Implementation of a constitutive model for the finite element analysis of landslide triggered by rainfall

The paper deals with the implementation of an extended Cam-Clay model for unsaturated soils [14]. The model is defined using the generalized Bishop stress as formulated in [3] and [2] and an extended hardening law that accounts for the rate of the degree of saturation. The model is implemented in the research code COMES-GEO ([4], [5], [6], [7], [8]) and the rate equation is integrated Via an implicit return mapping scheme. The elastic predictor stage is modified to account for soil collapse due to wetting. This mathematical feature allows to use a single tangent matrix as discussed in the present paper. The model is applied in the simulation of a rainfall induced landslide. The purpose of the analysis is to assess the suitability of the model to reproduce a shallow landslide. The analysis of the stress path into the flowing mass show that the condition of instability corresponds to a phase transition of water vapour into liquid.