水平受荷阶梯形变截面桩的内力及变形分析

Internal force and deformation of step-tapered pile under lateral loads

基于线弹性地基反力法,提出水平荷载作用下阶梯形变截面桩内力及变形解析算法,该算法假定相同土层的地基反力模量为常数.根据桩身的变截面特性以及桩周土体的分层情况将桩身进行分段,建立各段的微分控制方程.考虑到桩顶、桩端边界条件以及相邻桩段间的协调变形条件,推导出符合桩段挠曲变形特征的迭代关系,得到任意边界条件下的桩身内力及变形算法.通过将该算法的预测结果与有限元计算结果以及现场实测数据进行对比分析,验证了该方法的可行性.分析桩身长径比、变径位置、桩径比对桩身内力及变形分布的影响规律.减小长径比,将变径位置向桩底下移,均可以使得桩顶最大水平位移减小,最大弯矩增大,减小下部桩径有利于减小桩身弯矩峰值,更有效地协调桩身变形.

An analytical algorithm for calculating the lateral response of a horizontally loaded step-tapered pile was proposed based on linear elastic subgrade reaction theory.The algorithm assumes a constant subgrade reaction modulus for each soil layer.The pile was segmented according to the variation in the pile section and the different soil layers.The governing equation for every segment was established.Then the iterative relationship of the deflection was derived,and the distribution of internal force and deformation of the pile with given boundary conditions were given by considering the deformation continuity between the adjacent pile segments and the boundary conditions of the pile tips.The obtained results were compared with the finite element calculation results and the field measured data in order to verify the algorithm.The influences of pile parameters such as lengthdiameter ratio,the position of the reduced diameter or pile-diameter ratio on the internal force and deformation distribution of pile were discussed.Reducing the length-diameter ratio and shifting the position of the reduced diameter to the bottom of the pile can reduce the maximum groundline displacement and increase the maximum bending moment.Reducing the pile-diameter ratio is conducive to reducing the maximum bending moment and coordinating the deformation more effectively.