Study On Tunneling And Quality Control Trchnology Of Long Distance Shield Tunnel With Small Radius

With the rapid development of modern construction and manufacturing technology,shield construction technology and experience are becoming more and more mature.However,due to the continuous development and application of urban underground space,the selection of rail transit lines is restricted by the planning and surrounding buildings(structures),the line type is more and more complex,and the shield construction environment is more and more harsh.So fast,a large number of subway construction,it is inevitable to encounter thorny engineering problems.For example,in the Civil Engineering Standard 3 of Chengdu Rail Transportation Line 9 Phase I Project,during the tunneling process of nearly 10 km under complex conditions such as mudstone composite stratum,37.5‰ long longitudinal slope and 310 m minimum radius curve,the engineering cases of frequently occurring segment floating,wrong platform and quality defects are very rare.In this paper,the relevant research is carried out on the background of this shield tunneling interval project,and the main research contents and results are as follows:(1)Considering the construction conditions such as grouting replacement layer,Jack thrust and shield tail clearance,the finite element analysis models of shield tunneling in straight flat slope section,large slope section and small curve radius section are established,and the stress characteristics of shield tunnel segment lining and the construction mechanical response law of surface settlement under different construction conditions such as different slope and curve radius are revealed.(2)Based on the systematic analysis of the influencing factors of segment floating,the theoretical models of slurry diffusion in different grouting environments are proposed,and the corresponding calculation methods of dynamic buoyancy are derived;Considering the buoyancy effect,joint anti floating effect(bolt shear anti floating,joint friction anti floating)and overlying soil anti floating effect,two kinds of local anti floating computational mechanics models of single segment dislocation and integral segment dislocation are proposed.According to the shear failure condition of joint bolt,the critical control values of grouting pressure under two kinds of local dislocation failure modes are obtained.(3)Based on the longitudinal stiffness reduction theory of shield tunnel,the finite element analysis model of longitudinal integral buoyancy of shield tunnel is established.The influence of longitudinal stiffness of segment lining structure and dynamic and static buoyancy factors on the long-distance and large-scale buoyancy deflection of shield tunnel is explored,and the results are compared with the field measured buoyancy.(4)The damage plastic constitutive model of concrete in ABAQUS is introduced to establish the finite element analysis model of lining segment under different construction conditions.The stress characteristics and damage behavior of lining segment under bad jacking force are revealed.The research results can guide the control of Jack thrust in shield tunneling,at the same time,the comparative study on the mechanical damage characteristics of concrete with different strength grades can provide reference for the important parameters of segment design.