基于声发射定位的自然裂隙动态演化过程研究

 利用MTS815岩石力学试验机和PCI-II声发射三维定位实时监测系统对取自锦屏II级水电站交通辅助洞的含自然裂隙大理岩岩样进行单轴压缩条件下的声发射(AE)测试，并结合AE振铃数实现对不同空间分布类型自然裂隙时空演化过程的精确定位和追踪。试验结果表明：含自然裂隙大理岩岩样受压破坏过程中的局部渐进特征显著，AE累计数曲线的上升与试验的加载过程和岩样内部的应力调整关系密切；单一型和平行型自然裂隙空间分布形式相对简单，在压应力水平较低时AE大事件(振铃数＞20)随着压应力的渐增沿自然裂隙面展布，当压应力接近峰值强度时，AE大事件在裂隙面末端部位大量集聚，并朝着最终的实际破裂方向扩展；含交叉型自然裂隙岩样体内的AE大事件在初始压密阶段分布相对均匀，但随着压应力的持续增加，裂隙面附近的AE数量逐渐增加，并向裂隙面的交叉部位集聚；混合型自然裂隙结构最复杂，但仍不难根据AE大事件的空间分布确定岩样内部的软弱部位及相应的应力场变化规律。以上试验和分析结果对于深入研究岩体破裂失稳机制具有一定的意义，也可为现场微震监测提供指导。

INVESTIGATION ON DYNAMIC EVOLUTION PROCESS OF NATURAL FRACTURES BASED ON ACOUSTIC EMISSION POSITION

Uniaxial compression tests on naturally fractured marble samples taken from the transportation tunnels of Jinping II hydropower station were carried out using MTS815 rock testing system. And the acoustic emission (AE) activities were monitored by PCI-II AE system during the whole experimental process. According to the AE counts，the precise positioning and tracking on the time-space revolution processes of natural fractures with different spatial distributions characteristics have been successfully achieved. Experimental results clearly indicate that the failure of fractured marble is a locally progressive failure process. The progressive increasing curve of acoustic emission cumulative boll number is closely related with the experimental loading process and stress readjusts and redistribution in rock. Both of the spatial distributions of single and parallel natural fractures are relatively simple. For the two types of marbles，the strong AE events (count＞20) are increasing along the natural fracture surface with the progressive increasing compressive stress at low stress level. When the compressive stress is close to the peak failure strength，strong AE events progressively accumulate at the end of the fracture tip；and then along the final rupture direction. For marble including intersectant natural fractures，the distribution of strong AE events are relatively uniform in the initial compaction stage. In addition，with the continuing increase in the compressive stress，the AE events around the fracture surface gradually increase；and then accumulate around the intersection point of fractures. The distribution of AE events in marble including mixed natural fractures are most complex than those of marble including other types of fractures. It is still not difficult to determine the internal weakness parts and the corresponding stress field distribution law based on the special distribution of strong AE event. The above experimental and analytical results are significant for investigating rock mass failure and instability mechanism，and also provide guidance for microseismic monitoring in fields.