特厚煤层综放开采覆岩裂隙时空演化规律研究

Study on spatio-temporal evolution law of overlying rock fractures in fully mechanized caving mining of extra-thick coal seams

针对特厚煤层综放开采条件下采空区卸压瓦斯高效抽采问题,以陕煤建新煤矿4203工作面为研究背景,运用物理模拟及数值模拟等方法综合研究了试验工作面覆岩裂隙时空演化和特征参数变化规律,明确了裂隙场“三带”高度范围并采用钻孔窥视进行了现场验证。结果表明,随着工作面的不断推进,覆岩垮落高度不断增加,达到153 m后高度变化趋于稳定。而裂隙带上方空洞高度的变化规律与推进距离成负相关关系,随着推进距离增加而不断减小,最终趋于稳定。二维平面物理相似模拟得到试验工作面冒落带高度28 m,裂隙带高度158 m;现场钻孔成像表明工作面冒落带高度为28.72 m;利用FLAC^(3D)数值模拟软件,得出该地质和开采条件下覆岩裂隙带发育高度为155 m左右。综合分析得到4203工作面冒落带高度28.36 m,裂隙带高度156.5 m,为特厚煤层综放开采工作面卸压瓦斯高效抽采提供了理论指导。

Aiming at the problem of efficient pressure relief gas extraction in goaf under the condition of fully mechanized caving mining in extra-thick coal seams,taking the 4203 working face of Shaanxi Coal Jianxin Coal Mine as the research background,the spatio-temporal evolution and characteristic parameter variation rules of overlying rock fractures in the test working face were comprehensively studied using physical simulation and numerical simulation methods,and the height range of the“three zones”of the fracture field was defined and on-site verification was conducted using drilling hole peeping.The results show that with the continuous advancement of the working face,the collapse height of the overlying rock continuously increases,and the height changes tend to stabilize after reaching 153 m.The variation of the height of the cavity above the fracture zone is negatively correlated with the advance distance,and decreases as the advance distance increases,eventually stabilizing.The height of the caving zone and the height of the fracture zone in the test working face are 28 m and 158 m respectively through two-dimensional planar physical similarity simulation;Field borehole imaging shows that the height of the caving zone in the working face is 28.72 m;Using the FLAC^(3D) numerical simulation software,it is concluded that the development height of the overlying rock fracture zone under the geological and mining conditions is about 155 m.Based on comprehensive analysis,the height of the caving zone and the fracture zone in the 4203 working face are 28.36 m and 156.5 m respectively,providing theoretical guidance for the efficient pressure relief gas extraction in the fully mechanized caving mining face in extra-thick coal seams.