Frequency-domain characteristics of acoustic signals of granite under uniaxial compression

Instabilities that have the potential to cause rock failures are serious engineering problems that can lead to geological disasters. In this study, a uniaxial compression acoustic test is conducted to explore the precursors of instability failures in granite, and the evolution characteristics of the accompanying acoustic emission (AE) and infrasound signals are evaluated in the frequency domain. The experimental results show that the AE events below 100 kHz decrease gradually before the peak failure of granite specimens, while the AE events above 250 kHz increase gradually. The average frequency centroid of rock specimens undergoes a "relative rising period" and a "relative stable period" before the peak failure, which occurrs during the relative stable period. The dominant frequencies between 5 to 15 Hz of infrasound signals are about 62.5% of the total on average. When the relative stress level before the point of peak stress is more than 80%, the infrasound signal proportion in the first and third frequency bands is at its lowest, whereas the proportion in the second frequency band is at its highest. Finally, the dominant frequency of infrasound signal in the process of granite deformation and failure is fractal-processed, and it is found that the fractal dimension of the dominant frequency of infrasound signal decreases to the minimum value before the peak stress. The above characteristics of acoustic signal before the peak stress can be regarded as the precursory features of the critical failure.