矿震诱发高应力巷道厚顶煤动力失稳机制

Mechanisms behind mine earthquake-induced dynamic instability of thick top coals in high-stresses roadways

【目的】厚煤层沿底掘进煤巷普遍存在厚顶煤,工作面矿震对巷道厚顶煤产生动载作用,易诱发厚顶煤动力失稳和冒顶-冲击复合灾害,亟需探究矿震动载作用下巷道厚顶煤动力失稳机制。【方法】以陕西彬长矿区深部厚顶煤巷道为工程背景,调研分析深部高应力巷道厚顶煤动力失稳特征,数值模拟研究不同静动载作用下巷道厚顶煤多场演化规律,提出矿震诱发高应力巷道厚顶煤动力失稳机制。【结果和结论】结果表明,巷道厚顶煤冒顶区域距回采工作面较远,冒顶后裸露平整顶板,顶板锚索拉断,冒顶区域附近均发生大能量矿震,呈现冒顶-冲击复合灾害现象。随静载增加,巷道围岩裂隙发育深度及变形不断增加;随动载作用时间和动载强度增大,顶煤震动速度、加速度及裂隙发育程度不断增大,顶煤离层量显著增加;顶板锚杆索均位于顶煤裂隙发育区,支护性能大幅降低。静动载作用下巷道厚顶煤累积损伤及离层量不断增大,大能量矿震动载使浅部破碎顶煤震动速度及加速度显著增大,作用在锚索上载荷超过其承载能力,锚索被拉断,浅部破碎煤体以较高速度冒落,诱发厚顶煤动力失稳和冒顶-冲击复合灾害。在此基础上,提出了采用重建厚顶煤主被动支护和加强卸压的深部巷道厚顶煤动力失稳灾害的防治方法。

[Objective]Thick top coals are common in roadways excavated along the bottom of thick coal seams.Mine earthquakes along the mining face can exert dynamic loading on thick top coals in roadways,prone to induce the dynam-ic instability of thick top coals and even roof fall-rock burst compound disasters.Therefore,there is an urgent need to ex-plore the mechanisms behind the dynamic instability of thick top coals in roadways under dynamic loading induced by mine earthquakes.[Methods]This study investigated a roadway of deep thick top coals in the Binchang mining area,Shaanxi.Specifically,this study analyzed the dynamic instability characteristics of deep thick top coals in the high-stress roadway,investigated the multi-field evolutionary patterns of thick top coals in the roadway under different static/dy-namic loading using numerical simulations,and determined the mechanisms behind the mine earthquake-induced dy-namic instability of thick top coals in high-stress roadways.[Results and Conclusions]The results indicate that the roof fall zone of thick top coals in the roadway is far from the mining face.Roof falls were followed by the exposure of the flat roof and the breaking of anchor cables in the roof.Concurrently,high-energy mine earthquakes occurred near the roof fall zone,resulting in roof fall-rock burst compound disasters.An increase in static load corresponded to continu-ously increasing fracture depths and deformations of surrounding rocks in the roadway.As the time and intensity of dy-namic loading increased,the vibration velocity,acceleration,and fracture developmental degree of top coals increased gradually,along with significantly increasing detachment layer number of top coals.The anchor bolts and cables for the roof,all located in the fracture zone of top coals,showed significantly reduced support performance.Under the static/dy-namic loading,the cumulative damage and detachment layer number of thick top coals in the roadway increase gradu-ally.The dynamic loading induced by high-energy mine earthquakes leads to significantly elevated vibration velocity and acceleration of shallow broken top coals.Consequently,the anchor cables break off when the load acting on them exceeds their bearing capacities,and the shallow broken coals fall at a relatively high speed,thus inducing the dynamic instability of thick top coals and even roof fall-rock burst compound disasters.Based on these results,this study pro-poses preventing and controlling the dynamic instability of deep thick top coals in roadways by reconstructing the active and passive supports of thick top coals and reinforcing pressure relief.