Experimental Investigation and Numerical Simulation on the Strength and Deformation Characteristics of Granular Materials at Various Elevations of Dump Slope

Determining the shear strength parameters of granular materials in high waste rock dump slopes is essential for reliable slope stability analysis. In this study, dump materials were sampled from six benches (elevations 2800–2950 m) of an open-pit mine dump slope, and in situ density tests, gradation analyses, and large-scale consolidated drained (CD) triaxial tests were performed. Two PFC2D slope models—one with uniform (spatially averaged) parameters and one with elevation-dependent (layered) parameters—were then established to quantify how spatial heterogeneity affects stability predictions. The results show pronounced vertical heterogeneity: density, porosity, gradation, and shear strength parameters vary systematically among benches, reflecting the combined effects of compaction history and particle segregation during dumping. All specimens exhibited strain hardening and continuous shear contraction, and specimens with a denser, better-graded structure showed higher strength and lower compressibility. The layered model yields a higher factor of safety and shallower, bench-scale slip surfaces, whereas the uniform model underestimates stability and misplaces the critical slip zones. These findings demonstrate that elevation-dependent parameter assignment better represents the heterogeneous failure mechanism of high dump slopes and should be preferred over uniform parameterization in stability analyses of similar waste rock dumps.