Received: 25 May 2018 – Accepted for review: 31 Aug 2018 – Discussion started: 03 Sep 2018
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.
How to cite. Bartelt, P., Caviezel, A., Degonda, S., and Buser, O.: Avalanche Impact Pressures on Structures with Upstream Pile-Up/Accumulation Zones of Compacted Snow, Nat. Hazards Earth Syst. Sci. Discuss. [preprint], https://doi.org/10.5194/nhess-2018-154, 2018.
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.
A longstanding problem in avalanche science is to understand why slow moving avalanches exert...