扩底桩极限抗拔承载力设计方法比较分析

Comparison and Analysis of Ultimate Uplift Capacity Design Method for Under-reamed Piles

在非饱和及饱和粉土两种不同土质中进行了埋深比分别为1、2、3、5四种的扩底桩抗拔大尺寸模型试验,得到了桩头荷载-位移曲线,通过s-logt法确定各桩的极限抗拔承载力,分析了饱和度及埋深比对扩底桩极限抗拔承载力的影响。使用《架空送电线路基础设计技术规定》、《建筑桩基技术规范》中推荐的计算方法及国外相关计算方法,采用原位CPT测试、考虑非饱和粉土基质吸力的影响及查表得到的土体参数分别对试验桩进行了极限抗拔承载力计算。通过计算结果与试验结果的对比,指出了采用不同土体参数时扩底桩极限抗拔承载力各计算方法的适用性。

Large scale model tests on uplift capacity of under-reamed piles with the 4 different depth ratios of 1, 2, 3 and 5 in unsaturated and saturated silt are carried out. The load-displacement curve is obtained, and the ultimate capacity is determined by s-logt method, the influence of saturation and depth ratio is also investigated. The ultimate capacity is calculated on the basis of methods recommended in Technical regulation for designing foundation of overhead transmission line and Technical Code for Building Pile Foundations, relative methods in and abroad, in-field CPT tests, consideration of suction in unsaturated silt and parameters recommended in tables. By comparing the results of calculation with that of tests, the applicability of different methods are discussed when adopting different parameters.