Instability mechanisms of slope in open-pit coal mines: From physical and numerical modeling

The stability of open-pit mine slopes is crucial for safe and efficient mining operations. However, the presence of weak interlayers poses significant challenges in maintaining the stability of slopes. To explore the impact of the rock arching effect on slopes during excavation, understand the deformation zones and evaluation stages in such environments, and analyze the formation and characteristics of cracks, this study investigated the instability mechanism of open-pit mine slopes with weak interlayers through physical and numerical modeling. Focusing on the Zaharnur open-pit coal mine in China as a prototype, a sophisticated physical model test employing particle image velocimetry and Brillouin optical frequency domain analysis was conducted to comprehensively analyze the displacement and strain variation characteristics of open-pit mine slopes. The displacement, strain, stress redistribution, and failure processes of slopes under excavation were comprehensively analyzed through physical and numerical modeling. The results showed that the slope model exhibited a strain pattern in which the strain incrementally increased from its center toward the edges, and the landslide thrust was converted into an internal force along the arch axis and transmitted to the supports. The concept of the rock arching effect specific to soft rocks was proposed, shedding new light on an important phenomenon specific to open-pit slopes with weak interlayers. Based on its deformation characteristics, the slope could be divided into three areas: The excavation influence area, the crack area and the failure area. In addition, the ratios of the height and width of the outermost cracks to the excavation width fluctuated in the ranges of 0.36–0.49 and 0.72–1.00, respectively. These findings contribute to a better understanding of the instability mechanisms in open-pit mine slopes with weak interlayers and provide valuable guidelines for safe mining practices.