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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 16, issue 3 | Copyright
Nat. Hazards Earth Syst. Sci., 16, 775-788, 2016
https://doi.org/10.5194/nhess-16-775-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 18 Mar 2016

Research article | 18 Mar 2016

Snow instability evaluation: calculating the skier-induced stress in a multi-layered snowpack

Fabiano Monti1,2,*, Johan Gaume1,*, Alec van Herwijnen1, and Jürg Schweizer1 Fabiano Monti et al.
  • 1WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland
  • 2ALPsolut S. r. l., Via Saroch 1098b, c/o Plaza Placheda, 23030 Livigno, Italy
  • *These two authors equally contributed to this work

Abstract. The process of dry-snow slab avalanche formation can be divided into two phases: failure initiation and crack propagation. Several approaches tried to quantify slab avalanche release probability in terms of failure initiation based on shear stress and strength. Though it is known that both the properties of the weak layer and the slab play a major role in avalanche release, most previous approaches only considered slab properties in terms of slab depth, average density and skier penetration. For example, for the skier stability index, the additional stress (e.g. due to a skier) at the depth of the weak layer is calculated by assuming that the snow cover can be considered a semi-infinite, elastic, half-space. We suggest a new approach based on a simplification of the multi-layered elasticity theory in order to easily compute the additional stress due to a skier at the depth of the weak layer, taking into account the layering of the snow slab and the substratum. We first tested the proposed approach on simplified snow profiles, then on manually observed snow profiles including a stability test and, finally, on simulated snow profiles. Our simple approach reproduced the additional stress obtained by finite element simulations for the simplified profiles well – except that the sequence of layering in the slab cannot be replicated. Once implemented into the classical skier stability index and applied to manually observed snow profiles classified into different stability classes, the classification accuracy improved with the new approach. Finally, we implemented the refined skier stability index into the 1–D snow cover model SNOWPACK. The two study cases presented in this paper showed promising results even though further verification is still needed. In the future, we intend to implement the proposed approach for describing skier-induced stress within a multi-layered snowpack into more complex models which take into account not only failure initiation but also crack propagation.

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We propose a new approach based on a simplification of the multi-layered elasticity theory in order to easily compute the additional stress due to a skier at the depth of the weak layer, taking into account the layering of the snow slab and the substratum. The method was tested on simplified snow profiles, then on manually observed snow profiles including a stability test and, finally, on simulated snow profiles, thereby showing the promise of our approach.
We propose a new approach based on a simplification of the multi-layered elasticity theory in...
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