Critical energy release rates of weak snowpack layers determined in field experiments

Sigrist, Christian; Schweizer, Jürg

doi:10.1029/2006gl028576

Cited by 79 publications

(98 citation statements)

References 15 publications

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“…During the past decade, our understanding of the fracture process in snow has gradually evolved through the development of new theories as well as various field observations and experiments. The propagation saw test (PST), concurrently developed in Canada (van Herwijnen and Jamieson, 2005;Gauthier and Jamieson, 2006) and Switzerland (Sigrist and Schweizer, 2007), consists in isolating a snow column and initiating a crack of increasing length in the weak layer with a snow saw until the onset of rapid self-propagation of the crack. The PST allows observers to determine the critical crack length and evaluate crack propagation propensity.…”

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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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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“…Several studies introduced indirect methods to derive mechanical snow properties from field experiments. Sigrist and Schweizer (2007) were the first to estimate w f with field experiments and finite element (FE) modeling. Their method requires a Propagation Saw Test (PST;van Herwijnen and Jamieson, 2005;Sigrist and Schweizer, 2007;Gauthier and Jamieson, 2008) to determine the critical cut length r c and a snow micro-penetrometer measurement (SMP; Schneebeli and Johnson, 1998) to estimate the effective elastic modulus E of the slab.…”

Section: Introductionmentioning

confidence: 99%

“…Their method requires a Propagation Saw Test (PST;van Herwijnen and Jamieson, 2005;Sigrist and Schweizer, 2007;Gauthier and Jamieson, 2008) to determine the critical cut length r c and a snow micro-penetrometer measurement (SMP; Schneebeli and Johnson, 1998) to estimate the effective elastic modulus E of the slab. While Sigrist and Schweizer (2007) reported a mean fracture energy of 0.07 J m −2 , more recent results using the same methodology on eight different weak layers indicate substantially larger values, typically around 1 J m -2 (Schweizer and others, 2011). Similar values (between 0.5 and 2 J m −2 ) were also found by Reuter and others (2013) and Reuter and others (2015) by integrating the penetration force signal of the SMP over the weak layer thickness.…”

Section: Introductionmentioning

confidence: 99%

Estimating the effective elastic modulus and specific fracture energy of snowpack layers from field experiments

Herwijnen¹,

Gaume²,

Bair

et al. 2016

J. Glaciol.

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ABSTRACT. Measurements of the mechanical properties of snow are essential for improving our understanding and the prediction of snow failure and hence avalanche release. We performed fracture mechanical experiments in which a crack was initiated by a saw in a weak snow layer underlying cohesive snow slab layers. Using particle tracking velocimetry (PTV), the displacement field of the slab was determined and used to derive the mechanical energy of the system as a function of crack length. By fitting the estimates of mechanical energy to an analytical expression, we determined the slab effective elastic modulus and weak layer specific fracture energy for 80 different snowpack combinations, including persistent and nonpersistent weak snow layers. The effective elastic modulus of the slab ranged from 0.08 to 34 MPa and increased with mean slab density following a power-law relationship. The weak layer specific fracture energy ranged from 0.08 to 2.7 J m −2 and increased with overburden. While the values obtained for the effective elastic modulus of the slab agree with previously published low-frequency laboratory measurements over the entire density range, the values of the weak layer specific fracture energy are in some cases unrealistically high as they exceeded those of ice. We attribute this discrepancy to the fact that our linear elastic approach does not account for energy dissipation due to non-linear parts of the deformation in the slab and/or weak layer, which would undoubtedly decrease the amount of strain energy available for crack propagation.

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“…[2] The physical properties of the natural snowpack are of great importance for many geophysical processes such as heat transfer [Kaempfer et al, 2005;Sturm et al, 2002], interaction with the turbulent boundary layer [Lehning et al, 2002], wind erosion [Clifton et al, 2006], failure and crack propagation [Sigrist and Schweizer, 2007;Heierli and Zaiser, 2006]. However, the ice structure within a natural snowpack is a non-equilibrium system which undergoes metamorphic changes induced by many physical and chemical processes [see, e.g., Arons and Colbeck, 1995;Schweizer et al, 2003, and references therein].…”

Section: Introductionmentioning

confidence: 99%

On the evolution of the snow surface during snowfall

Löwe¹,

Egli²,

Bartlett³

et al. 2007

Geophysical Research Letters

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[1] The deposition and attachment mechanism of settling snow crystals during snowfall dictates the very initial structure of ice within a natural snowpack. In this letter we apply ballistic deposition as a simple model to study the structural evolution of the growing surface of a snowpack during its formation. The roughness of the snow surface is predicted from the behaviour of the time dependent height correlation function. The predictions are verified by simple measurements of the growing snow surface based on digital photography during snowfall. The measurements are in agreement with the theoretical predictions within the limitations of the model which are discussed. The application of ballistic deposition type growth models illuminates structural aspects of snow from the perspective of formation which has been ignored so far. Implications of this type of growth on the aerodynamic roughness length, density, and the density correlation function of new snow are discussed. Citation: Löwe, H., L. Egli, S. Bartlett, M. Guala, and C. Manes (2007), On the evolution of the snow surface during snowfall, Geophys.

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Critical energy release rates of weak snowpack layers determined in field experiments

Cited by 79 publications

References 15 publications

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

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

Estimating the effective elastic modulus and specific fracture energy of snowpack layers from field experiments

On the evolution of the snow surface during snowfall

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