A closed-form model for layered snow slabs

Weißgraeber, Philipp; Rosendahl, Philipp Laurens

doi:10.5194/tc-2022-140

Cited by 4 publications

(10 citation statements)

References 46 publications

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“…Using the virtual crack closure technique allows for the identiőcation of the ERR of a given crack length and the separation of both contributions. 35 For the 𝑎 c values recorded in our experiments, Fig. 1d shows computed critical shearing mode ERRs (𝒢 II ) as a fraction of the corresponding total ERRs (𝒢 = 𝒢 I + 𝒢 II ).…”

Section: Weak-layer Anticracks Are Controlled By Fracture Toughnessmentioning

confidence: 93%

“…1c), conőrming recent theoretical considerations of the differences in shear loading of upslope and downslope cuts. 35…”

Section: Cut Lengths Increase With Slope Anglementioning

confidence: 99%

“…To analyze PST data, we consider a closed-form analytical solution for a őrst-order, shear-deformable, layered plate under cylindrical bending (slab) that is supported by an elastic foundation (weak layer). 35 The anisotropy induced by the layered nature of snow slabs is accounted for by a stiffness matrix that distinguishes extension, bending, shear, and bendingśextension coupled deformations. Here, we extend the model to consider additional surface loads as used in the present experimental setup (cf.…”

mentioning

confidence: 99%

“…Mode I and II energy release rates are calculated from the stresses and displacements in the weak interface. The model was validated with comprehensive numerical studies, 19,35 full-őeld displacement measurements, 36 and dynamic energy release during anticrack growth. 37 Crucial inputs are the elastic material properties of snow slab and weak layer.…”

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confidence: 99%

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Fracture toughness of mixed-mode anticracks in highly porous materials

Rosendahl,

Adam,

Bergfeld

et al. 2024

Preprint

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When porous materials are subjected to compressive loads, localized failure chains, commonly termed as anticracks, can occur and cause large-scale structural failure. Similar to tensile and shear cracks, the resistance to anticrack growth is governed by fracture toughness. Yet, nothing is known about the mixed-mode fracture toughness for highly porous materials subjected to shear and compression. We present novel fracture mechanical field experiments tailored for weak layers in a natural snowpack. Using a mechanical model for interpretation, we calculate the fracture toughness for anticrack growth for the full range of mode interactions, from pure shear to pure collapse. The measurements show that fracture toughness values are significantly larger in shear than in collapse, and suggest a power-law interaction between the anticrack propagation modes. Our results reveal new insights into the fracture characteristics of anticracks in highly porous materials and provide important benchmarks for computational modeling.

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Section: Weak-layer Anticracks Are Controlled By Fracture Toughnessmentioning

confidence: 93%

“…1c), conőrming recent theoretical considerations of the differences in shear loading of upslope and downslope cuts. 35…”

Section: Cut Lengths Increase With Slope Anglementioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Fracture toughness of mixed-mode anticracks in highly porous materials

Rosendahl,

Adam,

Bergfeld

et al. 2024

Preprint

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“…Here, we followed the same approach but used a more recent model which accounts for slab layering and bendingextension coupling through the weak layer (Weißgraeber and Rosendahl, 2022). Applying the concepts of mechanics of layered composites (Jones, 1999), the constitutive equations of a deforming beam are given by…”

Section: Elastic Modulus and Specific Fracture Energymentioning

confidence: 99%

Temporal evolution of crack propagation characteristics in a weak snowpack layer: conditions of crack arrest and sustained propagation

Bergfeld

Herwijnen

Bobillier

et al. 2023

Nat. Hazards Earth Syst. Sci.

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Abstract. For a slab avalanche to release, we need sustained crack propagation in a weak snow layer beneath a cohesive snow slab – a process we call dynamic crack propagation. Field measurements on crack propagation are very scarce. We therefore performed a series of crack propagation experiments, up to 9 m long, over a period of 10 weeks and analysed these using digital image correlation techniques. We derived the elastic modulus of the slab (0.5 to 50 MPa), the elastic modulus of the weak layer (50 kPa to 1 MPa) and the specific fracture energy of the weak layer (0.1 to 1.5 J m−2) with a homogeneous and a layered-slab model. During crack propagation, we measured crack speed, touchdown distance, and the energy dissipation due to compaction and dynamic fracture (5 mJ m−2 to 0.43 J m−2). Crack speeds were highest for experiments resulting in full propagation, and crack arrest lengths were always shorter than touchdown lengths. Based on these findings, an index for self-sustained crack propagation is proposed. Our data set provides unique insight and valuable data to validate models.

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The effect of propagation saw test geometries on critical cut length

Bergfeld,

Birkeland,

Adam

et al. 2024

Preprint

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Abstract. For a slab avalanche to release, a crack in a weak snow layer beneath a cohesive snow slab has to initiate and propagate. Information on crack propagation is essential for assessing avalanche triggering potential. In the field, this information can be gathered with the Propagation Saw Test (PST), a field test that provides valuable data on crack propagation propensity. The first PSTs were performed about 20 years ago and standards have since been established. However, there are still differences in how the PST is performed. Standards in North America require the column ends to be cut vertically, whereas in Europe they are typically cut at a normal angle. In this study, we investigate the effect of these different column geometries on the critical cut length. To this end, we conducted 27 pairs of PST experiments, each pair consisting of one PST with slope normal cut ends and one PST with vertical cut ends. Our experiments showed that PSTs with normal cut ends have up to 50 % shorter critical cut lengths, and the difference predominantly depends on the slope angle and slab thickness. We developed two load-based models to convert critical cut lengths between the test geometries: (i) a uniform slab model that treats the slab as one uniform layer and (ii) a layered model that accounts for stratification. For validation, we compare these models with a modern fracture mechanical model. For the rather uniform slabs of our experiments, both load-based models were in excellent agreement with measured data. For slabs with an artificial layering, the uniform load-model predictions reveal deviations from the fracture mechanical model whereas the layered model was still in excellent agreement. This study reveals the influence that the geometry of field tests and the slope angle of the field site have on test results. It also shows that only accurately prepared field tests can be reliable and therefore meaningful. However, we provide models to correct for imprecise field test geometry effects on the critical cut length.

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A closed-form model for layered snow slabs

Cited by 4 publications

References 46 publications

Fracture toughness of mixed-mode anticracks in highly porous materials

Fracture toughness of mixed-mode anticracks in highly porous materials

Temporal evolution of crack propagation characteristics in a weak snowpack layer: conditions of crack arrest and sustained propagation

The effect of propagation saw test geometries on critical cut length

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