Research on the influence of temperature and effective stress on gas seepage and deformation law of loaded coal

To study the dynamic evolution characteristics of gas seepage and deformation of coal under different temperatures and effective stresses, based on the triaxial seepage test device of coal core, experiments on gas seepage of coal under different temperatures and effective stresses were carried out.The research results show that keep the effective stress unchanged, the permeability of the coal samples shows a decreasing trend with increasing temperature, and the maximum decrease is 21.99%.The change rate of coal permeability decreases in a negative exponential trend with the increase of temperature, and the maximum decrease is 23.01%.Temperature has a significant inhibitory effect on the gas seepage process of coal.At the same temperature, the permeability of coal gradually decreases with the increase of effective stress, and the maximum decrease is 60.56%.With the increase of effective stress, the rate change of permeability all decrease in a negative exponential trend, and the maximum decrease is 60.08%.The axial strain, radial strain and volumetric strain of the coal all show a decreasing trend with the increase of temperature.After heating up, the adsorption capacity of the coal weakens and the average kinetic energy of the molecules increases, thereby resulting in a tendency for the deformation of the coal to decrease.As the effective stress increases, the axial strain of the coal gradually increases, while both the radial strain and the volumetric strain show a decreasing trend.The increase in effective stress causes the expansion effect of gas adsorption on coal to be much greater than the contraction effect of gas desorption on coal, resulting in overall expansion deformation of coal.The research results can provide certain theoretical guidance for the reasonable arrangement of gas extraction parameters in the gas extraction process.