an engineering geological characterisation of tropical clays - GBV

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Alternatively, percentage swelling of clays could be derived by expressing the swelling (S
mm) which occurs under any load decrement (P kPa) as a percentage of the initial thickness
(Ho mm) of test specimen. Complete results of percentage swelling calculated for tested black
clay samples using this second method are given in Appendix C. A more summarised
representation of the results for the samples is given in Table (7.23). A derived classification
of relative degree of swelling of black clays based on this new method is also given in Table
(7.24).
Table 7.23. Percentage swelling of black clays under various load decrements (S% is in
relation to initial specimen height, Ho, i.e. 2 nd method).
Sample No. P (kPa) SP = Pmax (kPa) P (%) S (mm) Smax (mm) S (%) Smax(%)
82,46 100 0,000 0,00
41,23 50 0,106 0,96
SA2-70cm 19,99 24 0,253 2,30
10,00 82,46 12 0,321 1,036 2,92 9,42
5,00 6 0,539 4,90
2,50 3 0,725 6,59
0,00 0 1,036 9,42
37,48 100 0,000 0,00
18,74 50 0,054 0,49
SB1-70cm 10,00 37,48 27 0,126 0,425 1,15 3,86
5,00 13 0,197 1,79
2,50 7 0,279 2,54
0,00 0 0,425 3,86
36,23 100 0 0,00
17,49 48 0,066 0,60
SC25/50cm 8,75 36,23 24 0,16 0,475 1,45 4,32
5,00 14 0,26 2,36
2,50 7 0,347 3,15
0,00 0 0,475 4,32
44,98 100 0 0,00
22,49 50 0,061 0,55
SC29-50cm 11,24 44,98 25 0,149 0,493 1,35 4,48
5,00 11 0,266 2,42
2,50 6 0,356 3,24
0,00 0 0,493 4,48
Average 50,29 0,607 5,52
Table 7.24. Classification of relative degree of swelling of black clays based
on percentage swelling derived using the new/ 2 nd method (author, 2003).
P (kPa) P (%) S (%) Swelling degree
< 2,5 < 5 > 5 high
2,5-7,5 5-15 5 – 2,5 moderate
7,5-25,0 15-50 2,5- 0,5 low
> 25,0 > 50 < 0,5 very low