Shear Strength Applications in Plastic and Limit Equilibrium - Unsaturated Soil Mechanics in Engineering Practice - page 656

Figure 12.97 Cross section of typical steep slope in residual soils in Hong Kong.

fitted to the unsaturated permeability function proposed by
Gardner (1958a):

Table 12.11 Summary of Saturated Coefficients
of Permeability for Soils in Example 2

k s

k w =

(12.106)

Selected Permeability,

u w )/(ρ w g) ] n

1 + a [ (u a −

Soil Type k s (m/s)

The a and n values in Eq. 12.106 were found to be approx-
imately 0.1 and 3.0 for the colluvium and decomposed gran-
ite, respectively (Ng, 1988). The unsaturated permeability
functions were drawn as shown in Fig. 12.99 based on the
measured saturated coefficients of permeability.
The coefficient of water volume change, m 2 ,forthe
colluvium and the decomposed granite was computed to
be approximately 3

10 − 5

Colluvium 3 ×

10 − 6

Completely decomposed
granite

7 ×

10 − 6 Completely to highly

decomposed granite

6 ×

10 − 6

×

Highly decomposed granite 5

10 − 3 kPa − 1 . The shear

× strength

50

40

30

20

Completely decomposed granite
Colluvium

10

0 0.1

1 10 100 1000

Matric suction ( u a - u w ), kPa

Figure 12.98 SWCCs for completely decomposed granite and colluviums.