A New Risk Indicator of Outburst Based on Coal-Seam Temperature Variation and Acoustic Emission Signal

The process of coal and gas outburst (hereinafter referred to as "outburst") is inevitably accompanied by temperature variation. To further reveal the temperature evolution law and proposal of risk indicator of deep outburst, taking the outburst coal seam of Pingmei No.11 Coal Mine as the research object, the outburst tests with simulated buried depths of 600 m, 800 m, 1000 m, 1200 m, 1400 m, and 1600 m are carried out. The relationship between outburst parameters (critical gas pressure, test-effective stress), acoustic emission signal, and temperature variation is analyzed. The approximate range of the critical buried depth of Pingmei No.11 Coal Mine is given. According to the characteristics that the temperature variation decreases earlier than the acoustic emission signal, a new outburst risk indicator is established. The results show that the coal-seam temperature variation in the outburst process is determined by gas pressure and gas content. When the buried depth is higher than the critical depth, the influence of gas content on outburst is intensified, and the sensitivity of outburst to gas content is greater than that of gas pressure. The test-effective stress is negatively correlated with temperature, and the gas-expansion work is positively correlated with temperature. The development of outburst leads to the variation in internal temperature of coal seam. The temperature variation eventually reacts to the development of outburst. The risk indicators P2, N1, N2, and S are defined based on acoustic emission signal and temperature variation. According to the change of risk indicators, the outburst risk is divided into four grades: "no, weak, moderate, and strong", which is of great significance for the prediction and early warning of outbursts. The development of outburst incubation leads to the variation of internal temperature of coal seam, and the temperature variation eventually reacts to the development of outburst incubation.The variation of internal temperature of coal seam in the outburst process is determined by gas pressure and gas content. When the critical buried depth is exceeded, the sensitivity of outburst to gas content is greater than that of gas pressure.The difference in falling time between of temperature variation and gas pressure in the process of outburst incubation is obtained.A new risk indicator of outburst based on AE signal and temperature variation is proposed.