Abstract:The southern slope of Chengmenshan Copper mine is a typical tilted sedimentary stratum, which is susceptible to overall instability during the process of mining due to adverse factors such as heavy rainfall and blasting, threatening the safe development of normal mining activities in the quarry. Using engineering analogy method, theoretical analysis method and numerical simulation method, a three-dimensional model is established to evaluate the stability and formulate the optimal treatment plan of the slope. The results showed that the geotechnical body of the southern slope had a high degree of weathering, the lower part of the developed F1 fault is parallel to the slope direction with an opposite tendency, and the geotechnical body is cut by the structural surface with low overall strength, which is the main reason for the instability of the slope. Through the analysis and calculation of Midas/GTS numerical software, the damage to the southern slope is mainly wedge-shaped body and circular arc damage and is in the basic stable state. According to the implementation conditions of the site, three treatment solutions were proposed. The analysis of the results concluded that solution 2 (upper slope cutting and load reduction, lower stacking and counter-pressure, forming 5 steps) could not only reduce the engineering cost, balance the amount of excavation and filling, but also reserve the transportation and maintenance channels for the subsequent production, and minimize the encroachment of -82 m platform, which is beneficial to the long-term stability of the slope.