| As shield-driven tunnel has the advantages of stable construction period, high safety, small impact on the surrounding environment and wide formation applicability, it is increasingly applied to the construction of urban subway lines. The lining structure assembled by bolts is the main load carrying member in the shield tunnel. When the surrounding environment of shield tunnel affected by external construction impact, the stress state of lining structure would also be changed accordingly. As a result, it may lead to some damages at the joint part, such as excessive joint opening, segment crack, leakage and bolt failure. Currently, the method reinforced by steel plate is widely used to treat the severe damages in shield tunnel, but the study on subsequent bearing performance of the joint after reinforcement is less.The bearing performance of longitudinal joint has a significant impact on the deformation and internal force of lining structure. For this reason, the longitudinal joint 3D model of a shield tunnel reinforced project is established. Through the calculation, the bearing and failure mechanism of longitudinal joint before and after reinforcement are studied. The main works and research results of this paper are as follows.(1) Based on a project of shield tunnel reinforced by steel plates, the 3D numerical test model of the reinforced longitudinal joint is established by using Midas FEA finite element analysis software. This model takes the detailed structures such as rubber gasket, cork rubber gasket, connecting bolt and the contact relationship between different materials into account.(2 According to the variation of joint rotation angle with joint bending moment, the deformation of unreinforced joint is divided into four stages. For each stage, the deformation and force distribution of joint are analyzed in detail. These studies will be the foundation for the later research of subsequent bearing performance after reinforcement.(3) The subsequent performance of reinforced joint is studied respectively under the effect of positive and negative bending moment. Firstly, it is defined that when all expansion bolts between steel plate and segment reach yield, the reinforced joint destruct. Then the failure process and characteristics under the action of bending moment are analyzed in detail. Combined with the deformation results of reinforced and unreinforced joint, the reinforcement effect is proved to be significant. Finally, according to the calculation results of joint deformation and steel plate stress in different early bending moment, the reasonable reinforcement opportunity under the action of the positive and negative bending moment are respectively discussed.(4) Combined with the project characteristics of shield tunnel reinforced by steel plate, the parameters which may affect the reinforcement effect of joint are summarized and analyzed. The results show that the thickness and hoop reinforcement range of steel plate have great impact on the joint stiffness and ultimate bearing capacity after reinforcement. But the strength level of expansion bolt and the friction coefficient between segment and steel plate have small effect on the reinforcement effect. |
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