Coupled infiltration model of unsaturated porous media for steady rainfall

Unsaturated soil slopes introduce complex hydro-mechanical coupled processes which greatly alter matric suction distribution of an unsaturated soil during rainfall. In order to investigate matric suction and volume change of unsaturated soils, a two-dimensional hydro-mechanical coupled infiltration model (YS-Slope) is developed by incorporating the hydraulic and mechanical characteristics of unsaturated soils, such as the soil-water characteristic curve, permeability function, shear strength, and porosity. Special attention is given to the porosity-dependent permeability function of unsaturated soils. In addition, in order to highlight effectiveness of YS-Slope and coupling effects of hydro-mechanical processes on the infiltration behavior of unsaturated soils, a series of infiltration analyses for a soil column under various soil properties is conducted and their results are compared with those of commercial software, GEO-SLOPE (2012). The results of the numerical analyses show good agreement with data from the analytical solution and laboratory tests, which indicates that the proposed model is appropriate for use in the simulatfion o the infiltration of rainwater into deformable soils. The transient seepage and rainwater flow in deformable soils are influenced by the volume change of the soil. The change in matric suction on a slope due to rainfall infiltration influences change in effective stress while the effective stress alters seepage processes according to hydraulic properties. The results indicate that hydro-mechanical coupled behavior of soils has a positive effect on the stability of unsaturated soil slops during rainfall.