Abstract: Rockburst has a significant effect on the safety and speed of constructing deepburied tunnels such as the SichuanTibet railway tunnel project using a tunnel boring machine (TBM). This is a technical difficulty and needs to be resolved. Accordingly, tunnels with burial depths of over 2 000 m, such as the Hanjiang RiverWeihe River water conveyance project, the ABH project in Xinjiang, and the Jinping Ⅱ hydropower project, are taken as case studies. Based on the analysis of mass field data and the characteristics of the TBM structure and construction method, the following points of investigation are proposed: (1) the effects of safety and speed and the spatiotemporal characteristic laws of rockburst on TBM construction; (2) prevention and control targets of TBM construction corresponding to three grades of rockburst (slight, medium, and strong); (3) guidelines for rockburst prevention and control, including advanced speed control, risk control, spatiotemporal control, and hierarchical control; (4) technical solutions for the prevention and control of the three grades of rockburst. In this way, a hierarchical rockburst prevention and control system with coordinated "equipmentboringsupport" is established and applied (theoretically and experimentally) to engineering practices. Results reveal the following: (1) Compared with the TBM boring speed under no rockburst, the boring speed under slight rockburst is lower by 10%~30%, that under medium rockburst is lower by 30%~50%, and that under strong rockburst is lower by 50%~75%. (2) Approximately 20%~40% of rockburst phenomena occur within 10 h after excavation; the highest rockburst frequency is within 10~24 h, with over 90% of rockburst phenomena occurring within 24 h and approximately 9% of strong rockburst phenomena occurring within 24~48 h. (3) Over 30% of medium rockburst phenomena occur within the area between the shield body and tunnel face. Over 90% of medium and strong rockburst phenomena occur in the area 15 m behind the tunnel face. (4) Approximately 80%~90% of strong rockburst phenomena can be controlled to occur in the area between the TBM shield body and tunnel face by controlling the TBM advancing speed. The proposed technical solutions were successfully applied to the ABH project in the Xinjiang and Hanjiang RiverWeihe River water conveyance project, and good effects such as successful passage through the rockburst section and high TBM construction efficiency were achieved.

Key words: deep buried tunnel, Sichuan Tibet railway tunnel, TBM construction, rockburst characteristics; rockburst prevention and control