Modeling snow slab avalanches caused by weak-layer failure – Part 1: Slabs on compliant and collapsible weak layers

Rosendahl, Philipp Laurens; Weißgraeber, Philipp

doi:10.5194/tc-14-115-2020

Cited by 24 publications

(16 citation statements)

References 46 publications

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“…Collapse height was taken as the mean of the settlement of the slab measured after crack propagation. For the elastic moduli, 220 displacement fields with an increasing crack length prior to crack propagation were used to compare to displacement fields predicted by the mechanical model established by Rosendahl and Weissgraeber (2020a). The optimal set of E sl and E wl was estimated by minimising the residual, with E sl and E wl as free-fitting parameters.…”

Section: Methodsmentioning

confidence: 99%

Crack propagation speeds in weak snowpack layers

Bergfeld¹,

Herwijnen²,

Bobillier³

et al. 2021

J. Glaciol.

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For the release of a slab avalanche, crack propagation within a weak snowpack layer below a cohesive snow slab is required. As crack speed measurements can give insight into underlying processes, we analysed three crack propagation events that occurred in similar snowpacks and covered all scales relevant for avalanche release. For the largest scale, up to 400 m, we estimated crack speed from an avalanche movie; for scales between 5 and 25 m, we used accelerometers placed on the snow surface and for scales below 5 m, we performed a propagation saw test. The mean crack speeds ranged from 36 ± 6 to 49 ± 5 m s−1, and did not exhibit scale dependence. Using the discrete element method and the material point method, we reproduced the measured crack speeds reasonably well, in particular the terminal crack speed observed at smaller scales. Finally, we used a finite element model to assess the speed of different elastic waves in a layered snowpack. Results suggest that the observed cracks propagated as mixed mode closing cracks and that the flexural wave of the slab is responsible for the energy transfer to the crack tip.

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Section: Methodsmentioning

confidence: 99%

Crack propagation speeds in weak snowpack layers

Bergfeld¹,

Herwijnen²,

Bobillier³

et al. 2021

J. Glaciol.

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“…The microscopic snow structure and ice properties must be considered for modeling snow mechanical properties and failure initialization. Snow stratigraphy and mechanical properties of snow need to be considered for modeling crack propagation (e.g., [36,38,39]). At the slope-scale, spatial variations of snow stratigraphy and terrain are essential to model avalanche release (e.g., [40,41]).…”

Section: Models In Snow Mechanicsmentioning

confidence: 99%

Studying Snow Failure With Fiber Bundle Models

Capelli¹,

Reiweger

Schweizer³

2020

Front. Phys.

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Snow is a highly porous material with properties that may strongly differ depending on the environmental conditions. On slopes, the layered snowpack may fail and avalanches occur. Hence, knowing how snow deforms and fails is essential for understanding and modeling snow avalanche release and flow. The response of snow to imposed load or deformation and the failure behavior depends on the rate of the applied load or of displacement and follows from the complex, foam like, microstructure of snow and the properties of ice. The mechanical response and failure of snow can well be captured with fiber bundle models (FBM). We review the use of FBMs for studying snow failure. In particular, we show how FBMs have been used for studying the micromechanical processes, such as ice sintering and viscous deformation, to reproduce the results of snow failure experiments. Moreover, FBMs can reproduce signatures of acoustic emissions (AE) preceding snow failure, ease the AE interpretation, and shed light on the underlying progressive failure process.

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“…Sigrist and Schweizer (2007) were the first to estimate w f for snow (mean 0.07 J m −2 ), combining field experiments with finite element (FE) modelling. Their method used the critical cut length from a PST and snow micro-penetrometer (SMP) measurements (Schneebeli and Johnson, 1998) to estimate the effective elastic modulus of the slab. Using the same approach, Schweizer et al (2011) reported values an order of magnitude larger, typically around 1 J m −2 .…”

Section: Introductionmentioning

confidence: 99%

Dynamic crack propagation in weak snowpack layers: insights from high-resolution, high-speed photography

Bergfeld¹,

Herwijnen²,

Reuter

et al. 2021

The Cryosphere

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Abstract. Dynamic crack propagation in snow is of key importance for avalanche release. Nevertheless, it has received very little experimental attention. With the introduction of the propagation saw test (PST) in the mid-2000s, a number of studies have used particle tracking analysis of high-speed video recordings of PST experiments to study crack propagation processes in snow. However, due to methodological limitations, these studies have provided limited insight into dynamical processes such as the evolution of crack speed within a PST or the touchdown distance, i.e. the length from the crack tip to the trailing point where the slab comes to rest on the crushed weak layer. To study such dynamical effects, we recorded PST experiments using a portable high-speed camera with a horizontal resolution of 1280 pixels at rates of up to 20 000 frames s−1. We then used digital image correlation (DIC) to derive high-resolution displacement and strain fields in the slab, weak layer and substrate. The high frame rates enabled us to calculate time derivatives to obtain velocity and acceleration fields. We demonstrate the versatility and accuracy of the DIC method by showing measurements from three PST experiments, resulting in slab fracture, crack arrest and full propagation. We also present a methodology to determine relevant characteristics of crack propagation, namely the crack speed (20–30 m s−1), its temporal evolution along the column and touchdown distance (2.7 m) within a PST, and the specific fracture energy of the weak layer (0.3–1.7 J m−2). To estimate the effective elastic modulus of the slab and weak layer as well as the weak layer specific fracture energy, we used a recently proposed mechanical model. A comparison to already-established methods showed good agreement. Furthermore, our methodology provides insight into the three different propagation results found with the PST and reveals intricate dynamics that are otherwise not accessible.

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Modeling snow slab avalanches caused by weak-layer failure – Part 1: Slabs on compliant and collapsible weak layers

Cited by 24 publications

References 46 publications

Crack propagation speeds in weak snowpack layers

Crack propagation speeds in weak snowpack layers

Studying Snow Failure With Fiber Bundle Models

Dynamic crack propagation in weak snowpack layers: insights from high-resolution, high-speed photography

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