Fine Numerical Simulation And Multi-scale Mechanical Comparative Analysis Of Segment Joint In Shield Tunnel

Subway is developing rapidly with the growth of population,the increase of traffic pressure and the improvement of economic.The safety of subway structure is being paid more and more attention.Subway tunnel takes segments as main support structure,segments are connected by segment joints,which are the weak part of tunnel lining.At present,joint with bolts are commonly used,which are easy to appear cracks,falling blocks,leakage and other diseases in the process of use,affecting the safety and durability of the tunnel structure.The main reasons include the lack of mechanical analysis and the own deficiencies of bolt joint.Exploring mechanical properties of joints and utilizing new joints are both effective means to solve the problem.In this paper,two kinds of traditional joints(straight bolt joint,bent bolt joint)and one kind of new joint(slide-in quick joint)were used as the research objects.Finite-element method was used to build fine 3D solid models of three kinds of segment joints.The reliability of numerical models was verified by model test results.Based on the numerical model,mechanical responses and properties under bending moment,shear force and axial load were analyzed from three scales witch include joint details,joint structure and tunnel lining ring.The research also contains differences,relations and application range of these three kind of joints.The results of this paper are as follows:(1)The numerical models of flexural analysis of three kinds of joints are established.According to model analysis,the axial load can linearly improve the flexural performance of joints.The flexural performance between two traditional joints are basically the same.During loading period,traditional joints experience four stress stages and show good ductility.The flexural performance of slide-in quick joint is better than that of traditional bolt joint.There are three stages when slide-in quick joint is subjected to positive flexural load,and two stages when it is subjected to negative flexural load.T-connector and C-groove are the weak part of slide-in quick joint.(2)The research on optimization of slide-in quick joint was carried out in terms of the joint structure and material.It is found that moving the connector to compression side can improve structural ductility without changing joint flexural stiffness.Moving the connector to tensile side can improve joint flexural stiffness and reduce joint deformation.When material grade of the connector is increased,deformation performance of the joint will not be significantly changed,but flexural stiffness of the joint can be improved.Both too high and too low grade of connector material will lead to a increase of concrete stress.(3)Numerical models for shear analysis of three kinds of joints are established.According to the model analysis,the joint shear process is mainly divided into two stages.Axial load can linearly improve shear performance of the joint.Shear performance of the connector determines shear performance of the joint.Shear properties of straight bolt and bent bolt joints are basically the same.Shear performance of the slide-in quick joint is much better than that of the bolt joints.Weaknesses of slide-in quick couplings are located in T-type,C-type connectors and C-type grooves.(4)Numerical models for full-ring lining structure analysis of three kinds of joints are established.According to the model analysis,the deformation of the lining ring is in the form of "transverse duck egg".#2 join is the weak link of tunnel deformation,and the #1 and #2joints are the weak link of tunnel stress.Mechanical changes of the joints at each position of lining ring will affect overall stiffness of the tunnel and stiffness of each joint.There is a stable multiple relationship between joint opening at each position and tunnel lateral deformation,so the information of joint opening can be inferred from tunnel lateral deformation monitoring.Bearing capacity and anti-deformation ability of lining ring with traditional bolt joints are basically the same.Straight bolt joint is slightly stronger than the bent bolt joint.In the loading process,there are leakage risks in every position of traditional bolt joint.Load-bearing capacity and anti-deformation ability of slide-in quick joint are obviously stronger than that of traditional bolt joint.Slide-in quick joint can bear a larger load than traditional bolt joint,only the 2# joint of slide-in quick joint has the risk of leakage.(5)According to the analysis results of joint load test and the whole ring load test,it is concluded that traditional bolt joint is suitable for the tunnel with low ground stress,and slidein quick joint is suitable for the tunnel with high ground stress and high deformation control requirements.