Horizontal Vibration Response Analysis Of Pile Foundation In Liquefied Soil

The damage of the pile foundation in the liquefaction site under the action of earthquake often leads to the destruction of the upper building structure,which brings great losses to people's life and property.Therefore,it is necessary to conduct in-depth study on the mechanical properties of the pile foundation in the liquefaction site.In the past,related scholars often regarded liquefied soil as a solid with reduced strength when studying the performance of pile foundation in liquefied soil.This method neglected the fluidity of the soil after liquefaction and did not conform to the phenomenon of large lateral displacement of soil in the actual liquefaction site.Therefore,under the premise of considering the fluidity of liquefied soil,this paper rejects the traditional idea of reducing solids and regards the liquefied soil as fluid.The dynamic impedance of single pile and group pile under these conditions is studied,which provides a certain theoretical basis and reference value of the engineering design.This paper first introduces the failure mechanism and research status of pile foundation in liquefied soil,and then introduces the research and development status of pile foundation and soil respectively,which are the most important part of pile-soil interaction.Then regards the top liquefied soil as the fluid,the lower soil is regarded as the Winkler foundation,and the displacement expression of the liquefied layer pile foundation is obtained by using the fluid motion equation and the boundary conditions of the pile and soil.Then,using the vibration displacement expression of the pile foundation under the traditional Winkler foundation,combined with the displacement and internal force continuous conditions of the liquefied soil layer and the Winkler foundation soil layer at the interface,A matrix relational expression of internal forces and the displacement of the top and bottom of the pile foundation during liquefaction of the top layer is obtained.Then,using the embedding condition of the pile bottom,the impedance expression of the pile top is obtained.Then,the positions of the liquefied soil were separately placed in the middle and bottom of the soil for analysis and calculation.Finally,using the group pile dynamic interaction factor,the impedance expression of the pile group at the top liquefaction is obtained,and the dynamic impedance of the 2×2 and 4×4 group piles is analyzed,which enriches the research theory of pile foundation in liquefied soil.In the case study,the following results were obtained: when the top soil l ayer is liquefied,the increase of axial force will reduce the stiffness factor and increase the damping factor;the increase of fluid density will reduce the stiffness factor and increase the damping factor;the increase of liquefaction depth will reduce the stiffness factor and damping factor,but the effe ct is very small when the liquefaction depth exceeds 0.75.In the analysis of different liquefaction positions,it is found that the greater the liquefaction depth,the greater the stiffness and damping of the top of the pile foundation,indicating that the top soil's liquefaction has the greatest damage to the pile foundation,and also tells us that the upper soil's liquefaction should be prioritized in the project.In the 2×2 group piles analysis,the a xial force,fluid density and liquefaction depth have similar effects on the pile groups' impedance as the single pile.When performing 4×4 pile group's analysis,the increase of the aspect ratio will reduce the initial stiffness factor of the pile group.Finally,the influence of the number of group piles on the impedance is discussed.The results show that the more number of piles,the more severe the group pile impedance changes with the excitation frequency.