Modelling rainfall-induced landslides from initiation of instability to post-failure

This paper presents a model for rainfall-induced shallow landslides, revealing the failure mechanism from initiation of instability to final flow failure. The onset of slope failure occurs with a completely formed plastic shear band that is triggered by a rainfall-induced increase in pore pressure. The subsequent flow-like deformation is caused by the strain-softening effect associated with large strains. Due to the complex non-linearity in stress seepage coupling and large deformation, modelling the entire progressive failure induced by rainfall is always a challenge. Therefore, the model in this paper uses a two-step strategy, i.e., coupled hydro-mechanical finite element (FE) analysis for step 1 and large deformation FE analysis for step 2, to realize the simulation of the entire failure process. An equivalent strength method is used to ensure the physical continuity between step 1 and step 2. A more reasonable evaluation of large deformation during post-failure can be achieved without a predefined slip surface. The model is applied to the analysis of two real rainfall-induced landslide cases. Numerical analysis demonstrates the ability of this model to evaluate the progressive variations in pore pressure, displacement, plastic strain, and factor of safety (FOS) with rainfall infiltration and simulate the final flow-like deformation.