Preprints
https://doi.org/10.5194/nhess-2022-161
https://doi.org/10.5194/nhess-2022-161
 
20 Jun 2022
20 Jun 2022
Status: a revised version of this preprint is currently under review for the journal NHESS.

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

Bastian Bergfeld1, Alec van Herwijnen1, Grégoire Bobillier1, Philipp L. Rosendahl2, Philipp Weißgraeber3, Valentin Adam2,1, Jürg Dual4, and Jürg Schweizer1 Bastian Bergfeld et al.
  • 1WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland
  • 2Institute of Structural Mechanics and Design, Technical University of Darmstadt, Darmstadt, Germany
  • 3Chair of Lightweight Design, University of Rostock, Germany
  • 4Institute for Mechanical Systems, ETH Zürich, Zürich, Switzerland

Abstract. For a slab avalanche to release, the system, consisting of a weak layer below a cohesive slab, must facilitate crack propagation over large distances – a process we call dynamic crack propagation. Field measurements on crack propagation at this scale are very scarce. We therefore performed a series of propagation saw test experiments, up to ten meters long, over a period of 10 weeks and analyzed 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 PSTs 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.

Bastian Bergfeld et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2022-161', Anonymous Referee #1, 13 Jul 2022
    • AC1: 'Reply on RC1', Bastian Bergfeld, 17 Nov 2022
  • RC2: 'Comment on nhess-2022-161', Edward Bair, 19 Jul 2022
    • AC2: 'Reply on RC2', Bastian Bergfeld, 17 Nov 2022

Bastian Bergfeld et al.

Bastian Bergfeld et al.

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Short summary
For a slab avalanche to release, the snowpack must facilitate crack propagation over large distances. Field measurements on crack propagation at this scale are very scarce. We performed a series experiments, up to ten meters long, over a period of 10 weeks. Beside the temporal evolution of the mechanical properties of the snowpack, measured crack speeds were highest for PSTs resulting in full propagation. Based on these findings, an index for self-sustained crack propagation is proposed.
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