Abstract
The stiffness mutation of shield tunnel‐shaft junction makes the tunnel structure affected by the differential displacement and forms a complex spatial effect. Taking the subsea shield tunnel crossing under the Shantou Gulf, China, as a case study, a three‐dimensional finite element global model and a refined local spatial end submodel are established. The nonlinear dynamic behaviors of the seabed soil and concrete, the simulation of the bolt joints between ring segments by using cohesive models and the SMA shape memory alloy flexible joints, and the input ground motions produced by scaling from the high‐level earthquake records are considered in detail. The results show that the shield tunnel spatial end structure increases nonlinearly in response to the increase of seismic motion intensity. The opening width and the deformation between ring segments at the vault and the outside spandrel are larger, and serious seismic damage and stress concentration exist at the conjugate 45° directions of shaft. The seismic responses of the tunnel‐shaft junction subjected to the seismic motions with rich low‐frequency components are much stronger than those of seismic motions with rich high‐frequency components. Adding SMA flexible joints, the structural deformation caused by seismic motion propagation can be induced to the preset flexible joint, and the structural damage and stress concentration can be effectively reduced. The seismic response characteristics of shield tunnel spatial end structure calculated by the global model are consistent with those calculated by the submodel, while the seismic response of the submodel is greater than that of the global model.
Highlights
IntroductionMaritime trade is the pulse of the contemporary world economy, and the coastal zone is the link to it. is region concentrates on the vast majority of the population of the modern world, carries the dual functions of economy and life, and has a special significance for the world today. e local coastal zone is frequently scattered with islands, and the maritime traffic between the islands will greatly enhance the carrying capacity of this area
For the seismic direction is perpendicular to the tunnel axial direction [15] and the geological conditions mutation or the tunnel structure changes, it is necessary to establish a threedimensional model for seismic response analysis. rough the earthquake damage investigation of shield tunnel, Koizumi [16] found that the junction between the shaft and the tunnel is prone to damage
Erefore, the flexible joint becomes the weak part of the structure in seismic resistance and should be able to meet the expected seismic deformation requirement
Summary
Maritime trade is the pulse of the contemporary world economy, and the coastal zone is the link to it. is region concentrates on the vast majority of the population of the modern world, carries the dual functions of economy and life, and has a special significance for the world today. e local coastal zone is frequently scattered with islands, and the maritime traffic between the islands will greatly enhance the carrying capacity of this area. Chen et al [24] used the generalized response displacement method based on submodel technology to conduct nonlinear seismic analysis of submarine shield tunnel and studied the opening width between pipe rings under high-level earthquake. Considering seabed dynamic nonlinear characteristics of soil, the shield tunnel longitudinal bolt connection between pipe rings, and the flexible connection between the shield tunnel-shaft junctions, making nonlinear dynamic time-history analysis on the tunnel-shaft junction global model and local spatial end structure submodel, and discussing the influence of the characteristics of the input seismic motions and the shock absorption measures on the spatial end structure, the research results can provide a reference for seismic design of shield tunnel-shaft junction. Submodel technology is used to drive the local model through the results of the global model. e driving variables refer to the variables that constrain the submodel and generally match the results of the global model. e universal submodel technique is based on the nodes, and the corresponding response of the global model is interpolated to the nodes of the submodel by using the response of nodes (including displacement, temperature, or pressure degrees of freedom). e whole calculation process does not need to extract the response quantity of the global model node and input it to the submodel boundary again. e finite element software ABAQUS identifies the relationship between the submodel and global model by using the spatial positions of them and takes the displacement of the corresponding driving subboundary nodes in the global model as the additional boundary condition of the submodel. e displacement of the driving subboundary nodes are functions of time in dynamic analysis
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