Research on the pore structure and gas adsorption/desorption characteristics of tectonic coal in minor fault zone: Implications for coal and gas outbursts

Minor faults, widely prevalent as small-scale tectonism in mining work face, are one of the important factors influencing coal and gas outbursts (CGO). This paper examined the pore structure, gas adsorption and desorption characteristics of coal samples at varying distances from fault and analyzed their interrelationships. The results show that fault has a significant effect on modifying mesopore and macropore, with a lesser effect on micropore. As distance from the fault decreases, there is an increasing trend in the gas's maximum adsorption volume, desorption rate, desorption volume, expansion energy and initial emission speed. Micropore is not the sole factor influencing gas adsorption, coal mineral composition or other factors also affect gas adsorption performance, while mesopore and macropore control gas desorption characteristics. Powdering significantly enhances gas expansion energy, with gas expansion energy in 0.074-0.2 mm being 7.19 times that of 1-3 mm, greatly increasing the risk of CGO. The influence range of the hanging wall is 17.35 m, which is 1.16 times that of the footwall, indicating a notably stronger modification effect of the fault on the hanging wall. The research results reveal the mechanism of how minor fault affects the microphysical structure and macroscopic adsorption and desorption characteristics on outburst coal seams, providing a foundation for the prevention and control of CGO in coal seams containing minor faults.