Étude expérimentale des émissions acoustiques générées par les écoulements granulaires

Landslides are potentially deadly and destructive events. However, their trigger mechanism and propagation still remain poorly understood. This is partly due to the lack of observations. To increase the number of observations, it is possible to exploit the seismic waves generated during their progression. Indeed, a single station can cover continuously a large area. However, how to link the acoustic emissions to the events dynamics? To answer this question, three laboratory experiments of increasing complexity have been performed: 1) single bead impacts on smooth, rough and erodible surfaces, 2) quasi steady and uniform flows and 3) calotte collapses. In all cases, the elastic energy radiated acoustically has been correlated to the physical and/or dynamical properties of the event. For example, the first experiment confirms that the radiated elastic energy during an impact on smooth surface is well described by the Hertz contact. When the surface is more complex (rough and erodible), the differences with the theory are quantified. The second experiment highlight the link between the radiated elastic energy per time unit depends on the velocity fluctuations of the beads constituting the flow. In the third experiment, correlations between the radiated elastic power, the potential energy lost by time unit and the total kinetic energy of the beads constituting the flow are exhibited (the missing time in kinetic energy is in all probability the number of impacts between beads per time unit).