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三轴加载下构造煤组合体渗透率应力敏感性演化及主控因素分析

Evolution of permeability stress sensitivity and analysis of controlling factors for tectonic coal-bearing composites under triaxial loading

  • 摘要: 探究煤层渗透率应力敏感性系数的变化规律,对于揭示抽采过程中瓦斯衰减动态演化机理至关重要。为更好地契合实际煤层赋存形式,选择含构造煤组合体作为实验对象,利用煤岩心渗透率自动测试仪,结合随机森林方法,分析不同因素对渗透率应力敏感性系数显著性特征影响的变化规律。研究结果表明,随着轴压、围压增大,含构造煤组合体的渗透率应力敏感性系数均减小且单位应力下降幅度逐渐降低。随着气体压力逐渐增大,渗透率应力敏感性系数呈增大趋势。随着构造煤厚度占比的增大,渗透率应力敏感性系数呈先减小后增大趋势。通过建立随机森林模型,计算各因素对模型预测误差增加的贡献,对各因素显著性进行评估,得出轴压、围压、构造煤厚度占比是影响煤体渗透率应力敏感性系数的关键因素,且力学因素变化的影响最为显著,气体压力对煤体渗透率应力敏感性系数的影响最不明显。

     

    Abstract: Investigating the variation patterns of the permeability stress sensitivity coefficient of coal seams is crucial for revealing the dynamic evolution mechanism of gas attenuation during the extraction process. To better conform to actual coal seam occurrence conditions,tectonic coal-bearing composites were selected as the experimental objects. Using an automatic coal-rock core permeability tester combined with the random forest method,the variation patterns of the influence of different factors on the significance characteristics of the permeability stress sensitivity coefficient were analyzed. The results indicate that as the axial pressure and confining pressure continuously increase,the permeability stress sensitivity coefficients of tectonic coal-bearing composites decrease,and the magnitude of the unit stress drop gradually diminishes. As the gas pressure gradually increases,the permeability stress sensitivity coefficient exhibits an increasing trend. As the proportion of tectonic coal increases, the permeability stress sensitivity coefficient first decreases and then increases. By establishing a random forest model, the contribution of each factor to the increase in model prediction error was calculated, and the significance of each factor was evaluated. It is concluded that axial pressure,confining pressure,and the proportion of tectonic coal are the key factors affecting the permeability stress sensitivity coefficient of coal,with mechanical factors exhibiting the most significant influence,while gas pressure has the least significant effect on the permeability stress sensitivity coefficient.

     

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