an engineering geological characterisation of tropical clays - GBV

163
(8.6). The few isolated patches of relatively low plasticity values imply areas of increasingly
lateritic clays and/ or swampy environments .
PI%
Plasticitx index (PI) variation (< 0,5m)
1°19´S 41 54 45 43 47
4000
(m)
Profile distance (m)
46
3000
47 48 44 39 47 47 46
47 47 48 43 47 49 44
2000
West
48 48 47 49 46 48 47
1000
1°21.5´S48 48 48 41 49 49 49
0
47
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 (m)
36°49´E
South
Profile distance (m) 36°55´E
49
48.5
48
47.5
47
46.5
%
46
45.5
45
44.5
44
43.5
43
42.5
42
41.5
41
40.5
Plasticity index (PI) variation (> 0,5m)
1°19´S 39 55 47 39 49
4000
(m)
Profile distance (m)
48 49 51 49 45 51 50 49
3000
50 50 49 39 49
2000
48 47
West
50 49 49 49 47 48 48
1000
1°21.5´S48 47 48 48 48 43 50
0
47
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 (m)
36°49´E
South Profile distance (m)
36°55´E
41.5
42
42.5
43
43.5
44
44.5
45
45.5
46
46.5
47
47.5
48
48.5
49
49.5
50
PI%
50.5
Figure 8.6. A contoured representation of the distribution and variation of plasticity index
values in black clays.
The two depth intervals show more or less similar plasticity values and parameters, implying
a more or less uniform and/ or homogeneous character of the black clays, both across the
study area and with depth. This is further evidenced by a covariance of 5,60 and a fairly
strong correlation of 0,63 between the two sets of data obtained for the two depth intervals
(Table 8.1).
The plasticity indices obtained for the red soils in this study are relatively low, ranging from
18-22%.