Optimization Of Segment Parameter Design For Shield Tunnel

Segment is not only the lining part of shield tunnel,but also the most important structure of shield tunnel.According to different practical needs,it can be constructed by corresponding prefabricated modules in order to design different segments.The design of pipe piece is related to the safety of subway construction and operation,but the existing design mostly adopts the experience method,the design parameters of the pipe piece are relatively conservative,resulting in a large amount of safety surplus of force and deformation,thus increasing the production cost.It caused a waste of resources.In view of this,combined with the Foshan Metro Line 2 through River Tunnel Project,this paper makes a deep research and analysis on the force mechanism of the pipe segments,and at the same time makes a decision on the optimum design of some parameters in order to provide the key technical support for the optimization design of the segments.The following are the main contents of this paper:(1)in order to study the load acting mode of shield tunnel in soft clay subway with rich water,and establish the accurate calculation and simulation model,firstly,the field test of the tunnel through river shield in Foshan Metro Line 2 has been carried out.The soil pressure and axial force of shield segment are measured.Secondly,the shell-spring model is used to simulate the segments.Finally,the results of field test and numerical calculation are compared,the boundary setting conditions of the shell-spring model are modified by feedback,and the existence of water pressure around the segments is clarified.After modification,the accuracy of numerical simulation results is improved,and the calculation model of subsequent parameterized modeling script is determined.(2)in order to study the influence of different structural parameters on the internal force of segments,numerical simulation is used to analyze them.Firstly,the finite element modeling is complicated and the manual process is expensive.The parameterized internal force calculation script based on shell-spring model is designed to calculate the internal force of shield segment,and the analysis efficiency is improved.Secondly,based on the script,the force condition of the segment under different structural parameters is calculated.The influence of different structural parameters on the internal force and deformation of segments is analyzed and summarized.It is found that the thickness and width of segments are positively correlated with the axial force,and negatively correlated with the deformation,while the thickness of segments is just the opposite.(3)to optimize the geometric structure parameters of segment,firstly,a multi-objective optimization mathematical model based on radial basis agent model for shield segment is established,and the radius of segment r,the width of segment w and the thickness of segment h are selected as the design variables.The maximum axial force,the maximum deformation and the quality of the segment are multi-objective optimization.Secondly,the seven-star ladybug optimization algorithm SLO is used to optimize the multi-objective proxy model,and a set of optimal structural parameters are obtained.The results show that after optimization,the mass decreases by 16%,the maximum deformation decreases by 18.5%,and the maximum axial force decreases by 9% compared with that before optimization.