Abstract: Critical risk factors, such as hyperbaric operation, operation under atmospheric pressure, slurry system and shield tail seal, of the construction of Shiziyang tunnel on GuangzhouShenzhenHong Kong passengerdedicated railway are analyzed. Countermeasures and key safety control points are proposed, which eliminates serious injuries and fatal accidents in the tunnel construction. Detailed stipulations on accident prevention and accident coping in construction of superlong underwater shieldbored tunnels are provided. The paper can provide reference for other largediameter underwater shieldbored tunnels in the future. 

Key words: Shiziyang tunnel, largediameter slurry shield, risk factor analysis, risk control