Study On Properties Of Contact Between Pile And Soil In Liquefying Ground

China is an earthquake-prone country in generally,multiple studies about earthquake have shown that one of the important reason of leading to the collapse and destruction of buildings is the pile foundation damage caused by seismic liquefaction,it is also one of the main form of earthquake disaster.So the issue of on pile-soil dynamic interaction in liquefiable soils is one of the hot research topics in geotechnical engineering,the study of contact surface is to be recognized as a difficulty.Soil and pile is a typical contact problem as the working together system.There is a strong dynamic interaction between the pile and soil under seismic action.The numerical research on contact surface is also the difficulty on the calculation because of the nonlinear and extremely complicated mechanical characteristics.The main content in this paper is the numerical research on pile-soil dynamic interaction in liquefiable soils.The paper used the finite element program LIQCA2 D of pile-soil interaction through the water-soil coupled elastoplastic finite element and updated Lagrangian discrete method dynamic liquefaction numerical analysis platform with the following work on the basis of summaries of the results of predecessor’s studies:The article tells the research status on pile-soil interaction and the problem of contact surface with the introduction of joint element and interface constitution.The damp is joined in the contact units in numerical simulation due to the strong nonlinear in the pile-soil system.the calculation model which can simulate the material and geomatric nonlinearities of saturated sandy soil and can consider the part of energy dissipation in pile-soil interaction is established.By simulating the pile-soil systems adding different damping on contact elements,compared the displacements and horizontal accelerations of the pile head and the soil around pile,the results show that the response of the pile-soil system is overestimated without considering the contact unit damping.In addition,there is no thickness and quality in the Goodman element and only force link between nodes and the adjacent units,similar to the Winker foundation beam model assumes.So we can apply reduction factor of p-y curve which represented as pore pressure ratio in the shear stiffness of contact unit.The shear stiffness of contact element is reduced by three kinds of reduction functions(parabola function,segmentation function and linear function)so that it is changed from static state to dynamic and finally received the changing rule of displacement time history and pore water pressure time history.The paper has certain reference value for providing some basis of finding the appropriate dynamic contact stiffness.