Simulation and analysis of fracture evolution in repeated unloading mining based on fault structure

In the process of coal seam mining, the fault structure can easily lead to the concentration of ground stress, which seriously threatens the safety and efficiency of mining. In order to study the influence of repeated mining on the subsidence law, fracture characteristics and stress distribution of overlying strata under the condition of reverse fault, this paper adopts the method of similar simulation and numerical simulation to analyze the subsidence, fracture and stress variation law of overlying strata, and optimize the gas extraction effect in the goaf. The results show that the more downward mining, the more obvious the collapse and compaction of overlying strata of coal seam; the sinking amount of the reverse fault shows “M” distribution in the displacement change of various heights under the influence of fault mining, and the sinking amount shows “n” distribution in the mining of faultless coal seam; The stress of coal seam overburden presents a small-large-small distribution state; in the overburden rock subsidence law, the maximum subsidence range of the reverse fault is concentrated in the central Goaf; in the stress evolution law of reverse fault mining, the stress transfer phenomenon of weak structure body of coal rock mass cracking appears; the effect of gas extraction in goaf is optimized, and it is concluded that negative pressure extraction is adopted in goaf, and the negative pressure of orifice extraction is 7.6 KPa; the amount of gas extraction from high-level boreholes accounts for 30.2% ~ 55.4% of the total gas emission. The research results can provide a reliable basis for future mining under fault structures.