综放开采覆岩大结构作用下的冲击地压形成机制

Mechanism study of rock burst induced by overburden large structural action of fully-mechanized caving mining

覆岩结构影响着煤矿的矿压显现,甚至会引发冲击地压,因此,有必要对覆岩结构形成与演化规律进行深入研究。基于关键层理论提出了综放工作面"板-壳"覆岩大结构模型,分析了大结构作用下围岩应力演化特征。推导出覆岩大结构失稳能量释放表达式,得到了冲击地压发生的临界能量。采用微震监测方法,研究了矿震的空间分布和能量变化规律,研究得到:基本顶、亚关键层和主关键层组成的"板-壳"覆岩结构逐步演化,结构掩护下的矿震总能量依次程阶梯式上升,结构失稳矿震的总能量跳跃式增加;综放工作面主关键层控制的覆岩大结构失稳易引起的冲击地压。矿压监测表明:围岩应力下降突变由于板-壳结构失稳,上升突变由于结构下部岩层的周期破断引起的;覆岩大结构失稳的动压以及顶煤和直接顶产生的静压共同作用引起支架压力显著上升。

Overburden large structure affect coal mine strata behavior,seriously it will lead to rock burst.It is necessary for studying the formation and evolution law of overburden large structure.＂Plate-shell＂overburden large structure model is proposed based on the critical layer theory,surrounding rock stress evolution characteristics is analyzed.Overburden large structure instability released energy equation is deduced,and rockburst critical energy is achieved under large structure. Microseismic events spatial distribution and energy variation law was researched by Microseismic monitoring methods. Study showed that combined with main roof,sub-key layer and primary key layer＂Plate-shell＂overburden large structure gradually evolved,vibration total energy successively stepped increased under the cover of overburden large structure,structural instability vibration total energy skipped increased. Instability of overburden large structure controlled by primary key layer can lead to rock burst. Ground pressure monitoring showed that rock stress decreasing mutation since overburden large structure instability,rising mutations due to lower part rock cycle breakage under large structure. Support load significant increasing is caused by coupling effect between dynamic load of overburden large structure instability and static load of top coal and immediate roof.