石名磊  邓学钧  刘松玉
    （东南大学交通学院  南京 210096）

[提要]  根据试桩静载荷试验及桩身应力测试结果和对桩侧极限摩阻力预测技术系统的分析，研究了粘性土中大直径钻孔灌注桩(LDBPs)的桩侧极限摩阻力的预测方法和指标确定。针对硬粘土或超固结土，提出了不排水强度指数的概念，综合了粘性土不排水条件下的内摩擦角和粘聚力。基于这一概念，对传统的“a法”进行了扩展，使之成功地应用于粘性土中LDBPs桩侧摩阻力的预测。同时还对用SPT锤击数N预测粘性土中LDBPs的桩侧摩阻力进行了统计分析，并对粘土和亚粘土分别提出了相应的回归公式。
[关键词]  大直径钻孔灌注桩  桩侧摩阻力  标准贯入击数

Based on results of static loaded tests and pile shaft stress tests of instrumented piles, the approaches of predicting pile shaft skin ultimate friction and determination of the parameters are researched in the result from the analyses of the methodology of predicting pile shaft skin ultimate friction in a systematic way. The concept of the index of undrained shear strength of cohesive soils is brought forward in allusion to hard clay or over consolidation one, and that combines the friction angle and the cohesion of clay in undrained condition in effect. The representativeHd method" is modified to predict the ultimate friction of LDBPs triumphantly. The approach of count N of SPT used to predict the ultimate friction is analyzed, and the calculating formulae are established for clay and silt-clay respectively.
Keywords:  large diameter bored piles; pile shaft skin friction;  standard penetration test