Experimental Study On Deformation And Seepage Of Coal Containing Methane In Pressure Elevating

China owns abundant coal seam gas，but a large of coal seam gas is underkilometers and most of it is stored in coal reservoirs of low permeability, which is notconducive to industrial exploitation. Therefore, the general rules in the system study ofgas pressure lifting process of large temperature range of gas migration in coalcontaining gas is very meaningful. In addition, coal seam of low permeability showssignificant slippage effect, the phenomenon is propitious to coal seam gas extraction，thus exploring the slippage effect of gas pressure in the lifting process is of greatpractical significance.In this paper, coal seam coal sample taken from K2coal seam of ChongqingSongzao Mine is regarded as the research object. Using the self-developed triaxialservo-controlled seepage equipment for thermo-fluid-solid coupling of coal containingmethane, the author carried out the experiment of unloading after the first loading underdifferent degrees, while changing the gas pressure to simulate the coal seam gasgathering and exploitation during adsorption and desorption process to explore coaldeformation and permeability characteristics. Through parallel seepage tests of Heunder identical experimental conditions, the author has investigated the effects ofslippage effect on coal seepage characteristics. Through this research, the followingresearch results were obtained:1）The evolution between coal containing gas deformation and permeability in theprocess of gas pressure lifting was investigated and the experimental results show that:strain with increased pressure were varied approximately linearly in the boost phase,axial strain increased and radial strain reduced with the decrease of the pressure in buckstage. Test specimen permeability and pressure was approximately two times parabolachange with first decreasing and then increasing slightly and reaching the minimum atabout3.0MPa with the pressure increase. As the pressure increased and decreased,volumetric strain and permeability of coal presented similar trend, the inflection point isabout1.0MPa.2）The effect of temperature on gas containing coal deformation and permeabilitycharacteristics in the gas pressure lifting process had been investigated. Under the samegas pressure, axial strain decreased after the first increasing with increasing temperatureand reaches the maximum at40℃. Under the same gas pressure, the radial strain decreased overall with increasing temperature. When the gas pressure is constant,permeability showed a decreasing trend after first increasing rapidly. The maximumvalue appeared at50℃3）The Effect of number of cycles on gas containing coal deformation andpermeability characteristics in the gas pressure lifting process had been investigated.The axial strain increased and the radial strain decreased with the number of cyclesincreasing under the condition of filling the CH4both in step-up and step-down phase,axial strain increased and the radial strain decreased with the number of cyclesincreasing as gas pressure increased under the condition of filling the He. Permeabilityapproximately linearly decreased with the number of cycles increasing.4） The effect of gas adsorption on gas containing coal deformation andpermeability characteristics in the gas pressure lifting process had been studied. Whenthe coal samples were filled with He, CH4respectively, the strain of coal samplepresented a consistent change tendency with gas pressure in the process of increasingthe gas pressure. Coal permeability decreased with increasing pressure when filling thetwo gases, and Inflection point occurred around about1.0MPa. The permeability of coalshowed higher when using He as the test gas.5）The Effect of gas slippage effect on gas containing coal deformation andpermeability characteristics in the gas pressure lifting process had been also investigatedin this study. Permeability variation caused by slippage effect changed slowly alongwith the change of air pressure. However, inflection point occurred around about1.0MPa in both the boost and buck stages. Permeability variation caused by slippageeffect presented the power exponential function change with the increase of gas pressureand increased with increasing temperature. In addition, permeability variation caused byslippage effect showed a decreasing trend with the increased number of cycles.