an engineering geological characterisation of tropical clays - GBV

iii
Chapter 8. Distribution of index and strength properties in black clays 155
8.1 Natural moisture content 155
8.2 Liquid limit 158
8.3 Plasticity index 161
8.4 Linear shrinkage 164
8.5 Free swell 166
8.6 Clay and fine fraction 168
8.7 Shear strength 173
Chapter 9. Implications of index/ engineering properties of black clays and red soils
on construction practice 176
9.1 Atterberg limits and other index parameters 176
9.2 Grain size distribution 177
9.3 Shear strength parameters 177
9.4 Consolidation-settlement characteristics 178
9.5 Percentage swelling and swelling pressure effects 180
Chapter 10. Correlation of index properties 181
10.1 Linear shrinkage and plasticity index 181
10.2 Liquid limit and plasticity index 187
10.3 Liquid limit and linear shrinkage 191
10.4 Free swell and other index properties 194
10.5 Clay fraction and linear shrinkage, free swell 198
Chapter 11. Conclusions 200
Chapter 12. Recommendations 207
References
Appendices
Appendix A. Results of oedometer consolidation tests
Appendix B. Results of swelling tests on black clays
Appendix C. Results of swelling tests on black clays
Appendix D. Distribution/ variation of index and engineering properties of
black clays in Nairobi area
Appendix E. Geotechnical soil map of Nairobi area
Figures
1.1 Location map of Nairobi city and study area 3
3.1 Geology: relative position of Great Rift Valley, extent of early lava flows and
ages of rock formations in Nairobi area 22-23
4.1 Site investigation/ sampling scheme employed for black clays in this study 31
4.2 Field depth sounding results for black clays and red soils 35
4.3 Contoured depth variations in black clays and red soils 36
4.4 Block diagrams of depth variations in black clays and red soils 37