Fracture energy applicable to dry snow slab avalanche release

Abstract

Dry slab avalanches release by a sequence of propagating fractures: first by shear fracture (mode II and mode III) in a weak layer at the base of the slab and second by tensile fracture through the crown after which release of the slab is imminent. The fracture energy is the energy which must be provided to produce a unit area of fracture surface. It is a key parameter in determining how and when fractures will propagate and important slab characteristics such as length and width that are necessary in order to estimate slab mass and volume in relation to destructive potential. In this paper, approximate estimates of fracture energy are calculated from field measurements of slab properties, laboratory measurements and in‐situ strength tests in alpine snow. Estimates of fracture energy are given for both tensile fracture (mode I) through the crown as well as for shear fracture (mode II) in fragile weak layers of slab avalanches. The results, when compared with other values from ice, rock and engineering materials, suggest that snow has the lowest values.