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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10.3) for the black <strong>clays</strong>. The calculated values are shown to be strongly in close agreement<br />
with laboratory determined plasticity indices (PImeasured) in terms <strong>of</strong> maximum (53-55%),<br />
minimum (37-39%) <strong>an</strong>d r<strong>an</strong>ge (15-17%) values; as well as the medi<strong>an</strong>, mode <strong>an</strong>d me<strong>an</strong><br />
values (47-48%). St<strong>an</strong>dard deviation (2,85-3,09) <strong>an</strong>d vari<strong>an</strong>ce (8,13-9,53) are also in strong<br />
agreement <strong>an</strong>d <strong>of</strong> the same order <strong>of</strong> magnitude, signifying a similar form <strong>of</strong> distribution across<br />
the study area. A covari<strong>an</strong>ce <strong>of</strong> 5,89-6,37 <strong>an</strong>d a strong correlation <strong>of</strong> 0,70 was also registered<br />
between the calculated <strong>an</strong>d laboratory determined plasticity indices.<br />
Table 10.4. Calculated <strong>an</strong>d laboratory measured plasticity indices <strong>of</strong> red soils.<br />
Pr<strong>of</strong>ile Sample No. Wn (%) LL (%) PL (%)<br />
PImeasured<br />
(%) PI BS (%) PILL (%)<br />
Rd1 -30cm 39 49 31 18 21 19<br />
Red soils Rd1-100cm 24 51 31 21 23 21<br />
Rd1-200cm 24 49 30 20 21 19<br />
Rd1-400cm 25 48 30 18 20 18<br />
Rd2-30cm 38 53 35 19 24 22<br />
Rd2-100cm 26 57 34 22 27 25<br />
Rd2-200cm 25 54 33 21 25 23<br />
Rd2-400cm 26 53 34 19 24 22<br />
max 22 27 25<br />
Statistical min 18 20 18<br />
<strong>an</strong>alysis r<strong>an</strong>ge 5 7 7<br />
medi<strong>an</strong> 20 24 21<br />
mode #NV 24 22<br />
me<strong>an</strong> 20 23 21<br />
st<strong>an</strong>dard dev. 1,62 2,29 2,48<br />
vari<strong>an</strong>ce 2,63 5,26 6,16<br />
covari<strong>an</strong>ce 2,56 2,77<br />
correlation 0,79 0,79<br />
Calculated plasticity indices for red soils (Table 10.4) are also closely comparable to the<br />
laboratory determined plasticity indices, with maximum <strong>an</strong>d minimum values <strong>of</strong> 22-27% <strong>an</strong>d<br />
18-20%, as well as a r<strong>an</strong>ge <strong>of</strong> 5-7%. Medi<strong>an</strong>, mode, <strong>an</strong>d me<strong>an</strong> values <strong>of</strong> 20-24%, 22-24% <strong>an</strong>d<br />
20-23% were also recorded. The st<strong>an</strong>dard deviation <strong>an</strong>d vari<strong>an</strong>ce are <strong>of</strong> the same order <strong>of</strong><br />
magnitude while a covari<strong>an</strong>ce <strong>of</strong> 2,56-2,77 <strong>an</strong>d strong correlation <strong>of</strong> 0,79 was recorded<br />
between the calculated <strong>an</strong>d measured sets <strong>of</strong> data.<br />
The calculated <strong>an</strong>d laboratory measured plasticity indices for both black <strong>clays</strong> <strong>an</strong>d red soils<br />
are in a very strong <strong>an</strong>d near perfect agreement (Fig. 10.6), being related in the form <strong>of</strong><br />
<strong>an</strong>d<br />
PImeasured = 0,99PIBS, (10.16)<br />
PImeasured = 0,99PILL (10.17)