Evaluating snow weak-layer rupture parameters through inverse Finite Element modeling of shaking-platform experiments

Abstract

Abstract. Snowpack weak layers may fail due to excess stresses of various natures, caused by snowfall, skiers, explosions or strong ground motion due to earthquakes, and lead to snow avalanches. This research presents a model describing the behavior of "sandwich" snow samples subjected to shaking. The Finite Element model treats weak layers as interfaces with variable constitutive behavior parameters. This approach is validated by reproducing cyclic loading snow fracture experiments. The model evaluation revealed that the Mohr–Coulomb failure criterion, governed by cohesion and friction angle, was adequate to describe the experiments. The "best fit" cohesion and friction angle were ≈1.6 kPa and 22.5–60°, indicating that the cohesion mainly determines the outcome of tests. The model showed complex, non-homogeneous stress evolution within snow samples and especially the significance of tension for fracture initiation at the edges of the weak layer, caused by dynamic stresses due to shaking. Accordingly, the previously used analytical solution, ignoring the inhomogeneity of tangential and normal stresses along the failure plane, may incorrectly estimate the shear strength of weak layers. The obtained parameters may constitute valuable elements in mechanical models used for avalanche forecasting.