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

点击翻译按钮获取中文摘要

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.