Numerical Study On Seismic Response Of Undersea Immersed Tunnel

Due to the superiority of the immersed tunnel as the transport across the sea and river,its construction scale is constantly expanding.Immersed tunnels often involve issues such as the interaction between seawater and segments,and the stability of joints,Moreover,due to the complexity and instability of underwater environment,once the immersed tunnel structure is destroyed,the consequences will be catastrophic.At present,the 2D finite element model is mostly used to study the seismic response of seawater-immersed tunnel-seabed.However,the 2D plane finite element model can't reflect the longitudinal seismic characteristics of the tunnel,and this model can't consider the impact of weak joints of the immersed tunnel.This paper mainly uses numerical simulation methods to study the seismic responses of immersed tunnels and the influence of relevant factors.The main work is as follows:(1)The artificial viscoelastic boundary which suitable for the dynamic calculation of underground structures was set up by ABAQUS finite element software and the input of the seismic equivalent load was finished using the subroutines.Through numerical examples,the correctness of the artificial boundary and the input method of seismic load are verified.(2)In order to study the influence of seismic coupled seawater on the immersed tunnels,the simulation method of ABAQUS for water was compared and analyzed.The subroutine UEL was used to add a layer of user elements to the surface of the immersed tunnel system.By endowing the element quality,the hydrodynamic pressure of the seawater on the immersed tunnel under earthquake was finished.(3)Taking the Dalian Bay immersed tunnel as the research background,a three-dimensional finite element model of seawater,immersed tunnel segments,joints and surrounding soil was established,and the seismic response of the immersed tunnel under the effect of lateral ground motion were studied.(4)The influences of seismic waves,peaks acceleration,buried depths and seawater levels on the immersed tunnels are calculated.This paper focusing on the analysis of the seismic response of displacement,acceleration and principal stress of the tunnel,and the dynamic response law in the longitudinal and transverse of the immersed tunnel was summarized.