an engineering geological characterisation of tropical clays - GBV

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136
139
7.13 Compressibility classification of black clays and red soils 129
7.14 Rates of consolidation-settlement of black clays and red soils 130
7.15a Compression indices, Cc, and compressibility classification of clay soils 132
7.15b Results of compression indices correlated with Atterberg limits 133
7.16 Correlation between calculated and laboratory derived compression indices 135
7.17 Classification of black clays and red soils based on coefficient of secondary
compression 136
7.18 Results of swell indices for black clays and red soils correlated with Atterberg
limits and free swell
7.19 Results of swelling pressures for black clays, alongside corresponding
index properties and clay mineralogy
7.20 Percentage swelling of black clays under various load decrements 142
7.21 Relative degree of swelling of black clays under various loads 143
7.22 Classification of relative degree of swelling of black clays based on
percentage swelling 144
7.23 Percentage swelling of black clays under various load decrements (S% is in
relation to initial specimen height, Ho, i.e. 2 nd method in this study) 147
7.24 Classification of relative degree of swelling of black clays using the
newly derived/ 2 nd method 147
7.25 Computed values for estimating swelling characteristics of black clays
using the Greek method 150
8.1 Values of index properties of soils along field profiles in this study 156
8.2 Values of clay and fines fractions of soils along field profiles in this study 169
10.1 Calculated and laboratory measured values of plasticity index of black clays 181
10.2 Calculated and laboratory measured values of plasticity index of red soils 182
10.3 Calculated and laboratory measured plasticity indices of black clays 188
10.4 Calculated and laboratory measured plasticity indices of red soils 190
10.5 Calculated and laboratory measured linear shrinkage values of black clays
and red soils 192
10.6 Calculated and laboratory measured free swell values of black clays and
red soils 195
Plates
1.1 (a) & (b) New stone structures coming up in the study area 4
1.2 (a) & (b) Strong shrinkage cracks in black cotton soils during dry months 5
1.3 (a) & (b) Cracked and peeled-off asphalt on tarmac road giving way
to formation of pot holes in a zone of black clays in the Nairobi city centre 5
1.4 A slightly tilting building in a zone of black clays in the study area 6
1.5 (a) & (b) Light/ low rise buildings located in black clays with poor drainage 6
1.6 (a) & (b) Heavy constructed structures in a zone of black clays in
the study area 7
1.7 (a) & (b) View of the Great Rift Valley from its eastern flank, to the west of
Nairobi area 8
1.8 (a) & (b) Flat plains characterising areas of black cotton soils in this study 9
4.1 (a) & (b) Hand-dug excavation pits and undisturbed sampling in black clays 32
4.2 (a) & (b) Hand-dug excavation pits and undisturbed sampling in red soils 33