Observations of grain-scale interactions and simulation of dry granular flows in a large-scale flume

A series of 30 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 “dynamic analysis” 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.