The Study On Interactions Between Single Pile And Saturated Seabed Under The Effect Of Wave

Ocean engineering has been boomingly growing recently,which makes pile foundation,a significate foundation form in marine structures,become a core object in research of ocean geotechnical engineering.The true marine environment is extraordinary complicated.The influence of wave on soil around structural foundation and wave-induced pore pressure's effect on seabed and structure are both supposed to be concerned.Therefore the interaction between seabed and pile acts an important role in structural safty reasearch under wave load.In this paper,numerical method and laboratory test are adopted to investigate the interaction between seabed and pile.Firstly,compressive test with pile is proposed to study the response of embeded pile and saturated sandy soil under cyclic water pressure.After verification of numerical model with the same condition as test,the verified methods are used in modelling embedded single pile and seabed model to reveal the response of pore pressure,pile moment and displacement.Then pile-column-seabed model is developed with the consideration of direction on pile and wave,which is more in accordance with marine conditons.Finally,based on the comparison with embedded single pile seabed model and pure seabed model,the parameter analysis is conducted.The main contents are as follows.1.The response of pore pressure in soil around pile is studied,and pile strain and displacement is obtained according to laboratory test.Based on classic test in marine geotechnics,a totally embedded pile is attached to the compressive test for the better simulation of marine environment,in which related response are measured.The results show that phase lag and amplitude decay are more obvious with pile.Effects of pile diameter on pore pressure's distribution are not ignorable.And the strain extrema appears when seepage flow in soil has the most influence.2.A 3D numerical model is developed for single pile in seabed to study response under wave,where quasi-static theory is applied to simulate wave load and contact face is utilized to deal with interaction between pile and soil.Results show that the pore pressure around pile is smaller than in pure seabed model,while pore pressure near the pile end is amplified with increasing positive phase shift.Related responses are greater in coupled model than in contact model and stress concentration is evident near the pile end in coupled model.3.A 3D numerical model with more qualified conditons is developed.Based on totally embedded pile-seabed model,a pile-column-seabed model is proposed with direct action of wave on pile.Results show that pore pressure changes rapidly at the upper half layer,and distribution on pile's two sides are symmetrical.So it's feasible to reinforce upper layer seabed in design.The pile's effect on pore pressure reaches double pile diameter and wave crest works longer on pile moment.4.Parameter analysis of pile-column-seabed model is conducted.Results show that pore pressure turns larger and impacts deeper with smaller permeability.The extrema of pore pressure and pile's lateral displacement will increase when elastic modulus of soil decrease.Between soil and pile,the decrease of friction coefficient will induce pile's vertical displacement and increase pore pressure near the pile end.When wave period is short,pore pressure near the seabed surface is fierce and affects deeper.While wave period is long,pore pressure near pile end is amplified obviously.And wave heigt is linear ralated to lateral displacement.