Experimental study on the failure mechanism of roadway surrounding rock under true triaxial loading: Insights from acoustic emission (AE) characteristics

•The failure characteristics of the surrounding rock are investigated through a true triaxial loading environment.•The spatiotemporal evolution of the surrounding rock damage is analysed through stress and acoustic emission measurements.•The changes in the acoustic emission characteristics of the surrounding rock at different stages of damage are revealed. To investigate the failure behavior of the roadway surrounding rock under varying in-situ stress conditions, a series of small-scale model experiments were carried out using a true triaxial rock testing system, an acoustic emission (AE) monitoring system, and a miniature camera monitoring system. The experiments utilized prefabricated cubic sandstone specimens with through-holes to simulate the stress environment of the circular roadway, analyzing the AE characteristics of the failure process of the surrounding rock. The experimental findings indicated that the failure of surrounding rock can be categorized into four stages: the quiet stage, particle ejection stage, stability failure stage, and collapse stage. As the in-situ stress increased, the sustained stress during the quiet stage was negatively relative to the sustained stress during the particle ejection stage and positively related to the sustained stress during the stability failure stage. Moreover, the dominant AE signals during the particle ejection stage shifted from mid-frequency to high-frequency. In the stability failure stage, the ratio of low- to high-frequency (LF to HF) signals increased, the predominant failure mode transitioned from shear failure to tensile failure, and the fissure growth pattern changed from intermittent bursts to progressive development. Data from the RA (Rise Time/Amplitude) and AF (Average Frequency) analysis indicated that the predominant failure mode of deep roadway surrounding rock was tensile fractures, which intensified with increasing in-situ stress.