Numerical modeling of tensile fracture initiation and propagation in snow slabs using nonlocal damage mechanics

The results of numerical simulations of tensile fracture initiation and propagation in snow slabs are presented. Seventeen beam bending experiments, both notched and unnotched, were conducted using blocks of cohesive dry snow extracted from the same homogeneous layer in the natural snowpack. Material properties and fracture parameters were calculated from the experimental data using equations from beam theory and quasi-brittle fracture mechanics. These parameters were used in the nonlocal isotropic damage model to simulate the bending tests on two-dimensional finite element meshes. Using the same material parameters and boundary conditions, the model was capable of simulating the propagation of a tensile crack from an existing stress concentration as well as the initiation of a crack from a smooth boundary. Sensitivity analyses were conducted on the most uncertain model parameters. For the optimally paramaterized model, the simulated load-displacement curves agreed well with the experimental data, with the primary discrepancy related to the loss of elastic stability at peak load in the experiments. The spatial distribution of damage at peak load is shown to support a quasi-brittle interpretation of the fracture physics for both crack initiation and crack propagation problems. These results provide a foundation for future predictive modeling applications related to the tensile fractures associated with slab avalanches. (C) 2011 Elsevier B.V. All rights reserved.