Experimental Study On Dynamic Change Law Of Coal Deformation And Gas Adsorption-desorption-seepage

With the increase of coal seam mining depth,the degree of gas disaster increases,which restricts the safe and efficient mining of mine gas.Gas extraction is an effective way to prevent and control gas disasters.The extraction process involves gas adsorption-desorption-seepage process.The study of coal deformation and adsorption-desorption-seepage characteristics under different influencing factors has become a key problem to improve the efficiency of gas extraction.The experimental samples were taken from Hudi Coal Mine in Shanxi Province.The gas adsorption-desorption-seepage characteristics and deformation law of coal under different gas pressure,temperature and axial pressure ratio were studied by using the self-developed coal solid-gas coupling experimental platform.Through the study,it is found that the whole process of coal gas adsorption-desorption-seepage can be divided into initial rapid response stage,medium-term slow growth stage and final stable stage.Gas adsorption capacity,adsorption rate,desorption rate and gas seepage flow of coal body increase with gas pressure;with the increase of temperature,the adsorption capacity and gas flow rate of coal are negatively correlated with temperature,and the desorption rate of coal is on the rise.When the temperature is 303 K,313 K,323 K.333 K and 343 K,the desorption rate is 82.31%,84.37%,85.82%,86.35%and 87.04%,respectively;with the increase of axial pressure ratio,the coal gas adsorption,desorption rate and gas flow showed a downward trend,and the coal gas seepage flow was 9.4 ml/min～20.4 ml/min.The stress-strain instrument is used to synchronously record the deformation of coal body.Through analysis,it is concluded that the radial and axial deformation of coal body are consistent in each stage,and the radial deformation is always greater than the axial deformation.With the increase of gas pressure,the deformation of coal at each stage and the permeability show an increasing trend.The adsorption amount of coal is positively correlated with the radial and axial deformation of coal;with the increase of temperature,the adsorption deformation of coal body showed a decreasing trend.When the temperature was 303 K.313 K,323 K,333 K and 343 K,the desorption residual deformation rates were 21.7%,21.29%,19.95%,17.37%and 17.00%,respectively.It was negatively correlated with temperature,and the permeability showed a decreasing trend,with the change of 2.17×10-17～4.37×10-17 m2;adsorption deformation,desorption deformation and permeability decrease with the increase of axial pressure ratio;the deformation and permeability of coal under low seepage pressure and high seepage pressure are consistent.The deformation and permeability of coal are positively correlated with seepage pressure.The maximum permeability of coal is 2.01 times of its minimum value.Based on the physical experimental study,the adsorption-desorption-seepage model of coal gas is established,and the variation law of physical experiment and numerical simulation results is consistent.The maximum absolute error of coal body strain is 0.07×10-2 and the maximum relative error is 0.43.Maximum absolute error of coal permeability 2.22,maximum relative error 0.55.The research results provide a theoretical basis for coal seam gas drainage.