2 Volumes Final Proceedings - Washington 1984.pdf - IARC Research

29However, data did demonstrate that full annualsubroadway refreezing was occurring beneath thesepaved roadway sections in spite of the warm (-1°C)permafrost temperatures. Monitoring of thesesites was discontinued in 1960.The first insulated road embankment on permafrost,located near Chitina, Alaska, was constructedand instrumented in 1969, and has beenmonitored continually since that time, providingthe longest temperature data base for use in evaluatingthermal models. Since that time, additionalinstrumented roadway and railway embankmentshave been constructed and monitored in Alaska andCanada. Details of all such installations cannotbe given here, but Figure 1 and Table 1 shcw thelocations and references for significant experimentaldata pertinent to roads and railways overpermaf rest.Recently, three roadway sites in interiorAlaska have been painted white to masure the effectsof increased surface reflectance or albedoin reducing thaw-settlement problems. These sitesprovide a fair data base for predicting the performancebenefits of insulated embankments andother experimental features such as berms, aircoolingducts, and heat pipes, particularly inwarm permafrost. Increased field monitoring effortsare needed to masure the thermal effects ofculverts on embankmnt performance and the surfacetemperature effects of embankment slopes and slopevegetative covers, as well as the thermal stabilityof embankments overlying colder permafrost.constructed 60 years ago tends to verify this observation.Embankment drainage design considerations relatingto permafrost have not been studied in eufficient detail. So= roadway performance reportshave criticized designere for channeling flows intoculverts where cross-slope embankment routesintercept active-layer water drainage. No constructionmethods have been developed and testedthat will assure water percolation through embankmentswithout such channelization.Drainage culverts may act as embankmnt aircoolingducts or they may result in net warming,depending on seasonal air and water flows, snowcover, and so forth. Over a period of years, embanknlentsettlements and frost heaving may distortor displace culverts and make them non-functional.These therm1 aspects of culvert design have receivedessentially no research effort.A more detailed listing of research needs relatedto embankments on permafrost, recently developedby the U.S. Committee on Permafrost, istitled "Permafrost Research: An Assessment of FutureNeeds" (1983). According to this report, thehighest priority in permafrost research should begiven to developing improved methods of detectingpermafrost and ground ice and to mapping of criticalpermafrost parameters. The author shares thisview, because lack of accurate kncwledge of subsurfaceconditions prior to construction may bethe mjor problem facing the embankment designer.REFERENCESRESEARCH NEEDSBecause of the long thermal adjustuent periodthat often results from new embankment constructionover permafrost, thermal models are neededthat will economically analyze alternatives over aperiod of 20 years or more. In fact, in view ofthe forecasts of a major climatic warming trendexpected to occur in the Arctic as a result of the"greenhouse effect" due to increasing atmosphericcarbon dioxide levels, even longer periods ofthermal analysis are indicated. In areas of discontinuouspermafrost, acceleration of thawing bypreconstruction or construction operations may becomethe best design approach.Research is needed particularly to quantifythe therm1 effects of alternative embankmentside-slope surf aces and surf ace vegetation coversand to determine the role of snow-cover in embankraentperformance. Previous embankment researchstudies in discontinuous warm permafrost areashave demonstrated that progressive talik developmentbeneath snow-covered embankment slopes is amajor factor in embankment distress. Snow removalfrom roadway surfaces, by couparison, normally resultsin sufficient seasonal cooling to assure refreezingbeneath paved roadways, even in warm permafrostareas. Although railway embankments havenot been similarly instrunented and monitored, experienceIndicates that raihaya, because theylack a snow-free surface, should result in perpetualnet warming and ongoing thaw-settlement problemsin warm permafrost. Experience with continuedmaintenance on Alaska Railroad embankmntsBerg, R.L. and Esch, D.C., 1983, Effects of colorand texture on the surface temperature of asphaltconcrete pavements, & Proceedings ofthe Fourth International Conference on Permfrost,Fairbanks: Washington, D.C., NationalAcademy of Sciences, p. 57-61.Brown, J., 1983, Interaction of gravel fills, surfacedrainage, and culverts with permafrostterrain: Hanover, N.H. , U.S. Army Cold RegionsResearch and Engineering Laboratory, inpreparation.Brown, J. and Berg, R.L., eds., 1980, Environmentalengineering and ecological baseline investigationsalong the Yukon River-PrudhoeBay Haul Road: Hanover, N.H. , U. S. ArmyCold Regions Research and Engineering Laboratory,CRREL Report 80-19.Crory, PA., 1968, Bridge foundations in permafrostareas, Goldstream Creek, Fairbanks,Alaska: Hanover, N.H., U.S. Army Cold RegionsResearch and Engineering Laboratory,Technical Report 180.Crory, F.E., 1975, Bridge foundations in permafrostareas: Hanover, N.H., U.S. Army ColdRegions Research and Engineering Laboratory,Technical Report 266.Crory, F.E., 1983, Long-term foundation studies ofthree bridges in the Fairbanks area: Hanover,N.H., U.S. Army Cold Regions Researchand Engineering Laboratory, in preparation.Esch, LC., 1973, Control of permafrost degradationby roadway subgrade insulation, &Permafrost-- The North American Contribution tothe Second International Conference, Yakutsk: