Phase-field modeling of cracking process in partially saturated porous media and application to rainfall-induced landslides

In this paper, we first present a new phase-field model for modeling the deformation and progressive failure in saturated and unsaturated porous rocks. Two independent damage variables are used to easily capture tensile and shear cracks. The influences of frictional shear stress and normal stress on the evolution of shear cracks are taken into account. The phase-field model is extended to variably saturated porous rocks by including the effect of pore water pressure. The proposed model is implemented in the framework of finite element method for coupled hydro-mechanical and damage problems. The phase field model is able to describe global stress-strain responses and localized cracking patterns in brittle rocks at the laboratory scale. The onset of localized cracks is directly linked to the non-uniform distribution of porosity. The proposed phase-field model is also applied to the analysis of rainfall-induced landslides. The numerical results of cracking scenarios are consistent with the real field observations in the Mayanpo slope in China. The main physical mechanisms involved in the rainfall induced instability of slopes are analyzed.