an engineering geological characterisation of tropical clays - GBV

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Plasticity index variation; < 0,50m depth
Plasticity index (%)
60
50
40
30
20
10
Profile A
Profile B
Profile C
Profile D
Profile E
0
0 2000 4000 6000 8000 10000 12000
Distance along profile (m)
Figure 8.5a. Plasticity index variation across the study area for the depth
of less than 0,50m (north-south distance: 4000 m).
Profiles A, B, C, D and E show plasticity indices of 41-54%, 43-49%, 41-49%, 39-48% and
46-49% for depths of less than 0,50m; and 39-55%, 39-50%, 43-50%, 45-51% and 47-50%
for depths of 0,5m and greater, respectively.
Plasticity index variation; 0,50m and greater
60
Plasticity index (%)
50
40
30
20
10
Profile A
Profile B
Profile C
Profile D
Profile E
0
0 2000 4000 6000 8000 10000 12000
Distance along profile (m)
Figure 8.5b. Plasticity index variation across the study area for the depth of
0,50m and greater (north-south distance: 4000 m).
The plasticity index of soils is similarly distributed across the study area for both depths of
less than 0,50m and those of 0,50m and deeper, exhibiting maximum and minimum values of
54% and 39% with a range of 15%; and 55% and 39% with a range of 16%, respectively
(Table 8.1). Soil depths of less than 0,50m are also characterised by a median, mode and
mean value of 47%, as well as a standard deviation of 2,78 and variance of 7,74. Similar and
closely comparable parameters were calculated for depths of 0,50m and greater, in terms of
median, mode and mean values of 48%, 49% and 48%, respectively. A standard deviation of
3,28 and variance of 10,76 were also computed for the latter depth interval. A summary of
the distribution in the form of contour maps for the two depth intervals is presented in Fig.