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Slope instabilities may be generated on open slopes or within canyons due to external mechanisms such as seismic acceleration, sediment overload or excess pore pressures. These instabilities can suddenly release great amounts of material and originate gravity driven slides or flows of different sorts. The way these sediment masses accelerate and move after a slope failure impacts differently the water column (tsunamogenesis) and the deposition geometry and architecture down slope. Some slides do not display enough energy to flow and may stop suddenly as they have been started. Other slides are drastically transformed while they accelerate and become gravity driven flows characterized by turbulence, mixing and sediment segregation. The aim of this work is to connect, in a modelling frame, the initial condition given by a 3D slope instability analysis (Samu 3D ; Sultan et al., 2007), providing the failure initiation, and the post-failure evolution till the final (de)position of the released material and its geometry. The depth integrated flow is simulated by a Smoothed Particle Hydrodynamics (SPH) deterministic model that solves in a Lagrangian approach the horizontal momentum equation and the sediment concentration transport for each class of grain sizes. The model accounts for non hydrostatic pressures, complex rheology, turbulence, entrainment of ambient water, particles settling, erosion and deposition. Being constitutively Lagrangian this approach provides a meshless solution. Hence, the computational effort is concentrated on the flow location and avoids computation elsewhere in the domain of interest. The model is applied to the Nice airport slope where well documented slide occurred in 1979. The 1979 event is used to constrain the model and provide confidence to simulate a flow originated from an area detached as potentially prone to failure thanks to in situ geotechnical measurements and 3D slope stability modelling (Leynaud et al., this conference). For each simulation the model provides flow velocities and acceleration and segregated deposition of the sediments.
Sultan, N., M. Gaudin, S. Berne, M. Canals, R. Urgeles, and S. Lafuerza (2007), Analysis of slope failures in submarine canyon heads: An example from the Gulf of Lions, J. Geophys. Res., 112, F01009, doi:10.1029/2005JF000408.
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