SHEAR FRACTURE PRECIPITATED BY STRAIN SOFTENING AS A MECHANISM OF DRY SLAB AVALANCHE RELEASE

Snow stratigraphy studies at the fracture lines of dry slab avalanches often indicate a situation that consists of a harder thick layer overlying a thin weak layer. Prefracture stress conditions and progressive fracture of snow slabs are discussed here from the point of view that slow shear failure in the weak layer results in Griffin-like critical lengths there, resulting in rapid shear fracture and subsequent avalanche release. The main experimental facts on snow and field observations of snow slab avalanche are explainable from this approach. -from Author