During the construction of subway shields, the problem of floating segments is particularly prominent in silty clay strata. The resulting segment problems, such as cross-platform, cracks, damage and leakage, cause great harm to the tunnel. Through field test, combined with mathematical theory and numerical simulation analysis, this paper studies the floating law of segments in water rich sandy silt and muddy clay layer, which provides a basis for analysing the control measures of segment floating, which can improve the safety of the project and save the project cost. The typical section of shield tunnel of Hangzhou Metro Line 7 is selected as the test section, and the segment floating law is deeply analysed through field test. By combining numerical simulation and theoretical research, the mechanism underlying the effects of the grouting slurry properties, the main physical parameters of the soil and the distance of the segment from the shield tail on segment floating is discussed. The results show that shield segments floating in muddy clay strata can be divided into three typical stages: rapid change, buffering and stability. In the first stage, segment up-floating develops rapidly, accounting for 70–90% of the total up-floating within 15 hours after leaving the shield tail. In the second stage, buffer up-floating develops slowly, and the average up-floating amount accounts for 7.59% of the total amount of up-floating. In the third stage, segment up-floating gradually stops with the condensation and hardening of the slurry. The results show that there is a negative correlation between the slurry condensation rate and the number of floating segments, a negative correlation between the segment distance from the shield tail and the number of floating segments, and a positive correlation between the elastic modulus of the soil and the number of floating segments. The multifactor calculation model is proven to have good adaptability in silty soft soil layers.
Study on the Floating Law of Metro Segments in Water-Rich Sandy Silt and Silty Clay Strata
KSCE J Civ Eng
KSCE Journal of Civil Engineering ; 26 , 6 ; 2979-2991
2022-06-01
13 pages
Article (Journal)
Electronic Resource
English
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