Stability analysis of open-pit gold mine slopes and optimization of mining scheme in Inner Mongolia, China

The geological structure of the Changshanhao open-pit mine in Urad Middle Banner, Inner Mongolia, China is extremely complicated, and slope instability has frequently occurred in various forms, such as wedge sliding, bedding sliding, and toppling failure. In order to study the failure mechanisms of these slopes, the geological structure and mechanical rock properties were investigated based on field investigations and laboratory tests. Numerical models for the present mining area and final mining area of the original scheme were established to analyze slope stability. The results showed that the unique geomorphological characteristics of the mining area were generated by geological tectonism, and the north side of the stope is an anti-dip layered rock slope and the south side is a dip layered rock slope. Slope failure is the consequence of endogenic and exogenic integration, including physical and mechanical properties of the rock mass, geological structures such as faults and joints, and human-caused factors such as blasting and excavation disturbances. Then the original excavation scheme was redesigned mainly by optimizing the slope angle and decreasing the final mining depth to maintain slope stability. Finally, the Monte Carlo method was used to analyze the reliability of the slope angle optimization scheme. The open-pit mine excavation plan that meets the stability requirements was obtained eventually.