>on</strong> of the size of thaw areas<br />

of the mine working walls under the influence of warm air for positive and sign-vaxying thermal<br />

regimes. An analysie is,made of the influence of a variety of factors up<strong>on</strong> thawing dynamica.<br />

The usefulness of heat insulati<strong>on</strong> as applied depending <strong>on</strong> operating c<strong>on</strong>diti<strong>on</strong>8 for woxkinge is<br />

"<br />

ahom<br />

Advantageous ueage and deprign of the eupports<br />

of mine worklnp within the permafroat are imporrslble<br />

unleea thawing dynamic@ of the walls<br />

under the effect OS a warm air i~ predicted.<br />

'Phi8 questi<strong>on</strong> ha0 been addrerrsed by a number of<br />

papere having the aatne dieadvantage in comm<strong>on</strong>,<br />

namely the analyeia waa made for o<strong>on</strong>diti<strong>on</strong>s of<br />

a c<strong>on</strong>atant, poaifive temperatwe of the air in<br />

the mine.<br />

For practiaal puxpoees, howevex, it is the xeaults<br />

for variable temperaturea whi& ar5 required<br />

<strong>on</strong> moat occaei<strong>on</strong>e beoause mine workings<br />

of all underground mining enterprises in the<br />

North-East of the U.S.S.R. operating throughout<br />

the year, are under c<strong>on</strong>diti<strong>on</strong>s of a eignvarying<br />

heat regime.<br />

,Pagers faking account of air temperature fluctuati<strong>on</strong>s<br />

are not numerow and axe, baaically,<br />

o<strong>on</strong>cerned with problem statements. hhgineering<br />

predicti<strong>on</strong> teehniquea (Ieakn<strong>on</strong> and Petxov, 1985)<br />

find a llmited field of applicati<strong>on</strong> and Lack<br />

the am%ly8iS of thawing dynamics for poeitive<br />

and sign-varying heat regimels.<br />

In the preeent paper thie problem will. be solved<br />

by a method of mafhematioal simulati<strong>on</strong> <strong>on</strong><br />

a computer by an algorithm reported a in paper<br />

of Ioaks<strong>on</strong> and Petrov (1986).<br />

The algorithm aolvea muLtifxolst Stephan problems<br />

by the finite differenoe method via automatic<br />

sampling of the amoothing parameter. A<br />

large-scale computer simulati<strong>on</strong> experiment has<br />

been c<strong>on</strong>ducted for the following variati<strong>on</strong>s of<br />

affecting parametera (Table 1).<br />

Mathematleal simulati<strong>on</strong> was carried out in two<br />

stages. The first stage involved selecting<br />

thermal characteristic# of the problem (the<br />

heat exchange coefficient d , the heat c<strong>on</strong>ductivity<br />

and heat capacity coefficients for rock<br />

ground in unfrozen a d frozen c<strong>on</strong>diti<strong>on</strong>s A,,<br />

A,,, , cTp , and C,,,JJ , and moiatuxe c<strong>on</strong>tent<br />

of rook ground 15 ) such a8 to achieve agreement<br />

between calculated and experimental results<br />

obtained under natural c<strong>on</strong>diti<strong>on</strong>s (Dad"<br />

kin et el., 1968) and laboratory experiments<br />

TABLE I<br />

Limits and Steps of Variati<strong>on</strong> of Values<br />

in Mathematical Simulati<strong>on</strong><br />

Parameter<br />

Natural temperature of a<br />

rook maee, To, *C -6 -2 2<br />

Yearly amplitude of air 0 10 2<br />

temperature fluotuati<strong>on</strong>s in<br />

the mine, A, 9 OC<br />

Service time of the<br />

working r , m<strong>on</strong>th6<br />

1 48 0.1<br />

1 240 0.25<br />

3 0.5<br />

Tn the sec<strong>on</strong>d stage of mathematical eimulati<strong>on</strong><br />

the variants were calculated using data in<br />

Table I. The caloulati<strong>on</strong> results were handled<br />

by the method of least aquares, Although for<br />

each variant, we aalculated the entire tempera<br />

ture field, we, nevertheless, investigated the<br />

behaviour of the main parameter of the temperature<br />

field, namely the size of the thaw area<br />

( 5 ), whose boundary was taken to be the<br />

zero isotherm.<br />

The case of heat exchange at c<strong>on</strong>stant, positive<br />

temperature wa~ investigated <strong>on</strong> numerous occaai<strong>on</strong>8.<br />

The beet repreeentati<strong>on</strong> of the dependence<br />

of the depth of thaw <strong>on</strong> the time of heat<br />

exchange is<br />

1397

S<br />

5 = a +segz, (1)<br />

where Z is the service time of the working<br />

(years I.<br />

For each variant, we determined the coefficients<br />

of equati<strong>on</strong> (11, fox each a9 which we<br />

chose a complex argument giving the beat (in<br />

the sense of a minimum of atandard deviati<strong>on</strong>)<br />

representati<strong>on</strong> of the deaeadences of the coef-<br />

ting the dependences of the above arguments<br />

may be characterized as being good (Fig5 1, 2).<br />

Pig.2 The Dependenae 09 the Coefficient 8 ;<br />

Point Numbering Irs the Same as Pig.1.<br />

Fig. 1 The Dependence of the Coefficient<br />

Involved in Equati<strong>on</strong> (11 up<strong>on</strong> Affecting Parameters.<br />

Mathematioal Simulati<strong>on</strong> Data axe<br />

Numbered: 1st Figure tmem, 2nd Figure, I,,<br />

OC 8-2 (I), 6-2 (21, 4-2 (31, 6-4 (41, 6-6<br />

(5), 4-4 (61, 2-2 (7), 4-.6 (81, 2-4 (91, and<br />

2-6 (IO), Points 11-15 are obtained at<br />

P 6OC and<br />

tmean<br />

To = -2OC, for heat reslstanaea<br />

of 0.125; 0.4; 0.9; 1.3; and 1.53<br />

W/(m2 K), respectively.<br />

The variable o f air temperature of the mine was<br />

simulated ueing the relati<strong>on</strong>ship<br />

where 5 is time (m<strong>on</strong>ths), i.e., allowance ia<br />

made <strong>on</strong>ly for the annual cycle of temperature<br />

fluctuati<strong>on</strong>s and the beginning of heat exchange<br />

is accomplished with maximum yearly temperature.<br />

In the aaae of 8 positive heat regime<br />

0, A ~ tmeanl, movement of the<br />

fr<strong>on</strong>t of thaw is proceeding in the same manner<br />

a# depicted in Pig. 3 which aloo ehows the movement<br />

of the fr<strong>on</strong>t of thaw at a c<strong>on</strong>atant temperature<br />

equal to tmea.<br />

The movement ia oacillatoxy in character, i.~.,<br />

the poeiti<strong>on</strong> of the fr<strong>on</strong>t of thaw fluctuates<br />

1398<br />

1 2 4 z, ysazs<br />

Fig.3 The Movement<br />

-<br />

of the h<strong>on</strong>t of Thaw in<br />

the Case of a Poaitive Heat Regime, OC:<br />

tmeaa 1.6, To -2, At IC 0(1), 6 (2).<br />

The movement is oscillatory in oharaater, i.e.,<br />

the poaitl<strong>on</strong> of the fr<strong>on</strong>t of,thaw fluctuatee<br />

about a positi<strong>on</strong> defined by equati<strong>on</strong> (I). POXlowing<br />

4 ox 5 cycles, the movement becornerr a<br />

stati<strong>on</strong>ary <strong>on</strong>e, ulaatfng toward the amallex<br />

side by 5 to 8% fthe smaller is the yearly amplitude<br />

of air tempexatwe fluctuati<strong>on</strong>s, the<br />

smaller i8 the deviati<strong>on</strong>). Ignoring thie, the<br />

8ir;e of the area of thaw at a variable, poeifive<br />

air temperature in the mine oan be predicted<br />

using equati<strong>on</strong> (1).<br />

In the case of B eign-varying heat reerne of<br />

the air inside the working, thawing aJmamies<br />

are different for negative and posltive yearly<br />

mean temperatures. When tmem Q OOC, the movement<br />

of the fr<strong>on</strong>t of thaw is pulsating in<br />

character (Pig. 4).<br />

Por predicti<strong>on</strong> purpoesa &a regaxde the greateat<br />

size of the area of thaw, for ~ > l year, WB<br />

obtained the equati<strong>on</strong>

dynamics are more oomplicated, Let UB denote<br />

by z* the time before which the c<strong>on</strong>diti<strong>on</strong><br />

emax e is satisfied, where 5 is the depth<br />

of thaw at c<strong>on</strong>stant temperature (tmean). It ia<br />

evident that, when ZSZ*, the thawing is pulsating<br />

in character, with the depth of thaw<br />

incrkasing from year to year and becoming atable<br />

when z = z" .<br />

1 2<br />

1<br />

t,p+At+2<br />

1,256 + 2.01 Ea<br />

~t,p-8J(10R,+1)0'75<br />

(2)<br />

Within this time range, as the amplitude 3f<br />

yearly air temperature fluctuati<strong>on</strong>s grow^, the<br />

depth of thaw increares as well.<br />

For z rZ*, this relati<strong>on</strong>ship is valid <strong>on</strong>ly<br />

for large amplituder (At). If (At - lies<br />

within the interval 0.5 - 2.5O (the Interval<br />

becoming shorter with a decrease of the paratCP<br />

1, then thawing dynamics<br />

T0-1,8i(Ru+1)<br />

show an'unwual behaviour (curve 3 in Pig, 6).<br />

ati<strong>on</strong> between equati<strong>on</strong> (2)<br />

dati<strong>on</strong> results ils shown<br />

~ig.6 The Movement of the Fr<strong>on</strong>ts of 'Phew in<br />

the Case of a Sign-Varying Heat Regime and<br />

Positive, Yearly Mean Temperature, OCI<br />

4, ICo -4, At 10 (11, 8 (21, 6<br />

(31, 0 (4).<br />

Fig.5 !Che Dependenoe of the Maximum Depth of<br />

Thaw up<strong>on</strong> Affecting Fdors (tmem 0,<br />

At 1 I tmean( 1. Mathematical Simulati<strong>on</strong> Data<br />

are Numbered (1st Figure fmean, 2nd Figwe<br />

The outer fr<strong>on</strong>t of phaae tranaiti<strong>on</strong> that is situated<br />

farther from the working c<strong>on</strong>tour, displaces<br />

according to the relati<strong>on</strong>ahip repreaenxima<br />

and,minima grows with the time remaining,<br />

ted by a harm<strong>on</strong>io curve, whose ordinate of mahowever,<br />

amallex than the depth to which the<br />

maad would thaw out, provided that the temperature<br />

is c<strong>on</strong>stant.<br />

The inner fr<strong>on</strong>t of phaae transitl<strong>on</strong>s appears<br />

during a 'cold' period of air temperature and,<br />

<strong>on</strong> Borne ooca~li<strong>on</strong>s, doem not make c<strong>on</strong>tact with<br />

the outer fr<strong>on</strong>t (Big. 6).<br />

For predicti<strong>on</strong> purposes as regarda the greatest<br />

depth o f thaw, for 't; r, z' , we obtained<br />

the equati<strong>on</strong><br />

At poeitive, yearly mean temperature, thawing<br />

1399

this dependence is illustrat ed<br />

3 I I<br />

OhA<br />

I<br />

'0<br />

e I1<br />

0'2<br />

a '3<br />

4 '4<br />

+ '6<br />

Fig.7 The Dependence of the Maximum Depth<br />

of Thaw up<strong>on</strong> Affecting Dactors (emean 7 0,<br />

At 7 t ,) .. Point Numbering ia the Same as<br />

Fig. 1.<br />

In order to calculate the value of z*, we may<br />

take advantage of the formula<br />

'<br />

den .ce for a involves th e value 09 thermal resistance<br />

to the 3rd power. C<strong>on</strong>sequently, heat<br />

insulati<strong>on</strong> effectively delaya the <strong>on</strong>set of thawing<br />

and influences, to the same extent, the<br />

displacement apeed of the fr<strong>on</strong>t of thaw during<br />

a prol<strong>on</strong>ged acti<strong>on</strong> of the warm air.<br />

On the c<strong>on</strong>trary, in the caee of a sign-varying<br />

temperature regime, heat ineulati<strong>on</strong> effectively<br />

reduces the depth of thaw at prol<strong>on</strong>ged service<br />

times of the working and bsla little effect during<br />

the first years because a high maximum temperature<br />

of the cycle come@ into play.<br />

Xn the case 04 sign-varying cycleis the depth<br />

of thaw can be predioted with a xeeerve using<br />

formulae (2) and (3); however, with cycle8 with<br />

a positive, yearly mean temperature and short<br />

service times, the remne may turn out to be<br />

c<strong>on</strong>aidersble as well since formula (3) gives<br />

a value of z 32 * , and z* , at small. valuels ,<br />

During the firet year of 'eervioe, thawing dynamics<br />

dependa eubetantially up<strong>on</strong> the <strong>on</strong>set time<br />

of exploitati<strong>on</strong>, i.e., <strong>on</strong> the period (win,<br />

ter, summer, tapring, or autumn) Buring which<br />

the working is driven, During the sec<strong>on</strong>d year<br />

and later <strong>on</strong>, this influence relaxerr becoming<br />

of no signiflosnce. Pig, 8 givea example plots<br />

of thawing for four variant8 of the temperature<br />

regime. The type of acheme for air temperature<br />

variati<strong>on</strong> ia achematically represented by<br />

a circle aiagram. A processing of the'reaulte<br />

dQrived from a mass computer experiment made it<br />

posaible to obtain empirical formulae fox the<br />

maximum relative depth of thaw during the first<br />

year of exploitati<strong>on</strong><br />

where emaria determined by the expressi<strong>on</strong> (31,<br />

and the coefficients a and 8 are determined<br />

in Figs 1 and 2.<br />

Let us analyze the remlts obtained. To begin The coefficients B and C are given In Table XI.<br />

with, it rshould be noted that the widely accepted<br />

pobt of view about the equivalence of the<br />

effectB of a sign-varying cycle and the air<br />

temperature c<strong>on</strong>atant equal to tmem, is mislea-<br />

TABU 11<br />

ding. The depth of thaw in the firs3 cam is<br />

The<br />

able to be both Larger (when z<br />

Coefficienfa Involved in the<br />

c 2: and<br />

smaller (when >z") as compared with the<br />

Expressi<strong>on</strong> (1) as a Functi<strong>on</strong> of<br />

sec<strong>on</strong>d<br />

the Onset Time of Exploitati<strong>on</strong><br />

ease.<br />

of the Working<br />

In the case of a positive temperature regime<br />

".. . . ..- . .-. .<br />

and sign-varying temperature, but At - tmeU<br />

NO.<br />

5 2.5, the depth of thaw can be predicted<br />

Variant<br />

Correlati<strong>on</strong> ratio<br />

(Fig981<br />

of the dependence<br />

using formula (1) which may be transformed<br />

thus t<br />

1 a 0,5869 0,6017 0,9928<br />

2 b 0.8117 0.9037 0.9963<br />

3 c 0.6154 0,6850 0.- 9924<br />

4 d 0,7846 0.8734 0.9975<br />

where &C = - + 1s the time of thawing <strong>on</strong>-<br />

set after the warm air has affected the working<br />

walls. Note that heat ineulati<strong>on</strong> of the<br />

working walls has a largerinfluence up<strong>on</strong> the<br />

magnitude of tha coefficient a (and hence<br />

up<strong>on</strong> Z, ) than up<strong>on</strong> the coefficient 8 in<br />

-equati<strong>on</strong>(1) because the argument of the depen-<br />

1400<br />

The relati<strong>on</strong>ship (5) is characterized by a very<br />

high closeness of relati<strong>on</strong> because the correlati<strong>on</strong><br />

ratios are close to unity.

a<br />

2 6 1D 14 18 Z, mcnt hs<br />

6 i4 18 Z,m<strong>on</strong>ths<br />

C<br />

2 6 io i4 I’8 G, m<strong>on</strong>ths<br />

Fig.8 Examplea of the Time Dependence of the Depth of Thaw for<br />

tmean<br />

= 4qC, To = -4OC. The Amplitude of Yearly Air Temperature<br />

Fluatuati<strong>on</strong>s: 2O (I), 4O (21, 60 (3), 8 O (41, 100 (5).<br />

A maximum value is reached at different times<br />

with relspect to the beginning of exploitati<strong>on</strong><br />

of the working (Table TSI).<br />

No. Variant<br />

(Pig.8)<br />

TABLE I31<br />

Onset Times of Maximum Thaw<br />

with Respect to the Beginning<br />

of Rrploitati<strong>on</strong> (M<strong>on</strong>ths)<br />

First<br />

maximum<br />

1 a 3.1<br />

2 b 12.6<br />

3 C<br />

9.3<br />

4 d<br />

6.5<br />

By analyzing the result8 obtained,<br />

to draw the following c<strong>on</strong>clusi<strong>on</strong>s.<br />

Sec<strong>on</strong>d<br />

maximum<br />

15.1<br />

24.6<br />

21 -3<br />

18.5<br />

we are led<br />

1. Phe <strong>on</strong>aet time of heat exchange influences<br />

<strong>on</strong>ly the intenaity of the first cycle of thawing<br />

and does almoat not affect the aimultaaeity<br />

of the thawin and the air temperature variati<strong>on</strong><br />

(Table IIIf . The time delay of: the thawing<br />

with respect to the air temperature varia-<br />

1401<br />

ti<strong>on</strong> ranges erom 10 to 20 days and seeme to<br />

be of no practical c<strong>on</strong>aern.<br />

2. The apparently unusual. minimum of the depth<br />

of thaw for variant (a) is accounted for by<br />

the fact that the period of positive air temperature<br />

rmp<strong>on</strong>sible for the first cycle of<br />

thawing is exceedingly short.<br />

3. For the fir& year of exploitati<strong>on</strong> of the<br />

working, heat insulati<strong>on</strong> is a powerful remedy<br />

for the thawing - it can be avoided uaing heat<br />

insulati<strong>on</strong> with a thermal reaistance 3 .4<br />

m:K/W, which corresp<strong>on</strong>da to 15.....20 om<br />

thickness of foam plastic, for example.<br />

4. The natural temperature effect of xocko ie<br />

not as significant in the range studied - as<br />

To varies from -6O to -2O, the relative depth<br />

of thaw increases by 30$.<br />

5. The results presented here may be useful for<br />

predicti<strong>on</strong> purposes a8 regarde the depth of<br />

thaw in the walls and the roof of the workings,<br />

as well as deciding up<strong>on</strong> the use of heat insulati<strong>on</strong><br />

and choosing temperature regime parameters<br />

of exploitati<strong>on</strong> of the workingrs.

REFERENCES<br />

Dyad’kin, Yu.D. Zilberbrod, A.F., and Chaban,<br />

P.D. (1968). Teplovoi rezhim ruanykh,<br />

ugolnykh i rossypnykh ahakhf Severa, M<strong>on</strong>cow:<br />

Nauka.<br />

leaks<strong>on</strong>, V.Yu. and Petrov, E.E. (19851. Inzhenerny<br />

metod prognozirovaniya i regulirovaniya<br />

razmerov oreolov protaivsnipa<br />

vokrug gornykh vyrabotok oblaeti mnogolatnei<br />

merzloty, No. 5, FTPRPI.<br />

Izaks<strong>on</strong>, V.Yu. and Petrov, E.E. (1986). Chislennye<br />

metody prognosirovaniya i regulirovaniya<br />

teplovogo rezhirna &ornykh pOrOd<br />

oblasti mnogoletnei mer5loty, YakufPk:<br />

Tad. Yap so AN SSSR.<br />

1402

EXPERIENCE IN CONSTRUCTION BY STABILIZATION METHOD<br />

L.N. Khrustalevl and V,V. Nikiforovz<br />

1Laboratory of Engineering Geocryology, Faculty of Geology, Moscow State University<br />

Z<strong>Research</strong> Institute of Bases and Underground Structures, Moscow, USSR<br />

6YNOpsIS<br />

The paper presents a new method for building foundati<strong>on</strong>s <strong>on</strong> perennially fro-<br />

2- grounds al<strong>on</strong>g with the assessment of the field of its possible applicati<strong>on</strong>. 8tructural and<br />

technological designs of baaee, foundati<strong>on</strong>s and coaling systems are described and the data obtained<br />

in the course of observati<strong>on</strong>s of the buildbgs built bg tbja method are analyzed.<br />

In permafrost regi<strong>on</strong>s all the areas under<br />

c<strong>on</strong>atructi<strong>on</strong> can be divided into two groups:<br />

area8 with c<strong>on</strong>thuoua or disc<strong>on</strong>tinuous perennially<br />

frozen grounds.<br />

The former 'are most simple for development.<br />

Hence, the first principle of using gmunda as<br />

a bass ia applied here: foundati<strong>on</strong>s are built<br />

in the permafrost; ventilated vaults or oljher<br />

cooling sygtems being arranged under a building.<br />

These systems help maintain a frozen<br />

state of the ground under buildings over the<br />

whole period of exploitati<strong>on</strong>.<br />

The Latter are more complicated, since they require<br />

preliminarg freezing or thawing of *he<br />

permafrost to prepare a base for c<strong>on</strong>structi<strong>on</strong>.<br />

Preliminary freezing artificially creates the<br />

c<strong>on</strong>diti<strong>on</strong>s characteristic of the first group<br />

of areas, and then the ground or the base is<br />

used according to the first principle. The<br />

preliminary thawing creates c<strong>on</strong>diti<strong>on</strong>s under<br />

which a further thawing of perennially frozen<br />

grounds under the acti<strong>on</strong> of heat generated by<br />

a building will not result ia abnormal settlement<br />

of the foundati<strong>on</strong>6 during the entire period<br />

of exploitati<strong>on</strong>.<br />

At preaent, a more ec<strong>on</strong>omical way of c<strong>on</strong>structhg<br />

<strong>on</strong> permafrost of disc<strong>on</strong>tinuous type has<br />

been develo ed which envisages Eitabilizatiw<br />

of the initfel permafrost table over the whole<br />

period of a buildhg exploitati<strong>on</strong>. The idea<br />

of such a stabilizati<strong>on</strong> was proposed and protected<br />

by the authora' certificate granted to<br />

G.V.Porkhaev, L.N .Kkrustalev, V.N.Yeroahenko<br />

and others (Avtorskoe svidetelstvo.. . , 1975).<br />

The method of stabilizati<strong>on</strong> is applied at<br />

c<strong>on</strong>structi<strong>on</strong> sites where the layer of seas<strong>on</strong>al<br />

PreezFng and thawing do- not merge with the<br />

permafrost fully O r partially withln the area<br />

of a building, and the perennially frozen<br />

grounds are characterized by a c<strong>on</strong>siderable<br />

compressibility at thawing, and the overlying<br />

thawed grounds possess heavFng properties during<br />

freezing.<br />

The method Lnvolves maintenance of the initially<br />

prescribed permafrost table over the whole<br />

period of e%ploitati<strong>on</strong>.with the help of a vent'iiated<br />

vault arranged under the building. '<br />

The bottom of the foundatlane is located ia<br />

the layer of unfrozen ground between the per<br />

mafroat table and the bottom of a seasanally<br />

or perennially frozen layerr<br />

A mean alr-Bempexature close to zero is maintained<br />

in the vault for the whole period of<br />

exploitati<strong>on</strong> to exclude the heat influeme of<br />

a building <strong>on</strong> the underlying permafroat. In<br />

that case, the depth of seas<strong>on</strong>al or perennial<br />

ground freezing under thq building beoomes<br />

equal to that of seas<strong>on</strong>al OT perennial thawing,<br />

producing a phase bouuaarg of the stable maiatenanae<br />

.of freezing temperature above the<br />

foundati<strong>on</strong> bottom the year round. The sec<strong>on</strong>d<br />

phase boundary ia located at the tog of the<br />

permafrost, and a, layer 00 unOroeen ground<br />

the "buffer layer",. whoee temperature grad€ents<br />

are equal 'practically to aero, a d so,<br />

c<strong>on</strong>sequently am the heat fluxes passing<br />

through it,:ia looated between the pWe boundaries.<br />

The buffer layer semw a8 a heattight<br />

curtain ensuring stabilizati<strong>on</strong> of the<br />

initial permafrost table and protecting the<br />

,unfrozen ground Prom perennial freezinng. The<br />

base of a building being protected f mm perennial<br />

freezing and thawhg does not deform<br />

Fn the proce~s of exploitati<strong>on</strong> which ensures<br />

ita stability .<br />

In the c<strong>on</strong>structi<strong>on</strong> and exploitati<strong>on</strong> of building5<br />

by the method of Beabilizati<strong>on</strong> the following<br />

two modes of ventilated vaults operati<strong>on</strong>:<br />

variable ana permanent are possible.<br />

The variable mode involves regulati<strong>on</strong> of he&<br />

Fnteracti<strong>on</strong> between a building and its base in<br />

the process of exploitati<strong>on</strong>.and is aimed primarily<br />

at creating a special mode of the ventilated<br />

vault operati<strong>on</strong>. It c<strong>on</strong>siste in maiatafninsg<br />

10-15 year periods of negative mean<br />

annual air temperature alternating with 2-5<br />

year <strong>on</strong>es of positive mean annual ais temperature<br />

Fn the vault.<br />

Perennial freezing of round wcurs ba the<br />

vault during the perio ! 09 negative air tampsrature.<br />

The modulus OP the vault ventilati<strong>on</strong><br />

1403

for that eriod is calculated BO that the The calculati<strong>on</strong> is based <strong>on</strong> the method of the<br />

mean annuaf air temperature h the vault, ta- worst case. The essence of this method! as<br />

k u into account probable deviati<strong>on</strong>s from the applied to the problem under c<strong>on</strong>aideratl<strong>on</strong>,ia<br />

estimated values, should a fortiori be negati- as follows.<br />

ve. The depth of perennial freezing at the baae<br />

of a building is limited by the c<strong>on</strong>diti<strong>on</strong> of 'pwo c<strong>on</strong>diti<strong>on</strong>al cross-sectioaa are chosen Fn<br />

the fouudati<strong>on</strong> stability against the acti<strong>on</strong> of the base of a building to calculate the depths<br />

heaving forces. Up<strong>on</strong> reaching such a depth, of perennial freezing and thawing for the<br />

the perennial freeslag is stopped by changing whole period of exploitati<strong>on</strong>. The calculati<strong>on</strong><br />

the air temperature in the vault from negative is pexforrned for probable deviati<strong>on</strong>s of mean<br />

to positive.<br />

annual tempesatures of the ground Surface in<br />

the ventilated vault and outside the building<br />

The resultant perennially $rozen ground layer from the mean values. In <strong>on</strong>e of the crossthawa<br />

out during the period of positive air secti<strong>on</strong>s these temperatures are to be maximum,<br />

temperature in the vault, and the initial c<strong>on</strong>- taking into account their probable deviati<strong>on</strong>s.<br />

diti<strong>on</strong>s are restored ~JI the barse of a butldbg. The depth of perennial thawinng of the under-<br />

Thla cycle recurs.<br />

lying permafrost and the resultant settlement<br />

of the base and foundati<strong>on</strong>s are calculated for<br />

The operatt<strong>on</strong> mode of a ventilated vault is this cross-secti<strong>on</strong>. From the c<strong>on</strong>diti<strong>on</strong>, Limichanged<br />

by opening and closin vantilati<strong>on</strong> ope- ting the settlement, the thickness of the pr<strong>on</strong>hngs.<br />

Paxameters of the vauft. design am tective mrozen ground layer is determined.<br />

assigned by calculati<strong>on</strong>s to ensum a positive In the other secti<strong>on</strong>, the mean annual temperamean<br />

annual air temperature with cl.osed venti- tures of the ground surface Fn the ventilated<br />

lati<strong>on</strong> openings not less than the absolute - vault and outside the building, taking into<br />

value of the ambient mean annual air tempera- account their possible deviati<strong>on</strong>s, are assumed<br />

ture in the regi<strong>on</strong>. This ensures a complete as minbum. In this cross-secti<strong>on</strong> the depth<br />

thawbing of the short-term permafrost that forme of perennial freez'ing of the thawed layer<br />

during the period. of negative mean annual. air around. the foundati<strong>on</strong>s is calculated. Proceedtemperature<br />

in the ;vault at, any temperature of Fng from the necessity of maintaining the stathe<br />

ground surface out'aiae '%he c<strong>on</strong>tourof the bility of foundati<strong>on</strong>s inthis cross-secti<strong>on</strong><br />

buildhg.<br />

fmm the aati<strong>on</strong> of tangential heaving forces<br />

in the course of perennial. freezkg, <strong>on</strong>e has<br />

The alternati<strong>on</strong> of c<strong>on</strong>trol periods Lf carried to determine their depth as well as permissible<br />

out baaed <strong>on</strong> the result6 of temperature measu- depth of perennial freezing of the mfrozen<br />

rements 'in- the base of the building In speoial ground layer. In such a way, the thiclmess of<br />

thermometric boreholes. Such meaaurements are the protective thawed Layer, the depth of. founmade,<br />

<strong>on</strong>ce B year to detemhe the actual depth datiOnS, and the admissible depth of perennial<br />

of pezennial freezing or thawing in the upper freezing at the base both st permanent and valayer<br />

over the entire area of the building so riable modes of the ventilated vault operati<strong>on</strong><br />

as to -make 8 decisi<strong>on</strong> <strong>on</strong> the alternati<strong>on</strong> of are determined.<br />

c<strong>on</strong>tml .periods.<br />

The parameters of the ven*ilated vault; aesim<br />

In applying the stabilizati<strong>on</strong> method, a perma- (thermal resistance of the floor and enclosing<br />

nent mode of the ventilated, vault bperatl<strong>on</strong> Is structures, as well as the total area of venalso<br />

possible. It is a,$articul.ar came of the tilati<strong>on</strong> openhings) are specified from the f 01-<br />

variable mode when <strong>on</strong>e of the periods lasts for lowing c<strong>on</strong>siderati<strong>on</strong>s.<br />

the whole term of exploitati<strong>on</strong> of a building.<br />

An average mean annual air temperature bh the Under the permanent mode of a ventilated vault<br />

vault is aaaigned to be- al<strong>on</strong>e .t O°C (-0.5 to operati<strong>on</strong> these parameters axe detembed by<br />

+2 .oca)<br />

calculated man annual temperature of the<br />

ground surface beneath the building which is<br />

A method has been devised to calculate the main a result of the calculati<strong>on</strong> and the limitati<strong>on</strong><br />

parametera of the base when c<strong>on</strong>structi<strong>on</strong> is of the perennial freezing of the unfrozen<br />

effected by the stabilizati<strong>on</strong> method. It- b- ground layer Fn the bamr<br />

plies' calculati<strong>on</strong> and rjipecjficati<strong>on</strong> of the followhng<br />

characteristics needed to desiga 8 buil- Under the variable mode of operati<strong>on</strong> of a vending:<br />

tilated vault, its design parameters ark determined<br />

80 aa to ensure the desired calculated<br />

(11 depth of foundati<strong>on</strong> and its carrying meen annual temperature of the ground surface<br />

capacity ;<br />

under a building during warm and cold periods<br />

(2) depthe of the admissible perennial of exploitat i<strong>on</strong>.<br />

freezing of grounds at the base;<br />

The distance between the ranges of the m<strong>on</strong>itor-<br />

(3) .- resistance to the heat transfer of the ha thermometric boreholes under both modes of<br />

floor over the ventilated vault end operati<strong>on</strong> is specified by a special calculati<strong>on</strong><br />

structures which surround iti;<br />

depending 011 the width of the building, the in-<br />

(4) areas of the vault ventilati<strong>on</strong> ope- homogeneity of the thermal reglmme 5n the vault,<br />

nings ; the admissible depth of perennial freeaing-,and<br />

accuracy of ground temperature measurements in<br />

(5) thiclmess of the protective unfrozen the boreholes.<br />

mound - laser over the aermafmostr<br />

(61 distance between the ranges of m<strong>on</strong>i- Thfs calculati<strong>on</strong> method of the main parameters<br />

toring thermometric boreholes.<br />

of a base is described Sn detail in the recommendati<strong>on</strong>s<br />

<strong>on</strong> the applicati<strong>on</strong> of the stabllisat<br />

i<strong>on</strong> method (Khrustalev and N ikiforov , 1985).<br />

1404

At present, more than 30 appartment houses and<br />

public buildhgs have been built and ~uccessfully<br />

exploited in the northern Euhpean UBSR<br />

by the stabilizati<strong>on</strong> method. Many of them<br />

were put into operati<strong>on</strong> over IO yeam ago.<br />

Therefore, to-day we can analyse the experience<br />

ga'ined in the course of their c<strong>on</strong>structi<strong>on</strong> and<br />

exploitati<strong>on</strong> by this method.<br />

The advantages of the stabilizati<strong>on</strong> method can<br />

be appreciated <strong>on</strong> the example of a residential<br />

micro-re i<strong>on</strong> (neighborhood housing unit) built<br />

in 1975-88.<br />

Its geology is represented by deluvial and<br />

upper-morainic 0.5-5.0 m-thick lams overlying<br />

fluvioglacial d osits with a frequent bterbeading<br />

of loams ,oamy sands, coarse and finerained<br />

sands, and gravelly deposita with Band<br />

ill and some boulders.<br />

B<br />

The permafrost in this micro-regi<strong>on</strong> is characterized<br />

by great diversity and complexity. The<br />

sites of c<strong>on</strong>tlnuous permafrost occupy about<br />

108, those of ahallow permafrost (less than 10-<br />

12 m) about 30%, and of deep pexmafrost (more<br />

than 12 m) ab0 ut 60% of the area. The upper<br />

ground layer In the micro-regi<strong>on</strong> is diatb uished<br />

by a greater thicbess of the seae<strong>on</strong>ah<br />

frozen lager which reaches 2.5-3.0 m. In<br />

additi<strong>on</strong>, llpereletokslv (short-term permafrost<br />

extendjng down to.6-7 rn) frequently occur here,<br />

covering more than a half of the area.<br />

Due to the fact that the, permafrost in this<br />

micro-regi<strong>on</strong> is of disc<strong>on</strong>tinuous type, the temperature<br />

at the depth of mnuaL aero amplitudes<br />

is close to OOC.<br />

Loams in the upper layer of the geological Beeti<strong>on</strong><br />

are subject to heavhg during freezing.<br />

Perennially frozen fluvi.oglaciLa1 deposits axe<br />

characterized by c<strong>on</strong>siderable shrinkage durin<br />

thawing (over 5 cm/m). Ln this c<strong>on</strong>necti<strong>on</strong>, if<br />

was decided to apply the method of stabilizati<strong>on</strong><br />

when developing this micro-regi<strong>on</strong>.<br />

Twenty s3x five-storied * large-panel appartment<br />

houses and public buildinLngs2with a total general<br />

useful. area of 69,109 m have been built<br />

h this micro-regi<strong>on</strong>. Fricti<strong>on</strong> piles, driven<br />

to a depth of 8-12 m, with a high foundati<strong>on</strong><br />

mat were used as foundati<strong>on</strong>. Ventilated vaults<br />

were c<strong>on</strong>structed beneath all the buildings of<br />

the micro-regi<strong>on</strong>. All sanitary engbneering<br />

networks were c<strong>on</strong>centrated in the technical<br />

floor8 which w m located between the ventilated<br />

vault and the ground floor.<br />

The stabiliaati<strong>on</strong> method made it possible to<br />

minbize the preliminary preparatibn of the<br />

bases. The amount of preliminary thawing la<br />

the entire micro-re i<strong>on</strong> amounted to 36 thou. m, 3<br />

versus 1445 thou, m s envisaged by the sec<strong>on</strong>d<br />

principle of c<strong>on</strong>structi<strong>on</strong>. Pile foundati<strong>on</strong>s<br />

and c<strong>on</strong>siderable reducti<strong>on</strong> of the volume of<br />

preliminary thawing and excavati<strong>on</strong> work allowed<br />

us to Fndustrialize the basement erecti<strong>on</strong> and<br />

to reduce the durati<strong>on</strong> of c<strong>on</strong>structi<strong>on</strong> by +4<br />

m<strong>on</strong>ths.<br />

At all atages of designing and c<strong>on</strong>structi<strong>on</strong>,<br />

the problem8 involved in town planning were<br />

Bolved jointly. Attenti<strong>on</strong> was focuased <strong>on</strong><br />

laying sanitary-engineering communicati<strong>on</strong>s<br />

withfn the micro-regi<strong>on</strong> and <strong>on</strong> their inletoutlets<br />

in the buildings. This was accomplished<br />

by the same stabilizati<strong>on</strong> method usin<br />

ventilated chaxzaels. Ground ror the terra%<br />

levelbg was transported from the outsiae. An<br />

efficient drainage ,was envisaged In the ventilated<br />

vaults to prevent flood and break-down<br />

water from penetrating ink0 the ground. A11<br />

these measurea, oompletely ' prevented penetrati<strong>on</strong><br />

of heat from buildlngs and engineering communicati<strong>on</strong>s<br />

into the ground.<br />

The stab'ilisati<strong>on</strong> method permitts free planniag<br />

of housing c<strong>on</strong>structi<strong>on</strong>. 'Phis has enabled to<br />

employ modern architectural Uesigas. The<br />

three-dimensi<strong>on</strong>al unificati<strong>on</strong> of residential<br />

groups adopted In the rojeet made it poseible<br />

to use the' Pmnt row os buildings 88 protecti<strong>on</strong><br />

from wind and mow and thereDy to increase comfort<br />

within the ilntrablock areas and density<br />

of c<strong>on</strong>structi<strong>on</strong>, ma to rt~~ce the length 09<br />

roads and underground smi*ary-engineerSng<br />

networks.<br />

AI1 measures menti<strong>on</strong>ed above have led to a<br />

c<strong>on</strong>siderable increase In the level of comfort<br />

Is that area. The cost of houshng c<strong>on</strong>struc- '<br />

ti<strong>on</strong> in this micro-regi<strong>on</strong> has proved to be<br />

smaller than in the neighboring <strong>on</strong>es where<br />

other c<strong>on</strong>structi<strong>on</strong> methode were applied. The<br />

estimates show that the stabilizati<strong>on</strong> method<br />

employment had decreased the cost of c<strong>on</strong>atruoti<strong>on</strong><br />

of 1 m2 of useful area by 121.6 ma '19-7<br />

rouble8 aa compared with Principle 11, baaed<br />

<strong>on</strong> prelhintnay thawing, and Principle I,usfng<br />

preliminary freesing, respectively.<br />

The status of the bases of buildings has been<br />

m<strong>on</strong>itored since 1976 fWm the moment when the<br />

first of them were put Ynto exploitati<strong>on</strong> in<br />

thia micro-regi<strong>on</strong>. The results of ObsemjPg<br />

the bases of three buildinge are given below<br />

by wag of example.<br />

The measurements involve air temperakure regime<br />

in the ventilated vwltB, ground temperature<br />

regime in the bases of buildings, and the fomdati<strong>on</strong><br />

aettlement .<br />

Results of stati<strong>on</strong>ary ibaervati<strong>on</strong>e of air temperature<br />

in tne ventilated vaults of the three<br />

buildings in 1977-I981 show that average l<strong>on</strong>gterm<br />

values of this temperature are close to<br />

O°C and are - IoC in building I, O*C in bullding<br />

2, and O°C in building 3. The negative<br />

air temperature in the vault of buildin I 0852<br />

be explainea by the increase of its socfe<br />

height as compared with the projected <strong>on</strong>e. The<br />

obeervati<strong>on</strong>s have also shown that In the ventilated<br />

vaults of these buildings. there waB an<br />

inhomogeneity of mean annual air temperature<br />

which occurred <strong>on</strong>ly al<strong>on</strong>g the length of the<br />

vaults was random. Fn character and its value<br />

did no4 exceed 1OC.<br />

, ,<br />

Ground temperature regime ob$ervatinns in the<br />

bases of three buildings show that a perennially<br />

frozen 3-5 m-thick lager formed and stabilized<br />

aver the ten-yoar period of expJoLtati<strong>on</strong>.<br />

Beneath the buildings, this layer is &tdarlain<br />

by unfrozen ground w.herein temperature gradients<br />

practicalJy equal zero. The thawing of<br />

the underlying pemafros$ in .the bases .of the<br />

buildings has not been noted.. 'Phi8 is indirsctly<br />

evidenced by the small values of settlement<br />

1405

of the buildings under c<strong>on</strong>siderati<strong>on</strong> not<br />

exceeding 5 cm for the period surveyed.<br />

In additi<strong>on</strong> to the stati<strong>on</strong>ary observati<strong>on</strong>s<br />

described, numerous urgent measurements of air<br />

temperature in the ventilated vaults and ground<br />

temperature in the bases 00 the majority of<br />

buildin s in the micra-regi<strong>on</strong> were made during<br />

,9764986. Besides, measurmente of the eettlement<br />

of all the bui1ding.s were made'<strong>on</strong> a reglrlar<br />

basis.<br />

The .studies show that <strong>on</strong> the whole the air temperature<br />

regime in the ventilated vaults and<br />

grounds of the bases of theJbuildjng6 corresp<strong>on</strong>ds<br />

to the estimated <strong>on</strong>e. The mean annual<br />

air temperature jn the ventilated vaults, depending<br />

<strong>on</strong> the mean annual ambient air temperature<br />

over the perioa surveyed,. ranged Prom<br />

-1.0 to Y.5OC. The data obtained from practically<br />

all the thermometric boreholes indicate<br />

that a thawed-out protective layer with zero<br />

temperature and zero temperature gradients has<br />

formed in the bases. This layer is located<br />

between the bottom of seas<strong>on</strong>al or perennial<br />

freezing and the permafrost table. The thawing<br />

of the underlyhg permafrost ha6 not been revealed<br />

from the data obtained in the thermometric<br />

boreholes. Perennial freezing was obaexved in<br />

the base8 of some of the buildings at the beginnhng<br />

of exploitati<strong>on</strong>. Its depth has already<br />

stabilized and does not exceed 5 m.<br />

The absence of the underlying permafrost thawing<br />

and the superadmissible perennial freezing of<br />

mmds a% the foundati<strong>on</strong>s is c<strong>on</strong>firmed by the<br />

fi ouudati<strong>on</strong>s leveling. For the period of bvestigati<strong>on</strong>e<br />

the settlemen% of all the buildings<br />

in this micra-regi<strong>on</strong> has not exceeded<br />

6 cm (the maximum admissible value being 15<br />

om)<br />

Thus, the ten-year successful. exploitati<strong>on</strong> of<br />

the buildings in this micro-regi<strong>on</strong> has dem<strong>on</strong>strated<br />

the reliability of the stabilizati<strong>on</strong><br />

method and the validity of theoretical noti<strong>on</strong>s<br />

<strong>on</strong> which the menti<strong>on</strong>ed method is based.<br />

RFFERENCES<br />

Avtorskoe svidetelstvo 480803 MK12E 02 a 27/32<br />

('1975). Zdanie voevodimoe na vechnomerzlykh<br />

gruntalch (G.V. Porkhaev, L.N. -ustalev,<br />

V.N. Yeroshenko i dr. (SSSR)<br />

(Otkrytiya, Izobreteniya), N 30,str.W.<br />

Khrustalev , L.N. & NikWorov V.V. (I 985)<br />

Rekomendatsii PO psimeneniyu sposobov<br />

stabilizataii vechnomerzlykh gruntov v<br />

osnovanii zdmiy, u str. Moskva: NII<br />

osnovaniy .<br />

1406

GEOCRYOLOGICAL STUDIES FOR RAILWAY CONSTRUCTION<br />

(STATE, PRIMARY TASKS)<br />

V.G. K<strong>on</strong>dratyev, A.A. Korolyev, M.I. Karlinski, E.M.+Tirnopheev and P.N. Lugovoy<br />

Moscow State Design and Survey Institute of Transport C<strong>on</strong>structi<strong>on</strong>, MOSCOW, USSR<br />

SYNOPSIS This report deals with the history of the problem; the experience of the<br />

BaykaLo-Amurakaya Idain Line (BAPJ) and, in particular, icing preventi<strong>on</strong> are analysed here. A<br />

questi<strong>on</strong> is raiaed about fundamental. changes of volumes, c<strong>on</strong>tents and quality of geocryological<br />

studies for railway c<strong>on</strong>structi<strong>on</strong> purpoaee. report The gives characteristic of the object of<br />

inveatigati<strong>on</strong>s and general scheme 09 woxk, covering smveys, deaigning and c<strong>on</strong>structi<strong>on</strong> of<br />

railways in pemlafrost z<strong>on</strong>e. Geocryological problems and ways of their soluti<strong>on</strong> me c<strong>on</strong>sidered<br />

<strong>on</strong> example of a new railway line Derkakhit-Yakutak - <strong>on</strong>e of the BAiJ Northern extensi<strong>on</strong>s.<br />

Ftrst the necessity of clewing up of the &eocryological<br />

c<strong>on</strong>diti<strong>on</strong>s for railway c<strong>on</strong>atrudA<strong>on</strong><br />

appeared 100 years ago, when during survvys of<br />

Trans-Siberian Railway in Zabaykalye and Priamuxye<br />

they came acrom permafrost, which<br />

str<strong>on</strong>gly complicated designing and c<strong>on</strong>structi<strong>on</strong><br />

and later <strong>on</strong> - main line operati<strong>on</strong>. Thun,<br />

Sumgin (1937, p. 41-42) mote, characterizing<br />

200-year his'tory of permafroat investigati<strong>on</strong>:<br />

"The permafrost soil inveatigati<strong>on</strong> has c<strong>on</strong>eiderably<br />

changed and advanced after c<strong>on</strong>sfruc-<br />

ti<strong>on</strong> of the Great :Xberian Railway.. The Pmblern<br />

of permafrost faced UQ in all its magnitude.<br />

It was necessary to give definite anawere<br />

to practical requests... It is c<strong>on</strong>sidered that<br />

<strong>on</strong>ly permanent repair of buildings and structuxes<br />

under deformati<strong>on</strong>s <strong>on</strong> Zabaykalskaya and<br />

Amurskaya railways has already cost the g m -<br />

ment 50 mln. old roubles, not faking into account<br />

losses from driving offence <strong>on</strong> these<br />

xailways". For the first time in Russia ayste-<br />

filled research works <strong>on</strong> investigati<strong>on</strong> of permafrost<br />

regime. A powerful. impulse in the geo<br />

cryology development was observed in the 70-<br />

808, when realizati<strong>on</strong> of the BAi.1 project took<br />

place. This project was elaborated by i;loscow<br />

State Desi@ and Survey Institute (LIoaguipro-<br />

trans) with participati<strong>on</strong> of more than 200 research,<br />

design and survey organizati<strong>on</strong>s. PxacticalLy<br />

all Leading permafrost centres of the<br />

country (institute of .Jerzlotovedeniya, icademy<br />

of Sciences of the USSR, ;:loscow State Uni-'<br />

veraity and etc.) also took part in soluti<strong>on</strong><br />

of the BAi.1 geocryological problems a d a special<br />

secti<strong>on</strong> for coordinati<strong>on</strong> and methodological<br />

management of permafrost inveatigati<strong>on</strong>s of<br />

' different organizati<strong>on</strong> <strong>on</strong> the B&;il was or-ized<br />

in the Counsil of Aarth cryolo,T, Academy<br />

of Sciences of the USSR. ,<br />

The BAL1 is a complicated technogenic complex,<br />

c<strong>on</strong>sisting of roadbed, embanlanents and cuts,<br />

matic studies of permafrost were carried out bridges and tunnels, stati<strong>on</strong>s, settlements,<br />

for grounding of Transsib c<strong>on</strong>structi<strong>on</strong> for tovms, buildings, structures and communicapractical<br />

neecln. The Pkst in the world buil- ti<strong>on</strong>s of different purposes. The length of the<br />

ding <strong>on</strong> permafrost with aired cellar was built main line is 3102 km, it has about 4200 buil<strong>on</strong><br />

the Iclogz<strong>on</strong> stati<strong>on</strong> (Zenzinov, 1986). The dings and structures, including 150 large bridfirst<br />

permafroat stati<strong>on</strong> wm establiahed <strong>on</strong> ges, over 30 hn of tunnels , over 200 stati<strong>on</strong>s,<br />

that railway in Scovordino 1927. in It did a over 20 large settlements; if lies in complilot<br />

for enswance of transport c<strong>on</strong>structi<strong>on</strong> in cated nature c<strong>on</strong>diti<strong>on</strong>s, is characterized by<br />

Siberia as well as for development of permn- inclement climate, mainly by mountain relief,<br />

frost studies as a whole. In general, railway various geological structure , permafrost and<br />

c<strong>on</strong>structi<strong>on</strong> in Siberia, Canada, <strong>on</strong> Alaska and high seismic activity of sepaxate route secin<br />

China stimulRted development of many prob- ti<strong>on</strong>s. By the beginning of rnilway c<strong>on</strong>structim<br />

lems of ermafrost studies (Lvov, 1916; Tisa- the degree of studying of natural c<strong>on</strong>diti<strong>on</strong>s<br />

rev and gatskiy, 1994; Bykov and Ilapterev, turned out to be uneven. Some factors, such as<br />

1940; Suhodolskiy, 1945; Nekrasov and Kllmov- spreading, depositing c<strong>on</strong>diti<strong>on</strong>s, temperature<br />

~kiy, 1978; Cornell, Law and Lake, 1972; Zabo- c<strong>on</strong>diti<strong>on</strong>s, permafrost cryogenic structxxe<br />

Lotnik, 1903; Yueheng et al., 19811.<br />

tuxned out to be weakly studied. That is why<br />

their studying was to be fulfilled simultane-<br />

In thia respoct, the Yaykalo-bmurakaya<br />

oualy with designing nnd sometimes during main<br />

Line occupies a special. place. Its surveys line c<strong>on</strong>structi<strong>on</strong> with the help of airphoto<br />

have been carried out with different intensity and spacephoto identificati<strong>on</strong>, engineering-&<br />

during several decades since 1932. At present geological survey, geophysical and drilling<br />

its c<strong>on</strong>structi<strong>on</strong>, begun in 1974, is completjng. works. On the whole, the B;L; engineering-and-<br />

As l<strong>on</strong>e ago as in 1937 a specially organized geological c<strong>on</strong>diti<strong>on</strong>s had been defined c o r e<br />

geocryological expediti<strong>on</strong> worked <strong>on</strong> the Bh1.1; however geocryologicnl support of the LlI.1 debeaideEt<br />

design and survey expediti<strong>on</strong>s it ful- siming turned out to be insufficient in the<br />

1407

1978;.K<strong>on</strong>dratyev, 1905) is as shown below<br />

(Table 2). In all, 3 periorla of permafroet rati<strong>on</strong><br />

investigati<strong>on</strong>s are singled out, corresp<strong>on</strong>din-<br />

gly: during surveying, c<strong>on</strong>ntructi<strong>on</strong> nnd opeof<br />

thc LIain Line.<br />

TlLBLU I<br />

Object of <strong>Permafrost</strong> Investigati<strong>on</strong>s for Railway C<strong>on</strong>atxucti<strong>on</strong> Pwposen<br />

.-<br />

Geologo-geographical c<strong>on</strong>diti<strong>on</strong>s Seas<strong>on</strong>aly frozen and permafrost Interacti<strong>on</strong> of railway idain<br />

<strong>on</strong> the railway route rocks<br />

and c<strong>on</strong>nected with them Line and permafroef<br />

cryogenic processes and phenome<br />

Geological structure (age of Temperatwe regime of rocks U w e of pemafrost c<strong>on</strong>dLti<strong>on</strong>s<br />

rocks, genesilt corn <strong>on</strong>iti<strong>on</strong> and (aual average temperatme in c<strong>on</strong>necti<strong>on</strong> with Ualn Line<br />

properties of rocksP. a d amplitude of its annual c<strong>on</strong>structi<strong>on</strong> (breakdown of geovariati<strong>on</strong>sl<br />

<strong>on</strong> the ground sur- logical-and-geographical c<strong>on</strong>di-<br />

Geomorphological structure (hyp- face, <strong>on</strong> the base of oeaso- ti<strong>on</strong>s, change of rock temperatusometry<br />

of relief elements, ex- nally thawed and seas<strong>on</strong>ally re regime, depth and rate of<br />

posuxe and gradient of slope). frozen layeFs, <strong>on</strong> the layer seas<strong>on</strong>al freezing and thawing<br />

base of annual temperature of xocks, development of para-<br />

Hydrogeological c<strong>on</strong>diti<strong>on</strong>s (prcr variati<strong>on</strong>s)<br />

meters and of immerging permapagati<strong>on</strong>,<br />

de ositing a<strong>on</strong>diti<strong>on</strong>e,<br />

frost, new permafrost formati<strong>on</strong><br />

type, hydraufic features, c<strong>on</strong>di- Seas<strong>on</strong>al thawing and freezing and perennial thawing, developti<strong>on</strong>8<br />

of power supply, +ransit of soils (type of seas<strong>on</strong>al ment of cryogenic processes and<br />

and unloading, reservea, chemi- thawing OF freezing of soils, phenomena).<br />

cal compositi<strong>on</strong> underground wa- thickness; period and rate of<br />

ter temperature j .<br />

seas<strong>on</strong>al thawing or freezing Change of permafrost c<strong>on</strong>diti<strong>on</strong>s<br />

of soils; compositi<strong>on</strong> and cry- In c<strong>on</strong>necti<strong>on</strong> vri th Lain Line<br />

Geobotazlic c<strong>on</strong>diti<strong>on</strong>s (type, ogenic structure of seas<strong>on</strong>ally operati<strong>on</strong> (c<strong>on</strong>structive and<br />

epecies compositi<strong>on</strong> of vegetn- thawed or seas<strong>on</strong>ally frozen technological pecularities of<br />

ti<strong>on</strong>,degree of covering or layer).<br />

&in Line, forming of temperatuclosing<br />

of top crovms).<br />

re regime of roadbed,soils, of,<br />

<strong>Permafrost</strong> thiclmese of rocks its base and of right-of-way;<br />

Olimate c<strong>on</strong>diti<strong>on</strong>s (radiati<strong>on</strong>- (propagati<strong>on</strong>, depositing c<strong>on</strong>- layer forming of seas<strong>on</strong>al thawand-heat<br />

balance of the Burface; diti<strong>on</strong>s, thiclcnesa, composi- ing or freezing<br />

,<br />

of xocks, new<br />

precipitati<strong>on</strong> quantlty, air hu- ti<strong>on</strong>, cryogenio structure, ge- permafrost formati<strong>on</strong> and ita<br />

midity, amuaZ average tempexatu-nesirs, hietory of forming and degradati<strong>on</strong>, development of cr -<br />

re and amalituda of annual air development of permafrost thicr ogenic processes and phenomenay.<br />

miag, o<strong>on</strong>necti<strong>on</strong> with geologogeographical<br />

medium factors end<br />

permafrost c<strong>on</strong>diti<strong>on</strong>s, paragenesis,<br />

dynamics, directi<strong>on</strong> and<br />

potential posslbilities of process<br />

and phenomena development).<br />

During surveying investigati<strong>on</strong>s are carried<br />

out in 3 phases: feasibility study, project<br />

and working documentati<strong>on</strong> of the railway c<strong>on</strong>structi<strong>on</strong>.<br />

On the feasibility study phase it<br />

is expedient to carry out investigati<strong>on</strong>s in<br />

two stagee: materials of the previous works<br />

and aero-viaual examinati<strong>on</strong>s are analyoed <strong>on</strong><br />

the first stage, and <strong>on</strong> the sec<strong>on</strong>d - investigati<strong>on</strong>s<br />

proper are fulfilled. Only <strong>on</strong>e stage<br />

of works is singled out <strong>on</strong> other phases. The<br />

regularities of formati<strong>on</strong> and development of<br />

permafrost c<strong>on</strong>diti<strong>on</strong>s in natural c<strong>on</strong>diti<strong>on</strong>s<br />

at blain Line o<strong>on</strong>structi<strong>on</strong> and operati<strong>on</strong> must<br />

be revealed during surveys as a result of pep<br />

mafrost investigati<strong>on</strong>s. The investigati<strong>on</strong> ac-<br />

tivity muat be enough for selecti<strong>on</strong> of optimum<br />

c<strong>on</strong>structive and technological soluti<strong>on</strong>s and<br />

assigning of effeotive measures <strong>on</strong> c<strong>on</strong>trol of<br />

permafrost c<strong>on</strong>diti<strong>on</strong>s in order 'to ensure optimum<br />

c<strong>on</strong>structi<strong>on</strong> and operati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s for<br />

the railway line. A network of observati<strong>on</strong><br />

areas for investigati<strong>on</strong> of permafrost c<strong>on</strong>diti<strong>on</strong><br />

dynamics in natural c<strong>on</strong>diti<strong>on</strong>s must be<br />

made during surveys.<br />

At present, a8 is correctly stated by Yu.F.Zaharov<br />

(1983), prospectors are unable to fulfill<br />

truatworthy quantitive engineering-andgeological<br />

forecast as a result of shortage of<br />

engineering survey volume (envisaged by the<br />

'

~~ .<br />

TXBh 11:<br />

Scheme of Works at <strong>Permafrost</strong> Investigati<strong>on</strong>s<br />

Routes of the Hew Railway Lines<br />

Period Y tage Phase Type<br />

~ ~ ~~~ .<br />

”<br />

Purpose<br />

Sumreys Feasibility I. bstimnti<strong>on</strong> Collecti<strong>on</strong> and analysis of materials Selecti<strong>on</strong> of route<br />

study of permafrost <strong>on</strong> geological-and-eeographical perm& perspective directic<strong>on</strong>diti<strong>on</strong>s<br />

of frost c<strong>on</strong>diti<strong>on</strong>s Airphoto and space- <strong>on</strong>s.<br />

the supposed photo identificati<strong>on</strong>.<br />

c<strong>on</strong>structi<strong>on</strong> Aerovisual and ground investigati<strong>on</strong>s,<br />

regi<strong>on</strong><br />

c<strong>on</strong>s t PUC -<br />

ti<strong>on</strong><br />

ZI. Yorks <strong>on</strong><br />

Medium-8cale aerial photo&aphy and Selecti<strong>on</strong> of route<br />

route pcrspec- identificati<strong>on</strong> of photographs<br />

opttmwn directi<strong>on</strong><br />

tive direc- Landscape z<strong>on</strong>ing of the territory Polyg<strong>on</strong> selecti<strong>on</strong> for<br />

ti<strong>on</strong>s in IO- and selecti<strong>on</strong> of key areas<br />

testing-and-experima-<br />

20 km wide Small scale permafroat survey ie <strong>on</strong> tal works<br />

z<strong>on</strong>e<br />

Iviain Line Linear part; medium slaw Selecti<strong>on</strong> and basing<br />

survey is <strong>on</strong> stati<strong>on</strong> sectt<strong>on</strong>s and of permafrost etati<strong>on</strong><br />

traneiti<strong>on</strong>s over large rivers and XoCRfiOB<br />

water shede.<br />

Geocryological m<strong>on</strong>itoring is in natural<br />

c<strong>on</strong>diti<strong>on</strong>s.<br />

Natural-historical and general technogenic<br />

permafrost forecast.<br />

Project III.Ylorks <strong>on</strong> Detailed aerial photogmphy and iden- Selecti<strong>on</strong> of route<br />

selected di- tificati<strong>on</strong> of photographs. optimum alternative,<br />

recti<strong>on</strong> ~CCOP Ivledium soale permafrost survey is oantre-lbe locati<strong>on</strong>,<br />

ding to route carried aut <strong>on</strong> Main Line linear part track schemes and<br />

alternatives .and large scale survey <strong>on</strong> secti<strong>on</strong>s structures<br />

in 10-20 km of operati<strong>on</strong> points and barrier plawide<br />

z<strong>on</strong>e ces<br />

Geocryologioal m<strong>on</strong>itoring is carried<br />

out in natural c<strong>on</strong>diti<strong>on</strong>s and <strong>on</strong> BXerimental<br />

areas<br />

8 echnogenic permafrost forecast<br />

Ingeneering-and-geocryological z<strong>on</strong>ing<br />

iforlcing do- IV. Yiorks <strong>on</strong> Large scale detailed permafrost BUTcumentati<strong>on</strong><br />

roqte in 0.5- vey is carried out <strong>on</strong> Main Line li-<br />

1 km z<strong>on</strong>e near part, <strong>on</strong> secti<strong>on</strong>s of operati<strong>on</strong><br />

pointa and barrier places.<br />

Geocryological m<strong>on</strong>itoring is made in<br />

natural c<strong>on</strong>diti<strong>on</strong>s <strong>on</strong> experimental<br />

areas<br />

Technogenic permaimst forecast<br />

Elaborati<strong>on</strong> of recomendati<strong>on</strong>s <strong>on</strong><br />

permafrost c<strong>on</strong>diti<strong>on</strong> c<strong>on</strong>trol<br />

AdOptbLI Qf final C*<br />

structive and techuological<br />

soluti<strong>on</strong>s.<br />

Uaborati<strong>on</strong> of measurea<br />

<strong>on</strong> enauxance of<br />

Main Line Btability<br />

and envtror<strong>on</strong>tnent protecti<strong>on</strong><br />

V. fiorks in C<strong>on</strong>trol <strong>on</strong> cr8cuti<strong>on</strong> of c<strong>on</strong>etruc- Xnsurance of Main<br />

right-of-way tive measuxea <strong>on</strong> c<strong>on</strong>servati<strong>on</strong> ox im- Line stability and<br />

provemenf of permafrost c<strong>on</strong>diti<strong>on</strong>s envir<strong>on</strong>ment protec-<br />

Geocryological m<strong>on</strong>itoring in natural ti<strong>on</strong><br />

c<strong>on</strong>diti<strong>on</strong>s and in right-of-way<br />

Correcti<strong>on</strong> of measures <strong>on</strong> permafroat<br />

c<strong>on</strong>diti<strong>on</strong> c<strong>on</strong>trol<br />

Operati<strong>on</strong> VI. Works in C<strong>on</strong>trol <strong>on</strong> executi<strong>on</strong> of technologi- hswance of blain<br />

right-of-way cnl measuxes <strong>on</strong> c<strong>on</strong>servati<strong>on</strong> ox in- Line stability and<br />

provement of permafrost c<strong>on</strong>diti<strong>on</strong>s envir<strong>on</strong>ment protec-<br />

Geocryological m<strong>on</strong>itoring of railway ti<strong>on</strong><br />

Main Line<br />

Correcti<strong>on</strong> of measures <strong>on</strong> permafrost<br />

c<strong>on</strong>diti<strong>on</strong> c<strong>on</strong>trol<br />

1410

normative documents) for complex acti<strong>on</strong> estimati<strong>on</strong><br />

<strong>on</strong> geolagical medium and its reacti<strong>on</strong><br />

<strong>on</strong> technogenic loads. C<strong>on</strong>sequently, is it possible<br />

to form engineering-and-geooryological<br />

c<strong>on</strong>diti<strong>on</strong>a at projeot realizati<strong>on</strong> and l<strong>on</strong>g<br />

structure operati<strong>on</strong>, which essentially differ<br />

from the forecmted <strong>on</strong>es. That is why it ie<br />

expedient to create a special permafrost service<br />

at board of diractors of the c<strong>on</strong>structed<br />

railway; it will fulfil: permanent permafrost<br />

c<strong>on</strong>trol dming c<strong>on</strong>structi<strong>on</strong> and operati<strong>on</strong> of<br />

the.hlain Line for accomplishing measLu.eB ensuring<br />

ita stability and nature protecti<strong>on</strong>;<br />

regime observati<strong>on</strong>s of permafrost c<strong>on</strong>ditl<strong>on</strong><br />

changw <strong>on</strong> the route under c<strong>on</strong>dzucti<strong>on</strong>; study<br />

of cryogenic process effects <strong>on</strong> operati<strong>on</strong><br />

of railway installati<strong>on</strong>s and operative correcti<strong>on</strong><br />

of measweB <strong>on</strong> improvement of geocryologioal<br />

c<strong>on</strong>diti<strong>on</strong>e of their operati<strong>on</strong> and envir<strong>on</strong>ment<br />

protecti<strong>on</strong>.<br />

Proceeding from the abovementi<strong>on</strong>ed maderstanding<br />

of the geocxyologioal provisi<strong>on</strong> essence<br />

for the railway c<strong>on</strong>atructi<strong>on</strong>, the primary.<br />

tasks of the ermafrost investigati<strong>on</strong>s <strong>on</strong> the<br />

Berlcakit-Yakufsk railway line route (being <strong>on</strong>e<br />

of the BAM sub-meridi<strong>on</strong>al developments) cm be<br />

formulated in the following way: 1) oarrybg<br />

out of large-scale and detailed permafrost<br />

survey 01’1 secti<strong>on</strong> up to Tomot and.mecUum-and<br />

large-mala permafrost erumrey <strong>on</strong> secti<strong>on</strong> lornmot-Yaltak;<br />

2) elaborati<strong>on</strong> of technogenic per<br />

mafrost forecarst for drawing up of a project<br />

and working documentati<strong>on</strong> of the railway installati<strong>on</strong>s;<br />

3) elaborati<strong>on</strong> of meaBuxe8 <strong>on</strong><br />

permfroet c<strong>on</strong>ditr<strong>on</strong> o<strong>on</strong>troL at th8 base of<br />

railway installati<strong>on</strong>e and.oa the adjacent territory<br />

for enaurame of optimum geocryological<br />

c<strong>on</strong>diti<strong>on</strong>s of o<strong>on</strong>structi<strong>on</strong> and operati<strong>on</strong> of<br />

structures ana envir<strong>on</strong>ment protecti<strong>on</strong>; 4) organizati<strong>on</strong><br />

of Main h e geocryological m<strong>on</strong>itoring<br />

for errnairost ooladiti<strong>on</strong> permanent c<strong>on</strong>tml<br />

a d wsll-!imed suppressi<strong>on</strong> ox reduoti<strong>on</strong> of cry.<br />

ogenic #rocem effects OM stratwee; 5) study<br />

of the AM and permafrost c<strong>on</strong>e real intermtiou,<br />

generalizati<strong>on</strong> of engineering-and-geocryologlcal<br />

investigati<strong>on</strong> experience <strong>on</strong> the BAM<br />

with learnlng of neceesexy less<strong>on</strong>s, meaning<br />

improvement of normative-methodological base<br />

of surveya, railway designing and c<strong>on</strong>structi<strong>on</strong><br />

in the permafrost regi<strong>on</strong>s and elaborati<strong>on</strong> of<br />

effective meaauree <strong>on</strong> “treatment of sore spotel’<br />

of the Main. Line.<br />

At present Nosguiprotrana has come to soluti<strong>on</strong><br />

of the first three problems with cooperati<strong>on</strong><br />

of the Moscow State University permafroat<br />

ohair, of the l’derzlotovedenije institute of<br />

the Aoademy of Soienoe, of the Tynda permafro&<br />

stati<strong>on</strong> and the Novosybirsk branch of the Central<br />

Reseerch Institute of Transport C<strong>on</strong>atructi<strong>on</strong><br />

within the programe limit8 of the engineering-and-geological<br />

surveys of the Berkakitfommot-Yakutsk<br />

railway line. A Propame of<br />

geocxyologioal investigati<strong>on</strong>s and further BAM<br />

m<strong>on</strong>itoring is also being elaborated.<br />

So, <strong>on</strong>ly deep and well-timed study of formati<strong>on</strong><br />

and development regularitlea of pertnafrost<br />

c<strong>on</strong>diti<strong>on</strong>s, systematic c<strong>on</strong>trol of their dynamics<br />

at territory development and cryogenic<br />

effects <strong>on</strong> stxuctwes, realizati<strong>on</strong> of their<br />

permafrost protectL<strong>on</strong> measures will make it<br />

141 1<br />

possible to realize stability and reliability<br />

of railways and also invir<strong>on</strong>ment protecti<strong>on</strong><br />

in the permafrost z<strong>on</strong>e.<br />

K;%WHiLIJCdS<br />

Bykov, N.I., Kapterev P.N. (1940). Vechpaya<br />

merzlota i stroitelstvo na ney. X.: Pran~<br />

zheldorhdat, 372.<br />

Guletakiy V.V., blinaylov G.P. (1984). . Bermy<br />

v k<strong>on</strong>struktsiyah nizkih nasipey na maxew<br />

h uchastkah. - TransDortnote atroitel-<br />

gicheskie -issledoVarziya dlya oFoanovaniya<br />

lineynogo stroitelstva na Severe.<br />

Tr. PNIIYo, vip. 52, 21-29.<br />

Zaharov Yu.P. ( 1983 ). Problemy iazhenernogeologicheskogo<br />

propozirovaniya v in&-<br />

nernyh izyakaniyah i projectirovaniye ga-<br />

z<strong>on</strong>efte romislovogo i truboprovodnogo<br />

stroiteEstva. v b. : Polysheniye effectivnosti<br />

inzhenernyh izyskaniy dlya<br />

sttoitelstva v neftenoan h ray<strong>on</strong>ah Zapad-<br />

noy Sibiri. Tyumen, 34-3 E .<br />

Zanzinov, X.I. (1986). Ot Yeterbuxga-Xoskovskoi<br />

do Baikalo-Amurskoi magistrali.<br />

Ei. t TranBport, 216.<br />

Ivenov 1~1.1, (1987), Opyt obespecheniya etabilnosti<br />

nasypey na prosadochnyh omovaniyah.<br />

Transportnoye stroitelstvo, N5,<br />

6-7<br />

K<strong>on</strong>dratyev V.G. (19G5). Merzlotnije issledovaniya<br />

v svyazi B proyektirovaniyem, sooruzheniy<br />

i ekspluatataiey severnih truboprovodov.<br />

V be: Neft i gaz Zapadnoy SlbPxi.<br />

Psoblemy dobychi transportirovki.<br />

Tyumen, 216-217.<br />

Lugovoy P.N.; Korolyev A.R.; Pozin V.A. i dr.<br />

(1983). Aktivniy metod borby B naledyami<br />

na BAMe. Tr,wsportnoye etroiteletvo, N12,<br />

3-4.<br />

Inrov A.V. (1916). Poiaki i ispytaniya istochnikov<br />

vodosnabzheniya na i5apadnoy<br />

chaati Amurskoy zh.d. v usloviyah Wechnoy“<br />

merzloty pochvy. Irkutsk: Ki3, 881.<br />

Merclotovedeniye (lcratkiy kurs). Pod red.<br />

Kudryavtaeva, V.A. (1981). X., Izdatelstvo<br />

Mosk. UT-ta, 240.<br />

Nekrasov 14.; IUimovsLiy 1.V. (1978). Vech-<br />

naya merzlota zany BAii. Novosibirsk: Nauke,<br />

115.<br />

Pisarev G.F.; Datskiy M.G. (1934). Vechnaya<br />

merzlota 1. ueloviya stroitelstva Y Usinskom<br />

ray<strong>on</strong>e Severnogo kraya,. L: Iad. AlJ<br />

YSSR, 144.<br />

3obofev P.V. (1984). Xkspluatasiya zdaniy i<br />

sooruzheniy na verchney merelote v usloviyah<br />

Bdlla. Transportnoye stroltelatvo,<br />

Ng, 23-24.<br />

Sobolev P.Y. (1985). BAL1 segodnya. Transporbnoye<br />

etroitelstvo, N8, 8-9.<br />

Suhodolskiy d.1. (1945). 0 sooruzhenii eemlyanogo<br />

zbeleznodorozhnogo polotna v usloviyah<br />

aevernih ray<strong>on</strong>ov oblasty vechnoy

merzloty. Tx. In-ta Kerzlotovedeniya im.<br />

V.A. Obrucheva, t.P.iI.-L: Iz-vo An SSSR,<br />

- 5-120<br />

Cornell, i4j.R.; Law, C.L.; Lake ii.i.'* (1971).<br />

The Arctic railway - envir<strong>on</strong>:nenntal aspects.<br />

- &g. J., 56, 3, 22-27.<br />

Zabolotnik, S.J. (1983). C<strong>on</strong>diti<strong>on</strong>s of <strong>Permafrost</strong><br />

Formati<strong>on</strong> in Z<strong>on</strong>e of the Raikal-<br />

Amur liailway. Perrrlafrost: Fourth inter- I.<br />

natolnal c<strong>on</strong>ference. ProceedingB, Nati<strong>on</strong>al<br />

academy preas. Washingt<strong>on</strong> D,C.,<br />

1451-1456.<br />

Yusheng L.; Xhugui W.; and e.a. (1383).<br />

<strong>Permafrost</strong> study and xailraad c<strong>on</strong>structi<strong>on</strong><br />

in permafrost weas of China: Fouxeh<br />

intornatioasl c<strong>on</strong>ference. Proceedings.<br />

Nati<strong>on</strong>al academy press, 707-714. Washingt<strong>on</strong>.-<br />

1412

VENTILATED SURFACE FOUNDATIONS ON PERMAFROST SOILS<br />

<strong>Permafrost</strong>, Soil Bed, Surface Foundati<strong>on</strong>, Ventilated Through Space,<br />

Heat-Engineering Analysis<br />

N.B. Kutvitskaya and M.R. Gokhman<br />

The Gersevanov <strong>Research</strong> Institute of Bases and Underground Structures, Moscow, USSR<br />

SYNOPSIS The main design soluti<strong>on</strong>s for ventilated surface foundati<strong>on</strong>s <strong>on</strong> penafrost Boils<br />

and their advantages as compared to other types of foundati<strong>on</strong>s are c<strong>on</strong>sidered. Principal propositi<strong>on</strong>s<br />

of the heat-engineering analusia of permafrost beds of ventilated surface foundati<strong>on</strong>s<br />

aye presented. ResultB of the heat-engineering analysis of a bed of an industrial building<br />

rested <strong>on</strong> a ventilated plate-type surface foundati<strong>on</strong> are given.<br />

Ventilated surface foundati<strong>on</strong>s <strong>on</strong> permafrost<br />

eoils are serving aa both a supporting foundati<strong>on</strong><br />

c<strong>on</strong>structi<strong>on</strong> and a soil cooling meane.<br />

Such foundati<strong>on</strong> furnishes a thin-walled reinforced:<br />

c<strong>on</strong>crete spatial syetem being mounted<br />

<strong>on</strong> a subbed which is prepared from plane plates,<br />

channeled or hipped plate elements,hollow volumetric<br />

blocks, Cooling of bed soils which<br />

yields creati<strong>on</strong> and preservati<strong>on</strong> of their specified<br />

temperature regime is brought about in<br />

winter period by the moti<strong>on</strong> of the cold a-tmospheric<br />

air through spaces provided in<br />

a foundati<strong>on</strong>. Ventilated foundati<strong>on</strong>s of a plate<br />

or strip type are empoyed depending <strong>on</strong> a character<br />

of loadin2 transmitted from buildings or<br />

structures. Pig.1 shows examples of crosn-secti<strong>on</strong>al<br />

view of beds with a plate foundati<strong>on</strong> (a)<br />

and a strip foundati<strong>on</strong> (b).<br />

/<br />

B I 6<br />

4 h<br />

Fig.1 Cross-secti<strong>on</strong>al views of bedo with a<br />

plate foundati<strong>on</strong> (a) and a strip ioundati<strong>on</strong>(b).<br />

Compared to deep foundati<strong>on</strong>s (pile founda-Li<strong>on</strong>s ,<br />

column pad founda-ti<strong>on</strong>u and others) the erpoy-<br />

aent of ventilated surface r"oundati<strong>on</strong>s embles<br />

to eliminate alxost completely the labour-c<strong>on</strong>awning<br />

and expensive excavati<strong>on</strong> of fr*ozen soils<br />

and to reduce the c<strong>on</strong>euptior, of buildins xaterials<br />

and electric energy. Surface foundatiocs<br />

take loads transmitted to the:x by upper stnctures<br />

and distribute then al<strong>on</strong>g the soil surface<br />

beneath a building thus reducing the pressure<br />

<strong>on</strong> soil lay ex^ occuned below. Pheefore<br />

this type of a foundati<strong>on</strong> is advantageous to<br />

employ at sites built by salty high-texpeFatuIne<br />

ice-saturated soils as sell as by eoile '<br />

with crgopegs and under;round ice. The bearing<br />

capacity of a soil bed of a ventilated surface<br />

foundati<strong>on</strong> is defized. essentially by phpical<br />

and mechanical characteristics of bed upper<br />

soil layers vrhich,in turn, depend <strong>on</strong> a thernal<br />

regime in a building and inside of foundati<strong>on</strong><br />

ventilated through spaces as well as qn a thermal<br />

re,ri:ae of a soil surface around a building.<br />

4s a c<strong>on</strong>sequence the soluti<strong>on</strong> of a problea <strong>on</strong><br />

c<strong>on</strong>jugate heat transfer i:1 a spten "buildingventilated<br />

foundati<strong>on</strong>-pei..mafrost enables<br />

to detennin uniquelly the Searin, capacity of<br />

a ventilated surface foundati<strong>on</strong> bed. P'he analytical<br />

xethod of the heat-engineering analysis<br />

which was developed enables to select principal<br />

parameters of a foundati<strong>on</strong> coolhg system which<br />

ensure a required bearin,; capacity of a bed.<br />

'Jith this ai:n in vien,at given designs of a<br />

structure floor,subbed and ventilated foundati<strong>on</strong><br />

ic is determined through the use of heatengineedng<br />

analysis a depth of seas<strong>on</strong>al thawing<br />

of soils beneath a s-tmc,i:u:-e and there are<br />

computed telnperatuzes of pemafrost ued - ;he<br />

!naximun texperatures at a given depLh ~,T:!~,and<br />

man maximum tenperaLu-es ai<strong>on</strong>,; a depth z,Te ,<br />

accor,ding to a inean tenperature fo1, the ventilati<strong>on</strong><br />

peldod and. an average annual l;e1!lpel-ature<br />

of fomdati<strong>on</strong> through space wall. 3el<strong>on</strong> is given<br />

the distributi<strong>on</strong> of the :.lean fo-4 the ventilati<strong>on</strong><br />

peLsiod temperature, lhv, of the foudatior,<br />

through space wall al<strong>on</strong>g the foundati<strong>on</strong> axis y<br />

which was analgticnlly oo'taincd sy Gokh:~an and<br />

Ivanov (1985) and i:;l'ourlded exp:*i:xn&all; by<br />

Kutvitskaya (19713).<br />

1413

In -the equaxi<strong>on</strong> (2) .the terns x th and x, are<br />

the thexal cor-!ilucr;i-vi;y of thane6 and frozen<br />

soii :-e3pectl-~eLy, 2.<br />

In<br />

is the air texperature<br />

ill a s:rl;cc\X..*e. =!:e effect of geo:ne,trical para:x've:s<br />

si a subbed and a ventllated foundati<strong>on</strong><br />

<strong>on</strong> the c<strong>on</strong>jugate heat exchange in the systen<br />

uxier c<strong>on</strong>siderati<strong>on</strong> is tairen into account<br />

in ;he equati<strong>on</strong>s (1) and (2) through the use<br />

01 ;;eneralized characteAstics of the stati<strong>on</strong>a<br />

q te:nperature fields and.the heat flows -<br />

the fom-facto- of the sgstm, , and the functi<strong>on</strong><br />

of its c<strong>on</strong>figuraGi<strong>on</strong>, f, Gokh.ian,Ivanov,<br />

1.337). For the purpose of practical coaputati<strong>on</strong>s<br />

according to the equati<strong>on</strong>s (1) and (2)<br />

it; was developed a prooedure for detemining<br />

9 ar,d f by :he nel;hod of elec%-ical analoey<br />

ba8ed or, the use af two-dimensi<strong>on</strong>al xodels :nade<br />

f:o:n the electroc<strong>on</strong>ductive paper and the electi-ic<br />

integ2a:or YdGiUft. Sinulasi<strong>on</strong> r

characteristics of the bed soils.<br />

As an example,Pig.3 shows the coefficient<br />

as a fuhcti<strong>on</strong> of its parametecs. IIei-e, R is the<br />

Pig.3 Coefficient<br />

parameters.<br />

ki as a functi<strong>on</strong> of its<br />

width of the ventilated through space bottom;<br />

b is the distance between the axes of ,the adjacent<br />

ventilated through spaces; Cf and af are<br />

the heat capacity per unit volume and the thermal<br />

diffusivity of the frozen soil respectively<br />

( af = af/Cf). The families of curves 1,2 and 3<br />

corresp<strong>on</strong>d to the values of the parameter B/b=<br />

0.1 ;0.25;0,5 respectively. The solid,dotted and<br />

dash-dol; lines corresp<strong>on</strong>d to the values of the<br />

parmeter z/ = 25;50 and 100h '05 respectively.<br />

Below are given main results of the heat<br />

engineering analysis of a bed of an industrial<br />

building which measures 24 x 48 m in plan and<br />

is c<strong>on</strong>structed <strong>on</strong> a ventilated surface foundati<strong>on</strong><br />

rested <strong>on</strong> a fill. The analysis is made according<br />

to the methodology given above. The<br />

fill is prepared from sand soil exhibiting the<br />

total moisture c<strong>on</strong>tent ltot - 0.1 and the den-<br />

.Psity<br />

p dfp = 1.6 t<strong>on</strong>s/m3. As it is so,the heat<br />

c<strong>on</strong>ductr<strong>on</strong> of the fill Soil in a -thawed and<br />

frozen state hatth = 1.45 Vt/(mOC) and<br />

A fp = 1.62 Vt/(moC$ respect-ively. The bed soil<br />

is the sand exhibiting the temperature To= -0.5<br />

OC; the total moisture c<strong>on</strong>tent Vtot = 0.2 and<br />

,the densii;ypdf = 1.5 t<strong>on</strong>s/m3 , the heat c<strong>on</strong>ducti<strong>on</strong><br />

of the bed soil in a thawed and frozen<br />

state isb,th = 2.15 Vt/(moC> andlf= 2.38Vt/<br />

(m°C) respectively; the heat capacity per unit<br />

volume of bhe soil in a frozen state is Cf =<br />

2140 ltJ/(12~~C) . The "computed air .temperature<br />

in the buildin): is T. P 18 OC,<br />

In<br />

the :lean wind<br />

veloctty and the at:nospheric air te:llpel.atu.re<br />

over the ventilati<strong>on</strong> period (tv = '1 n<strong>on</strong>thn) are<br />

IC,:<br />

Crete elements and nan the following parmeters:<br />

the height II = 1.5 m; the width 3f ihe ventilated<br />

throu;;h space bottom 2 = 1.5 m; the thicknesu<br />

of the fill aemath the foundati<strong>on</strong> underside<br />

level h = 0.5 m; the addxiosible depth<br />

P<br />

of the seas<strong>on</strong>al tharlng of the bed noils hthC<br />

0.9 In. Accordine to the results of the analyois<br />

the required resistance to the heat transfer<br />

from the floor stxcture abo;re the foundati<strong>on</strong><br />

ventilated througn spaces is Ro = 3.2<br />

m'OC/ Vt and above :hc n<strong>on</strong>ventilated th::ough<br />

spaces it is ;In = 2.5 n20C/ 'Jt. Ir, :his case<br />

it is necessa2y to ventilate e-rerl third tbrou.Eh<br />

space in the J"oundati<strong>on</strong> (1; a 3B = 4.5 .:).<br />

The mean fenperature o-~er the -Jenbilati<strong>on</strong> pe--<br />

fod and the average annual tenperature of the<br />

ventilated through space wall at ihe 3 7 3 ,,let<br />

'<br />

(y = 48 m) are Thv =-I 5.9 OC and Tha= - 8.6 OC<br />

respeckively. The cornputed depth or' the Beas<strong>on</strong>al<br />

thawing of the subsoil beneath -the fomdati<strong>on</strong><br />

through space botto:n is equal i0.D.J<br />

n<strong>on</strong>unifomity of tha.;Ting of the bed 1s<br />

- 0.7 = 0.2 m. Distributi<strong>on</strong> of the :naxi:num temperatures,<br />

Tm, of soil beneath ,the ventilated<br />

through space bott<strong>on</strong> in depkh is given in Table<br />

I.<br />

TOLE I<br />

Distributi<strong>on</strong> of maximus soil tezperatures<br />

in depth<br />

yp<br />

The :nain para3:leters of the foundati<strong>on</strong> cooling<br />

system, which ensure the i-equired bearing capacity<br />

of the bed, may be selected <strong>on</strong> the basis<br />

of the proposed procedure for the heat-errgineering<br />

analysis.<br />

REFERXHCES<br />

Gokhmsn,M.R., IV~OV,MOM. (1985). US~~OV~V<br />

ahiyeya teploobmen lineynih podzemnih<br />

eoorujeniy I oftaivayuehim (promereapshim)<br />

gruntom.<br />

In enerno-Phizicheskiy Jurnal, (48),4,<br />

a.L,Moahs.<br />

ir = 5.1 rn/s and Tout.V = - 13.6 OC respectively. Gokhman,M.Rt, Tvanov,M.M. (1987). Analitiche-<br />

2he L'oundati<strong>on</strong> is surface,ventilated,of plate<br />

skle 3 chialennie metody rascheta aopryatype,<br />

built from prefabricated reinforccd c<strong>on</strong>-<br />

jennogo<br />

jeniy<br />

teploobmena zsglubly<strong>on</strong>nih sooru-<br />

0 vechnomerzlimi gruntmi.<br />

141 5

Pe'dorovich,D.I.,Gok~~,~~~~ (1985). Utochnenie<br />

raechetnih temperatur vechnomsrslih<br />

gruntov v omovanil. zdaniy i ~ooruj<br />

eni y.<br />

Oenovaniya,Fundamenty i Mekhanika Grunfov,5,es.22-24,~oskva.<br />

~rudy Nauchno-X,ssLedovatelskogo Inmtituta<br />

Osnovaniy i Poazemrdh soorujeniy,69,<br />

88.117-1 26, MOB~VEL.<br />

1416

RESULTS OF RESEARCHES AND EXPERIENCE OF<br />

HYDRAULIC MINING OF FROZEN ROCKS<br />

N.P. Lavrov, G.Z. Perlshtein and V.K. Sarnyshin<br />

All-Uni<strong>on</strong> Scientific <strong>Research</strong> Institute of Gold and Rare Metals, Magadan, USSR<br />

SYNOPSIS<br />

Ice-rich fine-dispersed SedimentE may be successfully mined by a hydraulic<br />

method. Tn this report the new1 determined regularities of hydrowashing of thawing rocks are<br />

given, The formulae for cslculafi<strong>on</strong> of water temperature and deneity of heat flow into eroding<br />

rock MeBif am given.The dependence of intensity of erosi<strong>on</strong> of loamy-sand and loamy rocks <strong>on</strong><br />

their initial moisture is studied. The results of the researches are realized in Borne flow<br />

sheete of hydrowaehing of permafrost placere.<br />

There axe thiok ice-rich Tine-dispereed<br />

sediments that are widely distributed through<br />

Arctic and Subaxatlc z<strong>on</strong>ee of permafroat. The<br />

problem of their mining by a hydraulic method<br />

ie of great interest since the use of earthmoving<br />

equipment for this purpose does not<br />

aetsum good performance.<br />

So called washing off works were mastered in<br />

Rusmia early in the 19th century at the Ural<br />

and Altai placere. To the end of the last<br />

century rook waehing by preseure jetsr had got<br />

wide use at the Lena and Zabaikal placers.<br />

In the 40-es of this century hydrauLio<br />

stripping operati<strong>on</strong>s were agreat srucceo~ in<br />

permafrost lacers near Fairbanks ,Alaska.<br />

The hydra& mining of placers in permafrost<br />

regi<strong>on</strong>8 of the USSR was employml but in rare<br />

cams beoauss of a defficient atudy of<br />

quantitative regularitlea of water Plow<br />

interacti<strong>on</strong> with eroding permafrost.<br />

To fill u the gap the author. have carried<br />

out the whe complex of theoretical and<br />

experimental reeearches, The analysis of heat<br />

exchange in the syetemr thawing rocke - water<br />

Plow - atmoaphere waa given. The water flow<br />

of a Bingle width moving over the suxface of<br />

the thawed rock layer of h thicknefla al<strong>on</strong>g<br />

a axi~ was c<strong>on</strong>sidered.<br />

The temperature chan ing through the flow<br />

length occur8 under fhe influence of heat<br />

exchange with atmosphere and rock. It ia<br />

supposed that owing to turbulent water mixing<br />

its temperature down the depth does not change.<br />

On the water surface them ia a c<strong>on</strong>vective<br />

heat exchange with air ( Hc ) and energy<br />

exchange by evaporati<strong>on</strong> or c<strong>on</strong>densati<strong>on</strong> ( M ).<br />

The water surfaoe also receives radiant<br />

energy in the form of total shortwave radiati<strong>on</strong><br />

( Pt 1 and l<strong>on</strong>gwave atmoaphere ( ID 1<br />

radiati<strong>on</strong>, According to the aurface albedo A<br />

the art of ehortwave radiati<strong>on</strong> of AQt<br />

quaneity ie rafleoted. Like any heated body<br />

water flow emits l<strong>on</strong>gwave energy ( Iw 1 into<br />

space. We d<strong>on</strong>'t. c<strong>on</strong>sider tho radiant heat<br />

erchango below water eurface as this practically<br />

has no effect <strong>on</strong> final results. Beoidee,<br />

1417<br />

the papt of heat ( 4 ) ier tmsferinng thxough<br />

the thawed layer to permafrost surface.<br />

As follows from the law of c<strong>on</strong>servati<strong>on</strong> of<br />

energy the changing of water flow heat c<strong>on</strong>tent<br />

fox an area of elemental length dx is equal<br />

to the algebraic sum of heat ~ouraes acting<br />

<strong>on</strong> the area:<br />

where c in the volume specific heat of water,<br />

W'h/(y3*0C); T is the water ternperature,OC;<br />

k) 1w a single c<strong>on</strong>sumpti<strong>on</strong> of water flow,<br />

m3/(m*h) .<br />

The deneity of heat flow Fnto thawing massif<br />

ie defined from:<br />

af IS the coefficient of water PLo heat<br />

exchange with under1 inng rocks,W/(myaoC); Tr<br />

j,s the rock surface $emperature,OC; h is<br />

the thermal c<strong>on</strong>ductivity of thawing xockB,<br />

W/(m*oc).<br />

The effect of water flow velocity <strong>on</strong> at<br />

erosi<strong>on</strong> or loamy-sand and loamy sediment8 is<br />

experLmentally researched (fig.1).<br />

Expressing the remaining c<strong>on</strong>stituents of heat<br />

exchange by the known physical lwas (Newb<strong>on</strong>'S,<br />

Stefan-Boltaman's) and using their lhear<br />

ap roximati<strong>on</strong>s taking into account formula<br />

(*P,letIs present equati<strong>on</strong> (1) aa:

c<strong>on</strong>ducti-<br />

al ia the coefficient of heat exchange<br />

beiween water flow and air,W/(rn2*°C); 7 , Tu<br />

is the temperature of water and aix, respectively<br />

OC; be is the COB ficient of evaporati<strong>on</strong><br />

(c<strong>on</strong>densati<strong>on</strong>) ,W/(ms*Pa); e, , ea are<br />

the elasticities of aaturating vapour at OaC<br />

and water vapours in air, respectively,Pa: B<br />

i8 the Coefficient of linear approximati<strong>on</strong> of<br />

the dependence of saturating vapour presswe<br />

<strong>on</strong> temperature ,Pn/OC; Io is the heat radiati<strong>on</strong><br />

of surface at O°C,W/m*; cGr is the coefficient<br />

of linear appr ximati<strong>on</strong> of power law of heat<br />

radiati<strong>on</strong>,~/(mE*Oc).<br />

flows at initial temperature 7OC, single<br />

water c<strong>on</strong>sumpti<strong>on</strong> 50m2/h, atream velocity<br />

0.5 B and its respective value of aLf ~2000<br />

W/($-0C). The coefficient of heat I<br />

vZ%y of thawed rock is 1.0W/(m-8C), The reeults<br />

of calculati<strong>on</strong>s are <strong>on</strong> fia.2,<br />

- &vr w/m2<br />

Fig.1 De endence of the Coefficient of<br />

Hent Exchnge (&,c 1 <strong>on</strong> Water Flow Velocity<br />

(V 1 when Eroding Loamy-Sand and Loamy<br />

Sediments<br />

BY Solving equati<strong>on</strong> (3) wit boundary c<strong>on</strong>diti<strong>on</strong><br />

TTQ)=J, we define theJaw of temperature<br />

change al<strong>on</strong>g water Plow length:<br />

It is interesting to note that a8 follows<br />

from formula (4) at the at the L<strong>on</strong>gest length<br />

directly down the frozen<br />

rocke surface the water temperature remains<br />

higher than OOC by the 2 value,which is<br />

usually equal to 0.1-0.5°C.<br />

of run ( X - - )<br />

The average density of heat flow ( 4av ) into<br />

thawing rocks at an area of e length is:<br />

where m=& 9 n=- ae -<br />

CCI)<br />

For the climate c<strong>on</strong>diti<strong>on</strong>s of the midp<br />

stream of Ichuveem river ( q0 -430W/m ;<br />

ah+be+cCr =39~/(rn2*0~) accordaq to formu-<br />

La (5) we've calculated the heat coming info<br />

the rocke down the surface o.f which water<br />

1418<br />

v<br />

f hl cm 2<br />

Fig.2 Dependence of Average Daneity OP<br />

Heat Flow ( Q y 1 into Thawing Massif <strong>on</strong><br />

Thicknesa (h 5 of Thawed Lager at a<br />

Different Length ( d ) of Water Runt 1-20n-1,<br />

2-4Om, 3-60m. The explanati<strong>on</strong>a are in the<br />

text<br />

The attenti<strong>on</strong> ia drawn to the fact of sharp<br />

decrease of qav at increasbg the thickness<br />

of accumulated thawed layer. So at h =la<br />

and e =50m the density of heat flow ia<br />

a proximately 10 tirnea lese than in oam of '<br />

lgmiting thermoerosi<strong>on</strong> waehing at which h 4.<br />

From formula (4) it is not difficult to find<br />

the c<strong>on</strong>diti<strong>on</strong> of water flow heating, i.e. its<br />

cooltq acti<strong>on</strong> <strong>on</strong> underlying rocks. In the<br />

given example the thawed layer critical thicknesa<br />

at which water flow transfers to the<br />

regime of heating i~l 4.5cm.<br />

In terns of etatsd it ia obvious that at<br />

hydrom<strong>on</strong>itor mining of thawed rock layem<br />

a water supply method is to amsure the l<strong>on</strong>gest<br />

posBible c<strong>on</strong>tact of flow with frozen ~u~face.<br />

To realize thia the hydraullc mining with<br />

gradual retreat of eroai<strong>on</strong> fr<strong>on</strong>t away from a<br />

tranmort trench waa umd. At a o<strong>on</strong>stant<br />

velocity of face advance for an e distance<br />

the coefficient of heat-away is expremed by:<br />

In the given case the coefficient of heat-away<br />

meane the relati<strong>on</strong> of the heat quantity<br />

absorbed by racks to the initial heat o<strong>on</strong>tint<br />

Of Water flow. When c<strong>on</strong>ducting the experimental<br />

works at a hydrowaahing polyg<strong>on</strong> quite<br />

satisfactory coinaidence of formulae (5);(6)<br />

with the results of obaemati<strong>on</strong> ie found. For<br />

example, the deviati<strong>on</strong>a of actual Kh values<br />

Prom.the rated *3u1ves didn't exceed 1Oper cent<br />

(fig.3).

point is difficult to explain otherwise than<br />

a tlpeeling'l phenomen<strong>on</strong> under the influence of<br />

the qradient of capillary pressi<strong>on</strong> which i~<br />

the ZarRer the lower the initial w' value,<br />

Pig.3 Relati<strong>on</strong> between the Coefficient<br />

of Water Flow Heat-Away (Kh 1 and the<br />

Strip Width ( e ) of Washing at a S nale<br />

C<strong>on</strong>sumpti<strong>on</strong> of 1 - 50&h, .2 - 7O&h<br />

When forcing frozen rockn by water flow and<br />

low-head jets the particles of already thawed<br />

Layer am swept away. The la er's maximum<br />

thickness ia determined by de relati<strong>on</strong> of<br />

thawing veloclty to the intensity of rook eroai<strong>on</strong><br />

at the given hydrodynamic charecterietics<br />

and the temperature of flow.<br />

Multiple laboratory experiments c<strong>on</strong>firm the<br />

result8 of the preceding researches (Yerahov<br />

a.0. ,1979; Myrtehulava,1967): 1)thm decrease<br />

of erosi<strong>on</strong> intensity and the riae of n<strong>on</strong>-ero-<br />

ding velocity in the range sand - loamy sand -<br />

loam; 2)sharp decelerati<strong>on</strong> of eromi<strong>on</strong> intensity<br />

increase at reachinR some Plow velocity<br />

corresp<strong>on</strong>ding to the beginnin8 of limiting -<br />

thexmoerosi<strong>on</strong>al regime,<br />

The new data have been got c<strong>on</strong>cerning the<br />

c<strong>on</strong>necti<strong>on</strong> of loamy aands and loams erosi<strong>on</strong><br />

ability with their total moiature c<strong>on</strong>tent in<br />

unfrozen and frozen date (fig.4).<br />

As for ffrosen rocks, the decrease of washing<br />

intensity in the left part of the cuxves can<br />

be explained by the decelerati<strong>on</strong> of thawing<br />

velocity as the ice c<strong>on</strong>tent gxowa. Further<br />

increase of the ice c<strong>on</strong>tent to the right of<br />

the extreme is probably accompanied by fast<br />

weakening of structural links in the thawed<br />

n<strong>on</strong>-eroded layer. As a remlt, its thickness<br />

sharply decreases,and according to formula( 5)<br />

the density of heat flow into the rock and<br />

the thawing velocity increase. The same reas<strong>on</strong><br />

is for Sf growing at increasing the thawed<br />

rocks moisture in the range of high w<br />

values. The increase of the thawed rock erosi<strong>on</strong><br />

intensity ae their initial moisture c<strong>on</strong>tent<br />

is lowering to the left of the extreme<br />

w, %<br />

Fig.4 Correlati<strong>on</strong> between Washin Intensity<br />

( U ) of a) Loam Sands and %)Lome<br />

and their Initial Moisture C<strong>on</strong>tent( W 1:<br />

1 - in Thawed State; 2 - in Frozen State<br />

In natural c<strong>on</strong>diti<strong>on</strong>s of Ichuveem river valley<br />

(West Chukotka) the observati<strong>on</strong>s were<br />

c<strong>on</strong>ducted fox the earlier marked (Yerehov a.<br />

o., 1979) perculiaritiea of erosi<strong>on</strong> of frozen<br />

rocka of reticular cryotexture. The destructi<strong>on</strong><br />

of ice streaks at a direct c<strong>on</strong>tact with<br />

water flow waa faster than the thawing of<br />

rock aagregatee. The calculati<strong>on</strong>e show that<br />

to moment of full ice streaka thawing up to<br />

80 per cent of rock aqgregate volume remains<br />

in frozen state. Thanks to that the thawed<br />

rock, if it has water drainage, obtains the<br />

inherited fine-platy structure (fig. 5).<br />

Main technique for rock wanhinff is a hydrom<strong>on</strong>itor.<br />

Therefor ite productivity was detexmined<br />

during operati<strong>on</strong> by<br />

4<br />

ete having moet Prequently<br />

used parameters nozzle diameter is<br />

70-75 nun, pressure ia 0. -0.65 ma, water<br />

c<strong>on</strong>sumpti<strong>on</strong> i~ 500-550 m /h). When hydromining<br />

heavy dusty loam sand and broken Bt<strong>on</strong>e loam<br />

it was noticed t$at at increaefng the thawing<br />

depth from 2 to 25 cm there was steady TOductivity<br />

rise. The results of obsematf<strong>on</strong>e<br />

are expressed by the empirical formula:<br />

where P ie the hydrom<strong>on</strong>itor pSoductivity for<br />

the accumulated thawed rock,m-/h; h is the<br />

thawing depth, cm; Po , S axe empirical paremeters,<br />

reepectively equal to 50 and 15 for<br />

loam, 40 and 30 for loamy sand.<br />

Formula (7) is. valid for the thawinn: depth up<br />

to 25 em and for the rock of plastic c<strong>on</strong>sletansy.<br />

1419

hand.<br />

Pig. 5 ~ n ~ ~ e o ~ ~ ~ ~ ~ ~~~~~~~~~ y w ~ ~ i Q ~ 4<br />

af Loam Sand and Lo my ~ ~ op ~ ~ ~ ~ ~ @ ~<br />

~~Y~~ ~~~~~ ~ ~ & ~ e ~<br />

n v ~ e ~ ~<br />

The c<strong>on</strong>ducted reaearches allow to ohoose rati<strong>on</strong>al<br />

tecknklogical parameters of hydrowaahin&<br />

The necessary value of a day surface<br />

advance is determined <strong>on</strong> the base of initial<br />

requirements to the planned date of working<br />

out the placer of the given thickness, Then<br />

according to known calculati<strong>on</strong> methodm OP<br />

radiati<strong>on</strong> thawing (Pavlov,Olovin,1974) and<br />

formulae (5)-(7) they determine the optimum<br />

hydroerosi<strong>on</strong> rate which assurea sufficient<br />

intensity of mining operati<strong>on</strong>a and the best<br />

equipment productivity. After that the necessary<br />

quantity of hydrom<strong>on</strong>itor installati<strong>on</strong>s<br />

for the entire mining area is determined.<br />

The reseachers'a results are realized in the<br />

range of flow sheets of hydrostripping works<br />

which have been employed over the paBt five<br />

years at placer deposits of the North-East of<br />

the USSR at different minhg and geological<br />

and permafrost-climatic c<strong>on</strong>diti<strong>on</strong>e, Hydromining<br />

was carried out by stati<strong>on</strong>ary and selfpropelled<br />

hydrom<strong>on</strong>itor units (fig.6,7,8) and<br />

also by sprinkling apparatus.<br />

Depending <strong>on</strong> the type of a unit and the properties<br />

of eroding rocka watezj c<strong>on</strong>sumpti<strong>on</strong><br />

was changed from 100 to 630 m /h, pressure<br />

from 0.2 to 0.8 MPa. Before Btarting hydrostripping<br />

Operati<strong>on</strong>s the earthmoving machines<br />

removed moan and plant cover away from placer<br />

depo~lit surface, then waehed out periodically<br />

the rock layer thawed down by the oun radiati<strong>on</strong><br />

heat; the said rock being transported to a<br />

hydrodump by runninR by gravity or by dredge<br />

pumps. If mined placer depoeits c<strong>on</strong>tain plemty<br />

of large fragrnenta, their moving through<br />

transporting trenches and p1lj.n~ waa carried<br />

out by earthmoving equipment.<br />

Durlng hydrostripping operati<strong>on</strong>s next indices<br />

have been got:<br />

specific c<strong>on</strong>s pti<strong>on</strong> of electric power -<br />

O.R-2.5kW*h/m Y<br />

apecific water c<strong>on</strong>sumptJ<strong>on</strong> 3-6rn3/m3<br />

hydrom<strong>on</strong>itor productivity - 100-250m3/h<br />

It should be noted that the proposed technology<br />

starts to compete againat the most efficient<br />

c<strong>on</strong>venti<strong>on</strong>al f'low sheetn beginninp: from 3<br />

meter depth. The mom the mining depth the<br />

best will be the efficiency of the method(Samyshin<br />

a.o. ,1903).<br />

While developing open-pit deposits c<strong>on</strong>taining<br />

large rock fxagments the most effective are<br />

combined technoloKies FncludLing washing away<br />

a fine diapersed filler and transportinE tho<br />

remained rocks by earthmoving machines.<br />

Nowadaya the scales of hydromining use are<br />

quickly widening in the North-East of tho USSR.<br />

1420

1421

OFFSHORE SEAWATER TREATING PLANT FOR WATERFLOOD<br />

PROJECT, PRUDHOE BAY OIL FIELD, ALASKA, U.S.A;<br />

V. Manikianl and J.L. Machemehlz<br />

'ARC0 Alaska, Inc., Anchorage, Alaska, U.S.A.<br />

qexas A&M University, College Stati<strong>on</strong>, Tx., U.S.A.<br />

SYNOPSIS<br />

ARC0 Alaska, Inc., al<strong>on</strong>g with c<strong>on</strong>sulting engineers and c<strong>on</strong>tractors, planned, designed, and c<strong>on</strong>structed the largest civil<br />

engineering structure in the hlgh Arctic Beaufort Sea. This structure, a barge-mounted plant l<strong>on</strong>ger than two football fields and taller than an eleven-story<br />

building, treats water from the Beaufort Sea for pressurizati<strong>on</strong> of the Prudhoe Bay oil field through waterflooding, to enable the recovery of an additi<strong>on</strong>al<br />

160 milli<strong>on</strong> CU meters of oil. In the c<strong>on</strong>text of nati<strong>on</strong>al energy producti<strong>on</strong>, this corresp<strong>on</strong>ds to about ten percent of estlmated <strong>on</strong>shore undiscovered<br />

recoverable oil reserves in Alaska (Shell 1978, USGS 1975), and it is unlikely that the opportunity exists elsewhere in the US. to achleve with a single<br />

project the oil productivity of a Prudhoe Bay oil field waterflood.<br />

As Prudhoe Bay oil producti<strong>on</strong> passes 500 milli<strong>on</strong> cu meters, injected water (known as waterflood) is needed to offset the pressure lost as the oil is<br />

removed. The c<strong>on</strong>structi<strong>on</strong> of the Seawater Treating Plant with its innovative design provides the unique soluti<strong>on</strong> to the needs of industry and the local<br />

community.<br />

INTRODUCTION<br />

The barge-mounted Seawater Treating Plant is the first offshore facility<br />

in the high Arctic (Fig. 1). While the plant itself cost 385 milli<strong>on</strong> dollars,<br />

it is the cornerst<strong>on</strong>e of a two billi<strong>on</strong> dollar waterflood project which will<br />

enable ARC0 Alaska, Inc., Standard Alaska Producti<strong>on</strong> Company,<br />

Exx<strong>on</strong> Company, U.S.A. and other owner oil companies to recover<br />

through this sec<strong>on</strong>dary recovery system the additi<strong>on</strong>al 160 mllll<strong>on</strong> cu<br />

meters ,from the Prudhoe Bay oil field of Alaska,<br />

I<br />

utfall<br />

tive<br />

iravel Berm<br />

larine Llfe<br />

Return<br />

tended<br />

useway<br />

:khead 3<br />

1<br />

N<br />

Daewoo, Korea was chosen as the fabrlcati<strong>on</strong> site for the 186 m l<strong>on</strong>g<br />

oceangoing barge and Seawater Treating Plant based <strong>on</strong> ec<strong>on</strong>omic<br />

c<strong>on</strong>slderati<strong>on</strong>s and a study of available shlpyard facilities. The<br />

fabricati<strong>on</strong> started <strong>on</strong> January 4, 1982 and was completed in nineteen<br />

m<strong>on</strong>ths <strong>on</strong> July 8, 1983. The barge was then towed 6,500 km to<br />

Prudhoe Bay to colncide with the 1983 summer open water sealift<br />

period, a short four- to six-week stretch when the ice floes recede and<br />

ships can get to Prudhoe Bay. The platform was positi<strong>on</strong>ed and set <strong>on</strong><br />

a prepared offshore gravel foundati<strong>on</strong> (Flg. 2) <strong>on</strong> the seabed by<br />

c<strong>on</strong>trolled ballasting <strong>on</strong> August 22, 1963. After mechanical completi<strong>on</strong><br />

and startup activities in Prudhoe Bay, the plant was put in operati<strong>on</strong> <strong>on</strong><br />

June 14. 1984 (Fig. 3). At the end of its expected service life of 25 yrs,<br />

the barge-mounted Seawater Treating Plant can be removed from its<br />

site by de-ballasting and towlng.<br />

The design of the Waterflood Project involved challenges and<br />

opportunities for innovati<strong>on</strong> in the following areas: freeze protecti<strong>on</strong> and<br />

life support system, Intake and marlne life recovery system, ice criteria<br />

and protecti<strong>on</strong>; marine design, special materials and coatings, gravel<br />

foundati<strong>on</strong> design, causeway and fish passage breach, buried pipelines,<br />

and slope protecti<strong>on</strong>.<br />

Fig. 1<br />

14

FACILITY DESCRiPTlON<br />

To maintain an adequate water supply even in winter, when sea ice can<br />

form to thicknesses of two meters or more, the Seawater Treating Plant<br />

had to be located at .the end of the 1,200 m extensi<strong>on</strong> of an existing<br />

causeway, where water is 3.6 m deep (Fig. 1).<br />

Seawater flows directly into the treating plant intake reservoir through<br />

ports in the shoreward end of the platform. The intake ports are located<br />

below winter ice and above the seabed to assure a reliable water source<br />

of good quality with minimum intake of marine organisms. Flow is then<br />

directed through angled screens which are part of a bypass system. Any<br />

incoming fish are diverted by the screens and returned to the sea. An<br />

untreated seawater spray will then remove any other debris from the<br />

screens. This debris will be collected and returned to the Beaufort Sea<br />

through the 61 cm main outfall line.<br />

The seawater will then be pumped through in-line strainers to remove<br />

fibrous tundra particles. After straining, the seawater is heated to<br />

approximately 4.4T to prevent freezing. The filtered seawater then<br />

flows through deaerators for dissolved oxygen removal. Finally, the<br />

treated water is pumped through pipelines to <strong>on</strong>shore injecti<strong>on</strong> plants,<br />

where it is pressurized and sent to designated injecti<strong>on</strong> wells in the oil<br />

field.<br />

Processing removes suspended solids and dissolved oxygen for two<br />

reservoir operati<strong>on</strong>al requirments: (1) reducti<strong>on</strong> of oxygen present in<br />

seawater to reduce corrosi<strong>on</strong> to waterflood facilities, and (2) to eliminate<br />

the fines present in seawater that plug the pores within the reservoir<br />

formati<strong>on</strong>, in additi<strong>on</strong>, the processing provides heat for freeze protecti<strong>on</strong><br />

in the low-pressure pipeline system of 1,690 K Pa.<br />

The Seawater Treating Plant is protected from waves and ice by a<br />

’ gravel berm which is c<strong>on</strong>nected to the shore by a gravel causeway.<br />

Buried in the causeway are two large diameter supply pipelines that<br />

transport treated seawater to injecti<strong>on</strong> wells, c<strong>on</strong>duits carrying the power<br />

distributi<strong>on</strong> cables, and a fuel gas supply pipeline to the Seawater<br />

Treating Plant. The causeway also has a breach, spanned by a bridge,<br />

to minimize the impact of the causeway <strong>on</strong> free movement of marine<br />

life.<br />

The envir<strong>on</strong>mental design criteria are summarized in the following<br />

TABLE I.<br />

TABLE I<br />

Envir<strong>on</strong>mental Design Criteria<br />

with several levels of redundant power. On-board power generati<strong>on</strong> is<br />

provided to back up the 69 kV power brought into Seawater Treating<br />

Plant from the <strong>on</strong>-shore facilities. The backup equipment c<strong>on</strong>sists of two<br />

turbine generators (dual fuel, gas or diesel) and <strong>on</strong>e diesel generator.<br />

Any two generators can maintain minimum flow through the pipelines<br />

plus life support load at the facility, while any <strong>on</strong>e generator can<br />

maintain the “life support loads.”<br />

Due to the Arctic envir<strong>on</strong>ment a c<strong>on</strong>siderable freezing hazard exists if<br />

the discharge through the pipelines is significantly decreased. The<br />

insulati<strong>on</strong> <strong>on</strong> the pipelines would keep the water above freezing<br />

temperatures for <strong>on</strong>ly a limited period of time.<br />

The Seawater Treating Plant has been designed to maintain mlnimum<br />

flow through pipelines (usually 10% of design flow) to prevent freezing.<br />

As a last resort opti<strong>on</strong>, provisi<strong>on</strong>s have been made to evacuate the<br />

pipelines back into the ocean if the minimum flow could not be<br />

maintained.<br />

iNTAKE AND MARINE LIFE RECOVERY<br />

Due to the large physical dlmensi<strong>on</strong>s of the required integrated<br />

seawater intake, the early completi<strong>on</strong> of its design was a key element in<br />

determining the overall size of the barge. Project planning<br />

c<strong>on</strong>sideratl<strong>on</strong>s dictated that the barge dimensi<strong>on</strong>s be finalized early in<br />

the design effort. This, in turn, put a high priority <strong>on</strong> the intake design.<br />

The design of the seawater intake, however, turned out to be very<br />

challenging. First, it had to meet specific hydraulic performance<br />

requirements for a broad range of anticipated water Ieveis, sea states,<br />

and plant flow rates. Sec<strong>on</strong>dly, a serious ice particle ingesti<strong>on</strong> problem<br />

required soluti<strong>on</strong>. And, finally, very strlngent standards were established<br />

regarding minimizing harm to marine ilfe.<br />

Extensive analytical and physical modeling of the hydraulic performance<br />

of the eight hays comprising the intake was carried out. Ice problems at<br />

the intake included both the potential for Clogging of the intake ports by<br />

accumlati<strong>on</strong>s of ice rubble and the ingesti<strong>on</strong> of ice fragments into the<br />

intake. Design refinement, again with c<strong>on</strong>siderable model testing, was<br />

performed.<br />

The intensive effort that went into the design and testing of the marine<br />

life recovery system will ensure that the Seawater Treating Plant will not<br />

disrupt the native fishery in the Prudhoe Bay area. This fishery is reiled<br />

up<strong>on</strong> by North Slope natlves for subsistence. Large numbers of fish<br />

(arctlc and least cisco) feed during the summer in the Prudhoe Bay<br />

area. Alaska natives in coastal vlllages net these fish during the autumn.<br />

Design Ambient Temperature: - 4aoc<br />

The seawater intake was deslgned with low entrance velocities so that<br />

Water Depth:<br />

3.6 rn<br />

fish would not be drawn into the plant. Should fish swim or be drawn<br />

Seawater Treating Plant Dimensi<strong>on</strong>s: 186 m (L) x 46 m (W) x 35 m (H)<br />

into the intake ports, the system will recover and divert them back to the<br />

Mean Draft:<br />

3m<br />

ocean unharmed. This was achieved by designing a system that<br />

Design Storm Surge:<br />

+2.3 m, MLLW<br />

Design Wave Height: HSig= 3 1 m, H, - 4.6 m<br />

minimized thermal shock by specifying a maximum temperature rise in<br />

the fish diversi<strong>on</strong> system (0.55%) and by reducing mechanical damage<br />

Seawater Treating Plant Berm Height: + 8.7 m<br />

by avoiding any c<strong>on</strong>tact of fish with moving parts of pumps. The system<br />

SeawaterTreatingPlantBermSideSlope: 1V to 5H<br />

diverts fish from the main process flow bv the use of anoled screens<br />

I and with graduaily passages reduced cross<br />

secti<strong>on</strong>al returns<br />

them to the ocean with the help of let Dumps. Flsh behavior tests, usina<br />

live fish, were c<strong>on</strong>ducted before the systemdesignwasfinalized.A -<br />

A 69 kV power system serves the facility. Other facilities in the<br />

series of closely spaced bars, positi<strong>on</strong>ed in the intake ports, will prevent<br />

Seawater Treating Plant include emergency power generators, fired<br />

marine mammals (e.g., seals) from entering the seawater intake.<br />

heaters, elaborate fire protectt<strong>on</strong> and safety systems, maintenance<br />

shops, storage areas, offices, c<strong>on</strong>trol rooms and emergency living<br />

quarters with <strong>on</strong> board desalinati<strong>on</strong> plant for potable water, a waste<br />

water and sewage treating plant, recreati<strong>on</strong>al facilities, kitchen and food ICE FORCE AND RIDE-UP PROTECTION<br />

storage facilities.<br />

Ice Forces Criteria: The protective berm and the causeway were<br />

designed to resist ice loads of 655,000 kgliin m of perimeter for the<br />

Seawater Treating Plant berm and 402,000 kg/lin m for the causeway. ’<br />

FREEZE PROTECTION<br />

For the ice force design criteria see the following TABLE II.<br />

The Seawater Treating Piant is designed for an ambient temperature of<br />

- 48%. Life support systems (minimal lighting, heating system,<br />

elevators, fire protecti<strong>on</strong> and other basic facilities) have been designed<br />

1423<br />

\

0.5<br />

TABLE II<br />

Ice Force Design Criteria For Various Waterflood Activitles<br />

Causeway (From Shoreline to Dockhead 3)<br />

Ice Force: 1600 K Pa x,depth below MLLW x 110%<br />

Frost penetrati<strong>on</strong> assumed E m below seabed under existing causeway.<br />

Frozen Qravel shear strength for local shear: 192 K Pa<br />

Causeway Extensi<strong>on</strong> (From Dockhead 3 to Seawater Treating Plant)<br />

ice Force: 402.000 kgllin m<br />

Frost penetrati<strong>on</strong> assumed to be 1.8 rn below seabed.<br />

Seawater Treating Plant Berms<br />

Ice corce: northern and eastern exposure ~ 595,000 kgllin rn<br />

Ice Force: southern and western exposure - 402,000 kgllin m<br />

No frost penetrati<strong>on</strong> assumed below seabed.<br />

Seawater Treating Plant Hull<br />

Indirect ice load: N, E, W - 241 K Pa (223,000 kgllin rn)<br />

Direct ice load: South ~ 402,000 kgllin<br />

Gravel fill welght above MLLW - 1,642 kg/cu rn<br />

Gravel fill weight below MLLW 1,041 kglcu rn<br />

Slidinp Fricti<strong>on</strong> Cwfficient, GravellSoil +<br />

Ice Forces Transmitted to Hull: A two-dimensi<strong>on</strong>al finite element analysls<br />

was c<strong>on</strong>ducted to determlne pressure transmltted to the Seawater<br />

Treating Plant hull from migrating Ice loads Imposed through the<br />

protective berm in varylng c<strong>on</strong>figurati<strong>on</strong>s of frozen and thawed<br />

c<strong>on</strong>dltl<strong>on</strong>s. It was determined that the resultlng pressures <strong>on</strong> the hull<br />

were within the maximum allowables. The <strong>on</strong>ly direct exposure to the<br />

ice load was <strong>on</strong> the intake side of the Seawater Treating Plant. An<br />

integrated shear transfer system, including seven shear walls each 6 m<br />

high, 1 m wide, and 27 m l<strong>on</strong>g, were provided at the seawater Intake to<br />

transfer direct icp forces into the main hull structure.<br />

Ice Ride-Up Protecti<strong>on</strong>: Horiz<strong>on</strong>tal excursi<strong>on</strong>s by wlnter Ice sheets<br />

c<strong>on</strong>stituted an ice “over-ride’’ threat. All structures projecting above the<br />

surface of the berm or causeway were placed sufficiently distant from<br />

the ocean to be bey<strong>on</strong>d maximum anticipated Ice movements.<br />

MARINE DESIGN<br />

The Seawater Treating Plant al<strong>on</strong>g wlth Its Intake structure and all the<br />

support facilltles. was designed as an integrated facility with the barge.<br />

The plant c<strong>on</strong>slsts of a marlne hull and a superstructure. The hull is a<br />

doublewall and doublebottom c<strong>on</strong>structi<strong>on</strong>. The 13 m high hull is divided<br />

into several watertight compartments to provide strength as well as<br />

damage survivability.<br />

SPECIAL MATERIALS AND COATINGS<br />

Due to the corrosive and electrolytic properties of the aerated seawater,<br />

special materials and coatings were used In the waterflood project. This<br />

was supplemented by cathodic protecti<strong>on</strong> measures. Also necessary<br />

was a galvanic corrosi<strong>on</strong> protecti<strong>on</strong> design since a large corrosi<strong>on</strong><br />

potential existed due to use of various dissimilar metals.<br />

GRAVEL FOUNDATION DESIGN<br />

The Seawater Treating Plant foundati<strong>on</strong> c<strong>on</strong>sists of a prepared gravel<br />

pad <strong>on</strong> the sea floor inside the protective berm. The foundati<strong>on</strong> design<br />

was an area of c<strong>on</strong>siderable c<strong>on</strong>cern because very little geotechnical<br />

Informati<strong>on</strong> was available <strong>on</strong> the offshore Arctic. The foundati<strong>on</strong> also<br />

had to be built to very close tolerances ( f 2.5 cm) and required that the<br />

l<strong>on</strong>g term behavior of the foundati<strong>on</strong> be predictable.<br />

The top layer of the existing sea floor was silty material, This material<br />

was removed by dredging and replaced with gravel backfill. This<br />

provided a foundati<strong>on</strong> of known uniform compositi<strong>on</strong> and of predictable<br />

behavior, which gave a higher degree of c<strong>on</strong>fidence in its integrity. After<br />

placement of the backfill the foundati<strong>on</strong> gravel pad was brought up to<br />

final elevati<strong>on</strong> and leveled. This leveling operati<strong>on</strong> was carried out under<br />

water.<br />

Backfill placed after the Seawater Treating Plant was in positi<strong>on</strong> would<br />

generate a higher loading c<strong>on</strong>diti<strong>on</strong> than generated by the Seawater<br />

Treating Plant itself, which would result in an undesirable differential<br />

settlement between the center of the plant and the perimeter. Because<br />

of this c<strong>on</strong>siderati<strong>on</strong>, a gravel preload was placed at the perimeter of<br />

the dredged and backfilled area to prec<strong>on</strong>solidate the foundati<strong>on</strong><br />

materials and eliminate the differential settlement. The preload material<br />

was placed <strong>on</strong>e year prior to the Seawater Treating Plant installati<strong>on</strong>.<br />

Preloading was used in lieu of mechanical compacti<strong>on</strong> because<br />

settlement was expected to take place in the underlying materials.<br />

Mechanical compacti<strong>on</strong> would <strong>on</strong>ly c<strong>on</strong>solidate the gravel fill and not<br />

resolve the settlement problem.<br />

C<strong>on</strong>cern with otfshore permafrost caused extensive thermal modeling of<br />

the Seawater Treating Plant hull to be c<strong>on</strong>ducted. In summary, the fact<br />

that permafrost is very deep at the Seawater Treating Plant site (more<br />

than 30 m), allowed the Seawater Treating Plant hull to be uninsulated<br />

at its bottom surface. (The hull is, however, insulated at the upper<br />

porti<strong>on</strong>s of its vertical surfaces to llmit heat loss to the embankment.)<br />

CAUSEWAY AND FISH PASSAGE BREACH<br />

The berm surrounding the Seawater Treating Plant is c<strong>on</strong>nected to the<br />

shoreline with a gravel causeway, which provides a two-way vehicle<br />

access. Other major operati<strong>on</strong>al benefits of the causeway are the<br />

protectl<strong>on</strong> of, and ease of access to, the fuel gas line and the two largediameter<br />

seawater supply pipelines buried in the causeway.<br />

A fish passage causeway breach design was incorporated in the gravel<br />

causeway to intercept and allow fish passage through the causeway at a<br />

point where they are c<strong>on</strong>centrated. The 16 m wide waterway opening is<br />

protected <strong>on</strong> Its sides with sheet pile bulkheads driven into the seabed<br />

to an adequate depth below the worst case scour c<strong>on</strong>diti<strong>on</strong>. The 46 m<br />

l<strong>on</strong>g bridge structure spanning over the breach area will accommodate<br />

loaded Euclid 8-70 trucks with its load of 104,000 kgs, the set loading<br />

criteria for the bridge and the causeway. The bridge bottom of steel is<br />

7.6 m above the mean-low water elevati<strong>on</strong> to provlde freeboard above<br />

storm surge, wave and winter Ice sheets.<br />

SEAWATER SUPPLY PIPELINES<br />

The Seawater Treating Plant has two large diameter water pipelines to<br />

dellver treated seawater to the oil field for injecti<strong>on</strong>. These were<br />

insulated and buried within the causeway and are the f!rst major<br />

underground pipelines ever c<strong>on</strong>structed in the Arctic.<br />

Treated water for ARCO and the Eastern Operating Area is pumped<br />

through an insulated 101 cm line. Treated water for Standard and the<br />

Western Operating Area is pumped through an insulated 91 cm line.<br />

The ARCO line has a design rate of 190,OOO cu mlday and the<br />

Standard line has a deslgn rate of 160,000 cu mlday.<br />

Buried large diameter pipelines when subjected to Euclid 6-70 impact<br />

loads can be subjected to ovalling deflecti<strong>on</strong>s and excessive stresses.<br />

Calculati<strong>on</strong>s were c<strong>on</strong>ducted with special c<strong>on</strong>siderati<strong>on</strong>s to the pipeline<br />

sidefiil resistance. The procedure models the soil-pipe interacti<strong>on</strong>,<br />

characterizing the sidefill by an appropriate modulus value during winter<br />

or summer weather c<strong>on</strong>diti<strong>on</strong>s. It was determined that with the-available<br />

cover over the pipelines and under the design loading c<strong>on</strong>diti<strong>on</strong>s the<br />

maximum pipe deflecti<strong>on</strong>s were well below five percent of the diameter<br />

and the maximum pipe stresses below allowable values.<br />

1424

The Waterflood project was the first project requiring a decisi<strong>on</strong> <strong>on</strong> l<strong>on</strong>g Shell, 1978. Shell: Alaska holds 58 percent of future U.S. oil finds. Oil<br />

term slope protectl<strong>on</strong> in the Arctic Ocean. During its design, a and Gas Journal, November 20, 1978, p. 214,<br />

management decisi<strong>on</strong> was made to allow the exposed berm and<br />

causeway slopes to erode. The decisi<strong>on</strong> to treat all exposed gravel USGS, 1976. Water resources data for Alaska, water year 1975. U.S.<br />

surfaces as “sacrificial beaches” was based <strong>on</strong> a risk and ec<strong>on</strong>omic<br />

Geological Survey, Water-Data Report ALK.75-1, 410 pp.<br />

analysis in which various slope protecti<strong>on</strong> alternatives were c<strong>on</strong>sidered.<br />

The “sacrificial beach” c<strong>on</strong>cept allowed for estimated levels of beach<br />

erosi<strong>on</strong>, thus, requiring restorati<strong>on</strong> of the slopes after storms and <strong>on</strong> an<br />

“as-needed” basis. A program for future malntenance was found cost<br />

effective (i.e., substantially less expensive, <strong>on</strong> a “present worth basis”)<br />

than other alternatives. The project will be m<strong>on</strong>itored by the Prudhoe<br />

Bay Unit to ensure that the causeway and seawater treating plant can<br />

c<strong>on</strong>tinue to functi<strong>on</strong> adequately with limited maintenance or down time.<br />

CONCLUSIONS<br />

The Seawater Treating Plant was a unique challenge requirlng<br />

resoluti<strong>on</strong> of many complex problems. It was in many ways an<br />

unprecedented facility. We c<strong>on</strong>clude that:<br />

I. An offshore permanent industrial plant in the Arctlc has proven to be<br />

technically feasible.<br />

2. An Integrated process plant and oceangoing vessel can be a viable<br />

cost-effective Opti<strong>on</strong> in comparis<strong>on</strong> to c<strong>on</strong>ventl<strong>on</strong>al modular<br />

c<strong>on</strong>structi<strong>on</strong>.<br />

3. It can be an attractive opti<strong>on</strong> when a complete plant is to be<br />

fabricated as a single transportable unit for remote locati<strong>on</strong>s.<br />

4. This approach may be preferable for temporary process plant<br />

locati<strong>on</strong>s where marlne access is avallabie. or when a process piant<br />

has to be removed after completi<strong>on</strong> of its assignment.<br />

5. Process plant c<strong>on</strong>structi<strong>on</strong> and shipbuilding techniques can be<br />

integrated with proper planning of engineering and c<strong>on</strong>structl<strong>on</strong>.<br />

Experience gained <strong>on</strong> the Seawater Treating Plant project can be of<br />

tremendous value <strong>on</strong> slmilar projects in future.<br />

6. Underwater foundati<strong>on</strong>s for large industrial plants can be prepared<br />

to close tolerances cost effectlvely.<br />

7. A marine life recovery system can be designed without any moving<br />

mechanical parts coming in c<strong>on</strong>tact with the fish.<br />

E. A “sacriflcial beach” type of slope protecti<strong>on</strong> appears to be a viable<br />

alternative in the near-shore Beaufort Sea.<br />

9. Providing pipeline access to an offshore site from the shoreline, by<br />

way of burial of the pipeline within a causeway, appears to be an<br />

efficient soluti<strong>on</strong> to many design problems including those related to<br />

subsea permafrost.<br />

ACKNOWLEDGEMENTS<br />

The permissl<strong>on</strong> of the Prudhoe Bay Unit owners to publish this paper is<br />

gratefully acknowledged.<br />

Appreciati<strong>on</strong> is extended to the following c<strong>on</strong>tractors and c<strong>on</strong>sultants<br />

that participated in the design and c<strong>on</strong>structi<strong>on</strong> of the project:<br />

Alaska <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> C<strong>on</strong>structors, ARCTEC Engineering, Bechtel<br />

Petroleum, Daewoo Shipbuilding & Heavy Machinery, Dames & Moore,<br />

Harding - Laws<strong>on</strong>, Western Canada Hydraulic Laboratory, Woodward -<br />

Clyde.<br />

1425

DEVELOPING A THAWING MODEL FOR SLUDGE FREEZING BEDS<br />

C, J. Martel<br />

U.S. Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering Laboratory, Hanover, N.H. 03755.1290 USA<br />

SYNOPSIS This paper presents the development of a model that can be used to predict the<br />

thawing design depth of a sludge freezing A bed. sludge freezing bed is a new unit operati<strong>on</strong><br />

for dewatering sludges from water and wastewater treatment plants. Preliminary results obtained<br />

from a pilot-scale freezing bed indicate that this model is valid.<br />

INTRODUCTION<br />

One of the main problems in sludge management<br />

is dewatering. Typically, sludges resulting<br />

from wastewater treatment processes c<strong>on</strong>tain<br />

<strong>on</strong>ly 0.25 to 12% solids (Metcalf and Eddy,<br />

1979). Water treatment sludges may,c<strong>on</strong>tain as<br />

little as 0.1% solids before thickening and<br />

perhaps 2.5% after thickening (Fair et al.,<br />

1968). In most cases, direct disposal of<br />

these dilute sludges is unacceptable because<br />

of the cost of transportati<strong>on</strong>. In additi<strong>on</strong>,<br />

the liquid in the sludge could pollute surface<br />

or ground waters, so some method of dewatering<br />

is usually required before disposal. comm<strong>on</strong>ly<br />

used methods include filter presses, horiz<strong>on</strong>tal<br />

belt filters, centrifugati<strong>on</strong>, and drying<br />

beds.<br />

Selecti<strong>on</strong> of an effective &watering method<br />

for facilities located in cold regi<strong>on</strong>s can be<br />

especially,difficult. Because of the remoteness<br />

of many northern communities, parts and<br />

equipment are nst easily obtainable. Most of<br />

these communities are small, and skilled<br />

operators are scarce or not available. Therefore,<br />

complex mechanical dewatering methods<br />

are often undesirable. Simpler methods such<br />

as drying beds and lago<strong>on</strong>s can be but used<br />

they are inefficient in cold regi<strong>on</strong>s because<br />

of the shortness of the drying seas<strong>on</strong>. Large<br />

(1987). This unit operati<strong>on</strong> is called a sludge<br />

freezing bed. A c<strong>on</strong>ceptual sketch of a sludge<br />

freezing bed is shown in Figure 1. In<br />

essence, the bed c<strong>on</strong>sists of a large in-ground<br />

c<strong>on</strong>crete tank with a ramp <strong>on</strong> <strong>on</strong>e side and an<br />

overflow gate <strong>on</strong> the other. The ramp is needed<br />

to allow vehicle access for sludge removal<br />

and to distribute the incoming sludge evenly<br />

within the bed. The overflow gate is provided<br />

in case of accidental overfilling to and draw<br />

off supernatant during thaw. The bottom of<br />

the bed is under-drained with wedgewire screen<br />

or sand to allow drainage of the filtrate.<br />

~oth overflow and filtrate are collected in a<br />

sump and are pumped back to the plant. This<br />

c<strong>on</strong>cept is similar to the prototype freezing<br />

beda built at three small biological/chemical<br />

treatment plants in Sweden (Hernebring and<br />

Lagess<strong>on</strong>, 1986).<br />

To use the bed the operator would apply sludg<br />

in layers during the winter m<strong>on</strong>ths. Each<br />

layer would be applied as so<strong>on</strong> as the previous<br />

layer was frozen. Athe end of the freezing<br />

seas<strong>on</strong>, applicati<strong>on</strong>s would be terminated and<br />

the frozen sludge layers would be allowed to<br />

thaw. Under natural ambient c<strong>on</strong>diti<strong>on</strong>s, thawing<br />

is expected to proceed from the top downward.<br />

Most of the supernatant would be<br />

drained away by removing stop planks from the<br />

overflow gate. When thawing is complete, any<br />

storage facilities are often required to c<strong>on</strong>- remaining liquid would be drained away through<br />

tain the sludge over the l<strong>on</strong>g winter and the wedgewire or sand bottom. If necessary<br />

spring m<strong>on</strong>ths.<br />

the solids could be kept in the bed until th<br />

desired solids c<strong>on</strong>tent is achieved. The<br />

A more efficient method of dewatering sludges operator would then remove the sludge a with<br />

in cold regi<strong>on</strong>s is to use natural freeze-thaw. fr<strong>on</strong>t-end loader or other device. If suffi-<br />

Studies by Martel (1987) have shown that up to cient warm weather remains, the operator could<br />

2.0 m of freeze-thaw-c<strong>on</strong>diti<strong>on</strong>ed sludges can c<strong>on</strong>tinue sludge dewatering by using the freezbe<br />

dewatered by this process. Some northern ing bed as a drying bed.<br />

plants are already using natural freeze-thaw<br />

in their existing lago<strong>on</strong>s or drying beds.<br />

As c<strong>on</strong>ceived, a sludge freezing bed could be<br />

However, these operati<strong>on</strong>s are designed for<br />

used as a sole method of dewatering (Fig. 2a)<br />

drying sludge and are <strong>on</strong>ly deep enough to<br />

or in combinati<strong>on</strong> with other methods such as<br />

freeze 0.2 to 0.3 m of sludge. To optimize drying beds (Fig. 2b). If it were used as the<br />

the natural freeze-thaw process, a specially <strong>on</strong>ly method of dewatering, a storage facility<br />

designed unit operati<strong>on</strong> is necessary.<br />

would be needed to c<strong>on</strong>tain the sludge during<br />

the summer m<strong>on</strong>ths. This storage facility<br />

A unit operati<strong>on</strong> based <strong>on</strong> natural freeze-thaw could be a lago<strong>on</strong>, tank, or even a digester if<br />

c<strong>on</strong>diti<strong>on</strong>ing has been proposed by Martel<br />

excess capacity were available. If used in<br />

1426

““7<br />

This paper presents the development of a thawing<br />

model that can be used to predict this<br />

depth. Development of a freezing model can be<br />

found in Martel (1987).<br />

DEVEMPMENT OF THAWING MODEL<br />

1 E&- I<br />

combinati<strong>on</strong> with drying beds, the freezing bed<br />

would be designed to handle the winter sludge<br />

producti<strong>on</strong> <strong>on</strong>ly. A freezing and drying bed<br />

combinati<strong>on</strong> is particularly attractive because<br />

both methods would be operating under optimum<br />

c<strong>on</strong>diti<strong>on</strong>s.<br />

The size of a sludge freezing bed depends <strong>on</strong><br />

the depth of 6ludge that can be frozen and<br />

thawed at the proposed site. The Lower of the<br />

two depths will be the limiting design depth.<br />

In permafrost areas the depth of thaw is<br />

limiting because of the short thawing seas<strong>on</strong>.<br />

Thawing proaeeds downward from the surface and<br />

inward from the walls of the freezing bed.<br />

When the sludge thaws, the solids separate<br />

from the liquid and settle <strong>on</strong> the underlying<br />

frozen sludge. The depth of this settled<br />

solids layer increases as thawing progresses.<br />

This layer acts as an insulati<strong>on</strong> between the<br />

warm ambient air and the frozen sludge, so the<br />

frozen sludge at the bottom of the bed will<br />

take l<strong>on</strong>ger to thaw than that at the top. The<br />

expected temperature profile in the bed during<br />

thaw is 6hown in Figure 3.<br />

In this development it is assumed that most of<br />

the supernatant will be removed as quickly as<br />

possible. This can be accomplished by removing<br />

the stop-planks as thawing progresses.<br />

Leaving the supernatant in the bed decreases<br />

the thawing rate because of the added water<br />

layer.<br />

Thawing occurs as a result of warm air passing<br />

over the settled solids layer and of solar<br />

radiati<strong>on</strong>. The rate of heat transfer into the<br />

frozen sludge mass by both of these mechanisms<br />

must equal the rate of energy gain during the<br />

phase change from solid to liquid states.<br />

Thus, an energy balance per unit area at the<br />

solids/air interface yields<br />

1427

+<br />

Qriglnal<br />

Depth<br />

Y Thawed Sludae<br />

A Settled Sludqe<br />

Another energy balance relati<strong>on</strong>ship can be<br />

obtained across the settled sludge layer. In<br />

this case the rate of heat transfer by c<strong>on</strong>ducti<strong>on</strong><br />

across the layer must also equal e. The<br />

rate of heat transfer by c<strong>on</strong>ducti<strong>on</strong> (q,) can<br />

be calculated from<br />

Prevlously Frozen<br />

Sludge Layers<br />

Fig. 3.<br />

Assumed temperature profile during thaw<br />

where q and q, are the rates of heat transfer<br />

C<br />

by c<strong>on</strong>vecti<strong>on</strong> and radiati<strong>on</strong> respectively, and<br />

e is the rate of energy gain during the phase<br />

change.<br />

The rate of heat transfer by c<strong>on</strong>vecti<strong>on</strong> (9,)<br />

can be expressed as<br />

where is the average c<strong>on</strong>vective heat transfer<br />

coefficient (W/m2.'C) , A is the surface<br />

area (m), Tat is the average air temperature<br />

during thaw ("C) , and TIsa is the average temperature<br />

of the settled solids at the air interf<br />

ace ( 'C) .<br />

The rate of heat transfer by solar radiati<strong>on</strong><br />

(9,) can be expressed as (Krieth, 1973)<br />

where Kss is the thermal c<strong>on</strong>ductivity of<br />

thawed sludge (W/m.*C), A is the thickness of<br />

the settled sludge layer, and Tf is the freezing<br />

point of sludge. Thus an energy balance<br />

across the settled sludge layer yields<br />

Neither Eq. 5 nor 7 is very useful because Tsa<br />

is difficult to determine. However, Fsa can<br />

be eliminated by solving Eqs. 5 and 7 for the<br />

temperature differences and adding them. This<br />

procedure results in the following expressi<strong>on</strong><br />

in terms of Fat and Tf <strong>on</strong>ly:<br />

Solving Eq. 0 can be simplified by assuming<br />

that the ratio of A to y is c<strong>on</strong>stant for all<br />

depths. Then A can be expressed as By, where<br />

8 is the fracti<strong>on</strong> of deposited solids per unit<br />

depth of thawed sludge. Substituting this<br />

expressi<strong>on</strong> into Eq. 8 and separating variables<br />

results in<br />

where a is the solar absorptance of the sludge<br />

(dimensi<strong>on</strong>less), T is the transmittance of the<br />

roof (dimensi<strong>on</strong>less), and 7 is the average<br />

insolati<strong>on</strong> during thaw (W/mZ).<br />

The rate o f energy gain during melting can be<br />

calculated from<br />

At t = 0, y = 0, and at t = tth (time to<br />

thaw), y = Y (the total depth of thawed<br />

sludge). Integrating between these limits and<br />

solving for tth results in the following equati<strong>on</strong><br />

for predicting thawing time:<br />

where pf is the density of frozen sludge<br />

(kg/mz), L is the latent heat of fusi<strong>on</strong><br />

(W.h/kg), and dy/dt is the rate of change in<br />

the positi<strong>on</strong> of the melting sludge interface.<br />

Substituting Eqs. 2, 3, and 4 into Eq. 1<br />

results in the following energy balance rclati<strong>on</strong>ship:<br />

Eq. 10 can be solved for Y, the thawing design<br />

depth, by using the quadratic formula. This<br />

formula produces two values of Y but <strong>on</strong>ly the<br />

positive value is useful for engineering purposes.<br />

From this formula,<br />

1428

values of p f and L were assumed to equal those<br />

of water, i.e. 917 kg/m2 and 93 W.h/kg<br />

respectively. The transmittance (7) of the<br />

transparent fiberglass roof was 0.9 and the<br />

absorptance (u) of the sludge was assumed to<br />

be 0.9.<br />

VALIDATION<br />

To validate this model, 0.58 m of anaerobically<br />

digested sludge was frozen over the<br />

winter of 1986-87 in a pilot-scale freezing<br />

bed in Hanover, New Hampshire (Fig. 4). Thawing<br />

began <strong>on</strong> 18 March and was completed <strong>on</strong> 12<br />

May for a total thawing time (tth) of 1344 h.<br />

The average arnbient air temperature (!Fat) and<br />

insolati<strong>on</strong> (T) during this period was 7.7'C<br />

and 149 W/m2*h respectively. The calculated<br />

average c<strong>on</strong>vecti<strong>on</strong> coefficient was 12.9<br />

W/ma* 'C based <strong>on</strong> the relati<strong>on</strong>ship h = 5.7 +<br />

3.8 7 where v is the average wind velocity in<br />

m/a (Kreith and Kreider, 1978).<br />

The thermal c<strong>on</strong>ductivity of the settled sludge<br />

(Kss) was 0.20 W/m-'C according to measurements<br />

made in situ using a procedure developed<br />

by Atkins (1983). Drainage tests with this<br />

sludge indicated that 9 , the fracti<strong>on</strong> of<br />

settled solids per unit depth was 0.34. The<br />

freezing point (Tf) was found to be O'C<br />

(Martel, 1987). Since sludge is mostly water,<br />

Substituting these values in Eq. 11, the predicted<br />

depth of thawed sludge is 0.52 m, which<br />

is approximately 10% less than the actual<br />

thawed depth of 0.58 m. This small difference<br />

should not be significant for design. In additi<strong>on</strong>,<br />

the equati<strong>on</strong> predicted a lesser depth<br />

than the actual, which results in a mare c<strong>on</strong>servatively<br />

designed freezing bed.<br />

A comparis<strong>on</strong> of the 1/hc and 8Y/2KS,terms in<br />

Eq. 10 indicates that the latter has a greater<br />

effect <strong>on</strong> thawing time. The value of 8Y/2Kss<br />

is 0.493, which is 6.4 timea greater than the<br />

value of l&. To reduce the value of this<br />

term it is necessary to either reduce the<br />

settled solids fracti<strong>on</strong> (0) or increase the<br />

thermal c<strong>on</strong>ductivity (Kss). Although it would<br />

be difficult to increase the thermal c<strong>on</strong>ductivity,<br />

it can be prevented from decreasing by<br />

keeping the sludge saturated since water has a<br />

higher thermal c<strong>on</strong>ductivity than air. The<br />

settled solids fracti<strong>on</strong> could be reduced by<br />

occasi<strong>on</strong>ally removing the solids during the<br />

thawing period.<br />

The pilot-scale experiment dem<strong>on</strong>strated the<br />

beneficial effect of natural freeze-thaw. The .<br />

anaerobically digested sludge, which originally<br />

c<strong>on</strong>tained wnly 6% solids, was dewatered to<br />

40% solids after freeze-thaw. This represents<br />

an 81% reducti<strong>on</strong> in water c<strong>on</strong>tent. The sludge<br />

was easily removed from the bed with a fr<strong>on</strong>tend<br />

loader.<br />

CONCLUSION<br />

Natural freeze-thaw can effectively dewater<br />

sludges from most water and wastewater treatment<br />

facilities in cold regi<strong>on</strong>s. A new unit<br />

operati<strong>on</strong> called a sludge freezing bed has<br />

been developed that can utilize this process.<br />

Preliminary results indicate that the model<br />

presented in this paper can be used to predict<br />

the depth of frozen sludge that can be thawed<br />

naturally during the spring and summer. More<br />

research is being c<strong>on</strong>ducted to further validate<br />

this model.<br />

14829<br />

REFERENCES<br />

Atkino, R T (1983) .<br />

In-situ thermal c<strong>on</strong>ductivity measurements.<br />

Final Report for the State of Alaska. US<br />

Army Cold Regi<strong>on</strong>s <strong>Research</strong> and Engineering<br />

Laboratory, Hanover, N.H.<br />

Fair, C W, Geyer, J C t Okun, A D (1968).<br />

water and Wastewater Engineering, Vol. 2,<br />

John Wiley and S<strong>on</strong>s Inc., New York.<br />

Hernebring, C & Lagess<strong>on</strong>, E (1986).<br />

C<strong>on</strong>diti<strong>on</strong>ing of sludge by natural freezing<br />

(translati<strong>on</strong> from Swedish). Report No. 27,

Institute for Urban C<strong>on</strong>struc ti<strong>on</strong>, Dept. of Martel, C J (1987).<br />

Water and Sewage Technology, university of<br />

Develwpment and design of sludge freezing<br />

Lulea, Sweden.<br />

beds, Ph.D. Dissertati<strong>on</strong>, Colorado State<br />

Kreith, F (1973).<br />

University, Ft. Collins.<br />

Principles of Heat Transfer. 3rd Editi<strong>on</strong>, Wetcalf and Eddy, Inc. (1979).<br />

McGraw-Hill Inc., New York.<br />

Wastewater Treatment/DisposaL/Reuse. 2nd<br />

Kreith, F & Kreider, J F (19781. Editi<strong>on</strong>, McGraw-Hill Inc., New York.<br />

Principles of Solar Engineer ing, McGraw-Hill<br />

Inc., New York.<br />

1430

TEST OF THE SHALLOWLY BURIED WATER SUPPLY PIPE<br />

Meng, Fanjin<br />

Oil Field C<strong>on</strong>structi<strong>on</strong> Design and <strong>Research</strong> Institute of Daqing Petroleum Administrative Bureau, China<br />

SYNOPSIS<br />

In order to determine the proper buried depth for water supply pipes in cold regi<strong>on</strong>s<br />

the field full-scale tests were c<strong>on</strong>ducted in Daqing area for three winters. The temperatures<br />

at inlet and outlet of the pipe, the size of the melt ring and the ground temperatures at various<br />

points around the pipe were observed. The tests showed that the shallowly buried technique could be<br />

used in burial of water supply pipes. Based <strong>on</strong> the test resuls, 43 km water supply pipes were built<br />

in Daqing Oilfield with the buried depth of 1 m. No frost damage occured in three years.<br />

INTRODUCTION B) Water temperature<br />

Daqing is in cold regi<strong>on</strong>, where winter is l<strong>on</strong>g<br />

and the. ground is frozen as l<strong>on</strong>g as eight m<strong>on</strong>ths.<br />

The lowest air temperature is -25.1"C in m<strong>on</strong>th<br />

average and -39'C in minimum. The deepest frost<br />

penetrati<strong>on</strong> is 2:2 meters.<br />

The test was suggested based <strong>on</strong> the features of<br />

the water supply pipes and the actually productive<br />

c<strong>on</strong>diti<strong>on</strong>s in the oil fields.<br />

TEST CONDITION AND METHOD<br />

Water from different supply sources has different<br />

temperatures. C<strong>on</strong>sidering that the temperature<br />

of surface water is 0-1°C in the winter,<br />

and its amount is small, so it is not suitable<br />

to use surface water in the test. Ground water<br />

was used in the test and the water temperature<br />

is c<strong>on</strong>sidered to be 9'C.<br />

C) Soil property<br />

The soils in the test site are light loam and<br />

sandy soil. Their thermal c<strong>on</strong>ductivity is 14<br />

WIrn'K.<br />

Determinati<strong>on</strong>of the test parameters D) Pipe diameter<br />

The main purpose of this test was to investigate<br />

the behaviour of the water supply pipe that was<br />

buried above the lowest frost line and in different,c<strong>on</strong>diti<strong>on</strong>s,<br />

such as the pipe's length and<br />

diameter, water temperature in the supply inlet,<br />

flow and the property of the soil around the<br />

pipe, and to look for the allowable minimum<br />

buried depth of the pipe. The demands for this<br />

buried depth are: (a) water at the end of pipe<br />

should not be frozen during supply, (b) water in<br />

pipe should not be frozen in the allowable period<br />

of stopping water supply, Because it usually<br />

needs not more than 24 hours to maintain the supply<br />

pipe <strong>on</strong>ce, the time for stopping water supply<br />

in the test was decided to be 36 hours or<br />

more. Suitably buried depth is related with the<br />

pipe length and diameter, flow, water temperature<br />

and property of soil. These parameters were<br />

chosen as follows<br />

A) Pipe length<br />

In the oil field the supply stati<strong>on</strong>s' service<br />

radius is about 3 kilometers and the furthest<br />

point from the stati<strong>on</strong> is not more than 5 kilometers,<br />

am<strong>on</strong>g which the lengths of main pipes and<br />

branch pipes are 3.5 and 1.5 kilometers, respectively.<br />

Limited by test c<strong>on</strong>diti<strong>on</strong>, the length<br />

of test pipe was chosen as 80 meters.<br />

According to the practical situati<strong>on</strong> in the oil<br />

field, three kinds of pipes, 4114x4, 688.5~4<br />

and 660x5 mm, were used in the test.<br />

E) Flow<br />

The flow in most branch pipes is about 3 m'/h<br />

and a few of that about 1 m'/h. All tests,,were<br />

c<strong>on</strong>ducted at two stages, i.e., "great flow and<br />

"small flow" stage, In great flow stage, the<br />

test flows in the pipes of b60x5, m88.5xb and<br />

$114~4 mm are 2 , 3 and 4 mg/h, respectively,<br />

whereas in small flow stage, they are 0.2-0.6<br />

m'/h.<br />

F) Buried depth of pipe<br />

According to the standard, buried depth at the<br />

top of a pipe can not be less than 0.7 m and it<br />

is comm<strong>on</strong>ly designed lower than the maximum<br />

frost depth, that is 2.2 m in Daqing regi<strong>on</strong>.<br />

Buried depths (at the centre of a pipe) of test<br />

pipes were 1.5, 1.3 and 1.0 m for the pipes of<br />

660x5, 688.5~4 and 4114x4, respectively.<br />

Test method<br />

When the ground temperature around the pipes<br />

were near the minimum, let the water run through<br />

1431

~~ ~ ~ ~~ .<br />

~~<br />

the pipes with a designed value of flow so as to<br />

form a melting ring around the pipes. At the<br />

same.time, the soil temperatures around the pipes<br />

and air temperature were measured and recorded.<br />

As so<strong>on</strong> as the melting ring had been stable,water<br />

c<strong>on</strong>veyance should be stopped immediately, but the<br />

temperatures at various point around the pipes<br />

should be observed c<strong>on</strong>tinuously. The melting<br />

ring is c<strong>on</strong>sidered to be disappeared when the<br />

temperature at the pipe wall becomes zero "C.<br />

According to the observed data, the magnitude of<br />

the melting ring and the time from stopping water<br />

supply to the disappearance of the melting ring<br />

were calculated, and the melting ring was drawn,<br />

as shown in Fig.1.<br />

L<br />

Fig.1 The Shape of the Melting Ring.<br />

Around a Pipe<br />

The t.est results obtained in three winters during<br />

1978-1981 are shown in Table I.<br />

che variati<strong>on</strong> of ground temperature is slow the<br />

effect of short-term variati<strong>on</strong> of air temperature<br />

<strong>on</strong> the temperature in deep soil layer is<br />

small, where the melting ring is comparativity<br />

stable <strong>on</strong>ce it has been formed.<br />

Relati<strong>on</strong>ship between the magnitude of melting<br />

rinR and the elapsed time of its disappearance<br />

After water c<strong>on</strong>veyance has been stopped, the<br />

melting ring will decrease in magnitude and<br />

finally disappear. The shape and magnitude of<br />

the ring change with the pipe's positi<strong>on</strong> in the<br />

soil,<br />

If the pipe diameter, the flow and the buried<br />

depth are small, the ground temperature is low<br />

and the frost depth is great, the melting ring<br />

will be small in magnitude. In this case, the<br />

shape of the ring is a ellipse and the soil<br />

below the ring is frozen. It is easy for the<br />

melting ring to disappear after stopping water<br />

c<strong>on</strong>veyance, so that the pipe is easy to be<br />

frozen. For the pipes with greater flow and big<br />

diameter, the melting ring is usually in parabolic<br />

shape and c<strong>on</strong>nect with underlying unfrozen<br />

layer. In this case, the elapsed time of disappearance<br />

of the ring is comparatively l<strong>on</strong>g and<br />

it is not easy to be frozen for water in t,he<br />

pipe. The elapsed time menti<strong>on</strong>ed above is<br />

generally affected by the ground temperature,<br />

buried depth of the pipe and thermal c<strong>on</strong>ductivity<br />

and moisture c<strong>on</strong>tent of the soil. If the soil<br />

thermal c<strong>on</strong>ductivity, moisture c<strong>on</strong>tent and ground<br />

temperature are about the same, the greater the<br />

magnitude of the ring, the l<strong>on</strong>ger the elapsed<br />

time of disappearing the ring,<br />

TABLE I<br />

Observed Data in the Test<br />

Radius of Time for<br />

pipe B~~~~~ Flow melting the dis- Mean Ground temp. Depth of Mean Ground temp. Depth of<br />

diameter depth<br />

ring appear- air at the depth frost air at the depth frost<br />

(upper/ nace of temp. of the cen- penetra- temp. of the cen- penetralower)<br />

the ring<br />

tre of pipe ti<strong>on</strong><br />

tre of pipe ti<strong>on</strong><br />

mm m m'/h m h "C "C m "C OC m<br />

60x5<br />

60x5<br />

88.5x4<br />

88,5x4<br />

a8.5x4<br />

114x4<br />

114x4<br />

114x4<br />

114x4<br />

1.5 3.1 0.3/0.63<br />

1.5 0.24 0.25/0.6<br />

1.3 20 0.2810.75<br />

1.3 0.320.2/0.65<br />

1.3 0.17 0.2/0.5<br />

1 .o 3.25 0.28/0.55<br />

1 .o 0.23 0.2/0.3<br />

1 .o 0.33 0.2/0.3<br />

1 .o 0.19 0.15iQ.27<br />

110<br />

110.5<br />

500<br />

127<br />

192<br />

174.5<br />

48<br />

38<br />

253<br />

-11.3<br />

-8.0<br />

-11.3<br />

-10.6<br />

-16.9<br />

-11.3<br />

-15.4<br />

-10.6<br />

-14,O<br />

-2.3<br />

-1.1<br />

-4.3<br />

-2.8<br />

-2.4<br />

-5.4<br />

-5.3<br />

-4.7<br />

-4.0<br />

1.85<br />

1.67<br />

2.85<br />

1.65<br />

1.74<br />

1.85<br />

1.53<br />

1.65<br />

1.69<br />

-8.5<br />

-16 5<br />

07 .0<br />

-16.1<br />

-12.8<br />

-8.5<br />

-14.5<br />

-10.6<br />

-21.0<br />

.. ~<br />

. "<br />

-1.6 1.87<br />

71.1 1.72<br />

-1.8 1.92<br />

-2.7 1.7<br />

-2.3 1.79<br />

-3 1.89<br />

-5.3 1.55<br />

-4.5 1.66<br />

-4.9 1.77<br />

. . ."<br />

Influencing factors of the forminR of pelting ring Comparis<strong>on</strong> between observed data and calculated<br />

results<br />

The developing speed and magnitude of the melting<br />

ring are mainly determined by the ground tempera- The cornparisi<strong>on</strong> shows that the calculated reture,<br />

water temperature, the flow and the soil sults are<br />

in a good agreement with observed<br />

property. In the c<strong>on</strong>diti<strong>on</strong>s of c<strong>on</strong>stant buried data. The formula used in the calculati<strong>on</strong> is as<br />

depth and flow, the higher the ground and water follows:<br />

Eemperature, the greater the melting ring. When<br />

1432

where t-Water temperature at the outlet<br />

tl-water temperature at the inlet<br />

("C);<br />

("C);<br />

t "ground temperature at the depth of<br />

E. the depth of the centre of pipe ("C);<br />

D-the pipe's outer diameter (m);<br />

K-average coefficient of thermal c<strong>on</strong>ductivity<br />

of soils around the pipe<br />

(.Kcal/rn'h"C);<br />

C-specific heat of water (Kcal/kg"C);<br />

G-water flow in weight (kg/h);<br />

L-pipe length. (m).<br />

Example 1. Taking D=0.0885 m, G=3000 kg/h,L=80 m,<br />

t=-3'C, t-9"C, C=L and K-3 Kcal/m'h'C). Then,the<br />

calculated result is t-8.73"C.<br />

The difference between this result and observed<br />

data is <strong>on</strong>ly 0.03"C. According to Eq.(l), if the<br />

pipe length is 2000 m and water temperature at<br />

inlet is 7"C, the water temperature at outlet<br />

will be 2.72"C. The heat reduced from fricti<strong>on</strong><br />

is not c<strong>on</strong>sidered here.<br />

The cooling time (T) for water in the pipe from<br />

stopping supply to freezing can be estemated by<br />

in which,<br />

T = To t T, (2)<br />

Fig.2<br />

0.2-<br />

0.4-<br />

0.6-<br />

0.8:<br />

1-<br />

-2-<br />

* -<br />

B 4-<br />

x 6-<br />

R-<br />

10-<br />

20 -<br />

40 -<br />

60-<br />

80 -<br />

1001 ' k ' ; ' 5 ' .f ''lo 1'5 io io ' io';i9d<br />

S2Xl 00 %<br />

Determinati<strong>on</strong> of Parameters x and y<br />

Example 2. Given the following data to calculate<br />

the sustained time of stopping water supply, T,<br />

<strong>on</strong> the assumpti<strong>on</strong> that the water temperature is<br />

allowed to be lowered to OOC.<br />

pipe diameter D=0.114 m,<br />

Buried depth h=l m,<br />

Ground Temp. t =-4.3"C,<br />

g<br />

Moisture c<strong>on</strong>tent of soil n=13%,<br />

Specific gravity of soil=2.7,<br />

Specific heat of soil c=O.6,<br />

a=10 Kcal/m"C h,<br />

A2=2 Kcal/m"C h, and<br />

Water Temp. in beginning=S"C<br />

With the equati<strong>on</strong>s shown above, it is calculated<br />

that<br />

is the diameter of the melting ring (m),<br />

DT = 0.9 (m)<br />

To = 75.5(h),<br />

Thus, T = 128 (h).<br />

and T3= 52.5(h)<br />

a-the coefficient of thermometric c<strong>on</strong>ductivity<br />

of s~il (m'/h);<br />

h-buried dept'l of pipe centre (m),<br />

-6-15 Kcal/m"C h;<br />

A,-thermal c<strong>on</strong>ductivity of frozen soil;<br />

AI-thermal c<strong>on</strong>ductivity of melting soil;<br />

m-the depth of frost penetrati<strong>on</strong> (m);<br />

n-the volumetic moisture c<strong>on</strong>tent in<br />

volume of soil;<br />

x,y-parameters determined with Fig.2,in<br />

which;<br />

Atl--the difference between water temperature<br />

in beginning and ground temperature<br />

("C) and<br />

At2 -the difference between water temperature<br />

at last and ground temperature<br />

("C).<br />

CONCLUSIONS<br />

Any water supply pipe that is in agreement with<br />

<strong>on</strong>e of the following situati<strong>on</strong>s can be buried<br />

shallowly.<br />

(1) The water supply pipe system is composed<br />

of many branchs;<br />

(ii) The supply pipe system is<br />

without dead water in any<br />

the system;<br />

netted but<br />

secti<strong>on</strong> of<br />

(iii) The diameter of industria 1 or civil<br />

water supply pipe is equa 1 to or greater<br />

than 50 mm. the flow in i t is greater<br />

than 0.1 m3/s, and the water supply will<br />

not cut off,<br />

1433

According to the test reults, 43 kilometers<br />

water supply pipe was c<strong>on</strong>structed in Daqing Oil<br />

Field in 1983 with buried depth of 1 m. yo '<br />

frost damage has occured after three year s running.<br />

About 1000 kilometers water suppLy pipe<br />

has been buried shallowly in the soil field in<br />

recent years.<br />

1434

~ SHALE<br />

ROCK MECHANICS RELATED TO COAL MINING<br />

IN PERMAFROST ON SPITZBERGEN<br />

A.M. Myrvang<br />

The Norwegian Institute of Technology, NTH, 7034 Tr<strong>on</strong>dheim, Norway<br />

SYNOPS I S This paper describes the results from rock mechanics investigati<strong>on</strong>s in permafrost in<br />

the Svea Mine, Spitzbergen. The investigati<strong>on</strong>s features in-situ measurements as well as laboratory<br />

testing, for the determinati<strong>on</strong> of the in-situ virgin stress, in-situ strength of coal, general<br />

mechanical properties of thawed and frozen coal and shale and deformatl<strong>on</strong>al behaviour<br />

of the mine<br />

entries (tunnels) during actual mining.<br />

INTRODUCTION<br />

The Spitzbergen Islands Svalbard) are situated<br />

approximately between 77' and 80°N. Thanks to<br />

favourable ocean currents the average temperature<br />

is higher than in comparable areas in the<br />

Arctic, but still the permafrost penetrates<br />

down to depths of approximately 300 rn below<br />

surface. .'At present the Norwegian government<br />

owned company Store Norske Spitsbergen Kulkompani<br />

A/S (SNSK A/S) operateg 3 coal mines <strong>on</strong><br />

the island, but throughout the period from 1916,<br />

when SNSK A/S started its activities, the company<br />

has operated 8 mines. To date most of the<br />

mining operati<strong>on</strong>s have been in permafrost.<br />

The design of the mining methods was traditi<strong>on</strong>ally<br />

based up<strong>on</strong> experience and/or trial and<br />

error approaches. In the late sixties the<br />

first rock mechanics investigati<strong>on</strong>s were carried<br />

out. From the Late seventies quite extensive<br />

investigati<strong>on</strong>s have been initiated by the<br />

mine management, to get a better understanding<br />

of the mechanics associated with the coal mining.<br />

Rock mechanics programs have been carried<br />

out in the No. 3 mine, the No. 7 mine and the<br />

Svea Mine, with emphasis <strong>on</strong> the.determinati<strong>on</strong><br />

of in-put data for the design of the so-called<br />

room- and pillar system in the Svea Mine. This<br />

paper will c<strong>on</strong>centrate <strong>on</strong> the results from the<br />

investigati<strong>on</strong>s in this mine.<br />

THE SVEA MINE<br />

The Svea Mine is situated about 60 km SE of<br />

L<strong>on</strong>gyearbyen, which is the "capital" of<br />

Svalbard and the locati<strong>on</strong> of the two other<br />

mines in operati<strong>on</strong> (Fig. 1).<br />

The Svea camp is served by a small commuter<br />

airplane from the main airport in L<strong>on</strong>gyearbyen<br />

and also by snowmobiles during the winter<br />

seas<strong>on</strong>. Heavy equipment must preferably be<br />

brought in by ship during the shipping seas<strong>on</strong>, .<br />

but to some extent equipment can be brought<br />

in by bulldozer sledges or helicopter.<br />

As the other SNSK mines, the Svea Mine is also<br />

an adit mine situated in a valley side. The<br />

mining area is reached by a semi-horiz<strong>on</strong>tal<br />

adit (tunnel) from the valley side, and the<br />

coal seam itself is relatively flatlying.<br />

The coal seam is of tertiary age. The seam<br />

thickness is varying between approximately<br />

2 m and 5 m. I4ajor parts of the deposit<br />

c<strong>on</strong>tain intermediate bands of shale, which may<br />

have a thickness up to nearly 1 m. The roof<br />

is normally made up of fairly competent shales,<br />

while the floor in many cases c<strong>on</strong>sists of weak<br />

coal shale with bands of clay.<br />

Fig. 2 gives a simplified cross secti<strong>on</strong><br />

ing the lithology.<br />

show-<br />

. Fig. 1 Locati<strong>on</strong><br />

of L<strong>on</strong>gyearbyen<br />

and Svea Mines<br />

<strong>on</strong> Spitzbergen<br />

FAIRLY COMPETE : NT<br />

COAL<br />

BAND OF SHALE<br />

COAL<br />

WEAK SHALE<br />

Fig. 2<br />

Simplified Lithology<br />

1435

"<br />

--- - - - - - ""<br />

"1""""<br />

Fig * 5 Slmplif ied cross secti<strong>on</strong> showing<br />

successive, favourable caving<br />

Fig.3 Panel lay-out<br />

Each panel is first developed in a checkerboard<br />

pattern of rooms and pillars as shown <strong>on</strong> Fig. 4.<br />

Successive, c<strong>on</strong>trolled caving of the roof will<br />

give moderately, increased Load <strong>on</strong> the remaining<br />

pillars, allowing a major part of the coal<br />

in the pillars to be mined.<br />

The geometry, the mechanical properties of the<br />

roof rocks ana the in-situ stress c<strong>on</strong>diti<strong>on</strong>s<br />

are important factors in this c<strong>on</strong>necti<strong>on</strong>, Without<br />

caving of the roof, the remaining pillars<br />

will act as abutment for a "roof plate" which<br />

eventually can crush the pillars, or an-unc<strong>on</strong>trolled,<br />

violent caving will occur when the span<br />

is large enough, Fig. 6.<br />

t+<br />

Span<br />

Fig.6<br />

Situati<strong>on</strong> without successive caving<br />

Artificial<br />

support<br />

During the first several years of mining the<br />

operati<strong>on</strong>s will be in permafrost. The average<br />

year-round temperature of the coal and surrounh<br />

ing rocks will be approximately -4OC. The intake<br />

ventilati<strong>on</strong> air will always be above freezing<br />

temperature (artificially heated during the<br />

winter seas<strong>on</strong>). However, <strong>on</strong> its way to the<br />

mining panels the ventilati<strong>on</strong>s air will be<br />

cooled down, and in the mining panels the temperature<br />

will always remain below the freezing<br />

point as l<strong>on</strong>g as mining takes place in permafrost.<br />

Mining directi<strong>on</strong><br />

Fig.4 Simplified room-and-pillar mining<br />

With increasing overburden the mining will eventually<br />

take place in thawed ground.<br />

Rock mechanics data are vital in c<strong>on</strong>necti<strong>on</strong> with<br />

the design of the room- and pillar lay-out.<br />

While the initial design was carried out by<br />

experienced American c<strong>on</strong>sultants; the necessary<br />

1436

ock mechanics d ata were pr ovided by the Rock<br />

Mechanics Laboratory of the Mining Divisi<strong>on</strong>,<br />

the Norwegian Institute of Technology (now part<br />

of SINTEF, Divisi<strong>on</strong> of Rock and Mineral Engineering).<br />

TWO DIMENSIONAL STRESS MEASURE-<br />

MENTS (DOORSTOPPER)<br />

ROCK MECHANICS INVESTIGATIONS<br />

Throughout the years 1978-87 investigati<strong>on</strong>s<br />

have been carsied out during several periods.<br />

Both field and laboratory work has been included,<br />

featuring<br />

- In-situ rock stress measurements.<br />

- Sampling of material for laboratory investigati<strong>on</strong>s..<br />

- Laboratory investigati<strong>on</strong>s including uniaxial<br />

and triaxial strength determinati<strong>on</strong><br />

of coal and shale, determinati<strong>on</strong> of cohesi<strong>on</strong><br />

and fricti<strong>on</strong> angles and point load<br />

testing.<br />

- In-situ mapping of joints and fractures.<br />

- RQD (fracture index) determinati<strong>on</strong> of<br />

the roof rock based up<strong>on</strong> available dlam<strong>on</strong>d<br />

drill cores.<br />

- C<strong>on</strong>vergence measurements (change in roof<br />

to floor distance) during development of<br />

pandl s I<br />

The Rock Mechanics Laboratory (RML) uses two<br />

methods for in-situ rock stress measurements,<br />

Fig. I. In this case the two dimenti<strong>on</strong>al<br />

"doorstopper" method proved to be successful.<br />

The versi<strong>on</strong> used is developed by RML, and has<br />

been extensively used by RML for more than<br />

20 years in a large number of mines and tunnels<br />

in Norway, Sweden, Finland, Spain and Greenland.<br />

Fig.7<br />

1 A diam<strong>on</strong>d drill hole i5 drilled to required depth. Cort is<br />

removed and bottom of the hole 1s flattened.<br />

I<br />

2. A strain gauge rosette measuring three strains in three<br />

directi<strong>on</strong>s simultaneourly is cemented to the bottom of<br />

the hole<br />

3. The bottom is stress relieved by overc<strong>on</strong>ng. The<br />

corresp<strong>on</strong>ding strains are recorded by the rosette. When<br />

the elastic c<strong>on</strong>stants of the rwk are known. the stresses<br />

in a plane normal to the hole mi$ can be computed.<br />

Rock stress n-easuring methods<br />

To determine the in-situ stresses, measurements<br />

were carried out in the roof of entries at four<br />

different lccati<strong>on</strong>s (Fig. 8) , All measuring<br />

TRIAXIAL STRESS<br />

MEASUREMENTS<br />

TRIAXIAL STRESS<br />

MEASURBIIBMIS<br />

#Measuring hole<br />

"<br />

1. A diam<strong>on</strong>d drill hole is drilled to wanted depth. A<br />

c<strong>on</strong>centric hole with a smaller dlsmcter is drilled<br />

approximately 30 cm further.<br />

Fiq .8 Measuring set-up<br />

2. A measuring cell wntaming three strain rosettes is<br />

inserted, and the rosettes are glued IO the walls of the<br />

small hole.<br />

3. The small hole is overcored by the larger diameter bit,<br />

thus stress relieving the core. Thc corresp<strong>on</strong>ding strains<br />

are recorded hy the rosettes. When the clastic c<strong>on</strong>stants<br />

are known. the triaxial state of stress can be computed.<br />

sites were in permafrost. No practical difficulties<br />

were encountered due to the permafrost.<br />

For the core drilling heated water was used to<br />

avoid freezing problems.<br />

Assuming that the vertical stress is governed<br />

by the weight of the overburden (verified as<br />

the normal situati<strong>on</strong> by numerous measurements<br />

throughout the world) the following stress<br />

pattern was determined:<br />

1437

- The vertical stress is in accordance with<br />

overburden I. e.<br />

uv= p * g * h<br />

where p = density - 2500 kg/m 3<br />

g = accellerati<strong>on</strong> of gravity<br />

h = overburden<br />

By 300 m overburden uv = 7.5 MPa<br />

- The measured maximum horiz<strong>on</strong>tal principal<br />

stress uhl is parallel to the moun-<br />

tain side and is equal to or slightly<br />

higher than the vertical stress. At the<br />

innermost measuring site uhl = 12 MPa.<br />

- The measured minimum horiz<strong>on</strong>tal principal<br />

stress uh2 is normal to the mountain<br />

side and is in the order of magnitude of<br />

the horiz<strong>on</strong>tal gravity induced horiz<strong>on</strong>tal<br />

stress given by<br />

'h<br />

V<br />

= 1-v 'v<br />

where v = Poiss<strong>on</strong>s ratio<br />

It is very important and interestiny to note<br />

that even in these young tertiary rocks, there<br />

exist c<strong>on</strong>siderable "geological" stresses that<br />

superimpose the gravity stresses.<br />

C<strong>on</strong>siderable problems with so called floor heave<br />

and partly roof slabbing in some of the development<br />

entries are probably caused by high horiz<strong>on</strong>tal<br />

stresses normal to the axis of the entry<br />

combined with low strength of the rock, Fig. 9.<br />

F or the determinati<strong>on</strong> of in-situ strength of<br />

coa 1 a test axea pillar that showed quite heavy<br />

surface spalling and slabbing was selected. This<br />

indicates that the pillar stress is close to or<br />

over the in-situ strength of the coal. By taking<br />

stress measurements from the surface and into<br />

the pillar, the stress values will give an indicati<strong>on</strong><br />

of the in-situ strength. Fig. 10 shows<br />

the measured stresses as a functi<strong>on</strong> of hole<br />

depth.<br />

v) VI 15-1<br />

Q<br />

SUBBING AND<br />

WALLING FROM *<br />

THE SURFACE<br />

J<br />

HOLE<br />

CORE DISCING ' "1<br />

AND FRACTURING<br />

DEPTH M -<br />

Fig.10 Measured<br />

strength<br />

stress as functi<strong>on</strong> of hole<br />

Fiq.9<br />

Pillar pinches<br />

the soft floor<br />

Floor heave and roof spallinq<br />

Floor heave is caused by bucklinq due to hiqh<br />

horiz<strong>on</strong>tal stress or sqeesing due to nillar<br />

penetrati<strong>on</strong> in the floor. The stiffer coal<br />

pillar pinches the soft floor causinn the floor<br />

to heave. Roof snallinq is shear failure due tn<br />

hiqh horiz<strong>on</strong>tal stress.<br />

The first successful measurement was taken at a<br />

hole depth of 3 m. Measurements at shallower<br />

depth were not possible due to core discing and<br />

fracturing. This indicates higher vertical<br />

stress near the surface of the pillar as would<br />

be expected, and that the stress here is Close<br />

to the in-situ strength of the coal. The highest<br />

measured value is 11,6 MPa and for practical purposes<br />

it can now be assumed that the in-situ<br />

strength of the coal is close to that value. The<br />

laboratory determined uniaxial compressive<br />

strength is 16.3 MPa (se Table 1 <strong>on</strong> next page).<br />

Sampling €or laboratory testing has been extsemely<br />

difficult, as both the coal and the shale<br />

disintegrates very easily. To obtain the best<br />

possible results, the laboratory testing should<br />

be carried out <strong>on</strong> frozen specimens, and the<br />

specimens should also be kept frozen a11 the<br />

time from the removal from the mine. The drillcoxes<br />

were therefore kept in insolated polyuretan<br />

cases in the mine. Up<strong>on</strong>departurethey were<br />

brought as hand baggage <strong>on</strong> theplane to Tr<strong>on</strong>dheim<br />

and immediately after arrival stored in a freezer<br />

with -4OC temperature. This proved to work<br />

out well, and the cores were still frozen up<strong>on</strong><br />

arrival. The cores were then rapidly prepared<br />

(cut with a diam<strong>on</strong>d saw) and again kept in the<br />

freezer until immediately before testing. Although<br />

this is not completely ideal, it is felt<br />

that the results are not very far from the real<br />

values. Table 1 shows the mechanical properties<br />

1438

of frozencoal and shale.<br />

TABLE I<br />

Mechanical data for frozen coal and<br />

shale (based up<strong>on</strong> cores drilled out<br />

in the mine<br />

Rock type Younqs<br />

modulus<br />

Poiss<strong>on</strong>s<br />

ratio<br />

Uniaxial<br />

compressive<br />

GPa<br />

V strength<br />

MPa<br />

Coal 10,o 0,35 16,3<br />

Shale 1 bedding 13,4 0,20 77,8<br />

Shale I I bedding 17,O 0,20 86,4<br />

Triaxial tests were carried out <strong>on</strong> thawed coal<br />

cored from blocks in the laboratory. The<br />

results are presented in Table If.<br />

TABLE 11<br />

Triaxial data for coal (thawed)<br />

Failure stress u1<br />

MPa<br />

C<strong>on</strong>fining stress u3<br />

MPa<br />

13,7 0<br />

47,7 4,9<br />

66,7 918<br />

80,4 14,7<br />

The uniaxial compressive strength is here<br />

13,7 MPa vs. 16,3 MPa for frozen coal, indicating<br />

that the frozen coal is slightly str<strong>on</strong>ger<br />

than the thawed coal. Fig. 11 shows the Mohr<br />

failure envelope for the coal. It will be noted<br />

that the envelope curve is not linear, which is<br />

the case for most rocks. For practical purposes<br />

in c<strong>on</strong>necti<strong>on</strong> with pillar dimenti<strong>on</strong>ing the comm<strong>on</strong><br />

Mohr-Coulomb failure criteri<strong>on</strong> is often<br />

used assuming a straight line envelope curve.<br />

gati<strong>on</strong>s is that the obtained values coicide<br />

well with values from coal fields other places<br />

in the world and that the Bermafrost as such<br />

does not seem to affect the material properties<br />

much.<br />

The results from the in-situ measurements and<br />

laboratory tests have been used by the c<strong>on</strong>sultants<br />

as in-put data in empirically and computer<br />

based design of the room- and pillar<br />

systems. This resulted in 5 m wide entries and<br />

crosscuts, leaving 24 m x 24 m pillars.<br />

A vital factor in the design is the ability of<br />

the roof rock to cave during pillar recovery.<br />

To get informati<strong>on</strong> about this several diam<strong>on</strong>d<br />

drill holes were drilled 50-60 m vertically<br />

upwards in the xoof, and the cores were mapped<br />

according to the so called RQD-system and also<br />

the Raith-Li-system.<br />

The RQD (Rock Quality Designati<strong>on</strong>) gives a<br />

measure of the fracturing of the rock mass,<br />

while the Raith-Li-system (developed mainly by<br />

the late professor Bj@rn Li, Norwegian Institute<br />

of Technology) in additi<strong>on</strong> also gives some indicati<strong>on</strong><br />

of the strength of the rock mass. Both<br />

systems rate the rock in classes from "very<br />

bad" to "very good". In this case both methods<br />

in general indicated that the first 10-15 m of<br />

the roof was "bad". This in turn indicates that<br />

the caving ability of the roof is good.<br />

Throughout the years from 1984 the development<br />

of the room- and pillar system has progressed.<br />

As menti<strong>on</strong>ed earlier, c<strong>on</strong>siderable problems<br />

have been experienced with floor heave and sometimes<br />

also spalliny from the roof. This is pro-,<br />

bably partly caused by high horiz<strong>on</strong>tal stresses.<br />

To map this more accurately, a c<strong>on</strong>vergence<br />

measuring program was started in late 1986.<br />

Fig.11<br />

Mohr failure envelope for coal<br />

A fitted straight line approach will give the<br />

following values for internal fricti<strong>on</strong> and<br />

cohesi<strong>on</strong>:<br />

- Internal fricti<strong>on</strong> angle Qi = 39,6'<br />

- Cohesi<strong>on</strong> c = 4,5 MPa<br />

A general c<strong>on</strong>clusi<strong>on</strong><br />

of the laboratory investi-<br />

EFFECT OF THAWING<br />

The intake ventilati<strong>on</strong> air to the mine is normally<br />

always above freezing point. During the<br />

winter seas<strong>on</strong> the air is artificially heated.<br />

The intake air is taken through the main adit.<br />

Throughout the years c<strong>on</strong>siderable stability<br />

problems have been experienced in the roof of<br />

the adit, as the roof shale gradually disintegrates.<br />

It is, however, not quite clear if this<br />

is due to thawing or a general effect due to<br />

exposure to air and/or humidity. It is known<br />

from other n<strong>on</strong>-permafrost localities around the<br />

world that some sedimentary rocks tend to<br />

disintegrate when exposed to air and/or molstur€.<br />

This is called slaking. In additi<strong>on</strong> the effect<br />

of high horiz<strong>on</strong>tal stresses may also cause the<br />

roof to spa11 or disintegrate.<br />

Normally, the roof was systematically rock<br />

bolted combined with steel net (Fig. 12a). In<br />

the main adit, the loosened chips of rock is<br />

collected by the net which would eventually<br />

bulge down by the weight as indicated <strong>on</strong> the<br />

figure. From time to time the net had to be<br />

opened to remove the debris. Because of this<br />

major parts of the adit is now supported by<br />

steel sets as indicated <strong>on</strong> Fig. 12b. Tests with<br />

shotcreate combined with rock bolts has proved<br />

to be quite successful (Fig. 12c). It seems<br />

that the thin layer of shotcreate seals the

CONCLUSION<br />

R@ck mechanics investigati<strong>on</strong>s in permafrost in<br />

the Svea Mine indicate that the mechanical<br />

properties of coal and shale as such do not<br />

deviate much from those determined under n<strong>on</strong><br />

permafrost c<strong>on</strong>diti<strong>on</strong>s other places in the world<br />

The uniaxial compressive strength is probably<br />

slightly higher in permafrost than under thawed<br />

c<strong>on</strong>diti<strong>on</strong>s.<br />

Rock bolting<br />

With net<br />

A<br />

Steel sets<br />

Fig.12 Different types of support used<br />

B<br />

Shotcreate<br />

wi4h rock bolts<br />

C<br />

rock from the influence of the air and a least<br />

delays the slaking process very c<strong>on</strong>siderably.<br />

This probably indicates that the deteriorati<strong>on</strong><br />

is more an effect of air/moisture than thawing<br />

of the rock, as it must be assumed that the<br />

rock behind the thin shotcreate layer will also<br />

thaw eventually. In some areas explorati<strong>on</strong> adits<br />

have been driven under the permafrost: and this<br />

has in many cases created quite serious water<br />

problems. Whereas "dykes" of ice with' c<strong>on</strong>siderable<br />

thickness can be seen in the permafrost<br />

z<strong>on</strong>e (and they normally not create problems),<br />

in the thawed z<strong>on</strong>e the ice will inevitably be<br />

watei with accompaning problems.<br />

Traditi<strong>on</strong>ally, the entries and adits follow the<br />

fluctuati<strong>on</strong>s of the coal seam. The entries can<br />

therefore easil be flooded as indicat,ad nn<br />

Fig. 13. When txe water reaches the pemafrost<br />

it can eventually also freeze.<br />

Problems with deteriorati<strong>on</strong> of the roof in the<br />

main adit of the mine may ox may not be due to<br />

thawing. Other factors like general influence<br />

from ais and/or moisture and high horiz<strong>on</strong>tal<br />

in-situ stresses are probably as important. The<br />

major problem when mining takes place under the<br />

permafrost is water. From a practical and rock<br />

mechanics point of view stable permafrost c<strong>on</strong>diti<strong>on</strong>s<br />

are therefore to prefer versus thawed<br />

c<strong>on</strong>diti<strong>on</strong>s.<br />

REFERENCES<br />

MyKVang, A & Utsi, J (1987).<br />

Evaluati<strong>on</strong> of in-situ strength of coal from<br />

stress measurements in mine pillars.<br />

Proceedings 22.th 1nt.<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> of Safety<br />

in Mines. Beijing, China. NOV. 1987.<br />

Myrvang, A (1983).<br />

Report c<strong>on</strong>cerning rock mechanics investigati<strong>on</strong><br />

in the Svea Mine.<br />

Report for SNSK A/S from the Rock Mechanics<br />

Laboratory, the Norweqian Institute bf<br />

Technology. Tr<strong>on</strong>dheimi Norway.<br />

Agapito, J F T (1983).<br />

Room- and pillar plan for the Svea Mine.<br />

Report for SNSK A/S from J F T Agapito &<br />

Associates Inc. Grand Juncti<strong>on</strong>, Colorado,<br />

USA.<br />

Roof<br />

Water<br />

Floor<br />

Fig.13<br />

The entries follow the fluctuati<strong>on</strong>s<br />

of the coal seam<br />

So both from an operati<strong>on</strong>al and a rock mechanics<br />

point of view, stable permafrost c<strong>on</strong>diti<strong>on</strong> is<br />

seemingly to prefer versus thawed c<strong>on</strong>diti<strong>on</strong>s.<br />

Experiences from mining in crystalline rocks <strong>on</strong><br />

Greenland also indicate that the stability and<br />

mechanical properties are noe much affected by<br />

the permafrost as such, but also here serious<br />

water problems have occured when going under<br />

the permafrost.<br />

1440

SETTLEMENTS OF THE FOUNDATIONS ON SEASONALLY FREEZING SOILS<br />

V.O. Orlovl and V.V. Fursovz<br />

lAll-Uni<strong>on</strong> <strong>Research</strong> Institute of Bases and Underground Structure, Moscow, USSR<br />

2Tomsk Civil Engineering Institute, Tomsk, USSR<br />

SYNOPSIS The development of vertical diaplacements of,foundatiom to be built <strong>on</strong> seas<strong>on</strong>ally<br />

freezing heaving mila am analyzed in thie report. Results of l<strong>on</strong>g-term field testa with the<br />

we of shallow foundati<strong>on</strong>-plates carried out in the Western Siberia are assumed as a basie for<br />

this atuay.<br />

Ti11 the present time it was not paid much attenti<strong>on</strong><br />

to ageaific pmpsrtiee and to pmcedum<br />

of seas<strong>on</strong>ally freezing soils testing, that<br />

ie w problem of deformati<strong>on</strong> development du-<br />

-%awing of seae<strong>on</strong>ally fzwezing aoila aa<br />

wel a% BSgn-variable defomti<strong>on</strong>e occuring at<br />

l<strong>on</strong>g-term seas<strong>on</strong>al freezing and thawing of 80-<br />

ils axe studied unauffiaiently. Soluti<strong>on</strong> to<br />

this problem was <strong>on</strong>e of the aim# of the investigatiow<br />

undertaken in Tomsk (Siberia) dealing<br />

with vertfoal diaplaoemsnts of ahallow foundatiom<br />

which warn carried out dur;ing the last<br />

8 years <strong>on</strong> experimental eitee with etr<strong>on</strong>gly<br />

heaved Boils.<br />

At experlmsntal site the aeae<strong>on</strong>ally freeaing<br />

layer c<strong>on</strong>sisted of quaternary loam depoaita.<br />

The upper soil layer c<strong>on</strong>eiated of hardplaatic<br />

and softplaefic low up to 1,2-lr5 m in thickness<br />

which were underlain by soils having the<br />

c<strong>on</strong>sistence ranging from softplastic to yieldplastia.<br />

The groundwater table was 1,8-2,8 m<br />

below the ground aurfaoe, On the whole the soils<br />

wre represented by water-eaturated soft<br />

silty lo-.<br />

In the teete there were used xeinfom c<strong>on</strong>crete<br />

foundati<strong>on</strong>-plates of an area of 1 2whioh<br />

transmitted pressure to the eoil of 0; 0,1;0,2<br />

and 0,3 MBa reapectively. The foundatiowplertee<br />

were imtalled at a depth of 1 ,O and 1,5m<br />

while the seaa<strong>on</strong>al freese and thaw norm depth<br />

ma equal to 2,2 m. The side faoea of the foundati<strong>on</strong>-plates<br />

were isolated from the effect of<br />

tangent fmat-heave forces, therefore during<br />

the teeta the faundati<strong>on</strong>-plates w%re displaced<br />

<strong>on</strong>ly as a meeult of seas<strong>on</strong>al freezi~-thawing<br />

of soil8 beneath their undercride level.<br />

The analyse of teating reeulte allowed to draw<br />

c<strong>on</strong>clwi<strong>on</strong>a aa to vertical diaplacements of the<br />

foundati<strong>on</strong>-platee depending <strong>on</strong> the l<strong>on</strong>g-term<br />

seas<strong>on</strong>al freezing and thawing of ~ofls and the<br />

ressure transmittea to them.<br />

enloaded foundati<strong>on</strong>-platee (bo) were heaved<br />

praotioally simultaneously with the beginning<br />

of soils freezing beneath their underside level<br />

and had the maximmum dieplacements resulted<br />

fmm the effect of heaving soils deformatioae<br />

(hfo=hfmax), After thawing of soils they wedescended<br />

to the initial positi<strong>on</strong> and their 8ettlements<br />

were equal to their elevati<strong>on</strong><br />

at soils heaving (S =h 1, Dieplacements of<br />

the Loaded founbti8n-flates (hfo) were leea<br />

than the unloaded <strong>on</strong>ee (O

I<br />

Fig.1 Vertiaal displacements of the foundati<strong>on</strong> F,during freezing and thaning of aoile<br />

1 - foundati<strong>on</strong> ; 2 - surface mrk; .3- depti; of eeae<strong>on</strong>al freezing and thawing<br />

greesive compacti<strong>on</strong> and strengthening of the freezing and the depth of the foundati<strong>on</strong> deesoil<br />

layer beneath the foundati<strong>on</strong> underaide<br />

pening respectively; c - the Eiler-maker<strong>on</strong>y<br />

level<br />

c<strong>on</strong>stant ; the d i w fmCti<strong>on</strong>*<br />

If to asaume that koefficient (k ) which cha- The result x- of oompariaoa between calculated<br />

mcterizea the changes in sec<strong>on</strong>dry settlement and experimentally determined values of aec<strong>on</strong>at<br />

l<strong>on</strong>g-term cyclic fpeezing equals to<br />

dary settlements of the founbti<strong>on</strong> having<br />

4<br />

1,5 m in depth and exerting <strong>on</strong> baae eoil~~ the<br />

Ki - -J$<br />

(31<br />

pressum of 0,2 MPa during the seven-year<br />

'<br />

teat are illuetrated by figure 2. The calculated<br />

values determined aocording to the abovethenthe<br />

experimentally determined relati<strong>on</strong>-<br />

menti<strong>on</strong>ea procream are accurate enough to<br />

ship of thie koefficient depending <strong>on</strong> number be used in praotioe.<br />

of gyules is expressed in feme of inverse Laboratory inveetigatlom of eoil defomatifuncti<strong>on</strong><br />

and is described by the following<br />

<strong>on</strong>e at freezing and thawing were carried out<br />

e quat i<strong>on</strong><br />

to ground the development of eec<strong>on</strong>dary aettlementa<br />

depending <strong>on</strong> the type of rjoil, preasu3.e<br />

Ki = +Br 1 (43<br />

<strong>on</strong> the foundatl<strong>on</strong>-plate and the number of<br />

freeze cycles.<br />

d<br />

The work of shallow foundati<strong>on</strong> was modelled<br />

where E: and E, - the relative sec<strong>on</strong>dary<br />

in the refrigerator camem with the use of<br />

settlements in the first and i - cyclse reepsctively;<br />

A,& -<br />

&<br />

a beat-insulting chute made of acrylic plaetic<br />

the parameters depenaing 500x500x700 m in size. The dimenat<strong>on</strong>e of the<br />

<strong>on</strong> the c<strong>on</strong>eisfence of soile; the preasure<br />

foundati<strong>on</strong>-plate model were determined <strong>on</strong> the<br />

transmitted to the soils and the relative<br />

asampti<strong>on</strong> of geometric similarity to foundadepth<br />

of the foundati<strong>on</strong> deepening in the eea- ti<strong>on</strong> moael.<br />

s<strong>on</strong>al freezing; layer.<br />

Linear wale of the model mas 1 : 10, that cord<br />

resp<strong>on</strong>ded to the frea of aquare-shaped plate<br />

Hence, the total sec<strong>on</strong>dary settlement (S,)<br />

eaualed to 100 m . The teate were c<strong>on</strong>duoted<br />

1L<br />

resulting from the repeated seas<strong>on</strong>al freeze- os undisturbed &mplas of soil blocka and<br />

thaw cyclea for ' . n -years may be determi- artificially prepared soil-bases bt .&r$i@ed<br />

ned from the equati<strong>on</strong> oompoeiti<strong>on</strong>, moisture c<strong>on</strong>tent density. and<br />

Testing procedure was aasumed to have in prind<br />

d ciple ELI analogy to field experime<br />

sn 91 E, (df - a) {n*k+ J k *'f(n+l I]}, (5) corporated static teat with c<strong>on</strong>sequent repea-<br />

where df and d - the depth of the seas<strong>on</strong>al<br />

1442<br />

ted cyclic freezing and thawing under preaau-<br />

%a<br />

The teste C<strong>on</strong>ducted in the chute<br />

<strong>on</strong> different

. 1 - foundati<strong>on</strong>; 2 3,4.5 - mrke at points 0; 0.5; 1 0; 1 54 6.7 - de th of aeaabnal<br />

freezing and thadng of soils <strong>on</strong> north and aouth de8 0) the foundaPi<strong>on</strong><br />

2<br />

4<br />

6<br />

8<br />

io<br />

12<br />

2 3 4 S 6 7<br />

PIg.3 Relati<strong>on</strong> between eec<strong>on</strong>dary eettlement (am)<br />

and number of cyalea at l<strong>on</strong>g-term eeam<strong>on</strong>al<br />

freeaing and thawing in a baee of the<br />

foundati<strong>on</strong> Fg (d - l,Sml P 012 ma)<br />

- 1 - experimental valuee: 2 - calculated<br />

value8 determined according to the fornula (5)<br />

Fig.4 Freeze-thaw cyclee<br />

1444

mates.<br />

The above c<strong>on</strong>clusi<strong>on</strong>a allow t o make an approeoh<br />

to the problem of utilizati<strong>on</strong> of seae<strong>on</strong>elly<br />

frozen @oil layer as a nature1 base of ethallow<br />

foundati<strong>on</strong>e <strong>on</strong> the basis of their oalculati<strong>on</strong>B<br />

<strong>on</strong> defomati<strong>on</strong>a.<br />

(IONCLUSIONS<br />

' Ut ie detemfned experimentally that a rate<br />

and mount of settlements of soila in bed of<br />

ahallow foundati<strong>on</strong>s et seas<strong>on</strong>al thawing may<br />

o<strong>on</strong>siderably surpaee the fort, i dei<strong>on</strong>nati<strong>on</strong>a<br />

caused by frost heaving o$s%a.<br />

2. The settlement8 during thawing of eees<strong>on</strong>ally<br />

freezing soil basee depend an the load<br />

tranemitted by foundati<strong>on</strong>s and inoreaee with<br />

the Load inczwaae.<br />

3* The vertical diaplacemente of shalLow foundati<strong>on</strong>s<br />

In the prows8 of l<strong>on</strong>g-term eeae<strong>on</strong>al<br />

freesing and thawing of soils are developed<br />

due to an increase in total amount of aec<strong>on</strong>dary<br />

eettlemenf for each yeax.<br />

4. The gmatest sec<strong>on</strong>dary eattlementa are obaewed<br />

after the firat f-thaw cycle of soil<br />

under a load; after the eec<strong>on</strong>d fmeze-thaw<br />

cycle they are reduced by 2-3 timea. In the<br />

aouree of l<strong>on</strong>g-term freese-thaw oyclea the<br />

trettlrment of the foundati<strong>on</strong> exhibits a trend<br />

to be st0 ped due to the progreesive ampacti<strong>on</strong><br />

of eoile %sneeth the foundati<strong>on</strong> underaide level.<br />

5. The relati<strong>on</strong>ship of change in the amount<br />

of sec<strong>on</strong>dary eettlement is expreaeed by an<br />

inveree functi<strong>on</strong> of the number of freeze-thaw<br />

oy01es.<br />

1445

REGULARITIES OF THERMAL AND MECHANICAL INTERACTION<br />

BETWEEN CULVERTS AND EMBANKMENTS<br />

N.A. Peretrukhinl and A.A. Topekbaz<br />

'IrSNIS Mintranastroy, Moscow, USSR<br />

2hstitute of Railway Eng., Khabarovsk, USSR<br />

SYNOPSXS Data ofl railway embankment ma track deformati<strong>on</strong>s in the limits of culvert8 uflder<br />

embauhwnts locati<strong>on</strong> sites, as we31 as a regular relati<strong>on</strong> of khe deformati<strong>on</strong>s menti<strong>on</strong>ed with<br />

seas<strong>on</strong>al verbical alternating displacements of: *he culvert secti<strong>on</strong>s, are presented in this report.<br />

Regularities of thermal and mechanical interacti<strong>on</strong> between culverts and frostsusceptible aoila<br />

sursoundfrrg secti<strong>on</strong>s and foundati<strong>on</strong>s of culverts revealed <strong>on</strong> the basis of lohg-term investi ati<strong>on</strong>s<br />

field c<strong>on</strong>diti<strong>on</strong>s and theoretical generaliaatf<strong>on</strong> 09 measumment results of c<strong>on</strong>structi<strong>on</strong>s feformati<strong>on</strong>s<br />

and soils temperature, are set forth, There are also some suggesei<strong>on</strong>a c<strong>on</strong>cerning the<br />

desigu of culverts and ernbmkment;q road secti<strong>on</strong>s looated at frostsusceptible soils.<br />

INTRODUCTION<br />

The Momati<strong>on</strong> c<strong>on</strong>cerning high deformability<br />

of railway track and highwas bed in the z<strong>on</strong>ea<br />

of culverts locati<strong>on</strong>s in permafrost and deep<br />

frost penetrati<strong>on</strong> regLoas have been adduced fa<br />

a number of publicati<strong>on</strong>s (Jumickis,1973; Liverovw,lYtI<br />

; N0vozhilov,l963; Peckover,l978).<br />

However, there are no 8uffSciently substaneiated<br />

data <strong>on</strong> causes and appropriate methods for<br />

preventi<strong>on</strong> of defomati<strong>on</strong>a. In c<strong>on</strong>necti<strong>on</strong> with<br />

activiziag of road c<strong>on</strong>structi<strong>on</strong> ia northern<br />

regi<strong>on</strong>s, the provisi<strong>on</strong> of railway track and<br />

highway bed eveness in the z<strong>on</strong>e8 of culverbs<br />

locati<strong>on</strong>s have become an urgent necessity.<br />

Tqereiore special hvestigati<strong>on</strong>s of deteformability<br />

and thermal re& of rallwey bed and<br />

culverta during freezbg-thawfag of soils,<br />

surrouuding culverts and their foudatioa8,have<br />

been carried out (Peret-, 1967, 1982,<br />

1983).<br />

INITIAL CONDITIONS<br />

Secti<strong>on</strong>s of various depth embanhente with culverts<br />

la bounds of a railwag, located in the<br />

regi<strong>on</strong>s 09 c<strong>on</strong>tbuoup wrmfrost. have been<br />

Fmbs.nhente near culverts at these secti<strong>on</strong>s<br />

have been c<strong>on</strong>structed of frostsusceptible<br />

soile, aameYy loems and gravel sands with amdy<br />

loam, layers of which alternate at some<br />

secti<strong>on</strong>s. The fill de th above the culverts<br />

v-ies Prom 1.3 to 4.8 m. soils of active<br />

layer are peat8 .of 0.5 thickness, undexlied in<br />

most cases by a1ternat;i.q layera of loam, sandy<br />

lo-, as well as pebble wlth gravel and<br />

sand, oftea aatuxated with peat. Soils of aotive<br />

layer aud embanhent, with the excepti<strong>on</strong><br />

of lowaolat aanas, used for upper part; of<br />

some embaulmeata, bel<strong>on</strong>g to the frostauaceptible<br />

<strong>on</strong>es by theix compositi<strong>on</strong> and moisture.<br />

Bedrocks presented by sandat<strong>on</strong>es and sanw<br />

clay-&ales, lie under 3-4 m depth. There are<br />

six culvexts wit- the embankment secti<strong>on</strong>s<br />

selected, includiag two rectangular culvgrts<br />

with aperburea of 'I .25 and 'l.5 m, two ovoid<br />

culverts of 2 and 2.5 m ad two cboular <strong>on</strong>es<br />

of 'l.5 and 2 m. AJ.1 culverts have been c<strong>on</strong>structed<br />

in 194.8-199 period. The foundati<strong>on</strong><br />

base of oulverts secti<strong>on</strong>s and headwalls had<br />

been embedded into permafrost at the depth oi<br />

24.2 m from the earth supface. However, during<br />

Savestigati<strong>on</strong>sl the permafrost surface was<br />

at/or lower the fouadatioa baoe level.<br />

INVESTIGATIONS TECHNIQUE<br />

Vertical displaoements of the tsaok, subwade<br />

and culverbs elemenljs haw been measured by<br />

means of technical levelling of marks located<br />

<strong>on</strong> the rail head and ernbanbent shoulder above<br />

culvert, <strong>on</strong> both sides of the latter at 2* 4,<br />

6,8,20--30..1l distance from its axis, aa wel as<br />

<strong>on</strong> each secti<strong>on</strong> ends and he ads of culvert<br />

Bench marks made up of metallic rob and located<br />

bey<strong>on</strong>d the embankment limits, were embeaded<br />

bat0 permafrost at the depth of 2-2.5 times<br />

greatex than a local active layer tuckness.<br />

A part of the bench mark roads within<br />

the active leyer was enclosed Frrto a vhil<br />

chloride tube an8 a space between the rod and<br />

tube walls was filled with a cup grease.<br />

To measure the temperature near culverts 40<br />

cased holes of 0.7 to 7.7 m depth were bored<br />

and by electric copper resistance thermometer<br />

sets equipped (Pig.1). Themmeters were located<br />

al<strong>on</strong>g the height with 0.2 up to l m iatervalse<br />

More than. half of all the holes were 10-<br />

cated at the mctanguLar reinforced c<strong>on</strong>crete<br />

culvert with I .5 m a erture. Here holes are<br />

looated al<strong>on</strong>g the cufvert; axis and three lines<br />

parallel to the track and situaiied at the<br />

shoulder, the embadaneat slope and the slope<br />

base. Tbe holes near the rest of culverts were<br />

located <strong>on</strong>ly at points which are significant<br />

by the thermal mgh. ElectrZcal resistance<br />

of thermometers was measmd by a dhwct-current<br />

bridge. Mewurements erxor, pansfered Ftl<br />

the temperature, amounted to 4.2 C.<br />

1446

the culvert secti<strong>on</strong>s rise. During the whtef<br />

period values of the secti<strong>on</strong>s riae of the rectangular<br />

culvert;^, located under 3.6 and 4 m<br />

high embanbents, c<strong>on</strong>stituted from 63 to 77<br />

of the humps total height <strong>on</strong> embankment surface<br />

above cuJ.vert;t;8, i.e. the main part of the<br />

humps height.<br />

r I I I I I I -1<br />

550<br />

Fig.1. Boles with Thermometers Locati<strong>on</strong> and<br />

temperature Pield withFu a Z<strong>on</strong>e of 1.5 m qerture<br />

Culverti <strong>on</strong> Datutu of 27 Nov Measurement at<br />

I- Termometem, 2- Culvert<br />

Measurementswere c<strong>on</strong>ducted m<strong>on</strong>thly during the<br />

period changing from <strong>on</strong>e whter seas<strong>on</strong> to four<br />

ye axe<br />

VERTICAL DI8PLACEMENTS<br />

!the sail track, the embatihent upper p&<br />

above the culverts and all secti<strong>on</strong>s of the<br />

latter were defoxmbg during the whole obser<br />

vati<strong>on</strong> period; Le. they rose in the th<br />

of<br />

soil fxeezhg and subsided just a8 soil thawag.<br />

Under these c<strong>on</strong>diti<strong>on</strong>s, in wiaimx there<br />

appeared humps <strong>on</strong> the subsade swam above<br />

culverts reaulthng in formati<strong>on</strong> of track loa-<br />

,gitudal gradients, the algebraic dilifferenoe of<br />

which above culverts ran up to 0.001-0.012 within<br />

adjacent 4-5 m l<strong>on</strong>g track secti<strong>on</strong>8.<br />

Accodhg to current standards such Ustoxti<strong>on</strong><br />

of the track profile is c<strong>on</strong>sidered as an -admissable<br />

<strong>on</strong>e even for a train speea up to 50<br />

Wh<br />

At the beginning of I winter perha (October-<br />

November), before a culvext secti<strong>on</strong> rising<br />

start, the main cause of humps occwnce <strong>on</strong><br />

the embankment surface and a corresp<strong>on</strong>ding distorti<strong>on</strong><br />

of the track l<strong>on</strong>gitudhal profile<br />

above the culvert.8 is different value of froat<br />

heaving of embankment soile above culvert and<br />

at some dietance fxom the latter. Such differeace<br />

is c<strong>on</strong>diti<strong>on</strong>ed by simultaneous soil freezing<br />

above the culvert, from the embanlanenk<br />

amace and from the culvert opening. As can<br />

be seen at Fig.2, during that period the-embanhent<br />

surface rise above culvert is mom<br />

intensive (curve I ), than that at the distance<br />

of 30 m from the culvert axis (cume 2). After<br />

complete soil free~ing above the culvert (Decemberdanuary)<br />

the rise of embankment surface<br />

and accorajngly railwqy track not ceased but<br />

Lasted up to April (see Figm2).Takhg into 8ccount<br />

the approximate equality of rise values<br />

of both, embailanent surface above the culvert<br />

and secti<strong>on</strong>s of the lakter (cumre 3), <strong>on</strong>e can<br />

come to a c<strong>on</strong>alusi<strong>on</strong> that the humps occurence<br />

<strong>on</strong> the track at that period is c<strong>on</strong>ati<strong>on</strong>ad by<br />

c<br />

r'<br />

,1447<br />

Fig.2. Use of embalmen* Surface and gecti<strong>on</strong><br />

of 1.25 m apertues Culvert: I- Fill above CULverb,<br />

2- Embadanent at Distance of 30 m from<br />

Culvert, 3- Culvert secti<strong>on</strong><br />

Besides seas<strong>on</strong>al displacemeats, from year to<br />

year, residual uneveme8ee~ above all the culvert<br />

under investigati<strong>on</strong> acoumulatea. Thw<br />

there, for the two yearst the bump height L- '<br />

creased by 47 mm above an <strong>on</strong>e of culverts. As<br />

a c<strong>on</strong>eeguence of this the worst Wference of<br />

local gradients of the track l<strong>on</strong>gitudLnal pmfile<br />

above the culvert6 appeared at the end of<br />

the soil freezug period, when maiaual humps<br />

were increasing due to seas<strong>on</strong>al humps occu- *<br />

rence. There were no humps <strong>on</strong> the track 8urface<br />

above a culvert, located under 8 m high<br />

emb-nt Accor to the data obtained by<br />

other investigatox~~~erov~,,~, ) humps<br />

above ccilve&8, stipulated 'by irregular freezing<br />

of embankment soila, not emerge, if the<br />

embanlunent height is equal or Ughex 5 m and<br />

*he fill thickness above %he culvert; is more<br />

then 2.3 m.<br />

THl$RUG IlEGIME<br />

Analysis of temperatwe measurement results d-<br />

Lowed to reveal tha9 soS1,sumounding culvert;,<br />

begins to freeze earlier and freezes more intensively,<br />

as compared with that of the embdcment<br />

body bey<strong>on</strong>d limits of the culvert<br />

thsnnal influence z<strong>on</strong>e<br />

Thus temperature field, plotted according to<br />

measurement data <strong>on</strong> November 27 (see Big.l),<br />

shows that freesing depth of soil around the<br />

rectangular reinforced c<strong>on</strong>crete culvert is ab+<br />

ut 1.5-2 times more as aompared to thab of in<br />

the embaakment body bey<strong>on</strong>d the l-ts of the<br />

culvert thennal Wluence z<strong>on</strong>e. Results of analgals<br />

of temperature fields 5~ aoils surrounding<br />

culverts, located under up to 5 m high<br />

embanlanents, allow to diotinguish c<strong>on</strong>diti<strong>on</strong>ally<br />

three stages of growth of a seas<strong>on</strong>ally frozen<br />

soil halo around the culvert secti<strong>on</strong>. The<br />

first stage (Fig. 3,a) is characterized by the<br />

xesence of Fnitial freezing and beavirsg soil<br />

1 ayere 1 around the culvert; and at the embankment<br />

surface. It beghs at a moment when the<br />

negative daily average air temperature becomes<br />

steady, The stage durati<strong>on</strong> depends <strong>on</strong> the<br />

thhiclmess of the fill leyer over the cave& :

I 2<br />

mcIIANIcAL ~IVTErnCTION<br />

Frostsusceptible soil freezing aziowd the culvert,<br />

exerts a force huence <strong>on</strong> smace of<br />

the latter. A schemaeic noti<strong>on</strong> <strong>on</strong> this influence<br />

<strong>on</strong>e can imagine <strong>on</strong> the basis of the known<br />

segularitiee (Peletrukhin, 19671, takhg lato<br />

account anaILysad above freezhg regime peculirities<br />

of soils, sumoundiag the culvert. During<br />

the first stage of soil freezbg (see<br />

Big. 3,a) regelati<strong>on</strong> of soil with lateral and<br />

upper culvert surfaces takes place (Fig. 4)<br />

whereas soil negative temperature dxopping,ihe<br />

regelati<strong>on</strong> strength FZLcreaases.<br />

I<br />

I<br />

Pig.3. Freezing Stages of Soil murid Culver%<br />

Secti<strong>on</strong>s: a- Stage I, b- Start of Stage 2,<br />

c- Start of Stage 3, d- FWBh of Stage 3s 1-<br />

Soil in initial Stage of freezing-heavbg,<br />

2- bard-frozen Soil, 3- <strong>Permafrost</strong>, 4- thawed<br />

Soil<br />

it was equal to several days when thickness<br />

being 50-60 cm and to 2-3 decades for 1,5 m<br />

thfckiess. In the latter case there appears a<br />

hard-frozen soil layer 2 at cooling suxfaces,<br />

thickness of whoch increases with time.<br />

The first stage ends by the moment of closing<br />

of the two seas<strong>on</strong>al frozea mound layers, OCcured<br />

due to freeziag of the fill from two sides,<br />

namely the embaakment surface and the<br />

culvert orifice. After that moment the sec<strong>on</strong>d<br />

free5ing stage begins (Fig. 3,b) and further<br />

freezing of frozen soil c<strong>on</strong>kinues up to xeachug<br />

hardfrozen state. Besides, fornati<strong>on</strong> of a<br />

seas<strong>on</strong>ally frozen soil layer from the uaderc-<br />

Wing permafrost surface 3 takes place. The<br />

moment of thae layer mexg- with seas<strong>on</strong>al frozen<br />

ground generated from culvert; orifice<br />

aide, dl& shes the sec<strong>on</strong>d stage completi<strong>on</strong><br />

(Fig. 3,cpTQ that time, soil near the<br />

middle p& of the culvert foundati<strong>on</strong> height<br />

is at initial freezing stage 1 and ita temterature<br />

is higher than minus 2%, while soil<br />

arouud culvert secti<strong>on</strong>s and the foundati<strong>on</strong> top,<br />

being j-u a hard frozen state 2, has the temperature<br />

of minus 2% and lower. Soil 4 bey<strong>on</strong>d<br />

the culvert Whence z<strong>on</strong>e, is still a<br />

thawed state. At this stage the freezhg boundary<br />

is of a curved shape.<br />

The third freeeig stage is characterized by<br />

further cooling and thickness Fncreasing of<br />

hard-frozen soil massif surrounding the culverb.<br />

By the end of this stage the psocess of<br />

~011, freezung from- the culvert oxif ice side<br />

finishes. Around the culvert a solid massif of<br />

seas<strong>on</strong>ally frozen soil and permafrost forms,<br />

while bey<strong>on</strong>d culvert thermal influence z<strong>on</strong>e<br />

limits a layer of thawed soil can be rem&<br />

(Fig. 3.d).<br />

1448<br />

I I I I<br />

Fig&. Scheme of heaving Boxces acting wit-<br />

"freezing heavlsg SoilXulvert Secti<strong>on</strong>" System<br />

during freezhg Stage *I t I- soil Layer in hi-<br />

%ial freezing-heaving Stage, 2- hard-froeen<br />

Soil, 3- Culvert Secti<strong>on</strong>, 4- Thawed Soil<br />

Besides, there takes place a comgreesi<strong>on</strong> of<br />

culver% secti<strong>on</strong>a 3, as wel as thawed soil<br />

layers 4, ai a coaeequence of heaviag force<br />

effect 6;c, i.e. hternal stresses, generated<br />

in the soil layers 1 freezing around *he culved<br />

secti<strong>on</strong> and acting Fa the same direcrti<strong>on</strong><br />

as *ha* of a thermal Plow. The heaving force<br />

6, simultaaeously generated ia the soil<br />

layer I, freeziag from the embankment surface,<br />

causes rising of the overleyiag hard-frozen<br />

soil layer 2 and compxesi<strong>on</strong> of uyldeslayhg<br />

thawed <strong>on</strong>e 4. In the sec<strong>on</strong>d stage of freez$,ng<br />

(Fig. 3,b,c) the heaving force, generated in<br />

the layer of initial freezing-heaving I (Fig.5)<br />

ia directed nomally to an interface of this<br />

layer with the hara-frozen soil massif 2, bu*<br />

at &P acute angle to the secti<strong>on</strong> Lateral face3<br />

and the foundati<strong>on</strong> upper ;part 4 (aee Fig. 5).<br />

Under such c<strong>on</strong>diti<strong>on</strong>s the total heaving force<br />

may be decomposed into horiz<strong>on</strong>tal and vertical,<br />

comp<strong>on</strong>ente. The horiz<strong>on</strong>tal <strong>on</strong>e stipulates a<br />

la-beral squeeze of the culvexk secti<strong>on</strong>s and<br />

foundati<strong>on</strong>, and Lncreases c<strong>on</strong>tact ties of the<br />

regelati<strong>on</strong> between hard-frozen soil and cub<br />

vert, while the vertical <strong>on</strong>e c<strong>on</strong>tributes to<br />

soil and culverb rise. Calculati<strong>on</strong> results<br />

showed that for most of the starrdard oulverts<br />

the total strength of soil regelati<strong>on</strong> with the

culvert secti<strong>on</strong> surface exceeds the culvert culvert c<strong>on</strong>tact as <strong>on</strong>e of such mea~mes. C<strong>on</strong>siweight.<br />

That's why the hard-frozen soil mas- derati<strong>on</strong> of versi<strong>on</strong>s of n<strong>on</strong>-standard watersif,<br />

surrounding culvert secti<strong>on</strong>, can rise <strong>on</strong>- pass c<strong>on</strong>structi<strong>on</strong>s, not affectbg negatively<br />

ly together with b-frozen culvert; secti<strong>on</strong>. <strong>on</strong> road embankments during the freesin$-tha-<br />

DurFng the thixd freezhg stage (Fig.3,d) the wLng process of frostsusceptible soils used,is<br />

bterface of hard and thawed soile witkin the a suggestive COW as well.<br />

thermal Whence z<strong>on</strong>e of culve& decreases,<br />

while the thicbesa of hard-frozen soil masrsii<br />

Fncre as8 s.<br />

REF'EIIEKCES<br />

I . JumUis A.B. (1973) The soil-culvert-femperature<br />

system up<strong>on</strong> freezing. Symposium <strong>on</strong><br />

Frost Acti<strong>on</strong> <strong>on</strong> Roads. Report 1. Organizati<strong>on</strong><br />

for Ec<strong>on</strong>omic Cooperati<strong>on</strong> and Development, Paris,<br />

p ~ 235-248. .<br />

20 Liverovw A.V., MOPOZOV K*D*(I94'l) StrOitelstvo<br />

v uelovijalrb vechnoy merzloty, LenFngraadoskva,<br />

Stroyizdat.<br />

3. Novozhhplov G.F.(1963) Puchenie zemljanogo<br />

polotna na poltkhodakh k iskusstvennym sooruzhhenijam<br />

(Stroiteljstvo zheleznykh dorog):SbornFk<br />

Tmdov, LITZNT, Leningrad, Vypusk 203, ss.21-<br />

30.<br />

Fig.5. Scheme of heaving Ferces acting within<br />

"freezing heavhg Soil-aulvert Seati<strong>on</strong>" Syatem<br />

dwQg freezhg Stage 2: '1- soil Layer in U-<br />

tial freezing-heaving Stage, 2- hard-frozen<br />

Soil, 3.- Culvert Seati<strong>on</strong>, 4- Foundati<strong>on</strong><br />

So, the pxwbabili.t;s of hard-frozen soil rise<br />

together with culvert secti<strong>on</strong> decreases. In<br />

the light of the stated analysis the sec<strong>on</strong>d<br />

stage of soil freaeing arouud the culvert<br />

(Fig. 3, c) ahodd be c<strong>on</strong>sidere a8 a basic <strong>on</strong>er<br />

C<strong>on</strong>diti<strong>on</strong>s, existing duriq that stage, should<br />

be taken as design <strong>on</strong>es (Fig. 5) when culverts<br />

standard structure develo iag and autihheavin@;<br />

measures selectinf, a8 wefl as when detedniag<br />

culvert; stab lit7 in case of heaviasg<br />

force effect, tatring lsto account loo& a&ural<br />

c<strong>on</strong>diti<strong>on</strong>s.<br />

Peculiarities of thexmal c<strong>on</strong>diti<strong>on</strong>s of Soils,<br />

surr~undbg road culverbs, exclude the possibility<br />

of hard-frozen soil layers upwara movbg<br />

re1akiveJ.y to culvert seati<strong>on</strong>s. Therefore,<br />

the standard method for calculati<strong>on</strong> of the<br />

c<strong>on</strong>structi<strong>on</strong> foundati<strong>on</strong> stability under the<br />

effect of heaving forcea (SNFP, 1977) can't be<br />

used fox road culverts stability estimat;i<strong>on</strong>r<br />

5. Peretrukhin N.A.(196) Vzaimodeistvie fundamentov<br />

s pxomerzajuschim puchiaistym grmntom,<br />

v Sbornike Moroznoe puchenie grUnt;ov i<br />

sposoby zaschity sooruzhenij ot ego vozdejstvijar<br />

Trudy TsNIIS, Vypusk 62, ss.74-99.<br />

6. PeretrukhFn N.A., Tope+ A.A.(lg&) 0 nerowtostjakh<br />

prodohogo profllja zheleznodor<strong>on</strong>hnogo<br />

puti nad vodopropushymi trubd. Transportaoe<br />

atroitelstvo, N 8, ss.7-8.<br />

8. SNiP IT-18-76 (1977) Chast II. G1.18. Osnov<br />

d ja i fuadamenty na vechomerzlykh grunt akh.<br />

Moskva, Stroyisdat.<br />

CONCLUSION<br />

In the case of heaving eoils utilizati<strong>on</strong> as a<br />

material OP base for wp to 5 m heigh$ road embanbnents,<br />

a special c<strong>on</strong>aiderati<strong>on</strong> should be<br />

given to the selecti<strong>on</strong> of culvert and embankment<br />

stmotws, hki.ng into account peculiarities<br />

of their thermal and mechanical Fnteracti<strong>on</strong>.<br />

Standard culverbs beinng used, antiheaving<br />

measures should be taken to reduce up<br />

to standard values or eliminate the psobability<br />

of railway track ox highway pawement me-.<br />

venness occwence .<br />

It is expedient to c<strong>on</strong>sider the use of thermal<br />

insulati<strong>on</strong> within the z<strong>on</strong>e of embanlrment: and<br />

1449

* METHODS OF QUANTITATIVE VALUATION OF REGIONAL HEAT RESOURCES<br />

FOR PREPARATION OF PERMAFROST PLACER DEPOSITS TO MINING<br />

G.Z. Perlshtein and V.E. Kapranov<br />

All-Uni<strong>on</strong> Scientific <strong>Research</strong> Institute of Gold and Rare Metals, Magadan, USSR<br />

t<br />

SYNOPSIS<br />

According to modern noti<strong>on</strong>s there are regi<strong>on</strong>al and microclimatic Pactora Of'<br />

heat exchange between rock surface and atmomhere. In the report it is offex%& to use three<br />

parameters for quantitative valuati<strong>on</strong> of regi<strong>on</strong>al pesoureen of atmosphere heat:density of heat<br />

flow to the,exposed surface of frozen ground, temperatuwr of wet thermometer and moist surface<br />

temperature. With the help of the data offered in the report the eretimati<strong>on</strong> le given to the<br />

natuxal heat reaoursea of some.permafroat regi<strong>on</strong>s and the posaibility of their UBB POr Water<br />

heat reclamati<strong>on</strong> is c<strong>on</strong>aidered.<br />

Methods of thawin baaed <strong>on</strong> wing solax<br />

radiati<strong>on</strong>, atrnoapaare ,and surface water8 have<br />

ot wide distributi<strong>on</strong> in practioe of pemaf<br />

roat placer deposits, exploitati<strong>on</strong> in the<br />

USSR and NorthAmerioa. As a rule, the employment<br />

of every possible type of fuel and power<br />

imtallati<strong>on</strong>e turns out to be ineapedient<br />

because of high heat loss when o<strong>on</strong>vershg<br />

frozen mock into thawed state (20-60<br />

kWmh0m-3). The problem8 of efficiency and<br />

eo<strong>on</strong>omy of thamng is especially acute for<br />

placer deposits of Siberia and the North-East<br />

of the USSR where preparati<strong>on</strong> of Borne frozen<br />

grounds to excavati<strong>on</strong> is being carried out<br />

in very large scales and influencer decisively<br />

<strong>on</strong> the prime coat of mineral output. In<br />

c<strong>on</strong>necti<strong>on</strong> with thin the importance of workingout<br />

eome reliable criteria allowing to<br />

value natural heat resowseg of thie or that<br />

regi<strong>on</strong> most corn letely from the point of view<br />

of permafrost t R awing ie evident. Tn Soviet<br />

literature similar valuati<strong>on</strong>s were made till<br />

recently by the eum of positive degree~~hours<br />

of air temperature drawing eometimes the data<br />

of radiati<strong>on</strong> balance (Metodika.. .,1979).<br />

Besides, such important climatic factors as<br />

wind velooity,air moisture etc. were not<br />

taken into account. As for the temperature<br />

of surface waters it changes eharply depending<br />

<strong>on</strong> dimensi<strong>on</strong>s and Local perculiarities<br />

of water courae feed; therefore its uae as a<br />

regi<strong>on</strong>al characterietic is not competent,<br />

To our mind all the pointed dxawbacks may be<br />

eliminated <strong>on</strong> the base of modern ideas about<br />

the dependence of temperature regime of<br />

different types of surface8 <strong>on</strong> outward heat<br />

exchange c<strong>on</strong>diti<strong>on</strong>e (Kourtener,Chuanovskif,<br />

1969: Pavlov,1975; Perlshtein,l979). In<br />

reference to the problem of radiati<strong>on</strong> thawing<br />

(by Pavlov and Olovin) tMs queeti<strong>on</strong> is tho .-<br />

rou hly c<strong>on</strong>sidered in works by Balobajev<br />

( 1923) ,Lukjanov and Golovko (1957),PavloY and<br />

Olovin (1974) ,Parlehtein(1979). Following<br />

them lett expreee the density of a heat flow<br />

(Q, W*mm9) to a rock surface from the claeeic<br />

equati<strong>on</strong> of radiati<strong>on</strong>-heat balance:<br />

4 =at(i-A)+Ia-Is-Hc-M , (1)<br />

where at is total shortwave radiati<strong>on</strong>; A is<br />

the eurface'albedo in &ares of unit; Io ,Is<br />

is l<strong>on</strong>gwave radiati<strong>on</strong> of atmaphere and rock<br />

suxface res eceivel 8 Hc is the intensity Of<br />

c<strong>on</strong>vectjve Reat exogmge wfth atmosphere; M<br />

is the heat lose for etvaposatl<strong>on</strong> from the<br />

eurface<br />

UaLng the linear approximati<strong>on</strong> of surface<br />

temperature functi<strong>on</strong>s entering the known<br />

phyeioal lawa (radiati<strong>on</strong>,oooling,and evaporati<strong>on</strong>)<br />

let's exprees %he valuee I, Hc and<br />

M .by the following dependences:<br />

whe 6 is Stephan-Boltmuam's c<strong>on</strong>stant,<br />

W*rn3*( OC)-4; 6 is a relative radiating<br />

capacity of the eurface in ,moet cams approximated<br />

to 0.9; To is the heat radiati<strong>on</strong> of<br />

the surface at OOC, -288 W*me2tdh is the<br />

coef icient of o<strong>on</strong>vective heat exchange,<br />

Worn-'*( OC)-l; fa is the temperature of air,<br />

is the oosffi ient of evaporati<strong>on</strong><br />

(c<strong>on</strong>densati<strong>on</strong>) W*m-~~P&t-l ;e,(T)and eo is the<br />

pressure of saiurattn vapour at T temperature<br />

and OW, respectfvaly, Pa; ea is the<br />

presaure of water vapour in air, Pa; U p is<br />

the coefficient of Linear approx tio of<br />

power radiati<strong>on</strong> law, 4.6-4.8 w*m-$c)-P; 6<br />

I s the analogous coefficient of the preseure<br />

dependence of' satur ting vapour <strong>on</strong> temperature,<br />

-70 Pa.( OC)-.<br />

Taking into account expressi<strong>on</strong>s (2)-(4) let'e<br />

express equati<strong>on</strong> (1 1 as:<br />

1450

It Is to be noted that thhfi ae/ah ratio is<br />

c<strong>on</strong>stant (1.56~10-2PC4%3 1. The dh values<br />

depend <strong>on</strong> the wind velocity and may be expreseed<br />

with a satisfactory approximati<strong>on</strong> by<br />

the formula:<br />

Heat Flow Density ( Q W=n-~-2)<br />

of Solar Raaia'ti<strong>on</strong> ant'Atmosphere<br />

to the Exposed Surface of Frozen<br />

Rocks in the Period of Thawing<br />

where is the wind velocity,m*s-l- the dimensi<strong>on</strong><br />

of O L is ~ expressed in W*C1 t OC)-1.<br />

On exposing Proaen rocks in warm period their<br />

surface gete the ioe melting temperaturea<br />

(O°C> near1 instantly. As follows from expresai<strong>on</strong><br />

(58 the deneity of heat flow ( QO )<br />

from atmosphere 1s maximum at thie moment<br />

and equal to:<br />

The right part of equati<strong>on</strong> (7) includes the .<br />

valuee depending <strong>on</strong> the regi<strong>on</strong>al erculiarities<br />

of climate ( at, ~ a 10, , eu,cd as 7, and also<br />

<strong>on</strong> the physical c<strong>on</strong>stants ('Io,eo )* The expo~led<br />

surface albedo of dispersed frozen rocks<br />

may also be c<strong>on</strong>eidered a8 the c<strong>on</strong>stant ap roximatwag<br />

to 0.1. hue, 9. is a regi<strong>on</strong>al cKaracteristic<br />

taking Into acoount all main soursea<br />

of natural energy which take part in PormInR<br />

heat flow to permafrost surface immediately<br />

alter the thawed layer i~l removed. This value<br />

most full characteriees the heat otential of<br />

a regi<strong>on</strong> Pn relati<strong>on</strong> to radiati<strong>on</strong> !hawing. All<br />

necemar data for its calculati<strong>on</strong> ma be found<br />

in climaeic referenoe bookam* It shourd be<br />

noted that in natural c<strong>on</strong>aiti<strong>on</strong>s th8 density<br />

of heat flow into thawing rocks during summer<br />

does not exceed 4-6 per cent of Q, <strong>on</strong> an ave-<br />

rage.Unlike it, go value is, as a rule 2-2.5<br />

tlmee more than at . In c<strong>on</strong>necti<strong>on</strong> wijh this<br />

the mistake of 40 calculati<strong>on</strong> has 8 similar<br />

order with errors of definiti<strong>on</strong> of such qua-<br />

Cities 88 Qt , H, etc. Table l gives the qo<br />

values fo$tbree different regi<strong>on</strong>s of permafrost<br />

according to the average m<strong>on</strong>thly data.<br />

As <strong>on</strong>e can see from the table, q0 varies widely<br />

reaching rather high values in the periodr of<br />

maximum. It*s enough to eay that every rjquare<br />

kilometer of expoeed surfaces of frozen rock@<br />

in the upper Kolyma and Indigirka in July is<br />

influenced by the natural heat Bourse equivalent<br />

in power to the Kolymakaya hydroelectric<br />

power stati<strong>on</strong>. ff calculate $0 according to<br />

the data of fixed-term observati<strong>on</strong>s, <strong>on</strong>e nay<br />

be assured that the dayly course of 0 is close<br />

to a sine-shaped <strong>on</strong>e. Between the mi 3 day and<br />

3O'clook in the afterno<strong>on</strong> these valueB are<br />

1.2-2.0 times hiEher than the average daily<br />

<strong>on</strong>es .<br />

3 L<strong>on</strong>mave radiati<strong>on</strong> of atmosphere .fa ie not<br />

measured directly at weather stati<strong>on</strong>s and may<br />

be calculated by the formula:<br />

Ia=Q,+&6(TtP73)4-Q~(i-A),<br />

An which the radiati<strong>on</strong> balance Qp and the rest<br />

measurod values ( Qt,A,T ) should relate to<br />

the name obsexvati<strong>on</strong> point.<br />

The coast<br />

of the<br />

Arctic<br />

Ocean<br />

(Shmidt) - 240 310 190 -<br />

The upper<br />

Kolyma<br />

(Susuman) 150 420 500 350 90<br />

Zabaikal j e<br />

(Borzja) 350 620 720 605 300<br />

As the thawed layer le accumulating the surface<br />

temperature is raising and he& loseea<br />

into atmosphere are increaeing what causes<br />

quick decreaae 'of heat Plow density into<br />

thawing masflif. The character of 9, changing<br />

<strong>on</strong> inorearjing the thawing depth is closely<br />

c<strong>on</strong>nected with the compoeiti<strong>on</strong> and thermophysical<br />

propertiea of rocks (fig.1).<br />

FLg. I<br />

Fig.1 De endence of Heat Flow ( )<br />

Density ento Thawing Massif <strong>on</strong> !he<br />

Thickness ( ) of Thawed Layer<br />

(July, the Upper Kolyma): 1- Gravel -<br />

Pebble Deposits; 2- Peat<br />

It*s clear that for the moat effective utilizati<strong>on</strong><br />

of natural heat resoume s for urposes<br />

of radiati<strong>on</strong> thawing of frozen rock@ Et le<br />

necessary to Femove the thawed layer off its<br />

surface as often as possible. The given c<strong>on</strong>diti<strong>on</strong><br />

is fulfilled most oasily when mining<br />

permafrost deposits with a bulldoxer-scraper<br />

method which leading positi<strong>on</strong> in mining<br />

industry of the North-Eaet of the USSR i~<br />

1451

c<strong>on</strong>diti<strong>on</strong>ed juat<br />

by this fact<br />

Such approach also allows to forcast the apeed<br />

of snow and surface Ice thawing in natural<br />

o<strong>on</strong>di-ti<strong>on</strong>s and during the dmplest operati<strong>on</strong>s<br />

of surface thermal reclamati<strong>on</strong>. The caloulati<strong>on</strong>s<br />

show that the thawinff speed in May in<br />

the upper Kolyma increaees 2.5-3.0 times 88<br />

a result of soiling icings whereas it i~l <strong>on</strong>ly<br />

25-30 per cent more in July. Such difference<br />

may be easily explained. In the 8mer when<br />

air temperature and moisture are high, the<br />

growth of absorbed radiati<strong>on</strong> at the expence<br />

of surface albedo changing makes <strong>on</strong>ly little<br />

share in the pooitive pari of the heat balance<br />

of ice suxface.<br />

As fox hydraulic thawing the heat potential<br />

of the regi<strong>on</strong> is better to characterise by<br />

the two c<strong>on</strong>stants dependent <strong>on</strong> the complex<br />

of climate c<strong>on</strong>diti<strong>on</strong>s - the temperature of<br />

wet thermometer (Tw) and the temperature of<br />

moist surface( Tm )<br />

The noti<strong>on</strong>s of Wet thermometer temperature<br />

are usefull when c<strong>on</strong>aiderina aome questi<strong>on</strong>s<br />

of outward heat exchange Fn c<strong>on</strong>diti<strong>on</strong>s of<br />

sprbkle thawing. Some worke tell that water<br />

temperature is c<strong>on</strong>siderably raiaing during<br />

drops'e fli ht in air (Vesexov 1959-<br />

Demidjuk,l9~1; Goldtman,l958). dne cathot<br />

agree with this affirmati<strong>on</strong> wtthout serious<br />

proviBors. Indeed, the temperature of flying<br />

dro B ( Td ) changes mahly as a result of<br />

turgulent heat mass exchange with air. The<br />

influence of radiati<strong>on</strong> faotors is negligibly<br />

little. The resulting density of heat flow<br />

( 4d) to a drop surface may be expreseed by:<br />

It should be noted that the values of the<br />

coefficients dhand de in formula (8) are<br />

quite high. So for a s heri a1 amp (of Im<br />

in radius) flylnq with &n*s-f speed b+,- 200<br />

W*m-2.( *C)-l (Kutateladze 1971). However, the'<br />

&/ah. ratio remaina equal to 1.56090-2oC.Pa-1<br />

It's clear that water heate if qd' 0. Hence ,<br />

the c<strong>on</strong>diti<strong>on</strong> of drop heating in air is:<br />

W-h-m-3.(oC)-l; R is the drop radius,m;<br />

a = dh+tae.<br />

Formula (IO) is meant for extremd valuati<strong>on</strong>s,<br />

of temperature changing of water dropa in air.<br />

Developing the proposed method <strong>on</strong>e can easily<br />

calculate the maximum value of evaporati<strong>on</strong><br />

in eprinklina c<strong>on</strong>diti<strong>on</strong>s what has a practical<br />

meaning for investigati<strong>on</strong> of moisture balance<br />

while sprinkling arid earths.<br />

The other parameter is Tm which presents<br />

the soluti<strong>on</strong> of equati<strong>on</strong> (5) at 9 =Or<br />

Physical senae of Tm Is the temperature<br />

which is attained by the moiat surface in<br />

the given climatic c<strong>on</strong>diti<strong>on</strong>e provided there<br />

is no heat outflow into an underlying layer,<br />

Phe temperature of ehallow stagnant pools<br />

h a the values cloee to T,. . AB water temperature<br />

in riverrs and brooks is, a8 a rule<br />

c<strong>on</strong>eiderably lower than Tm the questi<strong>on</strong> o#<br />

the area of poola-heptera made for improving<br />

the hydraulic thawing effectiveness is of<br />

great interest.<br />

C<strong>on</strong>siderin the heat balance of flowing water<br />

in interecfi<strong>on</strong> with atmosphere (neglecting<br />

heet flow Into bottom deposita) we'll pet an<br />

ordinary differential equati<strong>on</strong>:<br />

[qo-aT(Sl]dS codT(s) ,<br />

from which we'll PLnd the depsndencd of water<br />

temperatw T <strong>on</strong> the area and c<strong>on</strong>diti<strong>on</strong>s<br />

of outward heat exchange;<br />

T(S)-T,t(T,-P[t-e;cp~~~~ I (12)<br />

where $ is thearea of expo ed urface,m2;<br />

W is watercourae debit,mJ*h-f; the re&<br />

designati<strong>on</strong>s are the ame. It ia not difficult<br />

to sere that at&-- (i.e. in a atagnant<br />

pool) T(S) "Tm<br />

The calculati<strong>on</strong>s fox the climatic c<strong>on</strong>diti<strong>on</strong>s<br />

of July in the upper Indigirka are made by<br />

formula ( 12) , The result B a= given in table 2,<br />

Thus T;u which servea ae & integral chara-<br />

cteristic of air temperature and moiBture<br />

shows the possibility of heating or cooling<br />

dropa in flight. On the territory of the North-<br />

EaBt of the USSR water temperature is c<strong>on</strong>siderably<br />

lower than 7. <strong>on</strong>ly in the coldest<br />

small. rivers and brooks.<br />

More detailed analysis of heat mass exchange<br />

dynamics of water drops with air reuults in<br />

dependence :<br />

Initial<br />

Td=T,-(T,-T,)exp(-~), 3ut (10) 8<br />

TABLE 2<br />

Rated Water Temperature<br />

Shallow Pooh-Heatexe,<br />

OC<br />

in<br />

Water temperature at Ifferent<br />

water values s (m B )<br />

"**.""<br />

tur:, ,<br />

7-0 oc 5 10 20 50<br />

6 7.6 8.9 10.8 14*1 15.5<br />

9.3 10.3 11.8 14.4 15.7<br />

10 11.0 11.7 12.9 14.9 15.8<br />

12 12.6 13.2 13.9 15.2 15.85<br />

where t is the time of drop flisr;ht,h; To in 14 14.3 14.6 15.0 15.6 15.9<br />

initial water temperature,OC; c is the<br />

volumetric specific heat of water,<br />

1452<br />

100

We '31. point for comparis<strong>on</strong> that Tm =16OC<br />

and actual water temperature for example,<br />

in Bereljoich and Khatynnakh (Indigirkat B<br />

tributary) rivers are 11.0 and 5.9 oC.9hua,<br />

theIarxangement of shallow storage-p<strong>on</strong>ds of<br />

50-100m2 in area for each lrn3-h-l of watercourBe<br />

debit will allow 1.4 and 2.5 times<br />

increase of water temperature and hence,<br />

hydraulic thawing speed, respectively.<br />

The Tm value is eubjected to rather sharp<br />

daily fluctuati<strong>on</strong>s, For instance, in inter<br />

c<strong>on</strong>tinental regi<strong>on</strong>s of the North-East of the<br />

USSR the average values of Tm in July in<br />

dlfferent day time change from 7 to 26°C(fig2).<br />

vedenij~,vyp.3, pp.1-16.<br />

RourteneT,D.A.,Chudnovskil AmF. (1969).<br />

Raechet 1 regulirovanije teplovogo roafma<br />

v otkrytom i zashchishch<strong>on</strong>nom<br />

L.: Gidrometeoizdat, ppm184-22!Yte*<br />

Kutateladze,S.S. (1971). Osnovy teplofiziki.<br />

Novoslbirakt Nauka, pp.229-231.<br />

LukjanovV.C.,ColoVko,M.De (1957). Raschet<br />

glubiny promerzanija @Untov.- M.:<br />

Transzheldorizdat , p. 164<br />

Metodika merzlotnoi ajomki. (1979). Podoredo<br />

prof. V.A.Kudrjavteeva,M- Izd-vo MGU,<br />

pp . 49-53 .<br />

Pavlov,A.V. (1975). TepLoobmen pochvy s<br />

atmoeferoi v severnykh i umerennykh<br />

ehirotakh SSSR.- Yakutsk: Kn, izd-vo,<br />

p.303.<br />

Pavlov,A.V., Oloy+n,B.A. (1974). Iskusstvennode<br />

ottaivanqa merzlykh porod teplom<br />

Bolnechnoi radiat sii pxi razrabotke xos-<br />

8ypei.- Novoaibirsk; Nauka, pel82<br />

Perlshtein,G.Z. (1979). vodno-teplova'a<br />

melioratsija na Severo-Vostoke SSS$.-<br />

Novoaibirak: Nauka, p.304.<br />

Veaelov V.V. (1959) Ottaika ekskavatornykh<br />

podg<strong>on</strong>ov dozhdevanijem i Eidroiglamy.<br />

Tr.VNI1-I, Magadan,vyp.l2,pp.223-~43.<br />

Fi -2 Daily Courae of the Temperature<br />

( $m of Moiat Surface Calculated<br />

5y the Data of L<strong>on</strong>g Year Observati<strong>on</strong>s<br />

(July, the Upper Kolyma)<br />

,In the hottest days at bright ~un ehining rm<br />

may be above 40°C. The calculati<strong>on</strong>e show that<br />

provided the surface evaporati<strong>on</strong> and heat eranefer<br />

into an underlying thick layer are excluded,<br />

the temperature of stagnant p<strong>on</strong>de at<br />

the warmeet day hours may be increased to<br />

65-7OoC. TheBe Piguree make <strong>on</strong>eself to search<br />

sertain ways of accumulating and utilizati<strong>on</strong><br />

of high potential heat energy which inexaustible<br />

reBerve8 are presented in most regi<strong>on</strong>a<br />

of permafrost.<br />

REFERENCES<br />

Balobajev,V.T.(1963). Protaivanije merzlykh<br />

gornykh porod pri vzaimodeistvii s<br />

atmosferoi. V kn.: Teplo- i. massoobmen<br />

v merzlykh tolahchakh zenmoi kory,<br />

pp.105-116,<br />

Demidjuk L.M. (1961). Effectivnoje ispoLzovdje<br />

tepa solnechnoi ensrgii pri<br />

primenmil dozhdevalno-dranazhno~o metoda<br />

oftaivania merzlykh gmtov. V knmt<br />

Merzlotnyje issledovanija. Vyp.2,pp.<br />

198-213.<br />

Goldfman,V.G.( 1958)- Ottaika vechnamerzlykh<br />

gruntov dozhdevaniJem oborotnoi vodoi.<br />

Tr,VNII-l, Yagadan,t.7,razdrl. Meerzloto-<br />

1453

STABILITY OF ROAD SUBGRADES IN THE NORTH OF WEST SIBERIA<br />

A.G. Polunovsky and Yu.M. Lyvovitch<br />

Soyuzdornii, USSR<br />

3 mops x3 The xeport c<strong>on</strong>siders the peouliarities of natural and climatic o<strong>on</strong>diti<strong>on</strong>e of<br />

West Siberia that should be takan,into aooount at road design ana o<strong>on</strong>structi<strong>on</strong>. Frinoiples of<br />

providing the stability of the embankments built of various soils are given. Struotural soluti<strong>on</strong>s<br />

are proposed with the use of geotextile interlayers snd heet-insulating materials.<br />

The development of vast oil-and-gas regi<strong>on</strong>s in<br />

the North of West Siberia has required building<br />

a wide net of roads under complicated engineering-geologioal<br />

c<strong>on</strong>diti<strong>on</strong>s. This network<br />

inoludes inter-and iatrafield trunk roads of<br />

oil and gaa produoing xe i<strong>on</strong>s, whioh =e deaigna-ted<br />

fox heavy traffic mainly from 200 to<br />

1500 design vehicules per day).<br />

Engineering eoluti<strong>on</strong>s comm<strong>on</strong>ly used in road building<br />

praotice me no5 applicable to this<br />

area due to the oomplez of unfavourable c<strong>on</strong>di-'<br />

ti<strong>on</strong>a which axe 88 follows:<br />

- the abeenoe of c<strong>on</strong>structi<strong>on</strong> industry base as<br />

well a8 natural resouroea of the rook, gra-<br />

vel and s&nd qlls with a filtrati<strong>on</strong> footor<br />

higher then 10 cm/s; -<br />

- short period of above-zero temperatures;<br />

- exoeas moistening of the upper soil horira<strong>on</strong>a;<br />

- difficulties in o<strong>on</strong>structi<strong>on</strong> of unshfinkable<br />

eubgrades;<br />

- deficit and high cost of labour resources.<br />

A new approach to road building under such c<strong>on</strong>diti<strong>on</strong>s<br />

provides structural-technologioal soluti<strong>on</strong>a<br />

aimed at maximum reduced volume8 of earthworks<br />

and their executi<strong>on</strong> <strong>on</strong> a round-the-year<br />

basis, stage road c<strong>on</strong>structi<strong>on</strong>, the u6e of pseoaat<br />

pavements from reinforced o<strong>on</strong>orete slabs.<br />

The regi<strong>on</strong> in the Ob-Gnisey downstream iaterfluvs<br />

is cbaraoterlzed by extremely unfavourable<br />

climatic, soil-hydrologioal and cryogenic<br />

c<strong>on</strong>diti<strong>on</strong>s. The distinctive featuses of this<br />

area are excressive moistening and insufficient<br />

heat . %vexage annual air temper8ture is<br />

-3- 4 C in the south to -9- -12 C in the<br />

north of the area, a durati<strong>on</strong> of frostlees perlod<br />

iB 60-90 days, winter temperature ie up<br />

to -50 C, and the winas of 15-20 m/s blow frequently.<br />

Str<strong>on</strong>g winda oawe the anow tranefer<br />

which is o<strong>on</strong>siderabla due to a dry loose natu-<br />

1-9 05 the fresh snow with density 0.03-0.12-<br />

g/cm . A thickness of enow cover in the open<br />

tundra raagea from 20 to IOOcm, an average <strong>on</strong>e<br />

being 20-40cm. The relief is plane, slightly<br />

rugged ana very poorly drained, absolu'6e elevati<strong>on</strong><br />

marks range within 50-120m. The regi<strong>on</strong> is<br />

ohareoterlstia of extremely high swampiness and<br />

is very lab (up to as), .there widely ooow<br />

plarle and o<strong>on</strong>vexo-hummook vest peat bogs wnith<br />

peat; deposit depth from 1 to 4m (mainly about<br />

2m)<br />

AB for soil o<strong>on</strong>diti<strong>on</strong>s of the regi<strong>on</strong> permafrost<br />

is most comm<strong>on</strong>. The latter, firat of a11<br />

o<strong>on</strong>cerna with the northen regi<strong>on</strong>s where eeperefs<br />

talika ooow in the river valleys or n8&<br />

the lakes, with trough tsrlika being erhmely<br />

rare. In the regi<strong>on</strong> of Nadym and Urengoi 25-<br />

-30% of the Interfluve mea falls at the deposita<br />

thawed from fha surface up to the depth<br />

4-10m, which form the unmerged froaen masses.<br />

In the southern regi<strong>on</strong>s, development af the<br />

frozen masee8 oocws almost exoluaively in the<br />

pest meas. A temperature of the rook at the<br />

-<br />

deptb<br />

of zero annual amplitude varies from -3-<br />

-5 C in the north to above mro In the south;<br />

frosen gfound beoomes insular and the prooeas<br />

runs more aluggishly with aimultaneoua raduoti<strong>on</strong><br />

in the icity. Am<strong>on</strong>g the cover rocks a 00-<br />

mplex of sea deposits prevails with limited occuxenoe<br />

of alluvial depoaits in the flood plains<br />

and above-flood plain terraoea. These<br />

xoclce are mainly composed of clay aoils-loam ,<br />

sandy loam, clay and more rarely by fine<br />

sands. In all tie cases the c<strong>on</strong>tent of silt<br />

particles is high ,up to 50-9W. In the thawed<br />

o<strong>on</strong>diti<strong>on</strong> theae rocks are obafacterieed by<br />

unstable structwe and are pr<strong>on</strong>e to the thixotropic<br />

fluidifioati<strong>on</strong> under load applicati<strong>on</strong>,<br />

especially under multiple loading or vibrati<strong>on</strong>.<br />

This is explained by high ioity of the rock reduoed<br />

from Its surfaoe down al<strong>on</strong>g the seoti<strong>on</strong>.<br />

The moisture o<strong>on</strong>tent of the frozen clay rook8<br />

is 25-6s and is higher than that of thawed<br />

<strong>on</strong>es, which is 2540%. Sand soil~t of this TB-<br />

gi<strong>on</strong> me referred to the fine silts of vaxioua<br />

ioity and average moisture c<strong>on</strong>tent of 20-3"<br />

High degree of overwetting is first. of all,<br />

oharaoteristic of the clay eoh, but not seldom<br />

that la observed for the sandy soils. The<br />

1454

~~~<br />

settlement of the olay soil depthe <strong>on</strong> thawing<br />

varies depending <strong>on</strong> genesis, temperature climatic<br />

and hydrogeolo ioal c<strong>on</strong>diti<strong>on</strong>s over a wide<br />

range up fo 400 mm$rn. Settelments <strong>on</strong> thawing<br />

of the sands are usually insignificant and adm<br />

i d ble in terms of their use in the foundati<strong>on</strong>@<br />

an8 bodies of the road embankments at the<br />

looar-frozen state. The highest degree of the<br />

icity and subaideaae is obererved with the peat<br />

BoilsI The moisture c<strong>on</strong>tent of the frozen peat<br />

not aeldom le 300-400$ at the voluminal icity<br />

60-80%. Frost heave formati<strong>on</strong>s in the form of<br />

heave mounds several meters ~YI height and 40-<br />

-100m in plane occur in peat soils.<br />

The icity and temperatuse of a soil influence<br />

not <strong>on</strong>ly its atability- in the foundati<strong>on</strong> and a<br />

degree of subeidence, but also, to a high de&-<br />

reel determine the c<strong>on</strong>diti<strong>on</strong>s of working out<br />

the frozen soil and the possibility of uslng<br />

the material thus obtained either directly for<br />

embankment filling-up OF after a preliminary<br />

technological treatment .<br />

Wlfh due regard of the above peculiarlea a nuber<br />

of basic principles of the deslgn and c<strong>on</strong>mtruutl<strong>on</strong><br />

of subgrades in the northern regi<strong>on</strong>s<br />

of West Siberia has been formulated.<br />

According to the firet principle the subgrade<br />

is designed <strong>on</strong> the embanhents rather uniform<br />

in height (due to the smooth relief) and a reference<br />

nark is established with o<strong>on</strong>slderati<strong>on</strong><br />

of the snow-drifting, The latter is of speoia1<br />

importance for a regi<strong>on</strong> that is oharacterised<br />

by frequent ana str<strong>on</strong>g winds, dry displeclng<br />

anow, and a winter maintenance period up<br />

to 7-8 m<strong>on</strong>ths each year. The abeeme of a speaial<br />

erervioe of road operati<strong>on</strong> during c<strong>on</strong>atructi<strong>on</strong><br />

pefiod a8 well a8 during the first years<br />

after putting a road into service should also<br />

be taken into ao~ount. That is why the subgrade<br />

design and the ohooice of reference mark is<br />

based an the oriterium of the snow-drifting.<br />

According to the snow-drifting o<strong>on</strong>diti<strong>on</strong> the<br />

height of the embankment is deeigned <strong>on</strong> basis<br />

of a maximum height of the snow oovex and climatio<br />

peculiarities of a regi<strong>on</strong>. Due to the ~<br />

absence of road network and the experience of<br />

Its operati<strong>on</strong> under winter c<strong>on</strong>diti<strong>on</strong>s a8 well<br />

as difficuties of factual informati<strong>on</strong> gathering<br />

during winter investigati<strong>on</strong>s of a route,<br />

it is recommended to design the embankment helght<br />

wing a method of the Omsk Branch of Sowdornii<br />

by formula:<br />

where H, = design maximum height of the<br />

anow oover from data of the nearest<br />

meteorological stati<strong>on</strong>;<br />

If, = ooafflcient o<strong>on</strong>siderlng the influence<br />

of the relief, whioh is<br />

determined from Table I;<br />

Ah tp minimum height of the embanbent<br />

edge above the snow c'over in the<br />

case of open horiz<strong>on</strong>tal secti<strong>on</strong><br />

of the terrain, m.<br />

TABU I<br />

"L "<br />

bharactmistic of the terrain<br />

7<br />

"-"."- "<br />

Highly rugged terrain covered with<br />

vegetati<strong>on</strong> and forest massive8<br />

Leeward slopes of steepness 1:3 and<br />

mor e<br />

Hilly rarely wooded tundra with underbrush<br />

Hummoclry tundra<br />

Hilly tundra<br />

Windward slopes of sttepness more<br />

than 1:3<br />

Flat c<strong>on</strong>tinental peat-moss tundra<br />

Open frozen water surfaces (water<br />

areas) lh and more in length<br />

New-shore tundra<br />

Upland and watershed heads<br />

""""""""""_____I_______<br />

""1"<br />

K1<br />

"-2"<br />

""""<br />

2.0<br />

1.8<br />

1 .a<br />

1.7<br />

1.6<br />

1.3<br />

1.2<br />

1.0-1.2<br />

1 .o<br />

0.8-1 e 0<br />

When specifying the embanbent height and structure,<br />

the sec<strong>on</strong>d design prinoiple should be<br />

followed whioh requires to determine the depth<br />

of thawing of the foundatl<strong>on</strong> under the embankment<br />

of 8. given height by means of heat-engineering<br />

oalculati<strong>on</strong>e as well as to evaluate a probable<br />

settlement of the embanhent foundati<strong>on</strong><br />

after thawing and the rate of settlement completi<strong>on</strong>,<br />

To take into account 8 degree of soil<br />

thermosubsidence as well as an effect of the<br />

foundati<strong>on</strong> aettlement <strong>on</strong> the performance of a<br />

road the use Is made of <strong>on</strong>e of the two wellknown<br />

fundamentals (spsclf ied in c<strong>on</strong>atruct i<strong>on</strong> norms)<br />

for designing the structures <strong>on</strong> thermosubsiaing<br />

soils. In applicati<strong>on</strong> to road c<strong>on</strong>structi<strong>on</strong><br />

c<strong>on</strong>diti<strong>on</strong>s these fundamentals are interpreted<br />

by the following way: aooording to the first<br />

fundamental the thawing of the natural foundati<strong>on</strong><br />

underlying the embanbent is inadmissible<br />

during the whole service life of a road; according<br />

to the see<strong>on</strong>d fundamental the thawing<br />

of soils in the embanbent foundati<strong>on</strong> is admiasible<br />

through a design depth within which tlia<br />

settlement of the thawing layer does not exceed<br />

a permissible limit depending <strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s<br />

of the road pavement performance.<br />

The third deeign prinoiple is based <strong>on</strong> that<br />

the stability of the embankment itself built<br />

from a soil. the moisture o<strong>on</strong>tsnt of which is<br />

higher than an optimum <strong>on</strong>e should be provided<br />

during thawing of the embankment ox when the<br />

latter and its foundati<strong>on</strong> is in the thawed state.<br />

The settlement <strong>on</strong> thawing of the embankment<br />

built in winter from icy lumpy soil is c<strong>on</strong>diti<strong>on</strong>ed<br />

by the porosity of the soil itself<br />

and the sec<strong>on</strong>dary porosity of the lumps. This<br />

8ettlemer.t should not exceed admissible limits<br />

depending <strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s of the pavement operati<strong>on</strong>.<br />

When designing the embankment acoording<br />

to the sec<strong>on</strong>d principle, total settlement of<br />

the embankment body and the thawing layer of<br />

the embankment foundati<strong>on</strong> should be within the<br />

permissible limits.<br />

Road design for the northern regi<strong>on</strong>s is reoommended<br />

to carry out o<strong>on</strong>sidering subsequently<br />

the above three principles. First of all, a<br />

refereme mark of the embankment is established<br />

<strong>on</strong> the baais of snow-drifting c<strong>on</strong>diti<strong>on</strong>.<br />

-"I"-<br />

1455

With the embankment height obtained, the heat-<br />

-engineering computati<strong>on</strong>s of a structme are<br />

performed and the depth of thawing of the emba- -<br />

nlunent and its soil. foundati<strong>on</strong> Is determined,<br />

For these computati<strong>on</strong>s a road is divided Into<br />

typical lengths taking into account peculiarities<br />

of the relief, and soil-climatic c<strong>on</strong>diti<strong>on</strong>s<br />

as well as compositi<strong>on</strong>, state and a degree<br />

of ice-cementatiqn of the soil used for embankment<br />

c<strong>on</strong>structi<strong>on</strong>. From data <strong>on</strong> thawing the<br />

embanhent and its foundati<strong>on</strong>, <strong>on</strong> physical-and-<br />

-mechanical characteristics of the embanlunent<br />

and foundati<strong>on</strong> soils the stability of a whole<br />

road structme (an embankment and road pavement)<br />

is assessed, The total settlement of the<br />

embanhant and its foundati<strong>on</strong> is calculated and<br />

compared with a pexmisaibXe <strong>on</strong>e, and the stability<br />

of the road structure as a whole after thawing<br />

is evaluated. At this stage of calculaatl<strong>on</strong>8<br />

the applicati<strong>on</strong> of averaged data is allowable.<br />

When the embankment stability is not provided<br />

or the settlement exceeds an admissible<br />

limit the ' addwtment of the structure ie pexformed.<br />

The adjustment may inolude the change of<br />

the embankment height, the change of the design<br />

principle (fox instance, coming from the sec<strong>on</strong>d<br />

principle to the first <strong>on</strong>e), and the use of special<br />

materials (heat-insdating materials, g80-<br />

textile) in order to regulate either thermal<br />

regime or stressed-strained state of the struoture.<br />

Within the frames of alternate design<br />

variow structural soluti<strong>on</strong>s uan be c<strong>on</strong>eidered<br />

not <strong>on</strong>ly as mutually complementary but also aa<br />

competitive <strong>on</strong>es from the engineering-eo<strong>on</strong>omical<br />

point of view.<br />

Flg.1c Resign scheme for evaluaki<strong>on</strong> of the stability<br />

of the embankment over the frozen foundati<strong>on</strong>,<br />

with the lower part of the embanlanent<br />

made of compreseibla soils<br />

Fig.ld Design saheme for evaluati<strong>on</strong> of the stabllit<br />

of the embankment <strong>on</strong> the thawing foundati<strong>on</strong><br />

(as in the case in Pig.10)<br />

Calculati<strong>on</strong>8 for the road embanlunents <strong>on</strong> thermosubsident<br />

soils are performed <strong>on</strong> the basia of<br />

four barsia sohemes. The fkst two sohemes<br />

(Pig.1) c<strong>on</strong>eern with c<strong>on</strong>struotioa of the embankments<br />

from sandy ~ils of a8mlasible motstwe<br />

c<strong>on</strong>tent, and theix design is performed aouoyding<br />

to the first ox sec<strong>on</strong>d fundumental, respectively,<br />

i.e. with inadmisekbble or admissible<br />

thawia of the foundatloo. Design sohemea 3<br />

and 4 fFig.2) a<strong>on</strong>oern with embanhent c<strong>on</strong>ertruati<strong>on</strong><br />

with the we of iroaen lumpy soils in the<br />

.lower part of the structure. Scheme 3 ie applied<br />

to the embanwent design according to the<br />

first principle, 1.e. without thawing of the<br />

foundati<strong>on</strong> and with looat i<strong>on</strong> OS LI thawing hoxiz<strong>on</strong><br />

during a whole ~ummer above the bottom of<br />

the embankment body. However in this oese the<br />

eettlement of the foundati<strong>on</strong> ia excluded beaau-<br />

SI the smbsrnlcmeat is built from soils wstiable<br />

at thawing but deformati<strong>on</strong>s of the erubgrade and<br />

road pavement are possible. Soheme 4 is applied<br />

to the design of the embanlanent aooox8ing<br />

to the sec<strong>on</strong>d design pxinciple pith a posaibllity<br />

of thawing of the foundati<strong>on</strong> of the embankment<br />

built from soils unstabls at thawing.<br />

@/2 , 81 /A<br />

1<br />

2<br />

Fig.la Design scheme for evaluati<strong>on</strong> of the stability<br />

of the embanbent made of incompressible<br />

aoils and laid over the frozen foundati<strong>on</strong><br />

Fig.4b Design scheme for evaluati<strong>on</strong> of the stabllity<br />

of the embankment <strong>on</strong> the thawing foundati<strong>on</strong>:<br />

1- sand; 2- moss-peat layer; 3- the locati<strong>on</strong><br />

of the upper boundary of the perennially<br />

frozen soils; 4- oompresaible-<strong>on</strong>-thawing soil<br />

Fig.2 Structure of the embankment with heat-<br />

-insulating layexa in its foundati<strong>on</strong>:<br />

4- peat; 2- plastid foam; 3- geotextile; .<br />

4- sand<br />

When designing roed structurss <strong>on</strong> the baaie of<br />

the above four sohemes, aomputati<strong>on</strong>pl are performe6<br />

which include the determinati<strong>on</strong>. of magnitude<br />

of the final settlement of the embankment<br />

and its foundati<strong>on</strong> active layer m wall LIB durati<strong>on</strong><br />

of the c<strong>on</strong>solidati<strong>on</strong> settlement and<br />

terms'of oompleti<strong>on</strong> of the latter; before both<br />

these oaloulati<strong>on</strong>s the heat-engineering computat<br />

i<strong>on</strong>s of the depth of the embankment and foundati<strong>on</strong><br />

thawlng are oarried out. An acoepted<br />

method of the heat-engineering computati<strong>on</strong>s iS<br />

based <strong>on</strong> the aoluti<strong>on</strong> of a two-dimensi<strong>on</strong>al problem<br />

taking into account the n<strong>on</strong>-uniformity of<br />

thawing across the embankment width due to an<br />

additi<strong>on</strong>al heat flow moving from the slope sides<br />

and the-near-slope band.<br />

A computer software of the heat-engineering<br />

computati<strong>on</strong>s is worked out, which allows to car-<br />

1456

xy out a multifootor analysis of the influence<br />

of natural-and-olimetic c<strong>on</strong>diti<strong>on</strong>s of the area<br />

of the route alignment, of variants of the embanbent<br />

heights and structures, of soil type,<br />

properties and state as well as the effect of<br />

interlayers from the artifioial materials.<br />

Final c<strong>on</strong>olusi<strong>on</strong>s as to the possibility of the<br />

we of any particular strwture may be drawn<br />

<strong>on</strong>ly <strong>on</strong> the basis of oaloulatl<strong>on</strong>s of the embankment<br />

eettlament an8 evaluati<strong>on</strong> of posslble pavement<br />

deformati<strong>on</strong>s. It should be taken Into<br />

account that in the case 02 precast pavements,<br />

there is a posnibility of slab replaoement and<br />

restoring the pavement evenness. According to<br />

this teohnology, whiah is essentially a variant<br />

of the two-stage. c<strong>on</strong>strwti<strong>on</strong> method, at<br />

the firat stags the pavement laying-down is permlttea<br />

before completing the embankment c<strong>on</strong>solidati<strong>on</strong>,<br />

When the final aettlement is aohieved<br />

and there ooouxs settlement attenuati<strong>on</strong> the<br />

aeo<strong>on</strong>d stage begins that Includes ,slab diemounting,<br />

levelling and filling-up the subbase, and<br />

then slab relaying <strong>on</strong> the levelled suxfaoe.<br />

To asses8 a magnitude of the ilnal Settlement<br />

of unstable, compresalble-<strong>on</strong>-t~wing soils of<br />

the embankment as well as Its foundati<strong>on</strong> i.t is<br />

seoommended to use the following expressi<strong>on</strong>:<br />

zH,= H,+Ha f ah<br />

whareScaLaG= total magnitude of the final settlement<br />

of road struoture;<br />

lpL = modulus of settlement<br />

design layer, mm/m;<br />

ZH~ 5 thickneea of B design comperrlble-<strong>on</strong>-thawing<br />

layer in an "embankment-relief<br />

element system";<br />

H, = thiakneas of umtable layer of<br />

the embanbent ;<br />

.H2 = thickness of thawing aative layer<br />

;<br />

Ah = thickness of moss-peak oover.<br />

Magnitude of the modulus of settlement of frosea<br />

lumpy soils <strong>on</strong> thawing, which axe wed for<br />

the lower layers of the subgrade Is taken to be<br />

aa fallows: 100+200mm/m far loose-frosen and<br />

dry-frozen sands, 300+500mm/m for hard-frozen<br />

and lastlo-frozen silty sands and sandy loams;<br />

500-~0Om/m fox hard-frozen loams and oleys,<br />

and 700+800mm/m for froeen lumpy peats.<br />

The modulus of settlement of soils In natural<br />

strata depends <strong>on</strong> the type of a soil in the aative<br />

layer, its genesis, total moisture c<strong>on</strong>tent,<br />

and a degree of the ice oementati<strong>on</strong> (iclty).<br />

Total values of the m9dulu.s of settlement<br />

at normal atresa of O.lg/cm at the surface of<br />

a design aompressible layer of soil me:<br />

20+60mm/m for sands, 100~120mm/m for sandy loema,<br />

120+400mm/m for loams and clays, ana 300-<br />

-500mm/m for peats.<br />

'Po determine a durati<strong>on</strong> and time of completi<strong>on</strong><br />

of the settlement of compressible-<strong>on</strong>-thawing<br />

soil layer of the embankment and itrr foundati<strong>on</strong><br />

it is necessary to establish a period of COnsolidafi<strong>on</strong><br />

in order later <strong>on</strong> to lay down a pavement,<br />

for instance, from precast reinforced<br />

slabs; because compressible (unstable) soil layer<br />

begins to deform under the load from the<br />

overlaying courses of the road pavement structure<br />

<strong>on</strong>ly,after thawing or in the prooess of<br />

thawing, for rough computati<strong>on</strong>s it is possible<br />

to assume that the time and xate of c<strong>on</strong>solidati<strong>on</strong><br />

is equal to the time and ratre of thawing<br />

of the design oompressible layex. Thus, if is<br />

proposed to ooasider the settlement and the time<br />

of a<strong>on</strong>solidati<strong>on</strong> of compreasible layers together<br />

with the time and rate of thawing of compressible<br />

Soils in the embanhent and its Pounderti<strong>on</strong>.<br />

Fox a given period of time tt thlckness<br />

of thawing compressible layer H~ ia found<br />

<strong>on</strong> the baeis of heat-engineering computati<strong>on</strong>s<br />

and its eettlament A at any given time is determined<br />

by formula42) . The time of achieving<br />

a final magnitude of the settlement oorxesp<strong>on</strong>ds<br />

to the time of complete thawing of 8 layer<br />

H; . Of essential importance is thickness<br />

of the oompressible soil layer, its total moisture<br />

c<strong>on</strong>tent <strong>on</strong> thawing, its modulus of settlement<br />

and Btruotwe as well a8 a seas<strong>on</strong> of the<br />

embankment c<strong>on</strong>structi<strong>on</strong> (summer or winter),<br />

the state of a soil used (thawed, frozen), a<br />

degree of fragmentati<strong>on</strong> (lumpiness).<br />

Indices of structural and physical-and-mechanlcal<br />

properties of the compreesible-<strong>on</strong>-thawing<br />

soils of the aubgrade influenoe the total value<br />

of settlement and a mode (n<strong>on</strong>-uniformity)<br />

of settlement development which resulte in oertain<br />

diffiaulties not <strong>on</strong>ly in providing the embanbent<br />

atability but also in laying down the<br />

road pavement because the terms of c<strong>on</strong>structi<strong>on</strong><br />

of the latter depend <strong>on</strong> an admissible intensity<br />

of settlement development. In o<strong>on</strong>necti<strong>on</strong><br />

with the necessity to we compressible-<strong>on</strong>-thawing<br />

soils for the embankment c<strong>on</strong>structi<strong>on</strong>, <strong>on</strong><br />

the basla of the design echemes (Fig.lb,c,d) '<br />

subgrade struotures are developed which include<br />

elements made of geotextile ana heat-insulating<br />

meterials in order to oompensate the n<strong>on</strong>-<br />

"uniformity of settlement development arr well<br />

as to proviae the structural stability and to<br />

regulate the c<strong>on</strong>gelati<strong>on</strong> regime. Schemes of<br />

subgrade atruotures are given in Figures 2-5,<br />

Fig.3 Structure of the embanhent including a<br />

layer of compressible-<strong>on</strong>-thawing soil, with<br />

heat-inaulat ing Layer <strong>on</strong> the erurfaoe: 1- land;<br />

2- pavement slabs; 3- geotextile under the pavement<br />

slabs; 4- geotextile in the embankment<br />

foundati<strong>on</strong>; 5- plastic foam of reduced thiokness<br />

In oaaea when It Is necessary to preserve the<br />

embankment soil in the frozen state without an<br />

increaee in the embankment height (design soheme<br />

1) the we is made of the heat-insulating<br />

layers of art if icial or natural materials<br />

(Fig.2) laid in the embanbent foundati<strong>on</strong>.<br />

To lower the n<strong>on</strong>-uniformity of the embanlanent<br />

- .-<br />

1457

settlement up to an admissible limit it is re- and separating geotexfile interlayers. The emquired<br />

to reduce elther (1) a magnitude of the bankment height and structure are speoified 0x1<br />

settlement or (2) a degree of its noa-uniformi- the baais of oompu.tati<strong>on</strong>s according to the QOnty<br />

that is achieved, respectively, either by difi<strong>on</strong>a of enow-drifting, thawing, admiaaible<br />

lowering a depth of thawing by means of heat- settlement, and stability of the embanlanent.<br />

-insulating interlayers or by reinforairw the<br />

embanbent foundati<strong>on</strong> by geotextile materials.<br />

This case corresp<strong>on</strong>ds with design scheme 2,<br />

When the lower layers of the embankment are ,<br />

built from hard-frozen soils oompxessible at<br />

thawing (design sohemes 3 and 4) geotextile<br />

envelopes or semi-envelopes combined (if required)<br />

with heat-insulating layers (deai n soheme<br />

3) are wed as etruotural elements fFigs.4<br />

ana 5).<br />

Fig.4 Strwture of the embankment with geotertile<br />

interlayers and envelopes: 1- aand; 2- pavement<br />

slabs; 3- geotextile envelope; 4- fro-<br />

5en lumpy soil<br />

Pig.5 Structure of the sand embankment with<br />

heat-insulat ing interlayera and semi-envelopes<br />

of gsotextile: I- sand; 2- pavement slabbs;<br />

3- plastio foam; 4- peat; 5- geotextile semienvelopes;<br />

6- lumpy soil<br />

coNcLmIoNs<br />

Natmal c<strong>on</strong>diti<strong>on</strong>a of the northern regi<strong>on</strong>s of<br />

West Siberia are extremely unfavourable fox road<br />

a<strong>on</strong>structl<strong>on</strong>. The main difficulties are<br />

c<strong>on</strong>diti<strong>on</strong>ed by a l<strong>on</strong>g cold period the neoeeaity<br />

to build the embankments from h e Pxoaen<br />

soil c<strong>on</strong>siderable embanment settlements at<br />

thawing both filled-ug soil and natwal founbti<strong>on</strong>.<br />

To raise the stability of the embankment<br />

in summer period without an incseage in<br />

the earthwork volumes it is recommended to we<br />

heat-insulating layers as well as reinforcing<br />

1458

REFLECTION SEISMIC EXPLORATION AND<br />

DATA PROCESSING IN COLD REGIONS<br />

E Porturas<br />

Divisi<strong>on</strong> of Petr. Eng. and Appl. Geophysics, The Norwegian<br />

Institute of Technology, Norway<br />

SYNOPSIS Today studies in cold regi<strong>on</strong>s are of great interest because of their potential<br />

ec<strong>on</strong>omic resources. This paper presents an up-to-date analysis of multichannel seismic reflecti<strong>on</strong><br />

methods and data processing problems. The applicati<strong>on</strong> of reflecti<strong>on</strong> seismic methods meets particular<br />

difficulties which are not found elsewhere. The major questi<strong>on</strong> is how the frozen ground<br />

thickness and frost breaks affect the seismic sources and wave propagati<strong>on</strong>. The frozen ground<br />

acts in the same way as weathering z<strong>on</strong>es do <strong>on</strong> land seismics, or as a hard sea floor in marine<br />

operati<strong>on</strong>s, very similar to the explorati<strong>on</strong> of transiti<strong>on</strong> z<strong>on</strong>es. The seismic data processing is<br />

directed towards optimizing data quality where noise and spurious events, which tend to mask<br />

reflecti<strong>on</strong>s of interest, must be attenuated. The success of any geophysical method in cold<br />

regi<strong>on</strong>s will rely <strong>on</strong> its ability to delineate boundaries and thickness of the frozen ground.<br />

Therefore the understanding of permafrost phenomena, glacial drift and related geological factors<br />

is necessary to achieve good results for resource explorati<strong>on</strong> and engineering purposes.<br />

INTRODUCTION<br />

Increased attenti<strong>on</strong> is being focused <strong>on</strong><br />

explorati<strong>on</strong> in "fr<strong>on</strong>tier" areas of the world.<br />

These include regi<strong>on</strong>s which lie above high<br />

latitudes with permafrost and ice occurrence,<br />

here these z<strong>on</strong>es are named "cold regi<strong>on</strong>s".<br />

The most comm<strong>on</strong> methods applied in the evaluati<strong>on</strong><br />

of cold regi<strong>on</strong>s include reflecti<strong>on</strong>,<br />

refracti<strong>on</strong>, spot bathymetric soundings and<br />

pulse techniques. other sets of geophysical<br />

data' have been obtained by airborne magnetometric,<br />

heat flow, gravimetric measurements,<br />

and limited shallow coring.<br />

Radio echo soundings have been d<strong>on</strong>e in the<br />

Antarctic ice uding very str<strong>on</strong>g sources such<br />

as pulse-modulated radar. This method has<br />

limitati<strong>on</strong>s because the echos are affected by<br />

refracti<strong>on</strong> phenomena <strong>on</strong> the ice surface, ice<br />

shelves, crevasses and cracks at the bottom of<br />

the ice. Recently, the measurements of ice<br />

thickness have been d<strong>on</strong>e using helicopters<br />

with a mounted impulse radar unit. The helicopter<br />

fly 3 to 5 m above the ice with a velocity<br />

of 5 to 10 knots. The energy is<br />

reflected partially by the ice and by the<br />

interface between the bottom of the ice and<br />

sea water. The difference between this technique<br />

and the seismic method is the nature of<br />

the energy Source. Electromagnetic waves<br />

being used for the radar technique as opposed<br />

to sound waves for the seismic method.<br />

In cold regi<strong>on</strong>s, the seismic data available is<br />

sparse because of the harshness of the<br />

envir<strong>on</strong>ment and the unstable nature of the ice<br />

cover. Its disc<strong>on</strong>tinuity does not allow the<br />

use of land techniques and maneouvering of<br />

marine seismic vessels requires ice-breakers.<br />

Therefore seismic explorati<strong>on</strong> in cold regi<strong>on</strong>s<br />

is a peculiar mix of land and marine operati<strong>on</strong>s.<br />

The studies in cold regi<strong>on</strong>s deal with similar<br />

problems found when exploring transiti<strong>on</strong><br />

z<strong>on</strong>es. For instance, the areal extensi<strong>on</strong> of<br />

frozen ground and transiti<strong>on</strong> z<strong>on</strong>es varies<br />

areally and depends largely <strong>on</strong> depositi<strong>on</strong><br />

envir<strong>on</strong>ments, temperature ( near the freez ing<br />

point), salinity, history of burial and exposure,<br />

depth, proximity to surface, water<br />

saturati<strong>on</strong>, lithology and stress factors.<br />

Seismic reflecti<strong>on</strong> techniques are a reas<strong>on</strong>able<br />

approach to the investigati<strong>on</strong> of cold regi<strong>on</strong>s<br />

both in terms of ec<strong>on</strong>omy and time. They provide<br />

useful informati<strong>on</strong> for estimati<strong>on</strong> of ice<br />

thickness, ice bounded, and subsea permafrost<br />

extensi<strong>on</strong>. These data can be used for design<br />

and c<strong>on</strong>structi<strong>on</strong> of mine shafts, designing<br />

suitable foundati<strong>on</strong> sites, oil and gas Eacilities<br />

and to calculate the forces exerted by<br />

ice floes against structures such as platforms<br />

set <strong>on</strong> the seabed. Seismic explorati<strong>on</strong><br />

assists in the determinati<strong>on</strong> of compressi<strong>on</strong>al<br />

wave velocities and in acoustic log interpretati<strong>on</strong><br />

in permafrost.<br />

The amount of work d<strong>on</strong>e in cold regi<strong>on</strong>s is<br />

large and most of the literature is scattered.<br />

In this paper a brief presentati<strong>on</strong> of the main<br />

problems found both for data acquisiti<strong>on</strong> and<br />

during the seismic data processing is given.<br />

The examples presented include mostly synthetically<br />

generated data and they illustrate the<br />

main steps followed to process a seismic secti<strong>on</strong>.<br />

1459

SEISMIC DATA ACQUISIT I ON<br />

Sei-smic data acquisiti<strong>on</strong> programmes needs to<br />

be oriented towards solving the acoustic impe-.<br />

dance problems encountered when dealing with<br />

ice covered and permafrost z<strong>on</strong>es. The most<br />

important parameters to be c<strong>on</strong>sidered are .<br />

geoph<strong>on</strong>e or hydroph<strong>on</strong>e spacing and signal frequency.<br />

The complexity of the subsurface will<br />

affect the source performance. Several energy<br />

sources such as airguns, explosives (dynamite,<br />

geoflex) , sparkers and boomers have been<br />

applied * The basic criteria for selecting the<br />

energy murce is its capacity to differentiate<br />

materials under the ice cover and permafrost,<br />

for instance they have different compressi<strong>on</strong>al<br />

velocities and when material become icebounded,<br />

the velocities will increase.<br />

Tests using various volume charges of explosives<br />

have been performed. Normally, the explosives<br />

are placed beneath the ice OF deep in<br />

the frozen ground with the purpose of maximizing<br />

the downward transmitted energy. This<br />

technique is pr<strong>on</strong>e to several difficulties.<br />

The holes usually refreeze, then the geoph<strong>on</strong>es<br />

are lost. The holes can cross and drain brine<br />

lenses, then seawater invades the hole and<br />

readily freezes and the geoph<strong>on</strong>e will be<br />

trapped. Experimental tests using dynamite<br />

charges of 10 lbs or greater det<strong>on</strong>ated at<br />

depths less than 0.5 m shows a tendency to<br />

create ice breaks, fractures and frost breaks.<br />

The frost breaks c<strong>on</strong>stitute a major problem<br />

during data acquisiti<strong>on</strong>. They originate when<br />

explod inq dynamite triggers, cracking the ice<br />

outwards from the det<strong>on</strong>ati<strong>on</strong> point. These<br />

minute cracks form in the ice of the per-<br />

mafros t and ac t as sec<strong>on</strong>dary sources Of<br />

seismic energy which obliteiate subsurface<br />

energy arriving at the same time. Experimental<br />

work has shown that volume charges between<br />

1 to 2 lb and det<strong>on</strong>ated between 5-10 m do not<br />

tend to create frost breaks.<br />

The logistics for a seismic survey in cold<br />

regi<strong>on</strong>s are very important. For a 12 geoph<strong>on</strong>e<br />

trace and 24 channels group interval, 142 rn<br />

spread, using a charge size of 25 lb, the<br />

energy necessary per mile of survey is 162.5<br />

lbs of dynamite. From human safety and ecological<br />

c<strong>on</strong>siderati<strong>on</strong>s it is recommended to use<br />

small charges. . Another difficulty encountered<br />

in cold regi<strong>on</strong>s is the ice flow camps power<br />

which restricts available sources. Noise<br />

results from water ground loops and due to<br />

mechanical vibrati<strong>on</strong>s of diesel or electric<br />

generators.<br />

The receivers are a source of low frequency<br />

strumming noise. This is created by vortex<br />

shedding of water flowing fast suspended<br />

hydroph<strong>on</strong>e cables. The hydroph<strong>on</strong>es are pr<strong>on</strong>e<br />

to strum oscillati<strong>on</strong>s.<br />

The recording systems used in the past were<br />

analogue. Today seismic data are gathered<br />

mostly digitally. Analogue methods have a<br />

seriously limited dynamic range. Digital<br />

single channel systems offer seismic records<br />

of poor quality and are not powerful enough to<br />

penetrate the structurea sufficiently. Therefore<br />

multichannel systems are preferable. The<br />

<strong>on</strong>ly problem related to this way of recording<br />

seismic data is the often erratic directi<strong>on</strong> of<br />

drift of the ice flows.<br />

A standard magnetic tape format widely used to<br />

SOURCES<br />

PROBLEMS<br />

COEMENTS<br />

- Sparkers<br />

- Boomers<br />

- Airguns<br />

up to 600 cu in<br />

Re ceitet either<br />

suspended or ice<br />

mounted.<br />

- Exploaives<br />

Re ceivers either<br />

suspended or mounted.<br />

- Small charges up to 25 lbs<br />

- 25' of 40 grain<br />

"Aquaf lex"<br />

- Vibrators<br />

Onshore<br />

Deep water<br />

- Weap<strong>on</strong>s, 22 caliber rifle<br />

Faster for quick-look No possibility<br />

interpretati<strong>on</strong> /to enhance data quality<br />

- Susceptible to vibrati<strong>on</strong>al pickup<br />

from power generator and man-made<br />

camp noise<br />

- Heave - thumping instruments flexes<br />

the ice- Spoils data quality.<br />

- Good data offshore seaward/<br />

lesser depth:noise<br />

- Easy to drill <strong>on</strong> ice<br />

- For explorati<strong>on</strong>lsts/envic<strong>on</strong>muntalists<br />

- Ecologists/point source<br />

- Better <strong>on</strong>ehore<br />

- Dlsadvantage: direct coupling to the<br />

ice or frozen ground<br />

Difficult to use in<br />

transiti<strong>on</strong> z<strong>on</strong>es<br />

- Extreme cold can cause<br />

temperamental variati<strong>on</strong>!<br />

- Airguns do not work wel:<br />

if there is nor enough<br />

good c<strong>on</strong>tact with water<br />

- Offshore flqating ice<br />

- Cable towing<br />

- Trenching equipment<br />

- Frost breaks<br />

- Ice fractures<br />

- fce breaks<br />

- Flexural wave noise<br />

I <strong>on</strong>ly for seas<strong>on</strong>al<br />

Operati<strong>on</strong>s.<br />

Requires good<br />

weather.<br />

- Needs proper maintenanca<br />

- Very difficult to w e<br />

eeismic arrays.<br />

- Holes drilled <strong>on</strong> ice or<br />

charges placed in water<br />

- Charges preferable belos<br />

permafrost<br />

- At least 10' below lower<br />

ice<br />

- Inferior shallow data<br />

quality<br />

:ood data .<br />

Fig. 1. Synopsis of seismic data acquisiti<strong>on</strong> parameters applied<br />

in cold regi<strong>on</strong>s.<br />

1460

ecord seismic data in cold regi<strong>on</strong>s is the<br />

format SEGA but other tape formats such as<br />

SEGB are also used. The energy source suitability<br />

depends <strong>on</strong> its ability to delineate<br />

permafrost, changes in lithology and lateral<br />

extensi<strong>on</strong> of the frozen ground. If data is<br />

not acquired properly, <strong>on</strong>ly limited improvement<br />

in resoluti<strong>on</strong> can be achieved during the<br />

processing. Figure 1 shows a synopsis of<br />

sources reported to be used in the seismic<br />

explorati<strong>on</strong> of cold regi<strong>on</strong>s and Figure 2 shows<br />

the surface and subsurface coverage diagram of<br />

a seismic survey.<br />

Fig. 2,<br />

DATA PROCESSING<br />

...........<br />

............ c'w *r 8p4<br />

..........<br />

._ CDP br sP7<br />

..........<br />

._ CDP Cr 8P w<br />

~ ~ ~ ~ 0 ~ ~ ~ 0 0<br />

-mm* mcm- mmcm tmm<br />

YI - I trace, tr.W sy I<br />

.................. 1 ...................<br />

TAPER OFF rww ON<br />

ZONE<br />

$ 2ME<br />

Diagram showing surface and subsurface<br />

coverage for a aeismic programme<br />

where Ar = 2AS ana with 10 receivers.<br />

The seismic data processing sequence for cold<br />

regi<strong>on</strong>s is similar to marine rather than land<br />

seismics, but it suffers the courses of both.<br />

Figure 3 shows a processing scheme adapted to<br />

treat data from fr<strong>on</strong>tier areas; The compulsory<br />

steps are illustrated using synthetically<br />

generated examples (Figures 4-10). The<br />

signal needs to be enhanced to a certain level<br />

of resoluti<strong>on</strong>, this is d<strong>on</strong>e at the processing<br />

center .<br />

The primary goal in data processing is to<br />

enhance and discriminate primary reflecti<strong>on</strong>s<br />

from unwanted noise events. By means of data<br />

processing, coherent and random noise must be<br />

removed from the seismic secti<strong>on</strong>. In ice-pack<br />

envir<strong>on</strong>ments, the worst problem is multiples.<br />

Since the ice skin reflects the energy much<br />

more eEfectively than the water surface al<strong>on</strong>e,<br />

multiple energy is effectively wasted energy.<br />

It is very complicated to design arrays for<br />

data acquisiti<strong>on</strong> in harsh envir<strong>on</strong>ment areas.<br />

The additi<strong>on</strong>al amount of drilling would make<br />

it impractical, the random and coherent noise<br />

is treated in the processing center. A t the<br />

processing center the raw data is demultiplexed<br />

and rearranged into Comm<strong>on</strong> Depth point<br />

gather. Figure 4 shows a synthetic generated<br />

shot and its corresp<strong>on</strong>ding CDP gathers.<br />

During data processing, several algorithms are<br />

tested to find an optimal sequence for the<br />

survey.<br />

Dealing with phase differences due to the different<br />

source signatures takes a good part of<br />

the time.<br />

Decisi<strong>on</strong>s are taken at different parts in the<br />

processing sequence. When transiti<strong>on</strong> z<strong>on</strong>es<br />

are invisible seismically and if cannot be<br />

well delineated <strong>on</strong> the basis of the seismic<br />

wavelet characteristics, it is recommended<br />

more testing to restore weak frequency comp<strong>on</strong>ents<br />

to a certain level of interpretability.<br />

A crucial step during the seismic data<br />

processing is the estimati<strong>on</strong> of velocities for<br />

normal moveout correcti<strong>on</strong>. This d<strong>on</strong>e by<br />

interpreting the velocity spectra (Figure 6).<br />

One important step is to test which gain functi<strong>on</strong><br />

can be used to compensate €or energy<br />

losses downwards, Figure 5 shows several gain<br />

functi<strong>on</strong>s, the purpose is to make the time<br />

series stati<strong>on</strong>ary previous to further processing.<br />

The velocity analysis has a great deal of<br />

influence both <strong>on</strong> depth and velocity gradient<br />

estimati<strong>on</strong>s, It also influences the final<br />

stacked secti<strong>on</strong>. Figure 7 shows the velocity<br />

effects both <strong>on</strong> CDP's and in the stack. It<br />

is desirable to choose the most optimal velocities<br />

otherwise good resoluti<strong>on</strong> will not be<br />

achieved. In fr<strong>on</strong>tier areas the measurement<br />

of velocities are performed in temperatures<br />

ranging from 20oC to -36oC. In this range of<br />

temperatures the materials behave differently<br />

but as a rule the velocities in water<br />

saturated rocks will increase with decreasing<br />

temperature, while in dry rocks it is nearly<br />

temperature independent.<br />

In the velocity spectra analysis the shape of<br />

the velocity functi<strong>on</strong> usually increase as a<br />

fun.cti<strong>on</strong> of time and as a functi<strong>on</strong> of lithology<br />

in the underground. However it can be<br />

affected by numerous factors such as the<br />

inherent physical c<strong>on</strong>diti<strong>on</strong>s of the frozen<br />

ground. When short arrays are used during<br />

data acquisiti<strong>on</strong>, poor resoluti<strong>on</strong> is expected.<br />

Source dec<strong>on</strong>voluti<strong>on</strong> algorithms are tested and<br />

designed to suppress the surface ghost and<br />

multiples, which tend to mask reflecti<strong>on</strong>s of<br />

interest. This inverse filtering process must<br />

be adapted carefully to the problem in the<br />

case of transiti<strong>on</strong> z<strong>on</strong>es. Migrati<strong>on</strong> is<br />

applied in order to move reflecti<strong>on</strong>s to their<br />

correct positi<strong>on</strong>s. Figure 8 shows a stack<br />

resp<strong>on</strong>se and its corresp<strong>on</strong>ding migrated secti<strong>on</strong>.<br />

Finally a good set of display parameters<br />

must be chosen for the final seismic secti<strong>on</strong><br />

(Figure 9).<br />

1461

---I I<br />

*4<br />

5*<br />

FLOW CHART<br />

CWMENTS<br />

DEMULTIPLEXING EUITING * IMX: Reordering field into data<br />

channel-time sequential.<br />

----<br />

Editing: bad traces or shots are<br />

1 remwd prior to further processing.<br />

m<br />

""_ I DATA UXDUCTION - Channel or/and shot s mti<strong>on</strong><br />

L I<br />

-A BcsamrJli*g*<br />

* SCAL: Ibp<strong>on</strong>ential gain or spherical<br />

divergence for gain recovety.<br />

- STAT! Compulsory for the transiti<strong>on</strong><br />

x<strong>on</strong>es. correcti<strong>on</strong> both for source1<br />

receiver poaiti<strong>on</strong> td a datum level.<br />

r-------l<br />

I DECONVOLUTION > I<br />

I DECON DBS<br />

I<br />

L-"""l<br />

- NPO named, picslica filtering.<br />

F-K filter<br />

- Gemtry-Comwn Depth Point<br />

techniqua-c<strong>on</strong>figurati<strong>on</strong> dapendent. ,<br />

- DECON<br />

Inverse filtWiUg to remove<br />

predictable eventm/coherent noise.<br />

F"""7<br />

I<br />

Dip moveout<br />

DUO<br />

I<br />

I<br />

L"""J<br />

r------1 8<br />

Normal Moveout<br />

STACK 8*<br />

p""<br />

1<br />

- WO-correcti<strong>on</strong> for offset aproading.<br />

- Trace aeroing of unwanted tail affects'.<br />

- IIK): king at tha right time at<br />

the right place.<br />

- Frequancp filtering.<br />

- MIG: mtatiatical or deterdniotic.<br />

Spatial and temporal repositi<strong>on</strong>ing<br />

of reflecti<strong>on</strong>a.<br />

- DISP: Filtered stack.<br />

Migrated stack.<br />

Plota can be taken at any step1<br />

rndicates figure number vhich illustrates<br />

"- Stippled area show opti<strong>on</strong>al algorithms.<br />

this step.<br />

Fig. 3. Proposed seismic data processing scheme for cold regi<strong>on</strong>s.<br />

EXPLORATION PROBLEMS<br />

The reflecti<strong>on</strong> seismic method provides clues<br />

to the presence of frozen ground because of<br />

its characteristic high velocity. However the<br />

base of permafrost is difficult to observe if<br />

the quality of seismic data is not optimal.<br />

The thickness of the frozen ground has a special<br />

effect and acts as a variable statics<br />

anomaly which can lead to wr<strong>on</strong>g interpre ta-<br />

ti<strong>on</strong>. Methane hydrates may be c<strong>on</strong>centrated at<br />

or near the base of permafrost z<strong>on</strong>e, 80 delineati<strong>on</strong><br />

of the permeafrost is important,<br />

because of the potential danger inherent in<br />

drilling in hydrate z<strong>on</strong>es.<br />

The area and depth of permafrost can cause<br />

scattered and broadside noise. Good data can<br />

be acquired if the group intervals, geometry,<br />

and source are well designed.<br />

1462

1463

To deal with the complexity found in cold<br />

regi<strong>on</strong>s, the low frequency ground roll can be<br />

treated using multichannel filtering. This is<br />

the'<strong>on</strong>ly way to discriminate signal from noise<br />

lying at the same frequency. Figure 10 shows<br />

an example of 2-D filtering. In other cases<br />

ice wave interference is greater than the<br />

reflected signal; therefore str<strong>on</strong>g noise cancellati<strong>on</strong><br />

during processing is required. The<br />

final seismic secti<strong>on</strong> will in all cases be<br />

affected by significant residuals because of<br />

the intensity and local variability of the ice<br />

thickness which affects surface wave propagati<strong>on</strong>.<br />

"A,. ....<br />

.. .<br />

.....I *..I*,,, C I I A I, ...I<br />

It is all the time necessary to test at which<br />

frequency level the energy lies in the data.<br />

Figure 11 shows a filtering operati<strong>on</strong> d<strong>on</strong>e <strong>on</strong><br />

CDP's.<br />

Fig. 9.<br />

Display types for seismic data.<br />

Variable area wiggle, variable area<br />

and wiggle traces <strong>on</strong>ly (from left to<br />

Wright).<br />

Fig. 11. Examples of filtering <strong>on</strong> a single<br />

CDP . Not ice the improvemen t/d amage<br />

to the seismic reflecti<strong>on</strong>s.<br />

The subsea permafrost (high velocity media)<br />

acts as an efficient wave guide which produces<br />

str<strong>on</strong>g reflected and refracted reverberati<strong>on</strong>.<br />

Therefore, data processing needs special<br />

.attenti<strong>on</strong> when applying dec<strong>on</strong>voluti<strong>on</strong>.<br />

It should be noted that permafrost can vary in<br />

depth, and the upper secti<strong>on</strong> can be affected<br />

by seas<strong>on</strong>al variati<strong>on</strong>s and l<strong>on</strong>g term trends of<br />

regressi<strong>on</strong> and advance, (ice cover). Therefore<br />

extensive testing is necessary, since<br />

normal schemes will not generally work with<br />

this type of data.<br />

Looking forward, experimental work related to<br />

the applicati<strong>on</strong> of the reflecti<strong>on</strong> seismic<br />

method in cold regi<strong>on</strong>s, acoustic impedance<br />

variati<strong>on</strong> as a functi<strong>on</strong> of offset remains to<br />

be d<strong>on</strong>e. Transiti<strong>on</strong> z<strong>on</strong>es associated with<br />

permafrost are ideal candidates for observing<br />

effects of increased reflecti<strong>on</strong> coefficients<br />

and wave shape modificati<strong>on</strong> with offset.<br />

. I<br />

CONCLUSIONS<br />

In spite of the c<strong>on</strong>siderable research already<br />

d<strong>on</strong>e, cold regi<strong>on</strong>s still remain the least<br />

known. Technology is evolving which permits<br />

work in harsh envir<strong>on</strong>ments; however, further<br />

advances must be made to acquire the comprehensive<br />

seismic data needed to develop its<br />

resources. Seismic explorati<strong>on</strong> has been<br />

limited in quality, since it is <strong>on</strong>ly recently<br />

that array technologies have been used.<br />

ments Although in remote coverage sensing is sparse, and submarine-mounted<br />

future develop-<br />

systems must be c<strong>on</strong>sidered to solve the major<br />

c<strong>on</strong>straints in acquisiti<strong>on</strong> and data processing.<br />

Finally, good data will be useful<br />

for producing more accurate interpretati<strong>on</strong>s<br />

and to provide a better insight into detecti<strong>on</strong><br />

and locati<strong>on</strong> of potential drilling hazards and<br />

for site studies.<br />

Fig. 10.<br />

Spectrum (Wright) taken from a shot<br />

(left) ta design a 2-D filter. Useful<br />

when random and coherent noise<br />

masks the seismic data.<br />

1464

AKNOWLEDGEMENTS<br />

I would like to thank Prof. B jarn Ursin for<br />

the comments, GECO has provided computing<br />

facilities and to Anne-Lise Brekken for typing<br />

the manuscript. Finally<br />

for his support.<br />

to Prof. J<strong>on</strong> Kleppe<br />

REFERENCES<br />

Baggeroer, A.B. h Duckworth, G.L. (1983).<br />

Seismic Explorati<strong>on</strong> in the Artic Ocean.<br />

Geophysics: TLE, (2) I 10, 22-27.<br />

Brown, A. (1983). ' Seismic <strong>on</strong> the Pack ice.<br />

Geophysics: TLE, (2), 10, 12-16.<br />

Harris<strong>on</strong>, C.H., (1970). Rec<strong>on</strong>structi<strong>on</strong> of<br />

subglacial relief from radio echo sounding<br />

records. Geophysics, (35), 6, 1099-1115.<br />

Justice, H.J. 6 Zuba, Ch. (1986). Transiti<strong>on</strong><br />

z<strong>on</strong>e reflecti<strong>on</strong>s and permafrost analysis.<br />

Geophysics, (51) , 5, 1075-1086.<br />

Poulter, T.C! (1951). A discussi<strong>on</strong> <strong>on</strong> seismic'<br />

soundings of glaciers. Geophysics, (16).<br />

535-.537.<br />

Proubasta, D. (1985). Ice saw - an incisive<br />

soluti<strong>on</strong> to seismic noise. Geophysics: TLE,<br />

(4)1 10, 12-23.<br />

Rackets, H.M. (1971). A low-noise seismic<br />

method far use in permafrost regi<strong>on</strong>s. Geophysics,<br />

(36), 6, 1150-1161.<br />

Senneset, K. (1986). Landbasert virksomhet -<br />

utfordring fra permafrost. NORD-86.<br />

Timur, A. (1968). Velocity of compressi<strong>on</strong>al<br />

waves in porous media at permafrost temperatures.<br />

Geophysics, (351, 4, 584-595.<br />

1465

PROBLEMS OF ARCTIC ROAD CONSTRUCTION<br />

AND MAINTENANCE IN FINLAND<br />

S. Saaretainen and J. Vaskelainen<br />

Technical <strong>Research</strong> Centre of Finland, Geotechnical Laboratory<br />

.33BLEMS OF ARCTIC ROAD CONSTRUCTION AND EIAINTENANCE IN FINLAND<br />

SYNOPSIS. In the paper, the problems induced by the cold climate to road maintenance and<br />

c<strong>on</strong>structi<strong>on</strong> in Northern Finland are described and discussed. Methods for the improvement of road <strong>on</strong><br />

permafrost, frost heave, icing and snow accumulati<strong>on</strong> are presented. According to the experimental<br />

design and c<strong>on</strong>structi<strong>on</strong>, ec<strong>on</strong>omical and technically feasible soluti<strong>on</strong>s can be achieved by the<br />

applicati<strong>on</strong> of developed thermodynamic background.<br />

1. INTRODUCTION<br />

Finland is located between the latitudes 60<br />

and 70 in the northern hemisphere. The mean<br />

annual air temperatures vary from + 6 OC in the<br />

south to -2.. .-3 OC in the north of Finland<br />

(fig. 1). The climate is heavily affected by<br />

the Golf stream, which smoothes the air<br />

temperature variati<strong>on</strong>. In eastern parts of the<br />

country, the c<strong>on</strong>tinental climatic effects are<br />

more distinct, and the seas<strong>on</strong>al temperature<br />

variati<strong>on</strong>s are relatively larger.<br />

Due to the l<strong>on</strong>g cold period and relatively low<br />

mean temperature, the effects of frost and Soil<br />

freezing are dominant in the behaviour of<br />

different structures exposdd to freezing, i.e.<br />

soil structures, foundati<strong>on</strong>s, hydraulic<br />

Structures and others. Due to the fact that the<br />

ec<strong>on</strong>omical activity in the country is<br />

c<strong>on</strong>centrated to the southern z<strong>on</strong>e, the basic<br />

experience of c<strong>on</strong>structi<strong>on</strong> and behaviour of<br />

structures is mostly based <strong>on</strong> practice in a<br />

relatively mi,lder climate.<br />

Because of the growing interest in cold regi<strong>on</strong>s<br />

engineering and the problems reported in the<br />

North, a development project was established to<br />

study the character and degree of the problems<br />

caused at the roads by extreme climatic c<strong>on</strong>diti<strong>on</strong>s<br />

in Finland. This study was started with a<br />

general study <strong>on</strong> the problems involved in road<br />

c<strong>on</strong>structi<strong>on</strong> and maintenance in Northern<br />

Lapland in 1905. The initiative and financial<br />

support were given by the Finnish Roads and<br />

Waterways Administrati<strong>on</strong> (TVH) and the Road<br />

District of Lapland. One resp<strong>on</strong>sible<br />

participant in the project was VTT,<br />

Geotechnical laboratory, which was resp<strong>on</strong>sible<br />

for the frost investigati<strong>on</strong>s and frost engineering<br />

design in the project, and other<br />

participants were the Road District of Lapland,<br />

which was resp<strong>on</strong>sible for site investigati<strong>on</strong>s,<br />

test c<strong>on</strong>structi<strong>on</strong> anrl the m<strong>on</strong>itoring of the be-<br />

haviour of test structures, and C<strong>on</strong>sulting<br />

Engineers Viatek Oy, which was resp<strong>on</strong>sible for<br />

the planning and road engineering design of the<br />

structures.<br />

The goals of the project were to produce<br />

methods for road rec<strong>on</strong>structi<strong>on</strong> feasible in<br />

these c<strong>on</strong>diti<strong>on</strong>s to be used as a technical<br />

basis in the north, and to apply the modern<br />

cold regi<strong>on</strong>s engineering approach in the<br />

soluti<strong>on</strong> of these specific problems. From this<br />

point of view, if carried out <strong>on</strong> exact methods<br />

of analysis, the experience gained might be<br />

used to develop structures in other cold z<strong>on</strong>es<br />

as well for the more southern z<strong>on</strong>es as in the<br />

permafrost z<strong>on</strong>e.<br />

Fig. 1. Locati<strong>on</strong> of the investigati<strong>on</strong> area.<br />

1466

2. PROBLEllS CAUSED BY THE COLD CLIEIATE<br />

According to the reports from the local road<br />

maintenance organizati<strong>on</strong> and the observati<strong>on</strong>s<br />

al<strong>on</strong>g the road line, some typical problems were<br />

found (Saarelainen & Vaskelainen 1986):<br />

- excessive snow accumulati<strong>on</strong> and<br />

snowdrift,<br />

- aufeis formati<strong>on</strong> due to the freezing of<br />

ground water and surface runaff at the<br />

road<br />

- excessive uneven frost heave<br />

- thaw settlement and damages of pavement<br />

<strong>on</strong> local palsa mounds (sporadic<br />

permafrost)<br />

- slope slides at steep fjell slopes.<br />

Host of the problems are c<strong>on</strong>nected to low<br />

winter temperatures. Some of the problematic<br />

processes are found in unc<strong>on</strong>structed terrain<br />

(palsas, ice formati<strong>on</strong>s, snow) while some<br />

problems result from human activity (frost<br />

heave, snow accumulati<strong>on</strong>, slope processes,<br />

icing caused by frozen road embankment etc.).<br />

They are c<strong>on</strong>sidered problems because of<br />

maintenance effort and costs.<br />

Some problems arise in c<strong>on</strong>necti<strong>on</strong> with strength<br />

losses of c<strong>on</strong>structi<strong>on</strong> materials due to<br />

freezing. Some minerals expand when freezing,<br />

resulting in structural changes in the<br />

material, and a loss of strength.<br />

3. PRINCIPLES OF THE TREATMENT OF THE PROBLEMS<br />

AND TEST CONSTRUCTION<br />

3.1. <strong>Permafrost</strong><br />

Palsas were found generally at wetlands with<br />

peat cover al<strong>on</strong>g the road line (Fig 2 ). The<br />

palsa formati<strong>on</strong> is caused by the difference in<br />

,thermal c<strong>on</strong>ductivity of frozen and unfrozen<br />

surface peat, which eliminates the heating<br />

effect of solar radiati<strong>on</strong> in summer <strong>on</strong><br />

peatlands, and thus causes permafrost process<br />

at z<strong>on</strong>es of mean annual air temperature close<br />

to -0 OC (e.g. SeppSlS 1985, Keyser et al.<br />

1984).<br />

At the studied secti<strong>on</strong> of the highway two<br />

locati<strong>on</strong>s were found, where permafrost was underlying<br />

the road embankment. At these<br />

locati<strong>on</strong>s the road has originally been built <strong>on</strong><br />

frozen ground with c<strong>on</strong>venti<strong>on</strong>al methods,<br />

without any special measures due to the<br />

permafrost. The original route was a modest<br />

pathway, which was improved for car traffic<br />

during the World War 11, and it was paved with<br />

emulsi<strong>on</strong> pavement in the beginning of 60'ies.<br />

During the test c<strong>on</strong>structi<strong>on</strong> it was found out<br />

that the road had suffered thaw settlement<br />

after paving about 1.8 m, which can be read<br />

from the successive repair pavement layers up<br />

to the total thickness of 1.8 m. During the<br />

soil investigati<strong>on</strong>s, laboratory tests <strong>on</strong><br />

undisturbed samples of underlying, permanently<br />

frozen peat showed a total thaw compressi<strong>on</strong> of<br />

70 8 under overburden pressure. Roughly these<br />

figures.show a mean annual thaw settlement<br />

about 60 - 70 mm, and mean annual thaw about<br />

100 mm. The length of the palsa secti<strong>on</strong> was<br />

about 100 m, and the depth of the frozen core<br />

was 7 - 8 m.<br />

Fig. 2. The palsa mound at Peera.<br />

As to the principle of test c<strong>on</strong>structi<strong>on</strong> it was<br />

decided to keep the permafrost i n frozen state.<br />

This was realized by increasing the thermal<br />

resistance of the embankment with insulati<strong>on</strong><br />

above the frozen core, to minimize the heat<br />

exchange with the atmosphere, and to minimize<br />

the heat effect of solar radiati<strong>on</strong> by using<br />

light-coloured pavement aggregate (white<br />

quartzite) to prevent the rise of surface<br />

temperature in summer. The design was based <strong>on</strong><br />

thermal computer analysis c<strong>on</strong>sidering actual<br />

material properties, limit c<strong>on</strong>diti<strong>on</strong>s and the<br />

cycle of seas<strong>on</strong>al mean temperatures. As a<br />

result it was stated that the thickness of the<br />

insulati<strong>on</strong> must be at least LOO mm to prevent ,<br />

thaw fr<strong>on</strong>t from penetrating through the<br />

c<strong>on</strong>structed layers into ice-rich subgrade<br />

(ADINA-T, Belander 1985). The time span of the<br />

analysis was 4 years (Fig. 3 ).<br />

The test c<strong>on</strong>structi<strong>on</strong> vas started with the<br />

removal of old pavement in November 1906. The<br />

surface was kept snowless over the winter, and<br />

the insulated structure was c<strong>on</strong>structed in<br />

April 1907. At the stage of c<strong>on</strong>structi<strong>on</strong> the<br />

underlying active layer was observed to be<br />

frozen to the permafrost table. The completi<strong>on</strong><br />

of the road profile was carried in summer 1907<br />

including the profiliny of the slopes with peat<br />

and the c<strong>on</strong>structi<strong>on</strong> of the new pavement. The<br />

structure is actually under m<strong>on</strong>itoring of thaw<br />

hepth, temperatures, frost heaves, settlements<br />

etc.<br />

Comparing with the c<strong>on</strong>venti<strong>on</strong>al soluti<strong>on</strong> of<br />

excavati<strong>on</strong> and filling, the test structure was<br />

evaluated to save building costs under these<br />

c<strong>on</strong>diti<strong>on</strong>s about 50 8. If the earlier observed<br />

settlement process is eliminated, the reducti<strong>on</strong><br />

in future maintenance and repair is expected to<br />

be remarkable,<br />

3.2. Seas<strong>on</strong>al frost<br />

On dry land areas at the site the ground<br />

freezes annually under the snow cover to the<br />

depth of 1-1,5 m. In the snowless areas the<br />

freezing depth may reach up to 2,5 - 3 in. The<br />

possibility of perennial frost is evident,<br />

because the variati<strong>on</strong>s of climate are rather<br />

c<strong>on</strong>siderable at these locati<strong>on</strong>s. At least<br />

according to the fr<strong>on</strong>t depth and temperature

INSULATED EMBANKMENT ON FROZEN PALSA (lnwlot1<strong>on</strong> lOQmm XPS1<br />

Fig. 3. Calculated seas<strong>on</strong>al thaw of the<br />

structure in Peera.<br />

measurements in summer 1986, it can be supposed<br />

that the perennial frost was probable. The<br />

frost heave at the locati<strong>on</strong>s investigated was<br />

ranging between 0-270 mm with a c<strong>on</strong>siderable<br />

variati<strong>on</strong>. The damages of pavement were found<br />

to c<strong>on</strong>centrate at locati<strong>on</strong>s where the relative<br />

deflecti<strong>on</strong> of the pavement was larger than<br />

about 10 pro mille. The ddmages were mainly I<br />

individual or systematic cracks and unevenness<br />

of the surface, and in minor amount netwise<br />

cracking, which is indicating loss in bearing<br />

capacity of the road structure.<br />

The subgrade at the locati<strong>on</strong>s of problematic<br />

frost heave c<strong>on</strong>sisted mainly of alluvial or<br />

glaciolacustrine silts, seilimented in the<br />

depressi<strong>on</strong>s of the terrain and overlain with<br />

peat cover. The ratio between the frost heave<br />

and corresp<strong>on</strong>ding-thickness of the frozen,<br />

frost susceptible soil was about 0,1-0,15. The<br />

segregati<strong>on</strong> potential of the subgrade (K<strong>on</strong>rad &<br />

Morgenstern, 1981), determined by backcalculati<strong>on</strong><br />

<strong>on</strong> observed frost heave and frost<br />

depth was of the order of 4-5 mm2/Kh. The<br />

analysis was carried out with a computer<br />

program based <strong>on</strong> the thermal balance at the<br />

freezing fr<strong>on</strong>t, which takes into account<br />

besides real material properties, also the heat<br />

flow through the frozen layer, the heat release<br />

in in-situ freezing and frost heave and heat<br />

flow from underlying ground (Saarelainen 1987).<br />

In laboratory frost heave tests, the segregati<strong>on</strong><br />

potential was determined <strong>on</strong> a procedure<br />

similar to that of K<strong>on</strong>rad (K<strong>on</strong>rad &<br />

Plorgenstern 1981). and the segregati<strong>on</strong><br />

potential was varying between 6,5-1,5 mm2/Kh<br />

when the load <strong>on</strong> the sample varied between 0-50<br />

kPa. The same order of magnitude can be observed.<br />

The test structure waG designed <strong>on</strong> tlle basis of<br />

observed behaviour using the <strong>on</strong>e dimensi<strong>on</strong>al<br />

program described above, with the maximum<br />

design frost heave of 50-70 mm, that can occur<br />

due to climatic variati<strong>on</strong>s <strong>on</strong>ce in ten years.<br />

The allowable design value is based <strong>on</strong> an<br />

asphalt pavement damage mapping earlier in<br />

Eastern Finland (VTT, 1904).<br />

At Peera, the structural layers were compiled<br />

according to the principle of testing the<br />

usability of the local, abundantly present,<br />

slighEly frost susceptible till. The till<br />

c<strong>on</strong>tains fines (fracti<strong>on</strong>

GRAVEL EMBANKMENT<br />

I PO<br />

35E , 3 5c , 553 1. PAVEMENT<br />

2. BASE COURSE<br />

4. SUBBASE.GRAVEL<br />

a) OLD PAVEMENT REMOVED<br />

b) OLD EMBANKMENT REFORMED<br />

-<br />

SCALE 0 1 2 3 4 5m<br />

TILL EMBANKMENT<br />

1. PAVEMENT<br />

2. BASE COURSE<br />

3. SUBBASE. GRAVEL<br />

6. SUBBASE,tlLL<br />

8.GEOTEXTILE<br />

b) OLD EMBANKMENT REMOVED<br />

-<br />

Fig. 4. Test road profiles at Peera SCALE ’ * 3’ ‘ ’‘<br />

TILL+GRAVEL EMBANKMENT<br />

8 00 1. PAVEMENT<br />

2 BASE COURSE<br />

’” ‘ Io<br />

, 3SUBBASE.GRAVEL<br />

a1 OLD PAVEMENT REMOVED<br />

b) OLD EMBANKMENT REFORMED<br />

Fig. 5. Till embankment with gravel isolati<strong>on</strong>.<br />

the problem results from the inefficient winter<br />

drainage of the road. In the road<br />

district of Lapland there was carried out a<br />

study about the remedial maintenance measures<br />

against the icing, and in this study were<br />

listed different methods to prevent the<br />

freezing of culverts. Most of these seemed to<br />

be of temporary value, because they caused<br />

F<br />

SCALE 0 1 2 3 I 5m<br />

seas<strong>on</strong>al operati<strong>on</strong> <strong>on</strong> the road line (insulati<strong>on</strong><br />

of the culvert ends. covers <strong>on</strong> the inflow, use<br />

of various thawing techniques etc).<br />

After the local investigati<strong>on</strong>, the following<br />

diagnosis could be made: the problems are<br />

basically caused by the ground water flow in<br />

winter at and across the road. The feasible<br />

soluti<strong>on</strong>s should include the maintaining of<br />

1469

positive temperature of the ground water flow<br />

across the road. This can be ensured by a<br />

winter culvert that should kept be unfrozen at<br />

frost free depth or by thermal insulati<strong>on</strong>. The<br />

ground water should be collected in drains at.<br />

upper terrain at a frost free depth and led to<br />

the winter culvert. The snowmelt that is the<br />

hydraulic design parameter, flows through the<br />

original large culvert. This is in spring time<br />

open and empty, if the winter flow is led via<br />

the winter culvert. The basic problem involved<br />

is to-catch the ground water in the terrain<br />

before freezing and to let it cross through the<br />

road line unfrozen. The design should c<strong>on</strong>sider<br />

the frost depth under the snow cover in upper<br />

terrain, and the frost free depth and hydraulic<br />

design of the winter culvert.<br />

This technique has been tested in 1986 at <strong>on</strong>e<br />

locati<strong>on</strong> of ground water icing, and at <strong>on</strong>e<br />

locati<strong>on</strong> of river icing. The structures needed<br />

proved to be relatively cheap, and according to<br />

the observati<strong>on</strong> in winter 1986-87 they seemed<br />

to be effective, too.<br />

Test c<strong>on</strong>structi<strong>on</strong> was c<strong>on</strong>tinued<br />

summer 1987<br />

at two other sites applying similar approach,<br />

but applying different drainage structures<br />

(i.e. vertical drainage mats instead of tubular<br />

drains). The behaviour will be m<strong>on</strong>itored at<br />

least <strong>on</strong>e winter to c<strong>on</strong>trol the effect.<br />

3.4 Snow c<strong>on</strong>trol<br />

The areas with snow problems are located at<br />

open tundra terrain, where the snow can flow<br />

freely with the eroding wind. According to<br />

literature informati<strong>on</strong>, the snow erosi<strong>on</strong> starts<br />

as the wind velocity exceeds about 5 m/s, and<br />

it increases roughly proporti<strong>on</strong>al to the cubic<br />

of wind velocity (Galuzin 1980). The<br />

accumulati<strong>on</strong> of snow, and the snow depth<br />

depends <strong>on</strong> the relative level of the locati<strong>on</strong><br />

in reference to the surroundings.<br />

The principle of design according to the snow<br />

depth is based <strong>on</strong> the finding that there is a<br />

reas<strong>on</strong>able correlati<strong>on</strong> of snow depth at a<br />

locati<strong>on</strong> with snow depth at the closest<br />

climatic stati<strong>on</strong> with l<strong>on</strong>g term observati<strong>on</strong>s<br />

<strong>on</strong> snow depth variati<strong>on</strong> (Bjalobzenskij 1983,<br />

Kuusisto 1984). Knowing the maximum depth at<br />

the locati<strong>on</strong> under study, the probability<br />

distributi<strong>on</strong> of local snow depth can be<br />

c<strong>on</strong>structed. In this manner it is possible to<br />

c<strong>on</strong>struct <strong>on</strong> a selected road line the design<br />

snow depth profile occurring at a certain<br />

probability, if the observati<strong>on</strong>s about maximum<br />

snow depth in <strong>on</strong>e observati<strong>on</strong> winter are<br />

available from the line in questi<strong>on</strong>. The<br />

design involves setting the level of the road<br />

above this level. If it is not technically<br />

possible, the snow accumulati<strong>on</strong> can be limited<br />

with the aerodynamic form of the road profile,<br />

smooth cutting etc (e.g. Norem 1975).<br />

The principle was tested <strong>on</strong>e at problematic<br />

secti<strong>on</strong>. The snow depth was measured in a<br />

perpendicular profile with the observati<strong>on</strong>s of<br />

wind directi<strong>on</strong> and speed <strong>on</strong>e at point, and in<br />

a terrain profile al<strong>on</strong>g the road line (Fig.<br />

6). According to the measurements and<br />

comparis<strong>on</strong> with the observati<strong>on</strong> series at the<br />

climatic stati<strong>on</strong>s at Kilpisjsrvi and Mu<strong>on</strong>io in<br />

Finland, it could be seen that the winter<br />

1985-86 corresp<strong>on</strong>ded, c<strong>on</strong>sidering the snow<br />

depth, to a winter repeated <strong>on</strong>ce in 10 years,<br />

and thus the observed snow depth profile is a<br />

representative design profile. At the test<br />

secti<strong>on</strong> this means an average snow depth of<br />

000 mm, with local maximums up to 1200 nun.<br />

r5Zs t<br />

SNOW DEPTH 5.3.1986<br />

JEAHKKASH<br />

PL 21bO PERPENDICULAR<br />

I GROUND 5-\.. . *530<br />

t'"'<br />

. 100" s l SO. o ~ _ 50ll l . 1W. R s ~ o<br />

LONG. PROFILE 15H LEFT FROM CL<br />

PERPENOICULAR.<br />

.. I<br />

-. SNXiEPTH<br />

1 "-:"-""<br />

"""_ ""*"- '.:.I," >7.L-I~<br />

VI 21. PL!L b ZOW 1160 2500 3000 3500<br />

Fig. 6. "he observed snow profile -at Jeahkkash.<br />

The test secti<strong>on</strong> was raised from the natural<br />

surface above the design level (Fig. 7 ). At <strong>on</strong>e<br />

part it was not possible to keep the level<br />

proper due to a local mound, and here the road<br />

was cut to the hill side. the perpendicular<br />

profile was formed smooth with l<strong>on</strong>g slopes of<br />

20 %. The shoulders of the embankment were<br />

rounded with a radius of 2 times the embankment<br />

height according to the Norwegian road design<br />

guidelines (Norem 1975).<br />

The test secti<strong>on</strong> was c<strong>on</strong>structed in summer 1987<br />

with the length 800 m. The development of snow<br />

c<strong>on</strong>diti<strong>on</strong>s, winds and the need of snow removal<br />

will be m<strong>on</strong>itored over the corning winter to<br />

c<strong>on</strong>trol the effect of the test design. The<br />

goal is to get rid of the snow fences earlier<br />

necessary <strong>on</strong> the line.<br />

4. CONCLUDING REMARKS<br />

The problems arising at a road line due to cold<br />

climate can be solved applying a sound<br />

thermodynamic approach. The applicability of<br />

the soluti<strong>on</strong>s depends str<strong>on</strong>gly <strong>on</strong> the validity<br />

of design data about the local ground c<strong>on</strong>diti<strong>on</strong>s,<br />

and the diagnosis about the reas<strong>on</strong>s of<br />

the processes involved. In this study, the<br />

methods of design are of prototypic character,<br />

and in order meeto other climatic c<strong>on</strong>diti<strong>on</strong>s,<br />

certain technical development must be applied<br />

to improve the ec<strong>on</strong>omy of the soluti<strong>on</strong> and<br />

structures. It is evident, pnyhow, that the<br />

basis of design can be used to solve similar<br />

problems in other parts of Northern Finland.<br />

1470

Fig. 7. The typical profile of the teat road at<br />

Jeahkkash.<br />

Because these problems can be recognized also<br />

in southern areas, the reas<strong>on</strong>s may be of<br />

similar nature, but due to the different scale,<br />

the practical soluti<strong>on</strong>s that are effective<br />

enough, may be different. The design of<br />

structures in a cold climate must c<strong>on</strong>sider the<br />

winter behavior of structures more canaciously<br />

than is being d<strong>on</strong>e today in the seas<strong>on</strong>al frost<br />

z<strong>on</strong>e. In this respect the exchange of experience<br />

with the specialists of c<strong>on</strong>structi<strong>on</strong> <strong>on</strong><br />

permafrost might be fruitful. The soils are<br />

comm<strong>on</strong>, and the physical proce,sses are in many<br />

cases similar. Difficulties lie mostly in<br />

proper techniques of investigati<strong>on</strong>s, and in the<br />

validity of the design models €or the problems<br />

to be solved.<br />

5 * REFERENCES<br />

Bjalobzenskij, G.V., Determinati<strong>on</strong> of snow<br />

cover thickness in the design of snow<br />

accumulati<strong>on</strong> at road embankments (in Russian).<br />

Avtomobilnye dorogi (1983), No.10.<br />

Galuzin V.M (ea.), C<strong>on</strong>structi<strong>on</strong> of streete in<br />

Northern c<strong>on</strong>diti<strong>on</strong>s (in Russian). Strojiedat,<br />

Leningrad 1980. 136 p.<br />

Helander R., The calculati<strong>on</strong>s for the thermal<br />

design of ground (in Finnish). Helsinki 1986.<br />

RIL, Publicati<strong>on</strong> K66-1986, p.23-66.<br />

Keyser A., Hode J. P Laforte M.A., Road<br />

c<strong>on</strong>structi<strong>on</strong> in palsa fields. Washingt<strong>on</strong> D.C.<br />

1984. Transportati<strong>on</strong> research record 978, p.<br />

26-36.<br />

K<strong>on</strong>rad J-H. h Morgenetern N.R., The segregati<strong>on</strong><br />

potential of a freezing Soil. Canadian<br />

Geotechnical Journal, Vol. 18 (1981), p. 482-<br />

491.<br />

Kuusisto E., Snow accumulati<strong>on</strong> and snowmelt in<br />

Finland. Helsinki 1984. Veaihallitus,<br />

Publicati<strong>on</strong> 55. 149 p.<br />

Norem H., Lokaliaering og utforming av veger i<br />

drivsnoe-omrlder. Oslo 1975. Statens vegvesen, .<br />

Veglaboratoriet, Meddelelse Nr. 49, 8. 19-31.<br />

Saarelainen S., Estimati<strong>on</strong> model for evaluati<strong>on</strong><br />

of frost depth and frost heave (in Finnish).<br />

Helsinki 1987. RIL, Publicati<strong>on</strong> K78-1987,<br />

p.205-210.<br />

Saarelainen S. & Vaskelainen J., Special<br />

problems in arctic road c<strong>on</strong>structi<strong>on</strong> and<br />

maintenance in Finland. Proc Int Symp. CIB <strong>on</strong><br />

Industrial planning, engineering and<br />

c<strong>on</strong>structi<strong>on</strong> under extreme circumstances,<br />

EspOO, Finland Nay 19-23, 1906, pp.171-181.<br />

Seppllg if., Palsa report (in Finnish).<br />

Preliminary work draft for the Arctic roadproject<br />

1985 (unpublished).<br />

TVH Road structure (in Finnish). Helsinki 1985.<br />

The Finnish Road= and Waterways Administrati<strong>on</strong>,<br />

Instructi<strong>on</strong>s €or the planning and design of<br />

roads, File B, Part IV.<br />

VTT. 1984. The frost investigati<strong>on</strong> at Karaikko<br />

and Opotta in Joensuu, Finland. -VTT,<br />

Geotechnical laboratory, and Road and traffic<br />

laboratory, Espoo 1984 (unpublished).<br />

1471

SOME ASPECTS OF FREEZING THE ICE PLATFORMS<br />

B.A. Savelied and D.A. Latah2<br />

1<strong>Research</strong> Institute of Engineering Site Investigati<strong>on</strong>s, Moscow, USSR<br />

2<strong>Research</strong> Institute of C<strong>on</strong>structing Main Pipings, Moscow, USSR<br />

SYNOPSTS<br />

A c<strong>on</strong>temporary state o the problem of freezing the artificial ice platforme<br />

is elucidated. Special attenti<strong>on</strong> ia given to the methods of calculating an artificial freezing<br />

of ice as well as to that of designing the artificial sfrucfuree asedng theis l<strong>on</strong>g-term operati<strong>on</strong>.<br />

One of tha promising trends related to making<br />

a aafa base to support drilling operati<strong>on</strong>s at<br />

the Arctic ehelf is that of c<strong>on</strong>structi<strong>on</strong> of<br />

artificial ice platforme allowing for their<br />

l<strong>on</strong>g-term operati<strong>on</strong>. The experiance in the<br />

USSR and abroad in applicati<strong>on</strong> of large icssoil<br />

masses as engineering rJtrmoturea enables<br />

to c<strong>on</strong>eider their wide applicati<strong>on</strong> to be quite<br />

practicable (Saveliev et al., 1983; Latalin,<br />

Gagarin, 1984). Temporary platform to aupport<br />

drllling operati<strong>on</strong>s are used by mome firms in<br />

Canada and US (Cox, 1979; Ekelund, haters<strong>on</strong>,<br />

1981 ; Ice Platforms, 1974) but notwithatanding<br />

the progrese achieved their applicati<strong>on</strong><br />

is presently limited for the purpose of explorati<strong>on</strong><br />

drilling and impossible for that of<br />

oil and gaa exploitati<strong>on</strong> due to a ahort-term<br />

period of operati<strong>on</strong>.<br />

A structure of ice and frozen ground whioh i~t<br />

c<strong>on</strong>etructed in Axotic regi<strong>on</strong>s ahould meet a<br />

number of requiremento. Ice used a8 a building<br />

material should be sound and the structure<br />

should c<strong>on</strong>geal to the reeertroir bottom BO that<br />

ice movementa or flows might not transfer it<br />

somewhere elee. The atrucfure should be durable<br />

enough and the length of ita exicrtence<br />

period ehould not be limited by <strong>on</strong>ly a wintar<br />

period.<br />

Physico-mechanical propertiee of ice ana ita<br />

compositi<strong>on</strong> are governed by thermodynamic c<strong>on</strong>diti<strong>on</strong>s<br />

of its formati<strong>on</strong>. Therefore, all the<br />

methods to ,build-up the ioe can be divided<br />

into three groups: aucoessive flooding of<br />

layers of water, drop spraying and volume<br />

freezing of a water medium.<br />

When freezing the ice by thin layers or by<br />

drop mpraying the water the system "ioe-bripe"<br />

ie somewhat of a eloead type by its parameters.<br />

Generati<strong>on</strong> and growth of cryetals of fresh ice<br />

will result in an increase in brine salinity<br />

which cannot be eliminated with masa transfer.<br />

The ice produced will either c<strong>on</strong>tain a large<br />

amount of brine of higher c<strong>on</strong>centrati<strong>on</strong> or<br />

posaeae a si ificant open porosity under<br />

drained c<strong>on</strong>d%<strong>on</strong>e, Nevertheleae, successive<br />

flooding and freezing of layers of water is<br />

<strong>on</strong>e of the most efficient methods of producing<br />

an artificial ice. By succesaive flooding and<br />

freezing of layere of water a temperature c<strong>on</strong>diti<strong>on</strong><br />

of an artificial ice mass is alfeoted<br />

by a number of facfore main of which ahould be<br />

c<strong>on</strong>sidered as follows: a rete of heat losa<br />

through coolhg and freezing of a flooded<br />

water layer 'of a particular fhickneas towards<br />

the atmosphere and underlying ice maw aa well<br />

a8 61 time period and rate of cooling a frozen<br />

ice layer and underlying ice maea.<br />

To build-up an ice maea with a pre-set temperatW8<br />

during the ahortest time poesible <strong>on</strong>e<br />

should fLnd an optimal combinati<strong>on</strong> of the<br />

given factors.<br />

The fofmsti<strong>on</strong> of an ice meBs by'succeasive<br />

flooding and freezing of water layers of a<br />

partioular'thicknase at ita fop aurfaccb ie<br />

performed in two stages (Latalin, 1986).<br />

1. Cooling of a frozen water layer and the<br />

whole of previourrly built-up ice mass c<strong>on</strong>sisting<br />

of i-layers during a time period,Ar<br />

(Fig. 11.-<br />

Fig.1 Temperature curve for a period<br />

of cooling an ice layer <strong>on</strong><br />

an ice cover<br />

1472

2. Freezing of a water layer of A h = hi+l-<br />

-ha thick flooded at an ice base of h, thick<br />

Big.2<br />

Temperature Curve for a Period<br />

of Rceezing a Water Layer <strong>on</strong><br />

an Ios Cover.<br />

With a number of assumpti<strong>on</strong> the problem of<br />

flooding and freezing of water layers <strong>on</strong> an<br />

ice mase can be reduced to soluti<strong>on</strong> of the<br />

following two boundary problame:<br />

Here tI - ice temperature; tW - water temperature;<br />

tS - temperature st the surface of the<br />

built-up ice; aI - thermal diffusivity of ice;<br />

aw - thermal diffuaivity of water; L heat of<br />

water-ice transformati<strong>on</strong>; 1, - positi<strong>on</strong><br />

of a aolidificeti<strong>on</strong> fr<strong>on</strong>t.<br />

The above problem has been eolved numerically<br />

using a finite difference method. Thermophysical<br />

properties of water and ice shown in<br />

Table 1 have been ueed for calculati<strong>on</strong>. We have<br />

calculated temperature of an ice mass 1 rn<br />

thick through floodin and freezing by la ere<br />

of 0.01 m (100 la emf, 0.02 m( 50 layeraS,<br />

0.03 m (33 layem, 0.04 m(25 layere), 0.05 m<br />

(20 layere) and during a total tlme period of<br />

cooling the ice maeaif being 25, 50 and 100<br />

boure,<br />

Table 1<br />

Thermophysical Properties of Water<br />

and Ice Used in Calculati<strong>on</strong>s<br />

Propertiea of<br />

Water and ice<br />

Water<br />

Ice<br />

Heat of water-ice<br />

tranaformati<strong>on</strong>, 336000 336000<br />

kJ/m3<br />

Heat capacity per<br />

unit volume,<br />

kY/(m3.K)<br />

4330 2090<br />

Thermal c<strong>on</strong>ductivity,<br />

W/ (m. K) 0.60 2.22<br />

1473<br />

A surface temperature has been taken equal to<br />

-3OOC. The resulta of simulati<strong>on</strong> are tabulated<br />

in Table 11. As men from the table an average<br />

temperature OS the ice maae decreaaes with<br />

an increase in a time period of cooling of<br />

frozen layera and increaaes with an increase<br />

in thicknese of flooded layera. In practical<br />

work <strong>on</strong>e can elwaye eelect such e c<strong>on</strong>diti<strong>on</strong> of<br />

flooding and freezing of water layers thet an<br />

ice mags of a particular thickness and pre-eef<br />

temperature be built-up during the shortest<br />

time possible.<br />

The artificial efrucfure having been built-up,<br />

the etability and length of its existence period<br />

depend <strong>on</strong> upkeeping a perticuler temperature<br />

c<strong>on</strong>diti<strong>on</strong>, The temperature c<strong>on</strong>diti<strong>on</strong> of<br />

the artificial ice-aoil platfomn has been celculated<br />

using a finite element method (FEY).<br />

The method involves a aubetituti<strong>on</strong> of a c<strong>on</strong>tinuous<br />

funoti<strong>on</strong> (in this very caae - temperaturelby<br />

a discrete model that is formed by a<br />

lot of piecewise-o<strong>on</strong>tinuoua functi<strong>on</strong>a defermined<br />

from the finite number of elemente.

Table I1<br />

Simulati<strong>on</strong> Pindings<br />

Total 'Thickneas '<br />

length of layer,<br />

of m OIOl 0.02 0.03 0.04 0.05<br />

- ..<br />

Length of<br />

cooling a<br />

layer,<br />

hour 0.25 0*5 0.75 1.0 1.25<br />

Length of<br />

flooding<br />

and freezing<br />

cycle,<br />

hour 26.5 2908 32.6 35.4 38.1<br />

Length of<br />

cooling<br />

a layer,<br />

hour 0.5 1.0 1.5 2.0 2.5<br />

Average<br />

tempera-<br />

50 ture,<br />

OC -27.1 -18.1 -gd6 -7.7 -4.8<br />

Length of<br />

flooding<br />

and freezing<br />

cycle,<br />

hour 51.0 53.3 55.3 58.0 60.2<br />

provided that<br />

et G boundary<br />

where t - temperature, - time, A (X,Y) - '<br />

tharmal c<strong>on</strong>ductivity, C(X,U)<br />

- heat capacity,<br />

p (X, Y) - deneity, oc ( 5 ) - coefficient of<br />

c<strong>on</strong>vective heat BXOhBng8, q( 'T - heat PLW,<br />

tS( Z ) - aurface temperature, P (x,Y, T 1-<br />

beat aources.<br />

Introducing a' heat c<strong>on</strong>tent (enthalpy) functi<strong>on</strong>t<br />

H(t,X,Y) 7 I (C( 0 ) p + ,$8 (a&*) Id8 (17)<br />

a<br />

where 8 ( fl -t*) - Diraa delta functi<strong>on</strong><br />

t * - phaae transformati<strong>on</strong> temperature.<br />

The heat c<strong>on</strong>tent functi<strong>on</strong> hes a break in going<br />

through a temperature of phase transiti<strong>on</strong>,<br />

t*. Therefore for solving the problem a procedure<br />

of moothing the heat c<strong>on</strong>tent functi<strong>on</strong><br />

about a certain critical temperature is carried<br />

out prooeeding from the requirements of eristenca<br />

and c<strong>on</strong>tinuity of the firat and sec<strong>on</strong>d<br />

temperature derivatives of the heat c<strong>on</strong>tent<br />

functi<strong>on</strong>s.<br />

The amoothing ppocedure having been employed,<br />

eqn. (15) takes the form:<br />

oo<br />

Average<br />

temperature,<br />

OC -28.5 -23.0 -14.8 -12.5 -7.9<br />

Length of<br />

flooding<br />

and freezing<br />

cycle<br />

hour 100.0 100.8 101.8 103.2 104.8<br />

The procedure of minimizing the functi<strong>on</strong>al<br />

related to differential equati<strong>on</strong> (18) and<br />

boundary c<strong>on</strong>diti<strong>on</strong>s (16) results inthe following<br />

matrix equati<strong>on</strong> (Zenkevich, 1975):<br />

where [K], IC], {F} are to be composed of<br />

element metrixee of the ahape:<br />

(19)<br />

Nodal values of temperature are ao eelected<br />

that the beat approximati<strong>on</strong> to ita true aistributi<strong>on</strong><br />

be ensured whiah i s achieved by<br />

minimizing the functi<strong>on</strong>al xelated to the heat<br />

c<strong>on</strong>ducti<strong>on</strong> differential equati<strong>on</strong>. The procem<br />

of minimizing i s reduoed to solving a eyyetem<br />

of linear algebraic equati<strong>on</strong>s relative to the<br />

nodal values.<br />

A temperature profile of the artificial ice-<br />

@oil atrUCtUr8 is described by the heat c<strong>on</strong>ducti<strong>on</strong><br />

n<strong>on</strong>-equilibrium equati<strong>on</strong><br />

where Nil Nj I* ahape fwxoti<strong>on</strong>a.<br />

Time aampling of matrix equati<strong>on</strong> (19) has been<br />

achieved by Krunk-Nicole<strong>on</strong> circuif.<br />

Computer-sided calculati<strong>on</strong>a of the temperature<br />

c<strong>on</strong>diti<strong>on</strong> of the artificial ice-soil platform<br />

has been made. Boundary c<strong>on</strong>diti<strong>on</strong>e have bean<br />

specified aa follows (Fig. 3). Near the upper<br />

boundary the heat Losaes towards the atmosphere<br />

(boundary c<strong>on</strong>diti<strong>on</strong> of the third order) has<br />

been specified. In the lower part of the plat-<br />

1474

Pig.3<br />

Dissecti<strong>on</strong> of the Regi<strong>on</strong> in<br />

Queati<strong>on</strong> into ITnite Elements<br />

end Representati<strong>on</strong> of Boundary<br />

C<strong>on</strong>diti<strong>on</strong>e,<br />

form two boundary o<strong>on</strong>diti<strong>on</strong>s have been aped.-<br />

fied, namely, the heat loeeee fowarda water<br />

' (bounday e<strong>on</strong>difi<strong>on</strong> of the third order) - at<br />

the o<strong>on</strong>tact of the platform and marine water<br />

and the .geothermal heat flux (boundary c<strong>on</strong>diti<strong>on</strong><br />

of the sec<strong>on</strong>d order) - at the cantaot<br />

of the atructure and the BBR bottom, Pig. 4<br />

ahows the results of numerical eirnulati<strong>on</strong> of<br />

the heat c<strong>on</strong>diti<strong>on</strong> of the ice-eoil platform<br />

through initial dietxibuti<strong>on</strong> of ,the temperature<br />

obtained by the data of field investigati<strong>on</strong>s<br />

(Latalin, Gagarin, 1984). Resulte of numerical<br />

simulati<strong>on</strong> enable to select euoh a temperature<br />

c<strong>on</strong>diti<strong>on</strong> of the ice-eoil etructuse that its<br />

heat efability during the moat uniavourable<br />

period6 of operati<strong>on</strong> be enaured.<br />

I<br />

FUDERGNCFS<br />

Zenkevich 0. (1975). Meetod k<strong>on</strong>echnykh elementov<br />

v tekhnike. Momow.<br />

LataLin, D.A., Gagarin, V.E. (1984). hzhenerno-glyataiologiaheakie<br />

aspekty sozdanfya<br />

iekuaetvennykh ledyanykh platform v<br />

Arotike. Kn. "Inz~enernocgeocrrologiehee..<br />

kie issledovaniya'l, 48-52, Yakutsk.<br />

Lafalin D.A. (1986). Ob optimizstsii porsloinogo<br />

narnorazhivaniys lida. Materialy<br />

glyateiologicheskikh iasledovenfj. Khr<strong>on</strong>ika,<br />

obsuzhdeniye, B 55, 222-225,Moaoow.<br />

Saveliev, B.A. Latalin D.A., Gagaxin V.E. et<br />

al. (19821. Sozdanie Xedyanykh platform<br />

na erktieheekom ahelife . Materia4<br />

glyateiologicheekikh iealedovenij. Khr<strong>on</strong>ike,<br />

obauzhdeniya, N 45, 166-168,Moacow,<br />

Saveliev LA., Gagarin V.E., Zykov Yu.D. et 81.'<br />

(1983). Fiziko-khimioheekie aapekty BOBdsniya<br />

ilkusatvennykh ledyanykh sooxuzhenii<br />

is morskoi vody. Kn. Paoblemy gem<br />

kriologii, 113-1 18, MOBCOW',<br />

Savellev B.A., Latalin D.11. (1986). Tskusetvennye<br />

ledyanye platformy. "OkeanoLogiyall,<br />

t.7, 191 p., Modoecow<br />

Cox G.F.W. (1979). fwtiiioial ice ieland for<br />

exploratory drilling. 5-th kt. C<strong>on</strong>P.<br />

Port and Ocean Eng. Arctic C<strong>on</strong>diti<strong>on</strong>s,<br />

vel , p.147-162. NOW.<br />

Ekelund M.I., Mamtere<strong>on</strong> D.M. (1981). Bloating<br />

Ice Platforme for Oil Explorati<strong>on</strong> in the<br />

Arctic Ielende. Arctic, v.33, N 1 , p.168-<br />

1830<br />

Ice Platforma, Subsea Methods Ueed for Arctia<br />

Oasen Well. (1974). World Oil, v. 179,<br />

N 1 , p. 79-82.<br />

I<br />

B<br />

I<br />

Fig.4<br />

Predicti<strong>on</strong> of the Temperature<br />

C<strong>on</strong>diti<strong>on</strong> of an Ice-Soil<br />

Platform,<br />

A.<br />

B, - initial t8mpeXatUX8<br />

positi<strong>on</strong> of ieothexmal linea<br />

in a m<strong>on</strong>th's time<br />

C. - the aame in two m<strong>on</strong>th,% time.<br />

1475

SLOPE STABILITY IN ARCTIC COAL MINES<br />

A.K. Sinha, M. Sengupta and T.C. Kinney<br />

University of Alaska Fairbanks<br />

SYNOPSIS: <strong>Permafrost</strong> soil slopes in arctic mines are susceptible to thaw induced instability.<br />

Such instability may jeopardize the safe working c<strong>on</strong>diti<strong>on</strong>s of an open pit mine. The instability<br />

may also inhibit the safe operati<strong>on</strong> of heavy machinery used in surface mining.<br />

It has been dem<strong>on</strong>strated that covering the slopes with a suitable insulati<strong>on</strong> material reduces or<br />

completely eliminates thawing of the soil slope. An approach for the calculati<strong>on</strong> of the therma,l<br />

c<strong>on</strong>ductivity of the insulati<strong>on</strong> and its thickness is presented.<br />

INTRODUCTION<br />

Traditi<strong>on</strong>al slope stability analysis for a<br />

surface coal mine involves c<strong>on</strong>siderati<strong>on</strong>s of<br />

local 'geology, geotechnical properties of<br />

slope materials, groundwater c<strong>on</strong>diti<strong>on</strong> and<br />

dynamic destabilizing forces that may<br />

influence the slope.<br />

In arctic regi<strong>on</strong>s, however, the geotechnical<br />

engineer is faced with added complexities.<br />

Frozen ground adds another dimensi<strong>on</strong> to slope<br />

stability calculati<strong>on</strong>s. Frozen ground,<br />

c<strong>on</strong>sisting of natural earth materials may<br />

creep under its own weight as well as under<br />

externally applied loads. Due to surface<br />

disturbances, changing slope geometry, and<br />

thermal regime modificati<strong>on</strong>s, frozen ground<br />

may undergo thermal degradati<strong>on</strong> and a mass<br />

movement may in turn lead to slope failure.<br />

Such movements in frozen soils have been<br />

reported by several investigators '(McRoberts,<br />

1978; Phukan, 1985).<br />

STABILITY OF FROZEN SLOPES<br />

The frozen rock and frozen soil slopes lend<br />

themselves to a limiting equilibrium analysis<br />

in c<strong>on</strong>text of mobilized strength of frozen<br />

ground and of tolerable deformati<strong>on</strong> in terms<br />

of creep behavior just like slopes in<br />

temperate regi<strong>on</strong>s.<br />

The strength characteristics of frozen soils<br />

depend primarily <strong>on</strong> the soil type,<br />

temperature, ice c<strong>on</strong>tent, and strain rate.<br />

Frozen soils exhibit creep behavior eved at<br />

low stress levels at rates dependent up<strong>on</strong> ice<br />

c<strong>on</strong>tent, temperature, and applied load.<br />

Generally, the creep behavior of ice-rich<br />

frozen soils is dominated by sec<strong>on</strong>dary creep<br />

with a short time interval for the primary<br />

creep. Ice-poor frozen soils may exhibit <strong>on</strong>ly<br />

pr imary creep.<br />

STABILITY OF THAWING SLOPES<br />

An infinite slope analysis approach may bC<br />

applied to thawing slopes because the failure<br />

plane is approximately parallel to the surface<br />

of the slope. This approach is applicable to<br />

shallow instability problems, such as<br />

solifLucti<strong>on</strong> and bimodal flows. The factor of<br />

safety of such a slope has been discussed by<br />

Phukan (1985).<br />

Thaw-C<strong>on</strong>solidati<strong>on</strong> is a process where excess<br />

pore pressures are developed in soils up<strong>on</strong><br />

thawing and subsequent c<strong>on</strong>solidati<strong>on</strong>. It can<br />

lead to slope instability and ground<br />

settlements. Soliflucti<strong>on</strong> and skin flow in<br />

permafrost slopes can be explained by the<br />

theory of thaw c<strong>on</strong>solidati<strong>on</strong>. The soluti<strong>on</strong> to<br />

some of the related prpblems has been<br />

presented by different researchers (McRoberts,<br />

1978; Pufahl and Morgenstern, 1979).<br />

PIT SLOPE STABILITY<br />

For the stability analysis presented in this<br />

paper the open pit mining operati<strong>on</strong> <strong>on</strong> the<br />

North Slope of Alaska in the area lying<br />

between Cape Lisburn, Point Lay, and Umiat,<br />

al<strong>on</strong>g the Colvile River, was selected (Paul,<br />

1986). Three design alternatives were chosen<br />

using a finite element program as it allows:<br />

(a). two-dimensi<strong>on</strong>al heat transfer modelling.<br />

(b). simulati<strong>on</strong> of multi'layered systems,<br />

including rocks and insulati<strong>on</strong> materials.<br />

(c). surface energy balance calculati<strong>on</strong>s.<br />

The strength of rocks change with temperature.<br />

Weathering may be induced due to exposure to<br />

repeated freeze-thaw cycles, but often. rock<br />

slope stability can be investigated without<br />

detailed analysis of thawing if the rock has<br />

low porosity and low water c<strong>on</strong>tent. However,<br />

rocks with high porosity and permeability may<br />

exhibit thermal characteristics similar to<br />

coarse grained soils and can be modelled<br />

accordingly.<br />

1476

Since, the rock in the area of c<strong>on</strong>cern is<br />

sandst<strong>on</strong>e with high porosity, the slope model<br />

chosen for analysis c<strong>on</strong>sists of either fine<br />

grained or coarse grained soil. The<br />

classificati<strong>on</strong> of soil as fine and coarse, in<br />

this paper, is based <strong>on</strong> Kersten's thermal<br />

c<strong>on</strong>ductivity vs. water c<strong>on</strong>tent charts<br />

Lunardini, 1981). The dry density of both<br />

fine and coa segrained soil was assumed to be<br />

1281.49 Km/m f (80 lb./cft). Average published<br />

meteorolgical data for the envir<strong>on</strong>ment of the<br />

area lying northeast of Cape Beaufort was used<br />

in the heat transfer calculati<strong>on</strong>.<br />

The criteria for choosing an insulati<strong>on</strong><br />

material are the thermal properties, the<br />

moisture absorpti<strong>on</strong>, and compressive strength,<br />

and the modulus of elasticity. Field and<br />

laboratory results indicate that extruded<br />

polystyrene (board type) has a combinati<strong>on</strong> of<br />

properties (viz. low thermal c<strong>on</strong>ductivity, low<br />

water absorpti<strong>on</strong>, and good performance in<br />

thaw/freeze cycles) that has made it more<br />

acceptable than other types of insulati<strong>on</strong>s in<br />

road embankment applicati<strong>on</strong>s in Alaska (Ols<strong>on</strong>,<br />

1984). Expanded polystyrene has been<br />

successfully used as fill material as well as<br />

an insulating layer in Norway (Frydenlund,<br />

1985).<br />

Most of the insulati<strong>on</strong> materials used for road<br />

embankments and slopes are either the formed<br />

in place type (e.g. urethane rigid Foam) or<br />

the board type (e.g. extruded polystrene<br />

boards).<br />

Loose insulati<strong>on</strong> materials such as cork,<br />

gravel, wood chips, etc. would limit the slope<br />

angle to their angle of repose, if spread out<br />

loosely <strong>on</strong> steep slopes, they may be c<strong>on</strong>tained<br />

in "geotextile bags", which in turn may be<br />

placed and anchored <strong>on</strong> the slope face. This<br />

process of using natural insulati<strong>on</strong> material<br />

may, however, prove to be cost1 ier than using<br />

synthetic insulati<strong>on</strong> materials.<br />

On steep slopes, insulati<strong>on</strong> boards may be<br />

"sandwiched'* between layers of geosynthetics<br />

to form insulati<strong>on</strong> blankets which can be<br />

rolled down the steep slopes and anchored by<br />

gravel pad at the top and the bottom. A few<br />

l<strong>on</strong>g rock bolts may be required to firmly<br />

anchor the blankets to the slope face to avoid<br />

damage and swinging in high winds.<br />

Geosynthetics and laboratory results have<br />

shown that polyster geotextiles provided<br />

better performance under cold temperatures as<br />

compared to polypropylene type (Bell, et al.,<br />

1983).<br />

RESULTS FROM THE GEODYNE MODEL<br />

A two dimensi<strong>on</strong>al finite element model called<br />

GEODYNE was used to compute the thaw<br />

boundaries for both bare slopes and insulated<br />

slopes.<br />

Bare Soil Slope<br />

The slope, as shown in Figure 1, was<br />

c<strong>on</strong>sideredtobea fine or coarse grained soil<br />

slope and the thaw depth penetrati<strong>on</strong> into the<br />

soil slope was calculated using GEODYNE. The<br />

slope is subjected to insulated boundaries <strong>on</strong><br />

all sides, except for the slope faces exposed<br />

to air. This limitati<strong>on</strong> of insulating<br />

boundary c<strong>on</strong>diti<strong>on</strong>, assumed by the program<br />

unless a heat flux i s menti<strong>on</strong>ed for boundary<br />

c<strong>on</strong>diti<strong>on</strong>s, i s circumvented by choosing large<br />

slope dimensi<strong>on</strong>s.<br />

Figure 2 illustrates the maximum thaw depth<br />

penetrati<strong>on</strong> at three different locati<strong>on</strong>s of<br />

the slope. A l l depths of thaw penetrati<strong>on</strong> are<br />

the maximum thaw depth for the summer seas<strong>on</strong><br />

€or the respective locati<strong>on</strong>.<br />

The thaw depth in coarse grained soil is<br />

higher than that in the fine grained soil.<br />

This phenomena is due to the higher thermal<br />

c<strong>on</strong>ductivity of quartz, and other similar<br />

minerals, that dominate in a coarse grained<br />

soil, also, moisture c<strong>on</strong>tent is higher in fine<br />

grained soils. As can be observed, the depth<br />

of thaw fr<strong>on</strong>t penetrati<strong>on</strong> increases as the<br />

moisture c<strong>on</strong>tent of the soil reduces.<br />

Thus, the depth of penetrati<strong>on</strong> io the soil<br />

slope is from 0.61 m (2 ft.) to less than 1.2<br />

m (4 ft.) , the thaw depth being the highest<br />

al<strong>on</strong>g the sloping surface., depending <strong>on</strong> the<br />

soil type and the water c<strong>on</strong>teht.<br />

Insulated Slopes<br />

The slope is assumed to be covered with<br />

certain thickness of insulati<strong>on</strong> material, and<br />

the bench top and bottom are covered with a<br />

gravel pad to safeguard the insulati<strong>on</strong> layer,<br />

(Figure 1). A 0.61 m (2 ft.) thick gravel<br />

layer was found satisfactory after c<strong>on</strong>sidering<br />

the compressive strength of commercially<br />

available synthetic insulati<strong>on</strong>s and the<br />

potential. compressive stress caused by a<br />

walking dragline of 25.23 m3 (33 cu.yd.1<br />

bucket capacity.<br />

The thermal c<strong>on</strong>ductivity of the insulati<strong>on</strong>s<br />

increases with the increase of water<br />

absorpti<strong>on</strong> by the insulati<strong>on</strong>. In order to<br />

test the effectiveness of the insulati<strong>on</strong><br />

the area. of c<strong>on</strong>cern, a 0.076 m (3 inch) thick<br />

Polyurethane synthetic insulati<strong>on</strong> was assumed<br />

to cover the slope surface. The properties of<br />

Polyurethane are tabulated in Appendix (1).<br />

The insulati<strong>on</strong> layer water c<strong>on</strong>tent has been<br />

raised from 0% to 400% and the thaw<br />

penetrati<strong>on</strong> calculated using GEODYNE. The<br />

results are shown in the Figure 3.<br />

Figure 3 shows that a 0.076 m (3 inch) layer<br />

of insulati<strong>on</strong> is sufficient to limit the thaw<br />

fr<strong>on</strong>t from penetrating the soil slope even<br />

under extreme water absorpti<strong>on</strong> by the<br />

insulating layer. Al<strong>on</strong>g the sloping surface,<br />

the maximum depth of thaw is 0.074 m (0.24<br />

ft.) (at 400% water c<strong>on</strong>tent). As the<br />

insulati<strong>on</strong> thickness is 0.076 m (0.29 ft.),<br />

the thaw fr<strong>on</strong>t does not enter the soil.<br />

Similarly, at locati<strong>on</strong>s A and C in the slope<br />

in Figure 4 , maximum depth ob thaw (at 400%<br />

water c<strong>on</strong>tent) is about 0.65 m (2.13 ft.)<br />

below bench surface, whereas the combined<br />

thickness of the gravel pad and the insulati<strong>on</strong><br />

is 0.686 m (2.25 feet). Thus, the insulati<strong>on</strong><br />

limits the thaw fr<strong>on</strong>t penetrati<strong>on</strong> in to the<br />

soi 1,<br />

1477

FIGURE: 1<br />

SLOPE MODEL<br />

I, \<br />

4<br />

I I I I I I I<br />

5 10 15 20 25 30 35<br />

I<br />

40 45<br />

X AXIS in meter<br />

I<br />

FIGURE:2<br />

MAXIMUM MAW DEPTH<br />

IN FINE AND COARSE<br />

GRAINED SOIL SLOPE<br />

,... ........, ......... .,.,,,..,......... .

0.8<br />

FIGURE: 3<br />

MAXIMUM THAW DEPTH IN<br />

FINE GRAINED SOIL SLOPE VS.<br />

THERMAL CONDUCTIVITY OF INSULATION<br />

0.7 ........................<br />

I .............................<br />

.G<br />

........................<br />

., ..........<br />

, . A ~oer;no!,c,,..<br />

0.1" .. .: ........... ;... .......;..................................... ! . ..................<br />

~<br />

e-<br />

"- ;""-:----- ++""""<br />

0.0 , 1<br />

I 1<br />

0.02 0.03 0.04 0.05 0.06 0.07 0.01<br />

THERMAL CONDUCTIVITY in W/(m 'C)<br />

FIGURE:4<br />

MAXIMUM THAW DEPTH IN<br />

FINE GRAINED SOIL SLOPE VS.<br />

WATER CONTENT OF INSULATION<br />

0.7 i .............<br />

.........<br />

. .<br />

I<br />

................<br />

3 x 0.4 . FINE GR 30% W I 1<br />

' ' 0.076 m POLYURETHANE INSULAllON . . ' " ,,' WAnONS<br />

0.61 m THICK GRAVEL PAD 30% W<br />

0 ATI - -<br />

0.3 . . . . (Refer Figure 1)<br />

......<br />

W<br />

n<br />

k<br />

e""<br />

.........<br />

["" ""<br />

9<br />

0.0<br />

0<br />

1 I<br />

100 200<br />

300<br />

WATER CONTENT OF INSULATION %<br />

I<br />

400<br />

1479

The thermal c<strong>on</strong>ductivity of the insulati<strong>on</strong><br />

layer forms another major design criteri<strong>on</strong>.<br />

In order to determine a range of thermal<br />

c<strong>on</strong>ductivities suitable for the area of<br />

c<strong>on</strong>cern, insulati<strong>on</strong> (water c<strong>on</strong>tent 0%) with<br />

varying thermal c<strong>on</strong>ductivity was c<strong>on</strong>sidered.<br />

The K value was raised from 0.0288 w/(m°C)<br />

(0.20 Btu/sq.ft.-hr.-'F) to 0.0722 W/(m°C)<br />

(0.50 Btu/sg.ft.-hr-OF). It might be observed<br />

that while a K value range of 0.0288 W/(m°C)<br />

(0.20 Btu/sq.ft.-hr.-OF) is close to extruded<br />

polysterene, a material widely recommended for<br />

road applicati<strong>on</strong>s (Esch, 1978), that a K value<br />

of 0.0722 W/(m°C) (0.50 Btu/sq.ft.-hr.-'F), is<br />

close to that of wood chips.<br />

The maximum thaw ,depth al<strong>on</strong>g the sloping<br />

surface, (Figure 4 locati<strong>on</strong> B) is 0.089 m<br />

(0.29 ft.) below the slope surface at K =<br />

0.0722 W/(m°C) (0.50 Btu/sq.ft.-hr.-OF) , while<br />

the thickness of the insulati<strong>on</strong> layer is 0.076<br />

m (3 inch). The maximum depth of thaw at the<br />

locati<strong>on</strong>s A and B is about 0.65 m (21.5 ft.)<br />

below the bench surface respectively, while<br />

there lies a 0.65 m (2.25 ft.) thick combined<br />

layer of gravel pad and insulati<strong>on</strong>. Hence,<br />

the insulati<strong>on</strong> layer Limits the thaw fr<strong>on</strong>t<br />

penetrati<strong>on</strong> in to the soil, for locati<strong>on</strong>s A<br />

and C, but not B.<br />

CONCLUSIONS<br />

It hqs been successfully dem<strong>on</strong>strated that<br />

insulati<strong>on</strong> cover <strong>on</strong> a slope face reduces the<br />

depth of thaw; the effectiveness of such a<br />

measure shall depend <strong>on</strong> site specific thermal<br />

and climatic c<strong>on</strong>diti<strong>on</strong>s as well as <strong>on</strong> the type<br />

of the insulati<strong>on</strong> material being used.<br />

The model assumes homogeneity of the slope<br />

material as well as homogeneity of insulati<strong>on</strong><br />

covez,bothofwhichare rarelypresent in the<br />

field. However, the model allows simulati<strong>on</strong><br />

of multilayered materials and, thereby, allows<br />

simulati<strong>on</strong> of true ineitu c<strong>on</strong>diti<strong>on</strong>s.<br />

In the case of the finegrained soil slopes in<br />

the general vicinity of the Deadfall Syncline<br />

area of North Slope, Alaska, an insulati<strong>on</strong><br />

cover of 0.076 m (3 inches) with a thermal<br />

c<strong>on</strong>ductivity in the range of 0.0288 to 0.0722<br />

W/(m°C) (0.20-0.50 Btu/sq.ft.-hr.-OF) appears<br />

to be adequate to inhibit the thaw<br />

penetrati<strong>on</strong>, other c<strong>on</strong>diti<strong>on</strong>s being as<br />

specified in the calculati<strong>on</strong>s. A 0.12m(4.5<br />

inch) to 0.15m(6 inch) thick insulati<strong>on</strong> cover<br />

will provide a n<strong>on</strong> thawing slope, a measure<br />

that might be taken for safeguarding thawing<br />

slopes.<br />

It has also been dem<strong>on</strong>strated that water<br />

absorpti<strong>on</strong> by the insulati<strong>on</strong> cover, 0% to 400%<br />

in the simulati<strong>on</strong>s, for the area of c<strong>on</strong>cern,<br />

has an insignificant effect <strong>on</strong> thaw depth,<br />

other c<strong>on</strong>diti<strong>on</strong>s being the same.<br />

REFERENCES<br />

Bell, J.R. et a1 1983. Properties of<br />

Geot4extiles in Cold Regi<strong>on</strong> Applicati<strong>on</strong>.<br />

Proc. <strong>on</strong> Fourth <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g><br />

<strong>on</strong> <strong>Permafrost</strong>, Fairbanks, pp. 123-160.<br />

Berg, R.C. et a1 1978. Thaw Penetrati<strong>on</strong> and<br />

<strong>Permafrost</strong> C<strong>on</strong>diti<strong>on</strong>s associated with<br />

Livengood to Prudhoe Bay Road, Alaska.<br />

Proc. of The Third <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Permafrost</strong>, Edm<strong>on</strong>t<strong>on</strong>,<br />

Canada, pp. 616-621.<br />

Esch, D.C. 1978. Road Embankments Design<br />

Alternatives Over <strong>Permafrost</strong>. Proc. of<br />

Applied Techniques for Cold Envir<strong>on</strong>ments,<br />

Anchorage, pp. 159-170.<br />

Frydenlund, T.E. 1985. Soft Ground Problems.<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> C<strong>on</strong>f. <strong>on</strong> Plastic Foam in<br />

Road Embankments, Oslo, Norway.<br />

Lunardini, V.3. 1981. Heat Transfer in- Cold<br />

Climate. Van Nostrand Reinhold Company,<br />

NJ.<br />

McRoberts, E.C. 1978 LE Geotechnical<br />

Engineering for Cold Regi<strong>on</strong>s. McGraw-<br />

Hill, pp. 363-404.<br />

Ols<strong>on</strong>, M.E. 1984. Synthetic Insulati<strong>on</strong> in<br />

Arctic Roadway Embankments. Proc.: Cold<br />

Regi<strong>on</strong>s Engineering Speciality<br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, pp. 739-751.<br />

Paul, Jyoti Prakash 1986. Fragmentati<strong>on</strong><br />

System Design for an Arctic Surface Coal<br />

Mine. MS. Thesis, University of Alaska,<br />

Fairbanks.<br />

Phukan, A. 1985. Frozen Ground Engineering.<br />

Prent ice-Ha 11<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Series<br />

in Civil Engineering and Eng. Mechanics,<br />

NJ, pp. 200-500.<br />

Pufahl, D.E. and Morgenstern, N.R. 1979.<br />

Stabilizati<strong>on</strong> .of Planar Landslides in<br />

<strong>Permafrost</strong>. Canadian Geotech. J., vo1.8,<br />

558-580.<br />

APPENDIX I<br />

The GEODYNE is a two dimensi<strong>on</strong>al finite<br />

element model for time. dependent analysis of<br />

freeze-thaw problems.<br />

The two-dimensi<strong>on</strong>al form of the differential<br />

equati<strong>on</strong> solved by the model can be written in<br />

Cartesian coordinates:<br />

(1) (2) (3) (4) (5) (6)<br />

UBI% * "Ea (u + Y *)<br />

- (tXw *)<br />

where<br />

T = temperature, OC<br />

- (Xy" +) t Yv$ - 10s -<br />

B1 = the average volumetric heat<br />

capacity of the<br />

soil<br />

mass (kJ/m3); this term is<br />

temperature dependent<br />

a2 = the volumet ic heat capacity of<br />

water (kY/m 5<br />

)<br />

u,v = the comp<strong>on</strong>ents of Darcian water<br />

velocity in<br />

the x<br />

an y directi<strong>on</strong>s, respectively<br />

(m/hr)<br />

0<br />

1480

thermal c<strong>on</strong>ductivity<br />

coefficients in the x<br />

and y directi<strong>on</strong>s, respectively<br />

(kJ/hr m OC); these terms are<br />

temperature dependent<br />

the soil thickness normal to<br />

the x-y plane ( m)<br />

a thermal source or sink<br />

representing the ef ects of<br />

latent heat (kJ/hr m 5<br />

); this<br />

term is temperature dependent<br />

a thermal source or sink term<br />

representing a thermal flux<br />

such.as a surface heat flux or<br />

the flux resulting from the<br />

geothermal gradient (kJ/m)<br />

Equati<strong>on</strong> (1) represents a generalized,<br />

n<strong>on</strong>linear statement of the equati<strong>on</strong> describing<br />

the flow of in heat a saturatedor unsaturated<br />

soil. In reviewing the equati<strong>on</strong>, several<br />

comments c<strong>on</strong>cerning the assumpti<strong>on</strong>s made for<br />

each term are appropriate. First, in term (1)<br />

of Equati<strong>on</strong> (l), the assumpti<strong>on</strong> is made that<br />

the heterogeneous soil-water matrix can be<br />

represented by a homogeneous approximati<strong>on</strong><br />

using-a single volumetric heat capacity,<br />

In general, 81 will be temperature dependent,<br />

and different values will be used if the local<br />

temperature is above or below the freezing<br />

temperature. In other words, p1 is described<br />

in a stepwise Eashi<strong>on</strong>, with the step occurring<br />

at the phase transformati<strong>on</strong> temperature.<br />

Term (2) of Equati<strong>on</strong> (1) represents the<br />

thermal effects of flowing water in the soil<br />

matrix, and is usually called the c<strong>on</strong>vecti<strong>on</strong><br />

term. This term is derived directly from<br />

thermodynamic c<strong>on</strong>siderati<strong>on</strong>s and can have a<br />

profound effect <strong>on</strong> the behavior of a thermal<br />

regime. At the present time, it is assumed<br />

that all values of c<strong>on</strong>vective velocity are<br />

specified external to the model. If the<br />

temperature falls below freezing, the local<br />

water velocities are assumed to go to zero at<br />

that point. Terms (3) and (4) represent the<br />

diffusive transfer of heat according to the<br />

Fourier's analogy. As with the soil<br />

properties, the diffusi<strong>on</strong> coefficients are<br />

assumed to be stepwise temperature-dependent<br />

at the freeze fr<strong>on</strong>t. It is the analyst's<br />

resp<strong>on</strong>sibility to specify the correct<br />

properties for the soil mass above and below<br />

the freeze point. Also, while not a general<br />

situati<strong>on</strong>, it is easily seen that Equati<strong>on</strong> (1)<br />

is formulated to simulate anisotropic<br />

diffusi<strong>on</strong> properties in the x and y<br />

directi<strong>on</strong>s. This may be of particular<br />

interest in axisymmetric problems. The fifth<br />

term oE Equati<strong>on</strong> (1) represents the effects of<br />

latent heat. Proper formulati<strong>on</strong> of this term<br />

is essential to the soluti<strong>on</strong><br />

of the<br />

freeze/thaw problem, and a large number of<br />

alternative formulati<strong>on</strong>s have been tested. At<br />

the present time, this term is formulated as:<br />

where<br />

u1<br />

x (2)<br />

0%- 7 (ml - mo,)<br />

= the net effective heat source/sink<br />

term to represent the effects f the<br />

latent heat of fusi<strong>on</strong> (kJ/hr m s )<br />

1481<br />

At<br />

ml<br />

mB<br />

A= the latent heat of fusi<strong>on</strong><br />

soil matrix (kJ/m 3 )<br />

for the<br />

= some finite time interval between<br />

times to and tl (hr)<br />

= the unfrozen moisture c<strong>on</strong>tent of the<br />

soil matrix at the end of the time<br />

interval At (fracti<strong>on</strong> of total<br />

available unfrozen moisture for<br />

phase transformati<strong>on</strong>)<br />

= the unfrozen moisture c<strong>on</strong>tent of the<br />

soil matrix at the beginning of the<br />

time interval t (fracti<strong>on</strong> of total<br />

available unfrozen moisture for<br />

phase transformat i<strong>on</strong>)<br />

Finally, it is assumed that the unfrozen<br />

moisture c<strong>on</strong>tent of a soil, m can be<br />

approximated as a functi<strong>on</strong> of the soil<br />

temperature. This relati<strong>on</strong>ship has the form:<br />

where<br />

m - 1.0 for T'Tf<br />

T = the local temperature (OC)<br />

Tf = the freezing temperature (OC)<br />

The last term of Equati<strong>on</strong> (3) represents the<br />

effects of heat fluxes. Such fluxes may<br />

either be specified by the analysis (i.e., the<br />

geothermal flux), or may result from a<br />

calculati<strong>on</strong> of a surface heat balance. When<br />

d<strong>on</strong>e as a surface heat balance, the net<br />

surface energy balance flux term is<br />

approximated by the relati<strong>on</strong>ship:<br />

QNET = Qsw -t QNLW + QTURB - QEVAP (4)<br />

where<br />

Qsw =<br />

QNLw =<br />

QToRB =<br />

QEVAP =<br />

transmitted shortwave radiati<strong>on</strong><br />

flux<br />

transmitted net l<strong>on</strong>gwave<br />

radiati<strong>on</strong> flux<br />

turbulent heat transmitted<br />

across the surface<br />

evaporative heat flux leaving<br />

the boundary surface<br />

In general, the terms of Equati<strong>on</strong> (4) are both<br />

surface temperature dependent and functi<strong>on</strong>s of<br />

<strong>on</strong>e or more atmosphere variables.

THE RESISTANCE TO FROST HEAVE OF VARIOUS CONCRETE CANAL LINING<br />

S<strong>on</strong>g, Baoqing, Fan, Xiuting and Sun, Kehan<br />

Qinghai Provincial Institute of Water C<strong>on</strong>servancy, Xining, China<br />

SYNOPSIS Different types of canal lining were c<strong>on</strong>structed in an observati<strong>on</strong> stati<strong>on</strong> in an<br />

area subjected to seas<strong>on</strong>al frost. Linings included c<strong>on</strong>crete plates with a trapezoidal secti<strong>on</strong>, n<br />

shaped plates with a trapezoidal secti<strong>on</strong>, c<strong>on</strong>crete plates set <strong>on</strong> beams with a trapezoidal secti<strong>on</strong>,<br />

overhead c<strong>on</strong>crete plates with an arc bottom, an arch bar secti<strong>on</strong>, and a parabola shaped plate. The,'<br />

study included observati<strong>on</strong>s <strong>on</strong> the distributi<strong>on</strong> of frost heave; frost depth and water c<strong>on</strong>tent al<strong>on</strong>g<br />

canal secti<strong>on</strong>s; maximum heave displacement and residual. frost heave; and the development of cracks.<br />

The results show that the complex c<strong>on</strong>crete plates with an arc bottom was the best resistant to frost<br />

heave and the type of lining is suggested for use in regi<strong>on</strong>s subject to seas<strong>on</strong>al frost by the authors.<br />

TEST PURPOSE, PROCEDURE AND METHODOLOGY<br />

Introducti<strong>on</strong><br />

Up- to now, many engineers and scientists c<strong>on</strong>trol<br />

frost damage of rigid canal linings by limiting<br />

the allowable displacement of the structure.<br />

However,what kind of rigid lining is most suitable<br />

to minimizefrost heaving This is what we<br />

want to discuss in this paper,<br />

Based <strong>on</strong> frost heave distributi<strong>on</strong> al<strong>on</strong>g a secci<strong>on</strong><br />

of canal with various lining, we suggested<br />

some structures with flexible joints am<strong>on</strong>g each<br />

lining block in order to fit in with differential<br />

frost heave, and provided allowable maximum<br />

frost heave for different type of lining. After<br />

analysing the effect of anti-seepage, engineering<br />

cost and c<strong>on</strong>structi<strong>on</strong>, the authors selected<br />

readily available rigid canal lining following<br />

observati<strong>on</strong>s in test secti<strong>on</strong>s.<br />

canal lining were selectyd for test, each with<br />

an area of 5.1 tp 5.25 m and a depth of 1.5 m.<br />

The types of lining included:<br />

(1) A c<strong>on</strong>crete plate with trapezoidal secti<strong>on</strong>.<br />

The plate had a width at the bottom af 2 m, a<br />

slope of L:l, a depth of 1.5 m and a width at<br />

the top of 5.0 m. The plate was c<strong>on</strong>structed of<br />

cast-in-place c<strong>on</strong>crete, with a thickness of 8<br />

cm, and transverse c<strong>on</strong>structi<strong>on</strong> joints at intervals<br />

of 3 m.<br />

(2) A I7 shaped plate with a trapezoidal secti<strong>on</strong>.<br />

similar to that described above. The plate at<br />

the bottom of canal wae cast-in-place c<strong>on</strong>crete<br />

with a joint at the centre for accommodating<br />

frost heave. The slope was lined by precast<br />

shaped c<strong>on</strong>crete plates, with a length of 2.42 m,<br />

a width d'f 0.6 rn and a thickness of 7 cm.<br />

Field test secti<strong>on</strong><br />

(i) Observati<strong>on</strong> of test secti<strong>on</strong>s The field<br />

test setup had three main comp<strong>on</strong>ents:<br />

A, Frost heave pool TQe pool had a depth of<br />

3 m and an area of 600 m . It was lined <strong>on</strong> the<br />

inside surface with double plastic film. Water<br />

supply was runing through an arrangement of subsurface<br />

pipes surrounded by gravel (see Fig.1).<br />

The pool was filled with iight loam with a dry<br />

density of about 1.52 t/m .<br />

B, Water supply system The main pipe has a<br />

diameter of 4.2 cm and is c<strong>on</strong>nected to the<br />

branch pipes of the pool and is c<strong>on</strong>trolled by a<br />

valve. The pipes were full of water to supply<br />

water for the test. During freezing of the<br />

soil in winter, water was supplied from the<br />

supply system to the frost heave pool in order<br />

to keep the ground water level 40 to 60 cm<br />

higher than the pool bottom, that is 95 to 110<br />

cm beneath the bottom of the canal linings.<br />

C. Lining types Seven different types of<br />

unli: cm<br />

Fig.1 The Scheme<br />

of Frost Heave Pool<br />

1482<br />

I

(3) A c<strong>on</strong>crete plate set <strong>on</strong> beams with a trapezoidal<br />

secti<strong>on</strong> similar to that described in (1)<br />

above. A small beam with a secti<strong>on</strong> of 0.1xO.15<br />

m was placed at intervals of 1 m. The c<strong>on</strong>crete<br />

plate was cast-in-place above the beams in order<br />

to strengthen its rigidity.<br />

(4) An overhead c<strong>on</strong>crete plate, similar to that<br />

described in (1) above, supported <strong>on</strong> c<strong>on</strong>crete<br />

beams. The precast beams were placed fir.st,<br />

then the precast c<strong>on</strong>crete plate were placed <strong>on</strong><br />

the beams.<br />

(5) A complex c<strong>on</strong>crete plate with an arc bottom.<br />

The secti<strong>on</strong> was designed with a slope of 1:1, a<br />

depth of 1.5 m, a top width of 5.0 m, an arc<br />

radius of 2.5 m and a chord height of 0.5 m.<br />

The arc bottom was,cast-in-place with a thickness<br />

of 8 cm and with a joint at its centre for<br />

accommodating frost heave, The side slopes were<br />

cast-in-situ or precast c<strong>on</strong>crete plate with a<br />

n shape. A joint between the slope and the<br />

bottom was provided for accommodaing heave. An<br />

expansi<strong>on</strong> joint was provided at intervals of 3<br />

m.<br />

(6) An arch bar with a radius of 2.7 m, a top<br />

width of 5.0 m and with a joint at the centre<br />

for accommodating heave. The bar was cast-inplace<br />

with a thickness of 8 cm. Expansi<strong>on</strong><br />

joints were placed al<strong>on</strong>g the canal at intervals<br />

of 3 m.<br />

(7) A pa:abola shaped plate with a functi<strong>on</strong> of<br />

Y=0.24 X , a depth of 1.5 m. a top width of 5.0<br />

m and a thickness of 8.0 cm. A joint was c<strong>on</strong>structed<br />

in the centre and expansi<strong>on</strong> joints<br />

were provided at intervals of 3 m.<br />

All seven types o f test secti<strong>on</strong>s c<strong>on</strong>tained 8<br />

parts (see Fig.2) were subjected to the same<br />

c<strong>on</strong>diti<strong>on</strong>s, including canal gradient, climatic<br />

c<strong>on</strong>diti<strong>on</strong>s, type of subsoil, and water supply.<br />

(ii) Field observati<strong>on</strong>s Field observati<strong>on</strong>s<br />

including m<strong>on</strong>itoring air temperatures, frost<br />

depths, water c<strong>on</strong>tent of subsoils, frost heave<br />

of lining, development of crack <strong>on</strong> the surface<br />

of the lining and residual displacements. The<br />

layout of the moisture locati<strong>on</strong>s is shown <strong>on</strong><br />

Fig.3.<br />

RESULTS AND ANALYSE<br />

Observati<strong>on</strong> res.ults<br />

The minimum temperature was -16'C, and the maximum<br />

frost depth was 124 cm. Frost heave of<br />

the lining and frost depth were observed 29<br />

times. The development of cracks <strong>on</strong> lining was<br />

described as they occurred. Pertinent observati<strong>on</strong>s<br />

are summaried in Table I and <strong>on</strong> Fig.4.<br />

The soil water c<strong>on</strong>tent 8s a functi<strong>on</strong> of depth<br />

was determined before freezing, at the moment<br />

of maximum frost depth and after thawing. These<br />

test results are summaried in Table 11.<br />

Analyse of results<br />

(i), As indicated in Table 11, the moisture distributi<strong>on</strong><br />

of subsoil al<strong>on</strong>g the secti<strong>on</strong> of canal<br />

was almost the same whatever in the c<strong>on</strong>diti<strong>on</strong><br />

before freezing, frozen or after thawing. Water<br />

c<strong>on</strong>tent increased from the top to the bottom of<br />

the canal. In additi<strong>on</strong>s, the soil moisture c<strong>on</strong><br />

tent in north facing slopes was found to be<br />

higher than that in south facing slopes. , '<br />

Fig.2<br />

The Scheme of Different Types oC Canal Structures<br />

1-1 Precast trapezoidal c<strong>on</strong>crete plate<br />

11-11 precast n shaped c<strong>on</strong>crete plate<br />

a-IU precast overhead c<strong>on</strong>crete plate up<strong>on</strong> beams<br />

IV-IV cast-in-place c<strong>on</strong>crete plate<br />

1483<br />

V-V complex c<strong>on</strong>crete plate with an arch bottom<br />

VI-VI complex cast-in-place c<strong>on</strong>crete plate with<br />

an arch bottom<br />

VII-VII cast-in-place arch structure<br />

Vm-VlI cast-in-place parabola structure

TABLE I<br />

Frost Heave of Lining with Different Structures<br />

Lining Frost heave of lining (cm) Max.disp- Di€f.coef.of heave<br />

tY<br />

Pe<br />

Development of crack<br />

1 2 3 4 5 6 7 8 9 1 0 (cm) 1 2 3 - 4<br />

(1)- CH 0 0 0 0.5 2.3 1.5 1.1 0.8 .0.3 2.3 0 1.9 0.41 A crack occurred at<br />

the centre of canal<br />

Max.C 0.7 0.7 1.02.8 4.5 4.0 4.8 3.1 1.4 4.8 0.17 1.8 1.9 bottom with a width<br />

of 0.5 to 1.8 mm<br />

(2) CH 0.1 0.8 0.8 2.3 4.6 4.7 3.3 2.6 2.1 0.7 4.7 0.41 2.7 1.6 1.1 A crack occurred at<br />

the canal bottom in-<br />

Max.C 0.7 1.2 2.2 4.9 4.9 7.9 4.5 4.0 3.1 1.0 7.9 0.87 0 4.0 1.2 tersectinn - the centreline<br />

of canal atan<br />

angle of 63"<br />

, Significant frost '<br />

(3) CH<br />

heave occurred at the<br />

Max.C 0.1 1.8 2.9 8.9 8.4 3.4 4.2 3.2 3.6 0.9 8.9 1.6 0.59 0.94 1.6 canal bottom<br />

- " . . . .<br />

(4) ' CH<br />

Significant frost<br />

heave occurred at<br />

Max.C 0.6 1.8 2.4 4.2 5.16.0 2.9 4.3 3.1 6.3 1.0 1.1 3.6 0.7 the canal tottom<br />

(5) CH 0.6 0.3 1.1 2.9 4.5 6.0 4.8 2.9 2.2 2.7 6.0 .0.79 1.2 0.9 0.7 A the crack south occurred On facing<br />

Max.C 0.6 0.3 1.1 2.9 4.5 6.0 4.8 2.9 2.2 2.7 6.0 0.79 1.2 0.9 0.7 slope!parallel to<br />

t'h'e dxecti<strong>on</strong> of<br />

canal<br />

(6) CH 0.3 0.2 2.8 4.1 4.4 3.2 1.20.3 4.4 1.3 1.5 A crack occurred <strong>on</strong><br />

the south facing " sl<strong>on</strong>e. * .<br />

bx.C 0.8 0.8 2.2 5.7 6.1 4.7 0.8 2.0<br />

6.1 1.8 1.9<br />

parallel to the directi<strong>on</strong><br />

of canal<br />

(7) CH 0.1 0.1 3.0 4.1 2.3 1.9 1.2 1.0 4.1 1.4 0.36<br />

Max.C 0.3 0.4 5.1 6.3 5.1 3.5 2.2 0.6 6.3 2.2 1.6<br />

* CH-while crack happens; +* Max.C-While maximum crack occurea.<br />

A crack occurred <strong>on</strong><br />

the south facing<br />

slope, parallel to<br />

the directi<strong>on</strong> of canal<br />

Fig.3 Layout of Moisture Locati<strong>on</strong>s<br />

+ Frost depth measurements<br />

Frost heave displacements<br />

+ Water c<strong>on</strong>tent measurements

TABLE I1<br />

Soil Moisture of Subsoil Under Canal<br />

Lining Average moisture (W) Lining Average moisture (X) Lining Average moisture ( X ) .<br />

No,<br />

No.<br />

No.<br />

tY Pe BF Max.F AT type<br />

BF Max.F AT type<br />

BF Max.F AT<br />

1 11.6 15.2 16.1 1 17.5 19.6 17.0 1 10.2 11.5 15.8<br />

2 15.7 19.0 23.0 2 '18.7 25.2 22.3 2 15.4 19.2 22.0<br />

3 24.0 22.3 21.5 3 21.1 27.3 23.9 3 16.3 22.5 20.5<br />

(1) 4 21.8 25.8 21.5 (2) 4 20.8 28.7 25.6 (5) 4 15.5 28.9 23.1<br />

5 19.6 26.9 22.2 5 19.6 24.7 25.0 5 12.4 21.3 23.2<br />

6 16.1 17.5 20.8 6 14.5 20.6 23.5 6 11.8 16.2 22.5<br />

7 11.8 12.5 17.2 7 11.2 13.7 15.4 7 11.2 11.4 15.5<br />

*BF-Before freezing; **Max.F-At the moment of max. frost depth; ***AT-After thawing.<br />

ahmppcd with trapezoidal plate with Irapezoidal complex plate with<br />

secti<strong>on</strong> accli<strong>on</strong> bottom arc<br />

Fig.4<br />

Distributi<strong>on</strong> of Frost Depth al<strong>on</strong>g Canal Secti<strong>on</strong><br />

1 - 1<br />

Fig.5 The Distributi<strong>on</strong><br />

of Frost Heave al<strong>on</strong>g Canal Secti<strong>on</strong><br />

The difference in soil water c<strong>on</strong>tent before and<br />

after freezing between n shaped plates and<br />

plates with a trapezoidal secti<strong>on</strong> is negligible.<br />

However, the water c<strong>on</strong>tent under overhead plate<br />

was less about 3% than that above types.<br />

The water c<strong>on</strong>tent of subsoil before freezing in<br />

the complex plate secti<strong>on</strong> with an arc bottom is<br />

less than that in the trapezoidalsecti<strong>on</strong>. But<br />

after freezing, the soil water c<strong>on</strong>tent under<br />

the bottom was almost the same as that in the<br />

trapezoital <strong>on</strong>e.<br />

(ii) From Fig.4, we know that the distributi<strong>on</strong><br />

of frost depth al<strong>on</strong>g the canal secti<strong>on</strong>s is a<br />

maximum at the top. The frost depth below the<br />

north facing slope is greater than that below<br />

the south facing slope. The minimum frost depth<br />

€or the trapezoidal secti<strong>on</strong> was at the toe of<br />

the south facing slope. The minimum frost depth<br />

of arc secti<strong>on</strong>s was at the middle of the south<br />

facing slope.<br />

(EL) As indicated <strong>on</strong> Table I, the distributi<strong>on</strong><br />

if frost heave of lining al<strong>on</strong>g the secti<strong>on</strong>s is<br />

similar to the distributi<strong>on</strong> of changes of soil<br />

water c<strong>on</strong>tent. That is to say the frost heave<br />

at the top was the smallest and increased to a<br />

maximum at the bottom of the canal.<br />

Based <strong>on</strong> observati<strong>on</strong> results, we know that the<br />

directi<strong>on</strong> of frost heave at the bottom was normal<br />

to the surface of the lining. However, the<br />

directi<strong>on</strong> of the heave <strong>on</strong> canal sideslopes could<br />

be divided two parts, <strong>on</strong>e being normal to the<br />

surface of slope and the other being vertical.<br />

The distributi<strong>on</strong> of normal heave to the surface<br />

of lining for the secti<strong>on</strong> of 1 shaped plate with<br />

trapezoidal secti<strong>on</strong> and €or the complex plate<br />

with arc bottom secti<strong>on</strong> is shown in Fig.5.<br />

From Fig.5 we see that the distributi<strong>on</strong> of frost<br />

1485

heave in trapezoidal secti<strong>on</strong>s was like a "roof"<br />

at the bottom and like a trapezoid at the top.<br />

The distributi<strong>on</strong> of heave al<strong>on</strong>g the complex<br />

plate with an arc bottom has the shape of a<br />

crescent Mo<strong>on</strong>. Comparing the two types of frost<br />

heave distributi<strong>on</strong> in Fig.5, it is obvious that<br />

the complex plate with an arc bottom is much<br />

more effecting to frost heave. The experimental<br />

results show that the maximum frost heave ohtained<br />

from the curve secti<strong>on</strong>s (including the<br />

complex plate secti<strong>on</strong> with arc bottom, the arch<br />

bar secti<strong>on</strong> and the parabola secti<strong>on</strong>) is much<br />

less than that for the trapezoidal secti<strong>on</strong>s.<br />

As an example, the maximum heave of the complex<br />

plate secti<strong>on</strong> with arc bottom was 3.5 cm, when<br />

the maximum heave in the n shaped plate with a<br />

trapezoidal secti<strong>on</strong> .was 7.9 cm. The reas<strong>on</strong> for<br />

this improved performance might be that under<br />

the acti<strong>on</strong> of frost heaving forces the arc bottom<br />

of the lining acts as an arch to resist upwards<br />

forces.<br />

(iv) Frost depth and heave of the north facing<br />

slopes were found to be much larger than that<br />

in the south facing slopes, However, cracks in<br />

the lining usually occurred in the south facing<br />

slope first. The formati<strong>on</strong> of cracks depends<br />

<strong>on</strong> not <strong>on</strong>ly the heave. The rate of crack development<br />

during subsoil freezing is much slower<br />

than that during thawing. Placing a joint in<br />

the cehtre of the canal bottom can improve reduce<br />

the number of cracks.<br />

(v) From Table I we know that the resistance to<br />

Erost heave of curve secti<strong>on</strong> is much better<br />

than that in trapezoidal secti<strong>on</strong>, and the best<br />

lining type in our test field is the complex<br />

plate with arc bottom, the next is arch bar.<br />

The third best is the parabola secti<strong>on</strong>, the 4th<br />

is the n shaped plate with trapezoidal secti<strong>on</strong>,<br />

the 5th is the overhead plate with a trapezoidal<br />

secti<strong>on</strong>, the 6th is the plate set <strong>on</strong> beams with<br />

a trapezoidal secti<strong>on</strong>. The poorest resistance<br />

to heave was the c<strong>on</strong>crete plate with a trapezoidal<br />

secti<strong>on</strong>. The maximum allowable frost<br />

heave of different types of lining structure is<br />

summaried in Table 111. '<br />

Under the acti<strong>on</strong> of frost heave forces, the<br />

part of arc bottom in the complex plate lining<br />

was in compressi<strong>on</strong> z<strong>on</strong>e, the joints.in the centre<br />

of the canal bottom and between the slope plate<br />

and the arc bottom accommodating frost heave<br />

movements. Therefore, the structure of a complex<br />

plate with arc bottom performs extreme well<br />

against frost heave forces. The maximum allowable<br />

frost heave of a plate structure with a<br />

trapezoidal secti<strong>on</strong> is around 2 cm. The cracks<br />

j.n the plate structure therefore occurred under<br />

very small displacements.<br />

The directi<strong>on</strong> of frost heave at the top of canal<br />

slopes is not <strong>on</strong>ly normal to the slope but also<br />

vertical to the ground surface because of two<br />

dimensi<strong>on</strong>al freezing. The directi<strong>on</strong> of frost<br />

heave at toe of the slope was normal to the<br />

slope and the frost heave amount at that point<br />

was much larger than that at the top of the<br />

slope, As a result frost heave forces suhjectcd<br />

the slope plate to both tensi<strong>on</strong> and bending<br />

movements. Therefore, the cracking and frost<br />

damage <strong>on</strong> the slope of canals with trapezoidal<br />

secti<strong>on</strong>s .usually occures at a depth which is<br />

1/3 to 1/2 of canal height from the bottom. The<br />

c<strong>on</strong>structi<strong>on</strong> of the arch bar secti<strong>on</strong> can prevent<br />

such damage.<br />

(vi) After thawing of the subsoil, the displacement<br />

of c<strong>on</strong>crete lining was partially recovered.<br />

The maximum residual displacement produced by<br />

frost heave are listed in Table IV: the maximum<br />

residual displacement occurred at the corner<br />

between the slope and the bottom of canal, for<br />

trapezoidal secti<strong>on</strong>s, or at the centre of the<br />

bottom of the canal for curve secti<strong>on</strong>s. Displacement<br />

recovery was greater for curve secti<strong>on</strong>:<br />

is compared to trapezoidal secti<strong>on</strong>s.<br />

(vii) After analysing the results presented in<br />

Tables I and I1 and Fig.4, a relati<strong>on</strong> between<br />

mean frost heave ratio and moisture c<strong>on</strong>tent of<br />

the subsoil below the complex plate canal with<br />

an arc bottom was established as follows:<br />

P = 0.56 (W - 10.4)<br />

where, P-the mean frost heave ratio, %;<br />

W-the moisture c<strong>on</strong>tent of the subsoil<br />

before freezing.<br />

(viii) A review of the test data dem<strong>on</strong>strates<br />

that the structure of complex c<strong>on</strong>crete plate<br />

with arc bottom performs the best with a str<strong>on</strong>g<br />

resistance to frost heave and a good ability for<br />

recovering displacement. In order to provid a<br />

comparis<strong>on</strong> from a cost and c<strong>on</strong>structi<strong>on</strong> point<br />

of view, we have set up a test canal with a n<br />

shaped lining of trapezoidal secti<strong>on</strong> (with a<br />

length of 2.6 km) and a test canal with complex<br />

plate lining with arc bottom (with a length of<br />

Lining Max.AFH Diff.coef. Lining Max.AFH Diff.coef.<br />

type (cm) of FH(xl0) type (cm) of FH(xl0)<br />

-<br />

1486

TABLE IV<br />

Joj.nts are important to reduce frost<br />

heeve damage to the lining.<br />

Residual Displacement of Frost Heave with<br />

Different Lining Types<br />

Lining Residual Lining Residual<br />

type displacement<br />

(cm)<br />

type displacement<br />

(cm)<br />

(1) 3.6 (5) 1.6<br />

(2) 2.0 (6) 1.5<br />

(4) 3.2 (7) 2.5<br />

(3) 3.2 .<br />

1.4 km) in Daxia canal, Lodu county: a test canal<br />

with complex plate lining with arc bottom (with<br />

a length of 0.34 km) and U shaped secti<strong>on</strong> in<br />

Nanmenxia canal, Huzu county. Observati<strong>on</strong>s <strong>on</strong><br />

these test secti<strong>on</strong>s provide the following c<strong>on</strong>clusi<strong>on</strong>s:<br />

A. Compared with trapezoidal and U shapped secti<strong>on</strong>s,<br />

the secti<strong>on</strong> of complex plate with an arc t<br />

bottom is rather close to the ec<strong>on</strong>omical <strong>on</strong>e.<br />

Its perimeter is rather short, as an example,<br />

the perimeter is about 3% shorter than that of<br />

the trapezoidal secti<strong>on</strong> in Daxia test cana1,and<br />

is about 5% shorter than that of U shaped<br />

secti<strong>on</strong> in Nanmenxia test canal.<br />

B. The formwork for cast-in-place c<strong>on</strong>crete for<br />

the complex plate with arc bottom is more simple<br />

and ec<strong>on</strong>omic than that of U shaped secti<strong>on</strong><br />

and precast fl shaped secti<strong>on</strong>.<br />

C. Observati<strong>on</strong> results in Daxia show that the<br />

cost of precast shaped Lining is more expensive<br />

than a complex plate with a cast-in-place arc<br />

bottom.<br />

D. Frost heave observati<strong>on</strong>s over a period of<br />

two years show that cracks occurred in more than<br />

20 percent of the areas where lining c<strong>on</strong>sisted<br />

of n shaped secti<strong>on</strong>s cracks occurred in <strong>on</strong>ly<br />

0.4 percent of the areas where lining c<strong>on</strong>sisted<br />

of complex plate with an arc bottom. In c<strong>on</strong>clusi<strong>on</strong>,<br />

the complex plate with an arc bottom<br />

lining appears to cost the least and perform<br />

the best.<br />

CONCLUSIONS<br />

(i) The observati<strong>on</strong> results show that the<br />

experimental .test set up was suitable<br />

for testing the characteristics of different<br />

type of canal linings.<br />

(ii) Observati<strong>on</strong>s of maximum allowable frost<br />

heave and residual displacement of different<br />

types of linings are useful for<br />

design and c<strong>on</strong>structi<strong>on</strong>.<br />

(iii) The test results showed that a lining<br />

c<strong>on</strong>sisting of a complex c<strong>on</strong>crete plate<br />

with an arc bottom is host resistant to<br />

frost heave and most ec<strong>on</strong>omical.<br />

(iv) .C<strong>on</strong>structi<strong>on</strong> joints should be used according<br />

to the distributi<strong>on</strong> of potentail<br />

frost heave al<strong>on</strong>g canal secti<strong>on</strong>s,<br />

1487

SYNOPSIS: The*Northern Eskimo community of Barrow, Alaska, USA began c<strong>on</strong>structi<strong>on</strong> of the village<br />

wide underground BaKrOW Utilities System in 1981. In 1985 they decided to complete the unfinished<br />

porti<strong>on</strong>s of the utilities system using direct bury arctic pipes instead of the underground<br />

Utilidor used in previous phases of the project. This paper describes this Direct Bury Utilities'<br />

System and discusses the unique features of the design. Design details, some advantages and a few<br />

problems associated with the design and c<strong>on</strong>structi<strong>on</strong> of the project are presented.<br />

INTRODUCTION<br />

In 1981 the North Slope Borough began the<br />

design and c<strong>on</strong>structi<strong>on</strong> of their aggressive<br />

underground utilities system to serve the 3000<br />

residents in the Village of Barrow, Alaska,<br />

USA. This system was made financially possible<br />

by the development of the North Slope oil<br />

fields and the high price of oil during the<br />

late 1970,s and early 1980,s. The utilities<br />

system, comm<strong>on</strong>ly known as the Barrow Utilities<br />

System, represented a complete public works<br />

project whose main purpose was to provide a<br />

village wide underground utilidor c<strong>on</strong>taining<br />

water and sewer lines, cable TV, teleph<strong>on</strong>e, and<br />

future electrical service. In additi<strong>on</strong> to the<br />

Utilidor c<strong>on</strong>structi<strong>on</strong>, water pumping. stati<strong>on</strong>s,<br />

sewage pump stati<strong>on</strong>s, a sewage lago<strong>on</strong>, shop and<br />

warehouse facilities, and a village wide fire<br />

protecti<strong>on</strong> system were built. Roads were<br />

c<strong>on</strong>structed or rehabilitated, a material site<br />

was developed and a l<strong>on</strong>g term solid waste<br />

disposal site was investigated. The entire<br />

project provided stable employment €or the<br />

local villagers and in many cases training in<br />

some craft or skill.<br />

In 1985 the North Slope Borough recognized that<br />

the entire project had grown in scope and could<br />

not be completed with the remaining m<strong>on</strong>ies set<br />

aside for the project. Wanting to h<strong>on</strong>or their<br />

commitment to provide potable water and sewer<br />

service and fire protecti<strong>on</strong> throughout the village,<br />

the North Slope Borough decided to change<br />

the design from the well known "Barrow<br />

Utilidor" to a more cost effective Direct Bury<br />

System.<br />

Frank Moolin and Associates, Inc. headquartered<br />

in Anchorage, Alaska, USA was c<strong>on</strong>tracted to<br />

perform the new Direct Bury System design since<br />

they had been the designers and project<br />

managers for the Utilidor System. It was felt<br />

they could complete the redesign quickly due to<br />

their intimate knowledge of the Utilidor System<br />

which was important since the North Slope<br />

Borough did not want to interrupt the established<br />

c<strong>on</strong>strycti<strong>on</strong> schedule for the entire<br />

project .<br />

In June of 1985 work began <strong>on</strong> the redesign<br />

effort which would provide direct bury water<br />

and sewer service and fire protecti<strong>on</strong> to the<br />

areas not serviced by the utilidor. The author<br />

held the positi<strong>on</strong> of Senior Project Engineer<br />

for this project and was resp<strong>on</strong>sible for all<br />

porti<strong>on</strong>s of the technical design. Stanley<br />

Industrial C<strong>on</strong>sultants, Limited of Edm<strong>on</strong>t<strong>on</strong>,<br />

Alberta, Canada was c<strong>on</strong>tracted by the North<br />

Slope Borough to perform the design review and<br />

to provide technical assistance based <strong>on</strong> their<br />

c<strong>on</strong>siderable experience with utilities systems<br />

in the arctic,. The resulting design successfully<br />

incorporated significant cost savings<br />

features, provided an easy to maintain system<br />

and was designed and c<strong>on</strong>structed within the<br />

schedule c<strong>on</strong>straints.<br />

DESIGN PHTLOSOPHY AND CRITERIA<br />

prefabricati<strong>on</strong><br />

The North Slope Borough desired a high quality<br />

system which would provide water, sewer and<br />

fire protecti<strong>on</strong> to the unserviced porti<strong>on</strong>s of<br />

the village with the remaining Capital<br />

Improvement Funds. To achieve this goal it wae<br />

decided that most of the system should be prefabricated<br />

in a shop envir<strong>on</strong>ment with skilled<br />

labor. These prefabricated comp<strong>on</strong>ents would<br />

then be shipped to Barrow and assembled into<br />

the final operating system. The North Slope<br />

Borough indicated a desired to use <strong>on</strong>-site<br />

materials left over from the Utilidor project<br />

<strong>on</strong>ly if it was ec<strong>on</strong>omically desirable. Some<br />

insulated piping and pipe fittings were<br />

utilized from these <strong>on</strong>-site materials.<br />

Comm<strong>on</strong> Trench<br />

The excavati<strong>on</strong> and backfilling of the permafrost<br />

during the Utilidor installati<strong>on</strong> proved<br />

to be <strong>on</strong>e of the major expenses associated with<br />

the Utilidor c<strong>on</strong>structi<strong>on</strong>. It was felt that a<br />

ncomm<strong>on</strong> trench" design for the Direct Bury<br />

System should be used to reduce the excavati<strong>on</strong><br />

and backfilling costs. This comm<strong>on</strong> trench

approach did not meet the State of Alaska<br />

standards for utility system installati<strong>on</strong> and a<br />

variance allowing both the water and sewer<br />

lines to be placed in a comm<strong>on</strong> trench was<br />

needed.<br />

Unlike the utilidor where the water lines were<br />

installed in pairs (<strong>on</strong>e supply and <strong>on</strong>e return<br />

line) , the Direct Bury system's water lines<br />

would be c<strong>on</strong>figured in loops so that <strong>on</strong>ly <strong>on</strong>e<br />

water line would be routed al<strong>on</strong>g any <strong>on</strong>e<br />

street. The water would be made to circulate<br />

to prevent freezing during periods of low flow.<br />

Since the Utilidor waa already operati<strong>on</strong>al in<br />

porti<strong>on</strong>s of the village, it would be used as<br />

the backb<strong>on</strong>e of the Direct Bury System. All<br />

Direct Bury water loops would begin and end in<br />

the UtiLidor.<br />

EULuQY<br />

The North Slope Borough Fire Department<br />

required the Direct Bury System to provide a<br />

fire flow of 75 liters per sec<strong>on</strong>d at all fire<br />

hydrants which established the system's peak<br />

flow rates. Stanley Industrial C<strong>on</strong>sultants,<br />

Ltd. recommended that the system incorporate<br />

flow reversal in the water mains so the water<br />

could feed each fire hydrant from two<br />

directi<strong>on</strong>s as it does in the system they<br />

designed for DaWsOn City, Yuk<strong>on</strong>; Canada. Flow<br />

reversal would allow for smaller diameter mainlines<br />

and associated cost reducti<strong>on</strong>s.<br />

ElaJntainabilitv<br />

The existing Utilidor System provided the<br />

ultimate in access and ease of maintenance for<br />

a utility system in the arctic. The North<br />

slope Borough desired to maintain this feature<br />

in the birect Bury design. To satisfy this<br />

requirement all walving, fire hydrants, sewer<br />

clean-outs, heat trace. panels, etc. were<br />

located inside surface accessible manholes.<br />

SYSTEM COMPONENTS<br />

The major comp<strong>on</strong>ents of the Barrow Utilities<br />

System were c<strong>on</strong>structed between 1981 and 1985.<br />

These comp<strong>on</strong>ents included the Water<br />

Recirculati<strong>on</strong> Plant, four sewage pump stati<strong>on</strong>s,<br />

the sewage lago<strong>on</strong> and approximately five kilometers<br />

of utilidor. Only the extensi<strong>on</strong> of the<br />

mainline pipes from the Utilidor to the<br />

unserviced porti<strong>on</strong>s of the village was required<br />

in the design of tHe Direct Bury system. The<br />

major comp<strong>on</strong>ents of the Direct Bury System<br />

include :<br />

1. The tie-in c<strong>on</strong>necti<strong>on</strong>s to the existing<br />

Utilidor water lines and gravity sewer lines.<br />

2. The prefabricated manholes, which c<strong>on</strong>tain<br />

water valving; vents, drains, fire hydrants,<br />

sewer clean-outs, and heat trace panels.<br />

3. The comm<strong>on</strong> trench, which includes insulated<br />

high density polyethylene piping, heat tracing,<br />

trench insulati<strong>on</strong> and the backfill material.<br />

4. The service c<strong>on</strong>necti<strong>on</strong>s, which included the<br />

mainline stub-out, the service c<strong>on</strong>necti<strong>on</strong><br />

piping and the belowground to aboveground<br />

c<strong>on</strong>necti<strong>on</strong>.box.<br />

Details of these system comp<strong>on</strong>ents are<br />

discussed below. Included in the discusei<strong>on</strong><br />

are comments regarding the design, the fabricati<strong>on</strong><br />

and the installati<strong>on</strong> of the comp<strong>on</strong>ents..<br />

Utilidor to Direct B um<br />

Catiom<br />

Two methods of providing circulati<strong>on</strong> in the<br />

Direct ~ury system water loops were investigated,<br />

pumping and utilizing differential<br />

pressure at the Direct Bury water loop tie-in<br />

points. The use of circulating pumps was not<br />

selected because of their cost of installati<strong>on</strong><br />

and operati<strong>on</strong>, the need for maintenance and the<br />

c<strong>on</strong>sequences of a broken pump resulting in the<br />

freezing of the water main. An in-depth<br />

hydraulic analysis indicated that circulati<strong>on</strong><br />

in all the direct bury loops could be easily<br />

provided by creating a 70 kPa pressure differsntial<br />

between the Utilidor's water supply and<br />

return lines.<br />

Individual Direct Bury water loops were<br />

c<strong>on</strong>nected to the Utilidor water supply line<br />

using an isolati<strong>on</strong> valve. The return end of<br />

each Direct Bury water loop was c<strong>on</strong>neeted to<br />

the Utilidor's water return line with a check<br />

valve and circulati<strong>on</strong> by-pass piping as shown<br />

in Figure 1. The circulati<strong>on</strong> by-pass piping<br />

c<strong>on</strong>tains a flow balancing valve, a visual flow<br />

indicator and temperature and pressure<br />

indicators. By adjusting the flow balancing<br />

valve the desired flow velocity of 6 centimeters<br />

per sec<strong>on</strong>d in the mainlines could be<br />

obtained. The in-line check valve provides the<br />

capability -to reverse flow in tho Direct Bury<br />

water line in the event of fire flow. When any<br />

hydrant is opened <strong>on</strong> a Direct Bury loop the<br />

pressure in the loop will be less than the<br />

Utilidor's water return Line pressure and the<br />

check valve will open providing a reversal of<br />

flow in the line to the hydrant.<br />

MAINLINE<br />

CHECK VALVE<br />

7<br />

BX~UILB a - rmw ~ R B PIPIMG ~ L<br />

.ATION<br />

Maintenance is easy to perform <strong>on</strong> the flow<br />

c<strong>on</strong>trol piping because it is located in the<br />

Utilidor where it can be inspected during the<br />

daily walk-through. Being inclosed in the warm<br />

Utilidor envir<strong>on</strong>ment, the piping is not subject<br />

tQ freezing. There are no moving parts in the<br />

system except for the visual flow indicator<br />

1489

-<br />

which allows the maintenance people to quickly<br />

verify that there is positive flow in each<br />

direct bury water loop.<br />

ALCESS HATCH<br />

K<br />

1'90<br />

7<br />

The installati<strong>on</strong> of the potable water and<br />

sanitary sewer piping in the same manhole is<br />

generally termed by the designer as the "comm<strong>on</strong><br />

manhole" design. The comm<strong>on</strong> manhole design<br />

offers two major advantages over separate water<br />

and sewer manholes. First, the total number of<br />

manholes required when using comm<strong>on</strong> manholes is<br />

approximately <strong>on</strong>e half of the number requireU<br />

if separate manholes were used. .This reduces<br />

the c<strong>on</strong>structi<strong>on</strong> cost significantly. Sec<strong>on</strong>d,<br />

the fewer number of manholes also creates less<br />

interference with vehicle and foot traffic<br />

al<strong>on</strong>g the roads. This reduces the chance of<br />

ciamage to the manholes by snow removal equipment,<br />

public and private automobiles and<br />

recreati<strong>on</strong>al vehicles such as snowmachines and<br />

three wheelers.<br />

The design of the direct bury manholes followed<br />

the basic design of the Utilidor's service box,<br />

a 1.9 meter diameter steel cylinder with a base<br />

plate, frost shield and a hatched lid. This<br />

design worked very well for the Utilidor<br />

service c<strong>on</strong>necti<strong>on</strong>s and it was felt the design<br />

would adapt very easily to the Direct Bury<br />

manholes. Each Direct Bury manhole was individually<br />

designed for a specific locati<strong>on</strong>.<br />

Figure 2 shows a typical manhole. The major<br />

comp<strong>on</strong>ents of the manholes are smmiarized<br />

below:<br />

1. The manhole is made of a 1.9 meter diameter<br />

rolled steel shell with a 2.5 .meter diameter<br />

steel base plate, a 0.6 centimeter thick steel<br />

lid, an access hatch, a ladder and an insulated<br />

frost shield located abwe the piping. The<br />

outside of the manholes is insulated with 7.6<br />

centimeters of sprayed <strong>on</strong> urethane foam and<br />

sealed with 0.13 centimeters of waterproof<br />

coating.<br />

2. The potable water piping is located 0.9 to advantages:<br />

1.5 meters above the base plate. Necessary<br />

isolati<strong>on</strong> valves, tees, ells, vents, drains and 1. Higher fabricati<strong>on</strong> standards could be met<br />

other pipe fittings are installed as needed for because the work was performed in a shop<br />

each unique manhole c<strong>on</strong>figurati<strong>on</strong>.<br />

envir<strong>on</strong>ment equipped for this type of work.<br />

3. Soma manholes c<strong>on</strong>tained fire hydrant piping<br />

which includes an in-line tee base, the dry<br />

riser barrel and the hydrant head.<br />

4. Thegravitysewerpipingincludessewer<br />

clean-outs and vents where necessary.<br />

The<br />

sewage piping is completely c<strong>on</strong>tained within a<br />

welded steel sewer enclosure with a gasketed<br />

and bolted lid.<br />

5. The heat trace wiring c<strong>on</strong>nected to a c<strong>on</strong>trol<br />

box.<br />

The use of the steel sewer enclosure was in<br />

resp<strong>on</strong>se to the State of Alaska Department of<br />

Envir<strong>on</strong>mental C<strong>on</strong>servati<strong>on</strong>'s c<strong>on</strong>cern over the<br />

possibility of c<strong>on</strong>taminating the circulating<br />

water system if the sewer were to surcharge and<br />

leak into the manhole, eventually flooding the<br />

potable water piping. Both the water and<br />

gravity sewer piping are c<strong>on</strong>structed of 860 kPa<br />

rated piping for added safety and the sewer<br />

l k r l SPRAY<br />

INSULATION<br />

FFDST<br />

SHIELD<br />

PENETRATION<br />

SLEEVE<br />

BOARD<br />

INSULATION<br />

12.50 "J<br />

FXam 2 - -ow<br />

DETAIL<br />

enclosure provides additi<strong>on</strong>al assurance that<br />

cross c<strong>on</strong>taminati<strong>on</strong> will not occur.<br />

During the c<strong>on</strong>structi<strong>on</strong> of the Utilidor all the<br />

basic materials for the system were shipped to<br />

Barrow and then assembled into their final<br />

c<strong>on</strong>figurati<strong>on</strong>. This was necessary because o'f<br />

the nature of the Utilidor design and the<br />

desire to create jobs and job training in the<br />

village. With the need to reduce the overall<br />

cost of completing the utilities project, 'the<br />

direct bury manholes were totally prefabricated<br />

before being shipped to BaFKOW. Prefabricati<strong>on</strong><br />

of<br />

the manhole assemblies provided several<br />

-<br />

2. Shipping costs would be reduced because the<br />

number of pieces requiring handling, packaging<br />

and tracking was reduced.<br />

3. Reduced installati<strong>on</strong> costs at the<br />

c<strong>on</strong>structi<strong>on</strong> site because all the manhole<br />

piping was pre-installed,<br />

The selecti<strong>on</strong> of the comm<strong>on</strong> manhole design<br />

simplified the use of a comm<strong>on</strong> trench design in<br />

which the water lines and the gravity sewer<br />

lines are installed over the top of each other.<br />

This approach provides c<strong>on</strong>siderable cost<br />

savings in the excavati<strong>on</strong> of the trench and the<br />

installati<strong>on</strong> of the mainline piping.<br />

Unfortunately, it makes the installati<strong>on</strong> of the<br />

service c<strong>on</strong>necti<strong>on</strong> piping more difficult<br />

because the water c<strong>on</strong>necti<strong>on</strong> ia located<br />

directly above the sewer Line c<strong>on</strong>necti<strong>on</strong>. h<br />

typical cross secti<strong>on</strong> of the Direct Bury

Utilities System trench is shown in Figure 3.<br />

The trench width was fixed by the widest trench<br />

the Bortunco Roc-saw could cut with a single<br />

pass of its bar and chain. During the Utilidor<br />

c<strong>on</strong>structi<strong>on</strong> the Roc-saw utilized a 40 centimeter<br />

wide chain to make the Cut6 in the<br />

permafrost. This 40 centimeter wide chain<br />

would produce a trench which was too narrow to<br />

allow proper backfilling of the mainline piping<br />

used in the Direct Bury System. Investigati<strong>on</strong><br />

into the maximum cutting width of the Roc-saw<br />

revealed that a 60 centimeter wide Chain Could<br />

be installed if minor modificati<strong>on</strong>s<br />

to the<br />

cutting bar were performed. A trench width of<br />

60 centimeters provided 11.5 centimetersof<br />

clearance <strong>on</strong> both, sides of an 20 pipe with<br />

insulati<strong>on</strong>. This was enough clearance to allow<br />

the backfill material to fill the Voids under<br />

the haunches of the pipe. Additi<strong>on</strong>ally, the<br />

few loops requiring a 25 centimeter pipe with<br />

insulati<strong>on</strong> could be accommodated.<br />

To facilitate the trench backfilling activities<br />

and to provide a more thermally stable installati<strong>on</strong>,<br />

the n<strong>on</strong>-frost susceptible (NFS) backfill<br />

material was placed in the trench as a<br />

slurry. c<strong>on</strong>siderable effort was put into the<br />

thermal design of the Direct Bury Systems<br />

trench so a minimum burial depth could be<br />

utilized without compromising the integrity of<br />

the direct bury piping. Results of the thermal<br />

model indicated that backfilling with saturated<br />

NFS slurry would reduce the seas<strong>on</strong>al thaw depth<br />

in the trench during the first few years of<br />

operati<strong>on</strong>. The frozen moisture in the slurry<br />

backfill would reduce the overall thaw<br />

penetrati<strong>on</strong> due to the increased latent heat of<br />

fusi<strong>on</strong> in the slurry compared to that of dry<br />

NFS. Based <strong>on</strong> a -12 degree C soil temperature<br />

and a 5 degree C water temperature in the pipe,<br />

freezing times during no flow c<strong>on</strong>diti<strong>on</strong>s were<br />

estimated to be 95 hours to fKaZZle ice<br />

formati<strong>on</strong> in a 15 cm insulated pipe.<br />

Tests performed during the Utilidor c<strong>on</strong>structi<strong>on</strong><br />

established that the dry NFS material was<br />

difficult to compact requiring several passes<br />

with a gasoline powered hand operated<br />

compactor. The uee of a NFS and water slurry<br />

had several c<strong>on</strong>structi<strong>on</strong> advantages over the<br />

placement of dry NFS in that it coula be poured<br />

evenly into the trench from slowly moving mixtrucks,<br />

it would flow around the haunches of<br />

the pipe and it required no significant<br />

compacti<strong>on</strong> effort. Cement vibrators easily<br />

settled the slurry around the pipes and moved<br />

the slurry al<strong>on</strong>g the trench to even out the<br />

thickness of the lift. The problems associated<br />

with buoyancy floating the piping in the wet<br />

slurry were solved by installing wood blocking<br />

across the trench at a selected spacing and<br />

predetermined elevati<strong>on</strong>s and then floating the<br />

pipe <strong>on</strong> top of the slurry until it was held in<br />

the proper positi<strong>on</strong> by the blocking. No<br />

attempts were made to remove the blocking since<br />

it would not effect the thermal stability of<br />

the trench.<br />

The mainline piping in the trench c<strong>on</strong>sisted of<br />

15, 20 and 25 centimeter diameter high density<br />

polyethylene pipes with 7.6 centimeters of<br />

spray applied polyurethane foam insulati<strong>on</strong> and<br />

an extruded polyethylene jacket. This arctic<br />

pipe was identical to that used in porti<strong>on</strong>s of<br />

1491<br />

the Utilidor System where its historical performance<br />

was good. A heat trace channel and<br />

self regulating 20 kcal per meter heat trace<br />

was placed under the insulati<strong>on</strong> for use during<br />

the loss of circulati<strong>on</strong> to prevent freeze-up<br />

and to thaw frozen lines.<br />

Board insulati<strong>on</strong> was placed in most of the<br />

trenches to reduce the thaw penetrati<strong>on</strong> in the<br />

backfill material. When the pipe burial depth<br />

was shallow, insulati<strong>on</strong> was placed across the<br />

width and vertically al<strong>on</strong>g the sides of the<br />

trench to prevent thaw penetrati<strong>on</strong> from both<br />

the sides and the top of the trench. At<br />

intermediate burial depths insulati<strong>on</strong> was <strong>on</strong>ly<br />

placed across the trench width and at the<br />

deepest depths no trench insulati<strong>on</strong> was needed.<br />

Five centimeters of extruded polystyrene board<br />

insulati<strong>on</strong> was used in all cases since significant<br />

quantities were left over from<br />

the<br />

Ut idor il proj ect<br />

.<br />

r EXISTING GROUND SURFACE<br />

-<br />

LOCATOR TAPE<br />

5 ~n THICK INSULATION<br />

9 I BACKFILL<br />

1’<br />

INSULATED WATER MAIN<br />

INSULATED SEWER MAIN<br />

The State of Alaska Regulati<strong>on</strong>s require a<br />

separati<strong>on</strong> of at least 3 meters between the<br />

water and sewer lines. Discussi<strong>on</strong>k with the<br />

Department of Envir<strong>on</strong>mental C<strong>on</strong>servati<strong>on</strong><br />

resulted in the agreement that the comm<strong>on</strong><br />

trench design would have a very low cross c<strong>on</strong>taminati<strong>on</strong><br />

potential because the water and<br />

sewer pipes were made of high density<br />

polyethylene, insulated and covered with<br />

a<br />

seamless extruded jacket and the pipes were<br />

buried in a nearly impermeable saturated<br />

backfill.<br />

Overall, this trench c<strong>on</strong>figurati<strong>on</strong> provides<br />

good thermal integrity coupled with low c<strong>on</strong>-

structi<strong>on</strong> costs. The potential for c<strong>on</strong>tamina-<br />

%i<strong>on</strong> is remote and the ability to survive<br />

mainline freeze-ups is excellent.<br />

HEAT TRACE CHANNEL<br />

7w<br />

Service C<strong>on</strong>necti<strong>on</strong>s<br />

The design of the service c<strong>on</strong>necti<strong>on</strong> trench<br />

followed the approach used for the mainline<br />

comm<strong>on</strong> trench. The method of transiti<strong>on</strong>ing<br />

from belowground to aboveground at the building<br />

is similar to the method. used for the Utilidor<br />

service c<strong>on</strong>necti<strong>on</strong>s. All Direct Bury service<br />

c<strong>on</strong>necti<strong>on</strong>s c<strong>on</strong>sist of a 10 centimeter<br />

insulated gravity sewer Line installed in a<br />

comm<strong>on</strong> trench with a 10 centimeter insulated<br />

carrier pipe c<strong>on</strong>taining a 2.5 centimeter water<br />

supply line and a 2.0 centimeter water return<br />

line. Circulati<strong>on</strong> in the water lines is<br />

developed by a small circulating pump located<br />

in the llc<strong>on</strong>necti<strong>on</strong> box'l, the belowground to<br />

aboveground transiti<strong>on</strong> structure at the'<br />

building.<br />

Circulating the water in the service c<strong>on</strong>necti<strong>on</strong><br />

piping keeps it from freezing, however, heat<br />

tracing is installed inside the carrier<br />

c<strong>on</strong>taining the two water lines for back-up<br />

freeze protecti<strong>on</strong>. The insulated sewer Line<br />

c<strong>on</strong>tains a heat trace channel and self<br />

regulating heat tracing for thawing purposes<br />

<strong>on</strong>ly. Under normal flow c<strong>on</strong>diti<strong>on</strong>s the sewer<br />

should not freeze and the heat trace will be<br />

turned off. The heat trace cables and the circulating<br />

pump the are powered at the building<br />

from a dedicated electric meter since the costs<br />

associated with operating the circulating pump<br />

and the heat trace is built into the cost of<br />

the water. If a customer leaves the village<br />

for an extended period of time and has his<br />

house power turned off, the service c<strong>on</strong>necti<strong>on</strong><br />

will still operate.<br />

During the mainline pipe installati<strong>on</strong> prefabricated<br />

service c<strong>on</strong>necti<strong>on</strong> stub-outs were<br />

installed at the building c<strong>on</strong>necti<strong>on</strong> locati<strong>on</strong>s.<br />

When the time comes to c<strong>on</strong>nect a building to<br />

the mainlines, the service c<strong>on</strong>necti<strong>on</strong> piping is<br />

fused <strong>on</strong> to the pre-installed stub-outs. This<br />

eliminates the need to excavate around the<br />

mainlines which would be difficult in the<br />

frozen soils. The water line stub-out is<br />

fabricated such that the two circulating water<br />

pipes are c<strong>on</strong>nected to the mainline pipe so<br />

they fit inside the 10 centimeter carrier pipe.<br />

This c<strong>on</strong>necti<strong>on</strong> area is insulated, reinforced<br />

and made water tight with urethane foam and a<br />

fiberglass jacket. The sewer line service<br />

c<strong>on</strong>necti<strong>on</strong> branch is c<strong>on</strong>structed in much the<br />

same manor as the water line except that a<br />

single 10 centimeter fusi<strong>on</strong> is made to the<br />

mainline instead of two 2.5 centimeter fusi<strong>on</strong>s.<br />

Figure 4 shows the prefabricated water stubout.<br />

SYSTEM PERFORMANCE<br />

At the writing of this paper Phases I and I1 of<br />

the Direct Bury Utilities System had been<br />

c<strong>on</strong>structed and were operating. Phase 111 is<br />

scheduled to be c<strong>on</strong>structed during the winter<br />

of 1987-1988. The c<strong>on</strong>structi<strong>on</strong> and operati<strong>on</strong><br />

of the first two phases has revealed a few<br />

problems which should be avoided in Phase 111.<br />

Y<br />

cn<br />

0<br />

1 I - MAINLINE WATER PIPE<br />

"<br />

SNE<br />

One significant problem encountered during the<br />

first two phases of c<strong>on</strong>structi<strong>on</strong> was leakage<br />

during the pressure testing in the valve<br />

gaskets, at a few of the mainline pipe fusi<strong>on</strong><br />

joints and in the polyethylene pipe to steel<br />

pipe couplings. Poor installati<strong>on</strong> practice<br />

accounted for the gasket and fusi<strong>on</strong> joint<br />

problems. The leakage in the polyethylene to<br />

steel coupling was attributed to the cold<br />

temperatures causing the polyethylene to ahrink<br />

to a much greater degree than the steel collar<br />

extruded around the polyethyleni. Air escaped<br />

through the fitting which could not be<br />

prevented. Even though it was expected that<br />

these fittings would not leak when functi<strong>on</strong>ing<br />

at normal operating temperatures, the leaking<br />

fittings were replaced.<br />

At the time of the initial system start-up <strong>on</strong>ly<br />

a few building were c<strong>on</strong>nected to the system. A<br />

single service could not generate enough sewage<br />

flow ,to keep the mainline sewers from freezing.<br />

Regular-. flushing of the sewer lines and<br />

operati<strong>on</strong> of the backup heat trace was needed<br />

to prevent freeze-ups during the periods of low<br />

flows. As more buildings were c<strong>on</strong>nected to the<br />

system the problem of the freezing sewers<br />

disappeared.<br />

Maintaining the proper hydraulic balance in the<br />

combined Utilidor and Direct Bury Water loops<br />

normally requires very little acti<strong>on</strong> <strong>on</strong> the<br />

part of the system operators. However, the<br />

loops 3re finely balanced and any change in the<br />

pressures and flow rates in <strong>on</strong>e part of the<br />

system will have an effect in all other parts<br />

of the system. Isolating certain loops of the<br />

network can cause zero flow c<strong>on</strong>diti<strong>on</strong>s in other<br />

loops. For this reas<strong>on</strong> it is important that<br />

the operators understand hydraulic principles<br />

and the relati<strong>on</strong>ships between the loops. Zero<br />

flow c<strong>on</strong>diti<strong>on</strong>s have been encountered due to<br />

selected valving changes in the system.<br />

Fortunately, daily walk-throughs and visual<br />

inspecti<strong>on</strong>s caught these c<strong>on</strong>diti<strong>on</strong>s before a<br />

freeze-up occurred.<br />

Gaining access to the sewer line clean-outs is<br />

difficult. The operators must open the manhole<br />

access hatch, remove the frost shield hatch,<br />

1492

climb under the potable water piping, unbolt<br />

the sewer enclosure lid and then remove the<br />

clean-out cap. The reverse process is<br />

performed when the inspecti<strong>on</strong> is completed.<br />

There is c<strong>on</strong>cern that the maintenance pers<strong>on</strong>nel<br />

will not replace the sewer enclosure lid with<br />

the required gasket and bolts because 00 the<br />

time c<strong>on</strong>suming effort involved. Signs <strong>on</strong> the<br />

sewer enclosure lid pieces indicate the need to<br />

keep the lids bolted in place.<br />

CONCLUSION<br />

The Barrow Direct Bury Utilities System design<br />

o€fers a water and sewer distributi<strong>on</strong> system<br />

which interfaces well with the Utilidor System.<br />

Efforts in the design stage to create a<br />

comp<strong>on</strong>ent type system which allowed for<br />

prefabricati<strong>on</strong> and easy field installati<strong>on</strong>,<br />

were successful. This approach to a utilities<br />

distributi<strong>on</strong> system should be applicable to<br />

most arctic and sub-arctic villages where a<br />

buried system is desired. Utility system<br />

designers should visit the Barrow Utilities<br />

System to see first hand it's desirable<br />

features and to discuss the maintenance aspect@<br />

Of the Bystem With the Direct Bum System<br />

operators. Hopefully, good engineering<br />

practice and quality c<strong>on</strong>structi<strong>on</strong> have provided -<br />

the community of Barrow with many yeara of<br />

reliable water and sewer service.<br />

REFERENCES<br />

Greenwood, W (1982)<br />

Shallow Buried Insulated Water and<br />

Sanitary Sewer Systems in <strong>Permafrost</strong><br />

Regi<strong>on</strong>s.<br />

Martin, R h Sahlfeld, J (1984).<br />

Sewer/Water Service C<strong>on</strong>necti<strong>on</strong>s for Barrow<br />

Utilities System. Proc Cold Regi<strong>on</strong>s Engr,<br />

(1) , 395-400<br />

Shillingt<strong>on</strong>, E & MacKinn<strong>on</strong>j E (1987).<br />

Barrow Utility Syltem, Direct Bury System<br />

- The Alternative. Proc 2nd C<strong>on</strong>f <strong>on</strong> Cold<br />

Regi<strong>on</strong>s Envir Engr<br />

Zirjacks, W h Hwang, C (1983).<br />

Underground Utilidors at Barrow Alaska: A<br />

Two Year history. Proc IV Intl C<strong>on</strong>f <strong>on</strong><br />

<strong>Permafrost</strong><br />

1493

COLD CRACKING OF ASPHALT PAVEMENT ON HIGHWAY<br />

Tim, Deting and Dai, Huimin<br />

Heil<strong>on</strong>gjiang Provincial Institute of Communicati<strong>on</strong>s, Barbin, China<br />

SYNOPSIS Based <strong>on</strong> field investigati<strong>on</strong>s <strong>on</strong> a asphalt-paved highway in Heil<strong>on</strong>gjiang<br />

Province,<br />

Northeast China, features of the cold cracking of the road pavement were described, and its<br />

causes were analyzed as well, After intensively analyzing its influencing factors, measures for .I<br />

preventing the cold cracking were presented from various aspects including selecti<strong>on</strong> of pavement<br />

material, design of road structure and c<strong>on</strong>trol of c<strong>on</strong>structi<strong>on</strong> quality. etc.<br />

INTRODUCTION<br />

Cracking of road pavement caused by low temperature<br />

is a comm<strong>on</strong> phenomen<strong>on</strong> of frost damage in<br />

cold regi<strong>on</strong>s. It severely harms the normal operati<strong>on</strong><br />

of road and leads to a great increase in<br />

the maintenance cost. It was reported that the<br />

length of highway, which had been severely<br />

damaged by cold cracking, accounts for 17% of<br />

the total length of the highway in Japan. In<br />

China, because various kinds of oxide asphalts<br />

have been widely used in the c<strong>on</strong>structi<strong>on</strong> of<br />

road pavement in recent years, cold cracking<br />

of the pavement becomes worse and worae.Therefore,<br />

more attenti<strong>on</strong> has been paid to the study<br />

<strong>on</strong> the cold cracking of road surface. This<br />

paper deals with the field investigati<strong>on</strong> <strong>on</strong> the<br />

cold cracks occurredin the pavement of a sec<strong>on</strong>d<br />

grade highway in Heil<strong>on</strong>gjiang Province and<br />

their cures and preventi<strong>on</strong> countermeasures.<br />

TYPE AND FEATURES OF CRACKS IN PAVEMENT<br />

The cracks in road pavement caused by cold c<strong>on</strong>tracti<strong>on</strong><br />

and frost heave can be classified as<br />

the l<strong>on</strong>gitudinal crack and crosswise crack.<br />

L<strong>on</strong>gitudinal crack<br />

This type of crack is oriented al<strong>on</strong>g the L<strong>on</strong>gitudinal<br />

directi<strong>on</strong> of a highway, i.e.. most<br />

likely parallel to the directi<strong>on</strong> of driving<br />

(Fig.1, photo). Field investigati<strong>on</strong> shows that<br />

most of the l<strong>on</strong>gitudinal cracks are distributed<br />

at the central part of a road, and some at<br />

both sides of the vehicle runways or at the<br />

edges of the road. The l<strong>on</strong>gitudinal cracks<br />

are generally several meters, or several decades<br />

even hundreds of meters 'l<strong>on</strong>g, 1-5 mm<br />

(sometimes, 15-25 mm) wide and 5-40 mm deep.usually<br />

the central cracks are wider and deeper,<br />

while the edgewise cracks are smaller and shallower.<br />

The l<strong>on</strong>gitudinal cracks were caused by the uneven<br />

frost heave of subsoils. The severe cold<br />

cracking shown in Fig.1 occurred in the case<br />

that the.road was under the influence of flood<br />

before freezing. Field tests showed that the<br />

average water c<strong>on</strong>tent of the roadbed within the<br />

depth of 20-80 cm beneath pavement was as high<br />

as 30.1% (for some places even up to 34.8X),<br />

which was higher than its liquid limit. The<br />

groundwater table there was also shallow. This<br />

allows lots of moisture migrating towards frost<br />

fr<strong>on</strong>t and ice segregating during freezing. The<br />

ice segregati<strong>on</strong> leads to a great amount of frost<br />

heave,and thus resu1t.s insevere cracking of the pavement.<br />

Of course, the cracks could also be<br />

caused by the poor quality of the road c<strong>on</strong>structi<strong>on</strong>.<br />

Crosswise crack<br />

This type of cracks were developed across a road.<br />

Some of the cracks may run through the road from<br />

<strong>on</strong>e side to the other (Fig.2) and some may not<br />

(Fig.3). The former is wider, usually with a<br />

width of 3-10 mm (some up to 10-25 mm), and the<br />

latter is narrower but densely distributed, with<br />

a width of 2-4 mm in general.<br />

Field investigati<strong>on</strong> shows that some uf the crosswise<br />

cracks may penetrate from pavement into<br />

1494

higher the brittleness of Lhe material. Therefore,<br />

the cnvir<strong>on</strong>mcnt temperature substantially<br />

affects the cold cracking of the asphalt road<br />

pavement.<br />

From viewpoint of this c<strong>on</strong>siderati<strong>on</strong>, the occurcncc<br />

of the cold cracks can be predicted by<br />

estimating the cracking temperature (i.e., the<br />

cri-tical temperature for initiating cracking),<br />

which can be determined by comparing temperature<br />

stress (i.e., the tensile stress caused by cold<br />

c<strong>on</strong>tracti<strong>on</strong>) in the pavement material with its<br />

tensile resistance.<br />

Fig. A Photo Showi.ng a Crosswise Crack Running<br />

Throuah the Cross-secti<strong>on</strong> of the Hirhwav<br />

Fig,3 A Ptoto Showing Finer Crosswise Cracks<br />

in the Asphalt Pavement<br />

roadbed, while some occur <strong>on</strong>ly in pavement. The<br />

crosswise cracks may be caused by cold c<strong>on</strong>tracti<strong>on</strong><br />

or short of the thickness of pavement and<br />

roadbed or excessive deformatj<strong>on</strong> of the underlying<br />

base soils.<br />

MECHANISM OF THE COLD CRACKING<br />

At present, there are two c<strong>on</strong>si.derati<strong>on</strong>s dealing<br />

with the analysis <strong>on</strong> the mechanism of cold cracking.<br />

They are:<br />

Stress analysis c<strong>on</strong>siderati<strong>on</strong><br />

Because the asphalt pavement was cohered together<br />

with roadbed, the c<strong>on</strong>tracti<strong>on</strong> deformati<strong>on</strong> of the<br />

pavement due to cooling will be c<strong>on</strong>strained by<br />

the cohesi<strong>on</strong> and fricti<strong>on</strong> between the pavement<br />

and roadbed. C<strong>on</strong>sequently, tensile stress will<br />

be produced in the pavement. The tensile stress<br />

will increase with decreasing temperature. As it<br />

excesses the peak tensile strength of the pavement<br />

material, tensi<strong>on</strong> fracture, and thus cracks<br />

will occur.<br />

It is noted that the stress-strain behaviour of<br />

asphalt, the b<strong>on</strong>ding comp<strong>on</strong>ent of the pavement.<br />

mixture, is very sensitive to temperature. The<br />

higher the temperature, the higher the ductility.<br />

By c<strong>on</strong>trast, the lower the temperature, the<br />

Strain analysis c<strong>on</strong>siderati<strong>on</strong><br />

It is c<strong>on</strong>sidered from the strain analysis that<br />

with the decrease in temperature, the failure<br />

strain (i.e., the strain at which crack occurs)<br />

of asphalt mixture decreases, and as the total.<br />

strain of cold c<strong>on</strong>tracti<strong>on</strong> plus the strain caused<br />

by vehicle load of the pavement excesses its<br />

failure strain, cracking will occur. Of course,<br />

when the cold c<strong>on</strong>tracting strain is greater than<br />

failure strain, cracks will alos occur even if<br />

there is no acti<strong>on</strong> of vehicle load. Based <strong>on</strong><br />

this, <strong>on</strong>e could also estimate the cracking temperature<br />

by comparing the cold c<strong>on</strong>tracting<br />

strain with failure strain, and thus predict<br />

the occurence of cracking in pavement.<br />

The cold cracks in asphalt pavement usually<br />

generate first at the surface and then penetrate<br />

downwards. This is due to the fact that the<br />

temperature in the surface is colder, as a<br />

rasult, it produces higher c<strong>on</strong>tracti<strong>on</strong> stress<br />

and strain and makes the pavement material more<br />

brittle. Besides, it is also accounted for the'<br />

ageing and fatigue of the surficial layer of the<br />

pavement. However, it there is a layer of limesoil<br />

mixture directly underneath the asphalt<br />

pavement, which has a higher dry and cold c<strong>on</strong>tractibility,<br />

the cold cracks will initiate at<br />

the lower part of the pavement and penetrate<br />

upwards through the pavement,<br />

INFLUENCING FACTORS OF COLD CRACKING<br />

The main factors influencing the cold cracking<br />

of asphalt pavement include:<br />

Temperature<br />

Generally speaking, the colder the temperature,<br />

or the greater the temperature gradient, the<br />

more severe the cracking would be. Field investigati<strong>on</strong><br />

shows that the cold cracking is extremely<br />

serious particularly under the cyclic acti<strong>on</strong><br />

of freezing and thawing during earlier winter<br />

and spring. As for the cracking temperature, it<br />

is reportedly, defferent (sey, -.lo", -16" or<br />

-18'C) for different countries. According to<br />

the tests c<strong>on</strong>ducted at Harbin District, Northeast<br />

China, it also varies with the type of pavement.<br />

For example, it is about -7.5"C for the finegrained<br />

asphalt-c<strong>on</strong>crete pavement, -11°C for the<br />

medium-grained asphalt-c<strong>on</strong>crete pavement and<br />

higher than -7.5"C for the lime-soil pavement,<br />

'The minimum temperature in Northern China is<br />

lower than the above-menti<strong>on</strong>ed cracking temperatures,<br />

so that the cold cracking is unavoidable<br />

there.

Trafic density<br />

Field investigati<strong>on</strong> shows that more cracks will<br />

occur as trafic density is less than 1000 vehicles/day.<br />

This is accounted for that the asphalt<br />

pavement can not be compacted to have a higher<br />

density under the repeated loading of lower<br />

trafic density.<br />

Behaviour of asphalt and asphalt mixtures<br />

It is easy to crack for: (1') the asphalt with<br />

lover. penetrati<strong>on</strong> index, lower ductility and<br />

higher softening point,(2) the asphalt mixture<br />

with higher c<strong>on</strong>tractibility and greater rigidity<br />

modulus,(3) the asphalt c<strong>on</strong>taining less asphaltine,(&)<br />

the asphalt c<strong>on</strong>crete with higher peeling<br />

ratio and lower void ratio,(5) the asphalt<br />

mixture c<strong>on</strong>taining more asphalt (thus, with<br />

higher c<strong>on</strong>tractibility), and (6) the asphalt<br />

mixture c<strong>on</strong>taining less finer particles (thus,<br />

with higher sensitivity to temperature, higher<br />

permeability and easy to be aged).<br />

Effect of water<br />

The acc,umulati<strong>on</strong> and permeati<strong>on</strong> of surface water<br />

and migrati<strong>on</strong> of capillary water from underlying<br />

groundwater will make the roadbed and subgrade<br />

very moist. When freezing, it produces a great<br />

amount of uneven frost heave, resulting in the<br />

severe cracking of pavement, Besides, when the<br />

asphalt pavement is wetted, the,polar molecules<br />

of water will penetrate through asphalt film to<br />

the surface of mineral aggregates. It will peel<br />

off the surrounding asphalt film and decrease<br />

the b<strong>on</strong>ding force between the cementing asphalt<br />

and aggregates, leading to cracking.<br />

Effect of roadbed and subgrade material<br />

The cold cracking of pavement <strong>on</strong> fine-grained<br />

subgrade is more severe than that <strong>on</strong> coarsegrained<br />

subgrade, because the fine-grained soil<br />

is favourable in water migrati<strong>on</strong> and ice segregati<strong>on</strong>,and<br />

thus causing a great amount of uneven<br />

frost heave (Wu et a1.,1981; T<strong>on</strong>g et a1.,1985).<br />

However,, cracking of the pavement laid <strong>on</strong> coarsegrained<br />

subgrade will aslo occur if the fine particle<br />

(15%).<br />

The type of roadbed material also has a certain<br />

effect <strong>on</strong> cold cracking. Generally, various<br />

kinds of lime-soil mixture,which are of semirigid<br />

material with higher dry and cold c<strong>on</strong>tractibility,<br />

are easy to crack and lead t o reflective<br />

cracks of pavement.<br />

Grain compositi<strong>on</strong> of asphalt mixtures<br />

Investigati<strong>on</strong> shows that the coarse-grained asphalt<br />

c<strong>on</strong>crete has a better behaviour of anticracking<br />

in comparis<strong>on</strong> with the asphalt crushed<br />

st<strong>on</strong>es: more cracks occur in the dense asphalt<br />

c<strong>on</strong>crete with poor grain size distributi<strong>on</strong>; and<br />

the cracking temperature for the medium-grained<br />

asphalt c<strong>on</strong>crete is lower than that for the<br />

fine-grained <strong>on</strong>e.<br />

Effect of freezinR index<br />

It is obvious that the greater the freezing index,<br />

the deeper the frost penetrati<strong>on</strong>,and thus, the<br />

easier the cold cracking would be.The spacing of<br />

crosswise cracks depends up<strong>on</strong> cracking temperature.The<br />

lower the cracking temperature,the wider<br />

the spacing of the crosswise cracks. 'The further<br />

1496<br />

drop of temperature after initiati<strong>on</strong> of cracking<br />

does not affect the spacing, but widens the<br />

cracks.<br />

ANTI-CRACKING INDEX<br />

The capacity of anti-cold cracking of asphalt<br />

pavement is generally characterized by the following<br />

indexes, i.e., rigidity modulus, cold<br />

c<strong>on</strong>tracti<strong>on</strong> coefficient, split resistence and<br />

temperature stress.<br />

The cold c<strong>on</strong>tracti<strong>on</strong> coefficient (a) for different<br />

types of asphalt c<strong>on</strong>crete measured by<br />

T<strong>on</strong>gji University and Heil<strong>on</strong>gjiang Provincial<br />

Institute of Communicati<strong>on</strong>s are shown in Table<br />

1. The values of splitting deformati<strong>on</strong> (d) for<br />

various kinds of asphalt c<strong>on</strong>crete observed by<br />

an institute in Beijing are shown in Table 11. .,<br />

It is seen from Tab1e.a that the value of splitting<br />

deformati<strong>on</strong> for the A-60 type of asphalt<br />

c<strong>on</strong>crete is greater (about 1.58 times) than that<br />

for Vactory-100 asphalt c<strong>on</strong>crete. It is, therefore,<br />

predicted that the colding cracking for<br />

the former is less serious than that for the<br />

latter. This is c<strong>on</strong>sistent with field observati<strong>on</strong>s.<br />

Based <strong>on</strong> test results, the temperature stress<br />

( u) as a functi<strong>on</strong> of temperature for asphalt<br />

c<strong>on</strong>crete was formulated by Heil<strong>on</strong>gjiang Provincia1<br />

Institute of Communicati<strong>on</strong>s and T<strong>on</strong>gji<br />

University, which was written as<br />

u = a - (a +bt) exp(ct) (1)<br />

where u is the temperature stress in MPa, t is<br />

the absolute values of temperature in 'C, and<br />

a, b and c are empirical parameters, having<br />

the values of a = 43.87, b = 0.5856 and<br />

c = 0,01467, respectively,<br />

Eq.(l) can be used to accurately estimate the<br />

temperature stress for asphalt c<strong>on</strong>crete within<br />

the range of temperature from 0' to -3O'C<br />

and <strong>on</strong> the assumpti<strong>on</strong>th,at the l<strong>on</strong>gitudinal<br />

c<strong>on</strong>tracti<strong>on</strong> is completely c<strong>on</strong>strained and the<br />

crosswise c<strong>on</strong>tracti<strong>on</strong> is free ( i.e., <strong>on</strong>edimenti<strong>on</strong>al<br />

stress state).<br />

If the curves of u bs t and ot/K<br />

is the tensile strengthand K<br />

v6 t, where<br />

is the correcti<strong>on</strong><br />

factor takena valueof 2, are plotted<br />

in a diagram (Fig.4), then the cracking<br />

temperature ( to ) can be determined corresp<strong>on</strong>ding<br />

to the intercrossing point A ofthe<br />

curves.<br />

The spacing of crosswise carcks ( L ) of<br />

asphalt-c<strong>on</strong>crete pavement can be estimated by<br />

L = & [a-(a+bt) exp(cto)l (2)<br />

where r is the unit weight of the pavement<br />

material in KN/m', f is the fricti<strong>on</strong> coefficient<br />

at the interface between pavement and the underlying<br />

roadbed, generally taken a value Of 0.2,<br />

and to is the cracking temperature in 'c.

TABLE I<br />

Values of the Cold C<strong>on</strong>tracti<strong>on</strong> Coefficient (a) for Different<br />

Types of Asphalt C<strong>on</strong>crete<br />

Type of asph.Valuesof a ( M5) atthefollowingranges of temp. ("C)<br />

c<strong>on</strong>crete<br />

-25 -25 - -30<br />

0 - -5 -5 - -10 -10 - -15 -15 - -20 -20 +<br />

Medium-grained 2.38 2.22 2.10 1.98 1.79 1.64<br />

fine-grained 2.32 2.18 2.04 2.03 2 .oo 1.95<br />

TABLE I1<br />

Values of Splitting Deformati<strong>on</strong> (d) for the C<strong>on</strong>crete<br />

Mixed with Different Types of Asphalt<br />

Type of Values<br />

asphalt<br />

" . -<br />

of d (mm) at the following temps. ("C)<br />

10 5 -0.5 -6 -10.5 -15 -20.5<br />

A-60 0.65 0.48 0.36 0.32 0.30 0.24 0.18<br />

Vactory-10 0.50 0.34 0.41 0.23 0.19 0.16 0.16<br />

Comparis<strong>on</strong> shows that the values of c calculated CURE AND PREVENTION OF COLD CRACKING<br />

with Eq.(2) are in a good agreement with the<br />

observed values. Investigati<strong>on</strong>s and engineering practi<br />

that co1.d cracking can be effectively prevented<br />

by the proper choice of pavement material and<br />

I 1<br />

grain compositi<strong>on</strong> of mineral aggregates and the<br />

reas<strong>on</strong>able design of road profile.<br />

Temperaturel. 'C<br />

Choice of pavement material<br />

The behaviour of asphalt significantly affects<br />

the physical and mechanical properties of the<br />

asphalt mixtures, so that it is important to<br />

choose proper kinds of asphalt to c<strong>on</strong>struct road<br />

pavement for the preventi<strong>on</strong> of cold cracking.<br />

Am<strong>on</strong>g the various types of existing asphalts<br />

used in road c<strong>on</strong>structi<strong>on</strong>, the A-60, Vactory-100<br />

and Jinxi-60 types of asphalt have a better<br />

behaviour of anti-cold cracking. It is, therefore,<br />

recommended to use the above-menti<strong>on</strong>ed<br />

three types of asphalt in the c<strong>on</strong>structi<strong>on</strong> of<br />

road pavement. Investigati<strong>on</strong> shows that the<br />

behaviour of anti-cold cracking of asphalt can<br />

be greatly improved by mixing various kinds of<br />

asphalts, such as oil asphalt, natural asphalt<br />

and coal asphalt, together in a proper mixing<br />

ratio to make up a mixed asphalt or adding a<br />

certain amount of rubber, sulphur or asbestos<br />

Fig.4 Determinati<strong>on</strong> of the Cracking Temperature<br />

fabric to the asphalt. For example, the results<br />

from the tests c<strong>on</strong>ducted at Dagang, Tianjin<br />

(Lo) for the Medium-grained Asphalt C<strong>on</strong>crete: showed that the ductility of the asphalt with<br />

1- U vs.t, 2- ot/K vs.t.<br />

the additive of rubber is about twenty times as<br />

great as that without rubber.<br />

1497

Besides, mineral aggregates of the asphalt mixture<br />

also affect the anti-cracking behaviour of<br />

the pavement, It is better to use alkaline aggregates<br />

rather than acid aggregates to c<strong>on</strong>struct<br />

pavement, because the former has a higher<br />

coherence with asphalt, thus a higher capacity<br />

of anti-cracking.<br />

Determinati<strong>on</strong> o f grain di'stributi<strong>on</strong> of aaRreRates<br />

Test results show that the asphalt mixture withthe<br />

grain distributi<strong>on</strong> of aggregates listed in<br />

Table I11 is favourable in anti-cracking, so that<br />

it is recommended to the c<strong>on</strong>structi<strong>on</strong> of road<br />

pavement. The ratio of asphalt to aggregates<br />

should be also c<strong>on</strong>sidered in preparati<strong>on</strong> of the<br />

pavement material. It is better to take the<br />

value of the ratio as 4.2-5.2. In additi<strong>on</strong>,attenti<strong>on</strong><br />

should also be paid to the ratio between<br />

mineral powder and asphalt. It can be determined<br />

through the split tests c<strong>on</strong>ducted at the<br />

lowest local air temperature, usually taking a<br />

value of 1.2.<br />

Design of road profile<br />

Practical engineering showed that to prevent<br />

cold craking, design ofhthe road profile of an<br />

asphalt-paved road should be made in c<strong>on</strong>siderati<strong>on</strong><br />

of the operati<strong>on</strong>al performance of the road<br />

in cold climate. The following aspects should<br />

be particularly taken into account: (a) Reducing<br />

the difference in modula of pavement, roadbed<br />

and subgrade so as to avoid excessive c<strong>on</strong>sentrati<strong>on</strong><br />

of tensile stress at the interlayers. (b)<br />

Under the prerequisite of meeting the needs of<br />

designed strength of pavement, cutting down the<br />

aggregate c<strong>on</strong>tent to reduce the cold c<strong>on</strong>tracti<strong>on</strong><br />

of the pavement. (c) Thickening the roadbed<br />

and strengthening the coherence am<strong>on</strong>g pavement,<br />

roadbed and subgrade to avoid the underlying<br />

reflective cracks penetrating into pavement.<br />

(d) Increasing the strength pavement and roadbed,<br />

(e) Stabilizing the roadbed with various kinds<br />

of inorganic adhesives such as lime, cement and<br />

coal powder, The mixing ratios of the inorganic<br />

adhesives and soils recommended by the Beijing<br />

Institute of Municipal Engineering are show in<br />

Table IV. (f) Placing insulati<strong>on</strong> layer (plastic<br />

film, earth fabric or sand and gravel) in roadbed<br />

to reduce the frost heave of the road. (9)<br />

Properly designing the water drainage and water<br />

proof system. In additi<strong>on</strong>, carefully c<strong>on</strong>trolling<br />

the heating temperature and elapsed time<br />

of asphalt, ensuring the quality of c<strong>on</strong>structi<strong>on</strong><br />

and severely maintaining the road are also<br />

important for t :he preventi<strong>on</strong> of .cold cracking.<br />

TABLE IV<br />

Recommended Mixing Ratios of Inorganic<br />

Adhesives and Soils<br />

Material Mixing ratio<br />

Lime: sand and gravel 5:95 or 7.93<br />

Lime: fine soili sand &<br />

gravel 1.8:13.2:85 or 2.4:17.6:80<br />

Lime: coal powder: sand &<br />

gravel 5:15:80 or 3.75:11.25:85<br />

Lime: sand and gravel 6.94<br />

Cure of cracks<br />

Once cracking occurs in pavement, proper cure<br />

measures should be taken. For those finer cracks<br />

which will be naturally closed in warm seas<strong>on</strong>,<br />

no treatment is needed at the moment. Whereas,<br />

for the wider' and deeper cracks, proper treatment<br />

must be d<strong>on</strong>e in time. A comm<strong>on</strong>ly used measure<br />

is to fill the cracks with various sorts of pavement<br />

material such as rubber asphalt, resin asphalt,<br />

asphalt-cement-sand mixture. The choice<br />

of the material depends up<strong>on</strong> the size of cracks.<br />

Once cracks occured in a wide area <strong>on</strong> pavement,<br />

it is better to lay a thin layer (9-19 mm thick)<br />

of rubber asphalt, emulsified asphalt or foamed<br />

asphalt <strong>on</strong> the road surface covering the whole<br />

cracking area rather than to fill the cracks<br />

individually.<br />

CONCLUSIONS<br />

Investigati<strong>on</strong> shows that the cold cracking of<br />

asphalt pavement depends up<strong>on</strong> cold c<strong>on</strong>diti<strong>on</strong><br />

(temperature and freezing index), physical properties<br />

of pavement materials (asphalt, mineral<br />

aggregates and other additives), moisture c<strong>on</strong>diti<strong>on</strong><br />

and type of roadbed and subgrade, structure<br />

of road profile and trafic density. After<br />

knowing the temperature stress and tensile'<br />

strength of a pavement material as a functi<strong>on</strong> of<br />

TABLE<br />

111<br />

Recommended Grain-size Distributi<strong>on</strong> of Aggregates in the C<strong>on</strong>structi<strong>on</strong><br />

of Asphalt Road Pavement<br />

Grain<br />

size, mm 25 20 10 5 2.5 1.2 0.6 0.3 0.15 0.075<br />

Finer by<br />

weight<br />

100 82-95 50-65 30-50 22-35 - 15-28 10-25 4-12 3-7

temperature, cracking temperature of the pavement<br />

can be predicted. Cold cracking can be<br />

successfully prevented by correct choice of thc<br />

pavement materials and their mixing ratios,<br />

reas<strong>on</strong>able design of road profile (pavement,<br />

roadbed, subgrade and insulati<strong>on</strong> layer if necessary)<br />

and severe c<strong>on</strong>trol of c<strong>on</strong>structi<strong>on</strong> quality<br />

REFERENCES<br />

T<strong>on</strong>g Changjiang and Guan Fengnian, (1985). Frost<br />

Heave of Soils and Preventi<strong>on</strong> and Cure of<br />

Frost Damage of Structures. Hydraulic and<br />

Power Publishing House, 1985.<br />

Wu Ziwang, Zhang Jiayi, Wang Yaqing and Shen<br />

Zh<strong>on</strong>gyan, (1981). Experimental studies <strong>on</strong><br />

frost heave of soils, Collected Papers of<br />

the Lanzhou Inatitute of Glaciology and<br />

Geocryology, Academia Sinica, No.2, pp.<br />

82-96, Chinese Science Press, 1981.<br />

1499

AIRPORT NETWORK AND HOUSING CONSTRUCTION PROGRAMMES<br />

IN NORTHERN QUEBEC, CANADA<br />

C. Tremblayl and G. Do&<br />

' 1QuCbee Department of Transport Quebec, Canada<br />

2Service des Sols et Chawsh, Ministere des Transports du Qudbec<br />

SYNOPSIS Some 750 000 square kllometers of Quebec territory are in permafrost z<strong>on</strong>es. Northern<br />

Quebec is far from occupied Quebec, underpopulated and underdeveloped, In 1977, the native peoples (Cries, Naskapis,<br />

Inuit) Canada and Quebec signed the James Bay & Northern Quebec agreement. To fullfil 1 their commitments governments<br />

are buildlng housing units and establishing an air transportati<strong>on</strong> network.. In Quebec, there are greatly different<br />

approches to deal with northern c<strong>on</strong>structi<strong>on</strong> programes. The houses are built ct<strong>on</strong>n frozen grounds; the airstrips are<br />

built ((in)) permafrost. So airport c<strong>on</strong>structi<strong>on</strong> in a permafrost z<strong>on</strong>e is ambiti<strong>on</strong>s and involves a great deal of<br />

technical c<strong>on</strong>siderati<strong>on</strong>s. Many c<strong>on</strong>straints have to be taken into account when choosing an airstrip site; uneasy<br />

geotechnical c<strong>on</strong>diti<strong>on</strong>s have to be dealt with by the designer. In Kangirsuk, Northern Quebec, such a situati<strong>on</strong> occured;<br />

The <strong>on</strong>e and <strong>on</strong>ly suitable site to locate the runway forced a 5 meter deep cut in ice - rich silty soil.<br />

Troubles were expected; our deficient experience in working in permafrost combined to a lack of relevant bibliographical<br />

references could not help us in evaluating their magnitudes. M<strong>on</strong>itoring the sensitive area was undertaken...<br />

Let us look at what we found in Kangirsuk since 1985.<br />

Quebec is a large eastern Canada province. Wlth more<br />

than 1 500 000 square kilometers its area is more than<br />

15% of all Canadian lands. Compare to european stantards<br />

its sizes are quite shocking; from south to north<br />

say from M<strong>on</strong>treal to Ivujivik the distance is more than<br />

2 000 kilometers and Great White River <strong>on</strong> the west coast<br />

(Huds<strong>on</strong> Bay) is 1 200 kilometers away from the Gulf of<br />

St-Lawrence. Our Quebec al<strong>on</strong>e is wider than all the<br />

nine EEC countries.<br />

About orequarter of Quebec territory is in a c<strong>on</strong>tinious<br />

permafrost z<strong>on</strong>e, and about 50% approximately 750 000<br />

square kilometers - in a disc<strong>on</strong>tinious permafrost z<strong>on</strong>e.<br />

This vast northern area with its perennially frozen<br />

ground and subsoil is far from occupied Quebec, not<br />

very accessible, and virtually if not entirely uninhabited<br />

and/or developed. It is very appealing to the<br />

rest of Quebec because of tts wealth of natural resources<br />

and the hydroelectric potential of all its fresh<br />

watercourses which flow towards the North, towards the<br />

Northern seas.<br />

For centuries, the native people of those remote countries,<br />

for obvious histwical reas<strong>on</strong>s had very little<br />

social , commercial ar administrative matters with both<br />

Quebec and Canada Governments. In early seventies the<br />

always increasing needs for energy and ressources moved<br />

up north southerners eager to exploid the huge potential<br />

of the barrens grounds of Northern Quebec - James<br />

Bay and Huds<strong>on</strong> Bay inhabited for l<strong>on</strong>g time by native<br />

Indians and Inuit. For the past 15 years or so these<br />

people have been at the heart of an innovative, original<br />

governement scheme which wil have a great impact <strong>on</strong><br />

resource development and, as a result, <strong>on</strong> infrastructures<br />

of all kinds.<br />

In 1977, when the Canada and Quebec governments, the<br />

James Bay Crees, Quebec Naskapis and the Inuit of Nouveau-Quebec<br />

signed the James Bay and Northern Quebec<br />

Agreement, all the parties to the c<strong>on</strong>tract were comitting<br />

themselves to a vast undertaking <strong>on</strong> all northern<br />

coasts.<br />

1500

The James Bay and Northern Quebec Agreement is a sizable<br />

modern-type c<strong>on</strong>tract which the two (2) governments signed<br />

with the native peoples. It is c<strong>on</strong>tained in a book<br />

of six hundred-odd (600) pages broken down into thirty<br />

(30) highly-detailed chapters, and it touches up<strong>on</strong> all<br />

aspects of the life and development of the inhabitants<br />

of a specific area.<br />

For the V <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> c<strong>on</strong>ference <strong>on</strong> permafrost, we<br />

have selected am<strong>on</strong>g several two (2) northern infrastructures<br />

improvement and development programs:<br />

A- The c<strong>on</strong>structi<strong>on</strong> of housin units for Inuit<br />

p.eoples living north of 55% latitude north;<br />

The SHQ built its structures <strong>on</strong> well drained, n<strong>on</strong>-frost<br />

susceptible pads (granular material). Jacks were installed<br />

to support them and thereby alleviate all possibility<br />

of thermal bridges being created between the<br />

occupied areas of the buildings and the permanently<br />

frozen ground. The structures were reinforced in order<br />

to resist torsi<strong>on</strong>, and the jacks are to be adjusted over<br />

the years to keep the buildings level. Services (sanitary<br />

tanks, drinking water tanks, etc.) were all located<br />

inside the units. You do not have to know much to realize<br />

that these c<strong>on</strong>structi<strong>on</strong> techniques entail higher<br />

costs than c<strong>on</strong>venti<strong>on</strong>al <strong>on</strong>es<br />

B- The c<strong>on</strong>structi<strong>on</strong>, of a network of thirteen (13)<br />

airports to serve Inuit villages located north<br />

of 550 latitude north.<br />

These two programs were chosen because they are examples<br />

of large-scale projects in a frozen regi<strong>on</strong> which use<br />

radically different building strategles and methods.<br />

While the housing units built in the north by the SociBte<br />

d'Habitati<strong>on</strong> du Quebec (SHQ) were designed to avoid<br />

the permafrost without affecting it, envir<strong>on</strong>mental, physical,<br />

social and standardizati<strong>on</strong>-related c<strong>on</strong>straints<br />

forced the designers and builders of the northern airports<br />

to cttouch)) the permafrost and deal with this formidable<br />

adversarv.<br />

Over the past six (6) years, the SHQ has built or renovated<br />

six hundred eighty-seven (687) units and, by 1990,<br />

will spend about 65M$ an those projects that have already<br />

been approved to provide the thirteen (13) Inuit<br />

villages with some four hundred twenty (420) additi<strong>on</strong>al<br />

housing units.<br />

The SHQ's policy with respect to permafrost is as<br />

follows: <strong>on</strong>ce new c<strong>on</strong>structi<strong>on</strong> techniques that are practical<br />

and reliable have been perfected by researchers,<br />

an ec<strong>on</strong>omic analysis will be c<strong>on</strong>ducted to decide whether<br />

interventi<strong>on</strong> strategies in permafrost aeras should be<br />

a1 tered.<br />

1501

In 1983, as part of the implementati<strong>on</strong> of the James Bay<br />

gnd Northern Quebec Agreement, the Canada and Quebec<br />

governments c<strong>on</strong>cluded an umbrella agreement dealing with<br />

the c<strong>on</strong>structi<strong>on</strong> of a network of thirteen (13) airports<br />

to serve the Inuit villages created and/or recognized<br />

by the first-menti<strong>on</strong>ned Agreement.<br />

This lOOMS project slated for completi<strong>on</strong> in 1952 was<br />

initiated in 1984 with the c<strong>on</strong>structi<strong>on</strong> of the Ivujivik<br />

airport - a typical airport with a gravel landing strip<br />

1 070 metres by 30 metres ( 3 500' x loo'), a road from<br />

the village to the airport, a passanger terminal and a<br />

hangar for cargo, machinery, tools and vehicles. The<br />

runways are equipped with lights and electr<strong>on</strong>ic flight<br />

navigati<strong>on</strong> aids. Al the other villages wil be provided<br />

with similar infrastructures with the same physical<br />

characteristics,<br />

The summer 1986 c<strong>on</strong>structi<strong>on</strong> c<strong>on</strong>text was especially<br />

eventful and interesting for the program engineers and<br />

designers.<br />

Our first experience with the permafrost was at Kangirsuk<br />

<strong>on</strong> the western coast of Ungava Bay. In this particular<br />

case, we were glad that dedicated scientists had<br />

worked <strong>on</strong> finding logical and rati<strong>on</strong>al soluti<strong>on</strong>s to<br />

these sensitive problems and that we could still count<br />

<strong>on</strong> the determinati<strong>on</strong> of full teams of researchers to<br />

provide developers with techniques which greatly facilitate<br />

their task.<br />

The sec<strong>on</strong>d part of our presentati<strong>on</strong> is a summary of a<br />

technical study c<strong>on</strong>ducted in order to guarantee the<br />

c<strong>on</strong>structi<strong>on</strong> of a reliable landing strip at Kangirsuk<br />

and to improve up<strong>on</strong> the design of the projects slated<br />

forthe other villages.<br />

PART 2;<br />

Technical C<strong>on</strong>siderati<strong>on</strong>s<br />

1. Introducti<strong>on</strong>: The c<strong>on</strong>text<br />

It is quite a challenging experience working as a soil<br />

engineer and pavement designer for an airport building<br />

program in the north but, in some respects, not too<br />

rewarding a task. In fact, soils seem to be the last<br />

factor taken into account when choosing the site of an<br />

airfield. Social and envir<strong>on</strong>mental c<strong>on</strong>siderati<strong>on</strong>s are<br />

dealt with first as well as technical factors which are<br />

more closely related to aer<strong>on</strong>autics.<br />

It then becomes a challenge to determine proper pavement<br />

design in view of the fact that gravel-wearing surfaces<br />

may not justify sophisticated and expensive design features<br />

such as insulati<strong>on</strong> or thermo probes but do deserve<br />

good protecti<strong>on</strong> against poor performance due tO the<br />

presence of permafrost in the underlying terrain.<br />

One might think at first glance that a gravel surface<br />

requires very little design effort <strong>on</strong> account of the relatively<br />

low investment that it implies and of the easy<br />

and cheap maintenance it is liable to require. However,<br />

when ten airports involving a total investment of<br />

lSOW$ are c<strong>on</strong>cerned, it becomes worthwhile to emphasize<br />

technical studies in order to optimize the structural<br />

designs and therefore l<strong>on</strong>g-term performance.<br />

2. Development Limitatj<strong>on</strong>s<br />

Many factors are to be c<strong>on</strong>sidered prior to the selecti<strong>on</strong><br />

of an airfield site. Most of them are related to the<br />

needs of the community, aer<strong>on</strong>autical requirements, envir<strong>on</strong>mental<br />

c<strong>on</strong>siderati<strong>on</strong>s as well as the topographical<br />

and geological c<strong>on</strong>text. These factors make it very difficult<br />

to select a proper site even in a regi<strong>on</strong> as vast<br />

and little populated as northern Quebec.<br />

Social Requirements:<br />

The needs of the community are a key c<strong>on</strong>siderati<strong>on</strong>. The<br />

airport has to be as close as possible to the village<br />

without aircraft takeoffs and landings c<strong>on</strong>stituting a<br />

danger or causing stress. Traditi<strong>on</strong>al hunting and gathering<br />

sites, graves, trails, reference points and<br />

archeological sites must also be protected.<br />

Aer<strong>on</strong>autical Norms:<br />

Strict l<strong>on</strong>gitudinal and traverse clearence norms have to<br />

be taken into account when designing the geometry of an<br />

airfield. Maximum slope and inflecti<strong>on</strong> standards must<br />

also be observed. The orientati<strong>on</strong> of the runway can be<br />

determined <strong>on</strong>ly after due c<strong>on</strong>siderati<strong>on</strong> to the directi<strong>on</strong><br />

of the prevailing winds.<br />

Envir<strong>on</strong>ment : .<br />

The arctic tundra c<strong>on</strong>stitutes a very sensitive envir<strong>on</strong>ment.<br />

For instance,wen a minor change in the thin<br />

organic layer, may leave scars that could never disappear.<br />

Archeological sites, nesting areas, vulnerable<br />

streams and visual aspects are some of the important<br />

points to be studied to evaluate the impact of the<br />

project.<br />

Topography and Geology:<br />

It is easy to figure out how cost and feasibility of a<br />

project can be affected by the relief of the terrain.<br />

It is however a little bit more difficult to determine<br />

the role played by geology. Two major problems have<br />

come up since the beginning of the airport programme-.<br />

They are the rarity of granular materials and the difficulties<br />

occurring in cut secti<strong>on</strong>s <strong>on</strong> frost susceptible<br />

soils.<br />

The geological c<strong>on</strong>text caused great difficulty to the<br />

engineers while prospecting granular materials and designing<br />

foudati<strong>on</strong>s in cut secti<strong>on</strong>s <strong>on</strong> frost susceptible<br />

soils. Since ill our mind the exploitati<strong>on</strong> of sand or<br />

gravel pits would cause great harm to the envir<strong>on</strong>ment<br />

and deprive Inuit cornunities of these scarce ressources,<br />

granular material was to be produced essentially from<br />

crushed st<strong>on</strong>e. Besides, the lack of bibliographical<br />

references that deal with c<strong>on</strong>structi<strong>on</strong> of gravel airfield<br />

pavements in permafrost areas and our own lack of experience<br />

in that field combined to the problems encoutered<br />

during the first excavati<strong>on</strong> in frost susceptible soils,<br />

led to a specific study of the Kangirsuk airport.<br />

1502

3. Kangirsuk <strong>Research</strong> project<br />

3.1 Introducti<strong>on</strong><br />

The Kangirsuk airstrip is a typical example of a<br />

permafrost hazard. It required a 200m l<strong>on</strong>g excavati<strong>on</strong><br />

to a maximum depth of 5m that was d<strong>on</strong>e by blasting the<br />

groten ground. Since no borehole had reached the subbase<br />

level, very little was know about the soil and<br />

the permafrost at that point.<br />

:i1lO 11D<br />

FIG. 2 Pavement structure in cut z<strong>on</strong>e<br />

KANGIRSUK AIRSTRIP<br />

3.2 Geotechnical C<strong>on</strong>text<br />

Excavati<strong>on</strong>s and subsequent soil testing revealed<br />

that the granular pavement was to be placed <strong>on</strong> top of<br />

an ice-rich silty sand.<br />

The problem area is charactarized by an outwashed<br />

glacial till (approx. Imthick) <strong>on</strong> top of a fine-grain<br />

matrix till. Bedrock depth in the middle of the cut<br />

secti<strong>on</strong> is appsNmately 5.5m.<br />

Soil at that point was c<strong>on</strong>stituted of up to 80% (in<br />

volume) ice lenses (average 50%) (figure 1). Results of<br />

testing showed fairly c<strong>on</strong>sistent water and fine-grain<br />

(

Thaw Line:<br />

. Five electr<strong>on</strong>ic thermometers were installed al<strong>on</strong>g<br />

a l<strong>on</strong>gitudinal and a transverse secti<strong>on</strong> <strong>on</strong> the runway.<br />

Each thermometer was c<strong>on</strong>stituted of six equally-spaced<br />

thermocouples <strong>on</strong> a 2.4 meter deep probe.<br />

FIG. 5 Thaw Penetrati<strong>on</strong> during the first<br />

CROSS-SECTION 01-880<br />

wwrmlm<br />

two years<br />

Settlement and Frost Heave:<br />

These two parameters were to be measured by means<br />

of nine level references instalqed <strong>on</strong> the subbase surface.<br />

. A metal rod protected by a metal cylinder enabled<br />

thereading of the reference marks installed in the pavement.<br />

Bearing Strenght:<br />

In order to measure the bearing capacity of soilsin<br />

the active layer, two 30 cm plates were installed under<br />

the runway and protected by metal cylinders. They were<br />

left in place to be tested when the thaw line reached<br />

its maximum depth.<br />

S1 ope Movement :<br />

Three reference marks were placed <strong>on</strong> the slope<br />

al<strong>on</strong>g a cross-secti<strong>on</strong> where the cut was the deepest.<br />

These mirks should make it possible to record the<br />

extent of slope movement due to soliflucti<strong>on</strong> or slumping.<br />

3.5 Findings<br />

After two seas<strong>on</strong>s of thawing in Kangirsuk, data and<br />

observati<strong>on</strong>s were compiled to produce a preliminary report.<br />

The main findings of that first part of the<br />

study are as follows:<br />

Active layer<br />

After the first seas<strong>on</strong> of thawing, the active layer<br />

was 40 to 60 cm thick under the pavement structure while<br />

it reached 160 cm under the ditch. During the sec<strong>on</strong>d<br />

seas<strong>on</strong>, the thaw line dJd not exceed the maximum depth<br />

reached the previous year (figures 4 & 5). Two factors<br />

could ,explain a thinner active layer during that sec<strong>on</strong>d<br />

seas<strong>on</strong>. They are the possible colder sumr and the<br />

additi<strong>on</strong>, of a 150 mn thick surface gravel layer at<br />

the end of the first seas<strong>on</strong>.<br />

FIG. 4 Typical Thermocouple Record<br />

Settlement<br />

The settlement was found to be very irregular. The<br />

average reading .during the first reas<strong>on</strong> was about 15 cm<br />

but it was as high as 23 cm at certain spots. During<br />

the sec<strong>on</strong>d seas<strong>on</strong>, 1 to 5 cm.of additi<strong>on</strong>al settlement<br />

was recorded in spite of the shallow active layer.<br />

Depressi<strong>on</strong>s were observed in the crown of the subgrade<br />

(figures 6, 7, 8, 9.)<br />

FIG. 6 Typical Settlement record<br />

SmLEMENT<br />

: I<br />

i la ! I<br />

1504

FIG. 7<br />

A0<br />

m<br />

l(0<br />

mn<br />

m<br />

rw<br />

1 110<br />

1<br />

100<br />

Extreme Settlement Record<br />

mEMENl<br />

STATION N-8<br />

. ~ , , , , , , , , 1 1 1 , I . , I 1 8<br />

0 z 4 6 I IO It 11 16 11<br />

"M1-I<br />

FIG. 8 Settlement: l<strong>on</strong>gitudinal secti<strong>on</strong> (1986 and 1987)<br />

LONGITUDINAL SECTION (O/S:l4 mD)<br />

The additi<strong>on</strong> of riprap in the ditch caused an additi<strong>on</strong>al<br />

settlement of 10 cm that kept the drainage point<br />

below the platform.<br />

At this early stage of the study. no findings were<br />

as yet available <strong>on</strong> the extent of l<strong>on</strong>g - Term settlement<br />

Trends.<br />

Bearing capacity<br />

The bearing plate tests performed <strong>on</strong> the active<br />

layer after thawing and c<strong>on</strong>solidati<strong>on</strong> by the granular<br />

foundati<strong>on</strong>, showed results slightly lower (10 to 15%).<br />

Than the predicted spring-reduced bearing strenght. It<br />

thus c<strong>on</strong>firm that well drained soils in those c<strong>on</strong>diti<strong>on</strong>s<br />

could regain expected bearing capacity.<br />

Frost heave<br />

During the <strong>on</strong>ly freezing seas<strong>on</strong> m<strong>on</strong>itored so far,<br />

no significant heaving had occured. This might be related<br />

to the high thermic gradienfer that probably lead to<br />

d fast freezing of the active layer.<br />

Slope stability<br />

The cut slope was affected by active erosi<strong>on</strong> (figure<br />

10) and by undefined soliflucti<strong>on</strong> movement. his sinkholes<br />

(up to 60 cm deep) were also observed. The' filtering<br />

bank was found to be efficient in c<strong>on</strong>troling eroded<br />

sediments altough overflowing occured in few spots.<br />

FIG. 9 Settlement: cross-secti<strong>on</strong> (1986 and 1987)<br />

CROSS-SECTION 0+880<br />

3.6 Recommandati<strong>on</strong>s<br />

101.7<br />

a 101.1<br />

g 101.1<br />

9 101.4<br />

101.3<br />

The first part of the study led to 'the proposal of<br />

the following preliminary design principles for future<br />

sites.<br />

- If feasible cuts should be cuts should De avoided<br />

in frost susceptible soils.<br />

- ff a cut is unavoidable, the subbase thickness<br />

should be sufficient to minimize the penetrati<strong>on</strong> in<br />

subgrade and differential movement related to<br />

freeze-thaw cycles. A preliminary bibliographical<br />

approach would suggest a total granular thickness<br />

of 1,5 m protected against c<strong>on</strong>taminati<strong>on</strong>, as being<br />

a proper foundati<strong>on</strong> in such c<strong>on</strong>diti<strong>on</strong>s (Laing,1983)<br />

- If possible, excavati<strong>on</strong>, preparati<strong>on</strong> of the subgrade<br />

and placing the subbase should be performed early<br />

in the seas<strong>on</strong> while placing top layers of the<br />

1505

foundati<strong>on</strong> should be d<strong>on</strong>e at the end of the thawing<br />

period. Such a method should result in a deep thaw<br />

penetrati<strong>on</strong> during the first year. The additi<strong>on</strong> of<br />

the base layer later in the seas<strong>on</strong> would correct<br />

the first year settlement while it should ensure a<br />

shallower thaw penetrati<strong>on</strong> during the subsequent<br />

years.<br />

- The crown should be accentuated to achl'eve a 3%<br />

traverse slope.<br />

- The structural design should take into account a<br />

10% to 15% additi<strong>on</strong>al reducti<strong>on</strong> factor for the<br />

active layer bearing capacity.<br />

- The drainage system should be protected against<br />

active sedimentati<strong>on</strong> from cut slope erosi<strong>on</strong> and<br />

soliflucti<strong>on</strong> - type landslides. Slope stabilisati<strong>on</strong><br />

should be str<strong>on</strong>gly c<strong>on</strong>sidered.<br />

C<strong>on</strong>clusi<strong>on</strong><br />

C<strong>on</strong>sidering all the m<strong>on</strong>ey being invested in the northern<br />

Quebec airport programme, the Kangirsuk study is obviously<br />

worthwhile. C<strong>on</strong>clusi<strong>on</strong>s should lead to a better<br />

comprehensi<strong>on</strong> of permafrost and thereby improve our de- '<br />

sign and c<strong>on</strong>structi<strong>on</strong> methods in that particular c<strong>on</strong>text.<br />

The l<strong>on</strong>g-term m<strong>on</strong>etary as well as technical benefits<br />

should be profitable to the Inuit comnunities<br />

and to Quebec.<br />

Re,ferences<br />

- Ouvrir le Nord a pas feutres, Pil<strong>on</strong> J.A., Beaudoin<br />

A. Geos 1984/4.<br />

- Road C<strong>on</strong>structi<strong>on</strong> in Palsa fields, Keyser J.H.,<br />

Laforte M.A., Presentati<strong>on</strong> du T.R.B. Washingt<strong>on</strong>,<br />

1984<br />

- Problems de c<strong>on</strong>cepti<strong>on</strong> des chaussees dans le Nord<br />

Quebecois, Revue Routes et Transports, Printemps<br />

1984<br />

- Evaluati<strong>on</strong> of experimental Design features for roadway<br />

c<strong>on</strong>structi<strong>on</strong> over permafrost, Esch. D.C. <strong>Permafrost</strong>:<br />

fourth annual c<strong>on</strong>ference, Alaska 1983<br />

- Determinati<strong>on</strong> of critical Height of railroad embank-<br />

ments in the permafrost regi<strong>on</strong>s of the Quinghai-<br />

Xizang Plateau, Xinoming H., <strong>Permafrost</strong>: fourth<br />

annual c<strong>on</strong>ference, Alaska 1983<br />

- In situ Direct Shear tests at the freeze / thaw<br />

interface and in thawed soils, Zhiquan T., <strong>Permafrost</strong>:<br />

fourth annual c<strong>on</strong>ference, Alaska, 1983<br />

- Infrastructure des Transports: les effets de gel<br />

et les moyens de Protecti<strong>on</strong>, Keyser J.H.<br />

- Engineering in the North, Laing J.M., fifteenth<br />

musked research c<strong>on</strong>ference, may 1983<br />

1506

FROST DAMAGE OF ENCLOSURE AND ITS MEASURE<br />

FOR PREVENTING FROST HAZARD<br />

Wan& G<strong>on</strong>gshan<br />

Heil<strong>on</strong>gjiang Provincial Low Temperature C<strong>on</strong>structi<strong>on</strong> Science <strong>Research</strong> Institute<br />

SYNOPSIS The main reas<strong>on</strong>s producing enclosure crack in seas<strong>on</strong>al frost regi<strong>on</strong> might be c<strong>on</strong>cluded<br />

as follows: the first is the deformati<strong>on</strong> difference of foundati<strong>on</strong> bed with various facing;the<br />

sec<strong>on</strong>d is the difference of tangential frost heaving force around foundati<strong>on</strong>; the third is the dif-,<br />

ference of normal frost heaving force acting <strong>on</strong> the bottom of foundati<strong>on</strong>. Our. observati<strong>on</strong> results '<br />

show that: the enclosure with an eccentrically loaded foundati<strong>on</strong> can be able to reduce inclined degree<br />

about 92 to 97% caused by south fac1ng;and the enclosure with a c<strong>on</strong>e foundati<strong>on</strong> is available<br />

for reducing the acti<strong>on</strong> of tangential frost heaving force <strong>on</strong> the lateral surface of foundati<strong>on</strong> about<br />

77%. Beside above, because the weakness of subsoil after freeze-thawing cycles will be happened, a<br />

weakness coefficient, less than 1, should be c<strong>on</strong>sidered while designing the-bearing capacity of subsoil<br />

if the foundati<strong>on</strong> depth is less than the maximum frost depth.<br />

INTRODUCTION<br />

Up to now, more and more enclosures, with a simple<br />

and light structures, have been built in<br />

the areas with frost susceptible soils. However,<br />

they were broken in several years or sometimes<br />

in several m<strong>on</strong>ths aEter building because of<br />

str<strong>on</strong>g frost acti<strong>on</strong>. In order to explore the<br />

characteristics and mechanism of frost damage<br />

of enclosures and its preventati<strong>on</strong> measures, we<br />

have investigated many phenomena about frost<br />

acti<strong>on</strong> <strong>on</strong> enclosures worked years and built some<br />

with various type$ of foundati<strong>on</strong> for experiment<br />

in Yejiangan observati<strong>on</strong> stati<strong>on</strong> during 1983 to<br />

1986. After three freeze-thawing cycles test,<br />

some experimental results €or preventing enclosures<br />

from frost damage have been got which<br />

were recommened in this paper.<br />

MAIN REASONS ON FROST DAMAGE OF ENCLOSURE<br />

The effect of directi<strong>on</strong> <strong>on</strong> the stability of<br />

enclosure<br />

The freezing and thawing speed in both sides of<br />

enclosure with a east-west directi<strong>on</strong> is quite<br />

different because of various sunshine time. In<br />

winter. the frost penetrati<strong>on</strong> rate, the frost<br />

depth and frost heave amount o f subsoil i n the<br />

north facing side will be much larger than that<br />

in the south facing side. The angle deformati<strong>on</strong><br />

(Fig.1) produced by differential heave between<br />

north and south side can be expressed by<br />

81 = arc sin(Ahl/B) (1)<br />

where B is the width of foundati<strong>on</strong>. The centre<br />

of gravity o f enclosure has been moved to the<br />

south. During spring, the thawing speed in the<br />

north facing side is rather slow. While the<br />

thawing depth is over to the bo,ttom of foundati<strong>on</strong><br />

in the north aide, there-is a centain thickness<br />

of thawing layer under foundati<strong>on</strong> in the south<br />

side. So the thawing settlement of the foundati<strong>on</strong><br />

in the south side will be certainly much<br />

larger than that in the north side,,with a differential<br />

displacement of Ah2, because of the<br />

T ""<br />

/<br />

Base level<br />

aPter freezing<br />

"<br />

Bnse level<br />

befom frseaina<br />

Fig.1 A Digram <strong>on</strong> Displacement<br />

Process of Enclosure<br />

weakness of thawing Layer and the movement of<br />

the centre of gravity of enclosure towards the<br />

south side, cause by differential heave which<br />

makes enclosure inclined to the south with an<br />

angle deformati<strong>on</strong> Ozexpressed by<br />

e2 - arc sin (Ah2/B) (2)<br />

After thawing, the total angle displacement of<br />

1507

enclosure to the south is 8=e1+82. Meanwhile,<br />

the gravity can be divided two parts PI and P2<br />

which al<strong>on</strong>g the directi<strong>on</strong> and normal to the directi<strong>on</strong><br />

of vertical axial of enclosure respectively<br />

p1 = P e (3)<br />

P, = P sin 0 (4)<br />

The eccentrici ty, e , will be increased with the<br />

increase of 8, so will be the PZ which makes<br />

enclosure incl ined, and even broken.<br />

L-the distance between two observati<strong>on</strong><br />

points, cm.<br />

EXPERIMENTAL RESULTS AND ANALYSIS<br />

The,relati<strong>on</strong> of freeze-thawing penetrati<strong>on</strong> depth<br />

in both sides of enclosure vs elapsed time is<br />

shown in Fig.2. After analysing the observati<strong>on</strong><br />

results obtained in situ, some ideas might be<br />

made as follows:<br />

The effect of tanRential frost heaving force <strong>on</strong><br />

the stability of enclosure<br />

Even if the foundati<strong>on</strong> depth of enclosure is<br />

rather deep or deeper than the maximum frost<br />

depth, when the backfill around foundati<strong>on</strong> is<br />

frost susceptible, the lateral surface of foundati<strong>on</strong><br />

is acted under frost tangential heaving<br />

force which makes foundati<strong>on</strong> produced tansi<strong>on</strong><br />

crack and tansile failure with a directi<strong>on</strong> to<br />

parallel to horiz<strong>on</strong>tal level near frost fr<strong>on</strong>t.<br />

ElapJsd time (m<strong>on</strong>th)<br />

The effect of normal frost heaving force <strong>on</strong> the<br />

stability of enclosures<br />

When the foundati<strong>on</strong> depth of enclosure is rather<br />

deep but less than maximum frost depth, the enclosure<br />

may be failed under the acti<strong>on</strong> of normal<br />

frost heaving force which causes differential<br />

heave. If the space between the bottom of bearing<br />

brick arch or c<strong>on</strong>crete beam of enclosure and<br />

the ground surface is less than the maximum<br />

frost heave amount, the arch or beam will be<br />

acted under normal heaving force at the middle or<br />

the end of freezing period which, of course,<br />

makes enclosure cracked and broken also.<br />

EXPERIMENT IN SITU<br />

The experimental field is located in Yejianggan<br />

farm with yellow sandy clay in active layer,<br />

maximum frost depth of 1 .2 to 1.4 m, and a homogeneous<br />

frost heave amount of 30.6 cm. The<br />

ground water level was always deeper than the<br />

frost penetrati<strong>on</strong> fr<strong>on</strong>t, and was around -1.0 m<br />

in autumn and the deepest <strong>on</strong>e of -2.15 m. The<br />

observati<strong>on</strong> points of vertical deformati<strong>on</strong> were<br />

set up at the both north and south sides of experimental<br />

enclosures, the displacement of<br />

ground surface and frost penetrati<strong>on</strong> depth were<br />

also c<strong>on</strong>ducted. However, the vertical angle<br />

deformati<strong>on</strong> was calculated by the vertical differential<br />

deformati<strong>on</strong> of both north and south<br />

sides, i.e.<br />

Fig.2 Frost Depth vs Elapsed Time in ,<br />

Both Sides of Foundati<strong>on</strong><br />

1. Reducing incline of enclosure is an important<br />

measure for preventing structure from frost<br />

damage. Our results show that it is not necessary<br />

and not ec<strong>on</strong>omy to make an enclosureproduced<br />

no frost heave. If the anti-incline measure and<br />

settlement joint are set up reas<strong>on</strong>ably, the enclosure<br />

will not be failure even though with a<br />

rather vertical displacement.<br />

Because of a larger ratio of height and width<br />

of enclosure,and its higher centre of gravity,<br />

the effect of inclined angle of foundati<strong>on</strong> <strong>on</strong><br />

the stress distributi<strong>on</strong> of subsoil is rather<br />

str<strong>on</strong>g when the eccentricity of foundati<strong>on</strong> is<br />

less than B/6, the stress of subsoil may De calculated<br />

as follows:<br />

omax = N/F (1+6e/B)<br />

Umin = N/F (1-6e/B)<br />

(7a)<br />

(7b)<br />

Ah = hN hS (5)<br />

and 8 = arc sin (Ah/L)( 61<br />

where, hN-north vertical deformati<strong>on</strong> of enclosure,<br />

cm;<br />

hS-south vertical deformati<strong>on</strong> of enclosure,<br />

cm;<br />

where, Oma,-the maximum stress of subsoil, Pa;<br />

omin--the minimum stress of subsoil, Pa;<br />

N-total load acting subsoil, N;<br />

F-cross secti<strong>on</strong>20f the bottom of<br />

foundati<strong>on</strong>, m ;<br />

B-width of foundati<strong>on</strong> bottom, m;<br />

e-eccentricity,m, e=h'tge, h is the<br />

neight of centre of .gravity.<br />

1508

Our experimental results show that the compressive<br />

stress at the south bottom of type 1 foundati<strong>on</strong><br />

(Fig.3) was 7.23 times over that at the<br />

tyue I<br />

'YW 4<br />

I<br />

h<br />

"type 1<br />

Elapsed time (m<strong>on</strong>th)<br />

Elapsed time (m<strong>on</strong>th)<br />

Fig.3 Angle Deformati<strong>on</strong> vs Elapsed Time<br />

of Eccentrically Loaded Foundati<strong>on</strong><br />

Fig.4 Angle Deformati<strong>on</strong> vs Elapsed Time<br />

with C<strong>on</strong>e Shapped Foundati<strong>on</strong><br />

north bottom after two freeze-thawing cycles<br />

which makes the enclosure of type 1 lain down<br />

after the three cycles. Type 4 and type 6<br />

foundati<strong>on</strong>s have been added an eccentrical load<br />

with opposite directi<strong>on</strong> before working in order<br />

to deal with the differential deformati<strong>on</strong> problem.<br />

In this case, the compressive stress of<br />

subsoil at the bottom of foundati<strong>on</strong> in the south<br />

side will be very small, so will be its deformati<strong>on</strong>.<br />

We assume that the allowable stress of<br />

subsoil, U, is given after thawing, the maximum<br />

incline angle emax can be calculated by formula<br />

between frozen ground and the lateral surface<br />

of foundati<strong>on</strong>. If the lateral deformati<strong>on</strong> of<br />

frozen ground is so small that it is not necessary<br />

to be c<strong>on</strong>sisdered, which means that <strong>on</strong>ly '<br />

the part of frost fr<strong>on</strong>t c<strong>on</strong>nect to the surface<br />

,of foundati<strong>on</strong>. Therefore, the adfreezing area<br />

is so small that the c<strong>on</strong>necti<strong>on</strong> is very easy to<br />

be broken. Thus, the space will be developed<br />

with the increase of frost penetrati<strong>on</strong> depth<br />

which is almost equal to the frost heave amount<br />

of subsoil (see Fig.5).<br />

(8) I<br />

%ax = arc tgA(,F/N - 1)<br />

6h<br />

(8)<br />

The enclosure will be lain .down while the inclined<br />

angle i s more than the emax.<br />

2. Reducing tangential frost heaving force is an<br />

effective way .for preventing enclosure from<br />

frost damage. The enclosure with type 8 found'ati<strong>on</strong><br />

(see Fig.4) has been lain down after two<br />

freeze-thawing cycles even though its foundati<strong>on</strong><br />

depth was over the maximum frost depth. Therefore,<br />

it will be not able to get a good result<br />

in the c<strong>on</strong>diti<strong>on</strong> of <strong>on</strong>ly increasing the foundati<strong>on</strong><br />

depth, but never reducing the tangential<br />

frost heaving force. In order to reduce the<br />

effect of tangential heaving force, a test enclosure<br />

of type 8 (see Fig.4) with a c<strong>on</strong>e shapped<br />

foundati<strong>on</strong>, with a backfill of frost susceptible<br />

soil, has been c<strong>on</strong>ducted. Its experimental result<br />

was quite different from that of type 8.<br />

A space between f rozen ground and c<strong>on</strong>e founda:<br />

ti<strong>on</strong> will be occu red when surface part uplifts<br />

vertically under the acti<strong>on</strong> of frost heaving<br />

force. which will reduce the adfreezing area<br />

Fig.5 A Deformati<strong>on</strong> Digram of Soil Block<br />

Around the Foundati<strong>on</strong> with C<strong>on</strong>e Shapped<br />

3. Weakness phenomena while thaw ing of frozen<br />

subsoil. If the plastic deforma ti<strong>on</strong> of subsoil<br />

1509

1.0 tor slight or no trost susceptlale 9011<br />

respectively. C<strong>on</strong>squently, the subsoil strength<br />

of enclosure, changed with the facing directi<strong>on</strong>,<br />

should be more than its maximum stress produced<br />

by loading.<br />

where, [ol-allowable bearing capacity of unfrozen<br />

soil, Pa.' Comparing formulas (5),<br />

(6), (7) and (9), we may have following expressi<strong>on</strong><br />

:<br />

N 6htg arc<br />

sin(-)<br />

hN-hS<br />

[OI&"(l+ B )<br />

KF<br />

B<br />

(10)<br />

If there is no effect of the facing directi<strong>on</strong>, ,<br />

formula (10) will be much simple:<br />

[u] z L<br />

KF<br />

CONCLUSIONS<br />

1. The incline to the south of enclosure mainly<br />

occures in the thawing period of subsoil because<br />

the different thawing speed in each side of enclosure<br />

makes differential thawing settlement:<br />

(see type 1 foundati<strong>on</strong>). The incline degree can<br />

be reduce about 92% to 97W by using eccentrically<br />

loaded foundati<strong>on</strong> (see type 4 and type 6 foundati<strong>on</strong>).<br />

2. For the enclosure of deep buried foundati<strong>on</strong><br />

without any anti-heave measure around its lateral<br />

surface, the frost heave of the enclosure will<br />

be happened under the acti<strong>on</strong> of tangential frost<br />

heaving force, and of course,.its incline will<br />

occure during thawing. When the enclosure was<br />

set up with a c<strong>on</strong>e shapped foundati<strong>on</strong> with a c<strong>on</strong>e<br />

angle o f 24 degree, its incline degree can be<br />

reduced about 92%.<br />

3. The weakness phenomena of subsoil during<br />

* The properties of freeze-thawing Soil, "soil<br />

and Foundati<strong>on</strong>", 1977, No.7<br />

1510

APPLICATION OF LIME STABILIZATION ON HIGHWAY<br />

PERMAFROST REGION, QINGHAI-XIZANG PLATEAU<br />

Wang, Qing-td, Wu, Jing-mid and Liu, Jian-duz<br />

12nd Highway Eng Bureau of the Ministry of Communicati<strong>on</strong>, Xian, Shaanxi, China<br />

zThe First Highway Survey and Design Institute of the Ministry of Communicati<strong>on</strong>s, Xian, Shaanxi, China<br />

SYNOPSI3<br />

Qinghai-Xizang Plateau Is characteriaed by high altitude, low latitude, cold tLnd<br />

severe weather, l<strong>on</strong>g frost durati<strong>on</strong> and complex hydrogeological c<strong>on</strong>diti<strong>on</strong>. Qingzang Highway runs<br />

through the hinterland of permafrost regi<strong>on</strong> where ground ice is well developed and buried very close<br />

to ground surfaoe. It is difficult to get sand and st<strong>on</strong>e far c<strong>on</strong>structi<strong>on</strong> al<strong>on</strong>g the line under the<br />

threat flood from rivery water. So, the <strong>on</strong>ly way for preventing it from frost damage is to treat its<br />

subgrade with the lime stabilized soil(oalled "lime stabilizati<strong>on</strong>m), Since 1973, the First Highway<br />

Survey and Design Institute in co-operati<strong>on</strong> with the Science Institute of the Ministry of Communicati<strong>on</strong>s<br />

has d<strong>on</strong>e a aeries of tests <strong>on</strong> lime stabilizati<strong>on</strong> in laboratories and fields. A large number of<br />

data have been obtained from field observati<strong>on</strong> ma measurement ut the tested subgrade with the length<br />

of kilometers. It la shown that the applicati<strong>on</strong> of the lime stabilizati<strong>on</strong> <strong>on</strong> highway enginoering in<br />

permafrost regi<strong>on</strong>8 is quite gaod both in aspect of strength and of stability.<br />

Introducti<strong>on</strong><br />

Solla Stabilized with lime(ca1led "lime stabilizati<strong>on</strong>")<br />

have been effectively applied as a kind<br />

of material for highway engineering widely in<br />

China, but it is still a new object of study <strong>on</strong><br />

ita applicati<strong>on</strong> in permafrost regl<strong>on</strong>s, yet we<br />

have obtained a series of expexience, succesaful<br />

in practices, at other regi<strong>on</strong>s in China.<br />

Qingzang Plateou is typical of parmafroat table<br />

lands, spreading over a relatively large extent<br />

in regi<strong>on</strong> of moderate and comparatively low<br />

Latitudes in Qinghai province and Tibet nut<strong>on</strong>omous<br />

regi<strong>on</strong>, with the highest altitude in the<br />

world. It is a olimatic regi<strong>on</strong> of bitter cold<br />

and arid. The Preeztng seas<strong>on</strong> is 7-8 mounths<br />

l<strong>on</strong>g and the annuul mean atmospheric temperaeure<br />

is -4°C to -7°C there. The negative temperature<br />

has been recorded frequently at night, even in<br />

mounths, July or August with the highest average<br />

t'emperature yearly. It is lack of rainfall, the<br />

annual precipitati<strong>on</strong> is about 7QQ merely.<br />

Qlngzang I-li$hway Is running through the hintexland<br />

of the permafrost regi<strong>on</strong> <strong>on</strong> the Plateau for<br />

560 kilomotres in length. The altitudes al<strong>on</strong>g<br />

the Iiiehway 4500-5200 metres, the ,ground ices<br />

are very abundant everywhere. The major soil<br />

c<strong>on</strong>stituents in this regi<strong>on</strong> are silty and sandy<br />

yoils or gravel $Oils. It is lack of st<strong>on</strong>es and<br />

sands to be used for highway engineering all<br />

al<strong>on</strong>g the highway Line. Therefore, we have no<br />

choice but have to make a trial to stabilize the<br />

natural subgrade yoil of the highnay with lime<br />

as fundamental layer. of the pavement. Since 1977,<br />

the First IIighway survey and Design Institute in<br />

co-operati<strong>on</strong> with .the Communic:iti<strong>on</strong>s Science<br />

Institute of the Ministry of Communicati<strong>on</strong>s have<br />

c<strong>on</strong>ducted u good deal. of Yimulated road tests,<br />

with typical sail samples under the climatic<br />

c<strong>on</strong>diti<strong>on</strong>s which we andlogous to that to be In<br />

regi<strong>on</strong> of the Plateau, in laboratories. More<br />

than ten se~~~ments of testing ooaas with il total<br />

length about 1,6k were erected separately in<br />

different types of lime stabilized soil subgrade<br />

and mat base structure nt various testing fields<br />

and opened to trafPic. Indices nere drawn from<br />

D series of data which had been observed up<strong>on</strong><br />

the strength, road stability nnd the pavement<br />

smoothness under traffic operating during seven<br />

gears, which inaicated that the "lime stabiliziati<strong>on</strong>"<br />

is an effective approach to treatment for<br />

pavement in permafrost regi<strong>on</strong> of the Plateau.<br />

The Phisical Properties of soil3 and the Chemical<br />

Compositi<strong>on</strong> of Lime<br />

The samples used for testing of lime stabilisati<strong>on</strong><br />

were made of typical of soil, at our opti<strong>on</strong>,<br />

in various al<strong>on</strong>g the Highway, also with which was<br />

sampled at Rnrchal, for purpose to fulfill comparative<br />

tests. The physical characteristics of<br />

them are listed in table I<br />

L<br />

All dm<br />

iY)<br />

!<br />

i<br />

The c<strong>on</strong>tents of chomlcal compositi<strong>on</strong> in lime<br />

ueefor yoil stabilizati<strong>on</strong> ,tn percentuge by<br />

wei+:ht are: Cao, 60-84%: Mgo, O.R-1.5$<br />

1511

The Strength of Soil structure Stabilized with<br />

Lime<br />

We hove made samples, with the typical of various<br />

soils, stabilized with various lime c<strong>on</strong>tents,<br />

cured under different curing c<strong>on</strong>diti<strong>on</strong>a and with<br />

various curing periods, to study the strength<br />

develorrinrr with time during curing.<br />

The ruie of strength evoluii<strong>on</strong> duFlng cur+tIB,<br />

cycle under c<strong>on</strong>diti<strong>on</strong>s of comparativeQ-lqw<br />

temperature, (+I 2" C) .<br />

TIE -s%r%nitti"measured at various curing cycles,<br />

under the average temperature (t12OC) analogous<br />

to which during c<strong>on</strong>structi<strong>on</strong> period (from May to<br />

September) at fields In the permafroat regi<strong>on</strong> of<br />

the Plateau, we listed in table IT<br />

r<br />

I<br />

i<br />

I - I .A :-.<br />

WI.-I<br />

and it is far Prom that the,atrength i8 proporti<strong>on</strong>al<br />

to the lime c<strong>on</strong>tent added-the more the<br />

strength increases, the more the lime c<strong>on</strong>tent<br />

has been lldded.<br />

temperature which h'aa been mde to fluctuate<br />

between positives <strong>on</strong>d negatives alternately in<br />

accordance with that the negative temperatures<br />

often occurred at night in July und August of<br />

the warm seas<strong>on</strong>. The results of the tests me<br />

listed in table 1x1 md.table IV respectively.<br />

-i-<br />

I<br />

I<br />

!<br />

!<br />

I m I l.I 1 1.87 2.01<br />

It is seen from table 11, both the early strength<br />

of lime stabilized debris soil and that of the<br />

clayey loam &we higher than those of other soils<br />

stabilized with lime. And the early strength of<br />

the lime stabilisecl sandy loam seems quite low.<br />

The key to the develping of the strength for<br />

lime stabiliaed soil structures lies in the<br />

chemical acti<strong>on</strong>s of the i<strong>on</strong> exchange and carb<strong>on</strong>ati<strong>on</strong><br />

inside of them, which w e direotly in<br />

fluenced by the temperature. The chemicnl acti<strong>on</strong><br />

develops more rapidly aa the temperature is<br />

going up higher ana higher, and corresp<strong>on</strong>dingly,<br />

the strength of the lime stabilized so11 will<br />

increase quicker md quicker, but it would not<br />

increase any more, as the temperature has fallen<br />

below 0' c ana the chemical acti<strong>on</strong> ceased at all.<br />

The Strength of any lime stabilized soils would<br />

increase with the days during curing. It is in<br />

general, the atrength increasing is oomparatively<br />

quicker,uithin the curing period of 28<br />

days, and it would slow down later <strong>on</strong> moreover,<br />

the strength of the stabilized soils which nre<br />

dike in kind is closely correlated with the<br />

o<strong>on</strong>tent of lime which has been added to the Soil<br />

in percentage by weight, but the highest strength<br />

would be obtained at the optimum c<strong>on</strong>tent <strong>on</strong>ly,<br />

It is 390x1 from table I11 and IV, the strength<br />

of lime stabili5afi<strong>on</strong> structure would evolve<br />

thoroughly too, while the sample was cured in<br />

positive and negative temperatures alternately.<br />

The atrength inareasea with days of curing, but<br />

it ia somewhat lower than what is cured in positive<br />

temperature with the ame curing days. For<br />

example, the strength of the stabilized sandy<br />

loam is 20-70$ lover, and that of stabilized<br />

gravel-soil is about 1 Q$ lower €10wever, they<br />

are all able to fulfill the quality requirementa<br />

of design.<br />

The Preezina Resistance md Hydrostability of<br />

Lime Stabilizati<strong>on</strong> Structure<br />

Preeing. nes!E%!-!!<br />

For verifying the evoluti<strong>on</strong> of strength of stabilised<br />

aoil atructure dter it hns been both<br />

frozen up and thawed out at -12"~"- -15'~ for<br />

16 hours, under dry, moist and saturated c<strong>on</strong>diti<strong>on</strong>s<br />

separately. The evoluti<strong>on</strong> of strength of<br />

them after they underwent freeze-thaw processing<br />

6 times again $a ahown in table V.<br />

Moreover, both samples that of unsaturoted a d<br />

that of saturated after (whiah had) thawed mere<br />

frozen at -5°C" -2O'C for 12 houra und thawed<br />

ut +2O'c for 12 hours and meaaured their strength<br />

at they were fromn-thuWed f,6,9,12 and 15 times<br />

over again, respectively. The evoluti<strong>on</strong> in<br />

1512

have a c<strong>on</strong>siderable drop In early<br />

strength after freezing-proof agent<br />

(Mgcl2) was added into the mixing of<br />

them, therefore, we wouldn't recommend<br />

to add the freezing-proof agent now,<br />

although the adding 00 the agent had led<br />

to an effect to slow down the drop in<br />

strength .<br />

""-""""~<br />

strength which varied with times f'rozen and<br />

thawed over again is shown in figure3 sa<br />

following.<br />

It is seen in table V that the drop in strength<br />

of the stabilized soils has a natural relati<strong>on</strong><br />

with the times of frezen-thawed processing over.<br />

The frezen-thawed r'esistance of lime<br />

stabilized soils basically drops gradually<br />

with the increasing of times<br />

frozen-thawed. The Strength drops<br />

abruptly la the beginning nt frozenthawed<br />

3 times over, about 10--20$, and<br />

then drop OH down later gradually, The<br />

totdl mount of the dropo in strength at<br />

frozen-thawed 15 times over is about 7046.<br />

It is See2 ulso from the graphs that the<br />

drop in strength will still go <strong>on</strong>, but<br />

decreases in amount more and more small<br />

slowly<br />

The drop in strength of the test roada<br />

Seem3 to be <strong>on</strong> the fast Side. For exaaple,<br />

the atraia of deflecti<strong>on</strong> "cup" of a<br />

double course lime stabilizea pavement<br />

measured at Tsoumall River in 1976 was<br />

0.31mm, and it was 0.46mm measured again<br />

at the same site in 1981, after the road<br />

had been opened to traffic for five<br />

years. In fact, the strength had decreased<br />

about 48$, but It was still within<br />

the allowance for working.<br />

It is seen from tests d<strong>on</strong>e, the freezing<br />

resistance of lime stabilized gravelly<br />

soil is quite better, that of the sandy<br />

loam is the next best and that of the<br />

clayey loam is relatively poor. But,<br />

since the early strength of the lime<br />

stabilized playey lorn is quite higher,<br />

~lso, the strength, after the stabilized<br />

Soils have underg<strong>on</strong>e, frozen-thawea<br />

processing, is higher than that of stabilized<br />

sandy loam too, and <strong>on</strong> the other<br />

hand, the drop in strength, after the<br />

soils have been froierl-thawed 6 times<br />

over, is undistinguished, therefor, the<br />

lime stabilized clayey loam, to be sum,<br />

is z kind of material superior for us8<br />

than the lime stabilized sandy loam, as<br />

it is judged by the strength that which<br />

is after frozen-thawed processing.<br />

Since the lime stabilizati<strong>on</strong> structures<br />

1.60 .i<br />

1.50 - ',<br />

1.40 .<br />

'<br />

""<br />

1.30 -<br />

, """"""<br />

I I<br />

.O S 6 9 12 15 n<br />

Pig. I<br />

(4) The strength of the stabilized soils<br />

ceased from developing whlle,the soils<br />

are being frozen up. The freezing resistance<br />

of the stabilized soils axe in<br />

propsrti<strong>on</strong> to their curing days directly,<br />

and the l<strong>on</strong>ger they have been cured, the<br />

strenger the strength developed.<br />

Hydrostableness<br />

The hydrostableness of the lime stabilizati<strong>on</strong><br />

struc ture is expressed by the ratio between the<br />

strength of unsaturated soil sample at certain<br />

Curing period specified and that of the same<br />

curing period. The ratio of various soils which<br />

is 30 called as "hydrostublenesa index, Puis listed<br />

in table 11, It is seen Prom table I1 that the<br />

lime stabilized soil structure with higher<br />

strength is more hydros table.<br />

Problems <strong>on</strong> Swell of Lime Stabilizati<strong>on</strong><br />

It is indicated by swell tests: the swell value<br />

in volume of the frozen lime stabilizati<strong>on</strong><br />

Increases with the increasing of water c<strong>on</strong>tent<br />

in sofl. The swell factors In volume for some<br />

1513

soils, while their water c<strong>on</strong>tents a ~ e 1--& more<br />

than the optimum moisture c<strong>on</strong>tents respectively,<br />

are as following:<br />

The swell factor for silty heavy clayey loam is<br />

0.7--1 .Os, that for fine sandy loam 1s 0.4--0.7$<br />

and that for lime stabilized gravelly soil is<br />

0.1--0.2$.<br />

In the light of above experimental data, it is<br />

clew, the Influence of the swell <strong>on</strong> the stabi;<br />

lity of the whole pavement structure Is very<br />

light and may be negligible, even the swell is at<br />

their utmost limits.<br />

Some Aspects <strong>on</strong> the Applicati<strong>on</strong> of Llme Stabilizati<strong>on</strong><br />

us a kind of Paving Materials in <strong>Permafrost</strong><br />

Regi<strong>on</strong> of Qingeang Highway<br />

(1 1 The lime stabilizati<strong>on</strong> not <strong>on</strong>ly is a<br />

kind of materials to be able used for<br />

the base course and mat base of asphalt<br />

pavement, which is obtainable al<strong>on</strong>g the<br />

Highway everywhers in site, and it is an<br />

ideal matexial quite better in applicati<strong>on</strong><br />

comparatively.<br />

It is shown by indices of various lime<br />

stabilizati<strong>on</strong> <strong>on</strong> their strength, free%<br />

ing resistance, hydrostableness and<br />

swell, that the lime stabilized gravelly<br />

soil and debris soil we more effective<br />

than other soils in applicati<strong>on</strong>. But, 88<br />

the silty clayey loam posses arelatively<br />

higher early strength which would be a<br />

favourable factor to put it in use fully<br />

by mixing certain amount of gravel<br />

(debris) or sandy gravel to improve ifr<br />

freezing resistance. The suitable amount<br />

of aggregates $0 be added in mixing is<br />

about 4046 in volume.<br />

To plan a rati<strong>on</strong>al dispositi<strong>on</strong> of time<br />

limit for c<strong>on</strong>structi<strong>on</strong> and its progress<br />

chart 2s a key link to quarantee fully<br />

developing of lime stabilizati<strong>on</strong>'s<br />

strength. By meteorological observatk<strong>on</strong>s<br />

and that of earth temperature within a<br />

depth of 0--20crn, it 1s seen that the<br />

ground temperature within the depth of<br />

5--20crn remain8 at positives during the<br />

middle of May to that of October, even<br />

though, while negative temperatures may<br />

occure at cight frequently. Therefore,<br />

it is suitable to fix up the time limit<br />

of c<strong>on</strong>structi<strong>on</strong> in a period, from the<br />

beginning of May to that of September,<br />

By the teats in laborutories and the investigati<strong>on</strong>s<br />

up<strong>on</strong> the lime stabilized soil base course<br />

in traffic operati<strong>on</strong> <strong>on</strong> the test roads 50km in<br />

length, we have seen that the stabilized soil<br />

structures In permafrost regi<strong>on</strong> <strong>on</strong> the Platenu<br />

were plenty of c<strong>on</strong>solidati<strong>on</strong> und able to solidify<br />

out into block.<br />

The pavement, paved with stabilized soil atructures,<br />

as a whole .was quite better in freezing<br />

resistance and in hydrostablenesa, therefore,<br />

ita atrengtb was able to satisfy the quality<br />

requirements in design. It is paved by practice<br />

now that the soil atabilizati<strong>on</strong> is quite feasible<br />

to apply <strong>on</strong> highway engineering in permafrost<br />

regi<strong>on</strong> <strong>on</strong> lateau. This is the c<strong>on</strong>clusi<strong>on</strong> of the<br />

author -<br />

REFERENCES<br />

hnzhou Institute of Glaciology and<br />

Geocryology, Chinese Academy of<br />

Sciences, 1978, <strong>Permafrost</strong> Soil al<strong>on</strong>g<br />

the Qingz<strong>on</strong>g Highway.<br />

Ministry of Communicati<strong>on</strong>s of R.P.C. 1982,<br />

Specifcati<strong>on</strong>s for c<strong>on</strong>structi<strong>on</strong> of<br />

lime-soil base course of highway<br />

pavement.<br />

1514

INVESTIGATION AND TR~ATMENT FOR SLOPE-SLIDING<br />

OF RAILWAY CUTTING IN PERMAFROST AREA<br />

Wan& Wfmbao<br />

Qiqihar Railway Rearch Institute, Harbin Railway Administrati<strong>on</strong> Bureau<br />

SYNOPSIS The slope-sliding is a special type of railway roadbed damages in the permafrost<br />

area of the Great Xingan Mountain. Through the explorati<strong>on</strong> and engineering treatment for the sliding<br />

damages happened at the site of 440 kilometers of Yalin rail line, this report try to analyse in<br />

detail the processes of forming and developing o f the damage, and discuss its features and reas<strong>on</strong>s.<br />

The propping-seepage ditch of side slope, the block-seepage ditch and drain-seepage ditch compose a<br />

complete system and cure the damage permanently. This system possesses the functi<strong>on</strong>s of dredging<br />

skin-layer water, improving the drain-c<strong>on</strong>solidati<strong>on</strong> of soil, increasing soil strength and directly<br />

propping the soil-body of slope, In additi<strong>on</strong>, it also has the acti<strong>on</strong> of frost-drain-c<strong>on</strong>-solidati<strong>on</strong>.<br />

The engineering practice shows that the propping-seepage ditch <strong>on</strong> side slope is the key measure of<br />

treating damage, and its thermal effect does not influence the stability of the structure itself,<br />

therefore the method may be used to treat damages in roadbed engineering in permafrost areas.<br />

DESCRIPTION OF THE DAMAGE<br />

The damage secti<strong>on</strong> of railway line. from 440K+<br />

OOOM to 400M, is a road cutting, its Left is<br />

river valley and right is mountain slope. This<br />

line runs basically from south to north. With<br />

the culvert.as the boundary, located at the site<br />

of 440Kt175M, the whole damage secti<strong>on</strong> can be<br />

divided into two subsecti<strong>on</strong>s which are shown in<br />

Fig. 1 *<br />

The first secti<strong>on</strong> is located from 440Kt010M to<br />

llOM, and it is the old damage part. The soilmade<br />

cutting at the right side is 5 meters high.<br />

The gradient of the side slope is lower than<br />

1:1.75. At the bottom of the slope within the<br />

secti<strong>on</strong> of 060 M to 110 M,there is a st<strong>on</strong>ecemented<br />

retaining wall; and at the top of the<br />

slope, there is a gutter.<br />

Since 1965, two times of grave slope-sliding<br />

had occurred in August of 1970 and September of<br />

1972 respectively. About <strong>on</strong>e hundred cubic<br />

meters of soil collapsed down, which destroyed<br />

the retaining wall, washed it to roadbed and<br />

buried rails. In treating, we extended the re,-<br />

taining wall to the site of 010 M. Besides, <strong>on</strong><br />

the surface of slope, we made the chip-st<strong>on</strong>e<br />

.checks and the sod bank protecti<strong>on</strong>. At the<br />

locati<strong>on</strong> of 055 M , we also made a dry-laid chipst<strong>on</strong>e<br />

handing ditch for draining the water of<br />

gutter. But after that the slope still c<strong>on</strong>sider-<br />

ably deformed. In autumn of 1980, the retaining<br />

wall in the secti<strong>on</strong> from 010 M to 030 M was collapsed.<br />

The sec<strong>on</strong>d secti<strong>on</strong> is located from 440K+240M to<br />

340 M, and it is the late damage part. The<br />

soil-made cutting at the right side is 6 to 8<br />

Fig.1 Topographic Map of the Slope-sliding in a Cutting<br />

at the Site of Yalin Railroad 440K<br />

1515

meters high, and the gradient of which is about<br />

1:1.70. Al<strong>on</strong>g the right side of lateral ditch<br />

from 240 M to 290 M, there is originally a dry<br />

laid chip-st<strong>on</strong>e platform which is 2.5 meters<br />

wide, At the bottom of side slope, there is a<br />

dry laid chip-st<strong>on</strong>e bank protecti<strong>on</strong> with a<br />

height of 1.5 meters, and the upper of which i s<br />

the bank protecti<strong>on</strong> of chip-st<strong>on</strong>e checks. Al<strong>on</strong>g<br />

the right side of slope bottom, from 229 M to<br />

345 M , there is a trapezoidal and dry laid chipst<strong>on</strong>e<br />

buttress-bottom-guard.with a height of<br />

1.5 meters, At the top of cutting, there are<br />

cemented chip-st<strong>on</strong>e gutters, which are apart<br />

from the top of cutting over 8 meters. Most of<br />

the gutters are leaking because of the freezingthawing<br />

acti<strong>on</strong>.<br />

In this secti<strong>on</strong>, there was no deformati<strong>on</strong> originally,<br />

however <strong>on</strong> September 21 of 1980, as the<br />

result of the c<strong>on</strong>tinuous rain, the glide deformati<strong>on</strong><br />

simultaneously initiated <strong>on</strong> the slope<br />

surface of both the sites of 250 M and 275 M.<br />

It seemed being mudflow at the site of 250 M,<br />

and the right side rails were buried. At the<br />

latter site, it was the plastic sliding, and<br />

located <strong>on</strong> the platform outside of the lateral<br />

ditch.<br />

At the site of 250 M, the slide-body was a l<strong>on</strong>g<br />

belt in shape, with 17 meters l<strong>on</strong>g and about<br />

80 cubic meters in volume, The upper of which<br />

was wider, with 8 meters in average width, and<br />

the fr<strong>on</strong>t edge of which showed like a t<strong>on</strong>gue in<br />

soft-plastic and flowing state. At the upper<br />

edge of the slide-body, there was a steep wall<br />

with 1.3 meters high and water-seepage in many<br />

places. Its bottom was frozen, The thickness<br />

of the middle part of the slide-body is about<br />

1.5 meters, and the gradient of its surface is<br />

1:4. A birch <strong>on</strong> it had been moved about 7<br />

meters. The maximum movement of the body may<br />

be up to 10 m.<br />

At the site of 275 M, the slide-body was moundshaped<br />

about 2 meters high and 10 meters wide.<br />

Its total volume was about'70 cubic meters. The<br />

original dry laid chip-st<strong>on</strong>e bank protecti<strong>on</strong> was<br />

destroyed. The gradient of upper slide-body was<br />

about 1:25. There were crevices in the slidebody,<br />

from which water was leaked out, making<br />

the ground very moist. The crevices at the top<br />

of cutting was c<strong>on</strong>tinuously distributed from<br />

224 M to 340 M.<br />

After 1981, at the site of 300 m, a new slopesliding<br />

was formed, At the same time, the slopesliding<br />

at the site of 250 M had beed developing.<br />

The arc wall at the top of the sliding was c<strong>on</strong>tinuously<br />

nibbled and moved upward. The distance<br />

between the wall and gutter was reduced<br />

from 4 to 2.4 meters.<br />

On August 18 of 1982, at the site of 300 M, a<br />

sliding o f side slope suddenly happened. The<br />

developing process of the sliding was seen as<br />

follows.<br />

In 12:30 of that afterno<strong>on</strong>, a few of laid st<strong>on</strong>es<br />

<strong>on</strong> bank protecti<strong>on</strong> rolled down, which indicated<br />

that soil-body of the siding was beginning to<br />

creep and slid downward. J3u.t this phenomen<strong>on</strong> was<br />

not noted. In 13 o'clock, in the middle-lower<br />

part of the sliding, which was a little higher<br />

than the dry laid chip-st<strong>on</strong>e buttress, the slope<br />

surface was raising. At the same time, mudflow<br />

was forming at the water-seepage place <strong>on</strong> the<br />

upper part of the sliding, and finally piled up<br />

<strong>on</strong> the middle platform. Following this, the<br />

soil-body at the middle part of the sliding<br />

obviously moved down, and its speed gradually<br />

increased. The whole slide-body pushed and<br />

pressed the lower slide slope and made it c<strong>on</strong>tinuously<br />

raised and tumbled until the side<br />

slope was destroyed. After the slide-body<br />

(about 60 m) being separated from the slope surface,it<br />

rapidly advanced down with a largest<br />

speed of 5 meters per minute. Because of the<br />

obstructi<strong>on</strong> of the dry laid chip-st<strong>on</strong>e buttress,<br />

it was turned to south al<strong>on</strong>g the railway line,<br />

and finally pi.led up <strong>on</strong> the platform which is<br />

outside of the lateral ditch. Its fr<strong>on</strong>t edge<br />

moved about 10 meters, and the gradient of its<br />

surface was 1:5. If there was no obstructi<strong>on</strong><br />

of the chip-st<strong>on</strong>e buttress, it would had crossed<br />

surely the lateral ditch and buried the rails.<br />

Besides, the mud-flow directly rushed down to ,<br />

the lateral ditch and filled it up.<br />

The slide-body was 7 to 8 meters wide, 11 to 12<br />

meters l<strong>on</strong>g, and its average thickness was <strong>on</strong>e<br />

meter. It looked like a inverse trapezoid. The<br />

wall of the sliding was <strong>on</strong>e meter high and 15<br />

meters wide, where the places of water-seepage<br />

was a wedge-like and raised upward. Because of<br />

the lateral press, in the middle part of the<br />

slope surface, a soil-ridge, which was less<br />

than <strong>on</strong>e meter in height, was raised and buried<br />

a temperature observati<strong>on</strong> hole. By inserting a<br />

trunck in the sliding we obtained that the depth<br />

<strong>on</strong> its upper edge was 0.8 meters, which was the<br />

average thawed depth of the sliding. On the<br />

next day, we measured the form of the secti<strong>on</strong><br />

which was <strong>on</strong> the axis of the slide-body, and<br />

found that its surface was basically flat with<br />

a gradient of 1:4.2. The gradient of the sliding<br />

face below the sliding-wall was 1:2.75<br />

(Fig.2). The whole process of the sliding<br />

lasted half hour, followed by the upper mud-flow<br />

which also lasted about half hour.<br />

ENGINEERIN'G GEOLOGICAL CONDITIONS<br />

The left slope surface of the cutting is covered<br />

with broken st<strong>on</strong>e of serious weathering, the<br />

Outcrop of which extends down to the mountain<br />

from the left lateral ditch to the right in the<br />

slope of 1:2. The right side of the cutting is<br />

the soil sediments, which can be chiefly divided<br />

into three layers. The surficial layer is composed<br />

of yellowish-brown to greyish- brown sandy<br />

loam with 15-30% of crushed st<strong>on</strong>e and gravel.<br />

Its water c<strong>on</strong>tent is usually Less than 20%,<strong>on</strong>ly<br />

<strong>on</strong> the skin and the gutters used for waterseepage,<br />

the water c<strong>on</strong>tent is up to 25% to 30%.<br />

The thickness of this layer is generally less<br />

than 2 meters. The bottom of the layer tends<br />

to the railway line. In the sec<strong>on</strong>d layer, the<br />

number of sandy-loam minilayers is gradually<br />

reduced, but minilayers of sand and gravel are<br />

increased. Its thickness is about 3 meters.<br />

The layer under the roadbed, the third layer,is<br />

chiefly composed of the interlayers and lensed<br />

of sand and gravel. The maximum gravel diameter<br />

is about 40 millimeters. The total thickness<br />

of the three layers is over 10 meters, and all<br />

the layers tend to railway line with the grad-<br />

1516

-"<br />

.-... , ..1980.11.17<br />

Original S U ~ ~ ~ C E -""" 1981.7.24<br />

-emalms1 table "_ 1981.9.11<br />

-4.Y-Locati<strong>on</strong> of sliding - - 1982.4.15<br />

-1982.8.1F<br />

Fig.2<br />

Process of Sliding <strong>on</strong> Two Slopes<br />

ient of 1:lO to 1:20. The ground is frozen<br />

except the layer at the bottom of the slope.<br />

The sandy loam is composed of 38% of gravel,<br />

35X of sand, 25% of silt and 2% of clay. Thus.<br />

it is classified as the silty sand with gravels.<br />

The plastic limit is 18%; the liquid limit is<br />

25X; the plasticity index is 7. It is from<br />

field investigati<strong>on</strong> deduced that the stratum<br />

here may bel<strong>on</strong>g to the ice-water deposit.<br />

The shear strength tests <strong>on</strong> the remolded silty<br />

sand were c<strong>on</strong>ducted, The result show that the<br />

angle of fricti<strong>on</strong>,@ , islless than 10 degrees<br />

and cohesi<strong>on</strong> c=O.1 kg/cm when water c<strong>on</strong>tent<br />

W=20%, and they rapidly decrease with water<br />

c<strong>on</strong>tent increasing.<br />

In the warm seas<strong>on</strong>, water flows through gutters,<br />

Because of the freezing-thawing effect, 'many<br />

places in the gutters were deformed and broken,<br />

where water was leaked out from the slope surface.<br />

The locati<strong>on</strong>s of water-seepage were usually<br />

lower than the top of the cutting by 0.6<br />

to 1,0 meters. This was the main water source<br />

of causing slope being moist and slope-sliding.<br />

The water in the soil also comes from rainfall and<br />

thawed snow.<br />

FEATURES AND CAUSES OF THE SLOPE-SLIDING<br />

Through observati<strong>on</strong> and survey for two years<br />

and <strong>on</strong>e time of witness, it is found that the<br />

sliding deformati<strong>on</strong> of side slope has the following<br />

features and regularities:<br />

1. The deformati<strong>on</strong> of slope surface occurs in<br />

the whole warm-seas<strong>on</strong> from spring-thawing to<br />

freezing, and the process of the deforming is<br />

successive, which is showed in Fig.3.<br />

Sprinp lhawlna<br />

Iwtrtace<br />

The damage secti<strong>on</strong> is located in the central<br />

part of permafrost. According to the data obtained<br />

from the Mangui Observati<strong>on</strong> Stati<strong>on</strong>, the<br />

annual mean air temperature is -4.7'C, the annual<br />

average thawing and freezing indexes are<br />

1955 and 3600 'C-day, respectively.<br />

The depth of permafrost table is between 1.7<br />

and 2.5 meters at the top of the cutting with<br />

vegetati<strong>on</strong>, greater than 2.7 meters <strong>on</strong> the slope<br />

surface without vegetati<strong>on</strong>, and greater than<br />

6.0 meters under the right lateral ditch and <strong>on</strong><br />

the left side of the cutting.<br />

Fig.3 Schematic Drawing Showing the<br />

Development of a Slope-sliding<br />

1517

During spring-thawing, al<strong>on</strong>g with the gradually<br />

thawing of snow and frozen soil, slope deformati<strong>on</strong><br />

is chiefly the creep of surficial layer,<br />

which occurs everywhere and frequently. Simultaneously,<br />

crevices form at the top and <strong>on</strong> the<br />

slope surface of the cutting, In the warm-seas<strong>on</strong>,<br />

the layer of thawed soil gradually becomes thick,<br />

and the phreatic water and the leaking water<br />

from the gutter obviously act <strong>on</strong> the slope, so<br />

that the deformati<strong>on</strong> becomes a small scale of<br />

mud-flow, which will form steep ridges at the<br />

places of water seepage <strong>on</strong> the cutting top edge,<br />

and c<strong>on</strong>tinuously nibble and advance upward. Thus<br />

the area of the damage will be enlarged gradually.<br />

After enlarging a certain scale, and caused<br />

by a l<strong>on</strong>g time raining, the c<strong>on</strong>siderable scale's<br />

sliding of side slope may be happened above the<br />

freezing-thawing interface. In small water c<strong>on</strong>tent,<br />

the sliding deformati<strong>on</strong> may be showed as<br />

a hard-plastic stack sliding plastic sliding or<br />

soft-plastic mud-flow, respectively, which are<br />

all happened in the shallow layer and seas<strong>on</strong>ally.<br />

2. The deforming firstly occurs at the crevices<br />

of the cutting top. Since the thawed snow and<br />

surface water permeate into ground, the partial<br />

sliding deformati<strong>on</strong> <strong>on</strong> the slope surface will be<br />

happened. When the platform or the water accumulati<strong>on</strong><br />

area are formed in the upper side slope,<br />

surface water will gradually permeate into the<br />

lower slope surface,which make the strength of<br />

the slope greatly reduced and can not bear its<br />

self-weight, thus the sliding deformati<strong>on</strong> will<br />

be happened <strong>on</strong> the slope surface in a large<br />

scale.<br />

3. The pattern of slope sliding is usually as<br />

follows. On the upper, there is an arc steep<br />

precipice or a slide-wall with <strong>on</strong>e meter high;<br />

below that, there are water seepage exposures;<br />

in the middle part of slope surface, it is<br />

steps-like because of the breaking and separatingofthe<br />

soil-body; and in the lower part,<br />

there is an obvious t<strong>on</strong>gue-like fr<strong>on</strong>tier, <strong>on</strong><br />

which there exist arc wrinkles or crackles.<br />

4. The sliding face is from the slide-wall or<br />

crevices <strong>on</strong> the top of the cutting edge to the<br />

lower part of the slope which is higher than<br />

the platform about 0.5 to 1.0 meters. Its middle<br />

part is c<strong>on</strong>trolled by the freezing-thawing<br />

interface, but located above it about 1.0 to<br />

2.0 meters.<br />

The side slope is mainly composed of silty sand<br />

with gravel, which possesses higher permeability<br />

and maintenance of water. It will have<br />

higher strength when the water c<strong>on</strong>tent is lower,<br />

and the strength will be greatly reduced when it<br />

is rich of water. The existence of this kind of<br />

soil is the internal cause of the slope-sliding.<br />

The thawed snow, the shallow phreatic water, and<br />

especially the leaking water of gutters are the<br />

mainly external causes for the sliding.<br />

Furthermore, both the existence of permafrost<br />

and the freezing-thawing circles of active layer<br />

and its effect <strong>on</strong> soil structure and strength<br />

make the internal and external causes menti<strong>on</strong>ed<br />

above interacted. This brings about .the accumulati<strong>on</strong><br />

of the slope deformafi<strong>on</strong> and affects the<br />

integrity and stability of the soil-body of the<br />

slope. Thus, in rain-seas<strong>on</strong>, a certain scale of<br />

sliding <strong>on</strong> the slope may be caused and leads to<br />

a damage.<br />

TREATMENT MEASURES<br />

The guiding principles for preventi<strong>on</strong> and cure<br />

of the slope sliding are: c<strong>on</strong>trolling and dredging<br />

the surface water and the phreatic water of<br />

surficial layer, increasing the degree of drainc<strong>on</strong>solidati<strong>on</strong><br />

and strength of soi1,and c<strong>on</strong>structing<br />

supporting structures. The measure, which<br />

has all the functi<strong>on</strong>s menti<strong>on</strong>ed above, is to<br />

make propping-seepage ditches <strong>on</strong> the side slope<br />

surface,, which.has, been used in the treatment<br />

of the sliding discusses here.<br />

The effects of the propping-seepage ditch in<br />

treating the slope-sliding in permafrost area<br />

are :<br />

1. It directly blocks and dredges the phreatic<br />

water of surficial layer, eliminates the erosi<strong>on</strong><br />

acti<strong>on</strong> of water to slope surface and reduces the<br />

water c<strong>on</strong>tent of surficial layer of the slope.<br />

2. It increases the degree of drain-c<strong>on</strong>solidati<strong>on</strong><br />

and the strength of soil of the slope.<br />

3. It directly,props the soil-body of slope surface,<br />

thus increases its stability and protects<br />

the soil-body from sliding down.<br />

4. It partly changes the temperature regime of<br />

permafrost and the freezing-thawing interface,<br />

which is favourable to the drain-c<strong>on</strong>solidati<strong>on</strong><br />

of the soil-body of slope surface.<br />

The propping-seepage ditch at the side slope,<br />

the block-seepage ditch <strong>on</strong> the top of cutting<br />

and other drain-seepage ditchs, form a perfect<br />

dra i n system, which plays a comprehensive effec<br />

t of eliminating the damage of slope sliding.<br />

TRE 1A TMENT EFFECTS<br />

The treating engineering has experienced for<br />

four rain-seas<strong>on</strong>s, which proved that the draining<br />

effect is good. The deformati<strong>on</strong> and sliding of<br />

slope surface have been eliminated. Therefore,<br />

it is c<strong>on</strong>sidered that the applicati<strong>on</strong> of the<br />

propping-seepage ditch to the roadbed engineering<br />

in permafrost area is successful.<br />

The observati<strong>on</strong> o f ground temperature indicates<br />

that the influence of propping-seepage ditch <strong>on</strong><br />

permafrost is not obvious. It <strong>on</strong>ly limitedly<br />

increasse the thickness of active layer of the<br />

upper slope, which is favourable t o the drainc<strong>on</strong>solidati<strong>on</strong><br />

of the soil. It also indicates<br />

that although the propping-seepage ditch is not<br />

located in permafrost layer, it still works well<br />

and is not destroyed by freezing-thawing effect.<br />

CONCLUSIONS<br />

(i) Using the original measure of dry laid<br />

chip-st<strong>on</strong>e bank protecti<strong>on</strong> is not effective,<br />

the reas<strong>on</strong> is that it is a king<br />

1518

of protecti<strong>on</strong>al measure for preventing<br />

the slope surface from washing and<br />

weathering peeling, and can not bear the<br />

frost heave force and pressure of soil,<br />

However, although the retaining wall and<br />

the dry laid chip-st<strong>on</strong>e buttress are the<br />

passive measures, they still can c<strong>on</strong>trol<br />

the area of the damage. The proppingseepage<br />

ditch, which has the effects of<br />

both drain-c<strong>on</strong>solidati<strong>on</strong> and proppingprotecti<strong>on</strong>,<br />

is a good measure for treating<br />

the damage of slope-sliding,,<br />

(ii) In the central part of permafrost area,<br />

the propping-seepage ditch of side slope,<br />

<strong>on</strong>ly partly changes the planar state of<br />

temperature field under slope surface,<br />

and its effects of drain-c<strong>on</strong>solidati<strong>on</strong><br />

and propping-protecti<strong>on</strong> are identical<br />

to those in n<strong>on</strong>-frost area.<br />

(iii) The sliding face is from the place of<br />

water-seepage under the slide-wall to<br />

the slope surface which is higher than<br />

the platform, and the middle part of<br />

which is a gentle curved surface, Its<br />

gradient of upper part is close to 30<br />

degrees at the upper part, about 12 to<br />

15 degrees at the lower part, and 18 to ,<br />

20 degrees at the middle par,t.<br />

(iv) The sliding face is not the freezingthawing<br />

interface, but about 0.8 meters<br />

higher than the interface,and it is not<br />

a smooth plane, but a layer or a band<br />

with the thickness of 0.1 to 0.5 meters.<br />

(V) According to statistics, the sliding<br />

deformati<strong>on</strong> usually occurs after a c<strong>on</strong>tinuous<br />

rain about 20 days to <strong>on</strong>e m<strong>on</strong>th.<br />

(vi) Because of the thermal effect of the<br />

propping-seepage ditch, its foundati<strong>on</strong><br />

can not be set in permafrost layer.Thus,<br />

the foundati<strong>on</strong> must be designed big and<br />

save enough based <strong>on</strong> the calculati<strong>on</strong>s<br />

<strong>on</strong> its mechanical stability.<br />

ACKNOWLEDGEMENT<br />

The author sincerely thanks Messrs Liu Shenjia,<br />

Xie Ruitang and Li Yingwu, who were involved in<br />

this work.<br />

1519

MODEL TEST TO DETERMINE THAWING DEPTH OF<br />

EMBANKMENT IN PERMAFROST REGION<br />

Ye, Bayou, T<strong>on</strong>g, Zhiquan, Lou, Anjin and Shang, Jih<strong>on</strong>g<br />

Northwest Institute, China Academy of Railway Sciences<br />

SYNOPSIS Model test is an indoor method used for simulating the temperature field in<br />

engineering structure in permafrost regi<strong>on</strong>. C<strong>on</strong>traeted with the engineering<br />

situ the temperature<br />

dietributi<strong>on</strong> is almoat the same with each other. Thus, the calculating formulas of tho thawing<br />

depth obtained from the model teat may be used for the practical engineerings.<br />

MODEL DESCRIPTION<br />

It is bell known that there exists the interacti<strong>on</strong><br />

relati<strong>on</strong>ship (Ding Deweng, 1979) between<br />

time scale factor (&) and geometric factor<br />

(C,) $f both the model and actual object namely<br />

Q= CL if the model medium teated ia the same<br />

as the actual <strong>on</strong>e. That is, under this c<strong>on</strong>diti<strong>on</strong>,<br />

the model temperature is the sane aa that<br />

of the actual object, whereas the time Bcale<br />

dependa <strong>on</strong> the geometric scale. However, if<br />

the scale Size of model is too small, the time<br />

scale is smaller, and then the changing amplitude<br />

of boundary temperature of model is much<br />

greater in a ahort time ao it ia not easy to be<br />

c<strong>on</strong>trolled. The variati<strong>on</strong> law of model temperature<br />

field is also difficultly measured.<br />

When the model scale aize is too big, the teat<br />

cycle is l<strong>on</strong>g enough and the evaporati<strong>on</strong> of<br />

water in model so large that it is difficultly<br />

c<strong>on</strong>trolled. According to the practice in<br />

the COOL room, if time scale (3,between model<br />

and the engineering in aitu is 1:240, the geo-<br />

metric scale CL is 1:lC.49. So the time scale<br />

ie <strong>on</strong>e hour in model teat equabto ten days in<br />

situ.<br />

The model box, 2.2~1.41~2.0 m in size, can be<br />

directly assembled in the cool room. It is an<br />

insulated and sealed model box and can be devided<br />

into three parts, i.e. the temperature<br />

c<strong>on</strong>trolling chamber of bottom boundary of model,<br />

the ternFerature c<strong>on</strong>trolling chamber of<br />

top boundary of soil and the model soil chamber.<br />

The height of the soil chamber is 0.71 m<br />

which ie corresp<strong>on</strong>ding to the height of foundati<strong>on</strong><br />

aoil of embahent in aitu. It can meet<br />

.the needs of annual variati<strong>on</strong> depth in situ.<br />

After the eoil chamber is filled with earth<br />

taken from field, the embankment model is built.<br />

The electrical heater is installed in the<br />

top-boundary temperature-c<strong>on</strong>trolling chamber<br />

which is seperated with asbestos boards into<br />

five parts, road awface, aun-facing alope,<br />

shadow slope, berm of the sun-facing slope and<br />

berm of the shadow slope, and covered with rock<br />

wool to prevent warm air from riaing.which<br />

cauaes the surface temperature of emnankment<br />

not eaay to be c<strong>on</strong>trolled (see Fig. 1).<br />

The temperature of boundaries are c<strong>on</strong>trolled<br />

autometically by the temperature-c<strong>on</strong>trolling<br />

Fig.1<br />

Test Equipment for Embankment Model<br />

a. Before Aaaambling<br />

b. After Assembling<br />

units. 1Chermistora are used to measure the<br />

temperature of boundaxlee and the eleczric<br />

heaters ana fans at each boundary are c<strong>on</strong>trolled<br />

by the temperature-c~ntrolling units lor heating<br />

or winding to keep the temperature needed<br />

at each boundary.<br />

The temperatures are measured by the Univeraal<br />

Digetal Measuring Apparatua or L<strong>on</strong>g-Figure<br />

Autometieal Hecorder and Thermocouples.<br />

COIKPARI3ON BETWEEN MODEL TEST AND PRACTICE<br />

In order to prove the accuracy of the test, we<br />

carry out the simulating about the temperature<br />

field variati<strong>on</strong> of DK0+280 secti<strong>on</strong> of testing<br />

subgrade engineering <strong>on</strong> Qinghai-Xizang plateau.<br />

The model embenkment c<strong>on</strong>sists of two parts, <strong>on</strong>e<br />

is the sandy-clay embenkmsnt for aimulating the<br />

engineering in aitu, another is the coarse-grain<br />

aoil embenkment, And 10 cm thick polystyrene<br />

hard foam is placed between them to eliminate<br />

the interacti<strong>on</strong>.<br />

Figure 2 shows the secti<strong>on</strong> type of embankment<br />

1520

. .<br />

Thermal physical parameters for soil of model<br />

are as following:<br />

Fig.2 Embankment Model (IJK0+280, Fe huo<br />

Mt., Qinghai-Xizang Plateau) ,Ym)<br />

(ii) coarse-grain soil embankment<br />

H = 3m<br />

1 ya1430 H i 4 ~+=0.58<br />

and the thawing depth after the model returns<br />

to its original c<strong>on</strong>diti<strong>on</strong>. The embankment<br />

12. 1 r=1400 W04 Qt0.55<br />

temperature field of model after returning is<br />

H = 4m<br />

identical to that in situ. So the deeiga,<br />

I r=14oo w=4 k~0.5~<br />

temperature-c<strong>on</strong>trolling instruments, measuring<br />

I2 1 ~~1450 Wc4 ,+=0.60<br />

secti<strong>on</strong><br />

method and accuracy of model are<br />

DK0+280<br />

dependable.<br />

r=1420 w=5 k~0.70<br />

where r= dry density (kg/m3), W = water c<strong>on</strong>-<br />

, and h+ thermal c<strong>on</strong>ductivity (kcal/m.<br />

ANALYSIS OF TEST RESULTS<br />

hr.aeg. tent ($1 .<br />

It is assumed that the temperature <strong>on</strong> the em-<br />

The embankment tests are carried out with three banlrment aurface is F2 at the sun-facing slope<br />

different heighta, H=2m, H=3m and H=4rm, respec- center, B3 at the ehadow elope and PI at the<br />

tively. The embankment secti<strong>on</strong> is ahoh in<br />

top aurface, According to the observati<strong>on</strong> in<br />

Pig, 3. The sand-clay and coarse-grain moil situ, the temperature <strong>on</strong> the embanhent surface<br />

embanlanenta for eimulating ire tested simu- is about 0.8 times as high as that of both th<br />

taneouely for each height. Two Bifferent water zefo secti<strong>on</strong> and cut surface at the aame secc<strong>on</strong>tents<br />

are seperately simulated for each ti<strong>on</strong>, but the maximum thawing depth at the emheight.<br />

Each teat c<strong>on</strong>tinues for 6 cycles 00 bankment center is the aame as or little larger<br />

there are 36 cyclae totally. During analping than tlqt of them, so that the heat quantity <strong>on</strong><br />

and calculating the thawing depth of the em- both sides of the embankment has the influence<br />

bankments, the relative ice c<strong>on</strong>tent, i, is <strong>on</strong> the thawing depth at ite aenter. The thaw-<br />

0.80 for aand-clay and 0.95; for coarae-grain ing index at the embanhent center be: might<br />

soil.<br />

w<br />

where: 7,- thawing time lasted (tu+.);<br />

p= ( b+H d+d<br />

f ; H - embankment height<br />

; b -<br />

half width of road surface; d- slope angle.<br />

According to the observati<strong>on</strong> data of test, the<br />

thawing deptbof the embankment are shown in<br />

table I and =when the thawing index equa- in<br />

ti<strong>on</strong> (1) is taken. Based <strong>on</strong> them, reLati<strong>on</strong>ship<br />

between thawing index S and thawing depth H is<br />

shown in Fig. 4 and G. Prom them the following<br />

epati<strong>on</strong>a are obtained:<br />

i) sand-clay embankment<br />

Fig.3<br />

Embanlanent Secti<strong>on</strong> for Model (m)<br />

ii)<br />

coarse-grain soil embanhent<br />

Calculati<strong>on</strong> of Thawi De tb at Sub xade<br />

Knter----When the t%iG Proteas &cura<br />

Embankment<br />

in<br />

1521

TABLE I<br />

Thawing Depth of Sand4llay Embankment (m)*<br />

B r 2 0.45 0.75 0.65 0.80 1.02 1.12 1.20 1.30 1.45 1.60 1.73 1.77 1.82 1.86 1.90<br />

pL 0.117 I 0.40 0.55 0.65 0.77 1.00 1.10 1.20 1.28 1.40 1.50'1.60 1.73 1.79 1.85 1.89<br />

H z 3 0.47 0.60 0.65 0.70 0.87 1.07 1.20 1.30 1.40 1.55 1.68 1.78 1.88 1.94 1.98<br />

fit= 0.164 0.50 0.60 0.65 0.75 0.80 1.08 1.23 1.30 1.37 1.53 1.65 1.80 1.90 1.92 1.97 1.99<br />

H=4 0.45 0.55 0.65 0.72 0.85 1.08 1.22 1.30 1.40 1.46 1.57 1.70 1.%86 1.95 1.99 2.04<br />

p2= 0.202 0.47 0.58 0.65 0.80 1.00 1.20 1.30 1.38 1.46 1.54 1.63 1.75 1.89 1.95 1.99 2.03<br />

DK0+280<br />

@% 0.106<br />

10.45 0.55 0.65 0.80 0.97 1.15 1.25 1.40 1.50 1.60 1.70 1.80 1.90 1.95 2.05<br />

* The thawing index is calculated by equati<strong>on</strong> 1.<br />

Fig.4<br />

Relati<strong>on</strong>ehip between Thawing Index S and<br />

Thawing Depth h of Sand-Clay Embardanent<br />

2.8 .i<br />

1.2r /<br />

Big.5<br />

Relatiomhip between Thawing Index S<br />

and Thawing Depth h of Coarse-<br />

Grain Soil Embanlunent<br />

Pig.6<br />

Relatiomhip between Thawing Index S<br />

and Thawing Depth h of UnderatandabLe<br />

Secti<strong>on</strong> (DK0+280) Embadanent<br />

a. Sand-Clay Embankment<br />

b. Coaree-lirain Soil Embankment<br />

1522

TABLE 11<br />

Thawing Depth of Comae-Grain Soil Embanhent (m)*<br />

SXIO~ (deg.nr.1<br />

Embankment<br />

2 '4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72<br />

II li '4<br />

, re'= 0,202<br />

w5<br />

3 5 22 32<br />

3A<br />

33<br />

39 385<br />

335<br />

39<br />

* The thawing index ie calculated by equati<strong>on</strong> 1.<br />

where h is thawing depth st the center of the<br />

embanhmnt (m); hf ie thermal c<strong>on</strong>dilctivity of<br />

the aoil in embankment (koal/m.hr.deg.); QI is<br />

latent heat of thawing of the Boil in embankment<br />

(~1=80rwi). The other aim are the mame<br />

as before.<br />

For the irregular embankment aeati<strong>on</strong> '(see Fig.<br />

2, DK0+280), while calculating the value of<br />

the filling height at the road center is taken<br />

a8 the embaaent height H, and the average of<br />

both slope anglee is taken ae the slope angle,<br />

i.e. +. After dealing with as above<br />

we oan uee equati<strong>on</strong> 2 and 3 to caloulate the<br />

thawi depth of the irregular Bmbanlunent (see<br />

Big. 3.<br />

embanhnent<br />

(2) r=14oo W1=4.0 ~ ~ 0 . 5 5<br />

foundati<strong>on</strong> soil<br />

r=1680 W2=12.0 Cz1.38<br />

From the observati<strong>on</strong> to the teat, the initial<br />

thawing time of foundati<strong>on</strong> soil -ti and accmulated<br />

thawing index F1T1 of the embaulcment<br />

eurfaoe at this time can be detemined. After<br />

this time, the difference os between the thawing<br />

Index at time -C and FlZl le (BlT-PfCI),<br />

Wble 3 ehom the thawing depth of subpade.<br />

at difrerentbe. Following ie obtained from<br />

Big. 7:<br />

,Calculati<strong>on</strong> of Thawing Depth at Submda Center<br />

"" When the Thawing Process Occure in Founda-<br />

ti<strong>on</strong> Soil of Embankment<br />

When the embankment is not very high, the<br />

thawing OOCUTB in the foundati<strong>on</strong> of embankment.<br />

Such ae the coarse-grain soil embankment in<br />

the teet, when Bz2m and H=%, the foundati<strong>on</strong><br />

soil is thawed. The thermal parametera for<br />

coaree-grain soil and foundati<strong>on</strong> eoil are ae<br />

following:<br />

€I= 2m<br />

embanhent<br />

(1) r=14EO W1~3.5 ht=O. F4<br />

foundati<strong>on</strong> soil<br />

y=1680 *W2=12.0 ~:=1.38<br />

embankment<br />

(2) r=1430 W1=4.0 c,+,O 58<br />

foundati<strong>on</strong> soil<br />

y-1680 Wp12.0 To. Th8 other signs are the same as<br />

berore .<br />

In order co determine the minimum filling<br />

height, Hmin, of coarse-grain soil embankment,<br />

in equati<strong>on</strong> 4 the maximum thawing.depth H at<br />

%he embankment center should be Hmin+nn, where<br />

hn represent8 the locally natual depth of permafroert<br />

table. Following is obtained after<br />

omitting the decimal term:

H = 2 K=0.3913 2.07 2.12 2.15 2.22 2.28 2.36 .2.46' .2.57 2.66 2.75 2.80<br />

K=0.4203 2.04 I 2.06 2.12 2.25 2.35 2.50 2.60 2.70 2.75 2.80 2.86<br />

* Thawing depth includes the embankment height.<br />

Caloulati<strong>on</strong> of ThaWiw Depth at Slope Toe of<br />

Embankment<br />

The bexm at elope toe of embmkmenf is aomm<strong>on</strong>ly<br />

filled with sad clay. Following -9 the physical<br />

parmetere fox the berm at the slope tol<br />

<strong>on</strong> the secti<strong>on</strong> of sand-clay embankment:<br />

Pig.7<br />

Thawing Depth h at. Subgrade Center<br />

vs. Thawing Index Difference a<br />

..<br />

t=l. 58<br />

for the eecti<strong>on</strong> of coarae-grain aoil<br />

emba-ent :<br />

When calculating the minimum height of embankment<br />

by equati<strong>on</strong> 5, the value of Hmin may be<br />

preestimated, % ia determined by equati<strong>on</strong> 2 or<br />

3, and then Hmin is calculated by equati<strong>on</strong> 5.<br />

Finally, -(,at Hmin can be determined after<br />

aeveral calculati<strong>on</strong>a.<br />

POr example. in Fenghou Yt. regi<strong>on</strong>, Qinghai-<br />

Xizang plateau, hn=1,4m, a=1.52 and Q2=14515;<br />

'for the coaree-grain soil of embankment,<br />

4~0.58 and K=0.3816, its minimum height of the<br />

embadanent determined ia about 1.5m after calculati<strong>on</strong>.<br />

Based <strong>on</strong> the model teat, -<br />

P1$=52000 (deg.hr.) might be determined, which<br />

ia introduced into equati<strong>on</strong> 5:<br />

tx1.52<br />

From the test aata the relati<strong>on</strong>ship between<br />

the thawing index (Xt T ) and tha thawing depth<br />

h of slope toe (Bee Big. 8 and 9) i a obtained:<br />

where b is thawing depth of elope toe (m), h<br />

is them1 c<strong>on</strong>ductivity of the soil in berm<br />

above O°C (kcal/m.hr.deg.), Q ie Latent heat of<br />

thav,ing of the soil in berm (kcal/m), StG<br />

ie thawing index of berm (dag.&.), and kj io<br />

the correcti<strong>on</strong> for the sun-facing slope, shadow<br />

slope and soil propertieP. For the sun-facing<br />

slope toe of sand-clay embankment kt ie 0.80;<br />

for the ehadow elope kl is 0.78; for the aun-<br />

Pacing elope toe of coarse-grain soil embankment<br />

kl is 0.90 i and for the shadow slope kq is<br />

0.82<br />

1524

g 1.2 1.2<br />

0.8 0.8<br />

10.4<br />

tl<br />

OA oa 1.2 lb 2a 2.4 04 0.8 1.2 1.6 2.0 2A<br />

’ Pig.8 Belatiowhip between Thawing<br />

Depzh and Tnawing Index a% Slopp<br />

Toe of Sd-Clay Embadment<br />

a. Sun-Fsoing Slope berm<br />

b. shadow Slope berm<br />

Pig.9<br />

nela-cioaship between Thawing<br />

DepZh and Thawing Index at Slope<br />

’lor or coarse-Grain Soil EmPankment<br />

a. Sun-Pacing Slops Berm<br />

b. Shadow Slope ~ IXI<br />

coNcLusIoN<br />

The reault shows that a lot of data which are<br />

obtained difficultly in situ can be got through<br />

indoor teat. This simulating test can provide<br />

the theoretical calculati<strong>on</strong> bases for design<br />

and aow’tructi<strong>on</strong> in field. But the observati<strong>on</strong><br />

to the water field and water eupply ia not<br />

enough.<br />

REFEKENCE<br />

Ding Deweng 8nd Luo Xuepo, (1979). Theoretical<br />

base8 about model experiment of thermoteohnique<br />

of permafrost. Scientific<br />

lT0.8, 624-632<br />

1525

STUDIES ON THE PLASTIC-FILM-ENCLOSED FOUNDATION<br />

OF SLUICE GATES AND ITS- APPLICATION<br />

Yu, Bofang, Qu, Xiangmin and En, Naicui<br />

Heil<strong>on</strong>gjiang Provincial Institute of Water C<strong>on</strong>servancy, Harbin, China<br />

SYNOPSIS Based <strong>on</strong> the field experiments and engineering practice, a new type of soil foundati<strong>on</strong>-The<br />

plastic-film-enclosed foundati<strong>on</strong> was proposed and applied to the c<strong>on</strong>structi<strong>on</strong> of water<br />

c<strong>on</strong>servancy projects. Design and c<strong>on</strong>structi<strong>on</strong> procedures of the foundati<strong>on</strong> were described. To verify<br />

the reliability of the foundati<strong>on</strong> proposed, three full-scale experimental projects (sluice<br />

gates) were c<strong>on</strong>structed in seas<strong>on</strong>al frost regi<strong>on</strong>s. Observati<strong>on</strong> results from the'projects show that<br />

the proposed plastic film-enclosed foundati<strong>on</strong> can successfully protect the structures from frost<br />

damage.<br />

INTRODUCTION<br />

To solve the problems of frost damage encountered<br />

frequently in the c<strong>on</strong>structi<strong>on</strong> of hydraulic<br />

structures, a new type of soil foundati<strong>on</strong>, i.e.,<br />

the plastic film-enclosed foundati<strong>on</strong> has been<br />

intengively studied in recent years. Field<br />

investigati<strong>on</strong>s and engineering practice proved<br />

that adopting this type of foundati<strong>on</strong> could<br />

greatly reduce the frost heave of structures.<br />

Furthermore, it has the advantage of easy to<br />

c<strong>on</strong>struct and low cost. It is, therefore, an<br />

effective measure for preventing frost damage in<br />

the c<strong>on</strong>structi<strong>on</strong> of the medium- and small-scale<br />

hydraulic projects in cold regi<strong>on</strong>s.<br />

DESIGN OF THE PLASTIC FILM-ENCLOSED FOUNDATION<br />

Basis of the design of the foundati<strong>on</strong><br />

As well-known, frost susceptibilipy of soil<br />

depends chiefly up<strong>on</strong> moisture, freezing temperature<br />

and the type of soil. For a given temperature<br />

and soil, the frost susceptibility of the<br />

soil can be changed by its moisture c<strong>on</strong>diti<strong>on</strong>.<br />

Investigati<strong>on</strong>s have shown that n<strong>on</strong> or negligible<br />

amount of frost heave occurs during freezing<br />

when the water c<strong>on</strong>tent in the soil is less than<br />

'its initial water c<strong>on</strong>tent causing frost heave,<br />

which is close to the plastic limit of the soil<br />

(Wu et al., 1981: T<strong>on</strong>g, 1982). Based <strong>on</strong> this<br />

fact, the frost heave of a soil can be eliminated<br />

or greatly reduced if the water c<strong>on</strong>tent of the<br />

soil can be lowered and kept close to or less<br />

than its plastic limit. This is the scientific<br />

basis for the design of this type of foundati<strong>on</strong>.<br />

Choice of the enclosinn material<br />

At present, various kinds of impermeable films<br />

such as plastic film and variety of earth fabrics,<br />

which can be used as the enclosing sheet,<br />

are available. When choosing the enclosing<br />

material, <strong>on</strong>e should c<strong>on</strong>sider its durability,<br />

impermeability, strength, cost and c<strong>on</strong>structi<strong>on</strong><br />

c<strong>on</strong>diti<strong>on</strong>s. The comm<strong>on</strong>ly commercial polyvinyl<br />

chloride (plastic) film has the advantage of<br />

low permeability, soft, l<strong>on</strong>g running period,<br />

low cost, and eaey to be c<strong>on</strong>structed, so that<br />

it is a better choice to u8.e this plastic film<br />

as the enclosing material for the c<strong>on</strong>structign<br />

of the enclosed foundati<strong>on</strong>.<br />

It is know that plastic film has been successfully<br />

used in canal c<strong>on</strong>structi<strong>on</strong> for preventing<br />

seepage in Sweden and Norway for 30 years.plastic<br />

film has also been used in the c<strong>on</strong>structi<strong>on</strong><br />

of canal beds to prevent seepage in the Northest-<br />

Wang Farm, Beijing for more than 20 yeara. The<br />

buried (used) plastic film was sampled and<br />

tested in 1983. Test results (Table I) show<br />

that the tensile strength of the film does not<br />

decrease but increases after being used for 18<br />

years. It is predicted from the test that its<br />

durati<strong>on</strong> of service may be as l<strong>on</strong>g as 30-50<br />

years. In..additi<strong>on</strong>, applicati<strong>on</strong> of the plastic<br />

film to the hydraulic engineering at northeast<br />

and west China showed that its physical and<br />

mechanical behaviour could fairly meet the needs<br />

of engineering design. Based <strong>on</strong> these, it is<br />

decided to choose the polyvinyl chloride plastic<br />

film as the enclosing material (anti-permeating<br />

sheet) of the enclosed foundati<strong>on</strong> in this study.<br />

Design of the plastic film-enclosed foundati<strong>on</strong><br />

To design the enclosed foundati<strong>on</strong> <strong>on</strong> frost susceptible<br />

soils, it is necessary to know the<br />

maximum frost depth, maximum frost heave amount<br />

and frost susceptibility grade of the subsoils<br />

c<strong>on</strong>cerned, and then to determine the thickness<br />

(H) of the subsoils needed to be enclosed according<br />

to the thickness of the frost heaving<br />

soil as follows:<br />

H Z h - ~ t s (1)<br />

where h i s the thickness of the frost heaving<br />

soil,& is the thickness of the foundati<strong>on</strong> slab<br />

of a sluice gate and u is a reducti<strong>on</strong> coefficient,<br />

having a value of 0.5 for a small slab<br />

(with its width less than frost depth) and 0.333<br />

1526 '

TABLE I<br />

Comparis<strong>on</strong> of the Tensile Strength and Ductility of Plastic<br />

Film before and after Being Used for 18 Years<br />

Tensile strength, MPa Ductility ( X )<br />

Thickness<br />

Case<br />

mm Cross- L<strong>on</strong>gitudinal Cross- L<strong>on</strong>gitudinal<br />

secti<strong>on</strong>al<br />

secti<strong>on</strong>al<br />

0.12-0.14 18.87 24.43 261.3 224 B<br />

0.13-0.15 32.60 33.20 8-40 10-190 A<br />

0.14-0.15 18.10 24.27 261.3 264 B<br />

0.14-0.15 27.10 33.20 4-8 4-40 A<br />

Note: B - Before buried in,l965, A - Sampling in 1983.<br />

for a larger slab, respectively.<br />

To eliminate the effect of frost heave caused<br />

by the subsoil around the foundati<strong>on</strong> slab, the<br />

dimenti<strong>on</strong> at the top of the enclosed soil body<br />

must be greater than that of the slab base at<br />

least by 0.5 m at each side. The lateral surface<br />

of the enclosed soil body could be vertical,<br />

or a slope of 1 <strong>on</strong> 1,depending up<strong>on</strong>.the excavati<strong>on</strong><br />

st-ability c<strong>on</strong>diti<strong>on</strong> of the pit.<br />

The fill material could be any kind of finegrained<br />

soils. But, its unit weight and water<br />

c<strong>on</strong>tent must be carefully c<strong>on</strong>trolled during c<strong>on</strong>struqti<strong>on</strong><br />

so as to meet the requirement of designed<br />

bearing capacity and allowable.maximum<br />

frost heave of the subsoil.<br />

In additi<strong>on</strong>, it is better to seperate the enclosed<br />

soil foundati<strong>on</strong> into several individual<br />

layers with plastic films i n order to reduce<br />

moisture migrati<strong>on</strong> (thus the frost heave amount).<br />

The thickness of each layer is suggested to be<br />

, not greater than 0.35-0.5 m.<br />

The design of overlying structure is in principle<br />

the same as the design of usual sluice gate.But,<br />

the following two points should be taken into<br />

c<strong>on</strong>siderati<strong>on</strong>: (1) The buried depth of foundati<strong>on</strong><br />

slab can be designed c<strong>on</strong>sidering <strong>on</strong>ly the<br />

strength and stability of the structure itself,<br />

not the effect of frost heave. (2) Proper antifrost<br />

heaving measures should be taken for the<br />

frost susceptible soil behind the side wall of<br />

the sluice gate to avoid the gate uplifting due<br />

to frost heave.<br />

CONSTRUCTION OF THE PLASTIC FILM-ENCLOSED<br />

FOUNDATION<br />

Excavati<strong>on</strong> of pit<br />

joints between the glued films need to be staggered<br />

with the width of 15-20 cm. To prevent<br />

the film from tearing by st<strong>on</strong>e or tree roots,<br />

the exposed surface of the pit should be carefully<br />

cleaned before laying films.<br />

Fill c<strong>on</strong>structi<strong>on</strong><br />

The water c<strong>on</strong>tent of the fill must be carefully<br />

c<strong>on</strong>trolled to meet the needs of design. St<strong>on</strong>es,<br />

hard piece of soil and other hard materials,<br />

which may tear the film, should be taken out<br />

from the fill, Fill materials should be compacted<br />

layer by layer with its unit weight<br />

meeting design value. Inter-layer insulating<br />

sheets will be placed during filling with their<br />

joints also staggered. As the height of the fill<br />

reaches its design value, the outer enclosing<br />

sheets are finally enclosed. By now the c<strong>on</strong>structi<strong>on</strong><br />

of the foundati<strong>on</strong> is ccmpleted.<br />

EXPERIMENTAL PROJECTS<br />

Outline of the experimental projects<br />

To test the reliability of the plastic-filmenclosed<br />

foundati<strong>on</strong>, three experimental projects<br />

were c<strong>on</strong>structed at Jid<strong>on</strong>g County, Hailin County<br />

and Hulan County in Heil<strong>on</strong>gjiang Province,Northeast<br />

China. For the c<strong>on</strong>venience of discussi<strong>on</strong>,<br />

they are numbered as No.1, No.2 and No.3 in this<br />

paper, respectively.<br />

Some of the natural site c<strong>on</strong>diti<strong>on</strong>s for the projects<br />

are shown in Table 11. The dimenti<strong>on</strong> and<br />

form of the foundati<strong>on</strong>s and overlying structures<br />

for the test. projects are the same. Drawings<br />

of the l<strong>on</strong>gitudinal secti<strong>on</strong>, airview and crosssecti<strong>on</strong><br />

of the projects are shown in Figs.l,2<br />

and 3 , respectively, in which dimenti<strong>on</strong>s are in<br />

cm.<br />

posed surface should be as smooth as possible.<br />

Placing of enclosinn sheet<br />

Before placing, the purchased small pieces of<br />

plastic film should be glued together with an<br />

overlapped width of 5-10 cm. When placing, all<br />

Observati<strong>on</strong>s <strong>on</strong> the experimental proiects<br />

Frost depth, frost heave amount at ground surface<br />

and displacement of structures tested were<br />

observed <strong>on</strong>ce every five days during freezing<br />

period. The depth of groundwater table was also<br />

1527

TABLE I1<br />

Site C<strong>on</strong>diti<strong>on</strong>s for the Experimental Projects<br />

Annual mean Minimum Average<br />

Maximum frost Groundwater Type of<br />

air temp. air temp. frost depth heave amount table<br />

No. "C OC cm cm<br />

soil<br />

cm<br />

1<br />

2<br />

3<br />

2.3<br />

2.5<br />

-<br />

-30<br />

-38. a<br />

-<br />

170 22 - Clay<br />

183 22 70 Loam<br />

- 22 50 Loam<br />

Fig.1<br />

L<strong>on</strong>gitudinal Secti<strong>on</strong> of the Experimental Project<br />

V-levelling<br />

points<br />

. .<br />

Fig.3 Cross-secti<strong>on</strong> of the<br />

Experimental Project<br />

Fig.2<br />

Airview of the Experimental Project<br />

observed. A set of thermal couples were placed<br />

in the foundati<strong>on</strong> of test project No.1 to m<strong>on</strong>itor<br />

the actual frost depth of the foundati<strong>on</strong>.<br />

Observati<strong>on</strong> results and discussi<strong>on</strong><br />

Variati<strong>on</strong>s of the observed frost heave amount<br />

at ground surface, the displacement of structures<br />

and frost depth with time for the three<br />

projects were shown in Figs.4,5 and 6 , respectively.<br />

1528

6<br />

A 4<br />

Fig.4 Curves of Frost Heave Amount at Ground ,<br />

Surface (l), displacement of Structure (2),<br />

frost depth (3) and Groundwater Table (4) vs<br />

Time for No.1 Test Project<br />

t<br />

Fig.6, Curves of Frost Heave Amount at Ground<br />

Surface (l), Displacement of Structure (2)<br />

and Frost Depth (3) vs Time €or Nor.3 Test<br />

Project<br />

It i s seen from Figs.4 and 6 that while the<br />

maximum frost heave amount at natural ground<br />

surface reaches up to 22 cm, the frost heave<br />

amount is <strong>on</strong>ly about 3 cm occuring in the ec- '<br />

closed foundati<strong>on</strong> soil (fill) with original<br />

wa.ter c<strong>on</strong>tent o f 23X, which is less than the allowable<br />

deformati<strong>on</strong> of the structure. Fig.5<br />

shows that there was no frost heave but a small<br />

amount of frost c<strong>on</strong>tracti<strong>on</strong> occuring in the<br />

foundati<strong>on</strong> soils of No.2 test project, for which<br />

the original water c<strong>on</strong>tent is less than 17X.<br />

Observati<strong>on</strong>s <strong>on</strong> the experimental projects were<br />

c<strong>on</strong>tinuously made for four years. No damage<br />

has occured at all the three projects up to day,<br />

proving that the new type of foundati<strong>on</strong> is reliable<br />

in applicati<strong>on</strong> to hydraulic projects.<br />

cool<br />

Fig.5 Curves of Frost Heave Amount at Ground<br />

Surface (l), Displacement of Structure (2) and<br />

Frost Depth (3) vs Time €or No.2 Test Project<br />

Observati<strong>on</strong> shows that the plastic-film-enclosed<br />

foundati<strong>on</strong> also has a certain effect of heat<br />

insulati<strong>on</strong>. For example, the maximum frost<br />

depth observed at No.1 project is about 17% less<br />

than that at natural site.<br />

CONCLUSIONS<br />

Observati<strong>on</strong>s <strong>on</strong> experimental projects show that<br />

the plastic-film-enclosed foundati<strong>on</strong> discussed<br />

here is obviously effective <strong>on</strong> anti-frost heaving.<br />

Besides, it has the advantage of easy to<br />

be c<strong>on</strong>structed and low cost. It is, therefore,<br />

recommended that the plastic-film-enclosed foundati<strong>on</strong><br />

can be widely used in geotechnical engineering<br />

such as hydraulic project, airport,<br />

pipeline, road and civil engineering in cold<br />

regi<strong>on</strong>s. Test results show that the purchasable<br />

plastic (polyvinyl chloride) film can meet the<br />

needs of strength, ductiJity, impermeability and

durabi litv for t he foundati<strong>on</strong> design, and it<br />

is also cheep, so that i c is an ideal enclosing<br />

material for c<strong>on</strong>structi<strong>on</strong> of this foundati<strong>on</strong>.<br />

REFERENCES<br />

T<strong>on</strong>g Changjang, (1982). Frost heave behaviour<br />

of seas<strong>on</strong>ally active layer in Fenghuo Mt.<br />

area <strong>on</strong> Qinghai-Xizang Plateau. Proceedings<br />

of the First Nati<strong>on</strong>al <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong><br />

Glacier and <strong>Permafrost</strong>, Chinese Science<br />

Press,1982.<br />

Wu Ziwang, Zhang Jiayi, Wang Yaqing and<br />

Shen Zh<strong>on</strong>gyan, (1981). Experimental<br />

studies <strong>on</strong> frost heave of soils. Annals<br />

of Lanzhou Institute of Glaciology and<br />

Geocryology, Academia Sinica, No.2, pp.<br />

82-96, Chinese Science Press. 1981.<br />

1530

GEOCRYOLOGICAL BLOCK OF OIL AND GAS PRODUCING<br />

AND TRANSPORTING GEOTECHNICAL SYSTEMS<br />

Y.F. Zakharovl, Y.Y. Podborny2 and G.I. Pushkd<br />

*Engineerinpgmlogical Department, TyumenNIICiprogai, Tyumen, U.S.S.R.<br />

aEGM Trust, Urengoi, U.S.S.R.<br />

smoPsxs<br />

Safe running of oil and gaa producing and ~raneportiag uystame In pamafrost z<strong>on</strong>m<br />

i~ provi8ed by progrese in the dbaign of hydrocarb<strong>on</strong> projeoting and c<strong>on</strong>stant enginemring-geological<br />

m<strong>on</strong>itoring of its c<strong>on</strong>diti<strong>on</strong>. To achieve this a epocial progranrme accounting to the changea<br />

in mng~~ebTi~g-~eological c<strong>on</strong>diti<strong>on</strong>a of c<strong>on</strong>etmwbiorr. and ming af the aysta waB worked out<br />

ir Wmst Siberia, A the uam aha a rpeoial aaxviae was organized to o<strong>on</strong>trol the syetem'e o<strong>on</strong>diti<strong>on</strong>,<br />

to preaiot a d pravant hazardoum change@ in $eologioal envir<strong>on</strong>ment.<br />

To pFovido prol<strong>on</strong>ged and safe running of oil,<br />

gas and c<strong>on</strong>densate produaing and transporting ,<br />

nyetema In permafrost regi<strong>on</strong>s It in vitally<br />

neceaeary to maintain their deaign and management<br />

according to the requiremenfa of aystem<br />

analysis. From the eystem analynin point of<br />

view 011 and gas fields aB well aa trunk pipelines<br />

repreaunt highly or anised c<strong>on</strong>trolled<br />

gsotechnical systems (GTS with numerous fraafornards<br />

and feedbaoks between their-subsynterns,<br />

blocks and elements. Apart from these<br />

intermel relati<strong>on</strong>s GTS ketp various outer c<strong>on</strong>(<br />

necti<strong>on</strong>n with natural. mnd mamade envir<strong>on</strong>ment,<br />

In this multypurpoae functi<strong>on</strong>al complexity of<br />

6TS especially in thr Northern mgoina of West<br />

Siberia the main role bel<strong>on</strong>gs to geocryologic<br />

blook of GTS geosphers. Thia most dynamic and<br />

vulnerable block determinen the design chtisac-<br />

tar of itn ueo<strong>on</strong>d subaystsm - teohosphera -<br />

and'xegulates the majority of technological<br />

and engineerin~-geol.ogicsl procesaen in GTS'<br />

functi<strong>on</strong>ing, whiah often progrssses in extreme<br />

coriditi0n8, For inert ace, to prevent thewing<br />

of pipeline permafrost bedding and to<br />

avoid t d rmbaidence it was c<strong>on</strong>sidered necessary<br />

to aquj.lizs gan and ground temperaturea<br />

and to apply apeeial c<strong>on</strong>stxucti<strong>on</strong> teohniquea<br />

and complex cooling dericsn in as trannport,<br />

~f due *o teahologicsl difficulftiea of GTS<br />

funoti<strong>on</strong>fng preventi<strong>on</strong> of parmafxoat thawing<br />

does not mean possible if will make menma to<br />

carry out the o<strong>on</strong>trolled thawing which reduce8<br />

the negative aequenoes fa$ gOological envir<strong>on</strong>ment<br />

arnd technouphere, Still, to achieve<br />

thia <strong>on</strong>e ha8 to know the chsraoteriaticn of<br />

geooryologic and geologioal procesaeer in c<strong>on</strong>crete<br />

engineering-gsologiosl c<strong>on</strong>diti<strong>on</strong>s,<br />

Typioal elements of GTS geoeryologioal block<br />

are ice o<strong>on</strong>tent, tpperaturss, aeaa<strong>on</strong>al thawing<br />

a d frrseing depth and velocity, cryogenio<br />

PXWOOUU~B, thiokneas of psmafroat and it8<br />

interrelati<strong>on</strong> with wstera, cryogags.<br />

Duxinp c<strong>on</strong>structi<strong>on</strong> and functi<strong>on</strong>ing of the<br />

GTS all these elamante tend to alter under<br />

the direot effect of technospheric abjecta or<br />

throught the feedback impeat ~ft8r their neti<strong>on</strong><br />

up<strong>on</strong> geologicaL envir<strong>on</strong>ment. For example,<br />

though it may meem unrelated with pemafxost,<br />

prolanged exploitati<strong>on</strong> of gas and c<strong>on</strong>densate<br />

plays resulta in their qompacti<strong>on</strong> snd Ieada<br />

to the aubstdenos of fieldla Baylight area.<br />

This subaidrnce xesulta in fisldla flooding<br />

and accumula-bi<strong>on</strong>s of water omuse pemafrost<br />

thawing.<br />

When large mount of heat ammitting c<strong>on</strong> -<br />

stmcti<strong>on</strong>r ma CIQTV~C~U (ire. praatically eve:<br />

ry modern oil and gal producing and transporting<br />

system) appeara in permafr<strong>on</strong>t E<strong>on</strong>e fhi6<br />

procem reuults in largeaoale franaformati<strong>on</strong><br />

of permafroat landacapes during GTS a<strong>on</strong>atxuctd<br />

i<strong>on</strong> whioh causeu permafrost dsgrabti<strong>on</strong> even<br />

in lor Camperature secti<strong>on</strong>m. Coaarete parmet-<br />

ISU of GTS geoorgologio block elmentat alterati<strong>on</strong>s<br />

dhpend <strong>on</strong> engineering-geological atructurs,<br />

landsoape and meteorologic o<strong>on</strong>diti<strong>on</strong>s<br />

of the texritorg, stesngtb of inten:<strong>on</strong>nec.ti<strong>on</strong>u<br />

and character of acting faotors. !Phe above -<br />

menti<strong>on</strong>ed altexati<strong>on</strong>s - as a reault of human<br />

c<strong>on</strong>otructivs and productive activity - in<br />

turn caume in GTS ohangea in object# of technouphe-<br />

8gd in corrOmp<strong>on</strong>ding ologlcal enviromenta1<br />

maaaen (8.g. grounrfwndati<strong>on</strong>s<br />

aubaidence, basement diqrmpti<strong>on</strong>, deformati<strong>on</strong><br />

of buildingn, nsrvice linen and other atmaturem,<br />

envir<strong>on</strong>ment c<strong>on</strong>taminstian, etc.). To<br />

prevent such dangeroua effects in running oil<br />

and gas producing and transporting GTS the<br />

following is beneficial:<br />

a) At I). deeign 8ta e of OTS creeti<strong>on</strong> c<strong>on</strong>mider<br />

its geocryologic b 9 ock (denpits of it8 complexity)<br />

in cXose c<strong>on</strong>necti<strong>on</strong> with ita Inner<br />

and Outer ,fesdfomedds a d feedbacks with 0ther<br />

GTS blocka; 2.e. the deaign work should be<br />

based <strong>on</strong> complex engineering-geologic psedioti<strong>on</strong><br />

of the c<strong>on</strong>sequences af GTS functi<strong>on</strong>ing,<br />

geoaryolbgic fOXm36t included.<br />

b) While operatine; ETS c<strong>on</strong>atanfly receive detailad<br />

infomati<strong>on</strong> c<strong>on</strong>cerning current interaati<strong>on</strong><br />

between the objects and geological envir<strong>on</strong>ment,<br />

enpeeially frozen, freeeing and<br />

thawing soila, which ia vlttally naceasary<br />

for careful c<strong>on</strong>trol OV~T technological and<br />

<strong>on</strong>einasring-geological proteases.<br />

A. Projeoti<strong>on</strong> of oil and pas producing Rnd<br />

transporting GTS in pemafrost z<strong>on</strong>e of West<br />

1531

Siberin i .s c~rried out with reapec t to antropogenic<br />

~l.tar~.ti<strong>on</strong>n of thermal c<strong>on</strong> lditi<strong>on</strong>a of<br />

aesmns; freezing-thawing layer and c<strong>on</strong>siderabls<br />

permafr<strong>on</strong>t temperature rise in geospherea<br />

of 01; ma gas c<strong>on</strong>diti<strong>on</strong>ing plants, compxesnor<br />

pumping Rnd bo<strong>on</strong>fer stati<strong>on</strong>s of pipelines,<br />

fisldn an8 pipelines infrnntructure objects<br />

End accomodati<strong>on</strong> camps. Initial. engineering<br />

&age Rt the abovementi<strong>on</strong>ed aitea usually caus<br />

e the ~ diarupti<strong>on</strong> of m<strong>on</strong>s-lichen cover (ita<br />

aver%@ thickness in GTS In queati<strong>on</strong> reachen<br />

15-20 cm) and mil and vegetati<strong>on</strong>. Thus, ground<br />

temperature rises by I-2OC simultaneously -<br />

increasing thickness of aeaa<strong>on</strong>nlly thawing<br />

layer. Changeu of permafrost temperatures caused<br />

by vegetati<strong>on</strong> disrupti<strong>on</strong> is lean pr<strong>on</strong>ounced<br />

Northward. Sme thing happena with GTS ayrface<br />

Thoding; if such ia the cane neas<strong>on</strong>al<br />

freezing depth deareaaea 2,5 times. On the<br />

other hand fhia depth rapid1.y grown at vegetsti<strong>on</strong><br />

removal (].ow pemenbility aanda frteze<br />

down to 4 m claya and clayey silta freeze<br />

down to 3 ti15 Rnd when high permeability noila<br />

are enchorea <strong>on</strong> nitc by drainage, The latter<br />

may resu1.t in new permafrost formati<strong>on</strong> - an it<br />

happenn with drainage - and that must be taken<br />

into nccount while preparing the sitea beceusa<br />

drdning may come out n<strong>on</strong>-effective. Newly<br />

formed permnfrost of mtropogenic origin in<br />

South Arctic GTS are normally characterized by<br />

high ice c<strong>on</strong>tent which is 9XC98aiVe oompsred<br />

to pemsability of the ground in thmv. Similar<br />

chmngea in permafrost thermal c<strong>on</strong>diti<strong>on</strong> result<br />

from auch inevitable o<strong>on</strong>aenuanaea of OTS mnn-<br />

ing .BS snow removal, compacti<strong>on</strong> or c<strong>on</strong>taminati<strong>on</strong>,<br />

Landscape trannfomati<strong>on</strong> md direct thermal<br />

tfPect of oil and gas producing and tranmportinp<br />

ayatema up<strong>on</strong> permefroat induces thermokwat<br />

Rnd through feedback in OTS threaten<br />

syatem'n safety. Most typical fhemokarat .<br />

symptom ia Tunnel around the wellhead and rock<br />

settlement near heat emitting objeota: also am<br />

a renult of icy ground thawing cauaed by antropo<br />

enic influence. Maximal funnel dimenui<strong>on</strong>s<br />

are f m in dimnetre and 1,5 m in depth. They<br />

mey be es8ilg cured by filling in draining<br />

earth material,<br />

Because ice c<strong>on</strong>tent of the majority of permefrost<br />

comglexes in ail and gas produaing and<br />

transporting GTS reaches 25-557, thermal subsidence<br />

of th8WiW ground usually @meeds limits<br />

aet for the objects of much GTS. That is<br />

why in the majority of GTS all the stmeturea<br />

nre built with preliminary thawing and <strong>on</strong>ly<br />

<strong>on</strong> pil~s foundati<strong>on</strong>.<br />

Sine8 c<strong>on</strong>rtmcti<strong>on</strong> and running of the GTS<br />

unuslly change characteristics of surface coverm,<br />

soil humidity a d atmospheric heat exchanpe<br />

COnditiOn8, permafr<strong>on</strong>t end Iess<strong>on</strong>al<br />

tbawlng ground tend to heave. Most prominent<br />

mmnifestati<strong>on</strong> of thia procesa cRn bs observed<br />

in pu'lverieed lorn and sandy loam, where<br />

totm heave reaches 1,5 m, with pile-ground<br />

&freezing exceeding anchoring strsn<br />

the piJ.8. To prevent heaving of pils%%lati<strong>on</strong>s<br />

th8y have to inemsue the load <strong>on</strong> them<br />

which in turn threatens oarrging oapmity of<br />

the pile when/if unexpected thawing occurs.<br />

Sad experience of fighting the problem of<br />

foundati<strong>on</strong> hbavinp <strong>on</strong> the initial stage of<br />

developing Xedvejye rrnd Pyngepurovnkoye gas<br />

field8 mads it cotnpulnory to take into BCcount<br />

engineering-gsologic.1 fo~eceat at<br />

1532<br />

field pxojecting in Wesf Siberi8,<br />

When ice-c<strong>on</strong>taining xocka and thawed penna -<br />

frouf freeze <strong>on</strong>ae again, thamokaraf and heaving<br />

et drilling gslr wells result in deformati<strong>on</strong><br />

Of severpl drill atrings under bearing<br />

ntrena. Curing of auch ssrioua problem dsmmdad<br />

retrieving atring parta and .their complex<br />

repsir. To pssvent such dangeroun c<strong>on</strong>asquences<br />

thorough gaocryologic analyaln of the ferxitory<br />

is nwenaary to chooae the locati<strong>on</strong> of well<br />

cluuterw, c<strong>on</strong>ntructi<strong>on</strong> and technologiaal chengsa<br />

end time definiti<strong>on</strong> for safe well nhu-kdown.<br />

Site prepmati<strong>on</strong> and dtgging which brfngn to<br />

daylight area watery pulverized loam and psety<br />

aoiln of Arctic ragi<strong>on</strong>s of Weat Siberia, re -<br />

sultn in their .frost fracturing. Originated<br />

thus rtrees reaches X6700 H (Geoczyologichenkip<br />

ualoviye ... 1983). maiasa broken IOFViae<br />

linea, polyg<strong>on</strong>s of fraClWTes in 3-4 par8<br />

trsnafom info ayntema 09 polyg<strong>on</strong>al wibdge toe<br />

which hamper8 running of field and pipeline<br />

GTS. The <strong>on</strong>ly ray ho avoid deatmctiv* influence<br />

of the abovementi<strong>on</strong>ed .cryogenic procemses,'<br />

ia tapping of aurfaoa an8 melt water f'xom sits.<br />

To explom and develop Borfherm gam fields of<br />

Weut Siberia they have to build tempOr8Ty ninfar<br />

roads - nzbnikan with crossings over<br />

frozen T~VWEI and bxookn. Theae dements of<br />

future GTS b~ing to life fornati<strong>on</strong> of iding in<br />

river valleys whom it were not obmexvea before.<br />

The <strong>on</strong>ly nay to protect land and rivex<br />

vehich~, Iirrhery and c<strong>on</strong>utmeti<strong>on</strong> is to find<br />

less risky patohea of the valley.<br />

h~1dBU~p8 tramfoxmati<strong>on</strong> in oil and gan produeing<br />

and tramportin GTS In Arctic sagi<strong>on</strong>s<br />

of west Siberia r8SUlfing in vags*rati<strong>on</strong> layer<br />

TM~IOYP~~ nfimulatme slope soliflucfi<strong>on</strong> and even<br />

rapid Elides. of earth maum1m. Suoh cryogenic<br />

psocesses normally take placm <strong>on</strong> tha slopea<br />

3-4O &sap mosf intenaivoly when the domiamit<br />

roak is pulvexiaed loem ox ailty Loam, rhawod<br />

ground mobility grown mflth~asd ana ao~~flueti<strong>on</strong><br />

upmads over less skeep mZopeB, Moat ef -<br />

fsotivs wag to prevsn% thia is to c<strong>on</strong>trol trevel<br />

of track vehiclem al<strong>on</strong>g tunare -a to order<br />

digging and excavati<strong>on</strong> in mummer,<br />

While %hawing permafrost in oil and gea producing<br />

GTiTof Weat Siberia, Yakutis and Far<br />

North of tha European part of the U.S.S.R.<br />

Lose almoat completely its cerrging capscity<br />

thus aggravating deformati<strong>on</strong>el properties. In<br />

frozen c<strong>on</strong>diti<strong>on</strong> roaks are characterized by<br />

high veluss of thsae properties tens ox even<br />

hundreds of timea exceeding simmilar parmetera<br />

of malt ground. The dependance of compressi<strong>on</strong><br />

factors of frozen ground <strong>on</strong> changer of<br />

their physical properbiea and temperature wm<br />

studied in the ~mku of N.A.zitovitch (1973)<br />

end othexa. Similar relati<strong>on</strong>whip for peaty<br />

soils wnaa deacrihed by L.T.Roman (1981).<br />

L<strong>on</strong>g tima running of hup oil Rnd g ~ produc- s<br />

ing and tranaporting GTS Rccompanied by intensive<br />

thermal acti<strong>on</strong> up<strong>on</strong> permafroat lsssen<br />

the thickness of frozen I.aysr which reachan<br />

400 m in certain spots. Beside8 pasma~rost<br />

thnwing due to dirtct thenn~l Rcti<strong>on</strong> and indirect<br />

influence of antmpogenic activity<br />

up<strong>on</strong> subsurface pexmlfrost laysxa, oil and<br />

especial; y gas extracti<strong>on</strong> rmovea the Screen<br />

en route of thermal flow from the depths and<br />

violdes pressure and temperature balance,<br />

thua causing dcgrsaatian of pemefrost from<br />

beneath (Baulin, I85). Unfortunately, the

forecaat of nuch nlow process oannot yet be<br />

calculated with enough accuracy, that in why<br />

it is not taken info account at fhs dcaignlng<br />

of GTS.<br />

B. To receive <strong>on</strong>-line informati<strong>on</strong> c<strong>on</strong>cerning<br />

dynsmios of the proceases in the abovernent -<br />

i<strong>on</strong>s& GTS Por the most effectI’ive c<strong>on</strong>trol over<br />

thermal and geomechanical inferaefl<strong>on</strong> between<br />

objects and frozen, thawing and Preszing<br />

rocka Ministry of gam of the U.S.S.R. organ-<br />

Ized in West Sibrxia special aexviccr or en -<br />

gin4asing-geological m<strong>on</strong>itoring (EGM). The<br />

main task of this service, apart from the<br />

stated, is generati<strong>on</strong> of scirntifia mcom -<br />

mendati<strong>on</strong>a and demign decisi<strong>on</strong>s <strong>on</strong> soil rehabilitati<strong>on</strong>,<br />

msintenanoe technology, 4tc.<br />

Am<strong>on</strong>g the latter moat importent me anchoring<br />

of the dimruptured ground foundati<strong>on</strong>s,<br />

strengthening of the dintorted foundati<strong>on</strong>s,<br />

c<strong>on</strong>taminated soil smhabilitafl<strong>on</strong>, water<br />

we1 1.8 regenerati<strong>on</strong>, stc<br />

EGM nerviee of technoaphera objscfn amprimem<br />

meeruuring subsideme, displaoment, bbnlding,<br />

curving, fraxlturing and Pisrurr widening,<br />

corrosi<strong>on</strong> degree. Geologic msesuxsmmnta<br />

include voltage values, change of phase,<br />

cryogenic procesneu dynamics, changen in<br />

strength, def<strong>on</strong>nati<strong>on</strong> and rheolog of fromn,<br />

thawing =a fmszing aoi~s and vt%satii<strong>on</strong> of<br />

ground foundati<strong>on</strong>s of c<strong>on</strong>structi<strong>on</strong>s with omsiderable<br />

dynamic losd.<br />

The theory and methodology of a new tnia of<br />

emcinesrinp: activity - GTS eminsaxinff-Reolo-<br />

<strong>on</strong>ly positive nag fo op@m in full mrauum<br />

the aggravating c<strong>on</strong>diti<strong>on</strong> of gmological @vir<strong>on</strong>mmf<br />

OT running engineering objectn, au<br />

they gTOW old.<br />

1533

Author Index<br />

Afanasenko, V.Ye., 659<br />

Aguirre-Puente, J., 299,324<br />

Ahumada, A.L., 661<br />

Akagawa, Satoshi, 1030<br />

Aksenov, VI., 333<br />

Allard, M., 113,148,199,980<br />

Allen, D., 33<br />

Andersland, O.B., 1165<br />

Anders<strong>on</strong>, Prestrud S., 666,770<br />

Anisimova, N.P., 290<br />

Arc<strong>on</strong>e, SA., 910,927,988<br />

Bakkehgi, S.,39<br />

Bandis, C., 39<br />

Barry, R.G., 119<br />

Bartoszewski, S., 543<br />

Baulin, V.V., 123<br />

Beaty, A.N.S., 1363<br />

Beget, J.E., 622,672,897<br />

Bell<strong>on</strong>i, S., 678<br />

Ben-Mikoud, K., 980<br />

Bennett, L.P., 683<br />

Berggren, A.-L., 1078<br />

Bevzenko, Y.P.,815<br />

Bianov, G.F., 1036<br />

Bird, K.J., 50<br />

Bjerkelie, D., 546<br />

Blumstengel, W., 689<br />

Booth, G.G., 955,1242<br />

Bosikov, N.P., 695<br />

Bradley, G.P., 1256<br />

Braley, W.A., 1352<br />

Bredesen, B.A., 1206<br />

Bdthauer, S.R., 1312<br />

Bruggers, D., 1301<br />

Buk, E.M., 294<br />

Bukaty, M.B., 462<br />

Burgess, M.M., 916<br />

Burn, C.R., 633,700<br />

Burns, R.A., 949<br />

Burt<strong>on</strong>, B., 436<br />

Buska, J.S., 1039 .<br />

Buvey-Bator, R., 123<br />

Baek-Madsen, C., 552<br />

Caine, N., 349<br />

Cames-Pintaux, A.M., 299<br />

Carbee, D.L., 1200<br />

Carls<strong>on</strong>, L.E., 1004<br />

Carls<strong>on</strong>, R.F., 546<br />

Carter, L.D., 706<br />

Cart<strong>on</strong>, A., 712<br />

Chamberlain, E.J., 308, 1045<br />

Chang, R.V., 1298<br />

Chapayev, A.A., 1186<br />

Chekhovskyi, A.L., 123,1368<br />

Chen, Fahu, 903<br />

Chen, X.B., 304<br />

Cheng, Enyuan, 1051,1253<br />

Cheng, Guod<strong>on</strong>g, 308<br />

Chervinskaya, O.P., 537<br />

Chir<strong>on</strong>, M., 922<br />

Chizhov, A.B., 313<br />

Chmal, H., 44<br />

Chodak, T.,316<br />

Chuvilin, Ye.M., 320,528<br />

Clark, M.J., 558<br />

Cohen-Tenoudji, E, 324<br />

Collett, T.S., 50<br />

Collins, C.M., 56<br />

Cook, J.D., 776<br />

Corapcioglu, Yavuz M., 61<br />

Corte, A.E., 718<br />

Cui, Zhijiu, 724<br />

Dabrowski, K., 754<br />

Dai, Huimin, 1212,1494<br />

Dallimore, S.R., 127,132,224<br />

Delaney, A.J., 910,927,988<br />

Deng, Youseng, S16<br />

Deschatres, M.H., 324<br />

Desmhers, D.T., 67<br />

Devyatkin, V.N., 815<br />

Dijkmans, J.W.A., 728<br />

Ding, Dewen, 329<br />

Ding, Jingkang, 1056<br />

Dolzhin, S., 123<br />

Domaschuk, L., 1060<br />

Do&, G., 1500<br />

Dramis, E, 712<br />

Dredge, L.A., 564<br />

Dubikov, G.I., 333<br />

Dubikov, G.L., 123<br />

Dubina, M.M., 1372<br />

Dufour, S., 1217<br />

Dunaeva, Ye.N., 274<br />

Dyke, L., 138<br />

Eidsmoen, T.,933, 1282<br />

Ek, C., 840<br />

Elchaninov, E.A., 1377<br />

Esch, D., 1223,1292<br />

Esch, D.C., 1352<br />

Etkin, D.A., 73<br />

Evans, K.E., 568<br />

Everett, K.R., 574<br />

Fan, Xiuting, 1482<br />

Fanale, F.P., 284<br />

Fedorov-Davydov, D.C., 749<br />

Fedulov, A.I., 1066<br />

Feldman, G.M., 339<br />

Feng, ling, 107 1<br />

Ferrell, J.E., 1229<br />

Ferrians, Jr., O.J., 734<br />

Fortier, R., 148<br />

Fotiev, S.M., 740<br />

Frmss<strong>on</strong>, L., 1060<br />

French, H.M., 683,784<br />

Frolov, A.D., 43 1<br />

Fujino, Kazuo, 143<br />

Fukuda, Masami, 253<br />

Fursov, V.V., 144 1<br />

Furuberg, T.,1078<br />

Frarland, K.S., 344<br />

Fprrland, T.,344

Gagarin,V.E., 459<br />

GagnC, R.M., 949<br />

Gahe, E., 148,980<br />

Gallinger, B.J., 568,599<br />

Gavrilov, A.N., 1106<br />

Gavrilov, A.V., 3 13<br />

Gavrilowa, M.K., 78<br />

Giardino, R., 744<br />

Giegerich, H.M., 1382<br />

Gifford, G.P., 1085<br />

Gilichinsky, D.A., 749<br />

Gleas<strong>on</strong>, K.J., 349<br />

Gluza, A., 448,754<br />

Gokhman, M.R., 1413<br />

Good, R.L., 949<br />

Gorbunov, A.P., 154<br />

Gosink, J.P., 355<br />

Goto, Shigeru, 1030<br />

Gotovtsev, S.P., 189<br />

ciranberg, H.B., 67,159<br />

Grave, N.A., 580<br />

Gravis, G.F., 165<br />

Gray, J., 862<br />

Grechishchev, S.E., 1091<br />

Gregerseq, O., 933, 1206<br />

Gregory, Carringt<strong>on</strong> E., 770<br />

Grzes, M., 361<br />

Gubin, S.V., 759<br />

Guo, Mingzhu, 1388<br />

Guo, Pengfei, 583<br />

Gurnell, A.M., 558<br />

Guryanov, LE., 1235<br />

Haeberli, W., 764,937<br />

Hallet, B., 770 '<br />

Hammer, T.A., 955, 1242<br />

Han, Huaguang, 1388<br />

Hanna, A.J., 1247<br />

Harris, C., 776<br />

Harris, S.A., 364,689<br />

Harry, D.G., 784<br />

Haugen, R.K., 56<br />

He, P., 304<br />

Headley, A,, 73<br />

Henry, K., 1096<br />

Hinkel, K.M., 819<br />

Hinzman, L.D., 590<br />

Holden, J.T., 370<br />

Holty, J., 355<br />

Holubec, I., 1217<br />

H<strong>on</strong>g, Yuping, 1393<br />

Hopkins, D.M., 790<br />

Horiguchi, Kaoru, 377<br />

Huang, Cuilan, 442<br />

Huang, S.L., 943<br />

Huder, J., 937<br />

Humist<strong>on</strong>, N., 1262<br />

Hunter, J.A., 949<br />

Hunter, J.A.M., 127<br />

Ivanova, N.V., 333<br />

Izaks<strong>on</strong>, V.Yu., 1397<br />

Izuta, H., 522<br />

Jahn, A., 796<br />

Jarrett, P.M., 1363<br />

Jeckel, RP., 170<br />

Jiang, H<strong>on</strong>gju, 1051 , 1253,1393<br />

Jin, Naicui, 1526<br />

Johns<strong>on</strong>, E.G., 1256,1318<br />

Johns<strong>on</strong>, J.B., 1039<br />

J<strong>on</strong>es, R.H., 370<br />

Jorgens<strong>on</strong>, M.T., 176<br />

Judge, A., 33<br />

Judge, AX, 971<br />

Juvigne, E.,840<br />

Kadkina, E.L., 1036<br />

Kane, D.L., 590<br />

Kapranov, V.E., 1450<br />

Karczewski, A,, 596<br />

Karlinski, M.I., 1407<br />

Karpov, Y.G., 484<br />

Katas<strong>on</strong>ov, E.M., 801<br />

Kato, Kikuo, 143<br />

Kawasaki, K., 355<br />

Kennedy, F.E., 1262<br />

Kershaw, G.P., 568,599<br />

Kershaw, L.J., 599<br />

Reusen, H.-R., 937<br />

Khastou, B., 324<br />

Khishigt, A., 123<br />

Khlebnikova, G.M., 749<br />

Khrustalev, L.N., 1102,1403<br />

Kidd, J.G., 790<br />

King, L., 183<br />

Kinney, T.C., 1476<br />

Klementowski, J., 44<br />

Klimovsky, I.V., 189<br />

Klysz, P., 84<br />

K<strong>on</strong>dratyev, V.G., 1407<br />

K<strong>on</strong>dratyeva, K.A., 274<br />

K<strong>on</strong>ischev, V.N., 381<br />

€C<strong>on</strong>rad, J.-M., 384<br />

Korolyev, A.A., 1407<br />

Kovalkov, V.P., 805<br />

Krantz, W.B., 349<br />

Kreig, R.A., 56, 176<br />

Kriv<strong>on</strong>ogova, N.F., 1268<br />

Kr<strong>on</strong>ik, Ya.A., 1106<br />

Knewinski, T.G., 955,1242<br />

Kudoyarov, L.I., 1268<br />

Kudryavtseva, N.N., 749<br />

Kumai, Motov, 390<br />

Kurfurst, P.J., 127<br />

Kuskov, V.V., 961<br />

Kutasov, I.M., 965<br />

Rutvitskaya, N.B., 1413<br />

Kuzmin, G.P., 1298<br />

Labutin, V.N., 1066<br />

Ladanyi, B., 1175<br />

Lafleche, P.T., 971<br />

Lalji, D.S., 1271<br />

Landvik, J.Y., 194<br />

Latalin, D.A., 1472<br />

Lavrov, N.P., 1417<br />

Lebedenko, Yu.P., 396,528<br />

Le<strong>on</strong>ard, M.L., 1121<br />

Lewkowicz, A.G., 605<br />

Uvesque, R., 199<br />

Li, Anguo, 1110<br />

Li, Changlin, 1346<br />

Li, Xinguo, 107<br />

Li, Xnr<strong>on</strong>g, 1026<br />

Lin, Fengt<strong>on</strong>, 61<br />

Lindh, L., 89<br />

Lindner, L., 84<br />

Lisitsina, O.M., 233<br />

Liu, H<strong>on</strong>gxu, 11 16<br />

Liu, Jim-du, 15 11<br />

Liu, Jiming, 516<br />

L<strong>on</strong>g, E.L., 1277<br />

Lou, Anjin, 1056, 1520<br />

Loubiere, J.-E, 922<br />

Lozano, N., 943<br />

Lu, B.T.D., 1121<br />

Lu, Guowei, 205<br />

Lugovoy, P.N., 1407<br />

Lunardini, V. J., 1127<br />

Lunne, T., 1282<br />

Lyvovitch, Yu.M., 1454<br />

LAg, J., 977<br />

MacAulay, H.A., 949<br />

Machemehl, J.L., 1422

Mackay, Ross J., 809<br />

Mahar, L., 1121<br />

Makarov, V.I., 1036<br />

Makarov, V.N., 401<br />

Makeev, O.V., 1288<br />

Makog<strong>on</strong>, Yu.F., 95<br />

Maksimenko, E.S., 1133<br />

Mandarov, A.A., 615<br />

Mangerud, J., 194<br />

Manikian, V., 1301,1422<br />

Marciniak, K., 406,499<br />

Marks, L., 84<br />

Marsh, P., 618<br />

Martel, C.J., 1426<br />

Mas<strong>on</strong>, OK., 622<br />

Matsuda, Kyou, 143<br />

Maximova, L.N., 102<br />

Maximyak, R.V., 11 86 .<br />

McHattie, R., 1292<br />

McRoberts, E.C., 1137,1247<br />

Melnikov, E.S., 208<br />

Melnikov, P.I., 1298<br />

Melnikov, V.P., 815, 1143<br />

Meng, Fanjin, 143 1<br />

Michel, E, 33<br />

Migala, K., 44<br />

Miller, R.D., 436<br />

Mirenburg, Yu.S., 1336<br />

M<strong>on</strong>issey, L.A., 213<br />

Moskalenko, N.G., 165<br />

Murray, B.M., 819<br />

Murray, D.F., 819<br />

Myrvang, A.M., 1435<br />

Na, Wenjie, 1160<br />

Naidenok, Lye., 1307<br />

Nakano, Yoshisuke, 412<br />

Nels<strong>on</strong>, F.E., 819<br />

Neukirchner, R. J., 1147<br />

Nevecherya, V.L., 1152<br />

Nidowicz, B., 1301<br />

Nieminen, P., 872<br />

Niewiarowski, W., 824<br />

Nikiforov, V.V., 1403<br />

Nix<strong>on</strong>, J.F., 13 18<br />

Nyberg, R., 89<br />

Ohrai, T., 522<br />

Olovin, B.A., 418<br />

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Ostendorf, B., 574<br />

Osterkamp, T.E., 355<br />

Ostroumov, V.E., 425<br />

Outcalt, S.I., 819<br />

Omuf, J.-Cl., 830<br />

Palmer, A.C., 1324<br />

Pan, Baotian, 268<br />

Pancza, A., 830<br />

Panday, S., 61<br />

Pang, Guoliang, 1024<br />

Parameswarm, V.R., 1156<br />

Parmuzin, S.Yu., 1307<br />

Parmuzina, O.Yu., 906<br />

Pathak, R.C., 127 1<br />

Pavlov, A.S., 431<br />

Pavlov, A.V., 165,218<br />

Pelfini, M., 678<br />

Pelletier, Y., 113<br />

Perelmiter, A.D., 1307<br />

Peretrukhin, N.A., 1446<br />

Perfect", E.,436<br />

Perlshtein, G.Z., 1417, 1450<br />

Petrov, E.E., 1397<br />

Pdrez, EL., 834<br />

Phetteplace, G., 1262<br />

Phukan, A,, 1018<br />

Pietrucien, C., 628<br />

Pika, J., 937<br />

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Piper, D., 370<br />

Pissart, A., 840<br />

Pizhankova, Ye.I., 313<br />

Podborny, Y.Y., 1531<br />

Podenko, L.S., 1143<br />

Pokl<strong>on</strong>ny, S.A., 381<br />

Pollard, W.H., 224<br />

Polunovsky, A.G., 1454<br />

Popov, A.I., 230,846<br />

Porturas F., 1459<br />

Postawko, S.E., 284<br />

Prabhakar, V., 1262<br />

Przybylak, R., 406,499<br />

Pullan, S.E., 949<br />

Puschmann, O., 1206<br />

Pushko, G.I., 1531<br />

Pustovoit, G.P., 1102<br />

Qiu, Guoqing, 442<br />

Qu, Xiangmin, 1526<br />

Rampt<strong>on</strong>, V.N., 850<br />

Mv, A., 89<br />

Ratkje, S.K., 344<br />

Razbegin, V.N., 11 86<br />

Razumov, V.V., 459<br />

Regairaz, M.C., 856<br />

Repelewska-Pekalowa, J., 448,754<br />

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Riddle, C.H., 1312,1318<br />

Riseborough, D.W., 633<br />

Rodzik, J., 543<br />

Rogov, V.V., 381<br />

Romanov, V.P., 454<br />

Romanovsky, N.N., 233,1000<br />

Romanovsky, V.Ye., 102<br />

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Rosenbaum, G.E., 230<br />

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Sasa, Gaichirou, 143<br />

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Schmid, W., 764<br />

Schmidlin, T.W., 241<br />

Schwartsev, S.L., 462<br />

Seguin, M.K., 113, 148, 199,980<br />

Sellmann, P., 927<br />

Sellmann, P.V., 988<br />

Sengupta, M., 1476<br />

SeppQfi, M., 183,862<br />

Sergeyev, D.O., lo00<br />

Seversky, E.V., 247<br />

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Shang, Jih<strong>on</strong>g, 1520<br />

Shchobolev, A.G., 533<br />

Sheng, Wenkun, 442<br />

Shevchenko, L.V., 396<br />

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Shirnizu, Osamu, 143<br />

Shramkova, V.N., 1106<br />

Shui, Tieling, 1160<br />

Shur, Yu.L., 867<br />

Shvetsov, P.F.,805<br />

Sinha, A.K., 994,1476<br />

Sirikiewicz, M., 824<br />

Skowr<strong>on</strong>, R., 628<br />

Slepak, M.E., 11 86

Slepak, M.E., 1186<br />

Sletten, R.S., 467,478<br />

Smiraglia, C., 678,712<br />

Smith, M.W., 473,700<br />

Solomatin, VI., 484<br />

S<strong>on</strong>e, Toshio, 253<br />

S<strong>on</strong>g, Baqing, 1482<br />

S<strong>on</strong>g, Zhengyuan, 1026<br />

Stelzer, D.L., 1165<br />

Stoker, K.J.L., 73<br />

Stubbs, C.W., 770<br />

Sun, Jianzh<strong>on</strong>g, 107<br />

Sun, Kehan, 1482<br />

Sun, Weimin, 11 81<br />

Sun, Yuliang, 1171<br />

Szczepanik, W., 406<br />

Takahashi, Nobuyuki, 253<br />

Ter-Martirosyan, Z.G., 533<br />

Theriault, A., 1175<br />

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Thomas, J.E., P.E., 1488<br />

Threlfall, J.L., 558<br />

Tian, Deting, 1212,1494<br />

Tice, A.R., 412,473<br />

Timopheev, E.M., 1407<br />

Titkov, S.N., 259<br />

T<strong>on</strong>g, Changjiang, 11 8 1<br />

T<strong>on</strong>g, Zhiquan, 1520<br />

Topekha, A.A., 1446<br />

Tremblay, C., 1500<br />

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Trombotto, D., 263<br />

Trush, N.I., 274<br />

Tsibulsky, V.R.; 218<br />

Tu, Guangzh<strong>on</strong>g, 61<br />

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Ugarov, I.S., 615<br />

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Van Huissteden, J., 876<br />

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Vandenberghe, J., 876<br />

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Vaskelainen, J., 1466<br />

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Vita, C.L., 1330<br />

Vitek, J.D., 744<br />

Volchenkoc, S.Yu., 233<br />

Volkova, V.P., 233,659<br />

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Wang, Bingcheng, 1024<br />

Wang, G<strong>on</strong>gshan, 1507<br />

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Wag, Jianguo, 1014,1341<br />

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Wang, Wenbao, 1515<br />

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Xu, Ruiqi, 1024<br />

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Xu, Xiaozu, 5 16<br />

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Yang, Zhengniang, 650<br />

Yarmak Jr., E., 1277<br />

Yazynin, O.M., 320<br />

Ye, Bayou, 1520<br />

Yershov, E.D., 274,528<br />

Yershov, V.D., 528<br />

Yian, Weijun, 1341<br />

Yu, Bofang, 1526<br />

Yu, Ch<strong>on</strong>gyun, 11 8 1<br />

Zabolotnik, S.I., 278<br />

Zaitsev, V.N., 233<br />

Zakharov, Y.E, 1531<br />

Zamolotchikova, S.A., 237,274<br />

Zaretsky, Yu.K., 533<br />

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Zavodovski, A.G., 1143<br />

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Zhang, Weixin, 903<br />

Zhang, Xing, 1026<br />

Zheng, Kaiwen, 442<br />

Zheng, Qipu, 656<br />

Zhigarew, L.A., 906<br />

Zhou, Youcai, 1358<br />

Zhu, Cheng, 724<br />

Zhu, Qiang, 1196<br />

Zhu, Yuanlin, 1200<br />

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Zvyagintsev, D.C., 749<br />

Zykov, Yu.D., 537

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