基于CPTU测试的桩基承载力可靠性分析

Reliability assessment of bearing capacity of pile foundation based on CPTU data

通过连盐高速(连云港—盐城)和宁常(南京—常州)高速公路PTC、CFG和PHC桩基场地进行的CPTU试验资料,提出了一个预测桩基承载力的CPTU新方法。桩单位侧阻力由CPTU超孔压和侧壁摩阻力得出,而桩单位端阻力则由有效锥尖阻力获得。以静载荷和高应变试验得到的桩基承载力作为参考值评估了各种方法预测桩基承载力的有效性。基于可靠度理论,分别分析了承载力极限状态、正常使用极限状态与联合承载力极限状态和正常使用极限状态的可靠度指数。针对几种CPTU桩基预测方法,分别进行了可靠性分析。结果表明:提出的CPTU方法比其余3个方法具有更高的可靠度。CPTU方法具有简单、快速、多参数的优点,并且不依赖于操作者主观性的影响,在桩基工程中值得推广应用。

A method to evaluate the axial capacity of pile foundation is proposed in which the pile unit skin friction and the unit end bearing resistance are computed from the sleeve friction,excess pore water pressure and effective cone resistance,qe.The component reliability indices based on the ultimate limit state（ULS） and the serviceability limit state（SLS） criteria and the system reliability indices combining ULS and SLS are evaluated.Reliability analysis is conducted to evaluate the performance of the proposed CPTU method.The results show that the proposed CPTU method has higher reliability indices than other three methods.Further assessment of CPTU-based pile capacity in other Jiangsu clay sites should be made.The CPTU method is simple,fast and independent of all operators＇ subjective influence.Therefore,it is notably suitable for use in pile engineering practice.