Micromechanical controls of mixed-mode anticrack nucleation in porous solids: application to snow failure

Porous cohesive materials can fail and collapse under compressive stresses. This mechanical behavior is generally referred to as anticrack and in snow, it is at the origin of catastrophic avalanches. In this study, we investigate how the microstructure of a porous cohesive granular material affects its yield surface and plastic flow. The porous cohesive samples are generated based on Baxter's Sticky Hard Spheres which allows to independently control the volume fraction and coordination number of the samples. Discrete element simulations are performed under mixed-mode shear-compression loading. Our results show that the yield surface of the samples can be approximated by an ellipsoid function. While the shape of the yield surface appears uninfluenced by the micro-structure, its size significantly increases with increasing contact density according to a power law. Furthermore, we demonstrate that such porous solids follow an associative plastic flow rule which validates recent assumptions made in continuum anticrack models used for snow for avalanche simulations.