Abstract: A copper-cobalt mine in Congo (DRC) is a gently inclined medium-thick ore body. A 10 m-thick low-grade cobalt ore interlayer is developed in the middle of the ore body. The ore body is divid⁃ ed into a 7 m-thick hanging wall ore and a 13 m-thick footwall ore. The large-scale approach and the dia⁃ mond-shaped medium-deep hole hanging wall and footwall mining method are used for mining. In order to ensure the stability of the surrounding rock of the stope and improve the mining conditions, the structural parameters of the stope need to be optimized. Taking the first mining area of the mine as the engineering background, the maximum safe span of the ore body is calculated to be 19.12 m based on the elastic sim⁃ ply supported beam theory, and four sets of matching span schemes are set accordingly. FLAC3D is used to carry out numerical simulation, and the evolution characteristics of surrounding rock stress, roof displace⁃ ment and plastic zone under different stope sizes are analyzed. Combined with the entropy -TOPSIS fuzzy comprehensive evaluation model, the multi-index scheme optimization is completed. The results show that with the increase of the width of the stope, the main stress of the two sides increases nonlinearly, and the main stress of the roof decreases gradually. When the span reaches 20 m, the tensile stress of the roof ap⁃ pears and the plastic zone expands obviously. The comprehensive evaluation determines that the optimal parameters are the footwall stope span of 18 m and the hanging wall stope width of 9 m. The scheme has good controllability of surrounding rock and is suitable for the upper and lower plate mining process, which can provide reference for the optimization of stope parameters of similar gently inclined metal mines with interlayer.

Key words: upper and lower plate mining separately, stope structure parameters, numerical simulation, entropy-TOPSIS, fuzzy optimization