Study On The Dynamic Interaction Of Pile-Soil For The Sea Warf In Earthquake

Pile is a very important structure which has many advantages and it has been used in high building, factory, bridge, offshore, etc. In the issue of offshore structure the most important thing is the interaction between soil and pile. In traditional designs the interaction between soil and pile is very limited to be analyzed completely and the interaction between soil and pile is not easy to be expressed by equations, so many piles have been found to destroy very quickly and very seriously. And when the pile destroyed promptly the structure of its top will lose the load capability to continue sustaining the load pressure or shear force from the top structure. This paper studies the pile-soil dynamic interaction, dynamic loads and loads combination of the offshore pile in the harsh situation of random earthquake. A finite element structural analysis of pile foundation based on the nonlinear finite element analysis procedure is presented in detailed. Also it discusses some problems of applicating the nonlinear finite element analysis procedure to the structural analysis in ocean engineering. It shows that the method utilizing nonlinear pile-soil interaction is more reasonable in the structural analysis of pile foundation. The main content of this paper is shown as follows:First, we summarize the variable damages of piles in seismic environment. As for pile, the top of it is the place which is the most easy place to destroy whether it is in water environment or no-water environment. The liquefaction interface is the dangerous place which have the most moment or shear force and the liquefaction interface problem is very similar to the strain problem in pile. After summarizing the variable damages of piles in seismic we denoted that the pile is a better structure to sustain in seismic environment than the natural basement.That is because the pile can lessen the damage degree and increase the safety of structure.On the other hand, it is aslo a good way to summarize the variable damages of piles in seismic at first and then begin the numerical analysis of it.Secondly, this paper studies the development of research on soil-structure dynamic interaction meticulously, and also the development process and history of research on the dynamic interaction between soil and structure is summarized. The characteristics of different research methods and their applicable scope are also discussed. In the pastanalysis of the historic method, it is crucial to define the analytical width of the soil elements in the direction normal to the analytical plane. This is generally defined as being identical in the length to the width of the footing in the direction normal to the analytical plane. However, there is little knowledge about whether the results obtained from the historic method analysis are overestimated or underestimated, comparing with those obtained from the applicable values. So in this paper a new methodology considering the soil-pile dynamic interaction for sea warf has been imposed.Thirdly, the dynamic interaction of soil-structure in the harsh situation of random earthquake has been studied. So this paper presents a practical numerical method of evaluating the nonlinear seismic response of piles. A soil-pile-structure system is modeled using simple beam-spring model. Lateral springs and shear springs are used as soil springs which connect the pile with surrounding soil. To take group effects among piles into account, the stiffness of the springs is evaluated from the soil stiffness matrix of the piles calculated by the thin layer element method. It is concluded that the nonlinearity of the pile decreases the seismic responses of the pile, but does not affect those of the warf significantly. On the other hand the soil in sea is much or less saturated with the water around it and this will lead to the redistribution of aperture fluid movement. The redistribution is based on the seismic load, soil seepage, pressure gradient and boundary conditions, etc. The aperture fluid movement will also affect the dynamic properties...