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低透气性煤层工作面煤与瓦斯突出灾害中心体致灾机理

Mechanism of coal and gas outburst disaster in low permeability coal seam mining face

  • 摘要: 为有效揭示低透气性煤层回采工作面煤与瓦斯突出机理,提高监测和防治的针对性与有效性,基于瓦斯赋存状态和开采扰动等因素建立了突出灾害中心体力学模型,通过理论分析、相似模拟试验和现场试验的方法,验证了该理论假设,揭示了中心体致灾机理,并验证了微震与突出危险的关联性。相似模拟试验结果显示:在煤壁距中心体60~20 m时中心体逐渐孕育和发展,至20~10 m时中心体突出风险急剧升高,该范围即宏观的中心体突出临界区域,是重点防治时期和位置,该结论在寺家庄矿15112回采工作面基于钻屑瓦斯解吸指标K1值的试验中得到验证,突出灾害中心体致灾机理假设也得到验证。结果表明:吸附瓦斯在节理、裂隙等非均质性的孔洞中由于局部煤体破碎且渗透性升高而大量解吸为游离瓦斯,与煤粉混合成具有高能量的气固两相流体,形成突出灾害中心体;中心体在低透气性煤层中是客观性存在的,且赋存于多个位置,采动效应提供了外在动力,导致煤层应力环境和瓦斯状态发生变化,易诱发中心体突出;从中心体致灾的角度得到微震与突出危险间具有较良好的拟合关系,说明微震是有效的突出危险监测手段,为进一步提高突出监测及防治的针对性和有效性提供了方向。

     

    Abstract: In order to effectively reveal the mechanism of coal and gas outburst in the working face of low permeability coal seam, and improve the pertinence and effectiveness of monitoring and prevention,the central mechanical model of outburst disaster was established based on factors such as gas occurrence state and mining disturbance. Similar simulation experiments and field experiments have verified the theoretical hypothesis, the disaster-causing mechanism of central body was revealed, and the correlations between microseismic and outburst hazards was verified. The results of similar simulation experiments show that the centrosome gradually inoculates and develops when the coal wall is about 60-20 m away from the central body, and the risk of central body outburst increases sharply at 20-10 m. This range is the macroscopic critical mass of central body outburst, which is the key prevention period and position. This conclusion has been verified in the test of No.15112 working face of Sijiazhuang Mine based on the K1 value of drilling cuttings gas desorption index, and the hypothesis of disaster-causing mechanism of outburst disaster center body has also been verified.The results show that the adsorbed gas is largely desorbed into free gas due to local fragmentation and the increase of permeability in heterogeneous holes such as joints and cracks, and mixed with pulverized coal to form a gas-solid two-phase fluid with high energy, forming a outburst disaster center. The center body exists objectively in the low permeability coal seam, and occurs in multiple locations. The mining effect provides external driving force, which leads to changesin the stress environment and gas state of the coal seam, and is easy to induce the center body outburst. From the perspective of of central body hazard, there is a good fitting relationship between microseismic and outburst danger, indicating that microseismic is an effective means of outburst danger monitoring, which provides a direction for further improving the pertinence and effectiveness of outburst monitoring and prevention.

     

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