an engineering geological characterisation of tropical clays - GBV
an engineering geological characterisation of tropical clays - GBV
an engineering geological characterisation of tropical clays - GBV
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139<br />
Testing procedure involved cutting <strong>an</strong> undisturbed soil specimen into the consolidation ring,<br />
assembling it in the oedometer cell <strong>an</strong>d mounting the cell in the load frame <strong>of</strong> a consolidation<br />
press. Distilled water was added into the cell to saturate the soil specimen <strong>an</strong>d a stop-clock<br />
started at the same time. Ch<strong>an</strong>ges in compression gauge reading due to swelling <strong>of</strong> specimen<br />
were noted <strong>an</strong>d recorded with time; <strong>an</strong>d small weights added to the weight h<strong>an</strong>ger <strong>of</strong> the<br />
apparatus to bring the compression gauge reading back to zero or initial reading <strong>an</strong>d,<br />
therefore, prevent swelling. The compression gauge reading was observed over a period <strong>of</strong> 24<br />
hours, during which time more weights were added as necessary to maintain the reading as<br />
close as possible to zero or initial reading.<br />
120<br />
Swelling Pressure curves for black <strong>clays</strong><br />
100<br />
SA41-30cm (104 kPa)<br />
Swelling pressure (kN/m²)<br />
80<br />
60<br />
40<br />
SA2-70cm (95 kPa)<br />
SB1-70cm (49 kPa)<br />
SB42-50cm (53 kPa)<br />
SC17-50cm (70 kPa)<br />
20<br />
SC29-50cm (50 kPa)<br />
0<br />
0 10 20 30 40 50 60<br />
Square-root-time (minutes)<br />
Figure 7.28. Swelling pressure curves obtained for black <strong>clays</strong> in this study.<br />
A record <strong>of</strong> the amount <strong>of</strong> each load increment <strong>an</strong>d time from start when added was tabulated<br />
(Table 7.19), <strong>an</strong>d a graph <strong>of</strong> total pressure on specimen against square root <strong>of</strong> time plotted.<br />
Swelling pressure test curves obtained for the black <strong>clays</strong> in this study are presented in Fig<br />
(7.28). Flattening <strong>of</strong> the curves serves to indicate equilibrium having been virtually reached.<br />
Table 7.19. Results <strong>of</strong> swelling pressures for black <strong>clays</strong>, alongside corresponding index<br />
properties <strong>an</strong>d clay mineralogy (smectites).<br />
Sample No. LL (%) PL (%) PI (%) FS (%) Wn (%) Cr LI<br />
% smectites<br />
(min.)<br />
SP (kPa)<br />
SA2-70cm 90 36 54 170 34 1,04 -0,04 90,00 95<br />
SA41-30cm 89 41 47 135 23 1,39 -0,39 95,00 104<br />
SB1-70cm 90 39 51 145 30 1,19 -0,19 95,00 49<br />
SB42-50cm 91 45 47 145 21 1,50 -0,50 95,00 53<br />
SC17-50cm 81 33 48 110 22 1,22 -0,22 95 70<br />
SC29-50cm 80 37 43 110 20 1,38 -0,38 95 50<br />
Correlations 0,22 -0,11 0,41 0,35 0,34 -0,31 0,31 -0,51
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