均质土中竖向受荷X形混凝土桩的三维弹性变分解  

Three-dimensional variational elastic solution for axially loaded X-section cast-in-place concrete pile in homogeneous soil

作　　者：周航[1,2] 李籼橙 刘汉龙[1,2] 王增亮 ZHOU Hang;LI Xian-cheng;LIU Han-long;WANG Zeng-liang(Key Laboratory of New Technology for Construction of Cities in Mountain Area,Chongqing University,Chongqing,400045,China;College of Civil Engineering,Chongqing University,Chongqing,400045,China)

机构地区：[1]重庆大学山地城镇建设与新技术教育部重点实验室,重庆400045 [2]重庆大学土木工程学院,重庆400045

出　　处：《岩土力学》2021年第4期1012-1024,共13页Rock and Soil Mechanics

基　　金：国家自然科学基面上项目(No.51978105);重庆市技术创新与应用发展专项面上项目(No.cstc2019jscx-msxmX0107)。

摘　　要：现浇X形混凝土桩(简称XCC桩)是一种典型的横截面异形桩,其受力特性不同于常规圆形桩,即存在所谓的"异形效应",目前仍缺乏考虑XCC桩-土相互作用更严格的理论分析方法。为研究均质土中竖向受荷XCC单桩异形效应对桩基沉降的影响,基于变分原理导出考虑土体竖向和水平位移的桩-土体系控制方程,并对复杂边界平面内的控制方程进行了保角变换,借助Matlab编写差分程序,获得桩身位移函数、土体竖向和水平位移函数的半解析解。以桩身位移函数为例对差分程序的进行了收敛性验证,将所求桩位移函数与现有理论解对比,结果吻合较好;与ABAQUS有限元结果比较,也具有合理的一致性。最后,对影响桩沉降的主要因素进行了参数分析,同时将XCC桩与等截面圆桩以及等周长圆桩对比,探讨了其异形效应对无量纲化桩体刚度的影响,而后,给出了XCC桩相对于等横截面圆桩无量纲化桩顶刚度增加百分比的拟合公式。X-section cast-in-place concrete(XCC)pile is a typical non-circular cross-sectional pile of which the mechanical characteristics are different from a traditional circular pile,namely the"geometrical effects".So far,a rigorous theoretical method that considers the geometrical effects is still not given.To investigate the influence of geometrical effects of vertically loaded XCC single pile embedded into homogeneous soil on pile foundation settlement,the differential equations governing the displacements of the pile-soil system based on variational principles are obtained,which accounts for both vertical and horizontal soil displacements.The conformal mapping technique is applied to the governing differential equations in the physical plane with a complicated boundary.With the aid of Matlab software,a finite difference program is developed to solve the governing equations,yielding semi-analytical solutions of pile and soil displacement functions.The pile displacement function is selected to verify the convergence of the developed program.The pile displacement obtained from the present method is exactly the same as the existing theoretical solution.Compared with the finite element analysis,the solution for the XCC pile from our analysis is in reasonable agreement.Finally,parametric studies,which focus on the major effect factors of pile settlement,are conducted,and the geometrical effects of XCC pile are investigated by means of comparing the normalized head pile of stiffness with circular piles with the same area and the same perimeter.After that,a fitting equation for the percentage increase of the normalized pile head stiffness of the XCC pile relative to the circular pile with equal cross-section is given.

关 键 词：现浇X形混凝土桩(XCC桩) 保角变换 变分法 弹性解 竖向受荷 

分 类 号：TU473.1[建筑科学—结构工程]