Physical and numerical modeling of an interacting granular mass and an erodible layer

This contribution tackle the problem of a fast moving granular mass flowing on a steep slope and successively along a horizontal erodible layer. This setting is typi-cal at many sites where rock avalanche can or already occurred. Then the rele-vance of such a condition lays in its frequency under natural conditions, the high energy content and the possible role of the entrapment of erodible material along the path which can strongly control the evolution of the landslide motion. A series of experimental tests has been performed on a simplified slope to analyze the effect of: released mass and volume, slope angle (35-65°) and thickness of erodible layer on the final runout, the geometry of the deposit, the time evolution of the flow and the erosion process. The experiment setup includes a high speed camera and a system for the monitoring of the flow characteristics which allows to catch the flow evolution in space and time. The adopted materials are a uni-form sand for both the released mass and the erodible layer, and an angular grav-el for the released mass only. These tests allow a better understanding of the pro-cesses in terms of major controlling factors on flow height and velocity, and of erosion capabilities and influence on motion. At the same time they provide a re-liable dataset to perform some numerical simulation and especially to validate the prediction performance of the used numerical code, which adopts an Euleri-an-Lagrangian method allowing to not distort the FE mesh guaranteeing accurate calculation results. This code has already been tested on other geometries showing very good capabilites at simulating long runout flows and erosion. Results are compared in terms of modes of propagation, erosion, velocity and depth of flow as well as considering the dynamic evolution of the flow geometry during the propagation as well as the deposition phase.