桩竖向振动引起的饱和土体孔压积累效应分析

 采用一种非耦合分析方法模拟桩竖向振动过程中桩周产生孔压积累现象。首先基于比奥饱和多孔介质理论，考虑桩土间的非完全黏结条件，得到饱和土中弹性支承桩竖向耦合振动稳态孔压振动的解析解，通过卷积方法和数值积分逆变换得到任意次正弦激励作用下的瞬时孔压振荡半解析解。然后利用土动三轴试验得到饱和粉质黏土的残余孔压积累经验公式，以桩侧土剪应变和振次为参数建立桩周残余应变和瞬时孔压时域响应之间的联系，实现桩竖向振动作用下桩周土中孔压积累的模拟。数值计算结果表明，桩土非完全黏结条件下稳态孔压分布和桩周孔压积累均小于完全黏结情况，且受桩土接触刚度和桩底支承刚度的影响显著，此外桩周稳态孔压分布与渗透系数密切相关。

ANALYSIS OF PORE PRESSURE ACCUMULATION IN SATURATED SOIL INDUCED BY PILE VERTICAL VIBRATION

A non-coupling method is used to simulate the pore pressure accumulation in surrounding soil induced by pile vertical vibration. Firstly，an analytical solution of steady-state pore pressure built up by vertical vibration of a floating pile in saturated soil is obtained based on Biot?s theory of saturated porous media，considering the imperfect bonding condition at the contact surface of pile and soil in the course of pile sinking. A semi-analytical solution of transient pore pressure oscillation is deduced by using a convolution method and a numerical integration technology of the inverse Fourier transform under arbitrary sinusoidal excitations. Then according to empirical formula of residual pore pressure of saturated silty clay obtained from dynamic triaxial test，a connection between the steady pore pressure and the residual pore pressure is established in terms of shear strain and excitation times. Furthermore，the simulation of pore pressure accumulation of surrounding soil aroused by pile vertical vibration is successfully achieved. Numerical results show that the steady-state pore pressure distributions and pore pressure accumulations in the imperfect bonding condition are smaller than the ones in the perfect bonding conditions. The contact stiffness between pile and soil and the rigidity at pile toe have significant effects on them. Besides，the permeability coefficient of soil has obvious effect on steady-state pore pressure distributions.