ABSTRACT
The relative permeability kr is an essential parameter in the seepage analysis. This property is considered as a function of Sw, whereas the Sw is considered as a function of capillary pressure ψc (≡ −ψ). Among many mathematical models previously proposed to describe the water retention curve, the van Genuchten equation (van Genuchten 1980) (i.e., VG model) is employed in the present study; i.e.,
Se = Sw − Sr Sf − Sr =
{ 1 + (αψc)n
}−m (5)
where Se is the effective saturation, Sr is the residual saturation, Sf is the saturation at ψc = 0, and α, n and m are parameters. The parameters, n and m, are both dimensionless, whereas α has the dimension that can be defined as the reciprocal of the pressure head. The parameters n and m are not independent to each other, and they are related by
m = 1 − 1/n (6) The relative permeability and effective saturation
are interrelated as shown in the following form (Maulem 1976) ;
kr = Sεe { 1 − (1 − S1/me )m
}2 (7)
where ε is a parameter regarding the degree of interconnection among voids. Generally, a value of 0.5 is used for ε. The water retention curve and relative permeability can be calculated when the parameters α, n, Sr and Sf are all given. More details regarding the numerical techniques are given by Saito et al. (2008).
2.2 Effectiveness of LGD
