Modelling the onset of rainfall-induced landslides

The paper presents a simplified modelling approach for unsaturated infinite slopes. As it is well known, during severe rainstorms the progressive saturation of natural deposits is the main triggering cause of slope instability. The goal of the approach suggested here is to evaluate the magnitude of the triggering perturbations, distinguishing among different forms of hydro-mechanical instability. For this purpose, the mechanical effects of partial saturation are reproduced by means of a coupled hydro-mechanical constitutive model and stability conditions are evaluated through the theory of test controllability. This enables to study the outcome of both mechanical and hydraulic perturbations by means of simple shear test simulations. The numerical results clearly suggest that both initial conditions (e.g., the initial suction) and behavioural properties (e.g., the soil compressibility) are dominant factors in determining the magnitude of the triggering perturbations and the type of expected instability mode.