High-speed photography of fractures in weak snowpack layers

Herwijnen, A. van; Jamieson, Bruce

doi:10.1016/j.coldregions.2005.05.005

Cited by 54 publications

(59 citation statements)

References 13 publications

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“…This estimate from McClung [2005b] was made from only one speed measurement by Johnson et al [2004] so that scaling of speeds could not be attempted. Below, I show that the available estimates of avalanche speed by both Johnson et al [2004] and van Herwijnen and Jamieson [2005] combined with new estimates of μ by Sigrist et al [2006] are closely matched by a much lower estimate with an average proportionality factor of 0.12: …”

Section: Empirical Estimate Of Terminal Snow Slab Shear Fracture Speedsmentioning

confidence: 80%

“…The speed of a propagating shear disturbance depends on the rate at which energy is fed to the tip of the disturbance. Johnson et al [2004] provided a speed measurement of about 20 m/s for a propagating disturbance under a snow slab on horizontal terrain using seismic techniques and van Herwijnen and Jamieson [2005] have given more data from steep slopes. The data of van Herwijnen and Jamieson [2005] are from small snow slabs similar to avalanches triggered by a skier.…”

Section: Empirical Estimate Of Terminal Snow Slab Shear Fracture Speedsmentioning

confidence: 99%

“… a With measured shear fracture speeds from small skier triggered avalanches (tests 2, 3, 4, from van Herwijnen and Jamieson [2005]) and an estimate from a propagating disturbance on flat terrain (test 1, from Johnson et al [2004]). The value of μ S ( ω ) is estimated by extrapolation of the data of Camponovo and Schweizer [2001] using and the value of μ is estimated assuming ν = 0.2 to derive . …”

Section: Estimates Of the Effective Shear Modulus For Viscoelastic Anmentioning

confidence: 99%

“…Table 1 shows comparison of speed estimates from and compared with the field measurements of Johnson et al [2004] and van Herwijnen and Jamieson [2005] from small skier triggered snow slabs ( ψ is slope angle). The data from the small snow slabs were obtained by excavating a 4 m long trench along side the slope so that markers could be placed just above the weak layer to estimate the propagation speed.…”

Section: Estimates Of Terminal Snow Slab Speed Based On Limits Of Thementioning

confidence: 99%

“…I compared the estimated speed with a single measurement on horizontal terrain reported by Johnson et al [2004]. In this paper, I compare the theory with new speed data reported by van Herwijnen and Jamieson [2005] from small slabs on steep slopes triggered by skiers and the result of Johnson et al [2004]. In addition, new estimates of the elastic shear modulus are available [ Sigrist et al , 2006].…”

Section: Introductionmentioning

confidence: 99%

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Dry snow slab shear fracture speeds

McClung

2007

Geophysical Research Letters

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[1] Dry snow slab avalanches release by propagating shear fractures within thin weak layers underneath thicker, stronger planar slabs. In this paper, measured shear fracture speeds from small scale snow slabs are compared with theoretical estimates compatible with dynamic fracture mechanics. Given the important physical quantities including density and elastic shear modulus, it is concluded that estimated snow slab shear fracture speeds scale with the shear wave speed similar to estimates in other geophysical applications including shear fractures from earthquakes and in engineering materials. However, the constant of proportionality is much lower than for alpine snow than for earthquakes and engineering materials.

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Section: Empirical Estimate Of Terminal Snow Slab Shear Fracture Speedsmentioning

confidence: 80%

Section: Empirical Estimate Of Terminal Snow Slab Shear Fracture Speedsmentioning

confidence: 99%

Section: Estimates Of the Effective Shear Modulus For Viscoelastic Anmentioning

confidence: 99%

Section: Estimates Of Terminal Snow Slab Speed Based On Limits Of Thementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dry snow slab shear fracture speeds

McClung

2007

Geophysical Research Letters

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Der Knall im Lawinenhang. Die Ursache von Schneebrettlawinen

Heierli¹,

Zaiser

Gumbsch

2009

Physik in unserer Zeit

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Der Scherbruch gilt allgemein als Ursache für Schneebrettlawinen. Scherbrüche können sich allerdings in einer wenig geneigten Schneedecke nicht ausbreiten, da keine ausreichenden Scherkräfte vorliegen. Dennoch wird Bruchausbreitung im flachen Gelände oft beobachtet und führt auch zu zahlreichen Lawinenunfällen durch Fernauslösung. Dieser Widerspruch wurde von der Schneeforschung bisher nicht erkannt. Ein Ansatz aus der Materialforschung erklärt nun diesen Zusammenhang: Beim Bruchprozess eines kohäsiv‐granularen Materials wie Schnee werden die abgebrochenen Schneekörner in die porösen Zwischenräume gepresst, so dass die ungewöhnliche Versagensform des Antirisses zum Tragen kommt. Es lässt sich erklären, warum sich Antirisse selbst bei beliebig großer Bruchflächenreibung durch eine horizontale Schneedecke ausbreiten können.

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Numerical investigation of crack propagation regimes in snow fracture experiments

Bobillier,

Bergfeld,

Dual

et al. 2024

Granular Matter

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A snow slab avalanche releases after failure initiation and crack propagation in a highly porous weak snow layer buried below a cohesive slab. While our knowledge of crack propagation during avalanche formation has greatly improved over the last decades, it still remains unclear how snow mechanical properties affect the dynamics of crack propagation. This is partly due to a lack of non-invasive measurement methods to investigate the micro-mechanical aspects of the process. Using a DEM model, we therefore analyzed the influence of snow cover properties on the dynamics of crack propagation in weak snowpack layers. By focusing on the steady-state crack speed, our results showed two distinct fracture process regimes that depend on slope angle, leading to very different crack propagation speeds. For long experiments on level terrain, weak layer fracture is mainly driven by compressive stresses. Steady-state crack speed mainly depends on slab and weak layer elastic moduli as well as weak layer strength. We suggest a semi-empirical model to predict crack speed, which can be up to 0.6 times the slab shear wave speed. For long experiments on steep slopes, a supershear regime appeared, where the crack propagation speed reached approximately 1.6 times the slab shear wave speed. A detailed micro-mechanical analysis of stresses revealed a fracture principally driven by shear. Overall, our findings provide new insight into the micro-mechanics of dynamic crack propagation in snow, and how these are linked to snow cover properties. Graphical Abstract

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High-speed photography of fractures in weak snowpack layers

Cited by 54 publications

References 13 publications

Dry snow slab shear fracture speeds

Dry snow slab shear fracture speeds

Der Knall im Lawinenhang. Die Ursache von Schneebrettlawinen

Numerical investigation of crack propagation regimes in snow fracture experiments

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