Research On The Dynamic Response Of Seabed Induced By Wave Loadings

When subjected to wave loadings,the decrease of effective stresses and increase of excess pore water pressure in the seabed will cause the seabed to become instable,even to be liquefied.Based on the previous theoretical researches and experiments,this dissertation made further investigations on the dynamic response and liquefaction of seabed using analytical method.The main research contents and results are as follows:1.The current situation and problems of dynamic response of wave propagation in the seabed are briefly descripted.The linear wave theory,fluid-solid coupling and Biot theory are introduced.The theoretical and experimental methods for studying the dynamic response of seabed are summarized.2.The dynamic response and momentary liquefaction of seabed under wave loadings are studied by theoretical analysis.In the process of analysis,the seabed is modelled by using Biot's fully dynamic theory and waves are described by linear wave theory,where the inertia effects and the compressibility of solid and pore fluid are considered and the flow in the porous seabed is assumed to be governed by Darcy's law.Based on the appropriate boundary conditions,the solutions for the pore water pressure,effective stresses and displacements are obtained for seabed of finite or infinite thickness.A parametric study is performed to analyse the effects on the dynamic response and liquefaction depth of seabed,including wave period,water depth,pore fluid compressibility,soil permeability,shear modulus,Poisson's ratio and seabed thickness,etc.3.Considering the anisotropy of the seabed,the analytical solution of the wave-induced dynamic response of an anisotropic seabed under wave loadings is achieved in this paper.The influence of anisotropy on the seabed dynamic response and the depth of liquefaction was studied by analyzing the parameters including the Poisson's ratio,elastic modulus and permeability of seabed in different directions.4.The influence of inertia term on the dynamic response of seabed under wave loadings is analysed.Three theories including the fully dynamic theory,the quasi dynamic theory and the quasi static theory which are used to analyse the dynamic response of seabed are classified and discussed according to their applicabilities and their application occasions are given in this paper.