Item: A New Crack Propagation Criterion for Skier-Triggered Snow Slab Avalanches
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Title: A New Crack Propagation Criterion for Skier-Triggered Snow Slab Avalanches
Proceedings: International Snow Science Workshop 2016 Proceedings, Breckenridge, CO, USA
Authors:
- Johan Gaume [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ] [ Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland ]
- Benjamin Reuter [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
- Alec van Herwijnen [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
- Jürg Schweizer [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
Date: 2016-10-02
Abstract: Dry-snow slab avalanches begin with a local failure in a weak snowpack layer buried below cohesive slab layers. If the size of the failed zone exceeds a critical length, rapid crack propagation occurs possibly followed by slab release if the slope is steep enough. The probability to trigger a slab avalanche by a skier or a snowmobile is generally described by classical stability indices which do not account for crack propagation. In this study, we propose a new model to evaluate the conditions for the onset of crack propagation in skier-triggered slab avalanches. This model simply compares the critical crack length obtained without a skier to the size of the area where the skier-induced stress exceeds the shear strength of the weak layer. The critical crack length is calculated from a recently developed model based on numerical simulations. The skier-induced stress is computed using two approaches which are compared: (i) a recent simplified approach accounting for the multi-layered character of the slab; (ii) finite element simulations. A detailed sensitivity analysis is performed for simplified snow profiles to characterize the influence of snowpack properties and slab layering on crack propagation propensity. We applied our approach for manually observed snow profiles and compared our results to rutschblock stability tests and to signs of instability observed during field work around Davos. The goal is to develop a new stability index for skier-triggered slab avalanches incorporating both failure initiation and crack propagation.
Object ID: ISSW16_P1.01.pdf
Language of Article: English
Presenter(s):
Keywords: Snow avalanche, skier-triggering, failure initiation, crack propagation, PST, slab, weak layer
Page Number(s): 484-491
Subjects: skier-triggered avalanches crack propagation persistent weak layers
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