Numerical investigation of rainfall-induced slope failures through coupled fluid–soil interaction modeling

This paper performs a detailed numerical analysis of slope instability that can be caused by precipitation using a full couple fluid-soil interacting model. The analyses are based on the formulation of the finite element with the usage of Richards equation to state the movements of water by means of unsaturated and saturated mediums. The three sandly materials were tested under condition of rainfall of 25, 50, 75 and 100mm h -1 and also at different storm duration durations to determine stability of the sand in different infiltration regimes. Findings prove that the factor of safety (FS) decreases in proportion to the intensity and duration of rainfall highlighting the importance of the pore-water pressure accumulation and suction depletion in triggering failure. The Toyoura sand was more stable, which is explained by the high permeability and high friction angle whereas Saigata and Ohto sand had lower stability because it had already failed at high rainfall intensity. The two-way hydro-mechanical methodology is good in capturing the elusive behavior of the pore pressure and the effective stress, with more accuracy than the uncoupled models. The results put the model in perspective of its ability to forecast rainfall led slope failures and its ability to help in making better slope designs and risks assessment.