坚硬顶板三次强扰动临空宽煤柱诱冲机制及防治

Instability mechanism and prevention of wide coal pillar with three strong stress disturbances under hard roof

蒙陕矿区矿井多采用留宽煤柱双巷掘进工艺,造成工作面沿空巷道受多次采掘扰动,受采空区顶板、煤柱尺寸等影响,回采巷道围岩应力演化过程中出现多次集中现象,甚至诱发冲击显现,严重制约了工作面的安全高效生产。以蒙陕矿区葫芦素煤矿21103工作面为例,通过对沿空巷道冲击显现特征分析,采用数值模拟对巷道形成之后在上区段21102工作面回采时、回采后及本工作面回采时的3次高强度开采扰动进行分析,研究了沿空巷道围岩应力的演化过程;利用现场微震监测和采动应力监测,对煤柱内应力变化情况和开采扰动下的围岩活动特征进行了研究;提出了基于厚硬顶板、宽煤柱条件下沿空巷道冲击地压防治技术方案。研究结果表明:(1)在上区段工作面及本工作面回采扰动下,宽煤柱内应力逐次升高,形成应力集中,具有较高的静载荷水平;(2)采空区上覆顶板弯曲下沉、滞后垮冒等对沿空巷道带来强烈扰动,造成沿空巷道冲击危险性急剧增加;(3)煤柱内布置的联络巷加剧了巷道围岩形成的高应力集中,在顶板断裂等强动载作用下,易达到冲击载荷并诱发冲击;(4)采取厚硬顶板“钻-切-压”措施能够降低顶板带来的集中静载并弱化其动载作用,对煤柱内高应力区实施大直径钻孔降低高应力区的应力集中程度。通过防冲方案的实施,现场工程显示沿空巷道围岩应力增加值得到控制,易诱发冲击的大能量事件大幅减少,为指导多次扰动条件下的宽煤柱沿空巷道冲击地压防治提供借鉴。

In the Inner Mongolia and Shaanxi mining area,many mines adopt the double roadway driving technology.The width between the two roadways is wide,which will cause the roadways along the goaf to be disturbed for many times.Under the influence of goaf roof and coal pillar size,the surrounding rock of roadway shows the phenomenon of stress concentration,even rock burst.Taking the 21103 working face of Hulusu coal mine as an engineering case,the three disturbances of roadway were analyzed by numerical simulation.The three stages include the stage when the upper working face is mined,the stage after the upper working face is mined and the stage when the working face is mined.The microseismic monitoring and stress monitoring were carried out on site to analyze the variation of stress in the coal pillars and the characteristics of surrounding rock activity.On the basis of the above research,the technical scheme of rock burst prevention and control for thick hard roof and wide coal pillar was put forward.The results show that(1)under mining disturbance,the internal stress of wide coal pillar increases gradually,forming a stress concentration.(2)The bending,sinking and lagging collapse of goaf roof bring a strong disturbance.(3)The contact roadway increases the stress concentration,which is easy to reach the critical condition and induce impact.(4)The“drilling-cutting-pressuring”roof pressure relief measures can reduce the concentrated static load and dynamic load,and the implement of large diameter drilling can reduce the stress concentration.Through the implementation of the anti-scour scheme,the stress growth of surrounding rock of gob side entry is controlled,and the large energy events are greatly reduced,which provides guidance for the prevention and control of rock burst.