普通抗拔桩与托底抗拔桩荷载传递数值分析

NUMERICAL ANALYSIS ON LOAD TRANSFER OF TENSILE PILES AND BOTTOM-UPLIFTED PILES

基于FLAC3D有限差分软件,对普通抗拔桩和托底抗拔桩进行数值模拟分析,对比研究两种抗拔桩的荷载-位移曲线、桩身轴力传递特性及桩侧摩阻力分布等特性。结果表明:普通抗拔桩的极限承载力小于托底抗拔桩的极限承载力,荷载相同时普通抗拔桩的位移更大;两种桩型的荷载-位移曲线均主要由线性段构成,普通抗拔桩和托底抗拔桩在极限状态时均发生“突变型破坏”;托底抗拔桩桩身轴力由下向上传递,普通抗拔桩桩身轴力由上向下传递,两者的轴力沿深度分布形式相反:普通抗拔桩轴力随深度增加而减小,托底抗拔桩随深度增加而增大;两种桩的摩阻力分布曲线相似,上部小,中下部大;荷载水平较低时,托底抗拔桩上部摩阻力大于普通抗拔桩,荷载水平较高时,除了桩端附近,托底抗拔桩全桩摩阻力均大于普通抗拔桩;桩侧摩阻力与桩土相对位移关系呈双曲线型分布。

Based on the finite difference software FLAC3D,the numerical simulations of tensile piles and bottom-uplifted piles were conducted.Load-displacement curves,transfer of axial forces characteristics and distribution characteristics of lateral friction for the two types of piles were studied and compared respectively.The results showed that the ultimate bearing capacity of tensile piles was smaller than that of bottom-uplifted piles,and subjected to the same loads,the displacement of tensile piles was larger than that of bottom-uplifted piles.Load-displacement curves were mainly composed of broken lines.In the ultimate state,tensile or bottom-uplifted piles all failed suddenly.The axial forces in bottom-uplifted piles were transferred from the bottom to the top,and the axial forces in tensile piles were from the top to the bottom.For the two types of piles,the forms of axial forces along the shafts were opposite.With the growth of depth,the axial forces of tensile piles decreased,while that of bottom-uplifted piles increased.The lateral friction of tensile piles was similar to that of bottom-uplifted piles,which was smaller on the upper part of piles and larger on the middle and lower part of piles.Subjected to lesser loads,the upper lateral friction on bottom-uplifted piles was larger than that on tensile piles.Subjected to larger loads,except near pile tips,the lateral friction on the whole bottom-uplifted piles was larger than that of tensile piles.The curves on lateral friction and relative displacement between piles and soil were hyperbolic.