Dynamic Response Analysis Of Underwater Tunnel Under Seismic Effect

With the great strategy of “The Silk Road Economic Belt” and “Maritime Silk Road”,Chinese marine economy has entered the national strategy.Since the development of coastal urban agglomerations,more and more cross-river(sea)tunnels are under construction and planning.In the water environment,the stress and deformation characteristics of the site and tunnel are complicated by many dynamic factors such as site dynamics,seismic load,and seawater that couple to each other.As a lifeline project,tunnels will have catastrophic consequences in the event of damage.In order to reasonably evaluate the stability of underwater tunnel under seismic load,the dynamic response law of tunnel and surrounding soil under earthquake must be explored.Based on the Biot dynamic consolidation theory and the theory of elastic dynamics,and considering the interaction between fluid-soil fluid-structure interaction,an overall finite element analysis model for the water-tunnel-seabed is established in this paper.The model can simulate seawater factors realistically.Then,viscoelastic boundary,potential fluid and other theoretical methods were used to comprehensively consider the hydrodynamic pressure and the two-phase properties of the soil medium to study the distribution law of internal stress in the water tunnel under earthquake and the development law of the excess pore water pressure in the seabed soil.The sensitivity analysis was carried out on the influencing factors such as oblique incidence of ground motion,seabed seepage coefficient,depth of overlying water,and elastic modulus of the tunnel.The main research content is as follows:(1)Detailed expressions of the two-dimensional viscoelastic artificial boundary conditions are derived in detail.According to the wave field decomposition method,the equivalent load of each node on the viscoelastic artificial boundary when P and SV waves are incident at any angle is derived.The self-compiled program verifies the validity of theartificial boundary and the reliability of the ground motion input method through the distribution of internal and external fluctuation input examples.It provides the basis for the numerical analysis of the near-field fluctuation problem.(2)Based on Biot's dynamic consolidation theory and elastic dynamic theory,combined with ADINA potential fluid theory,the fluid infinite boundary,free liquid surface boundary,flow-structure coupling boundary and corresponding pore pressure boundary are set in seawater layer.Water-tunnel-seabed monolithic finite element analysis model.The seismic responses of the water tunnel and its surrounding soil to factors such as the two-phase behavior of soil medium under P wave and SV wave,the oblique incidence of ground motion,the seabed permeability coefficient,the depth of overlying water and the elastic modulus of the tunnel were investigated respectively.Influence the law.