采动影响下逆冲断层“活化”特征试验研究

Experiments on the characteristics of thrust fault activation influenced by mining operation

以义马矿区的F16大型逆冲断层为背景,结合断层影响下5个矿井的地质钻探和井下揭露情况搭建相似模型,在考虑断层面的分形特征和断层面两侧覆岩赋存特征的基础上,综合运用声发射监测、采场覆岩位移和采场应力监测系统,研究采动影响下断层"活化"前后的覆岩运动特征、矿压显现规律和动力响应特征。研究表明:受逆冲断层南北两侧地层覆岩结构复杂和构造运动影响,断层"活化"前后工作面覆岩运动特征、矿压显现规律和动力响应明显不同。断层"活化"前,工作面覆岩"三带"特征明显,底板应力基本不受采动应力影响,声发射信号较弱。进入断层影响区后,顶板离层量呈跳跃式增长,采动应力诱发断层"活化",底板应力达到最大值,声发射的总事件数和能率发生突变增加。当推过断层一段距离后,随着上盘关键岩层悬臂岩梁长度增加,工作面煤壁发生屈曲破坏,底板应力增加,待岩梁垮断挤压应力释放后,底板应力随之下降,伴随着工作面上方"短砌体梁"结构发生切落且沿断层面滑动,产生大量声发射信号。

With the background of F16 large thrust fault in Yima mining area, a similar model was built based on the geological drilling data and underground exposed structure from five coal mines influenced by the fault. Considering the fractal characteristics and occurrence of overburden on both sides of fault surface, the overburden movement, mine pressure behavior law and dynamic response before and after fault activation were studied by monitoring acoustic emission（AE）, overlying strata displacement and stress in mining area. The results demonstrate that the overburden movement, mine pressure and dynamic response show a great difference before and after fault activation influenced by the complicated overburden occurrence structure and the tectonic movement. Before fault activation, the ＂three zone＂ of overburden is obvious, and the floor stress is hardly affected by mining and the AE signal is weak. In the fault influential area, the roof abscission layer increases immensely, the fault activation is triggered by mining stress, the floor stress reached the maximum, and the total number of AE events and energy release rate grows abruptly. After crossing a certain distance from the fault, the buckling failure of mining face and the floor stress increase with the increasing length of cantilever rock beam. When bearing stress is released by the caving of antilever rock beam, the floor stress decreases, and the ＂short block voussoir beam＂ above the workface cuts down and slides along the fault plane with enormous AE events.