Research on Construction Technology of Large Cross Section Special-Shaped Shield Passing through Upper Soft&Lower Hard Strata
Based on a special-shaped shield tunnel section project of Ningbo Rail Transit,the construction technology control measures such as soil improvement in the construction of large section special-shaped shield in the upper soft and lower hard cohesive soil layer were studied.Combined with the problems of poor liquidity of soil bunker and poor soil discharge in the previous special-shaped shield construction,the soil improvement measures were optimized and adjusted in three stages during the construction.It was found that the addition of foam modifier can effectively eliminate the impact of the cutting blind area of the special-shaped shield cutter head and the adverse soil layer on the excavation,effectively reduce the total thrust and cutter head torque,and improve the excavation speed.Soil improvement through a small number of improvement holes at key points(blind area&cutterhead)can effectively enhance the effect of soil improvement while controlling the amount of modifiers such as foam,and significantly improve work efficiency.
large sectionspecial-shaped shieldsoil improvementwork efficiency
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