近直立特厚煤层组中间岩板诱发冲击矿压机理及其防治

Study on the mechanism of rock bursts caused by rock plates between subvertical extra-thick coal seams and its prevention and treatment

近直立特厚煤层具有煤层厚、赋存倾角大、煤层间岩石层坚硬的特点,在煤层组群联合开采过程中,煤层间岩板是诱发煤层采掘空间冲击矿压灾害发生的关键因素。通过研究煤岩体内微震事件与应力集中之间的关系,分析了煤层间岩板诱发冲击矿压的机制。采用弹性理论,建立了煤层间岩板破断力学模型,得到了岩板破断时能量计算公式。提出了降低岩板破断时悬顶尺寸,破坏煤岩体完整性,使煤岩体中的动静载叠加应力始终小于引发冲击矿压的临界值以下,从而避免岩板破断诱发冲击矿压的防冲机理。通过对煤层间岩板进行注水爆破和煤体注水,降低了岩板和煤层微震事件频率和能量值,卸压效果显著,有效避免了岩柱诱发冲击矿压。

Subvertical extra-thick coal seams are characterized by thick coal seams, large dip angles,and hard rock plates between coal seams. The rock plate between coal seams is a critical factor that leads to severe rock bursts in combined mining of coal seams. By studying the relation between stress concentration and microseisms in coal and rocks, the mechanism of rock bursts caused by rock plates between coal seams is analyzed. Based on the elasticity theory, the mechanical model of breaking in rock plates between coal seams is established, and the energy calculation formula of rock plate breaking is obtained. The prevention mechanism against rock bursts caused by the breaking of rock plates is proposed that the stacked stress of static and dynamic loads in coal and rock mass is always below the critical value of causing rock bursts through reducing the size of hanging rock plate and breaking the integ rity of coal and rock mass. Water injection and blasting in rock plates between coal seams and water injection in coal mass can reduce the frequency of microseisms and energy value in rock plates and coal seams, and remarkably relieve pressure, and effectively prevent the rock bursts caused by rock pillars.