Numerical modelling of geophysical mass flows such as debris flows, rock avalanches or snow avalanches is generally based on hydraulic depth-averaged approaches using a shallow-flow approximation. Such models are increasingly used in an operational context to assess hazards and risks, to design protective measures and to anticipate future evolutions in the context of climate change. However, these numerical tools still face a number of challenges that can limit their applicability. In particular, shortcomings related to the complex rheological behavior of the materials, to the heterogeneity of the flows, to the role of erosion and entrainment processes, etc. can be mentioned. I will illustrate some of these issues and how they can affect the predictive capabilities of the models. I will then present a few case studies designed to gain insights into the dynamics of gravity-driven surges through small-scale experiments, focusing on the particular case of a viscoplastic rheology. A first project was concerned with the internal dynamics of viscoplastic surges and the evolution of unyielded regions in the tip region using a specific laboratory setup. The experimental results were used to test and improve the asymptotic expansions underlying the shallow-flow models. The second project was to investigate the interaction between a surge and a mobile bed using SPH numerical experiments. The simulations revealed a wide variety of entrainment regimes that can lead to either a decrease or an increase in the mobility of the flow.
Accès Salle des séminaires FAST-LPTMS (Bât. 530, salle C.120, 1er)