The Evaluation of Infiltration Capacity Using the Approximate Expression for Sorptivity in Non-rigid Soil as Kanto Loam.

Abstract

The purpose of this paper is to evaluate infiltration capacity using the regular changes of physical properties that are occurred by the different bulk densities with the same soil texture and particle density in non-rigid soil as 'Kanto Loam'. At unsaturated range of bulk densities 0.50∼0.60 Mg/m3, wetness retentivity w(ψ) and hydraulic conductivity k(ψ) at a bulk density agreed with them at the greater bulk density. The approximate expression for sorptivity S was derived to use the results of numerical simulations by the Galerkin type finite element method. The approximate expression for sorptivity S was exactly determined by saturated hydraulic conductivity ks and the difference between initial soil liquid potential and air entry potential ψri with very great coefficients of determinationR2. It may be not appropriate to adopt the initial soil liquid deficit variable Δθand macroscopic capillary length λc for ψri, because θ(ψ) and k(ψ) have the polynomial approximate relations with respect ψ in this paper. Sorptivity S is proportional to about ks0.5 and this result nearly agrees with White and Sully (1987). This means that ks plays the part of proportional constant on the sorptivity with each bulk density. Because the change of ks with bulk density is occurred by that of void ratio, the change of ks with bulk density has the major effect on infiltration capacity. In non-rigid soils as Kanto Loam, bulk density is the most meaningful soil property in evaluating infiltration capacity, and the change of bulk density may be occurred by various natural and artificial impacts. Therefore, it is very important in effective water resource management to estimate exactly the change of infiltration capacity with bulk density.