To account for cohesion loss and volume reduction in a finite element snow model, Mahajan et al. In addition, existing models based on critical state soil mechanics (CSM) fail in reproducing the post-peak strain-softening behavior of porous cohesive materials since only hardening is allowed in compression. Hence, these methods are suitable for tensile and shear fractures only. In classical continuum methods for fracture 18, 19 as well as in standard materials, the concept of anticrack is physically impossible due to mesh or material inter-penetration induced by volume loss. However, the static and discrete nature of these two models prevents upscaling to the scale of typical avalanche slopes for which a dynamic continuum approach is necessary. 16, 17 proposed the shear-collapse model (SCM) which improved the latter by accounting for dynamics and a more realistic mechanical behavior of the porous weak layer using the discrete element method.
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10 proposed a mixed-mode (I/II) anticrack theory to characterize the conditions for the onset of crack propagation in snow slab avalanches. This contradiction highlighted the crucial role of the cohesion loss and volumetric collapse of the porous structure of the weak layer which is generally accompanied by a so-called “whumpf” sound, indicator of snowpack instability. While such avalanches were for a long time believed to initiate due to mode II shear fracture 13, recent experiments reporting fracture propagation on flat terrain as well as observations of remote avalanche triggering 14, 15 challenged classical theories. Once the initial failure reaches a critical size, the fracture propagates along the slope possibly leading to the detachment and sliding of the overlying slab if the slope-parallel gravitational force overcomes friction 12. Slab avalanches originate due to the mixed-mode failure of a porous weak snow layer buried below a dense and cohesive snow slab 11. Anticrack propagation is also believed to be at the origin of dangerous dry snow slab avalanches 10 that are responsible for most avalanche accidents. This peculiar fracture process is generally referred to as anticrack and is reported in the compression of porous sandstone and sedimentary rocks 3, 4, superheated ice 5, submarine landslides 6, deep earthquakes 7, 8 as well as in brittle foams 9. Our unified model represents a significant step forward as it simulates solid-fluid phase transitions in geomaterials which is of paramount importance to mitigate and forecast gravitational hazards.Ĭohesive porous materials under compression often evidence volumetric collapse leading to localization of compaction or compacting shear bands 1, 2. The key ingredient consists of a modified strain-softening plastic flow rule that captures the complexity of porous materials under mixed-mode loading accounting for the interplay between cohesion loss and volumetric collapse. Here, on the basis of a new elastoplasticity model for porous cohesive materials and a large strain hybrid Eulerian–Lagrangian numerical method, we accurately reproduced the onset and propagation dynamics of anticracks observed in snow fracture experiments.
This is particularly the case for anticracks in porous materials, as reported in sedimentary rocks, deep earthquakes, landslides, and snow avalanches, as material inter-penetration further complicates the problem. Continuum numerical modeling of dynamic crack propagation has been a great challenge over the past decade.
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