Triggering of dry snow slab avalanches: stress versus fracture mechanical approach

Chiaia, Bernardino; Cornetti, Pietro; Frigo, Barbara

doi:10.1016/j.coldregions.2007.08.003

Cited by 59 publications

(63 citation statements)

References 17 publications

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“…However, in the text, it was easier to explain the results by showing the knock-down and smoothing functions f 1 and f 2 as a function of the variables ∕h, ∕Λ, CV, and E. expansion in a quasi-brittle WL underlying a cohesive elastic slab can be expressed as follows [Chiaia et al, 2008]:…”

Section: Discussionmentioning

confidence: 99%

“…The solution of this problem was given by Chiaia et al [2008] and generalized by Gaume et al [2013a] for a Mohr-Coulomb WL failure criterion, showing that a stress concentration occurs at the tip of the crack. Hence, once a crack is initiated in a very weak zone, stresses will be redistributed toward stronger neighboring areas which in turn will reach the failure criterion more easily.…”

Section: Knock-down Function Fmentioning

confidence: 99%

“…Besides, the WL is assumed to be completely rigid; 3. Strength of material approaches solve the equilibrium equations of a slab-WL system in the presence of a single crack within the WL [Chiaia et al, 2008;Gaume et al, 2013a]. Stress concentrations occur at the tip of the crack which propagates when the failure criterion is reached.…”

Section: Appendix A: Fits Of the Knock-down And Smoothing Functions Fmentioning

confidence: 99%

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Evaluation of slope stability with respect to snowpack spatial variability

Gaume¹,

Schweizer²,

Herwijnen³

et al. 2014

JGR Earth Surface

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The evaluation of avalanche release conditions constitutes a great challenge for risk assessment in mountainous areas. The spatial variability of snowpack properties has an important impact on snow slope stability and thus on avalanche formation, since it strongly influences failure initiation and crack propagation in weak snow layers. Hence, the determination of the link between these spatial variations and slope stability is very important, in particular, for avalanche public forecasting. In this study, a statistical-mechanical model of the slab-weak layer (WL) system relying on stochastic finite element simulations is used to investigate snowpack stability and avalanche release probability for spontaneously releasing avalanches. This model accounts, in particular, for the spatial variations of WL shear strength and stress redistribution by elasticity of the slab. We show how avalanche release probability can be computed from release depth distributions, which allows us to study the influence of WL spatial variations and slab properties on slope stability. The importance of smoothing effects by slab elasticity is verified and the crucial impact of spatial variation characteristics on the so-called knock-down effect on slope stability is revisited using this model. Finally, critical length values are computed from the simulations as a function of the various model parameters and are compared to field data obtained with propagation saw tests.

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Section: Discussionmentioning

confidence: 99%

Section: Knock-down Function Fmentioning

confidence: 99%

Section: Appendix A: Fits Of the Knock-down And Smoothing Functions Fmentioning

confidence: 99%

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Evaluation of slope stability with respect to snowpack spatial variability

Gaume¹,

Schweizer²,

Herwijnen³

et al. 2014

JGR Earth Surface

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“…van Herwijnen et al, 2010;. On the other hand, theoretical and numerical models, based on fracture mechanics or strength of material approaches, were developed to investigate crack propagation and avalanche release (McClung, 1979;Chiaia et al, 2008;Gaume et al, 2013Gaume et al, , 2014b. While substantial progress has been made, application with regard to avalanche forecasting or hazard mapping is still hindered in part by our lack of understanding of the dynamic phase of crack propagation.…”

Section: Introductionmentioning

confidence: 99%

Modeling of crack propagation in weak snowpack layers using the discrete element method

Gaume¹,

Herwijnen²,

Chambon

et al. 2015

The Cryosphere

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Abstract. Dry-snow slab avalanches are generally caused by a sequence of fracture processes including (1) failure initiation in a weak snow layer underlying a cohesive slab, (2) crack propagation within the weak layer and (3) tensile fracture through the slab which leads to its detachment. During the past decades, theoretical and experimental work has gradually led to a better understanding of the fracture process in snow involving the collapse of the structure in the weak layer during fracture. This now allows us to better model failure initiation and the onset of crack propagation, i.e., to estimate the critical length required for crack propagation. On the other hand, our understanding of dynamic crack propagation and fracture arrest propensity is still very limited.To shed more light on this issue, we performed numerical propagation saw test (PST) experiments applying the discrete element (DE) method and compared the numerical results with field measurements based on particle tracking. The goal is to investigate the influence of weak layer failure and the mechanical properties of the slab on crack propagation and fracture arrest propensity. Crack propagation speeds and distances before fracture arrest were derived from the DE simulations for different snowpack configurations and mechanical properties. Then, in order to compare the numerical and experimental results, the slab mechanical properties (Young's modulus and strength) which are not measured in the field were derived from density. The simulations nicely reproduced the process of crack propagation observed in field PSTs. Finally, the mechanical processes at play were analyzed in depth which led to suggestions for minimum column length in field PSTs.

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“…Several approaches tried to quantify the slab avalanche release probability in terms of failure initiation, based on a stress-strength approach, such as skier stability index (Föhn, 1987b;Jamieson and Johnston, 1998), or fracture mechanics approaches assuming the presence of a weak spot (or a crack) within the weak layer (McClung, 1979;Heierli and Zaiser, 2007;Heierli et al, 2008;Chiaia et al, 2008;Gaume et al, 2013Gaume et al, , 2014Gaume et al, , 2015a. Both weak layer and slab play a crucial role in avalanche release (McClung and Schweizer, 1999).…”

Section: Introductionmentioning

confidence: 99%

Snow instability evaluation: calculating the skier-induced stress in a multi-layered snowpack

Monti¹,

Gaume²,

Herwijnen³

et al. 2016

Nat. Hazards Earth Syst. Sci.

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Abstract. The process of dry-snow slab avalanche formation can be divided into two phases: failure initiation and crack propagation. Several approaches tried to quantify slab avalanche release probability in terms of failure initiation based on shear stress and strength. Though it is known that both the properties of the weak layer and the slab play a major role in avalanche release, most previous approaches only considered slab properties in terms of slab depth, average density and skier penetration. For example, for the skier stability index, the additional stress (e.g. due to a skier) at the depth of the weak layer is calculated by assuming that the snow cover can be considered a semi-infinite, elastic, half-space. We suggest a new approach based on a simplification of the multi-layered elasticity theory in order to easily compute the additional stress due to a skier at the depth of the weak layer, taking into account the layering of the snow slab and the substratum. We first tested the proposed approach on simplified snow profiles, then on manually observed snow profiles including a stability test and, finally, on simulated snow profiles. Our simple approach reproduced the additional stress obtained by finite element simulations for the simplified profiles well -except that the sequence of layering in the slab cannot be replicated. Once implemented into the classical skier stability index and applied to manually observed snow profiles classified into different stability classes, the classification accuracy improved with the new approach. Finally, we implemented the refined skier stability index into the 1-D snow cover model SNOWPACK. The two study cases presented in this paper showed promising results even though further verification is still needed. In the future, we intend to implement the proposed approach for describing skier-induced stress within a multi-layered snowpack into more complex models which take into account not only failure initiation but also crack propagation.

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Triggering of dry snow slab avalanches: stress versus fracture mechanical approach

Cited by 59 publications

References 17 publications

Evaluation of slope stability with respect to snowpack spatial variability

Evaluation of slope stability with respect to snowpack spatial variability

Modeling of crack propagation in weak snowpack layers using the discrete element method

Snow instability evaluation: calculating the skier-induced stress in a multi-layered snowpack

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