Measurement of crack‐face friction in collapsed weak snow layers - van Herwijnen - 2009

The results indicate that crack-face friction in collapsed weak layers is far from negligible

A. van Herwijnen; J. Heierli; G. Casassa; H. Narita; N. Maeno; B. M. Chiaia; P. Cornetti; B. Frigo; J. Crocker; D. Grier; R. C. Fletcher; D. D. Pollard; D. Gauthier; B. Jamieson; P. Gumbsch; M. Zaiser; J. Jamieson; C. Johnston; B. Johnson; B. C. Johnson; J. B. Jamieson; R. R. Stewart; H. O. Kirchner; G. Michot; J. Schweizer; F. Louchet; J. Faillettaz; D. Daudon; N. Bédouin; E. Collet; J. Lhuissier; A.-M. Portal; D. M. McClung; M. Schneebeli; C. Fierz; P. M. B. Föhn; J. Bruce Jamieson

2009

Scholarcy highlights

  • In this letter we analyze the frictional contact forces during and immediately after the collapse of a weak snowpack layer, when the sliding plane consists of the freshly collapsed and crushed, but not yet eroded granular debris of the weak layer
  • Field measurements were carried out in order to determine the amount of friction of a freshly debonded slab on a bed of weak layer debris, during and immediately after the collapse of the weak layer
  • The results indicate that crack-face friction in collapsed weak layers is far from negligible
  • The friction data presented in this letter showed no dependance on grain type of the weak layer
  • It is still possible that friction depends on snow stratigraphy, in particular on the grain type and hardness of the weak layer as well as the layer above and below it
  • An important implication of our findings is that the minimum angle for avalanche release does not depend on shear strength, as is often thought, but results from crack-face friction which comes into play only as the fracture through the weak layer is already propagating

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