深部煤层瓦斯含量分阶赋存规律及其与突出危险的关联

Hierarchical occurrence law of gas content in deep coal seams and its relationship with outburst prevention

  • 摘要: 我国目前采用的煤与瓦斯突出区域预测指标包括瓦斯压力和瓦斯含量两种,在不同矿区两者对突出危险的敏感性不一。煤与瓦斯突出机理是合理制定突出危险性预测指标的基础,“本源瓦斯主控说”突出机理暗示瓦斯含量在深部条件下对突出危险的敏感性要高于瓦斯压力。为了检验上述推论的正确性,对比选取了具有高地温、高压力特征的平煤八矿作为典型研究对象,其高地温与高压力特点使得深部煤层瓦斯赋存规律与浅部不同,瓦斯含量在某一“临界深度”以下产生负增长,导致瓦斯赋存规律呈现分阶特征,与瓦斯压力的线性递增赋存规律产生明显差别。采用理论计算、试验分析、数值模拟与现场验证相结合的方法,首先理论计算了平煤八矿瓦斯含量分阶赋存规律,并建立了考虑温度与压力竞争效应的固−流−热三场耦合模型,分析出现瓦斯含量随深度逆向减小的影响因素;然后对比地勘/采动时期的瓦斯含量和瓦斯压力的差异化赋存规律,验证了理论研究和数值模拟的研究结果;之后理论分析了研究矿区的突出能量纵向分布规律,并以现场瓦斯涌出量以及突出事故案例,对突出危险性分阶分布特征进行了正面和侧面验证;最后比较分析了深部条件下瓦斯压力与瓦斯含量对突出危险的敏感性差异,阐明了造成两者差异的内在原因。论文研究显示:深部逐渐增高的地温以及压力对瓦斯含量形成了竞争作用,使得瓦斯含量在某一深度以下可能产生负增长现象,形成临界深度。临界深度的大小受到地温梯度、吸附能力以及温度敏感系数等因素影响。“本源瓦斯主控说”强调吸附瓦斯在突出中的主控作用,在临界深度以深,瓦斯含量对突出危险的敏感性要大于瓦斯压力。尤其对于构造煤而言,瓦斯含量的区域预测指标要更为敏感可靠。论文研究成果从宏观角度验证了“本源瓦斯主控说”的正确性,对于深部煤岩瓦斯动力灾害防治具有一定的指导意义。

     

    Abstract: The prediction indexes currently used in China for coal and gas outburst area include gas pressure and gas content, which exhibit varying sensitivity to outbursts in different mining areas. The formulation of rational prediction indexes for outburst risk is based on understanding the mechanism of coal and gas outbursts. According to the “internal gas controlled theory”, it is inferred that under deep conditions, the sensitivity of gas content is higher than that of gas pressure. To verify this inference, this study selects Pingmei No.8 Coal Mine as a typical research site due to its high temperature and high pressure conditions. These conditions result in a different occurrence pattern of gases in deep coal seams compared to shallow ones, where below a “critical depth”, the gas content exhibits negative growth leading to a step-like occurrence pattern, distinct from the linear increase observed in gas pressure. Using a combination of theoretical calculation, experimental analysis, numerical simulation, and on-site verification, the hierarchical occurrence law of gas content in Pingmei No. 8 Mine was first theoretically calculated, and a s solid-flow-heat three-field coupling model considering the competition effect of temperature and pressure was established to analyze the influencing factors of the reverse decrease of gas content with depth. Furthermore, the differential occurrence patterns of gas content and gas pressure during geological exploration/mining periods were compared, verifying the research results of theoretical research and numerical simulation. Additionally, the vertical distribution pattern of outburst energy within the study area was theoretically analyzed while verifying step-like distribution characteristics through positive lateral verification using data on emitted gases amounts and documented outburst accidents cases. Finally,the differences between sensitivities towards outbursts were compared and analyzed between deep conditions for bothgas pressureandgascontent,andthe underlying reasons behind these differences are clarified. The research results of this paper verify the correctness of “internal gas controlled theory” from a macro perspective, and have certain guiding significance for the prevention and control of deep coal gas dynamic disasters.

     

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