Analyzing the stability of surface mine waste dump based on particle size scale distribution

High-steep waste dumps in open-pit mines frequently demonstrate complex particle-size distributions and fractal characteristics along their slopes, which have a significant impact on slope stability. This study takes the Dasuji South waste dump in Inner Mongolia as a case to quantify the fractal dimensions of soil-rock mixtures at various slope heights, and to clarify how these fractal properties govern shear strength and deformation behavior under overlying stress, thereby affecting the overall stability of the waste dump slope. Field sampling and laboratory tests were conducted to determine the particle-size composition and fractal dimensions while direct shear tests were conducted and revealed that lower fractal dimensions indicating coarser particle assemblages significantly enhance shear resistance. Complementary PFC2D discrete element simulations demonstrate that slopes composed of lower-fractal-dimension materials deform less and contain localized deformation zones, whereas higher-fractal-dimension slopes experience more extensive displacement and a heightened risk of landslides. These findings refine our understanding of the relationship between fractal grain-size distribution and slope stability, providing a robust theoretical basis for improved stability assessment and optimized support strategies in deep open-pit mining waste dumps, and ultimately aiding in more effective disaster prevention within geotechnical engineering.