Excavation-induced open-pit slope failures behaviors from microscopic insights using DEM analysis

Excavation-induced slope failures present critical challenges in open-pit mining engineering yielding various failure morphologies, yet the underlying the mechanisms remain insufficiently understood. This work attempts to investigate slope arching failures induced by progressive excavation by employing a multi-scale approach integrating Discrete Element Method simulations and analytical solutions. The combined findings reveal a dominant role of initial material packing density in governing slope failure morphology: densely-packed slopes develop well-defined stress arching with localized deformation and delayed collapse, whereas relatively-loose slopes exhibit early, global failure with minimal stress reorientation. Furthermore, the microscopic density-dependent stress redistribution and rotation of principal stress trajectories have been quantitatively evaluated in both physical model tests and numerical models. In addition, a novel classification criterion based on incremental displacement ratios is proposed for distinguishing different failure phases, offering a more reliable indicator of failure onset compared to traditional accumulated displacement metrics. The findings provide micro-mechanical insights and interpretation into macroscale slope behavior, thus enhance the current understanding of realistic failures in excavation-affected open-pit slopes.