超长大直径钻孔灌注桩桩端承载力研究

阐述了超长大直径钻孔灌注桩桩端承载力的影响因素,包括施工工艺、深度效应和尺寸效应等。分析和对比了目前国内常用的各规范所采用的计算方法。文中算例的计算结果表明,对于同等条件的桩,各规范的计算结果相差较大。采用自平衡试桩法获得了几个重大工程的超长大直径钻孔灌注桩的桩端承载力的实测值。将工程实例的测试结果与各规范的计算结果进行对比,证实了目前规范的计算方法不尽合理。目前各规范中桩端承载力的计算方法是在针对小直径的中短桩的研究基础上建立的。如今,大型桥梁工程中普遍采用超长大直径钻孔灌注桩的情况下,对其桩端承载力的计算应当进行相应的调整,使设计更为合理。

Bearing Capacity of Super-Long and Large-Diameter Bored Pile Tip

The bearing capacity of super-long and large-diameter bored pile tip is influenced by the facts including construction process,depth effect,size effect and so on.Three domestic codes are usually used to compute the bearing capacity of bored pile tip.Computation methods of the codes are analyzed and compared.In order to clear the difference of the computation methods,an example is proposed.Through the example,it is concluded that the computation results according to each code are discrepancy for super-long and large-diameter bored pile under the same condition.By the test method of self-balanced,the bearing capacity of super-long and large-diameter bored pile tips of five great projects are obtained.Compared the test results with the computation results,it is proved that the computation methods according to the codes are unreasonable when they are used for super-long and large-diameter bored pile.For the computation methods are established on the research on small-diameter and short or middling length piles,the codes are revised to make the design of super-long and large-diameter bored pile more reasonable.