Experiments on granular flow behavior and deposit characteristics: implications for rock avalanche kinematics

Experimental dry granular flow with a flume configuration is a basic model used for simulating rock avalanches. Despite the establishment of many empirical relationships between single parameters and runout behavior, very limited attention has been focused on the corresponding mechanisms. To address this issue, the granular flow behavior and associated deposit characteristics are researched herein via a series of flume tests with varying grain size and volume conditions. The results show that the flow behavior is correlated with the grain size and volume of the granular flow. With decreasing grain size and increasing volume, a transition of the internal shear behavior from uniformly distributed shear-to-shear localization at the bottom is found, which is claimed to affect the global shear behavior. The global shear behavior, which is characterized by the global shear rate, is found to be correlated with the granular flow mobility. The reduction in the global shear rate related to the grain size decreases the equivalent friction angle, thus increasing the flow mobility. On the other hand, the Savage number correlates positively with grain size, indicating a transformation from a dense regime to an inertial regime with increasing grain size. This transformation results in discontinuous deformations in deposits, such as the attenuation of flow-like morphologies and increases in particle mixing.