Preprints
https://doi.org/10.5194/nhess-2018-154
https://doi.org/10.5194/nhess-2018-154
03 Sep 2018
 | 03 Sep 2018
Status: this preprint was under review for the journal NHESS but the revision was not accepted.

Avalanche Impact Pressures on Structures with Upstream Pile-Up/Accumulation Zones of Compacted Snow

Perry Bartelt, Andrin Caviezel, Sandro Degonda, and Othmar Buser

Abstract. Existing methods to calculate snow avalanche impact pressures on rigid obstacles are based on the assumption of no upslope pile-up of snow behind the structure at impact. Here we develop a method to predict avalanche impact pressures that accounts for the compaction and accumulation process. We show why this process leads to large impact pressures even at low avalanche approach velocities. The induced pressure depends on the incoming avalanche flow density relative to the ultimate compaction density because this determines the avalanche braking distance and therefore the flow deceleration in the upstream direction. The pile-up/accumulation process induces two additional pressures: (1) the static pressure of the pile-up zone and (2) the tractive stresses operating on the shear planes interfacing the accumulated and still moving avalanche snow. We demonstrate the use of the model on two theoretical examples and one real case study. Avalanche mitigation in maritime regions, or regions undergoing climate change with increasing wet snow avalanche activity, should consider the forces caused by the pile-up/accumulation process in engineering design.

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Perry Bartelt, Andrin Caviezel, Sandro Degonda, and Othmar Buser
 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Perry Bartelt, Andrin Caviezel, Sandro Degonda, and Othmar Buser
Perry Bartelt, Andrin Caviezel, Sandro Degonda, and Othmar Buser

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Short summary
A longstanding problem in avalanche science is to understand why slow moving avalanches exert large pressures on buildings. To understand this phenomenon we propose that avalanche interaction with a rigid structure must be divided into two separate regimes: a flow regime and a pile-up regime. In the flow regime, snow does not accumulate behind the obstacle. We show why the accumulation of avalanche snow behind a structure can lead to immense forces that must be considered in mitigation.
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