Modelling Wetting Collapse, Failure and Deposition of an Unsaturated Slope With Material Point Method

The paper presents the modelling of unsaturated soils with the material point method (MPM), including the effect of wetting leading to the loss of strength and the volumetric collapse. The elastoplastic Clay and Sand Model (CASM) extended to unsaturated conditions, formulated in terms of Bishop's stress and suction, has been implemented in an MPM‐based computational tool, in which gas density and pressure is assumed constant. The implementation of infiltration and seepage boundary conditions, required for wetting problems, are discussed and validated. A centrifuge experiment involving the construction, wetting, failure and post‐failure of a slope is interpreted and reproduced by the MPM‐based tool. Centrifuge data captured by video images, first analysed by particle image velocity (PIV) and then improved by the PIV‐numerical particle (NP) procedure, provides the motion and deformation of the entire experiment and is compared with calculations. The measured response of a 1D column of the model slope during the first stages of the test provided a first approximation of the constitutive parameters. The finally adopted set of model parameters led to a proper simulation of the entire response of the slope during wetting pre‐ and post‐failure stage.