an engineering geological characterisation of tropical clays - GBV

158
The distribution and variation of natural moisture content at depths of less than 0,50m across
the study area are characterised by a maximum and minimum of 34% and 18%, giving a range
of 16% (Table 8.1). Also characteristic are median, mode and mean values of 23% as well as
a standard deviation of 3,37 and variance of 11,36. The distribution is similar at depths of
0,50m and greater, with maximum and minimum values of 32% and 17% giving a range of
15% (Table 8.1). However, a slight increase in moisture content with depth of soils occurs
(due to reduced drying effects), and is reflected by a median of 25%, mode of 29% and mean
of 25%. Also calculated for this depth are a standard deviation of 3,56 and a variance of
12,69.
The variation of natural moisture content of soils at the two depth intervals across the study
area is generally similar, so that the two sets of data give a covariance of 9,71 and a strong
correlation of 0,83 (Table 8.1).
The upper 50cm of red soils were found to exhibit a relatively elevated moisture content of
38-39%, most probably a result of recent rainfall. However, depths greater than 0,50m are
generally characterised by a moisture content of 24-26%.
8.2 Liquid limit
The distribution of liquid limit values across the study area is presented in Figures (8.3a & b),
which show a concentration about a mean of 84% and 86%, respectively.
Liquid limit variation; < 0,50m depth
Liquid limit (%)
100
90
80
70
60
50
40
30
20
10
0
0 2000 4000 6000 8000 10000 12000
Distance along profile (m)
Profile A
Profile B
Profile C
Profile D
Profile E
Figure 8.3a. Liquid limit variation across the study area for the depth of less than
0,50m (north-south distance: 4000 m).