an engineering geological characterisation of tropical clays - GBV

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16 possible use as building stone and in the manufacture of bricks and tiles, limes and cements. His findings were published in a report issued by the Imperial Institute (1926). Bailey Willis (1936) described the Kikuyu scarp to the west of Nairobi, the warped peneplain around Nairobi and the grid – faulting that has affected the volcanic rocks of the Rift valley region and western parts of Nairobi area. Saggerson and Baker (1965) also investigated and described, among others, the Kikuyu scarp and the warped peneplain in the neighbourhood of Nairobi area. Campbell Smith (1931) described and classified the trachytes and phonolites of Nairobi and its surroundings after examining and analysing a number of rock specimens collected from the areas. His findings were published and incorporated in a report. Bowen visited Kenya in the 1930´s and made an excursion into the Rift Valley. He also collected specimens of volcanic rocks from other parts of the country, including Nairobi and the present study area. In 1937, he published the results of his studies in a paper in which he illustrated his experimental work with personal observations on the lavas. The nature of alkali – feldspars in certain Kenyan rocks, including the Kapiti phonolite was investigated by Häkli (1960). The specimens of Kapiti phonolite had been previously collected by a Finnish Expedition in 1952 from the Stony Athi River and Nairobi, including some parts of the study area. Williams (1967) outlined the geology of Nairobi and its surroundings, in its regional setting. Various lavas have also been collected from the Nairobi succession and dated (Baker et al, 1988). Curtiss, Evernden and Miller of the University of California, USA, carried out K/Ar – age dating on rock specimens collected from the Nairobi region. The volcanic rocks were found to be Upper Miocene to Pleistocene in age (Evernden et al, 1964). Other studies involving Nairobi and covering the present study area include palaeomagnetic studies by staff of the Department of Physics, University of Nairobi (Mussett et al, 1964- 1965); and the monitoring and detection of seismic activities and possible associated earth movements, by the Seismology Section, Department of Geology, University of Nairobi (1990-2002). A number of other geological investigations have been carried out in Nairobi and its environs, including the study area; but they are recorded as unpublished works by the Mines and Geological Department, Nairobi. Some of the unpublished works include those of Binge, Joubert, Pulfrey and Saggerson (Mines and Geological Department, Nairobi, 2001). Early works regarding detailed survey and study of soils of the Nairobi area and its environs were undertaken by Jones in 1952 and published in 1953. His works were later carried forward to completion by Scott, of the then East African Agriculture and Forestry Research Organisation. In his works, he described a variety of soils found as having developed under a wide range of climatic conditions (Scott, 1963). Other works in the study of soils were undertaken by Stephen, Bellis and Muir (1956), who investigated the nature of the black cotton soils overlying Nairobi phonolite in the Athi plains, with the purpose of establishing the cause for uneven growth of crops. They also noted that soils from Embakasi area, Nairobi, contained some minerals typical of metamorphic rocks.
17 Table 2.1 Stratigraphic correlation of rocks in the Nairobi region (Saggerson, 1991). SOUTH CENTRAL NORTH Kajiado Nairobi Kijabe (Matheson, 1966) (Saggerson, 1968) (Thompson, 1964) Soils, ashes, alluvium, Soils and ashes RECENT Soils loess, gypsiferous beds _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Longonot trachytes Trachytes U Lacustrine deposists xxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxx Sediments (Kandizi Valley) Pyroclastics PLEIST- Olorgesailie Upper Trachyte Division of xxxxxxxxxxxxxxxxx OCENE M Lake Beds rhyolites, trachyrhyolites Trachytes, Kijabe and obsidians ( with basalts, welded tuffs interbedded diatomites) _ _ _ _ _ _ _ _ _ _ __ _ _ xxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxx Upper Trachyte Division of: Pyroclastics and Welded tuffs & pyroclastics, Laikipian basalts (Sattima Series/ L Laikipian lavas) Orthophrye trachyte Orthophrye trachyte, and Limuru trachytes Alkali trachyte xxxxxxxxxxxxxxxxxxxxxxxxxxxxx Middle Trachyte Division: Ol Keju Nero basalts Tigoni & Karura trachyte xxxxxxxxxxxxxxxxxxxxxxxxx Ruiru Dam trachyte Ol Esayeti volcanics Kabete trachyte Sattima Series Kerichwa valley tuffs Kerichwa Valley tuffs PLIOCENE and Ol Doinyo Narok Ol Esayeti volcanics and agglomerate _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Lower Trachyte Division: Olorgesailie Ngong volcanics Volcanic Series Ol Doinyo Narok agglomerate Laikipian lavas Ololua trachyte Nairobi / Kiambu trachytes Mbagathi trachyte Sediments & tuffs Nairobi & Kandizi phonolites Mbagathi phonolitic trachytes x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x- Upper Athi tuffs Athi tuffs and Lake Beds _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Lower Trachyte Division: Simbara basalt MIOCENE Kapiti phonolite Kapiti phonolite Simbara Series _________________________ _____________________________ _____________________ PRECAMB- Basement System Metamorphic rocks of the RIAN Mozambique Belt not exposed xxx Faulting _ _ _ Erosion surface ___ Major unconformity
Page 1 and 2: AN ENGINEERING GEOLOGICAL CHARACTER
Page 3 and 4: i Contents Page Acknowledgements Su
Page 5 and 6: iii Chapter 8. Distribution of inde
Page 7 and 8: v 7.29 - 7.33 Correlation between s
Page 9 and 10: vii 136 139 7.13 Compressibility cl
Page 11 and 12: ix Acknowledgements I would like to
Page 13 and 14: 1 Chapter 1 Introduction 1.1 Scope
Page 15 and 16: Figure1.1 Map of Nairobi region sho
Page 17 and 18: 5 Plates 1.2 (a) & (b) Strong shrin
Page 19 and 20: 7 Available literature in the form
Page 21 and 22: 9 slopes. The northern boundary bet
Page 23 and 24: 11 1.6 Climate The Nairobi area and
Page 25 and 26: 13 marked daily range of relative h
Page 27: 15 Chapter 2 Previous works 2.1 Sum
Page 31 and 32: 19 Chapter 3 Geology 3.1 Introducti
Page 33: 21 metamorphic minerals sillimanite
Page 37 and 38: 25 and prismatic apatite occur as a
Page 39 and 40: 27 Table 3.2 Chemical analyses of s
Page 41 and 42: 29 caused by partial segregation of
Page 44 and 45: 32 could otherwise lead to erroneou
Page 46 and 47: 34 The red soils in this study occu
Page 48 and 49: 36 17 16 15 14 13 12 11 10 9 8 7 6
Page 50 and 51: 38 4.4 Vane test 4.4.1 Introduction
Page 52 and 53: 40 Table 4.1 Classification of soft
Page 54 and 55: 42 The variation of vane shear stre
Page 56 and 57: 44 And thirdly, the field vane appa
Page 58: 46 horizon, most probably a result
Page 61 and 62: 49 The red friable clays on the who
Page 63 and 64: 51 Results of chemical analyses of
Page 65 and 66: 53 Results of previous soil classif
Page 67 and 68: 55 neighbouring metamorphic areas a
Page 69 and 70: 57 Table 5.10. Profile description
Page 71 and 72: 59 The presence of BaO in the red a
Page 73 and 74: 61 resulted most probably from supp
Page 75 and 76: 63 800 Impulse 700 600 500 SC 17 -5
Page 77 and 78: 65 sericite and chlorite (see next
Page 79 and 80:
67 Q: Quartz (1%) H: Haematite K: K
Page 81 and 82:
69 Plate 6.3. K-feldspar phenocryst
Page 83 and 84:
71 The trachytes generally show a r
Page 85 and 86:
73 Plate 6.16. Organic matter (rema
Page 87 and 88:
75 Plate 6.24. Solution pores/ cavi
Page 89 and 90:
77 Plate 6.29. Iron concretion with
Page 91 and 92:
79 The CS-225 is a micro-processor
Page 93 and 94:
81 The red soils generally exhibit
Page 95 and 96:
83 Chapter 7 Laboratory soils index
Page 97 and 98:
85 According to Johnson and Degraff
Page 99 and 100:
87 Table 7.2. Results of index test
Page 101 and 102:
89 Plate 7.2a. Apparatus for liquid
Page 103 and 104:
91 Activity chart Plasticity index
Page 105 and 106:
93 Table 7.3 (continued). Atterberg
Page 107 and 108:
95 where 7.1.4.4 Results V = volume
Page 109 and 110:
97 A standard classification of soi
Page 111 and 112:
99 Table 7.6. Viscosity and density
Page 113 and 114:
101 Table 7.7, continued. Results o
Page 115 and 116:
103
Page 117 and 118:
105 Plate 7.7a. Shear testing showi
Page 119 and 120:
107 Shear stress / Displacement Cur
Page 121 and 122:
109 Table 7.10. Distribution and/ o
Page 123 and 124:
111 illustrated in Figures 7.6, 7.7
Page 125 and 126:
113 Black clays Cohesion c´ (kN/m
Page 127 and 128:
115 7.4 Oedometer consolidation tes
Page 129 and 130:
117 The compound coefficient, K/ρw
Page 131 and 132:
119 Primary consolidation is a time
Page 133 and 134:
121 where w (%) = moisture content
Page 135 and 136:
123 Relationships between values of
Page 137 and 138:
125 Plate 7.8. Oedometer consolidat
Page 139 and 140:
127 Cumulative log-time/settlement
Page 141 and 142:
129 Ranges of values of coefficient
Page 143 and 144:
131 is most probably due to the ten
Page 145 and 146:
133 The results of correlation show
Page 147 and 148:
135 by differences in lithology, mi
Page 149 and 150:
137 Black clays and red soils Swell
Page 151 and 152:
139 Testing procedure involved cutt
Page 153 and 154:
141 Black clays Swelling pressure S
Page 155 and 156:
143 Black clays: P (kPa) vs S (%) P
Page 157 and 158:
145 The same relationship is repres
Page 159 and 160:
147 Alternatively, percentage swell
Page 161 and 162:
149 Combined sample results: S % vs
Page 163 and 164:
151 Black clays: Greek method P% =
Page 165 and 166:
153 partly produced by effects of w
Page 167 and 168:
155 Chapter 8 Distribution of index
Page 169 and 170:
157 the study area, respectively. R
Page 171 and 172:
159 Liquid limit variation; 0,50m a
Page 173 and 174:
161 Liquid limit (LL) variation (>
Page 175 and 176:
163 (8.6). The few isolated patches
Page 177 and 178:
165 Similarly, soil thicknesses of
Page 179 and 180:
167 Free swell variation; 0,50m dep
Page 181 and 182:
169 fraction at the two depth inter
Page 183 and 184:
171 Variation of fines (%), < 0,50m
Page 185 and 186:
173 %coarse % coarse fraction varia
Page 187 and 188:
175 1°19´S 22 Shear angle variati
Page 189 and 190:
177 9.2 Grain size distribution The
Page 191 and 192:
179 rapid dissipation of pore water
Page 193 and 194:
Chapter 10 181 Correlation of index
Page 195 and 196:
183 Black clays; plasticity index/
Page 197 and 198:
185 On the other hand, laboratory m
Page 199 and 200:
187 Red clays; measured/ calculated
Page 201 and 202:
189 These two relationships could b
Page 203 and 204:
191 Diagram: PImeasured/ PIcalculat
Page 205 and 206:
193 Table 10.5, continued. Calculat
Page 207 and 208:
195 Table 10.6. Calculated and labo
Page 209 and 210:
197 The swelling capability in term
Page 211 and 212:
199 Free swell/ clay fraction Free
Page 213 and 214:
201 There has also been a decrease
Page 215 and 216:
203 PI = 1,88*LS A comparison of pl
Page 217 and 218:
205 cc = 0,0099(122-LL) for black c
Page 219 and 220:
207 Chapter 12 Recommendations Anal
Page 221 and 222:
209 cc = 0,0099(122-LL) for black c
Page 223 and 224:
211 References Abebe, S. T., 2002.
Page 225 and 226:
213 Galster, R.W., 1977. A system o
Page 227 and 228:
215 Mitchell, J.K., 1993. Fundament
Page 229 and 230:
217 ------,1964. Long term stabilit
Page 231 and 232:
Appendix A: Oedometer consolidation
Page 233 and 234:
Table A7. Consolidation parameters
Page 235 and 236:
Results of swelling tests on black
Page 237 and 238:
Appendix D Distribution/ variation
Page 239 and 240:
4000 3000 2000 Distance (m) 1000 We
Page 241 and 242:
4000 3000 2000 1000 Distance (m) We
Page 243 and 244:
4000 3000 2000 Distance (m) 1000 We
Page 245 and 246:
4000 3000 2000 Distance (m) 1000 We
Page 247 and 248:
4000 3000 2000 Distance (m) 1000 We
Page 249 and 250:
4000 3000 2000 Distance (m) 1000 We
Page 251 and 252:
4000 3000 2000 Distance (m) 1000 We
Page 253 and 254:
4000 3000 2000 Distance (m) 1000 We
Page 255 and 256:
4000 3000 2000 Distance (m) 1000 We
Page 257 and 258:
4000 3000 2000 Distance (m) 1000 We
Page 259 and 260:
Appendix E Geotechnical soil map of
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