The main factor affecting the gas content in a coal seam is the geological structure, and different types of geological structure have different effects on the gas content in a coal seam. To explore the main controlling factors of gas content in coal seam No. 3 in the Changping minefield, and the effect of different geological structures on gas control in a coal seam, this study analyzes the types and quantities of geological structures in the Changping minefield. Further, geological boreholes are used to sample and analyze coal seams near different geological structures and at different burial depths. The results show that the main controlling factor of gas content in a coal seam is the burial depth of the coal seam, and the gas content tends to increase with the increasing depth. A geological structure has an effect on the occurrence of coal seam gas in a local area, and the gas content in the coal seam near a fault is 1.6 times that in the normal areas at the same depth. The gas content in the upper wall of a normal fault is 21.6% higher than that in the lower wall. The syncline and anticline axes are prone to form gas accumulation areas, where the gas content is 30%‐60% higher than the normal level. Gas accumulation is prone to occur around a collapse column, and the gas content there is 2.47 times higher than that in a normal area at the same burial depth. Combining the formation mechanism and structural characteristics of different geological structures, this study analyzes the effect of geological structures on coal seam gas quantitatively and provides a theoretical basis for the prevention and control of gas disasters in the Changping minefield.

Coal and gas outburst and rock burst disasters have obvious dynamic effects in the process of development and occurrence. It is considered as two typical dynamic disasters. In order to study the mechanical effect and characteristics of typical dynamic disasters in underground coal mines, this work analyzed the stress source on coal and surrounding rock, the mechanism of typical dynamic disasters, and the mechanical appearance of dynamic disaster evolvement and occurrence. The results show that there is a significant mechanical effect in typical dynamic disaster evolution and occurrence. The stresses that cause typical dynamic disasters mainly include tectonic stress, the original stress of the coal and rock, and mining-induced stress. Stress is the necessary condition for the occurrence of typical dynamic disasters and plays a leading role in the gestation process of typical dynamic disasters. The stress effect is slow but persistent in a typical dynamic disaster evolution process, and the stress effect is rapid and dramatic in the process of dynamic disaster occurrence. This work puts forward Technical measures to reduce the hazards of typical dynamic disasters combining the stress effects in a typical dynamic disaster evolution process, and the effectiveness of the measures is verified in engineering practice.

In order to study the influence of water injections into a coal body on coalbed methane (CBM) recovery following hydraulic fracturing, experiments have been done in which water is injected into coal samples at adsorbate equilibrium pressures of 0.5 MPa, 0.84 MPa, 1.5 MPa and 2.5 MPa using a high-pressure adsorbate-injecting water-desorption device. The results show that the injected water can replace the adsorbed methane. The replacement ratio and quantity of adsorbed methane gradually increase with increasing quantities of injected water. Under the adsorbate equilibrium pressure of 2.5 MPa, the maximum displacement of the adsorbed methane is 11.88 mL/g when the moisture content of the coal is 10.03%. Under the adsorption equilibrium pressure of 0.84 MPa, the maximum replacement rate of the absorbed methane is 59.14% when the moisture content is 8.39%. The increase of the displacement and replacement rates shows that the adsorbed methane can be replaced by water, which further promotes improved CBM recovery.