To investigate the effect of various intermediate principal stresses on rockburst incubation and failure during tangential stress gradient loading

a series of true triaxial rockburst model experiments on quasi-rock material specimens under three intermediate principal stress conditions was conducted using a self-developed gas-liquid combined loading apparatus. A high-speed camera and an acoustic emission monitoring system recorded the test data. This paper compared and analyzed the macroscopic failure differences of the specimens and the evolution characteristics of acoustic emission parameters. The results indicate that the failure load

instantaneous burst intensity of rockburst

total mass of rockburst debris

mass of debris of each particle size

and scale of specimen failure increase with higher intermediate principal stress. During loading

specimens under high intermediate principal stress show weakened acoustic emission activity in the early and middle stages

revealing that the high intermediate principal stress suppresses the damage and crack development. In the later stages

the acoustic emission ringing count and energy release of the specimens under high intermediate principal stress become more concentrated

and the energy peak and cumulative values increase. The acoustic emission b-value drops sharply to a lower level

and the proportion of high main frequency amplitude points increases

indicating that high intermediate principal stress exacerbates the damage and crack development. The number of large-scale and shear cracks increases

leading to more violent instantaneous energy release

more severe failure

and higher intensity of rockburst.