Temporal evolution of crack propagation characteristics in a weak snowpack layer: conditions of crack arrest and sustained propagation

Bergfeld, Bastian; Herwijnen, Alec van; Bobillier, Grégoire; Rosendahl, Philipp Laurens; Weißgraeber, Philipp; Adam, Valentin; Dual, Jürg; Schweizer, Jürg

doi:10.5194/nhess-23-293-2023

Cited by 5 publications

(6 citation statements)

References 52 publications

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“…Experimental validations are challenging since direct measurements of stresses are not possible and displacement measurements require considerable experimental effort. The latter can be recorded using digital image correlation (DIC) as demonstrated by Bergfeld et al (2023a). From their analysis, we use the DIC-recorded displacement field of the first 1.3 m of a 3.0 ± 0.1 m long flat-field propagation saw test (Fig.…”

Section: Finite-element Reference Modelmentioning

confidence: 99%

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A closed-form model for layered snow slabs

Weißgraeber¹,

Rosendahl²

2023

The Cryosphere

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Abstract. We propose a closed-form analytical model for the mechanical behavior of stratified snow covers for the purpose of investigating and predicting the physical processes that lead to the formation of dry-snow slab avalanches. We represent the system of a stratified snow slab covering a collapsible weak layer by a beam composed of an arbitrary number of layers supported by an anisotropic elastic foundation in a two-dimensional plane-strain model. The model makes use of laminate mechanics and provides slab deformations, stresses in the weak layer, and energy release rates of weak-layer anticracks in real time. The quantities can be used in failure models of avalanche release. The closed-form solution accounts for the layering-induced coupling of bending and extension in the slab and of shear and normal stresses in the weak layer. It is validated against experimentally recorded displacement fields and a comprehensive finite-element model indicating very good agreement. We show that layered slabs cannot be homogenized into equivalent isotropic bodies and reveal the impact of layering on bridging with respect to weak-layer stresses and energy release rates. It is demonstrated that inclined propagation saw tests allow for the determination of mixed-mode weak-layer fracture toughnesses. Our results suggest that such tests are dominated by mode I when cut upslope and comprise significant mode II contributions when cut downslope. A Python implementation of the presented model is publicly available as part of the Weak Layer Anticrack Nucleation Model (WEAC) software package under https://github.com/2phi/weac (last access: 28 March 2023) and https://pypi.org/project/weac (last access: 28 March 2023, Rosendahl and Weißgraeber, 2022).

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Section: Finite-element Reference Modelmentioning

confidence: 99%

“…Figure 10 shows weak-layer fracture toughnesses determined from critical cut lengths of PSTs with layered slabs throughout the 2019 winter season using the present model. Details of the tests are reported by Bergfeld et al (2023a, b). The authors performed 21 tests on the same weak layer.…”

Section: Weak-layer Stresses and Energy Release Ratesmentioning

confidence: 99%

A closed-form model for layered snow slabs

Weißgraeber¹,

Rosendahl²

2023

The Cryosphere

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“…Dry-snow slab avalanches, the most destructive avalanches, release due to the failure of a mechanically weak snow layer buried below a cohesive slab (e.g. Bobillier et al, 2021;Bergfeld et al, 2023). Most dry-snow slab avalanches release naturally during or shortly after a snowstorm, but artificial triggering, for instance by skiers, is also possible.…”

Section: Introductionmentioning

confidence: 99%

Changes in snow avalanche activity in response to climate warming in the Swiss Alps

Mayer,

Hendrick,

Michel

et al. 2024

Preprint

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Abstract. The cryosphere in mountain regions is rapidly transforming due to climate warming, yet the impact of these changes on snow avalanche activity remains uncertain. Here, we use a snow cover model driven by downscaled climate projections to evaluate future alterations in dry- and wet-snow avalanche occurrences throughout the 21st century in the Swiss Alps. We assess avalanche activity by employing machine learning models trained with observed records of avalanches. Our findings indicate an overall decline in the occurrence of dry-snow avalanches during the months December to May that is partially compensated by an increase in wet-snow avalanche activity. Depending on elevation and the emission scenario considered, we anticipate a net reduction in total avalanche activity ranging from under 10 % to as much as 60 % by the end of the century. Projections further reveal a shift of wet-snow avalanche activity to earlier winter months. Analysis of changes in prominent snow grain types offers a coherent explanation of projected changes beyond a mere decrease in snow depth and snow cover duration. Overall, our study quantifies for the first time the significant influence of climate change on snow avalanche activity in the Swiss Alps and may serve as a benchmark for further mountain regions with similar avalanche climates.

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“…Bergfeld and others (2021) and Bergfeld and others (2018) used Digital Image Correlation (DIC) to measure crack speeds between 20 and 30 m s −1 and between 37 and 45 m s −1 , respectively, in a 3.3 m PSTs. Bergfeld and others (2018Bergfeld and others ( , 2022Bergfeld and others ( , 2023 used DIC again to measure crack propagation speeds on long PSTexperiments (up to 9 m long) over the entire life cycle of a weak layer. They measured speeds as fast as 55 ± 8 m s −1 .…”

Section: Introductionmentioning

confidence: 99%

Using video detection of snow surface movements to estimate weak layer crack propagation speeds

Simenhois¹,

Birkeland

Gaume

et al. 2023

Ann. Glaciol.

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Dry-snow slab avalanches release due to crack propagation in a weak snow layer under a cohesive snow slab. Crack propagation speeds can provide insights into the potential size of avalanches and inform fracture and avalanche release models. Despite their importance, slope-scale crack speed measurements from real avalanches are limited. Further, most existing slope-scale measurements utilize the appearance of slab fractures on the snow surface. However, we have no evidence that the appearance of surface cracking is a good indicator of the weak layer crack propagation tip. Here we present a novel method to estimate crack propagation speed from snow surface movements in avalanche videos. Our technique uses changes in frame pixel intensity, allowing us to detect the location of weak layer cracks well before slab fractures appear on the snow surface. We use field experiments and numerical simulations to validate our method before applying it to five avalanches. Our estimates show that cracks propagate faster up and down the slope than in the cross-slope direction; this suggests that different propagation regimes likely govern crack propagation up/down the slope, cross-slope and in flat terrain.

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Temporal evolution of crack propagation characteristics in a weak snowpack layer: conditions of crack arrest and sustained propagation

Cited by 5 publications

References 52 publications

A closed-form model for layered snow slabs

A closed-form model for layered snow slabs

Changes in snow avalanche activity in response to climate warming in the Swiss Alps

Using video detection of snow surface movements to estimate weak layer crack propagation speeds

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