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声发射的时空变化。在恒定应变率的单轴压缩条件下，声发射在最终破裂前有迁移的趋势，但随着应力的增加，声发射沿着最终的断层面集中。在该阶段，AE计数率和事件发生率也暂时降低。宏观断裂过程中声发射的时空异常反映了微裂纹在最终断裂面附近的整合和宏观裂纹的扩展引起的应力松弛。研究证实了声发射的振荡现象，为岩爆预测提供了依据，并通过矩张量反演确定了声发射的震源机制。缩尺模型试验研究表明，在诸如煤层存款中的开采盘区的平坦开挖前方，声发射是由单轴压缩或双力偶产生的。另一方面，开挖面后的AE是由包括单轴拉伸在内的各种力系模式引起的。模型试验中的应变分析表明，AE的震源机制与基坑周围的应力状态有很好的对应关系，并考虑到由屈服区及其周围组成的系统的整体不稳定性，导出了微地震事件发生的判据。该标准制定在各种应力状态，如多轴，双轴和单轴应力的不等式。该判据表明，微地震事件的发生受几个参数的控制，这些参数代表了破坏前后区域的变形特性。

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.