Analytical Analysis Of Seismic Response Of Underwater Tunnel Considering Of Water-saturated Soil-structure Dynamic Interaction

With the development and utilization of rivers,lakes and sea resources,the number of underwater tunnels is gradually increasing.Due to the frequent occurrence of undersea earthquakes,these undersea tunnels are facing the threat of earthquake damage at anytime.Therefore,studying the seismic response mechanism of underwater tunnels provides theoretical support for the seismic and damping design of underwater tunnels,which has important theoretical significance.This article is based on the National Key Basic Research Development Plan(973Plan)Project"Basic Research On the Safety of Long and Large Shield Tunnels with High Water Pressure across the River and Sea"(2015CB057800)topic 5"Deepwater long-line shield tunnel seismic dynamic response mechanism"and National Natural Science"Research on Complicated Local Site Fluctuations Considering the Porous and Multiphase of Soil"(51378058),using analytical methods to systematically study the seismic response laws of underwater tunnels under different conditions,revealing the dynamics of the water-soil-structure system under the action of earthquakes The fluid-solid coupling mechanism,and the research results provide theoretical support for the seismic design of underwater tunnels.The main research contents are as follows in this paper:1.Establish an underwater tunnel seismic response analysis model that can consider the dynamic interaction of seawater-saturated soil-structure.The seawater layer and seabed soil layer are regarded as ideal fluid media and saturated porous media,respectively,based on ideal fluid wave theory and Biot fluid saturation wave theory of porous media,the wave function expansion method and the Hankel function integral transformation method are used to derive the analytical solutions to the plane wave scattering problem of the underwater tunnel under different conditions.Including:(1)Analytical solution to the plane P₁ waves and SV waves scattering by underwater unlined tunnels;(2)Considering the two contact conditions between the seabed soil and the tunnel lining,perfect contact or imperfect contact,analytical solution to the plane P₁waves and SV waves scattering by underwater lined tunnels;(3)In combination with engineering practice,underwater tunnels often use double lining to build the underwater analytical solution to the plane P₁ waves and SV waves scattering by a double linging tunnel.2.Considering the topographic effect of the undersea shallow trench,the analytical solution to the plane P₁ waves and SV waves scattering of undersea lining tunnels is established.3.On the basis of the analytical solution,the dynamic stress concentration coefficient,pore pressure concentration coefficient and site displacement of the underwater tunnel in frequency domain are obtained.In this paper,the influence of factors such as incident wave characteristics(incident angle,incident frequency),tunnel site characteristics(water depth,buried depth,and porosity)and tunnel structure characteristics(lining stiffness,lining thickness,saturated soil-tunnel contact conditions)on the seismic response of underwater tunnels under different conditions is analyzed,and the mechanism of underwater tunnel seismic response is explored.The research results show that:(1)the site displacement and dynamic stress concentration factor under impermeable condition of unlined tunnels are greater than that under permeable condition;(2)the site displacement of the underwater tunnel with imperfect contact under the incidence of P₁ waves is greater than that with perfect contact,and the site displacement of an underwater tunnel with imperfect contact under high frequency incidence of SV waves is smaller than that of a subsea tunnel without a slip interface;(3)the influence of the water depth change under the incidence of P₁ waves on the displacement is related to the frequency,and the change of water depth under the incidence of SV waves is incident has little effect on site displacement;(4)the change of water depth under the incident of SV wave has little effect on the pore pressure factor coefficient and dynamic stress concentration factor of the tunnel beneath the shallow trench;(5)the seismic response of the underwater double lining tunnel is significantly smaller than that with perfect contact.