Study on the Effect of Small Faults on the Gas Content in No. 3 Coal Seam of the Changping Mine Field.

To study the influence of small faults on the gas content of Coal Seam 3# in the Changping mine field, the influence scope and degree of small faults on Coal Seam 3# and gas content in the Changping mine field are analyzed based on the field measured data such as the gas content on both sides of the fault, the initial speed of gas emission, and the solidity coefficient of the coal seam, combined with the FLAC3D stress simulation results, and the influence area of small faults is zoned from the perspective of gas control. The analysis results show that the measured gas content in the hanging wall of SF250 fault with a drop of 1.3 m and SF353 fault with a drop of 1.9 m is 7.14 and 9.47 m/t, respectively, and the gas content in the footwall is 5.29 and 7.41 m/t, respectively. The gas content in the hanging wall is obviously higher than that in the footwall; the gas content in the coal seam near the small fault surface is slightly lower. With the increase of the distance from the fault surface, the gas content in the coal seam decreases first and then increases; the firmness coefficients of hanging wall coal of small fault are 0.40 and 0.45, respectively, and those of footwall coal are 0.73 and 0.75, respectively. The firmness coefficient of hanging wall coal seam is obviously smaller than that of footwall coal seam. The closer it is to the fault surface, the smaller the firmness coefficient of coal is, and the greater the initial gas release speed is; the permeability coefficient of the coal seam far from the fault surface in the hangingwall of the small fault shows a decreasing trend after an increasing trend. The maximum stress of the coal seam is 21.85 MPa at 14 m from the hangingwall of the fault to the fault, and the minimum stress of the coal seam is 2.79 MPa at 1 m from the footwall of the fault to the fault. The stress of the hangingwall of the fault is greater than that of the footwall of the fault, and the stress concentration area is 14 m from the hangingwall of the fault to the fault.