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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.

Complex topographic features on the surfaces of rock avalanche deposits have been regarded as important indicators for understanding avalanche kinematics and dynamics. Based on a combination of remote sensing data and in-situ observations of surface landforms, including toreva blocks, transverse and longitudinal ridges, ridges separated by conjugate troughs, and hummocks, a giant Holocene rock avalanche on the Tibetan Plateau is recognized. This work aims to understand the kinematics of this event. In planview, the tongue-shaped rock avalanche exhibits a clear sequential distribution of various landforms. The translation zone (II) is characterised by toreva blocks originating from extension. In subzone III-1 of the accumulation zone (III), compression-related transverse ridges are well developed. Longitudinal ridges resulting from lateral velocity differences due to radial spreading are present in the front part of subzone III-1. Farther down, ridges separated by conjugate troughs (generated by a combination of compression and radial spreading) are common in subzone III-2. Subzone III-3 is characterised by abundant scattered hummocks with circular to oval shapes. Based on the distributions of these landforms, this rock avalanche is proposed to have mainly experienced a motion featuring laminar flow with radial spreading in its distal and marginal parts. During transport, three distinct processes appear to have occurred in the avalanche mass from the proximal to the distal zones: extension-dominated sliding in zone II, compression-dominated sliding in subzones III-1 and III-2, and rapid radial spreading in subzone III-3.