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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160<br />
Liquid limit (LL) variation (< 0,5 m)<br />
36°55´E<br />
LL (%)<br />
1°19´S<br />
Pr<strong>of</strong>ile dist<strong>an</strong>ce (m)<br />
West<br />
1°21.5´S<br />
36°49´E<br />
LL%<br />
88<br />
87.5<br />
87<br />
86.5<br />
86<br />
85.5<br />
85<br />
84.5<br />
84<br />
83.5<br />
83<br />
82.5<br />
82<br />
81.5<br />
81<br />
80.5<br />
80<br />
79.5<br />
79<br />
78.5<br />
South<br />
Pr<strong>of</strong>ile dist<strong>an</strong>ce (m)<br />
Fig. 8.4a. Block diagram showing distribution <strong>an</strong>d variation <strong>of</strong> liquid limit values at depths <strong>of</strong><br />
less th<strong>an</strong> 0,5m in black <strong>clays</strong>.<br />
A contoured representation <strong>of</strong> the distribution is shown in Figures (8.4a & b) in which<br />
isolated patches <strong>of</strong> relatively low liquid limits correspond to zones <strong>of</strong> more lateritic <strong>clays</strong><br />
<strong>an</strong>d/or swampy environments. On the whole, however, there is a slight tendency <strong>of</strong> liquid<br />
limit values to increase with depth. This could be attributed to the relatively higher org<strong>an</strong>ic<br />
matter content <strong>of</strong> black <strong>clays</strong> for depths <strong>of</strong> less th<strong>an</strong> 0,50m, <strong>an</strong>d which has the effect <strong>of</strong><br />
inhibiting the plasticity <strong>of</strong> soils. As a result, soil depths <strong>of</strong> less th<strong>an</strong> 0,50m show medi<strong>an</strong>,<br />
mode <strong>an</strong>d me<strong>an</strong> liquid limit values <strong>of</strong> 84%, 85%, <strong>an</strong>d 84%, respectively, as well as st<strong>an</strong>dard<br />
deviation <strong>of</strong> 3,30 <strong>an</strong>d vari<strong>an</strong>ce <strong>of</strong> 10,90; while soil depths <strong>of</strong> 0,50m <strong>an</strong>d greater, exhibit<br />
relatively larger medi<strong>an</strong>, mode <strong>an</strong>d me<strong>an</strong> values <strong>of</strong> 87%, 89% <strong>an</strong>d 86%, respectively. The<br />
latter soil depths are also characterised by st<strong>an</strong>dard deviation <strong>of</strong> 4,11 <strong>an</strong>d vari<strong>an</strong>ce <strong>of</strong> 16,86.<br />
On the whole, however, the two sets <strong>of</strong> data at the two different depth intervals are generally<br />
comparable <strong>an</strong>d in good agreement, this being indicated by a covari<strong>an</strong>ce <strong>of</strong> 8,28 <strong>an</strong>d a fairly<br />
strong correlation <strong>of</strong> 0,63 (Table 8.1).