In this paper, a problem involving unsteady or time-dependent infiltration into two-layered soils is considered. The problem is governed by a Richards’ equation. Using a set of transformations including a Laplace transform (LT), the governing equation is transformed into a modified Helmholtz equation. The modified Helmholtz equation is then solved using a dual reciprocity method (DRM). Numerical solutions obtained are then transformed back using a numerical inverse Laplace transform known as Stehfest formula. Results obtained are then presented and discussed to investigate the influence of infiltration time to soil suction potential.

Laplace transform dual reciprocity method, water flow, two-layered soils, modified Helmholtz equation.