Meikuang Anquan (Oct 2022)
Spatial-temporal evolution law of temperature in coal seam and roadway during coal and gas outburst
Abstract
A multifunctional outburst simulation test system was independently developed to monitor the temperature of the coal seam and roadway throughout the entire outburst process. Outburst simulation experiments under different gas pressures were carried out. The results show that: ① the coal seam gas pressure quickly drops to atmospheric pressure after outburst, however, the temperature evolution of coal seam has a certain lag, which is mainly controlled by the desorption of adsorbed gas and the expansion of free gas; three stages can be seen in the coal seam temperature evolution characteristics: quick decline, rapid increase, and slow change; peak values of coal seam temperature decline are 0.56, 0.23, and 0.11 ℃, respectively, and average decline rates are 0.042, 0.015, and 0.008 ℃/s when the adsorption gas pressure is 2.0, 0.85, and 0.35 MPa; the higher the gas pressure is, the greater the coal seam temperature decline and the faster the decline rate is, which is positively correlated; ② the change of the roadway temperature is simultaneously influenced by various factors such as desorption of gas from the outburst coal, expansion and pressure relief of ejected gas, shock wave disturbance and heat exchange with the environment, showing an evolutionary trend of a brief increase followed by an immediate and significant decrease and finally rise to the ambient temperature; in the three tests, the peak values of roadway temperature drop are 3.19, 2.41 and 1.09 °C, and the average decline rates are 0.249, 0.188 and 0.094 °C/s, respectively; ③ the coal seam and roadway temperatures have overall similarity in time evolution and significant difference in the magnitude of change; the further fragmentation of the outburst coal body in the roadway and the large amount of desorption of gas are the main controlling factors for the evolution of the roadway temperature and the main reason for the large amount of decrease in the roadway temperature.
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