The Controlling Role of Geological Structures in Rock Slope Failure Mechanisms in Fold-and-Thrust Belts: An Example from the Ergetu Open-Pit Coal Mine, China

Abstract Slope instability is one of the most significant safety hazards in open-pit mining production. Since May 2023, obvious signs of deformation and damage have been observed on the western pit slope of the Ergetu Open-Pit Coal Mine in Ordos City, Inner Mongolia, China. This study comprehensively employed geological structure exploration and numerical simulation methods to elucidate the deformation evolution process of the western pit slope of the Ergetu Open-Pit Coal Mine and aims to reveal the sliding control mechanisms of the geological structures. By combining a field investigation with unmanned aerial vehicle (UAV) photogrammetry techniques, interpretation work was conducted on the surface exposure of the geological structures in the study area. The sample window method was subsequently used to understand the development of the rock mass structural planes within the slope, and the physical and mechanical parameters of the slope rock mass were determined based on the geological strength index (GSI) and rock mass classification system. In addition, the integration of drilling and geophysical techniques formed a comprehensive technical framework for detecting the internal structure of the slope rock mass, revealing that the stability of the western pit slope of the Ergetu Open-Pit Coal Mine is controlled by the structure of the locked segment against the background of the fold-and-thrust belts. Finally, a structural model of the slope rock mass was constructed based on discrete fracture network (DFN) technology. The initiation–instability processes of the western pit slope were simulated using the discrete element software 3DEC, which showed the controlling role of geological structures in the initiation and movement process of rock slope failure. The comprehensive detection technology framework and controlling sliding mechanism of the geological structure proposed in this study can provide a reference for the prevention and control of similar locked-segment landslides.