Effect Of Faults On The Pore Structure Of Coal And Its Resultant Change On Gas Emission

Faults are one of the important factors influencing coal and gas outburst in outburst coal seams. In this paper, 3# and 8# coal seams in Xinjing Coal Mine were taken as the research objects in the hope of revealing the mechanism of how faults affect coal seam. The pore structure and its resultant change on gas emission of coal samples at different distances from the faults were studied by means of scanning electron microscope, nuclear magnetic resonance and adsorption/desorption experiments. The results show that the fault significantly influences the pore structure. The coal sample closer to the fault has a greater number of well-developed macropores and fractures as well as better connectivity between pores and fractures. Besides, compared with 8# coal seam, 3# coal seam which is more notably impacted by the fault possesses a more developed pore structure at the micron scale. As the distance from the fault increases, the gas adsorption volume declines while the desorption hysteresis coefficient grows on the whole. The coal sample closer to the fault adsorbs a larger volume of gas and meanwhile desorbs gas more easily, so it is more prone to coal and gas outburst. The initial velocity of gas emission falls gradually as the distance from the fault increases. The desorption hysteresis coefficient generally drops with the rise of the initial velocity of gas emission. Judged by the influence scope of the fault, 3# coal seam possesses a much higher outburst risk than 8# coal seam. The research results reveal the mechanism of how faults affect coal pore structure and gas sorption characteristics, which can provide a basis for the prevention and control of gas dynamic disasters in fault-containing coal seams.