Soil-Water Characteristic Curves for Unsaturated Soils - Unsaturated Soil Mechanics in Engineering Practice - page 229

100
90

80
70
60
50
40
30
20
10
0
0.001

Beaver Creek sand
(Brush, 1993)
Processed silt (Bruch, 1993)
Sask. sility sand
Indian Head till

0.01 0.1 1 10

Grain size, mm

Figure 5.58 Grain-size distributions for four soils for which SWCCs were measured (after
Pham, 2005).

140

Measured data for Regina clay (Fredlund, 1964)

Best-fitted curve for Regina clay

120 Measured data for Jossigny silt (Fleureau et al., 1995)

Best-fitted curve for Jossigny silt

100 Measured data for kaolin (Fleureau et al., 2004)

Best-fitted curve for kaolin

80

60

40

20

0

10 6 0.1 1 10 100

Soil suction, kPa

1,000 10,000 100,000

Figure 5.59 Best-fitting curves using meaningful parameter SWCC equation along with pub-
lished data sets for three soils (Data fits by Pham, 2005).

undertaking the best-fitting procedure. The fitting procedure
was used to find the parameters a , b , S 1 , w s , and w r .Best-
fit SWCC parameters for three soils are shown in Fig. 5.61.
Best-fit SWCC parameters corresponding for the soils tested
at the University of Saskatchewan, Saskatoon, are shown in
Fig. 5.62. A summary of the curve-fitting parameters corre-
sponding to the simplified SWCC equation for seven soils
is shown in Table 5.6.

50
45
40
35
30

Measured data for Beaver Creek sand

Best-fitted curve for Beaver Creek sand

Measured data for Sask silty sand

Best-fitted curve for Sask silty sand

Measured data for processed silt

Best-fitted curve for processed silt

Measured data for Indian Head till

25
20
15
10
5
0

Best-fitted curve for Indian Head till

5.6.4 Comments on Pham and Fredlund (2011)
SWCC Equations
The Pham and Fredlund (2011) SWCC equations (i.e., Eqs.
5.72 and 5.73) make use of the curve-fitting parameters w s
and S 1 corresponding to saturated initial slurry conditions.
The variable w s represents the gravimetric water content
at a soil suction of approximately 1 kPa (provided the soil

10 6 0.1 1 10 100

Soil suction, kPa

1000 10,000 100,000

Figure 5.60 Best-fitting curves using meaningful parameter
SWCC equation along with measured data sets for four soils (after
Pham, 2005).