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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 bearing capacity of expanded-bottom piles. How to evaluate its bearing mechanism qualitatively and quantitatively is the key to the design of expanded-bottom piles. Through the model test of the enlarged-bottom pile, the bearing mechanism of the pile-end of the expanded bottom pile is discussed and analyzed. The following results are obtained: The bearing capacity of the expanded bottom pile is controlled by the exertion of pile end resistance. The unsynchronized extent of the bearing capacity of the end of expanded pile and the frictional resistance of pile are more significant than that of non-expanded pile. The ultimate failure shape of the end of the expanded pile is different from that of the non-expanded bottom pile, which is similar to that of the reverse anchor foundation. Due to the existence of the enlarged bottom, the bearing capacity of pile foundation decreases. When the design and calculation of the bearing capacity of the pile end of the expanded bottom pile, the correction of the decrease of the bearing capacity of the pile end must be carried out.