Numerical Simulation Study on the Stability of Mined−out Areas and Ore Pillar in a Metal Mine

The stability of mined−out areas and pillars is critical to the safety of mining. To investigate the stability of the mined−out area and the pillar of a metal mine with room−and−pillar mining method, this paper establishes a part of the mined−out area refined three−dimensional model and a numerical model of the stress evolution characteristics of the mined−out area and the pillar through the combination of field survey and numerical simulation. The results show that the mined−out areas are mostly horizontal and gently inclined, and the morphology of the mined−out areas and pillars in the mid−plot is in good agreement with the reality. There are effects of ore body excavation on the surrounding rock, the stability of the roof in the goaf, and the stress evolution in the pillars. The stability of the mined−out area and the pillars is affected by the morphology of the mined−out area, the width of the pillar distribution, and the number of pillars. Overall, the overall stability of the mined−out area is higher in Area I than in Area II. There is a maximum stress concentration area in the upper mined−out area of Area II, which may produce local cracks, but the area has been closed and treated without affecting the overall stability. This study can provide the theoretical basis for the evaluation of stability of mine mined−out areas and pillars, and disaster prevention and control of mine mined−out areas.