Centrifuge Model Test And Numerical Simulation Of Seismic Response Of Bridge Pile Foundation In A Slope

The lateral movement of soil with inclined surface is the main reason that frequently causes damage to piles under bridge extending along mountain side.This new-coming problem of highway projects in western China is quite complex and also hard to prevent.Based on the existing research methods and achievements,this paper carried out targeted research.A single pile,a pile on the top of a slope,and a 1 ×2 pile group were tested on a shaking table installed on a centrifuge.The history of accelerations in the slope,strains along each pile shaft,and pile head displacements were measured using accelerometers,displacement sensors,and strain gauges installed in the model.Then,the amplification factor of acceleration at each point,pile moment and displacement histories were analyzed,in order to discuss the site influence of sloping ground,pile-slope interaction,and the residual displacement of each pile.On the basis of the experimental results,a two-dimensional computational model was established by using the finite element software OpenSEES.The deformation characteristics of the soil and pile-soil interaction under seismic were analyzed,and the following conclusions were obtained:(1)By comparing the time history of each measurement point in the slope with that of the shaking table,it is found that the seismic wave is continuously magnified in the soil.The amplification effect is most obvious on the surface.Input seismic waves' spectrum properties will be changed obviously after propagation through the model soil,the soil in slope had amplification effect to seism waves at low frequnency and filtering effect at high frequency.With the increase of input seismic amplitude,the filtering effect of soil is more obvious,and the band of amplification effect is narrowed;(2)By using the signal processing technique,the time history of the acceleration is processed and corresponding displacement time history is obtained.It is found that slopes shoulder instability occurs first in the slope under earthquake action.With the earthquake,the deformation of the upper soil mass is gradually completed and reached a steady state.The slope near the deformation position is still under development;(3)Based on the theory of mechanics,the strain history of the pile is calculated.through the cubic spline interpolation and the calculus principle,the bendingmoment and displacement distribution of the pile are obtained.The maximum bendingmoment of each model pile is above the bedrock interface.After earthquake,the bendingmoment of group pile P3 is the biggest,followed by the single pile on the slope P2,group pile P4 and the single pile on the top P1.The displacement of single pile on slope P2 is the biggest,followed by the single pile on the top P1,group pile is minimum;(4)With the earquake,there is obvious relative displacemet between the soil around the pile.The soil before piles gradually lose the support function on the pile,the squeezing effect of the soil is increasing,accelerated the damage of pile foundation.