大直径扩底桩端阻力折减问题探讨

目前人们对大直径扩底桩端阻力折减问题有不同的看法。从大直径扩底桩的承载机理入手，通过桩端面积不同的对比现场试验研究、数值模拟分析等，对大直径扩底桩的端阻力折减问题进行了探讨。结果表明，大直径扩底桩端阻力折减系数实质上是一个与基础结构特性相关联的尺寸效应系数，只是在形式上表现为变形折减或强度折减。在保证桩端土变形和强度满足上部结构要求的前提下，相对折减系数法以增大桩基的沉降为代价来提高桩基设计中的桩端承载力。最后提出了一些其它应注意的端阻力折减问题。

Study on modifying coefficient of end-bearing resistance of large diameter belled piles

The current viewpoints on the modifying coefficient problem of end-bearing resistance of large diameter belled piles are different. The results of four groups contrastive field full-scale axial loading tests investigating the influence of base diameter to end-bearing resistance and settlement behavior of large diameter belled piles in a clay layer site are discussed. Also, a plane finite element model is adopted to analyse the bearing mechanism of large diameter belled piles. Based on the tests and numerical simulation, a study on modifying coefficient of end-bearing resistance of large diameter belled piles is carried out; and some conclusions are drawn as follows, Firstly, the modifying coefficient of end-bearing resistance of large diameter belled piles is essentially a kind of dimension modifying coefficient. The coefficient behave as a modifying coefficient of deformation or strength of base soil layer formally. Secondly, under certain precondition, the relative modifying coefficient method can make piles obtain larger end-bearing resistance in oile foundation design. Finally, other related problems on which attention should be paid are proposed.