Discrete element simulation of collapse characteristics of particle column considering gradation and shape

Particle shape and gradation are the important factors affecting the movement of debris particle flows (such as landslides, debris flows, rock slides, etc.). The random generation method based on the Voronoi tessellation creates polyhedral particles with different aspect ratios and gradations. The potential particle algorithm is introduced to consider the contact effect between particles. The parameters of the contact model of discrete element are determined according to the indoor tests. For the item parameters, numerical experiments are carried out on the collapse characteristics of the particle column considering the gradation and morphology. The research results show that: (1) The normalized stacking height of the particle column decreases with the decrease of the aspect ratio and the median diameter (d₅₀) of the particles, and the normalized run-out distance increases with the decrease. (2) The relative angle of repose under different working conditions during the accumulation process is in the range of 61.49°~64.99°, and the change rule is consistent with the change of the normalized accumulation height. (3) The normalized energy dissipation range under different working conditions is between 27.1%~35.5%, and the rotational kinetic energy only accounts for 8.20%~9.05% of the translational kinetic energy. (4) The normalized kinetic energy has a negative correlation with the particle coordination number, and the particle coordination number reaches the minimum when the normalized kinetic energy reaches its peak. (5) In the process of collapse, the strong chain is generally distributed in the middle and lower areas of the sliding accumulation body, forming the "arch effect" of the transmission of the force chain. The increase in the median particle size (d₅₀) and the slenderness ratio will reduce the number of strong chains, and the paths of contact force transmission will be small and concentrated, thereby restricting the movement of particles during the accumulation process.