an engineering geological characterisation of tropical clays - GBV

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86 7.1.3.2 Plastic limit Plastic limit tests were carried out in this study to determine the lowest moisture content at which the clay soils found are plastic. The tests were carried out according to British Standard (BS 1377: 1975, Test 3) and German Standard (DIN 18 122, Teil 1); by using a suitable amount of disturbed soil previously oven-dried (105 °C over a 12-24 hour period) and sieved to provide a homogeneous material. The testing method is shown in Plate (7.1) in which a uniform pressure was used to roll threads of a homogeneous soil paste between the fingers of one hand and a glass plate from about 6 mm diameter size until they just crumbled at about 3 mm diameter. The moisture content of the threads at the first crumbling point was determined. In this study, a total of three separate moisture content determinations of the threads was carried out for each soil sample and an average value calculated and taken as the plastic limit (PL) of the soil. Results of plastic limit of soils obtained in this study are reported to the nearest whole number (1%) alongside those of liquid limit and plasticity index in Table (7.2). Plate 7.1. Plastic limit determination in this study. 7.1.3.3 Liquid limit Liquid limit determination of soils in this study was carried out using the Casagrande apparatus (Casagrande, 1958), and in accordance with British Standard (BS 1377: 1975, Test 2(B)) and German Standard (DIN 18 122, Teil 1). The apparatus used in this study is shown in Plate (7.2). The test involved applying bumps or blows to the cup of the apparatus so as to close a V-shaped groove cut in the middle of a homogeneous soil paste contained in the cup. The moisture content of the paste at which a total of 25 bumps closed the groove along a continuous distance of 10 mm was determined and recorded as the liquid limit (LL) of the soil.
87 Table 7.2. Results of index tests performed on black clays and red soils in this study. Profile Sample No. Wn (%) LL (%) PL (%) PI (%) Cr LI FS (%) LS (%) PI/LL class (BS 1377) Consistency SA1-30cm 31,6 78,2 37,2 41,1 1,136 -0,14 135 25 MV semi-solid A SA1-50cm 30 74,9 36,3 38,6 1,163 -0,16 100 23 MV semi-solid SA2-30cm 33,7 92,6 38,8 53,9 1,094 -0,09 135 27 CE semi-solid (black clays) SA2-70cm 34,1 90 36,3 53,7 1,04 -0,04 170 25 CV-CE semi-solid SA2-105cm 29,7 88,1 32,9 55,2 1,059 -0,06 120 26 CV semi-solid SA28-30cm 25,6 84,8 39,7 45,1 1,313 -0,31 125 25 MV-CV semi-solid SA28-50cm 26,8 88,5 41,3 47,2 1,307 -0,31 135 25 MV-CV semi-solid SA37-30cm 19,4 80,9 38,1 42,7 1,439 -0,44 115 24 CV semi-solid SA37-50cm 21,8 83,3 39,2 44,2 1,393 -0,39 115 26 CV semi-solid SA37-80cm 23,1 85,1 39,2 45,9 1,35 -0,35 115 26 CV semi-solid SA41-30cm 23 88,5 41,3 47,2 1,387 -0,39 135 26 CV semi-solid SA41-50cm 24,9 89,7 41,1 48,6 1,334 -0,33 120 24 CV semi-solid SB1-30cm 23 81,7 34,3 47,4 1,237 -0,24 125 23 CV semi-solid B SB1-50cm 26,7 83,7 36,1 47,6 1,197 -0,2 135 24 CV semi-solid SB1-70cm 29,7 89,9 39,1 50,8 1,187 -0,19 145 25 CV semi-solid (black clays) SB5-30cm 24 80,9 34 47 1,212 -0,21 120 23 CV semi-solid SB5-50cm 26,8 84,6 36,6 48 1,205 -0,2 135 24 CV semi-solid SB5-70cm 30,5 91,1 40,2 51 1,19 -0,19 145 26 CE semi-solid SB7-30cm 23,2 82,9 34,6 48,3 1,235 -0,23 130 24 CV semi-solid SB7-50cm 26,1 85,8 37 48,8 1,222 -0,22 135 24 CV semi-solid SB7-70cm 29,6 87 38,3 48,7 1,179 -0,18 140 25 CV semi-solid SB18-30cm 20 82,4 39,8 42,6 1,463 -0,46 120 23 MV-CV semi-solid SB18-50cm 20,1 72,4 33,6 38,8 1,346 -0,35 120 21 CV semi-solid SB27-30cm 21,6 85 38 47,1 1,348 -0,35 130 24 CV semi-solid SB27-50cm 22,2 87,7 39,2 48,5 1,352 -0,35 130 25 CV semi-solid SB31-30cm 23,4 86,9 38,1 48,8 1,3 -0,3 130 24 CV semi-solid SB31-50cm 22,9 86,1 37,6 48,4 1,304 -0,3 130 25 CV semi-solid SB41-30cm 23 88,8 44,6 44,1 1,491 -0,49 145 26 MV semi-solid SB41-50cm 24 90,7 43,6 47,1 1,415 -0,42 145 25 MV semi-solid SB42-30cm 22 87,6 43,8 43,8 1,499 -0,5 145 25 MV semi-solid SB42-50cm 21,3 91,1 44,5 46,6 1,498 -0,5 145 26 ME-CE semi-solid SC1-30cm 24,2 82 34,5 47,5 1,218 -0,22 125 23 CV semi-solid C SC1-50cm 25,9 84,9 36,7 48,2 1,224 -0,22 135 24 CV semi-solid SC5-30cm 23 83,1 34,7 48,4 1,24 -0,24 125 23 CV semi-solid (black clays) SC5-50cm 25,1 83,5 36,2 47,2 1,236 -0,24 135 24 CV semi-solid SC9-30cm 24,8 83,6 35,6 48 1,223 -0,22 130 24 CV semi-solid SC9-50cm 26 84,6 37,1 47,5 1,233 -0,23 135 24 CV semi-solid SC17-30cm 21,2 75,7 34,7 41 1,329 -0,33 105 25 CV semi-solid SC17-50cm 22 80,7 32,5 48,2 1,219 -0,22 110 24 CV semi-solid SC25-30cm 26,1 87,9 39 48,9 1,265 -0,27 125 25 CV semi-solid SC25-50cm 25,8 88,6 41 47,6 1,321 -0,32 145 25 MV semi-solid SC29-30cm 20,7 81,5 32,2 49,3 1,235 -0,23 110 25 CV semi-solid SC29-50cm 20,4 80,2 36,8 43,4 1,379 -0,38 110 26 CV semi-solid SC33-30cm 20,3 81,7 32,5 49,1 1,248 -0,25 120 25 CV semi-solid SC33-50cm 21,4 82,9 33 49,9 1,233 -0,23 120 26 CV semi-solid SC41-30cm 17,7 85,2 37,8 47,4 1,422 -0,42 125 29 CV semi-solid SC41-50cm 17,2 83,6 36,6 47 1,412 -0,41 125 29 CV semi-solid
Page 1 and 2:
AN ENGINEERING GEOLOGICAL CHARACTER
Page 3 and 4:
i Contents Page Acknowledgements Su
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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
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ix Acknowledgements I would like to
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1 Chapter 1 Introduction 1.1 Scope
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Figure1.1 Map of Nairobi region sho
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5 Plates 1.2 (a) & (b) Strong shrin
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7 Available literature in the form
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9 slopes. The northern boundary bet
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11 1.6 Climate The Nairobi area and
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13 marked daily range of relative h
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15 Chapter 2 Previous works 2.1 Sum
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17 Table 2.1 Stratigraphic correlat
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19 Chapter 3 Geology 3.1 Introducti
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21 metamorphic minerals sillimanite
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25 and prismatic apatite occur as a
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27 Table 3.2 Chemical analyses of s
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29 caused by partial segregation of
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32 could otherwise lead to erroneou
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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: 85 According to Johnson and Degraff
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
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137 Black clays and red soils Swell
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139 Testing procedure involved cutt
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141 Black clays Swelling pressure S
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143 Black clays: P (kPa) vs S (%) P
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145 The same relationship is repres
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147 Alternatively, percentage swell
Page 161 and 162:
149 Combined sample results: S % vs
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151 Black clays: Greek method P% =
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153 partly produced by effects of w
Page 167 and 168:
155 Chapter 8 Distribution of index
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157 the study area, respectively. R
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159 Liquid limit variation; 0,50m a
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161 Liquid limit (LL) variation (>
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163 (8.6). The few isolated patches
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165 Similarly, soil thicknesses of
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167 Free swell variation; 0,50m dep
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169 fraction at the two depth inter
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171 Variation of fines (%), < 0,50m
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173 %coarse % coarse fraction varia
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175 1°19´S 22 Shear angle variati
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177 9.2 Grain size distribution The
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179 rapid dissipation of pore water
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Chapter 10 181 Correlation of index
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183 Black clays; plasticity index/
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185 On the other hand, laboratory m
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187 Red clays; measured/ calculated
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189 These two relationships could b
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191 Diagram: PImeasured/ PIcalculat
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193 Table 10.5, continued. Calculat
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195 Table 10.6. Calculated and labo
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197 The swelling capability in term
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199 Free swell/ clay fraction Free
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201 There has also been a decrease
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203 PI = 1,88*LS A comparison of pl
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205 cc = 0,0099(122-LL) for black c
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207 Chapter 12 Recommendations Anal
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209 cc = 0,0099(122-LL) for black c
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211 References Abebe, S. T., 2002.
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213 Galster, R.W., 1977. A system o
Page 227 and 228:
215 Mitchell, J.K., 1993. Fundament
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217 ------,1964. Long term stabilit
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Appendix A: Oedometer consolidation
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Table A7. Consolidation parameters
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Results of swelling tests on black
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Appendix D Distribution/ variation
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4000 3000 2000 Distance (m) 1000 We
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4000 3000 2000 1000 Distance (m) We
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4000 3000 2000 Distance (m) 1000 We
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4000 3000 2000 Distance (m) 1000 We
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4000 3000 2000 Distance (m) 1000 We
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4000 3000 2000 Distance (m) 1000 We
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4000 3000 2000 Distance (m) 1000 We
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4000 3000 2000 Distance (m) 1000 We
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4000 3000 2000 Distance (m) 1000 We
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4000 3000 2000 Distance (m) 1000 We
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Appendix E Geotechnical soil map of
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