土塞效应对PCC桩振动特性影响的数值模拟

Numerical simulation on influence of soil plug effect on vibration characteristic of PPC piles

采用ABAQUS建立土塞效应作用下PCC桩的三维有限元模型,对土塞效应下PCC桩的低应变瞬态动测响应进行模拟,得出不同土塞率、不同土塞与桩壁摩擦系数下的桩顶速度时域和频域响应。结果表明:(1)随着土塞率的增大,速度时域曲线中的第一阶反射波峰的幅值减小,且幅值减小依然受三维效应的影响。(2)随着摩擦系数的增大,速度时域曲线中的第一阶反射波峰与第二阶反射波峰的幅值逐渐减小,且第一阶反射波峰幅值的减小程度较为微弱、呈线性变化,第二阶反射波峰幅值的减小程度更为显著、呈非线性变化,波形在第二个反射波峰之前才开始出现分离现象。(3)土塞效应导致波动在土塞段传播的速度减小,土塞效应越强,削减作用越强。(4)土塞效应削弱了纵向振动,横向振动与弯曲振动的耦合,从而导致PCC桩导纳曲线共振峰幅值下降。

Based on ABAQUS, a three dimensional finite element model was established to simulate the low - strain transient dynamic response of PCC pile. The velocity responses on the pile top in time and frequency domains are obtained under various soil plug ratios and friction eoeffieients of pile wall. The results show that ： （1）with the increasing of soil plug ratio, the first reflec- tion peak amplitude in the velocity - time domains curves decreases while still being afl＇eeted by the three - dimensional efl＇eet; （2）with the increasing of friction eoefl＇ieient, the amplitudes of the first and second order reflection peaks decrease gradually, show- ing a relative small and linear attenuation for the first order wave and a relative significant and nonlinear attenuation for the second order wave respectively. The wave shape separates before the second order reflection peak occurs; （3）due to the soil plug effect, the wave velocity decreases in the soil plug area and the stronger the soil plug efl＇eet is, the more significantly the velocity re- duces ; （4）the coupling of longitudinal, transverse and bending vibration of the PPC pile is weakened by the soil plug efl＇eet, hence the formant amplitude in PCC admittance curve goes down.