BACK-ANALYSIS OF THE COLLAPSE OF TACONNAZ REINFORCED CONCRETE DEFLECTIVE WALLS BY FEBRUARY 11th 1999 AVALANCHE

ABSTRACT: This paper shows that a precise mechanical analysis of destructive events can improve the knowledge of the avalanche action against structures in real situation. In fact, measuring avalanche’s impact on site is not common. In that way, the destruction of two deflective walls in Taconnaz site by February 11th 1999 exceptional avalanche was a favourable situation to undertake such a study. It consisted in two main parts: firstly, a large on site investigation program was conducted to complete observations and to analyse failure mechanism, including material specimen tests. Then, numerical simulations were performed with a rigorous three-dimensional finite elements model using a realistic representation of the concrete behaviour, in both quasi-static and dynamic approaches. Finally, two different scenarios are exhibited and confirmed: one of the walls was effectively destroyed under bending mode due mainly to a distributed pressure generated by the flow whereas the second was directly influenced by a localized impact