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温度与有效应力对受载煤体瓦斯渗流及变形规律影响研究

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

  • 摘要: 为探究不同温度与有效应力作用下煤体瓦斯渗流及变形动态演化特征,基于煤岩心三轴渗流测试装置,开展了不同温度与有效应力条件下煤体瓦斯渗流实验。研究结果表明:保持有效应力不变,随着温度升高,煤体渗透率均呈现减小趋势,最大降幅为21.99%;煤体渗透率变化率随温度升高均呈负指数趋势减小,最大降幅为23.01%,温度对煤体瓦斯渗流过程具有明显抑制作用;在相同温度下,煤体渗透率随有效应力增大而逐渐减小,最大降幅为60.56%;随着有效应力增大,渗透率变化率均呈负指数趋势降低,最大降幅为60.08%;煤体轴向应变、径向应变、体积应变均随温度升高呈降低趋势,升温后煤体吸附能力减弱,分子平均动能增大,从而导致煤体变形量趋于减小;有效应力增大,煤体轴向应变逐渐增大,径向应变与体积应变均呈减小趋势,有效应力增大造成瓦斯吸附对煤体的膨胀作用远大于瓦斯解吸对煤体的收缩作用,从而导致煤体总体产生膨胀变形。研究结果可为瓦斯抽采过程中合理布置抽采参数提供一定的理论指导。

     

    Abstract: 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 remains 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.

     

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