Size effect law and fracture mechanics of the triggering of dry snow slab avalanches

Zdeněk P. Bažant, Goangseup Zi, David McClung

Research output: Contribution to journalArticle

70 Citations (Scopus)

Abstract

A size effect law for fracture triggering in dry snow slabs of high enough length-to-thickness ratio is formulated, based on simplified one-dimensional analysis by equivalent linear elastic fracture mechanics. Viscoelastic effects during fracture are neglected. The derived law, which is analogous to Bažant's energetic size effect law developed for concrete and later for sea ice, fiber composites, rocks, and ceramics, is shown to agree with two-dimensional finite element analysis of mode II cohesive crack model with a finite residual shear stress. Fitting the proposed size effect law to fracture data for various slab thicknesses permits identifying the material fracture parameters. The value of preexisting shear stress in a thin weak zone of finite length is shown to have significant effect. There exists a certain critical snow depth, depending on the preexisting stress value, below which the size effect disappears. Practical applications require considering that the material properties (particularly the mode II fracture toughness or fracture energy) at the snow slab base are not constant but depend strongly on the slab thickness. This means that one must distinguish the material size effect from the structural size effect, and the combined size effect law must be obtained by introducing into the structural size effect law dependence of its parameters on snow thickness. The thickness dependence of these parameters can be obtained by matching the combined law to avalanche observations. Matching Perla's field data on 116 avalanches suggests that the mode II fracture toughness is approximately proportional to 1.8 power of snow thickness.

Original languageEnglish
JournalJournal of Geophysical Research B: Solid Earth
Volume108
Issue number2
Publication statusPublished - 2003 Feb 10
Externally publishedYes

Fingerprint

fracture mechanics
size effect
snow
avalanche
Snow
Fracture mechanics
avalanches
slab
slabs
Shear stress
Fracture toughness
fracture toughness
Sea ice
Fracture energy
shear stress
fracture strength
Residual stresses
Materials properties
residual stress
Rocks

Keywords

  • Avalanches
  • Fracture mechanics
  • Scaling
  • Size effect
  • Snow

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Atmospheric Science
  • Geochemistry and Petrology
  • Geophysics
  • Oceanography
  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Size effect law and fracture mechanics of the triggering of dry snow slab avalanches. / Bažant, Zdeněk P.; Zi, Goangseup; McClung, David.

In: Journal of Geophysical Research B: Solid Earth, Vol. 108, No. 2, 10.02.2003.

Research output: Contribution to journalArticle

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