Deformation and energy of dry snow slabs prior to fracture propagation
Abstract:Snow slab avalanches primarily release by propagation of shear fractures within thin weak layers under thicker slabs. The weak layer is typically on the order of 1 mm thick and fails in mode II. In some cases, the weak layer is thicker and there may be a need to consider slope-normal deformation as part of the energy condition prior to rapid propagation. In this paper, field measurements from shear fracture initiation and high-speed films are combined to consider the effects of slope-normal deformation on bending of the slab prior to propagation and its relation to the propagation condition. Slab bending is modelled using two limiting cases: (1) a uniformly loaded beam supported by a deforming weak layer, analogous to a Winkler foundation, and (2) a uniformly loaded unsupported cantilevered beam. The experimental and analytical results suggest that slab bending prior to fracture initiation is small or negligible. Two previous approaches to modelling slab avalanche initiation involving slab bending are discussed. Both models proposed strong slab-bending effects prior to initiation, which conflicts with our results. Our field observations and modelling both show that strong bending is a dynamic effect following slope-parallel weak-layer fracture initiation.
Document Type: Research Article
Publication date: June 1, 2012
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- The Journal of Glaciology is published six times per year. It accepts submissions from any discipline related to the study of snow and ice. All articles are peer reviewed. The Journal is included in the ISI Science Citation Index.
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