Study On Mechanical Behavior Of Marine Pile Foundation And Soil Under Wave Loading

The marine pile foundation that used in an open ocean terminal or a marine platform,is always under complicated loads,include wind,waves,tides,currents,ice and so on.There have been many accidents caused by the instability of marine pile foundations,which resulted in significant economic losses and adverse social impacts.Therefore,it is imperative to study the problems of offshore pile foundation and hydraulic characteristics of seabed soils under wave loading in order to improve the safety and structural reliability of offshore pile foundation.This thesis discusses the mechanical properties of marine pile foundation and soil under wave loading.The numerical method is used to study the dynamic response of seabed under wave loading,and verify the experimental results by the theory.Using cylinder test equipment to study the effects of water depth,wave height,period on the response of soil.The research contents and conclusions are summarized here:(1)Establish a wave-seabed dynamic model.Use Flow3 D to simulate the linear wave,and then import the wave simulation result into COMSOL.Applying the FEM method solves Biot dynamic equation coupled with soil and water.The correctness of the numerical model is verified by comparing the numerical results with the analytical results of the literature.After that,comparing the experimental data of sandy seabed with the numerical simulation results to confirm the correctness of the experimental method.Then discuss the effects of wave period,water depth and soil permeability coefficient on the pore water pressure.(2)Experiment studies on sand and silt seabed.It is found that the increase of the wave period T,the wave height H and the soil permeability coefficient Kz will increase the maximum amplitude of pore water pressure in the seabed.The results of liquefaction analysis show that the smaller wave period,higher wave height,larger soil particles and lower relative density will lead to deeper liquefaction depth of the seabed.It is found that the phases of pore-water pressure in different depths under wave loading produced a hysteresis compared with the wave phase.The pore-water pressure in bottom is about 1-2s behind the wave pressure in seabed surface.In silty seabed,the pore water pressure waveform will produce some deformation.(3)Experiment studies on seabed model with pile.It is found that the increase of wave period and wave height will increase the maximum amplitude of pore water pressure of the soil around the pile;The increase of the relative density of seabed will reduce the maximum amplitude of pore water pressure of the soil;The pore pressure in the seabed soil near the pile bottom suddenly increases,and the increase of wave period,wave height and permeability coefficient will increase this amplification effect.The increase of wave height and the decrease of wave period will increase the liquefaction depth of the seabed.The presence of pile will also affect the liquefaction depth of the seabed,when the pile rises,the liquefaction depth will be reduced.