Application of Acoustic Emission Technique to Prediction of Rockburst

为了阐明岩爆前兆现象，研究了岩石主断裂前的声发射的时空变化。在恒应变率的单轴压缩条件下，虽然随着应力的增加，声发射沿最终断层面集中，但声发射倾向于在最终断裂前迁移。在此阶段，声发射计数率和事件率也暂时降低。宏观断裂前声发射的时间和空间异常可归结为最终断裂面周围微裂纹的整合和宏观裂纹的扩展引起的应力松弛。本研究证实的声发射前兆现象对预测冲击地压具有较好的应用前景，并利用矩张量反演法确定了声发射的震源机制。缩尺模型研究表明，煤层矿体采场等平面开挖前方的动能是由单轴压缩或双耦合作用产生的。另一方面，开挖工作面后的应力应变是由包括单轴拉伸在内的各种力系模式引起的。缩尺模型研究中的应变分析表明，声发射的震源机制与开挖周围的应力状态很好地对应。考虑到由屈服区及其周围组成的系统的整体不稳定性，还推导了微震事件发生的判据。这些准则是以不同应力状态(如多轴、双轴和单轴应力)的不等式表示的。该判据表明，塔哈微震事件的发生受几个参数控制，这些参数代表了破裂前和破裂后的形变特征。

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.