Influence of bed curvature on the numerical modelling of unconstrained granular materials

This paper deals with the theoretical-numerical and experimental treatment of dry rock avalanches moving down a chute. Depth-averaged field equations of balance of mass and momentum as prescribed by Savage and Hutter (1991) are implemented in the RASH3D code. They describe the temporal evolution of the depth averaged velocity and the distributi0n of the avalanche depth. A Coulomb-type behavior of the mass is assumed. To incorporate the curvature effects of the bed, the centripetal acceleration term has been here implemented in the code. Carried out experiments consist in the release of granular material on an inclined plane that is connected to a horizontal run-out zone through a sharp transition. Comparison of the experimental findings with the computational results proved that dropping the centripetal acceleration term can have the effect of leading to unverifiable error in the determination of the well fitted friction angle because the tuned parameter obtained for fitting a runout distance may be dependent on these local effects. In particular, an overestimation of the computed dynamic friction angle respect to its measured value is observed.