Item: Snow avalanche pressure on obstacles
Title: Snow avalanche pressure on obstacles
Proceedings: Proceedings Whistler 2008 International Snow Science Workshop September 21-27, 2008
Authors: Prof Mohamed Naaim, Dr. Thierry Faug, Dr. Emmanuel Thibert, Dr. Guillaume Chambon, Dr. Nicolas Eckert, Dr. Florence Naaim, Mr. Herv
Abstract: Impact forces by snow avalanches on obstacles need to be taken into account to design hazard maps of avalanche prone areas. An important question is how the forces depend on the velocity and the thickness of the incoming flow. Existing engineering rules recommend to multiply the incident dynamic pressure of the free flow of the avalanche by a constant drag coefficient in order to obtain the effective pressure on the obstacle. But recent field data have shown a strong variation of the drag coefficient according to the flow parameters. This paper addresses the open question of the relation between the effective pressure developed by an avalanche on a given obstacle as a function of the flow parameters and the obstacle shape. The flow of the snow avalanche is considered as a gravity driven free surface flow and a general formulation of the drag coefficient is proposed. This formulation leads to low drag coefficients for rapid flows and higher drag coefficients for low velocity flows. This formulation was successfully tested on existing data including laboratory experiments and recent results from the Lautaret and la Sionne test sites. The new formulation is implemented in a simple avalanche dynamic model and the consequences on the hazard mapping are succinctly analysed.
Presenters: Prof Mohamed Naaim.
Keywords: snow, avalanche, pressure, mapping