Experimental Study On The Desorption Laws Of Loaded Gas-filled Coal With Slippage Effect

With the increase of coal mining mechanization, the depth of mining is increasing year by year, crustal stress, temperature and gas pressure are also gradually increasing. Studying on the seepage characteristics of gas-filled coal is of great significance for mine gas prevention and control. In this paper, through the self-developed heat-flow-solid-stress coupling adsorption and desorption experiment system of gas-filled coal, an experiment was carried out to investigate the seepage law of loaded gas-filled coal under different temperature and gas pressure. Based on theoretical analysis, we further analysed the seepage law of loaded gas-filled coal under the influence of temperature and gas pressure. General rules on slippage effect and critical conditions considering the slippage effect were studied in the seepage process of gas-filled coal. The main conclusions are as follows:(1) Effect of temperature on the permeability of loaded gas-filled coal is closely related to the stress-strain stage. In the stage of elastic deformation, the permeability decreases with the increase of temperature, and coal matrix internal expansion plays the leading role, which can be explained well using the porosity model. With the increase of gas pressure, the influence of temperature on the permeability of coal samples decreases gradually.(2) In the stage of elastic deformation, the permeability of gas-filled coal decreases with the increase of gas pressure first and tends to be stable afterward, showing an exponential law. When gas pressure is low, gas adsorption capacity is strong, and adsorption expansion deformation of coal skeleton is large, combined with the slippage effect, which lead to decline of permeability obviously. With the increase of gas pressure, gas adsorption effect tends to balance Adsorption expansion deformation of coal skeleton become smaller and smaller, effective stress variation caused by gas pressure emerging gradually, the change of permeability flatten out.(3) Gas seepage equation considering slippage effect can better describe the percolation process. General rules on slippage effect of gas-filled coal are presented. Based on the experimental study and theoretical analysis, the critical value of gas pressure considering slippage effect is about 1.8 MPa.