Study on law of fault activation,failure and energy release under influence of mining

In order to study the mechanism of fault activation and disaster when the working face was mined near fault，the stress field and displacement field of the fault layer were analyzed,based on theoretical analysis and numerical simulation,the trend of fault activation and destabilization area was discussed. At the same time，the fault activation release energy and the residual energy transferred to the working face were calculated. The results show that the fault activation is divided into four stages：initial activation stage,stable activation stage,activation intensification stage,and activation weakening stage. The fault activation position develops from the fault at the high roof to the vicinity of the coal seam,and the activation time of the fault at the floor is later than that of the fault at the roof. Under the influence of mining,the shear stress of the fault surface drops abruptly and leads to energy release. The shear stress and the ratio (shear stress to normal stress) on the fault surface exhibits a trend of stabilitygrowthdecrease,but the latter of them always lags behind the former. Using the calculation formula of the energy released by the activation and instability of the fault,the magnitude of the fault activation energy released as mining approaches the fault is calculated using the fault activation release energy formula. The calculation results are similar to the microseismic monitoring records，which proves the feasibility of the calculation method. The energy released by the activation of the fault is transferred to the working face in the form of a negative index. The energy released in the initial activation,stable activation,and activation weakening stages of the fault is transferred to the working face. During the activation intensification stage,the fault activation energy received by the working face is greater than 107 J，and the fault activation energy received by the working face at other stages is less than 105 J. Therefore,when the distance between the working face and the fault is less than 40 m,it is greatly affected by the disturbance of fault activation,and the impact risk is higher.