BACK-ANALYSIS OF AN AVALANCHE DESTRUCTIVE IMPACT ON BUILDINGS

ABSTRACT: This paper aims to perform a back-analysis of a snow avalanche event occurred in the Italian Alps on December 2008, in order to estimate impact pressure of a dense avalanche on buildings. In the second decade of December, 2008 the Italian Alps underwent extreme meteorological conditions, i.e. large snowfalls coupled with significant wind accumulation effects. Many extreme snow avalanches, seldom or never observed in the past, naturally triggered in that occasion. On December 15th, 2008 a thick and soft snow slab of about 50000 cube meters released from the upper part of a big wall and impacted a series of chalet houses of Les Thoules in the municipality of Valsavarenche, Aosta Valley. The avalanche totally destroyed seven houses and cut-off the infrastructures (roads, power and telephone lines) for many days. The damage effects caused by the avalanche are here investigated and analyzed under a structural framework. Following inverse forensic approaches based on collapse mechanisms and debris arrangement, an estimation of the dynamic pressure and impact direction is performed. A comparison the results of the back-analysis is done and suggestions are proposed