On size and shape effects in snow fracture toughness measurements

Sigrist, Christian; Schweizer, Jürg; Schindler, Hans-Jakob; Dual, Jürg

doi:10.1016/j.coldregions.2005.05.001

Cited by 19 publications

(29 citation statements)

References 19 publications

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“…The average weak layer elastic modulus E WL of our samples was 11.6 MPa ( Figure 10). The mixed mode interfacial fracture toughness for a shear fracture along a weak layer resulted in 0.49 ± 0.36 kPa m 1/2 which is about a factor of four lower than the fracture toughness in mode I for samples of similar snow density (Sigrist et al, 2005).…”

Section: Comparison With Mode I Resultsmentioning

confidence: 75%

“…The experimental set-up suggests to use a cantilever beam approach to calculate the energy release rate G. Sigrist et al (2005) used cantilever beams to determine the fracture toughness in mode I with homogeneous snow samples. Since in our case one layer of the specimen was supported and fixed by icing, the fracture energy was assumed to mainly depend on the elastic properties of the protruding layer (E 1 ).…”

Section: Cantilever Beam With Deep Crackmentioning

confidence: 99%

“…Recently, several studies were made to determine snow fracture toughness in mode I (Kirchner et al, 2000;Faillettaz et al, 2002;Sigrist et al, 2005) and in mode II (Kirchner et al, 2002a, b;Schweizer et al, 2004). For a density of 200 kg m −3 a mode I fracture toughness of about 0.5-1 kPa m 1/2 was measured, indicating that snow is a very brittle material.…”

Section: Introductionmentioning

confidence: 99%

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The energy release rate of mode II fractures in layered snow samples

et al. 2006

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Before a dry snow slab avalanche is released, a shear failure along a weak layer or an interface has to take place. This shear failure disconnects the overlaying slab from the weak layer. A better understanding of this fracture mechanical process, which is a key process in slab avalanche release, is essential for more accurate snow slope stability models. The purpose of this work was to design and to test an experimental set-up for a mode II fracture test with layered snow samples and to find a method to evaluate the interfacial fracture toughness or alternatively the energy release rate in mode II. Beam-shaped specimens were cut out of the layered snow cover, so that they consisted of two homogeneous snow layers separated by a well defined interface. In the cold laboratory 27 specimens were tested using a simple cantilever beam test. The test method proved to be applicable in the laboratory, although the handling of layered samples was delicate. An energy release rate for snow in mode II was calculated numerically with a finite element (FE) model and analytically using an approach for a deeply cracked cantilever beam. An analytical bilayer approach was not suitable. The critical energy release rate G c was found to be 0.04 ± 0.02 J m −2 . It was primarily a material property of the weak layer and did not depend on the elastic properties of the two adjacent snow layers. The mixed mode interfacial fracture toughness for a shear fracture along a weak layer estimated from the critical energy release rate was substantially lower than the mode I fracture toughness found for snow of similar density.

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Section: Comparison With Mode I Resultsmentioning

confidence: 75%

Section: Cantilever Beam With Deep Crackmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The energy release rate of mode II fractures in layered snow samples

et al. 2006

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“…The asymptotic value of G still occurred around l = 2 m for both versions of the model. Thus, while viscoelastic effects may be important for an accurate estimate for G (i.e., Bažant et al, 2003;McClung, 2005;Sigrist et al, 2005;McClung and Schweizer, 2006), they did not affect where G reached its asymptotic value. Comparison of both model results show that the far edge effect on G was eliminated in beams with l ≥ 2 m.…”

Section: Appendix A: Viscoelastic Effectsmentioning

confidence: 93%

The influence of edge effects on crack propagation in snow stability tests

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Simenhois²,

Herwijnen³

et al. 2014

The Cryosphere

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Abstract. The Extended Column Test (ECT) and the Propagation Saw Test (PST) are two commonly used tests to assess the likelihood of crack propagation in a snowpack. Guidelines suggest beams with lengths of around 1 m, yet little is known about how test length affects propagation. Thus, we performed 163 ECTs and PSTs 1.0-10.0 m long. On days with full crack propagation in 1.0-1.5 m tests, we then made videos of tests 2.0-10.0 m long. We inserted markers for particle tracking to measure collapse amplitude, propagation speed, and wavelength. We also used a finite element (FE) model to simulate the strain energy release rate at fixed crack lengths. We find that (1) the proportion of tests with full propagation decreased with test length; (2) collapse was greater at the ends of the beams than in the centers; (3) collapse amplitude was independent of beam length and did not reach a constant value; (4) collapse wavelengths in the longer tests were around 3 m, two times greater than what is predicted by the anticrack model. We also confirmed the prediction that centered PSTs had double the critical length of edge PSTs. Based on our results, we conclude that cracks propagated more frequently in the shorter tests because of increased stress concentration from the far edge. The FE model suggests this edge effect occurs for PSTs of up to 2 m long or a crack to beam length ratio ≥ 0.20. Our results suggest that ECT and PST length guidelines may need to be revisited.

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“…The fracture of homogeneous snow is yet not fully understood [Sigrist et al, 2005]. For agglomerates, the strength of an agglomerate is expected to depend on the bonding mechanism as discussed by [Mishra and Thornton, 2001].…”

Section: Discussionmentioning

confidence: 99%