Item: Snowpack stabilization following storms: Field experiments and modelling of temporal changes in snow mechanical properties following loading
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Title: Snowpack stabilization following storms: Field experiments and modelling of temporal changes in snow mechanical properties following loading
Proceedings: International Snow Science Workshop Proceedings 2018, Innsbruck, Austria
Authors:
- Karl W. Birkeland [ USDA Forest Service National Avalanche Center, Bozeman, Montana, USA ]
- Alec van Herwijnen [ WSL-SLF Swiss Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
- Benjamin Reuter [ WSL-SLF Swiss Institute for Snow and Avalanche Research SLF, Davos, Switzerland ] [ Department of Civil Engineering, Montana State University, Bozeman, Montana, USA ]
- Bastian Bergfeld [ WSL-SLF Swiss Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
Date: 2018-10-07
Abstract: Most dry slab avalanches occur during or immediately following loading by snowfall or winddeposition. In the absence of further loading avalanche activity decreases over time. This suggests thatavalanche release is facilitated by changes in snowpack properties during loading, and that changesfollowing loading generally help to stabilize the snowpack. This study quantifies these longer termstabilizing changes following loading. We developed a field method to rapidly increase the load onexisting weak layers, and used the technique to add 10 cm of disaggregated snow on over 30 isolatedcolumns. We then conducted Propagation Saw Tests (PSTs) in the minutes, hours and days followingloading and isolation, with tests ranging from 15 minutes to 4 days. We filmed each test at 120 fps forparticle tracking velocimetry analysis, and we utilized a finite element (FE) model to simulate theexperiments and better interpret our results. We found that critical crack lengths increased rapidly at firstand then more slowly over time. FE simulations of the experiments suggest that changes in critical cracklength over time are caused by an increase in slab elastic modulus in the first hours following loading, andthen caused by both increasing slab elastic modulus and weak layer specific fracture energy in daysfollowing loading. Our results help to illustrate changes in critical crack lengths in the days followingloading, and are consistent with field observations of increasing avalanche activity immediately followingloading events and decreasing avalanche activity afterwards.
Object ID: ISSW2018_O10.2.pdf
Language of Article: English
Presenter(s):
Keywords: avalanche, fracture, loading, slab, particle tracking velocimetry, Propagation Saw Test
Page Number(s): 861-865
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