Study on the Influence of Coal Face Advancing Distance on Fault-Activated Water Inrush

Water inrush in deep coal mines is closely related to geological structures such as faults. In order to study the influence rule of different coal face advancing distance (CFAD) on floor fault activation and floor rock mass failure characteristics, a mechanical model of fault activation was established with the 1315 working face of Anju coal mine as the research background, and the distribution of shear stress on fault plane and the influence rules of fault-activation under different CFAD are obtained. Then, FLAC3D numerical simulation software was used to further simulate and study the activation rules of floor faults and the characteristics of fracture development in floor rock mass. The results show the following: (1) When the coal face advances to a position of 80 m from the fault, the shear stress on the fault plane is sufficient to cause the fault-activation; When the coal face advances to a position of 20 m from the fault, the shear stress reaches a maximum and the fault-activation will reach a peak; (2) In the fault zone, fractures are derived from the bottom up under mining operation, but the development degree of fractures in the deep part is weaker than that in the shallow part. (3) Due to the existence of faults, a “oblate” damage and failure zone extending to the front and bottom of the coal wall gradually forms in the working face floor. The extension of this damage zone is first connected with the activated fault crack, and has formed advanced water inrush.