Acoustic emission space-time evolution rules and failure precursors of granite under uniaxial compression

To obtain the acoustic emission (AE) space-time evolution characteristics and energy releasing laws during process of rock failure, uniaxial compression tests are carried out by using MTS815 rock mechanics test system and PCI-2 AE system. The test results show that the evolution process of AE time series parameters under uniaxial compression can be divided into 3 stages, including the rising period, quiet period and fluctuation period. The spatial distribution and accurate localization of AE signal source may correspond to the stress concentration and seriously macro-fractured areas of rock. With the increase of stress, AE events are transformed into high-energy and large-crack events from low-energy and micro-crack events, which implies that the micro-cracks are developed into macro-fractures, the specimen is completely destroyed, and most of the energy is released. Based on the characteristics of space-time evolution, the AE quiet period, AE energy rate, AE ring count rate and rock dilatancy can be used to predict the rock damage. The AE energy rate and AE ring count rate are the most sensitive indexes to predict the failure of rocks. Then the followed AE quiet period and rock dilatancy occur. This study may provide some guidance for the monitoring and prediction of rock stability for underground powerhouses in high stress regions.