Experimental study on the evolutionary characteristics of acoustic signals produced by granite damage under uniaxial compression

Acoustic signals emitted during rock fracture constitute an important tool for rock damage evaluation. To investigate the evolutionary characteristics of acoustic emission (AE), microseismic (MS), and sound signals produced by hard rock fracture, uniaxial compression tests on granite specimens observed by AE, MS and sound monitoring were carried out. The evolution characteristics of the acoustic signal index, including its waveform, fractal dimension, b value, main frequency, energy proportion of signal frequency bands, and signal activeness, were analysed. The results indicate that there are significant differences in some characteristics of the AE, MS, and sound on the eve of granite failures, such as the waveform amplitude density, the average decline rate of the b value, the distribution of the main frequency, and the evolution of the energy proportion of the advantage frequency band. The three types of acoustic signals can characterize different scales of rock fracture under uniaxial compression. AE is sensitive to small-scale rock fractures, and MS and sound are sensitive to large-scale rock fractures. In addition, a unified damage evolution equation established by acoustic signals is proposed to quantitatively describe the damage process of granite specimens during uniaxial compression tests.