Superquadric discrete element simulation of the influence of particle shape and orientation on granular column collapse

The shape of rock and soil particles is distinct and their orientation may prefer a certain direction, and determining the influence of particle shape and orientation on the characteristics of granular column collapse is of great significance to geological disasters prevention. The collapse process of granular columns is simulated with the superquadric discrete element method, and the influence of particle shape (aspect ratio A and blockiness B) and initial orientation angle θ of long axis on the collapse characteristics of granular column is analyzed, and further the underlying physical mechanism is explored. The results show that, compared with the case A=1 (isotropic), the collapse of particles with larger A (elongated) or smaller A (platy) results in shorter final runout distance and increases the deposit height, but the effect is gradually weakened. The collapse of particles with larger B (more angular) results in shorter runout distance and higher deposit height, and the effect is also getting smaller. The collapse of particles with θ ≈ 0° (near horizontal) is not a whole continuous motion, but in a mode of some particles being squeezed out from the lateral free surface followed by the gradual slide of particles at the upper right corner of the granular column. For short column, the flow regime is slip-dominant, and the collapse of particles with θ ≈ 135° (near the orientation of subsequent accumulation slope) produces the longest final runout distance. For tall column, the early falling effect is obvious, and the collapse of particles with θ ≈ 90° (nearly upright) has the longest final runout distance. The influence of different particle shapes and orientation angles on the characteristics of granular column collapse is closely related to the transformation process of energy and the meso-structure.