不同比例地震波作用下桩及自由场土体的响应规律

Response Laws of Piles and Free Field Soil Under Different Proportions of Seismic Waves

为探讨桩身、自由场土体以及桩土接触面在不同比例地震波作用下的响应规律,利用OpenSees软件建立了桩-土模型,其中桩土间接触采用p-y、q-z、τ-z弹簧单元模拟。分别将50%、75%和100%比例的El Centro波、Kobe波输入到模型中,结果表明:自由场土体和桩身的加速度均有放大,其中地表处和桩头承台的加速度峰值放大倍数范围分别为1.73~2.26和2.63~3.92;随着输入波比例值的增大,地表处土体和桩头承台处的加速度放大倍数逐渐降低;桩头承台最大位移比和桩身最大剪切力比均与地面峰值加速度比近似呈线性关系;在地面下3 m处和桩底处的抗力较大,地表处抗力最小;地表处的土体因塑性变形而产生残余位移,对于不同深度处的土体在地震作用下先发生剪胀后剪缩现象。

To study response laws of piles,free field soil and pile-soil interfaces under different propertions of seismic waves,the pile-soil model was constructed by the OpenSees software.The contact between pile and soil was simulated by p-y,q-z andτ-z spring elements separately.The waves with proportions of 50%,75%and 100%of the El Centro wave and Kobe wave were respectively input into the model.The results showed that the accelerations of soil and pile bodies in the free field were amplified,and the amplified ranges of the peak ground acceleration and pile cap were from 1.73 to 2.26 and 2.63 to 3.92 respectively;with the increase of the proportion of input seismic waves,the amplified times of acceleration at the ground and the pile cap decreased gradually;the maximum displacement ratio at pile caps and the maximum shear force ratio of piles were approximately linear with the peak ground acceleration;the resistances of soil at 3 m below the ground or at the pile bottom were larger,and the resistance at the ground was smallest;the residual displacement at the ground was caused by plastic deformation.For the soil at different depths,the phenomenon of shear contraction followed shear dilation occurred in soil at different depths under earthquakes.