an engineering geological characterisation of tropical clays - GBV

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A comparison of laboratory determined linear shrinkage values (LS measured) with those
computed (LSLL) according to Equation (10.18) reveals a very strong closeness. The two sets
of data are practically identical in terms of maximun and minimum values, the range as well
as the median, mode and mean values (Table 10.5). The two comparable standard deviations
of 4,30 and 4,02, and very strong correlation of 0,93 are further evidence of the similarity of
the two sets of data; and therefore the reliability of the new relationship in estimating linear
shrinkage of soils from laboratory measured liquid limits. The relationship between laboratory
measured and calculated linear shrinkage values is illustrated diagrammatically in Fig. (10.8),
and takes the form of
LSmeasured = 0,997LSLL (10.19)
LS measured/ LSLL
Measured linear shrinkage
LSmeas. (%)
35
30
25
20
15
10
5
0
n = 90
R 2 = 0,86
LS meas. = 0,997LSLL
Black clays and red
soils
Linear (Black clays
and red soils)
0 10 20 30
Calculated linear shrinkage LSLL
(%)
Figure 10.8. A correlation between calculated and laboratory determined linear
shrinkage of black clays and red soils.
10.4 Free swell and other index properties
The Swelling capability of black clays and red soils could be estimated with a high degree of
approximation (R² = 0,85 and over) from laboratory results of Atterberg limits and linear
shrinkage. The form and strength of correlation between laboratory determined free swell
(FS) on one hand; and liquid limits (LL), plasticity index (PI) and linear shrinkage (LS) of the
soils on the other, are illustrated in Table (10.6) and Fig. (10.9).