刚性承台下柔性单桩复合地基工作特性分析

基于变形协调条件,运用力学理论,对带台柔性单桩复合地基的承载特性进行了系统的分析,得到了桩土应力比、桩身轴力分布及荷载-沉降关系等系列解析算式.计算表明,柔性桩在更多的情况下不可能像刚性桩那样将荷载传递到桩端,而存在一个有效桩长;同时,桩土应力比随荷载变化的趋势与桩体刚度、桩侧剪切刚度及桩端土的抗压刚度有很大关系.计算还显示,如果以相对变形s/b=0.004～0.01所对应的承载力作为复合地基承载力特征值的话,当桩体刚度增加一倍,复合地基承载力将增加1/3～1/2.为验证所提出方法的可行性,将模型实验的结果与计算结果进行了对比,对比表明,该方法对柔性桩复合地基的设计计算有指导意义.

Analysis of Working Characteristics of Composite Foundation with Flexible Piles under Rigid Pile-Capping

Based on the harmonic conditions of deformation and the mechanics theory,a series analytical formula for the pile-soil stress ratio,distribution of axial force and relationship of loading-settlement has been obtained by systematic analysis on the bearing characteristics of the composite foundation with flexible pile with rigid pile capping.The calculated results show that,in most instances,the loads on flexible piles can not be transferred to the pile-end and there is an effective length of the pile,which disagrees with a rigid pile.Similarly,the tendency of pile-soil stress ratio varying with loads have relations with column rigidity,shear rigidity of pile side and compressive rigidity of pile-end soil.If load corresponding with the relative deformation s/b = 0.004-0.02 was used as the bearing capacity eigenvalue of the composite foundation the bearing capacity will increase 1/3-1/2 under the column rigidity was twice as large as the primary.To verify the feasibility of the proposed method,the results of model tests are compared with the calculated results in the paper,which show that the proposed method has good guidance for design and calculation of composite foundation of flexible piles.