146 Combined sample results: S (%) vs P (%) Loading P (%) 120 100 80 60 40 n = 25 P = -22,3Ln(S) + 100,8 R 2 = 0,99 Combined sample results Logarithmic 20 0 0 50 100 150 Swelling S (%) Figure 7.36a. Correlation between percentage swelling <strong>an</strong>d extent <strong>of</strong> loading using combined sample results <strong>of</strong> black <strong>clays</strong>. Combined sample results: S (%) vs P (%) 120 n = 25 100 P= -22,3Ln(S) + 100,8 Loading P (%) 80 60 R 2 = 0,99 Combined sample results 40 20 0 1 10 100 Swelling S (%) on Log scale Figure 7.36b. Correlation between percentage swelling (log scale) <strong>an</strong>d extent <strong>of</strong> loading using combined sample results <strong>of</strong> black <strong>clays</strong>.
147 Alternatively, percentage swelling <strong>of</strong> <strong>clays</strong> could be derived by expressing the swelling (S mm) which occurs under <strong>an</strong>y load decrement (P kPa) as a percentage <strong>of</strong> the initial thickness (Ho mm) <strong>of</strong> test specimen. Complete results <strong>of</strong> percentage swelling calculated for tested black clay samples using this second method are given in Appendix C. A more summarised representation <strong>of</strong> the results for the samples is given in Table (7.23). A derived classification <strong>of</strong> relative degree <strong>of</strong> swelling <strong>of</strong> black <strong>clays</strong> based on this new method is also given in Table (7.24). Table 7.23. Percentage swelling <strong>of</strong> black <strong>clays</strong> under various load decrements (S% is in relation to initial specimen height, Ho, i.e. 2 nd method). Sample No. P (kPa) SP = Pmax (kPa) P (%) S (mm) Smax (mm) S (%) Smax(%) 82,46 100 0,000 0,00 41,23 50 0,106 0,96 SA2-70cm 19,99 24 0,253 2,30 10,00 82,46 12 0,321 1,036 2,92 9,42 5,00 6 0,539 4,90 2,50 3 0,725 6,59 0,00 0 1,036 9,42 37,48 100 0,000 0,00 18,74 50 0,054 0,49 SB1-70cm 10,00 37,48 27 0,126 0,425 1,15 3,86 5,00 13 0,197 1,79 2,50 7 0,279 2,54 0,00 0 0,425 3,86 36,23 100 0 0,00 17,49 48 0,066 0,60 SC25/50cm 8,75 36,23 24 0,16 0,475 1,45 4,32 5,00 14 0,26 2,36 2,50 7 0,347 3,15 0,00 0 0,475 4,32 44,98 100 0 0,00 22,49 50 0,061 0,55 SC29-50cm 11,24 44,98 25 0,149 0,493 1,35 4,48 5,00 11 0,266 2,42 2,50 6 0,356 3,24 0,00 0 0,493 4,48 Average 50,29 0,607 5,52 Table 7.24. Classification <strong>of</strong> relative degree <strong>of</strong> swelling <strong>of</strong> black <strong>clays</strong> based on percentage swelling derived using the new/ 2 nd method (author, 2003). P (kPa) P (%) S (%) Swelling degree < 2,5 < 5 > 5 high 2,5-7,5 5-15 5 – 2,5 moderate 7,5-25,0 15-50 2,5- 0,5 low > 25,0 > 50 < 0,5 very low
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AN ENGINEERING GEOLOGICAL CHARACTER
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i Contents Page Acknowledgements Su
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iii Chapter 8. Distribution of inde
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v 7.29 - 7.33 Correlation between s
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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
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36 17 16 15 14 13 12 11 10 9 8 7 6
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38 4.4 Vane test 4.4.1 Introduction
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40 Table 4.1 Classification of soft
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42 The variation of vane shear stre
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44 And thirdly, the field vane appa
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46 horizon, most probably a result
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49 The red friable clays on the who
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51 Results of chemical analyses of
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53 Results of previous soil classif
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55 neighbouring metamorphic areas a
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57 Table 5.10. Profile description
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59 The presence of BaO in the red a
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61 resulted most probably from supp
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63 800 Impulse 700 600 500 SC 17 -5
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65 sericite and chlorite (see next
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67 Q: Quartz (1%) H: Haematite K: K
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69 Plate 6.3. K-feldspar phenocryst
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71 The trachytes generally show a r
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73 Plate 6.16. Organic matter (rema
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75 Plate 6.24. Solution pores/ cavi
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77 Plate 6.29. Iron concretion with
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79 The CS-225 is a micro-processor
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81 The red soils generally exhibit
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83 Chapter 7 Laboratory soils index
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85 According to Johnson and Degraff
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87 Table 7.2. Results of index test
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89 Plate 7.2a. Apparatus for liquid
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91 Activity chart Plasticity index
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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
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- 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
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- 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
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- 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
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- Page 197 and 198: 185 On the other hand, laboratory m
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- Page 205 and 206: 193 Table 10.5, continued. Calculat
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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
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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