an engineering geological characterisation of tropical clays - GBV

134
Black clays
0,45
0,43
n = 6
Compression index Cc
0,41
0,39
0,37
0,35
0,33
0,31
0,29
Cc = 0,0099(122-LL)
R 2 = 0,73
Cc vs LL
0,27
0,25
75 80 85 90 95
Liquid limit LL (%)
Figure 7.23. Correlation between laboratory determined liquid limits and
compression indices for black clays.
Black clays and red soils
Compression index Cc
0,5
0,4
0,3
0,2
0,1
0
n = 9
Cc = 0,0016(308-LL)
R 2 = 0,34
Cc vs LL
0 20 40 60 80 100
Liquid limit, LL (%)
Figure 7.24. Correlation between laboratory determined liquid limits and
compression indices for black clays and red soils.
Calculated values of compression index for black clays, cc(b), as well as for combined black
clays and red soils, cc(br), as derived from laboratory measured liquid limits using the
relationships of Equations (7.47 & 7.48) are presented in Table (7.16); alongside laboratory
determined compression indices, cc. The strength of correlation between so calculated and
laboratory measured compression indices are strong (R = 0,85) for the black clays alone; and
only moderate (R = 0,58) for combined black clays and red soils. However, values of
compression indices calculated from laboratory liquid limits using Skempton´s relationship,
i.e. ( Cc(sk) = 0,009(LL-10) are generally overestimated with respect to laboratory determined
compression indices for black clays (Table 7.16). The overestimation could be accounted for