Investigation on Acoustic Emission Characteristics of Hole-Joint Contained Granite under a Compressive Disturbance: Experimental Insights

Abstract

Uniaxial compression experiments were performed in cross-jointed granite samples with a hole, together with acoustic emission (AE) observations, to investigate AE variability and precursory information during sample failure. The variability characteristics of multiple AE time-series parameters (including AE counts, accumulated counts, energy, accumulated energy, and b-value) and frequency domain parameters (including AE frequency and amplitude) were systematically analyzed, the variations in different parameters and precursor characteristics were compared, and the AE parameters suitable for rock failure prediction in a cavern were discussed. The results indicate that the variability characteristics of different AE parameters are different, and each parameter has a precursor phenomenon of specimen fracture. The peak value of specimen AE counts does not necessarily appear at the peak stress, but the AE counts decrease significantly when the samples are damaged. The accumulated AE count curve makes it easier to identify the precursors of sample failure. The AE energy is released at an accelerated speed when the samples are near complete failure, and a critical energy release exists in the samples. The abrupt increase in AE energy has potential as a precursor to sample failure. The b-value shows a fluctuating decline during the whole loading process and a rapid decline before sample failure. The low-frequency with high-amplitude and the high-frequency with low-amplitude signals exhibit distinct characteristics at different specimen deformation stages and are sensitive to the change in specimen stress state, so they can be used as the crucial signal source for predicting specimen failure. The joint analysis of these AE parameters can better capture the precursory information of rock failure.