Slab Avalanche Modeling

Abstract

The chapter starts with a review of a few unfounded arguments sometimes used to account for snow slab instability, and often resulting from the application of mechanical laws that are invalid in a granular, brittle, and healable material like snow. Statistical aspects are investigated using a two-threshold cellular automaton, one for basal instability, and the second one for crown crack opening. The results reproduce the power-law size distribution of starting zone sizes mentioned in chapter 4, and validate a “4-step” triggering scheme made of successive initiation and expansion events for both the basal crack and the crown crack. The possible sintering of collapsed weak layers is then analyzed. It is shown to flow as a slurry for shear strain rates less than a predetermined threshold, or to sinter in the opposite case, which provides a “joker” to any successful “4-step” scheme, turning an incipient avalanche into a simple “whumpf”.