LAUSR

Abstract Laboratory experiments consisting of releasing dry rigid blocks on an inclined chute have been designed to investigate the mechanisms involved in downslope motions of granular particles. The varied parameters are the slope inclination, volume and arrangement of the initial mass. The rigid blocks are made of mortar, in which one of them is implanted with a permanent magnet inside as a tracker. The permanent magnet is wrapped by a lightweight material and then by a layer of mortar so that the densities and surface friction coefficients of all blocks used in the rock fall are similar. A non-invasive tracking technology is applied to measure the positions of the tracker by recording the static magnetic fields generated. Displacements, as well as the orientations of the tracker, are derived using appropriately developed algorithms with necessary calibrations. Runout distance is measured manually and its relationships with slope inclination, initial volume and arrangement are discussed. The results obtained highlight the influence of the initial volume on runout distance from the analysis of the distributions of tracker's velocity and acceleration. The movement of the block is divided into two phases based on the distributions of translational kinetic energy. The result shows that the movement within the depositional area is more important in terms of its contribution to the longer runout from a larger initial volume. The magnetic tracking system shows great potential in capturing dynamic behaviours of a tracker block within a moving mass. In addition to translational motions, rotational characteristics of a moving particle can be obtained. As highlighted by the experimental results, larger volume tends to inhibit the rotations while producing propulsions to block at the front-most part.