Micro-mechanical insights into the dynamics of crack propagation in snow fracture experiments

Bobillier, Grégoire; Bergfeld, Bastian; Dual, Jürg; Gaume, Johan; Herwijnen, Alec van; Schweizer, Jürg

doi:10.1038/s41598-021-90910-3

Cited by 16 publications

(26 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For a detailed description of the DEM model for snow, and in particular how particle (and particle contact) parameters relate to macroscopic snow parameters, refer to Bobillier and others (2020). Recently, Bobillier and others (2021) modelled the PST design and showed that crack propagation in weak snow layers can be reproduced with their DEM model (Fig. 7a).…”

Section: Methodsmentioning

confidence: 90%

Crack propagation speeds in weak snowpack layers

Bergfeld¹,

Herwijnen²,

Bobillier³

et al. 2021

J. Glaciol.

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Methodsmentioning

confidence: 90%

Crack propagation speeds in weak snowpack layers

Bergfeld¹,

Herwijnen²,

Bobillier³

et al. 2021

J. Glaciol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…To correct for radial and tangential image distortion introduced by the camera lens, we used calibration factors using a pinhole camera model. The distortion coefficients k 1 , k 2 , k 3 , p 1 and p 2 as well as the camera model were estimated using chessboard calibration images and routines using OpenCV for Python (Bradski and Kaehler, 2008). The distortion coefficients are constant, as these only depend on lens characteristics.…”

Section: Camera Distortion Correctionmentioning

confidence: 99%

“…For closing cracks, as is the case in our experiments, no generally valid definition exists. Therefore, we evaluated similar methods as Bobillier et al (2021) to estimate crack propagation speed.…”

Section: Crack Speed and Touchdown Distancementioning

confidence: 99%

See 1 more Smart Citation

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

Bergfeld¹,

Herwijnen²,

Reuter

et al. 2021

The Cryosphere

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…[ 34 ] implemented such model to investigate the erosion of an immersed cohesive geomaterial. Several studies focused on snowpack stability [ 35 – 39 ] used a similar contact model to model the sintering of snow as a solid beam joining two particles when they are in contact. The DEM contact model that we use in this work, is based on the latter.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of the effect of cohesion and ground friction on snow avalanches flow regimes

Ligneau

Sovilla²,

Gaume

2022

PLoS ONE

View full text Add to dashboard Cite

With ongoing global warming, snow avalanche dynamics may change as snow cohesion and friction strongly depend on temperature. In the field, a diversity of avalanche flow regimes has been reported including fast, sheared flows and slow plugs. While the significant role of cohesion and friction has been recognized, it is unclear how these mechanical properties affect avalanche flow regimes. Here, we model granular avalanches on a periodic inclined plane, using the distinct element method to better understand and quantify how inter-particle cohesion and ground friction influences avalanche velocity profiles. The cohesion between particles is modeled through bonds that can subsequently break and form, thus representing fragmentation and aggregation potentials, respectively. The implemented model shows a good ability to reproduce the various flow regimes and transitions as observed in nature: for low cohesion, highly sheared and fast flows are obtained while slow plugs form above a critical cohesion value and for lower ground frictions. Simulated velocity profiles are successfully compared to experimental measurements from the real-scale test site of Vallée de la Sionne in Switzerland. Even though the model represents a strong simplification of the reality, it offers a solid basis for further investigation of relevant processes happening in snow avalanches, such as segregation, erosion and entrainment, with strong impacts on avalanche dynamics research, especially in a climate change context.

show abstract

Micro-mechanical insights into the dynamics of crack propagation in snow fracture experiments

Cited by 16 publications

References 35 publications

Crack propagation speeds in weak snowpack layers

Crack propagation speeds in weak snowpack layers

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

Numerical investigation of the effect of cohesion and ground friction on snow avalanches flow regimes

Contact Info

Product

Resources

About