Response characteristics of gas pressure under simultaneous static and dynamic load: Implication for coal and gas outburst mechanism

Coal and gas outbursts are dynamic disasters in which a large mass of gas and coal suddenly emerges in a mining space within a split second. The interaction between the gas pressure and stress environment is one of the key factors that induce coal and gas outbursts. In this study, first, the coupling relationship between the gas pressure in the coal body ahead of the working face and the dynamic load was investigated using experimental observations, numerical simulations, and mine-site investigations. It was observed that the impact rate of the dynamic load on the gas-bearing coal can significantly change the gas pressure. The faster the impact rate, the speedier the increase in gas pressure. Moreover, the gas pressure rise was faster closer to the impact interface. Subsequently, based on engineering background, we proposed three models of stress and gas pressure distribution in the coal body ahead of the working face: static load, stress disturbance, and dynamic load conditions. Finally, the gas pressure distribution and outburst mechanism were investigated. The high concentration of gas pressure appearing at the coal body ahead of the working face was caused by the dynamic load. The gas pressure first increased gradually to a peak value and then decreased with increasing distance from the working face. The increase in gas pressure plays a major role in outburst initiation by resulting in the ability to more easily reach the critical points needed for outburst initiation. Moreover, the stronger the dynamic load, the greater the outburst initiation risk. The results of this study provide practical guidance for the early warning and prevention of coal and gas outbursts.