an engineering geological characterisation of tropical clays - GBV

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strongly suggest that the whole soil thickness of black clays of the current study area is more
or less homogenous and uniform in terms of linear shrinkage and, possibly, other index and/or
engineering properties.
Linear shrinkage values obtained for the red soils are comparatively low and range from 10-
11%.
8.5 Free swell
The distribution of free swell values along the five field profiles in this study is presented in
Figure (8.9). Profiles A, B, C, D and E show free swell values of 115-135%, 120-145%, 105-
130%, 110-130 and 120-135% for depths of less than 0,50m concentrated about a mean value
of 126%; and 100-145%, 120-145%, 110-145%, 130-145% and 120-145% for depths 0f 0,5m
and over, concentrated about a mean value of 132%, respectively. The complete set of data is
given in Table (8.1).
Distribution of free swell values at a depth of less than 0,50m across the study area is
characterised by minimum and maximun values of 105% and 145% respectively, giving a
range of 40%, median and mode of 125%, mean of 126% as well as a standard deviation of
8,26 and variance of 68,25.
Free swell variation; < 0,50m depth
Free swell (%)
160
140
120
100
80
60
40
20
0
0 2000 4000 6000 8000 10000 12000
Distance along profile (m)
Profile A
Profile B
Profile C
Profile D
Profile E
Figure 8.9a. Free swell variation across the study area at depths of less than
0,5m (north-south distance: 4000 m).
On the other hand, black clays at depths of 0,50m and over exhibit free swell values of
between 100% and 145% with a range of 45%, across the study area. A median and mode of
135%, mean of 132%, standard deviation of 11,33 and variance of 128,28 were also
calculated for the depth.