Fundamental Study for the Application of AE Measurement to Predict Microcracking in Rock

本文对声发射（AE）测量在岩石微裂纹预测中的应用进行了实验研究。通过定位声发射震源，研究了大岛花岗岩单轴压缩蠕变过程中剪胀的局部化特征。结果表明，大岛花岗岩的力学行为受微裂纹局部化控制。在加载至蠕变应力阶段，声发射事件震源在整个试件中是随机分布的。蠕变一开始，声发射震源就会突然迁移并聚集到几个近地表带。声发射事件形成体积浓度。这种迁移和聚集强烈表明，在初级蠕变开始时，膨胀体在局部迅速发展。在初级蠕变结束时，声发射事件开始集中到其中一个簇中，而其他簇的活动逐渐衰减。在最活跃的聚类中，声发射事件本身的聚类导致更多的声发射事件发生在断层之前。该簇的形状为球体，长轴平行于加载轴。地表应变图也证实了震源位置确定的局部剪胀的发展。

An experimental research has been carried out for the application of acoustic emission (AE) measurement to predict microcracking in rock.The localization of dilatancy during creep of Oshima granite under uniaxial compression was investigated by locating hypocenters of AE events. It was found that the mechanical behavior of Oshima granite was controlled by the localization of microcracks. During the loading up to the creep stress, the hypocenters of AE events were randomly distributed throughout the specimen. As soon as the creep began, abrupt migration and clustering of AE hypocenters into several near-surface zones were observed. AE events formed volumetric concentrations. This migration and clustering strongly suggested the rapid localized development of dilatancy at the beginning of the primary creep.By the end of the primary creep, AE events began to concentrate into one of these cluster, while the activity of others gradually decayed. In the most active cluster, clustering of AE events by itself gave rise to more AE events preceding faulting. The shape of this cluster was spheroidal with the long axis parallel to the loading axis. The development of localized dilatancy identified by hypocenter locations was also confirmed by the surface strain mapping.