The Research On Vertical Vibration Characteristics Of Rigid Circular Plate In Complex Ocean Environment

With the world's exploitation of marine resources,more and more structural facilities are built in the marine environment,such as offshore wind turbines built for the application of offshore wind energy,offshore drilling platforms built for the exploitation of resources such as subsea oil and natural gas hydrate and the marine defense engineering applied to the national military and so on.Compared with the land environment,during the service of the marine structure,the foundation will be subjected to various dynamic loads such as wind,waves,currents,and earthquakes,and the force situation is more complicated.Therefore,it is very important to study the vertical vibration characteristics of the rigid foundation in the marine environment.At present,gravity foundations(surface-exposed foundations)or suction anchor foundations are more commonly used in marine foundation applications.In this paper,the upper disc structure of the gravity-based foundation and suction anchor foundation in ocean engineering is simplified into a rigid disk on the surface of the seabed.The vertical vibration characteristics of the rigid disc foundation in seawater-saturated foundation are analyzed.The main research work of the thesis is as follows:(1)Based on the coupled seawater-seabed half-space model,treating the seabed soil as a transversely isotropic saturated porous medium,combining the Biot dynamic equation and the transversely isotropic constitutive equation,directly decoupling,and applying the Hankel transform,The solution under the Hankel transform domain is obtained,combined with the boundary conditions of the surface of the seawater,the interface between the seawater and the seabed soil,the Tranter-type dual integral equation is obtained,and it is converted into the second type of Fredholm integral equation,and the cross-section under the seawater The vertical vibration solution of the rigid disc foundation on the isotropic saturated seabed.For the permeable and impermeable conditions of the bottom of the plate,the vertical dynamic compliance coefficient of the seawater depth,frequency and soil parameters on the foundation,the stress distribution of the bottom of the plate and the foundation are discussed.Changes in displacement and stress.(2)The vertical vibration characteristics of the disc foundation on the saturated seabed of the underlying bedrock overlying seawater are studied.Based on the Biot wave theory and the stress-strain relationship of the saturated porous medium,a potential function is introduced,and the integral transformation is used to obtain the Displacement and stress solutions,based on the mixed boundary conditions of seawater-seabed and bedrock stress and displacement,obtain the dual integral equation,and convert it into the second type of Fredholm integral equation;consider the two types of cases of permeable and impervious bottom The effects of soil permeability coefficient,seawater depth and bedrock depth on the vertical dynamic flexibility coefficient of the foundation,the stress distribution at the bottom of the plate and the response of the seabed soil are analyzed.