A dynamic method to measure the shear strength of snow

Nakamura, Tsutomu; Abe, Osamu; Hashimoto, Ryuhei; Ohta, Takeshi

doi:10.3189/002214310791968502

Cited by 24 publications

(33 citation statements)

References 14 publications

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“…Since then, numerous experimental studies investigated the effects of normal load on shear strength of snow and snow weak layers, mainly through shear frame or shear vane tests. Results showing an influence of normal stress on various snow types were reported by Roch (1966), DeMontmollin (1978DeMontmollin ( , 1982, McClung (1977), Perla and Beck (1983) and Navarre et al (1992). Jamieson and Johnston (1998) reported similar influence on non-persistent weak layers, but found no significant effect on persistent weak layers, thus proposing φ = 0 • .…”

Section: Objectives and Scope Of The Studymentioning

confidence: 69%

“…Overall, most of these studies investigated the influence of normal pressure using shear-frames. Results obtained with alternative methods, like shaking-platform tests (Nakamura et al, 2010;Podolskiy et al, 2010b), may provide valuable new insights on these issues of normal stress influence and applicability of Mohr-Coulomb criterion, and thus still remain to be analysed in that context.…”

Section: Objectives and Scope Of The Studymentioning

confidence: 99%

“…This paper is based on a series of experiments using the shaking platform as described by Nakamura et al (2010) and Podolskiy et al (2010b summarised as follows: snow samples were frozen to the platform and loaded via inertia through horizontal oscillations with a constant amplitude of 1.65 cm and with growing frequency (see Sect. 4.1.4 for details).…”

Section: Shaking-platform Experimentsmentioning

confidence: 99%

“…The frequency increase caused gains in velocity, acceleration, and thus stresses within the samples; at the point when the stress exceeded the strength of snow, the sample failed. High-speed video records, accelerometers and measurement of the fractured mass revealed the instant of failure and the corresponding peak acceleration (in the range of 2.23-6.36 g) (Nakamura et al, 2010;Podolskiy et al, 2010b). Originally, this dynamic experimental approach was developed for studying the shear strength properties of snow and their relationship to vibrations Nakamura, 2000, 2005;Nakamura et al, 2000aNakamura et al, , b, 2010.…”

Section: Shaking-platform Experimentsmentioning

confidence: 99%

“…Nevertheless, free surfaces on five sides of the sample and the probable occurrence of stress heterogeneities in the snow block due to edge effects restrict the possibility of simple stress assessments and relating the experimental results to a real snowpack at slope scales. For example, an attempt by Nakamura et al (2010) to calculate dependence of shear strength on presumably constant overburden pressure produced surprisingly high values of internal friction angle (73.4-83.1 • ) with zero cohesion, thus exemplifying the importance of understanding normal stress variations in the experiments for reliable interpretations. The experiments, considered in this study, were performed in a cold laboratory (with an ambient air temperature of −10 • C) on artificial "sandwich" snow samples constituted of two blocks of snow, with a weak layer made of low density snow placed approximately at mid height.…”

Section: Shaking-platform Experimentsmentioning

confidence: 99%

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Evaluating snow weak-layer failure parameters through inverse finite element modelling of shaking-platform experiments

Podolskiy¹,

Chambon²,

Naaïm³

et al. 2015

Nat. Hazards Earth Syst. Sci.

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Abstract. Snowpack weak layers may fail due to excess stresses of various natures, caused by snowfall, skiers, explosions or strong ground motion due to earthquakes, and lead to snow avalanches. This research presents a numerical model describing the failure of "sandwich" snow samples subjected to shaking. The finite element model treats weak layers as interfaces with variable mechanical parameters. This approach is validated by reproducing cyclic loading snow fracture experiments. The model evaluation revealed that the Mohr-Coulomb failure criterion, governed by cohesion and friction angle, was adequate to describe the experiments. The model showed the complex, non-homogeneous stress evolution within the snow samples and especially the importance of tension on fracture initiation at the edges of the weak layer, caused by dynamic stresses due to shaking. Accordingly, a simplified analytical solution, ignoring the inhomogeneity of tangential and normal stresses along the failure plane, may incorrectly estimate the shear strength of the weak layers. The values for "best fit" cohesion and friction angle were ≈ 1.6 kPa and 22.5-60 • . These may constitute valuable first approximations in mechanical models used for avalanche forecasting.

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Section: Objectives and Scope Of The Studymentioning

confidence: 69%

Section: Objectives and Scope Of The Studymentioning

confidence: 99%

Section: Shaking-platform Experimentsmentioning

confidence: 99%

Section: Shaking-platform Experimentsmentioning

confidence: 99%

Section: Shaking-platform Experimentsmentioning

confidence: 99%

See 3 more Smart Citations

Evaluating snow weak-layer failure parameters through inverse finite element modelling of shaking-platform experiments

Podolskiy¹,

Chambon²,

Naaïm³

et al. 2015

Nat. Hazards Earth Syst. Sci.

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Measurement of the physical properties of the snowpack

Kinar

Pomeroy

2015

Reviews of Geophysics

196

202

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This paper reviews measurement techniques and corresponding devices used to determine the physical properties of the seasonal snowpack from distances close to the ground surface. The review is placed in the context of the need for scientific observations of snowpack variables that provide inputs for predictive hydrological models that help to advance scientific understanding of geophysical processes related to snow in the near-surface cryosphere. Many of these devices used to measure snow are invasive and require the snowpack to be disrupted, thereby precluding the possibility for multiple measurements to be made at the same sampling location. Moreover, many devices rely on the use of empirical calibration equations that may not be valid at all geographic locations. The spatial density of observations with most snow measurement devices is often inadequate. There is a need for improved automation of snowpack measurement instrumentation with an emphasis on field-based feedback of measurement validity in lieu of postprocessing of samples or data at a lab or office location. The scientific future of snow measurement instrumentation thereby requires a synthesis between science and engineering principles that takes into consideration geophysics and the physics of device operation.

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A higher‐order method for determining quasi‐brittle tensile fracture parameters governing the release of slab avalanches and a new tool for in situ indexing

Borstad

McClung

2013

JGR Earth Surface

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[1] The tensile fracture of heterogeneous earth materials such as snow, ice, and rocks can be characterized by two fracture parameters-the fracture toughness and the fracture process zone length. The latter length scale characterizes the zone of microcracking surrounding a crack tip in a heterogeneous material. For alpine snow, these two fracture parameters influence the release dimensions and thus destructive potential of slab avalanches. In general, it is difficult to determine these parameters concurrently, and most experimental methods are based on first-order scaling laws that have considerable errors unless very large test specimens are used. Here we introduce a simple experimental method based on a higher-order quasi-brittle scaling law that has never been applied to snow nor any other geophysical material. We conducted hundreds of beam bending experiments using natural cohesive snow samples to produce the most comprehensive measurements to date of the tensile fracture toughness and effective process zone length of snow. We also adopt a new penetration resistance gauge to index the fracture toughness data, addressing a longstanding need for better proxy measurements to characterize snow structure. The peak penetration resistance met by a thin blade proved better than the bulk snow density for predicting fracture toughness, a finding that will improve field predictions and facilitate comparisons of results across studies. The tensile fracture process zone, previously a highly uncertain length scale related to avalanche fractures, is shown to be about 5-10 times the snow grain size, implying nonlinear fracture scaling for the majority of avalanches.Citation: Borstad, C. P., and D. M. McClung (2013), A higher-order method for determining quasi-brittle tensile fracture parameters governing the release of slab avalanches and a new tool for in situ indexing,

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A dynamic method to measure the shear strength of snow

Cited by 24 publications

References 14 publications

Evaluating snow weak-layer failure parameters through inverse finite element modelling of shaking-platform experiments

Evaluating snow weak-layer failure parameters through inverse finite element modelling of shaking-platform experiments

Measurement of the physical properties of the snowpack

A higher‐order method for determining quasi‐brittle tensile fracture parameters governing the release of slab avalanches and a new tool for in situ indexing

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