Physical Simulation Experiment of Granite Rockburst in a Deep-Buried Tunnel in Kangding County, Sichuan Province, China

The deep-buried tunnel planned in Zheduo Mountain, Kangding County, Sichuan Province, is likely to rockburst due to its large buried depth and concentrated tectonic stress. In order to figure out the rockburst failure mechanism under different depths, in this study, the triaxial rockburst physical experiments of the granite in the Zheduo Mountain tunnel at different depths were carried out employing the stress monitoring system, high-speed camera system, and acoustic emission monitoring system. The phase characteristics, time characteristics, failure modes, and crack evolution of the granite in the Zheduo Mountain tunnel at different depths were studied with regard to the sound, light, and force and the experimental results show that the rockburst of Zheduo Mountain granite has obvious characteristics of time delaying rockburst (TDR). 770 m is the critical depth of the granite triaxial strength with one free face, and the lag characteristics of the excavation rockburst around this depth is obviously weakened. Rockburst at different depths can be divided into different stages: quiet period, splitting into plate stage, plate folding and spalling stage, and overall ejection stage. Rockburst acoustic emission characteristics reveal that the rockburst of Zheduo Mountain granite is mainly tensile failure, and with the increase of the depth, the number of tension cracks gradually increases and the number of shear cracks gradually decreases. According to the ratio of the stress difference and the uniaxial compressive strength at the time of the rockburst, the rockburst of Zheduo Mountain granite is divided into three failure modes: small particle ejection failure, rock slab splitting failure and mixed ejection failure, and the greater the stress ratio (σv-σh1)/σc is, the greater the rockburst intensity is. © 2022 China University of Geosciences. All rights reserved.