| With the development of urban construction and the development of underground space,large scale underwater shield tunnels are developing in the direction of overlength, large section, high water pressure and complicated geological conditions, this puts forward higher requirements and challenges for seismic study of shield tunnel. However,in the past,it was generally considered that the underground structure was constrained by the surrounding soil,so it was difficult to be affected by the earthquake disaster. Therefore, the seismic research of underground structure seriously fall behind the ground structure. As an important part of underground structures,the shield tunnel is relatively few in seismic research,and large shield tunnel structure systems have not really withstood the test of strong earthquake action. In order to ensure the safety of large shield tunnel in high intensity area, it is necessary to explore new and effective measures for earthquake resistance and shock absorption.This paper is based on the project of a large underwater shield tunnel,combines with the longitudinal earthquake resistance of shield tunnel theory,builds a finite element model which can reflect the overall longitudinal stress characteristics of shield tunnels,analysis the dynamic response of structures under earthquake action.In view of the change of longitudinal soil layer along the tunnel,the opening of the ring joint exceeds the waterproof limit,proposes a dumbbell shape memory alloy (SMA)with flexible shock absorber node, Arranges it in the weak position of the shield tunnel pipe ring, and carries out a series of mechanical properties tests of different SMA materials, discusses the feasibility of SMA flexible damping joint used in tunnel.The specific research contents are as follows:(1) Sums up and summarizes the common analysis models and analysis methods of the longitudinal seismic calculation of shield tunnel,compares with the characteristics and conditions of shield tunnel, selectes the suitable analysis models and methods which suitable for this project ; Secondly, introduces the methods of determining the parameters and the theory of seismic wave ;Finally, discusses the ANSYS/LS-DYNA which reflects the boundary theory, concludes that the non-reflecting boundary is a artificial boundary which has good effects of absorbing energy and preventing reflection of boundary .The purpose of this paper is to provide the oretical guidance and basis for the whole longitudinal seismic calculation of shield tunnel.(2) Relies on a large underwater shield tunnel project,bases on the theory of beam-spring model which is widely used in Civil Engineering, using ABAQUS software,builds the whole longitudinal finite element model of shield tunnel;Secondly, Bases on the non-reflecting boundary theory, Using ANSYS/LS-DYNA software, builds the three dimensional finite element models of soil in tunnel,analyzes the displacement time history response of soil, gives the displacement response to the longitudinal beam-spring model of shield tunnel by the stratum spring; At last,analyzes the whole longitudinal seismic response of shield tunnel under different seismic waves.(3) Bases on the existing seismic measures, combines with the advantages of good elasticity and self-reset energy of SMA,introduces to set the SMA flexible damping node in the weak position of shield tunnel,analyzes of the damping mechanism of different flexible joints, testes on the related flexible damping node of SMA, comparative analyzes the mechanical properties of SMA in different forms, demonstrates the feasibility of flexible joints using in the shield tunnel; Finally,screenes SMA flexible damping node to meet the requirements of engineering. To provide reference and basis for the exploration of energy dissipation devices which suitable for engineering. |
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