抗拔单桩受力性状的解析算法

在荷载传递法的基础上,提出了一种抗拔单桩变形的简便解析算法。此法可反映桩侧摩阻力逐渐发挥至极限状态的过程,且可用于分析抗拔单桩位于成层土中的情况。算法的关键是确定合理的抗拔桩极限侧阻,进一步明确了抗拔桩极限侧阻计算时各参数的取值,并指出应将抗压桩极限侧阻计算值的0.7倍作为抗拔桩的极限侧阻计算值。已有现场试验抗拔单桩实测数据和此算例对比分析表明此法是合理可行的且方便快速。

广州某花岗岩地块单桩承载力特征值综合确定

全风化及强风化花岗岩极限侧阻由于其矿物组成及含量不同而差别大,且受地下水及施工工艺的影响较大,难以取值。工程根据静载试验成果,确定其单桩竖向抗压极限承载力,采用规范经验公式,返求全、强风化花岗岩极限侧阻,再与规范经验值对比,综合确定其推荐值,最后根据设计荷载要求,确定单桩竖向抗压承载力特征值。综合确定的全、强风化花岗岩极限侧阻力标准值已经考虑了矿物组成及含量、风化环境、地下水、成桩工艺、泥浆比重等多因素的影响,对特定场地及特定施工工艺下的单桩竖向抗压承载力特征值确定具有直接的指导意义。

Study of LDBPs Shaft Skin Friction for Piles in Cohesiove Soils

The methodology of predicting pile shaft skin ultimate friction has been studied in a systematic way. In the light of that, the analysis of the pile shaft resistance for bored and cast in situ piles in cohesive soils was carried out thoroughly in the basis of field performance data of 10 fully instrumented large diameter bored piles (LDBPs) used as the bridge foundation. The undrained strength index μ in term of cohesive soils was brought forward in allusion to the cohesive soils in the consistence plastic state, and can effectively combine the friction angle and the cohesion of cohesive soils in undrained condition. And that the classical ' α method' was modified much in effect to predict the pile shaft skin friction of LDBPs in cohesive soils. Furthermore, the approach of standard penetration test (SPT) N value used to estimate the pile shaft skin ultimate friction was analyzed, and the calculating formulae were established for LDBPs in clay and silt clay respectively.