Numerical Simulation Analysis Of Deformation Of Concrete Segments And Contact Characteristics Of Segment Joints

The concrete segment is used as a part of the shield tunnel lining.The mechanical properties of the segment and the segment joint greatly affect the safety and useful life of the project.In order to study the mechanical properties of concrete segments and segment joints,this paper takes several practical projects as the example,by using ANSYS finite element software to establish a three-dimensional fine finite element model of the segment ring structure,study on the contact characteristics of segment and segment joints.The main research contents are as follows:1)In order to study the relationship between the bending stiffness of the segment and the segment joint,first,the effective bending stiffness and bending stiffness ratio of the concrete segment and joint are defined.By referring to the construction parameters of three practical projects,the ratio of effective bending stiffness of the segment joint and the bending stiffness of the segment is calculated and compared.The comparison shows that the ratio between the bending stiffness of segment joint and concrete segment is between 9% and 11%.The ANSYS software are used to establish the equal stiffness ring model and the hinged model.The numerical simulation results show that the distribution and value of the bending moment and shearing force of the segment ring are greatly affected by the existence of the joint.2)Taking the Beijing Metro Line 4 and the Wuhan Yangtze River Tunnel Project as examples,a three-dimensional fine model of the segment ring was established to study the contact characteristics of the segment joint.The research shows that the maximum strain location on tunnel segment concentrates on the location of the bolt hole and the compression zone of the joint.As the amount of seam increases,the joint part changes from the full contact state to larger seam state,the contact stress distribution line gradually changes from the arc line centered on the bolt hole to the straight state,and the maximum stress value gradually increases.The stress value gradually becomes larger.The opening ratio of the segment joints in the two models reached 50% and 75% respectively.3)Taking the Qiongzhou Strait Undersea Tunnel as an example,the ANSYS software was used to establish the combined calculation of water and soil model and separated calculation of water and soil model respectively.The purpose is to study and compare the difference in contact characteristics of segment joints in two different models.The simulation results shows that the maximum strain of the segment and the maximum joint opening in the model of combined calculation of water and soil are 37 and 196 times that of the model of separated calculation of water and soil respectively.In addition,the influence of soil Poisson's ratio on the simulation results is discussed.In addition,the influence of Poisson's ratio of soil on the simulation results is discussed.The joint opening amount gradually decreases with the increase of Poisson's ratio in the combined calculation of water and soil model.When the Poisson's ratio is 0.48,the calculation result is similar to the separated calculation of water and soil model with the Poisson's ratio of 0.40.4)Using the Qiongzhou Strait Undersea Tunnel as an example to establish an analytical model to study the reasons for the large gap between combined calculation of water and soil model and separated calculation of water and soil model.The factors affecting the calculation results of the soil arching effect and the definition of the boundary and external force application modes during modeling are discussed separately.Studies have shown that when the soil physical parameters take a specific value,the soil arching effect can indeed reduce the large overburden pressure in the model,the strain difference decreases but the gap between the joints increases;the definition of the boundary during modeling and the way of applying external force have little effect on the results of combined calculation of water and soil model and separated calculation of water and soil model.The bending moment of the combined calculation of water and soil model can reach 2~5 times of the separated model,and the influence on the axial force is small.5)Taking the Qiongzhou Strait Undersea Tunnel Project as an example,in order to study the relationship between internal force distribution and numerical value between concrete segment and secondary lining,ANSYS software is used to establish a double lining structure model.The simulation results show that the bending moment,shearing force and axial force of the concrete segment are 15.7 times,12.9 times and 1.7 times of the secondary lining respectively.The bending moment,shearing force and axial force of the secondary lining accounted for 5.98%,7.21% and 37.73% of the total bending moment,shearing force and axial force value.The bending moment and shearing force of the secondary lining are less than 10% of the total bending moment and shear force.When the waterproof function of the concrete segment is completely lost,the ground water seeps into the gap between the pipe and the secondary lining,and the water pressure directly acts on the secondary lining,the maximum tensile stress and the maximum compressive stress are both within the tolerable range of concrete.