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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42<br />
The variation <strong>of</strong> v<strong>an</strong>e shear strength with natural moisture content <strong>of</strong> soils closely<br />
approximates a polynomial relationship with strong correlation for both soil types, giving R =<br />
1.0 for black <strong>clays</strong> <strong>an</strong>d R = 0,91 - 0,99 for red soils (Fig. 4.7).<br />
V<strong>an</strong>e shear strength (kPa)/ natural moisture content (%)<br />
200,00<br />
180,00<br />
c = -1,5051Wn 2 + 91,987Wn - 1220,7<br />
R 2 = 0,9976<br />
160,00<br />
140,00<br />
Red soil, Kenya<br />
High<br />
V<strong>an</strong>e shear strength c (kPa)<br />
120,00<br />
100,00<br />
80,00<br />
c = -1,6845Wn 2 + 101,55Wn - 1373,9<br />
R 2 = 0,9834<br />
Red soil,<br />
Arboretum<br />
Black <strong>clays</strong>,<br />
Madaraka<br />
Polynomial<br />
(Madaraka)<br />
Polynomial<br />
(Kenya High)<br />
60,00<br />
c = 0,3359Wn^2 - 24,801Wn + 473,93<br />
R^2 = 0,8292<br />
40,00<br />
20,00<br />
0,00<br />
0 5 10 15 20 25 30 35 40 45<br />
Natural moisture content Wn (%)<br />
Figure 4.7 Variation <strong>of</strong> field v<strong>an</strong>e shear strength with natural moisture content <strong>of</strong> soils for the<br />
s<strong>of</strong>t red friable <strong>clays</strong> <strong>an</strong>d s<strong>of</strong>t black <strong>clays</strong>.<br />
V<strong>an</strong>e shear strength <strong>an</strong>d bulk density were observed to generally increase with increased soil<br />
depths (Tables 4.2, 4.3, 4.4). So far, the variation <strong>of</strong> v<strong>an</strong>e shear strength with bulk density is<br />
best described by a polynomial relationship (Fig. 4.8) with a very strong correlation (R = 0,97<br />
for black <strong>clays</strong>; R = 0,99-1,0 for red soils).
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