Research On Ground Movement And Building Deformation Caused By Pipe-roof Pre-construction Method

In the process of rapid urban development,people put forward higher and higher requirements for urban road traffic,and the underground road has become the main way to solve the traffic problems in the urban center of big cities.However,in the process of underground engineering construction,in order to prevent the destruction of adjacent structures and cultural relics in the process of underground engineering construction,underground engineering construction methods have been constantly innovated and improved.Pipe-roof pre-construction method is used for The west Jianning Road channel Project which passes beneath the Yifeng gate.In order to To reveal the influence of Pipe-roof pre-construction method construction process on stratum and adjacent buildings,this paper based on the project by using numerical simulation and theoretical analysis and analytic calculation method makes a deep research in the deformation of walls and gates in the process of structure construction control standards,work shaft and pipe jacking construction and reinforcing scheme.It forms the research rule in the construction process of PPM,which has certain reference significance to the subsequent construction projects using PPM.The main conclusions of this paper are as follows:(1)Based on the existing bearing capacity of Yifeng Gate and ancient city wall,the control standard of foundation pit construction and tunnel construction is put forward.Based on the above prediction curves and numerical simulation,the control standards for settlement and uneven settlement of Yifeng Gate and the settlement control standards of the ancient city wall are established.(2)Based on the Mindlin basic solution,the analytical solution of the formation deformation in the rectangular pipe jacking process was deduced.Using the Mindlin solution of elasticity under the action of concentrated force in a semi-infinite body,the soil deformation solution under the action of the frontal thrust of rectangular pipe jacking,the friction force on the side of pipe jacking and the influence of the formation loss at any point in the stratum were derived by integral.The six-point Gauss-Legendre numerical integral was used to calculate and solve the solution on the MATLAB platform.The results of the solution are analyzed: the larger the buried depth is,the smaller the surface settlement caused by pipe jacking will be,but the larger the influence range will be.Under the combined action of additional thrust on the front,friction on the side and formation loss,the surface subsidence deformation curve shows uplift in front of excavation,then it sinks sharply,then it gradually rebounds and becomes stable.The most important factors affecting surface subsidence are formation loss,lateral friction and frontal additional thrust.The finite element numerical simulation method is used to analyze the law of ground surface settlement and deformation under different pipe jacking sequence,and it is considered that the construction sequence form top to bottom has the best effect on ground surface settlement control.(3)Based on the numerical simulation of the whole construction process of the working shaft,the deformation range and law of the ground,the supporting structure and the surrounding buildings under the excavation of the working shaft are revealed.The study shows that the soil outside the foundation pit will strengthen obviously when there are buildings,the stiffness of the stratum will increase,and the deformation of the stratum will become smaller under the disturbance.However,the internal force and lateral deformation of the working well envelope will also increase due to the additional load.Under the action of the construction of the pile foundation working shaft of the city gate,the lateral deformation will be produced,which also has a great influence on the bearing capacity of the pile,making the city gate foundation subsidence.During the construction of the ancient city wall,the maximum deformation position is the turning point of the city wall,and the foundation of the inflection point is prone to cracking.Based on the comprehensive analysis of the excavation sequence of the east-west working shaft,the construction sequence of the east-west working shaft is recommended.(4)Based on the numerical simulation results of three reinforcement schemes,the advantages and disadvantages of each kind of reinforcement scheme are clarified.There are three reinforcement measures for three-axis mixing pile reinforcement,drilled grouting pile reinforcement and sleeve-valve-pipe grouting reinforcement.According to the study,grouting reinforcement is easy to cause secondary damage to the ancient city wall,which leads to cracking of the city wall and the deformation control of the city gate is not obvious.The drilled grouting pile has a good effect on deformation control,but it will increase the difficulty of subsequent pipe jacking construction.Therefore,it is recommended to use three-axis mixing pile on both sides of the working shaft and the bottom of the pit for reinforcement.