Study on the Combined Reinforcement of Silt Stratum in Large Longitudinal Slope Shield Tunnel
In order to solve the control problems of stratum deformation and segment floating deformation when the shield tunnel with large slope passes through the silt stratum,relying on the Pazhou branch line of the new intercity railway in the Pearl River Delta,this paper creatively adopts the combination of portal frame and cement-soil reinforcement method to control the deformation of weak stratum and segment floating.Through the numerical simulation of the combination of portal frame and cement-soil reinforcement method,the change law of vertical displacement and segment floating at different positions of the shield excavation surface distance from the research section is analyzed,and the measured values of the field monitoring are compared with the numerical simulation results.The results show that:(1)under the combination of portal frame and cement-soil reinforcement method,before the shield machine reaches the research section where the 20th ring pipe piece is located,the surface at the research section first rises slightly and then rises continuously.When the shield excavation surface reaches the research section,the surface uplift value is about 1.5 mm,and the final surface uplift is controlled within 3.5 mm.(2)Under the combination of portal frame and cement-soil reinforcement method,the segment floating mainly includes four stages:rapid rising,slow rising,slow descending and leveling off.The final floating of segment is controlled at about 50 mm.
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