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特厚煤层综放开采邻空动压巷道围岩变形机理及卸压控制

Mechanism of deformation and pressure relief control of dynamic gob-side entry surroundings in fully-mechanized caving mining for extra-thick coal seam

  • 摘要: 受工作面采动叠加影响,特厚煤层综放开采邻空动压巷道极易发生冲击地压、巷道大变形等强矿压显现现象,是采掘过程中的重点防控区域。以榆神矿区曹家滩矿井特厚煤层综放开采为工程背景,分析了邻空动压巷道强矿压显现机理,研究了邻空巷道围岩倾向和走向支承压力分布力学机制,提出于邻空巷道进行定向张拉爆破切顶卸压巷道围岩控制,并运用数值模拟及现场试验等方法对该技术的作用效果进行了综合研究。结果表明,特厚煤层综放开采条件下,工作面开采大空间采空区长悬臂结构断裂后形成台阶岩梁块体长度较大,其滑落失稳或关键层失稳均会引发强动压,该动压作用在煤柱上并进一步传递至超前区邻空巷道围岩是造成底鼓大变形的主要原因。于邻空巷道内进行定向切顶卸压后,可减弱本工作面后方采空区顶板与煤柱间的承压,邻空巷道围岩应力向远离巷道方向转移,应力峰值降低,应力范围减小。现场开展了不同切顶方式下的现场工程试验,基于定向张拉爆破的深孔切顶卸压技术可有效减小特厚煤层工作面端头区邻空动压巷道的围岩压力,定向切顶后邻空动压巷道超前支架平均荷载降低11%,巷旁煤柱体应力峰值降低10%,巷内底鼓严重段平均变形减小65%,有效提高了巷道稳定性,为特厚煤层综放开采邻空动压巷道强矿压大变形控制提供了一种有效手段。

     

    Abstract: Affected by the superposition of working face mining, strong rock pressure phenomena such as rock burst and large deformation easily occur in the gob-side entry when mining extra-thick coal seams. Taking the extra-thick coal seam mining of Caojiatan Coal Mine in Yushen Mining Area as the engineering background, the appearance mechanism of strong mine pressure in gob-side entry is analyzed and a surrounding rock control technology based on deep-hole directional tension blasting and pressure relief is proposed in our study. The effects of the technology are comprehensively studied by numerical simulation and field experiment. It was found that under the condition of fully-mechanized top-coal caving mining in extra-thick coal seam, the large space long cantilever structure of the gob roof breaks and forms a bench rock beam block with a large length. The instability of the long cantilever structure or the roof key layer will cause strong dynamic pressure, which acts on the coal pillar and further transmits to the surrounding rock of the gob-side entry in the advanced mining area, which is the main reason for the large deformation of the floor heave. Numerical study shows that when the directional roof cutting is performed in the gob-side entry, the surrounding rock stress is transferred away from the entry to both sides. The peak stress value is significantly reduced and the stress range is reduced. The engineering test under different roof cutting conditions was carried out in the field. It was found that the deep-hole roof cutting pressure relief technology based on directional tension blasting can effectively reduce the surrounding rock pressure of the gob-side entry at the end of the ultra-thick coal seam working face. The average load of fore support in the entry was reduced by 11% and the average deformation of floor in the serious section of the entry was reduced by 65% after roof cutting. The combined blasting is beneficial to further reduce the deformation of the entry surroundings and improves the stability of the entry. The research results provide an effective method for controlling the deformation of entry induced by strong mining pressure in ultra-thick coal seam mining.

     

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