扩底桩桩端承载机制初探

A discussion on pile-tip bearing mechanism of pedestal pile

桩端承载力是扩底桩承载力的主要组成部分,如何定性、定量地评价其承载机制是扩底桩设计的关键。通过扩底桩的模型试验,对扩底桩桩端承载机制进行了探讨分析,得出了以下结果:扩底桩承载力的大小受桩端阻力的发挥程度控制。扩底桩桩端承载力和桩周摩阻力发挥的不同步程度要比非扩底桩的显著。扩底桩桩端极限破坏形状与非扩底桩的不同,类似于逆向的锚板基础破坏形状。由于扩底部的存在,使得桩端地基承载力强度有所下降;在扩底桩桩端承载力设计计算时,必须进行因扩底引起桩端承载力降低的修正。

The bearing capacity of pile tip is the main component of the pedestal pile; so it is the key of the pedestal pile design that how to evaluate the bearing mechanism qualitatively and quantitavely. By the model test of pedestal pile, we＇ve done some discussion and analysis of the pile-tip bearing mechanism of the pedestal pile, and drawn some conclusion as follows. The value of the pedestal pile bearing capacity is determined by the exerting level of the pile-tip bearing capacity. The unsynchronized level of the pile-tip bearing capacity and shaft resistance of pedestal pile is much more obvious than that of the non-pedestal pile. The limit equilibrium zone of the pedestal pile tip is different from that of the non-pedestal pile tip; but is similar to that of contrary anchor-slab foundation. Because of the enlarged part, the foundation bearing capacity at pile tip is lower in some extent; so during the design and calculation of the pedestal pile tip bearing capacity, it is necessary to modify the pile tip beating capacity lowered by the enlarged bottom.