Hydro-mechanical coupling in unsaturated soils covering a non-deformable structure

Rainfall infiltration can lead to landslides and other geohazards. This paper develops an analytical solution incorporating 1D coupled deformation and rain water infiltration in an unsaturated porous medium. The porous medium is a deformable soil (top) layer covering a non-deformable bedrock (bottom) layer. The rainfall intensity, the hydraulic conductivity for the covering layer, and the thickness of the top and bottom soil layers were analyzed. The results indicate that the coupling between water infiltration and deformation plays a vital role in the response of the unsaturated soils. A small desaturation coefficient produces a strong coupling effect. The effect of the ratio of the hydraulic conductivity at full saturation to rainfall intensity on the pore-water pressure profile is mainly distributed at the interface of the two-layer structure. The coupling effect plays a role in the rate of groundwater rise at the interface. The lower layer thickness also influences the water pressure development in the unsaturated layer. Water pressure responses increase slowly with increasing thickness of the deformable soil, particularly at the interface in the layered structure. The coupling between water infiltration and deformation strengthens from the bottom to the top of the deformable layer for rainfall flux at the surface boundary.