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工作面过上覆遗留煤柱致灾机理及超前区域防治技术研究

Disaster mechanism during passing of working face under overlying remnant coal pillar and advanced regional prevention technology

  • 摘要: 浅埋近距离煤层下伏工作面开采通过上覆遗留煤柱时,易发生强矿压动力灾害,造成人员设备损伤,严重威胁矿井安全生产。采用特征归纳、数值模拟计算、力学模型分析等研究方法,明确浅埋近距离煤层上覆遗留煤柱灾害发生规律,揭示强矿压致灾机理。研究表明:上覆遗留煤柱强矿压致灾机理为工作面出煤柱时,煤柱及上覆承载体受扰动突然失稳,能量瞬间传递至采场,以动能形式释放,造成强矿压动力灾害。基于“垮落充填体支撑+关键岩层弱化+应力传递路径转移”防治理念,提出通过改造煤柱及承载体运移空间、弱化关键岩层、均布集中应力及转移应力传递路径的分段水力压裂超前区域弱化防治技术,并在典型工作面开展工程试验。工程试验结果表明:水力压裂实施过程中,泵注压力峰值达23.4 MPa,压力变化总体呈“锯齿状”波动且伴有压力突降,突降达60余次,岩体内部人造主裂缝与微裂缝持续交替发育,有效破坏了岩体的完整性;治理后,来压峰值及来压平均值分别降低15.41%,8.29%,动载系数峰值及平均动载系数分别降低17.39%,11.88%,立柱最大下沉量降幅达50.00%且小于0.4 m,工作面巷道顶板最大下沉量降幅33.33%。工作面安全通过上覆遗留煤柱影响区域,分段水力压裂超前区域弱化技术可实现浅埋近距离煤层上覆遗留煤柱强矿压灾害的有效防治。

     

    Abstract: When the mining of the underlying working face of shallow and close seam passes under the overlying remnant coal pillar, it is easy to have an intensive mine pressure-induced dynamic disaster, resulting in personnel and equipment damage, which seriously threatens the safety of mine production. The characteristics induction, numerical simulation calculation, mechanical model analysis and other research methods are used to clarify the occurrence of the hazards of the overlying remnant coal pillars in the shallow and close seams, and reveal the disaster mechanism caused by intensive mining pressure. The research shows that the disaster mechanism of the intensive ground pressure caused by the overlying remnant coal pillar is that when the working face passes under the coal pillar, the coal pillar and the overlying bearing body are disturbed and suddenly lose stability, and the energy is transferred to the stope instantly, which is released in the form of kinetic energy, resulting in the intensive ground pressure-induced dynamic disaster. Based on the prevention and control idea of “collapsed rock support+weakening of key rock stratum+transfer of stress transmission path”, the prevention and control technology of weakening for front area using subsectional-hydraulic fracturing was proposed by modifying the coal pillar and bearing body migration space, weakening key rock stratum, uniformly distributing concentrated stress and transferring stress transmission path, and engineering tests are carried out at typical working faces. The engineering test results show that during the implementation of hydraulic fracturing, the peak value of pumping pressure reaches 23.4 MPa, the pressure changes generally in a “zigzag” shape, accompanied by a sudden drop of pressure for more than 60 times, and the artificial main fractures and micro fractures in the rock mass continue to develop alternately, effectively destroying the integrity of the rock mass; After treatment, the peak value and average value of periodic pressure decreased by 15.41% and 8.29% respectively, and the peak value and average dynamic load coefficient decreased by 17.39% and 11.88%, respectively. The maximum contraction of the shield cylinder was 50.00% and less than 0.4 m, and the maximum contraction of the gate road roof was 33.33%. The working face safely passed through the affected area of the overlying remnant coal pillar, and the advanced area weakening technology of subsectional- hydraulic fracturing can effectively prevent and control the intensive ground pressure disaster of the overlying remnant coal pillar in shallow and close seams.

     

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