Measurement of crack‐face friction in collapsed weak snow layers

Herwijnen, A. van; Heierli, Joachim

doi:10.1029/2009gl040389

Cited by 60 publications

(65 citation statements)

References 19 publications

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“…However, poorer reproducibility was found for the weak layer specific fracture energy w f due to error propagation when taking the derivative of the mechanical energy. An advantage of our method is that the effective elastic modulus can be measured on snow samples in the field, including low density snow (<150 kg m −3 ) and that w f and E ⋆ as well as other fracture mechanical properties such as collapse height, propagation speed and crack-face friction, can be extracted from the same field data (van Herwijnen and Jamieson, 2005;van Herwijnen and Heierli, 2009;van Herwijnen and others, 2010;Bair and others, 2012).…”

mentioning

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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mentioning

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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“…Generally, slab avalanches are released on slopes between 28 and 55 • (Perla, 1977;Schweizer and Lütschg, 2001;Schweizer and Jamieson, 2001). An increased release probability is generally observed above 35 • (Stoffel and Margreth, 2012). With respect to size, avalanches occurring below 35 • are often large.…”

Section: Slopementioning

confidence: 96%

“…In a shallow snowpack, terrain roughness can have a stabilising function, hindering the formation of continuous weak layers (Schweizer et al, 2003), as well as providing mechanical support to the snowpack (McClung, 2001). However, increasing snow accumulation is known to smooth out surface roughness (Veitinger et al, 2014), reducing snowpack variability in the surface layers (Mott et al, 2010) and the mechanical support of a slab (van Herwijnen and Heierli, 2009). In this case, the stabilising effects of terrain roughness disappear or even reverse (McClung and Schaerer, 2002), and the formation of continuous weak layers and slabs, which favours fracture propagation (Simenhois and Birkeland, 2008), is facilitated.…”

Section: Roughnessmentioning

confidence: 99%

Potential slab avalanche release area identification from estimated winter terrain: a multi-scale, fuzzy logic approach

Veitinger¹,

Purves

Sovilla³

2016

Nat. Hazards Earth Syst. Sci.

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Abstract. Avalanche hazard assessment requires a very precise estimation of the release area, which still depends, to a large extent, on expert judgement of avalanche specialists. Therefore, a new algorithm for automated identification of potential avalanche release areas was developed. It overcomes some of the limitations of previous tools, which are currently not often applied in hazard mitigation practice. By introducing a multi-scale roughness parameter, fine-scale topography and its attenuation under snow influence is captured. This allows the assessment of snow influence on terrain morphology and, consequently, potential release area size and location. The integration of a wind shelter index enables the user to define release area scenarios as a function of the prevailing wind direction or single storm events. A case study illustrates the practical usefulness of this approach for the definition of release area scenarios under varying snow cover and wind conditions. A validation with historical data demonstrated an improved estimation of avalanche release areas. Our method outperforms a slope-based approach, in particular for more frequent avalanches; however, the application of the algorithm as a forecasting tool remains limited, as snowpack stability is not integrated. Future research activity should therefore focus on the coupling of the algorithm with snowpack conditions.

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“…The first automated approaches to identify PRA, considering different terrain parameters, began with the availability of DTMs with quite coarse resolution in the range of 25 15 to 30 meter (Maggioni et al, 2002;Maggioni, 2005;Maggioni and Gruber, 2003). DTMs with higher spatial resolution (1 to 10 m) enable the calculation of DTM-derivatives such as ruggedness or curvature, which are of major importance for avalanche release (van Herwijnen and Heierli, 2009;McClung, 2001;Schweizer et al, 2003;Vontobel, 2011). Table 1 gives an overview on PRA delineation algorithms, published in peer-reviewed web of science journals, and the terrain derivatives they apply.…”

Section: Existing Algorithmsmentioning

confidence: 99%

Automated snow avalanche release area delineation – validation of existing algorithms and proposition of a new object-based approach for large scale hazard indication mapping

Bühler¹,

Rickenbach²,

Stoffel³

et al. 2018

Preprint

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Abstract. Snow avalanche hazard is threatening people and infrastructure in all alpine regions with seasonal or permanent snow cover around the globe. Coping with this hazard is a big challenge and during the past centuries, different strategies were 10 developed. Today, in Switzerland, experienced avalanche engineers produce hazard maps with a very high reliability based on avalanche cadastre information, terrain analysis, climatological datasets and numerical modelling of the flow dynamics for selected avalanche tracks that might affect settlements. However, for regions outside the considered settlement areas such areawide hazard maps are not available mainly because of the too high cost, in Switzerland and in most mountain regions around the world. Therefore, hazard indication maps, even though they are less reliable and less detailed, are often the only spatial 15 planning tool available. To produce meaningful and cost-effective avalanche hazard indication maps over large regions (regional to national scale), automated release area delineation has to be combined with volume estimations and state-of-theart numerical avalanche simulations.In this paper we validate existing potential release area (PRA) delineation algorithms, published in peer-reviewed journals, 20 that are based on digital terrain models and their derivatives such as slope angle, aspect, roughness and curvature. For validation, we apply avalanche cadastre data from three different ski resorts in the vicinity of Davos, Switzerland, where experienced ski-patrol staff mapped most avalanches in detail since many years. After calculating the best fit input parameters for every tested algorithm, we compare their performance based on the reference datasets. Because all tested algorithms do not provide meaningful delineation between individual potential release areas (PRA), we propose a new algorithm based on object-25 based image analysis (OBIA). In combination with an automatic procedure to estimate the average release depth (d0), defining the avalanche release volume, this algorithm enables the numerical simulation of thousands of avalanches over large regions applying the well-established avalanche dynamics model RAMMS. We demonstrate this for the region of Davos for two hazard scenarios, frequent (10 -30 years return period) and extreme (100 -300 years return period). This approach opens the door for large scale avalanche hazard indication mapping in all regions where high quality and resolution digital terrain models and 30 snow data are available.Nat. Hazards Earth Syst. Sci. Discuss., https://doi

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Measurement of crack‐face friction in collapsed weak snow layers

Cited by 60 publications

References 19 publications

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

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

Potential slab avalanche release area identification from estimated winter terrain: a multi-scale, fuzzy logic approach

Automated snow avalanche release area delineation – validation of existing algorithms and proposition of a new object-based approach for large scale hazard indication mapping

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