Acoustic emission characteristics and failure mode analysis of rock failure under complex stress state

Abstract

To study the acoustic characteristics and failure mode of the rock failure process under a complex stress state, acoustic emission (AE) monitoring technology was employed to collect the AE signals in the Brazilian indirect tension test (BITT), uniaxial compression test (UCT), and triaxial compression test (TCT) of yellow sandstone. Moreover, the evolution of AE parameters as well as the characteristics of failure mode during the failure process were analyzed. The results reveal that the peak value of AE b decreases to its lowest point before the peak stress, and the decrease in b corresponds to the sudden increase in AE energy. The peak frequency is primarily distributed in the 0–100 kHz and 200–300 kHz frequency band in BITT. It is primarily distributed in 0–100 kHz and 200–300 kHz band for UCT. The 100–200 kHz band dominates in TCT. The parameter analysis of RA (rise time/amplitude) and AF (AE counts/duration) values for classifying different cracking modes during loading reveal that the highest proportion of tensile events in BITT occurs in the failure stage near the peak stress. Tensile events dominate before the peak stress of UCT, and the proportion of shear events will increase in peak and post-peak stress. The peak value of the proportion of shear events in TCT appears in the range near the peak stress. Moreover, the classification results of the cracking modes coincide with the macrocracks. The research results can provide some reference for the study of the failure process of complex stress rock.