Investigation of the interplay between shear failure and normal collapse of weak layers using microstructure-based mechanical simulations

International audienceWeak layers of snow are thin layers of low density and cohesion that consist of a complexnetwork of sintered ice grains. These layers are very fragile and their failure is considered to be the primarycause of dry slab snow avalanche release. This study reports on the results of modelling the mechanicalresponse of these weak snow layers with discrete element (DEM) simulations, using X-ray microtomographicimages of real snow samples as input data. An original method for approximating arbitrary grain shapes inDEM was developed that enabled us to accurately capture the effect of snow microstructure on the mechanicalbehaviour of varying snow types, including weak snow layers. Three samples of different snow types havebeen subjected to simple shear simulations with varying normal pressure and a qualitatively similar result wasobtained for all three samples. The simulation results permitted us to study the failure as well as post-peakstrain softening and residual stress in snow. Failure envelopes of different snow types are presented andthe effect of the microstructure on the failure envelope characteristics is analyzed. A detailed investigation ofthe interplay between shear failure and collapse is conducted and put into perspective by the damage thatprogressively propagates through the specimen