(1. School of Mechanics and Civil Engineering，China University of Mining and Technology，Beijing 100083，China；2. State Key Laboratory for Geomechanics and Deep Underground Engineering，China University of Mining and Technology，Beijing 100083，China)
Abstract：The frequency-spectrum and time-frequency characteristics of acoustic emission original wave data are analyzed，which are obtained through monitoring strain rockburst test under true triaxial stress state with special characteristics of unloading one side of the specimen suddenly. The micromechanism of rock failure process is analyzed based on the microstructure SEM(scanning electronic microscope) images of Sanya granite samples before and post failure，frequency-spectrum and RA(rise time/amplitude) characteristics of AE waveform obtained during rockburst. When the rock sample is relatively stable，AE waves with the feature of low-amplitude and low-energy are formed，and microcracks slip or split in local zone correspondingly. However，the amplitudes of AE waves increase not only in low-frequency range but also in high-frequency during rockburst，which implies that high energy is releasing and macrocracks in the rock specimen are generated. The RA values increase before rockburst and decrease during rockburst. High RA value is wave generated by tensile cracks and low RA value is wave generated by shear cracks propagation. The test results reveal that many relative high-frequency- low-amplitude waves and low-frequency-high-amplitude waves generated during rockburst are related to transgranulation/cleavage tensile microcracks and intergranular shear macrocracks respectively，which shows the characteristics of high energy releasing and low RA value.
