Influence Of Welding High Temperature And Concrete Pressure Injection On Mechanical Properties Of Shield Tunnel Composite Segment

With the construction of underground space,the development of shield tunnels is moving toward increasing length,increasing buried depth,and diversification of crosssection forms(especially rectangular and similar rectangular cross-sections).These scenes make the soil and water pressure acting on the shield tunnel lining increase sharply,and then produce greater internal forces on the structure.The composite segment has the characteristics of high strength,high rigidity,good ductility and excellent durability,which can better meet the above development trends.During the manufacturing process,due to the high temperature of welding and the effect of concrete injection,it will cause greater residual stress.And deformation,further affecting the bearing capacity,dimensional accuracy,assembly accuracy,waterproof performance and production cost of the segment.This paper adopts the methods of theoretical analysis,numerical simulation and experimental testing.First,the temperature field,stress field and displacement field are verified for plate welding and L-shaped welding;secondly,a three-dimensional numerical model is established using ABAQUS to determine the shear bond Welding was simulated dynamically,and the temperature field distribution,residual stress distribution and deformation characteristics of the characteristic points were analyzed.After that,the welding residual deformation was tested and the welding width,penetration depth,and penetration length parameters of the double ellipsoid heat source were analyzed.The sensitivity is analyzed,and the influence of each parameter is summarized.Then the influence of welding sequence,ambient temperature and restraint conditions on the welding of joint plates is analyzed.Thirdly,a concrete pouring model was established,the load-structure method was used to analyze the stress and deformation of the plates,and the pressure injection analysis for the existence of initial welding defects was carried out.Finally,with a single shear key as the research object,the pull-out performance of the shear key is analyzed to resist the lifting and failure between the steel plate and the concrete.The research results of this paper show that:during the welding of composite tube segments,when welding panels with shear keys,the welding deformation of the component can be reduced by applying the method of anti-deformation.The setting of the support in this paper can significantly improve the control of the deformation.Compared with the welding in the unsupported state,the maximum deformation of the joint plate is reduced by 60.3%,and the maximum deformation of the main truss is reduced by 62.3%;the shape parameters of the welding heat source will directly affect the distribution of the heat flux inside the ellipsoid model,When the heat input is the same,with the increase of each parameter,the temperature peak value of the curve shows a decreasing trend,and the average temperature gradient under the influence of melt width is about 1.4 times that under the influence of penetration depth;the residual stress changes under different welding sequences The law is roughly the same,but the stress peak and stress distribution will change.The maximum deformation in the Joint plate width direction differs by 0.056mm and the maximum deformation in the board thickness direction differs by 0.090mm under the 6 working conditions;the change in ambient temperature is basically linearly related to the change in the peak temperature,The restraint will reduce the welding deformation of the component to a certain extent,but at the same time it may increase the residual stress inside the component.When this restraint is set within the range of 500mm～700mm,the stress distribution in the panel will be more uniform,and it can be welded at the same time.Deformation plays a control role;for components with welding residual stress,residual stress still exists inside the component after injection,but compared with the residual stress field before injection,the original high tensile stress is reduced,and the residual tension and compression The distribution of stress is more uniform.This study provides a reference for the forming process of composite segments and the promotion and application in engineering,which has important engineering practical significance and good application prospects.