Physical and numerical modelling of dry granular flows under Coriolis conditions

Abstract

In this paper, quantitative observations of dry granular flows subject to varying magnitude and direction of Coriolis acceleration are presented in order to assess the robustness of the Savage–Hutter shallow water approximation of granular flow for modelling landslides. Nine tests carried out at 70° and 45° slope inclinations are described for cases where no Coriolis acceleration was applied (i.e. tests performed at 1g), and where the Coriolis acceleration acted into or out of the slope (centrifuge tests). Given that the magnitude of the Coriolis term is velocity dependent, each point within a model landslide on the centrifuge experienced a unique time and space-varying magnitude of Coriolis acceleration, altering the flow displacement with time and final deposit characteristics. The resultant behaviour is compared to a depth-averaged flow model based on a frictional rheology. A single set of model parameters was found to be appropriate for all test conditions and directions/magnitudes of Coriolis acceleration, illustrating the robustness of the frictional depth-averaged approach to capture the mobility of dry granular flows, albeit as a ‘Class C' type of prediction. It is noted that the empirically derived basal interface friction was found to be lower than the static interface friction determined by conventional testing, suggesting that new methods are needed for the a priori determination of suitable rheological parameters for high-speed flows.