Dynamic Response Investigation On Subsea Immersed Tunnel Under Seismic Wave Oblique Incidence

With the development of economy and modern transportation construction in our country,many large-scale subsea tunnels,such as cross-channel project over Qiongzhou strait and Hongkong-Zhuhai-Macao immersed tube tunnel project have been built or under construction planning.There may exist some high seismic intensity areas in which these engineering are built,so sufficient attention has to been paid to the investigation on their seismic behaviors.Nowadays,in the research on seismic behavior of subsea tunnel structure,dynamic response analysis is often conducted with the normal incidence of seismic wave.However,this assumption of incidence manner isn’t coincident with reality,and may cause non-ignorable error.On the other hand,generally the influence of sea water has not been taken into account,or actual engineering condition can’t be reflected even if sea water has been considered.Therefore,taking the incidence of seismic wave and sea water into account can reflect the damage mechanism of immersed tunnel structure and has real engineering significance.In this paper,based on the viscoelasticity artificial boundary and FE-combined wave analysis method,sea water-immersed tunnel-seabed overall FE model is established,with the fluid-solid coupling dynamic response of sea water and seabed.Influence factors on the dynamic response of immersed tunnel,such as seismic wave oblique incidence,sea water depth,embedment depth of immersed tunnel structure and elasticity modulus of seabed soil,are studied.The main research contents are as follows:Firstly,based on the viscoelasticity artificial boundary and external source wave input method,artificial boundary nodes equivalent load calculation method under 2D seismic oblique incidence is established.Equivalent seismic nodes load program has been compiled by using Matlab,and verified through numerical example.Besides,based on the sea water-immersed tunnel-seabed overall FE model,influence degree and law of factors,such as sea water depth,embedment depth of immersed tunnel structure and elasticity modulus of seabed soil,on the dynamic response of immersed tunnel under seismic P wave normal incidence are studied.Then the dynamic response characteristics of immersed tunnel structure under different incidence angles of seismic P wave is investigated.Discussion on the influence of the sea water depth,embedment depth of immersed tunnel structure and elasticity modulus of seabed soil on the dynamic response of immersed tunnel is conducted.Comparing with the impact of normal incidence of seismic P wave,these factors have the same influence tendency while the influence degrees are different.Other useful conclusions are also presented.Finally,dynamic response of immersed tunnel under different incidence angels of seismic SV wave is studied.Discussion on the influence of the sea water depth,embedment depth of immersed tunnel structure and elasticity modulus of seabed soil on the dynamic response of immersed tunnel is conducted.In this paper,seismic response of undersea immersed tunnel is investigated,and dynamic response characteristic of immersed tunnel is explained reasonably,which can provide reference in terms of the seismic design of immersed tunnel structure.