Application of Acoustic Emission Technique to Prediction of Rockburst

研究了岩体主断裂前声发射的时空变化规律，阐明了岩爆前兆现象。在恒定应变率的单轴压缩条件下，声发射在最终断裂前有迁移的趋势，但随着应力的增加声发射在最终断裂面集中。在这个阶段，AE计数率和事件率也会暂时降低。宏观断裂过程中声发射的时空异常可以归结为最终断裂面周围微裂纹的整合和宏观裂纹的扩展所导致的应力松弛。研究证实的声发射前兆现象对岩爆的预测具有重要意义。此外，利用矩张量反演方法确定了声发射的源机制。尺度模型研究表明，煤层采空区等平面开挖前的ae是由单轴压缩或双偶压缩产生的。另一方面，开挖面后的ae是由包括单轴张拉在内的各种模式的力系统引起的。尺度模型研究中的应变分析表明，声发射的源机制与开挖周围的应力状态吻合较好。在考虑屈服区及其周围系统整体失稳的情况下，导出了微震事件发生的判据。该准则是根据各种应力状态（如多轴、双轴和单轴应力）的不等式制定的。该准则表明微震事件的发生是由几个参数控制的，这些参数代表了破坏前和破坏后区域的变形特性。

The temporal and spatial changes of acoustic emission prior to the main faulting of rock have been investigated to clarify precursor phenomena of rockburst. Under uniaxial compression with constant strain rate, AE tends to migrate just before the ultimate fracture, although AE concentrates along the eventual fault plane with increase of stress. At this phase AE count rate and event rate are also temporarily reduced. The temporal and spatial anomalies of AE proceding macroscopic fracture can be referred to stress relaxation associated with integration of microcracks around the eventual fracture plane and growth of macrocrack. The precursive phenomenon of AE confirmed in this study is promising to prediction of rockburst.In addition, the source mechanism of AE has been determined by means of moment tensor inversion. The scale model study has shown that AEs in front of a flat excavation such as mining panel in seam deposit are generated by uniaxial compression or double couple. On the other hand, AEs behind the face of excavation are caused by various modes of force system including uniaxial tension. The strain analysis in the scale model study suggests that the source mechanism of AE corresponds well to the stress state around the excavation.The criteria for occurrence of microseismic event has been also derived considering the global instability of a system comprising of the yielded region and its surroundings. The criteria are formulated in terms of inequalities for various stress states such as polyaxial, biaxial, and uniaxial stresses. The criteria imply taha occurrence of microseismic event is controlled by a few paramters representing the properties of deformation both in pre- and post failure regions.