Item: Dynamic crack propagation in weak snowpack layers: insights from high-resolution, high-speed photography
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Title: Dynamic crack propagation in weak snowpack layers: insights from high-resolution, high-speed photography
Proceedings: International Snow Science Workshop Proceedings 2018, Innsbruck, Austria
Authors:
- Bastian Bergfeld [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
- Alec van Herwijnen [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
- Jürg Dual [ Institute for Mechanical Systems, ETH Zürich, Zürich, Switzerland ]
- Jürg Schweizer [ WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland ]
Date: 2018-10-07
Abstract: To assess the avalanche triggering potential, information on failure initiation and crack propagation is required. While in the past failure initiation has extensively been studied, research focusing on the dynamics of crack propagation only started with the introduction of the Propagation Saw Test (PST) in the mid 2000s. Since then, various studies used particle tracking analysis of high-speed video recordings of PST experiments to gain insight into crack propagation processes, including slab bending, weak layer collapse, crack propagation speed and the frictional behavior after weak layer fracture. Nevertheless, many issues remain unanswered as due to the limited resolution of the videos it thus far was not possible to investigate dynamic processes, especially in the vicinity of the crack tip in the weak layer. We therefore recorded a PST experiment using a powerful portable high-speed camera with a horizontal resolution of 1280 pixels at 10,000 frames per second. By applying a high density speckling pattern on the entire PST column, we then used digital image correlation (DIC) to derive high-resolution displacement and strain fields in the slab, weak layer and substratum. Based on the displacement of the slab, we determined the evolution of weak layer crack speed and compared it to an alternative method where the strain concentration within the weak layer was used. Our results show that crack speed can be derived with both approaches. Hence, our measurement methodology has the potential to provide new insights into the dynamics of sustained crack propagation and crack arrest associated with slab avalanche release.
Object ID: ISSW2018_P10.12.pdf
Language of Article: English
Presenter(s):
Keywords: snow avalanche, fracture, crack speed, slab, weak layer, high-speed photography
Page Number(s): 935-939
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