Abstract: The unreasonable arrangement of grease holes at the shielded tail is easily to cause serious wearing of the tail brush at areas with too large spacing, resulting in fixed slurry leakage locations, which might seriously threaten the safety of shielded tunnel construction. To mitigate for this defect, a construction project case history between the Big Data Station and the Binhai-Xincheng Station in Fuzhou Metro Nearshore Express Line is presented in this paper. Firstly, reasons for the shielded tail improvement as well as the water stop grouting reinforcement before the improvement are introduced in detail. Secondly, different shielded tail on-site improvement alternates are compared from risk, construction duration and cost aspects. The result shows that the alternate of designing a special tail brush and welding with the external hot rolled steel is obviously better than other options. Through the above measures, the shielded tail on-site improvement is successfully completed in a safe and efficient manner under a no-water condition. The new grease holes can normally pump grease into the cavity, greatly improve the safety of the subsequent construction. The relevant experience learned in this project can provide a reference for the subsequent similar projects.

Key words: Improvement of Shielded Tail, Special Tail Brush, WaterRich Sand Strata, Grouting Method