| With the continuous increase of urban subway lines,there are more and more projects for shield tunnels to pass through pile foundations such as houses and bridges,and the shield construction environment is becoming more and more complicated.Therefore,it is of great significance to carry out the construction of shield tunnels for the study of the influence of existing pile foundations.In this paper,the previous studies are summarized and summarized.Based on the actual engineering background,the combination of field measurement,numerical simulation and theoretical analysis is used to study the influence of shield tunnel construction on the adjacent pile foundation in Zhengzhou silt layer.The main research contents of this paper are as follows:(1)Through the on-site measurement of the influence of shield construction on the existing high-speed railway piles in the Zhengzhou silt layer,and comparing the surface settlement values of the reinforcement section and the unreinforced section,it shows that the reinforcement measures can reduce the surface settlement by about 28.4%..The vertical displacement of the soil near the high-speed railway bridge pile in the reinforcement section can be divided into the early uplift stage,the sharp settlement stage and the settlement stable stage.The grouting reinforcement range is about 2 times the shield diameter.The maximum settlement of the surface caused by shield construction is 15.9mm,and the maximum settlement of the pier is 0.8mm,which meets the requirements of standard deformation.(2)Based on the parameter inverse algorithm,considering the factors such as the rigidity of the shield shell,the reduction of the segment,the pressure of the grouting,and the solidification process of the grouting layer,etc.,in the Zhengzhou silt layer,the shield construction side wears both high-speed bridge piles.The process was simulated and the reliability of the numerical simulation was verified by field measurements.By comparing the two working conditions of reinforcement and non-reinforcement,the results show that the maximum settlement of the high-speed railway bridge can be reduced by about 72.6% by the construction technology of soil grouting reinforcement,the horizontal displacement,bending moment and side of the pile.The maximum frictional resistance decreased by 58.3%,37.6% and 23.7%,respectively.Therefore,the construction method of first grouting and then crossing can effectively reduce the disturbance of the shield construction to the surrounding environment and protect the safety of the high-speed railway pile.(3)Using the two-stage analysis method,the influence of tunnel excavation on the internal forces and displacement of adjacent single piles and group piles is analyzed.Through the single factor analysis method,the effects of formation loss ratio,pile-pitch spacing,tunnel depth,and pile length-to-fine ratio on the internal forces and deformation of adjacent piles caused by tunnel excavation were studied.The results show that the formation loss ratio is approximately linear with the pile top settlement.The increase of the distance between the pile and the tunnel and the increase of the buried depth of the tunnel can significantly reduce the settlement and axial force of the adjacent pile.The pile-pitch spacing and tunnel depth have a significant impact on the safety of the pile foundation.The change of the slenderness ratio of the pile has little effect on the settlement of the pile caused by the excavation of the shield,but it has a great influence on the axial force of the pile.Based on the research results of this paper,the control measures for the construction of shield tunnels adjacent to existing pile foundations are proposed,in order to provide reference for the design and construction of similar projects. |
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