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Modeling snow slab avalanches caused by weak layer failure – Part II: Coupled mixed-mode criterion for skier-triggered anticracks

Rosendahl, Philipp Laurens and Weißgraeber, Philipp (2019):
Modeling snow slab avalanches caused by weak layer failure – Part II: Coupled mixed-mode criterion for skier-triggered anticracks.
In: The Cryosphere Discussions, pp. 1-25, ISSN 1994-0440,
DOI: 10.5194/tc-2019-87,
[Article]

Abstract

Abstract. Using the analytical model presented in part I of this two-part paper, a new conceptual understanding of anticrack nucleation in weak layers is proposed. To obtain a sufficient condition for onset of failure two necessary conditions must be satisfied simultaneously: i) The weak layer must be overloaded in terms of stress and ii) the initiating crack must release enough energy for the formation of new surfaces. This so-called coupled criterion was proposed by Leguillon (2002) Eur J Mech-A Solid, 21(1), 61{\&}ndash;72, 2002. No assumptions on initial defects within the weak layer are needed. Instead, the failure criterion provides both critical loading and the size of initiating cracks. It only requires the fundamental material properties strength and fracture toughness as inputs. Crack initiation and subsequent propagation are covered by a single criterion containing both a strength-of-materials and a fracture mechanics condition. Analyses of skier-loaded snowpacks show the impact of slab thickness and slope angle on critical loading and crack initiation length. In the limit cases of very thick slabs and and very steep slopes we obtain natural avalanche release. A discussion of different mixed-mode stress and energy criteria reveals that a wrong choice of mixed-mode hypotheses can yield unphysical results. The effect of material parameters such as density and compliance on weak layer collapse is illustrated. The framework presented in this two-part series harnesses the efficiency of closed-form solutions to provide fast and physically sound predictions of critical snowpack loads using a new conceptual understanding of mixed-mode weak layer failure. It emphasized the importance of both stress and energy in avalanche release.

Item Type: Article
Erschienen: 2019
Creators: Rosendahl, Philipp Laurens and Weißgraeber, Philipp
Title: Modeling snow slab avalanches caused by weak layer failure – Part II: Coupled mixed-mode criterion for skier-triggered anticracks
Language: English
Abstract:

Abstract. Using the analytical model presented in part I of this two-part paper, a new conceptual understanding of anticrack nucleation in weak layers is proposed. To obtain a sufficient condition for onset of failure two necessary conditions must be satisfied simultaneously: i) The weak layer must be overloaded in terms of stress and ii) the initiating crack must release enough energy for the formation of new surfaces. This so-called coupled criterion was proposed by Leguillon (2002) Eur J Mech-A Solid, 21(1), 61{\&}ndash;72, 2002. No assumptions on initial defects within the weak layer are needed. Instead, the failure criterion provides both critical loading and the size of initiating cracks. It only requires the fundamental material properties strength and fracture toughness as inputs. Crack initiation and subsequent propagation are covered by a single criterion containing both a strength-of-materials and a fracture mechanics condition. Analyses of skier-loaded snowpacks show the impact of slab thickness and slope angle on critical loading and crack initiation length. In the limit cases of very thick slabs and and very steep slopes we obtain natural avalanche release. A discussion of different mixed-mode stress and energy criteria reveals that a wrong choice of mixed-mode hypotheses can yield unphysical results. The effect of material parameters such as density and compliance on weak layer collapse is illustrated. The framework presented in this two-part series harnesses the efficiency of closed-form solutions to provide fast and physically sound predictions of critical snowpack loads using a new conceptual understanding of mixed-mode weak layer failure. It emphasized the importance of both stress and energy in avalanche release.

Journal or Publication Title: The Cryosphere Discussions
Divisions: 16 Department of Mechanical Engineering
Date Deposited: 13 Sep 2019 10:10
DOI: 10.5194/tc-2019-87
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