急倾斜巨厚煤层群难采资源开采的覆岩破断与能量释放规律
Law of overburden breaking and energy release in the mining of difficult coal resources in steeply inclined extra-thick coal seam group
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摘要: 针对急倾斜巨厚煤层群难采资源的安全开采问题,采用物理模拟实验与理论分析方法,对急倾斜巨厚煤层群不同开采工艺产生的覆岩变化、破断高度、微震能量等特征进行了分析与对比,推导了急倾斜巨厚煤层坚硬顶板破断积聚能量的理论计算公式,并由不同开采工艺的对比分析结果为急倾斜巨厚煤层群向深开采的方案设计提供思路。研究结果表明:急倾斜巨厚煤层群水平分段综放开采的中间岩柱集中破断形成岩柱与上部煤层顶板的联动效应,容易引发冲击地压等的动力灾害事故;走向长壁开采中区段煤柱的强支撑作用,使得急倾斜巨厚煤层群向深开采过程中覆岩破断高度与范围的增幅较小。通过构建急倾斜巨厚煤层坚硬顶板破断力学模型,推导得出急倾斜巨厚煤层坚硬顶板破断积聚能量计算公式。急倾斜巨厚煤层群采用走向长壁的累计微震能量24.28×105 J,较水平分段开采的累计能量小15.67%。水平分段综放开采过程中,单次开采的平均能量比走向长壁开采较低,且避免了煤柱留设时煤炭资源的浪费。顶板破断的能量不充分释放,容易造成其下次破断能量释放的峰值效应,且中间岩柱大范围集中破断容易对矿井的安全生产带来挑战。基于节约矿井资源的同时又能避免大范围覆岩集中破断的理念,建议在原有水平分段综放开采与顶板弱化调控基础上,增加对顶板与中间岩柱的弱化程度,避免岩柱大范围集中破断带来的矿井安全生产问题。研究结果为急倾斜煤层复杂条件矿井资源的有效利用与安全开采提供了参考。Abstract: Aiming at the problem of safe mining of difficult coal resources in steeply inclined extra-thick coal seam group,using the methods of physical simulation experiment and theoretical analysis,the characteristics of overburden change,breaking height and microseismic energy produced by different mining technologies in steeply inclined extrathick coal seam group are analyzed and compared. The theoretical calculation formula of energy accumulated by hard roof breaking in steeply inclined extra-thick coal seam is derived,and the comparative analysis results of different mining technologies provide some ideas for the scheme design of deep mining in steeply inclined extra-thick coal seam group. The results show that the central rock pillar of horizontal sublevel fully mechanized top coal caving mining in steeply inclined extra-thick coal seam group is broken intensively to form the linkage effect between the rock pillar and the upper coal seam roof,which is easy to cause dynamic disasters such as rock burst. The strong supporting effect of section coal pillar in longwall mining makes the increase of overburden breaking height and range smaller in the deep mining process of steeply inclined extra-thick coal seam group. By constructing the mechanical model of hard roof breaking in steeply inclined extra-thick coal seam,the calculation formula of hard roof breaking accumulated energy in steeply inclined extra-thick coal seam is derived. The accumulated microseismic energy of steeply inclined extra-thick coal seam group with strike longwall is 24.28×105 J,which is 15.67% less than that of horizontal sublevel mining. In the process of horizontal sublevel fully mechanized top coal caving mining,the average energy of single mining is lower than that of longwall mining,and the waste of coal resources due to coal pillar left is avoided. The energy of roof breakage is not fully released,which will easily lead to the peak effect of energy release in the next breakage. Moreover,the large-scale concentrated breakage of the middle rock pillar will easily bring some challenges to the safe production of the mine. Based on the idea of saving coal resources while avoiding a large-scale concentrated breakage of overlying strata,it is suggested that on the basis of the original horizontal sublevel fully mechanized top coal caving mining and roof weakening regulation,the weakening degree of roof and middle rock pillar should be increased to avoid the mine safe production problems caused by the large-scale concentrated breakage of rock pillars. The research results provide a reference for effective utilization and safe mining of coal resources in the steep coal seam with complex conditions.