P-Y Curve Of Dynamic Soil-pile Group Interaction In Liquefying Ground

In recent years, pile group are widely used in liquefying ground for bridge construction, because of its distinct advantages. However, its seismic issue has not been resolved effectively. In China, the code about the bridge pile foundation in liquefying ground has only some qualitative seismic regulations, which hamper their development seriously. p-y curve method with its own merits is widely used in the design for pile foundation. But, at present, most of the p-y curve is based on static or seismic load and did not consider the soil motion. Hence, it is imperative that to undertake research in p-y curve of dynamic soil-pile group interaction in liquefying ground. Firstly, according to the completed shaking table test of dynamic soil-pile group interaction in liquefying ground and combined with interval 24 hours two times loading, we have given the reliable method of obtaining dynamic p-y curve based on the test data. That is applied in studying the effect of the relative density on dynamic soil-pile group interaction. Secondly, we have built the 3D numerical model of dynamic soil-pile group interaction in liquefying ground and verified the reliability of the model. Then, we have set up the numerical model of shaking table test for the single pile, pile group and the corresponding dynamic p-y curve. Finally, we have analyzed that the different factors may have an effect on characteristic of dynamic p-y curve. The cognition and results have been obtained mainly as follows:First and foremost, we have accomplished the shaking table test of dynamic soil-pile group interaction in liquefying ground by loading different frequency and amplitude sine motions, using reinforced concrete 2×2 pile group-pile cap-pier system, which is towards the two layered typical field of overlying clay layer and saturated sand layer. The results show that the frequency and relative density have an significantly influence on foundation, structural system and characteristic of dynamic p-y curve, and we have found that the peak bending moment of pile group is obviously different from that of single pile.Secondly, on the basis of the completed shaking table test and completely fluid-solid coupling calculation mode, we have established the finite difference numerical model of dynamic soil-pile group interaction in liquefying ground by using solid element, beam element, pile element and Finn model to model pile cap, pier, pile and saturated sand respectively. The reliability of numerical model has been verified by the dynamic response of foundation and structure, through the site and structure dynamic response.Ultimately, we have probed into the factors that may have an effect on the dynamic p-y curve of pile group by comparing the result of single pile and that of pile group. And it indicated that the relative density, pile diameter and initial stiffness ratio of pile and soil have an appreciable impact on the dynamic p-y curve and pore pressure ratio, mass of the superstructure and width-thickness ratio of pile cap are not the case. Meanwhile, it is revealed that pile cap weakenes mass of the superstructure and width-thickness ratio of pile cap to the influence of the dynamic p-y curve.All these research offered great help for feasible solution of understanding dynamic soil-pile group interaction mechanism in liquefying ground and gaining the the dynamic p-y curve based on shaking table test. At the same time, it will provide references and techniques to the theory and numerical model of dynamic soil-pile group interaction in liquefying ground. Last but not the least, there is no doubt that it has the significant sense to take our country's bridge pile foundation seismic design method based on the deformation going forward, not only in the theory but also in practice.