Item: Observer Independent Measures of Snow Instability
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Title: Observer Independent Measures of Snow Instability
Proceedings: International Snow Science Workshop 2016 Proceedings, Breckenridge, CO, USA
Authors:
- Benjamin Reuter [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
- Jürg Schweizer [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
- Alec van Herwijnen [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
Date: 2016-10-02
Abstract: Observer independent measures of snow instability are a prerequisite for modeling, verifying and improving avalanche forecasts. However, presently no metrics directly related to snow instability exist. Instead, signs of instability or results from snow instability tests are frequently used to assess instability or the avalanche danger. Whereas these observations are well related to instability, they are subjective and difficult to use for quantitative analyses. We therefore developed three metrics of snow instability inspired by our understanding of the avalanche release process. We used a data set of over a hundred snow micro-penetrometer resistance profiles and concurrently performed propagation saw tests and rutschblock tests to model, in a first step, failure initiation and crack propagation with finite elements. A stress-based criterion and an estimate of the critical cut length as obtained with a PST were derived from the force signal of the SMP measurements. While both instability measures agreed well with observed signs of instability, some discrepancies were observed. We therefore introduced a third criterion based on modeled tensile stresses in the slab in comparison with the strength of the slab layers. Preliminary results indicate that with this three-step approach snow instability can be derived with observer-independent metrics related to the avalanche release processes. The criteria refer to failure initiation and the onset of crack propagation and are complemented with a tensile failure criterion related to the phase of dynamic crack propagation.
Object ID: ISSW16_O17.02.pdf
Language of Article: English
Presenter(s):
Keywords: snow instability, avalanche forecasting, snow micro-penetrometer, avalanche initiation, crack propagation, tensile strength, finite element modeling
Page Number(s): 390-396
Subjects: Snow Instability avalanche forecasting snow micro penetrometer
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