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      Snow fracture in relation to slab avalanche release: critical state for the onset of crack propagation

      , , , ,
      The Cryosphere
      Copernicus GmbH

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          Abstract

          The failure of a weak snow layer buried below cohesive slab layers is a necessary, but insufficient, condition for the release of a dry-snow slab avalanche. The size of the crack in the weak layer must also exceed a critical length to propagate across a slope. In contrast to pioneering shear-based approaches, recent developments account for weak layer collapse and allow for better explaining typical observations of remote triggering from low-angle terrain. However, these new models predict a critical length for crack propagation that is almost independent of slope angle, a rather surprising and counterintuitive result. Based on discrete element simulations we propose a new analytical expression for the critical crack length. This new model reconciles past approaches by considering for the first time the complex interplay between slab elasticity and the mechanical behavior of the weak layer including its structural collapse. The crack begins to propagate when the stress induced by slab loading and deformation at the crack tip exceeds the limit given by the failure envelope of the weak layer. The model can reproduce crack propagation on low-angle terrain and the decrease in critical length with increasing slope angle as modeled in numerical experiments. The good agreement of our new model with extensive field data and the ease of implementation in the snow cover model SNOWPACK opens a promising prospect for improving avalanche forecasting.

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          Most cited references43

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          A physical SNOWPACK model for the Swiss avalanche warning

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            Snow avalanche formation

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              snowpack model calculations for avalanche warning based upon a new network of weather and snow stations

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                Author and article information

                Journal
                The Cryosphere
                The Cryosphere
                Copernicus GmbH
                1994-0424
                2017
                January 2017
                : 11
                : 1
                : 217-228
                Article
                10.5194/tc-11-217-2017
                1abc49f8-c1d9-4692-b153-d971428e37cc
                © 2017

                https://creativecommons.org/licenses/by/3.0/

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