Evaluating Open-Pit Slope Stability Through Successive Modeling Stages

Abstract

Slope stability in open-pit mining is a critical factor influencing operational safety, production continuity, and overall economic performance. Conventional assessments typically employ two-dimensional limit equilibrium methods, which do not adequately represent the inherently three-dimensional nature of slope behavior. Even three-dimensional analyses may remain insufficient when geological conditions are oversimplified or model inputs are limited. In this study, open-pit slope stability was assessed using the three-dimensional limit equilibrium approach implemented in PLAXIS 3D LE. A simplified geological model was first created based on commonly accepted rock mass parameters from the literature, excluding groundwater, structural features, and dynamic loads. The analysis was then refined through a stepwise modeling strategy that sequentially incorporated site-specific geological units, rock mass properties derived from field and laboratory studies, identified fault zones, groundwater conditions, and pseudo-static seismic loading. Safety factors were calculated and compared using Bishop, Janbu, Generalized Limit Equilibrium, and Spencer methods. The results demonstrate a consistent reduction in safety factors as more realistic geological, hydrogeological, and structural conditions are integrated into the model. These findings emphasize the limitations of simplified analysis approaches commonly used in industry and highlight the importance of comprehensive geotechnical characterization for achieving reliable and realistic slope stability evaluations.