Environmental Engineering Reference
In-Depth Information
10
−
11
10
−
12
Psychrometer
1
2
3
4
5
Best-fit line
10
−
13
10
−
14
100
1000
10,000
Soil suction, kPa
Figure 7.34
Unsaturated coefficients of permeability obtained in laboratory using instantaneous
profile method (after Hamilton et al., 1981).
et al., (2009). Independent measurements were made of the
SWCCs followed by an estimation of associated permeabil-
ity functions. An independent model study was performed
using the same soils, and the instantaneous profile method
was used to analyze the measurements obtained during water
infiltration and evaporations from the model slope.
Krisdani et al. (2009) first measured the saturated coeffi-
cient of permeability and the SWCC on three types of soil: a
residual soil, a mixture of the residual soil and fine sand, and
gravelly sand. The residual soil (RS) was derived from the
weathering of Bukit Timah granite which covers about one-
third of Singapore. The soil mixture contained 60% residual
soil and 40% fine sand by dry mass, MRF 60-40. The
gravelly sand (GS) was a commercially available mixture
of 50% coarse sand and 50% fine gravel. The grain-size
distributions of the soils used in the study are presented in
Fig. 7.35 and Table 7.7. The drying SWCCs of the soils were
obtained using Tempe cell and pressure plate apparatuses.
The wetting SWCCs were obtained using the capillary rise
open-tube method (Yang et al., 2004a). The experimental
data were fitted using the Fredlund and Xing (1994) equation
with the correction factor
C
(
ψ
) set to 1. The results of dry-
ing (D) and wetting (W) SWCC tests together with the fitted
curves are shown in Fig. 7.36, while the fitting parameters
Sand
Coarse Medium
Clay
Silt
Gravel
Fine
100
RS
80
GS
60
40
MRF_60-40
20
0
10
1
0.1
0.01
0.001
Particle size, mm
Figure 7.35
Grain-size distribution of soils used in unsaturated flow study at Nanyang Tech-
nological University (NTU), Singapore (after Krisdani, et al., 2009).
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