Model-based identification of snow properties from full-field measurements

The accurate measurement of elastic and fracture properties of snow is challenging but crucial for the modeling of avalanche events. We propose the combination of a closed-form model of the mechanical behavior of layered snowpacks with full-field displacement measurements of propagation saw tests (PSTs) for the identification of the elastic properties of all snow layers and of the fracture toughness of weak layers.

The analytical model provides snow cover deformations, weak-layer stresses and energy release rates of cracks within the weak-layer for arbitrarily layered snowpacks. It can be used for real-time analyses of skier-loaded slopes and for stability tests such as the propagation saw test. Its real-time evaluation is particularly important for the present application.

Full-field measurements of snow cover deformations during propagation saw tests can be obtained using digital image correlation. Recordings of a simple handheld camera suffice for the present application.

The elastic material properties of each layer can then be obtained by fitting the modeled displacement field to the recorded field. The solution of this optimization problem requires many evaluations of the model with varied material parameters of all layers but finally yields the elastic properties of each layer of the snow cover.

Finally, the model allows for the calculation of weak-layer fracture toughnesses using the above determined material properties and the critical crack length of the PST experiment. The results indicate an increasing slab stiffness and an increasing weak-layer fracture toughness throughout one winter season.