Abstract: The acoustic emission tests in rockburst process of granite under true-triaxial loading conditions were conducted by using a true-triaxial rockburst test system. It reveals the spatial and temporal evolution characteristics of acoustic emission during rockburst process. At the early stage of rockburst, the count-hits ratio is relatively small, and the dominant frequency is mostly concentrated in low frequency bands. The dominant band, whose energy proportion is the maximum based on wavelet analysis, is characterized as low frequency less than 125 kHz. At this stage, the scattered AE events turn to concentrate, and new AE events migrate gradually from free face to interior of rock specimens. Immediately before rockburst, the count-hits ratio shows a continuous sharp increase, AE signals with high frequency, intermediate frequency and low frequency begin to teem, and the dominant band transfers from discrete state to continuous one. Meanwhile, the proportion of dominant band of 250-500 kHz increases significantly. Simultaneously, away from the free face the nucleation zone of AE events forms, while near the free face the number of AE events increases. During the process of rockburst, the acoustic emission is characterized as low frequency and high amplitude, and it has the dominant band of 62.5-125 kHz. The AE events are active near the free face and the nucleation zone of AE events can be clearly observed in interior of rock specimens, which indicates that the spalling or slabbing occurs near the free face and the macro shear failure occurs away from the free face.

Key words: rock mechanics, rockburst, true-triaxial, acoustic emission