杭州亲水平台桩基托换施工影响数值分析

Numerical Analysis for Underpinning Piles of Hangzhou Qin-Shui Platform

采用有限元数值方法对杭州亲水平台结构托换施工加载进行优化分析。对上部结构与地基进行整体建模,将结构与桩基考虑为弹性材料,而地基视为弹塑性材料。采用弹塑性有限元模型对主动托换施工进行了数值模拟,详细分析了托换施工诱发上部结构平台板(附加应力及二次变形)的影响特性,得到了施工诱发板X、Y向的应力状态以及Z向位移的重分布规律。基于施工诱发的结构板Z向最小变形原则优化千斤顶的预加顶力,并依据截桩前后平台结构的应力重分布规律验证了最优预加顶力大小。分析表明,托换系统顶升力宜小于柱原位受力状态,最优预加载为0.8倍原始荷载。

In this paper,FEM analysis is performed to obtain an optimization project for pile construction to underpin Hangzhou Qin-Shui platform structure.By integrating superstructure and foundation into a whole model,the structure and foundation are taken as purely elastic materials while subsoil is taken as elastic-plastic material.By using elastic-plastic finite element model of underpinning,the induced behaviors（additional stress and secondary deformation）of upper structure caused by underpinning has been studied to show re-distribution of stress in X and Y direction and that of displacement in Z direction.The criterion of minimum platform deflection is used to obtain the optimum pre-applied load by oil jacks.Moreover,the re-distribution of platform stress after the construction has also investigated to verify the magnitude of optimum preload.It has been concluded that the raising forces of oil jacks is less than original forces of columns.The optimum ratio of them is about 0.8.