Numerical analysis on the influence of frictional strength of fault plane on working face mining

Frictional strength of fault plane is the basis for estimating fault slip risk induced by stress disturbance during coal mining. Based on Chengzhuang coal mine field in Jincheng, constraint mechanism of frictional strength of fault plane to in-situ stress is analyzed, in addition, the effect law of F13 fault and its frictional strength on seam roof stability, lead abutment pressure and fault slip risk are also studied through both theoretical analysis and numerical simulation calculation. The results show that ratio of maximum to minimum principal stress in deep crust is constrained by frictional strength of fault plane, fault will slip when the ratio reaches the frictional strength extremum of fault plane located in critical direction. Fault fracture zone results in disturbance in initial stress field, forming low stress zone and high stress concentration zone around fault, which will have a immediate impact on movement, deformation and abutment pressure distribution of seam roof. Seam roof subsidence and alternate displacement of two fault walls are larger when frictional strength is smaller, it is obviously that lead abutment pressure decreases when working face advances near the fault. Ratio of the tangential stress to normal stress easily reaches frictional coefficient of fault plane, which will lead to higher fault slip risk.