横向扩展液化土中单桩-土系统的非线性分析

Nonlinear analysis of single pile-soil system in lateral spreading liquefied soil

将地震液化场地分为地表的上覆未液化土层、底部的未液化基层以及夹在两者之间的液化土层,基于桩-土相互作用的非线性Winkler模型,考虑桩弯曲的非线性弯矩-曲率本构关系和桩的几何非线性变形,建立了液化土层横向扩展下桩非线性大挠度变形的基本控制方程,并利用打靶法进行了数值求解。同时,给出了桩线弹性小变形情形下的解析解。通过与非线性有限元解和线弹性小变形解析解的比较,验证了文中打靶法的有效性和可靠性。用数值方法分析了液化土层横向扩展对桩力学性能的影响,结果表明:非线性桩-土相互作用和桩材料非线性效应强于桩的几何非线性效应,随着液化土层横向扩展位移的增加,几何非线性效应逐渐增大,此时,应采用完全非线性模型进行桩力学行为的分析。

Regarding the seismic liquefied field deposit as being composed of a non-liquefied crust layer at the ground surface,non-liquefied base layer and a sandwiched liquefied layer,based on the nonlinear Winkler model for pile-soil interaction and taking both the nonlinear bending moment-curvature constitutive relationship and geometric nonlinearity of the pile,the fundamental governing equations for nonlinear large deflection deformation of the pile undergoing soil layer’s lateral spreading are formulated and are solved numerically with the shooting method.At the same time,the analytical solutions of the pile are presented for the case of small deformation and linear elasticity.The validity and reliability of the shooting method presented in the paper are verified by comparing the results of the shooting method with those of the nonlinear finite element method and analytical solutions.The influence of the lateral spreading of the soil layer on the mechanical behavior of the pile is investigated numerically.The results show that the effects of nonlinear interaction between the pile and soil as well as material nonlinearity of the pile are much stronger than that of the geometric nonlinearity of the pile.The effect of the geometric nonlinearity is increased with the lateral spreading increasing of the liquefied soil layer.And it’s necessary to analyze the mechanical behavior of the pile with fully nonlinear model.