Analysis Of Dynamic Response Characteristics Of Seabed Saturated Sediment Under Different Permeability Conditions

With the development of science and technology and the increase of economic activities,the process of human exploitation and utilization of the ocean is accelerated,and the number of sea area projects is increasing gradually.Considering the important influence of earthquake on the stability of ocean structures and seabed(such as seabed liquefaction,seabed landslide,submarine pipeline and other submarine structures,instability of Marine engineering structures,etc.),the dynamic response of submarine sediments under earthquake has been one of the research hotspots of earthquake engineering and ocean engineering disciplines.Based on Biot porous media theory,many scholars have conducted in-depth research on the dynamic response of seabed sediments by numerical simulation or theoretical calculation,and great progress has been made.However,in previous studies,most of the scholars assumed that the bottom of the seafloor sediments was the impervious interface,and directly assumed that the bedrock was the impervious single-phase medium.However,in practical engineering,the permeability of seabed bottom can not be completely ignored.In view of this situation,it is of great theoretical and engineering significance to study the dynamic response characteristics of seafloor sediments under earthquake by using different boundary conditions of seafloor sediments with different permeability properties.The main contents of the paper are summarized as follows:1.The research background and significance of this paper are expounded,the research status of seabed dynamic response based on Biot porous media theory is summarized,and the seabed model adopted in this paper is introduced,as well as the main discussion contents in the following chapters.2.The sea-bed model of seawater layer and saturated sediment layer is established,four typical boundary conditions are given,and the analytical or semi-analytical solutions of sea-bed under four typical boundary conditions are obtained by means of eigenfunction expansion method and fine time integration method.The influence of the permeability of the bottom of the sedimentary layer on the transient response of the seabed during an earthquake is discussed by using examples.3.According to the model of seawater layer and saturated sediment layer,through the wave field analysis and linear equation solving of different layers of the model,the steady state response analytical solutions of saturated sediment layer with different permeability properties are given.The influence of the permeable conditions at the bottom of saturated sediment on the dynamic response is analyzed when the frequency of incident wave changes and the depth of coastal bed changes.4.Considering the influence of bedrock on the dynamic characteristics of seafloor sediments,a model of seawater layer,saturated sedimentary layer and bedrock layer is established,and the analytical solution of the steady-state response of multi-layered saturated seafloor sediments with different permeability properties is derived.With the help of this solution,the influences of the permeable conditions at the bottom of the saturated sediment on the dynamic response characteristics when the frequency of the incident wave changes and the depth of the coastal bed changes are analyzed.On this basis,by using a thin layer of saturated porous media and controlling the permeability coefficient at the bottom of the model,the steady-state response characteristics of saturated sediments with different permeability properties are analyzed.