Finite Element Analysis of the Influencing Factors on the Floating of Shield Tunnel Segments in Soft Soil Strata
This study examines the impact of shield tunneling excavation speed and slurry solidification time on the buoyancy of tunnel segments,focusing on the section between Tongyuan Road Station and Xinggang Street Station on Suzhou Metro Line 5.A three-dimensional finite element model of shield tunnel segments was developed using Winkler elastic foundation beams,considering the dynamic and static buoyancy effects generated by synchronous and secondary grouting on the pipe segments.The analysis assessed how excavation speed and grouting solidification time influence the uplift and misalignment of the segments.Results showed that both uplift and misalignment increased with higher tunneling speeds.The upward floating problem mainly occurs at the bottom of the pipe segment in the nonsolidified section of the slurry,whereas the misalignment mainly occurs at the junction between the nonsolidified section and the shield tail section,as well as between the nonsolidified section and the solidified section of the slurry.To avoid floating and misalignment of the pipe segments from exceeding the specification requirements,the excavation speed of the shield machine should not exceed 10 rings per day.Furthermore,it was observed that as the solidification time of the slurry increased,the amount of floating and misalignment of the tunnel segments gradually increased.Therefore,the use of a fast-setting and early strength dual liquid slurry is beneficial for controlling the floating of shield tunnels.
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