Stability evaluation of high-bench dumps considering the effects of disordered particle arrangements

Waste dumps generated during open-pit mining directly affect operational safety, and their hazards increase with dump height. During the stacking of high-bench dumps composed of soil-rock mixtures, particle rolling along the slope commonly produces particle-size grading, yielding gradation patterns that differ markedly from those of conventional dumps. Based on a field case, an improved cellular automaton (CA) was coupled with the finite difference method (FDM) to clarify how spatially disordered particle arrangements influence the distribution of shear-strength parameters in soil-rock mixtures. A slope-stability analysis framework tailored to high-bench dumps was developed, and the effect of particle grading on stability was assessed. Owing to spatial variability in particle distribution, strength parameters exhibited significant scatter even for identical overall gradation; both cohesion and internal friction angle were found to follow normal distributions. Particle grading along the slope was shown to reduce the deformation and volume of the tensile plastic zone, raise the slip-surface position, and increase the factor of safety. These findings advance the understanding of soil-rock mixture mechanics and provide a practical reference for slope stability analysis of complex particulate materials.