A series of thirty tests on dry granular flows were performed using a large scale flume under varying source volumes and basal friction conditions to capture grain scale interactions and their impact on overall runout behaviour. These grain interactions and ultimately the flow regimes developed were found to be a function of material source volume and boundary roughness. The dimensionless inertial number was computed for each flow, but was found to be of limited utility except perhaps to define a general state (e.g. liquid regime) for the material due to the high slip velocity encountered in the granular flows. Using the depth averaged numerical model, DAN, it was found that a single set of semi-empirically derived frictional parameters (i.e. specific to internal and basal friction conditions) was appropriate for matching the overall mobility of the experimental flows over a range of flow volumes and slope inclinations.However, these angles were found to be lower than those determined from laboratory interface friction tests, highlighting the importance of collisional stress transfer in the basal zone of the dry flowing landslides.
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 708 and 458 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.
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