Influence of Different Coal Seam Gas Pressures and their Pulse Characteristics on Coal-and-gas Outburst Impact Airflow

Coal-and-gas outburst (CGO) is a major challenge to safe and efficient coal mining worldwide. As the primary energy source of CGO, coal seam gas determines the impact dynamic characteristics of the coal–gas two-phase flow. Therefore, the process of gas pressure evolution obtained from an experiment was used as the initial condition to study the influence of the initial gas pressure on the flow characteristics of the CGO airflow. The results show that, during CGO process, the gas pressure decreased either periodically (pulse) or in a continuous manner. The static pressure in the roadway showed the evolution of alternating positive–negative pressure transition. The range of the positive pressure zone and static pressure value decreased with increasing gas pressure. The velocity of the CGO airflow exhibited a rapid rise to the maximum followed by a decreasing trend with periodic fluctuations. The increase in the coal seam initial gas pressure led to an increase in peak velocity of the CGO airflow, distribution range, and duration of the high-speed airflow in the roadway. During CGO process, expansion and compression waves appeared alternately at a frequency increasing with gas pressure. The existence of the pulse feature increased the velocity of the CGO airflow in the entire roadway. However, the effect weakened gradually with increasing distance from the working surface. A rational arrangement of disaster prevention fences, refuge chambers, and other facilities based on the distribution characteristics of impact airflow velocity distribution in the roadway during the CGO process can help reduce the damage caused by CGO impact disasters.