Modeling of crack propagation in weak snowpack layers using the discrete element method

• Published in: The Cryosphere
• Main Authors: Gaume, J., Van Herwijnen, A., Chambon, Guillaume, Birkeland, K., Schweizer, J.
• Other Authors: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Erosion torrentielle neige et avalanches (UR ETGR (ETNA)), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), USDA, Forest Service National Avalanche Center
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: NUMERICAL MODEL; DISCRET ELEMENT METHOD; AVALANCHE DE NEIGE SECHE; STRATE DE NEIGE; METHODE DES ELEMENTS DISCRETS; MODELE NUMERIQUE; MECANISME DE DECLENCHEMENT; RUPTURE D'EQUILIBRE; [SDE]Environmental Sciences; The Cryosphere
• Online Access: https://hal.archives-ouvertes.fr/hal-01273404; https://hal.archives-ouvertes.fr/hal-01273404/document; https://hal.archives-ouvertes.fr/hal-01273404/file/gr2015-pub00045557.pdf; https://doi.org/10.5194/tc-9-1915-2015

International audience Dry-snow slab avalanches are generally caused by a sequence of fracture processes including (1) failure initiation in a weak snow layer underlying a cohesive slab, (2) crack propagation within the weak layer and (3) tensile fracture through the slab which leads to its detachment. During the past decades, theoretical and experimental work has gradually led to a better understanding of the fracture process in snow involving the collapse of the structure in the weak layer during fracture. This now allows us to better model failure initiation and the onset of crack propagation, i.e., to estimate the critical length required for crack propagation. On the other hand, our understanding of dynamic crack propagation and fracture arrest propensity is still very limited. To shed more light on this issue, we performed numerical propagation saw test (PST) experiments applying the discrete element (DE) method and compared the numerical results with field measurements based on particle tracking. The goal is to investigate the influence of weak layer failure and the mechanical properties of the slab on crack propagation and fracture arrest propensity. Crack propagation speeds and distances before fracture arrest were derived from the DE simulations for different snowpack configurations and mechanical properties. Then, in order to compare the numerical and experimental results, the slab mechanical properties (Young's modulus and strength) which are not measured in the field were derived from density. The simulations nicely reproduced the process of crack propagation observed in field PSTs. Finally, the mechanical processes at play were analyzed in depth which led to suggestions for minimum column length in field PSTs.