静钻根植竹节桩竖向承载力计算方法研究  

Study on Vertical Bearing Capacity Calculation Method of the Static Drill Rooted Nodular Piles

作　　者：郭晶 戴国亮[1,2] Guo Jing;Dai Guoliang(School of Civil Engineering Southeast University Nanjing,210096,China;Key Laboratory of Concrete and PrestressedConcrete Structure Southeast University Ministry of Education Nanjing,210096,China)

机构地区：[1]东南大学土木工程学院,南京210096 [2]混凝土及预应力混凝土结构教育部重点实验室(东南大学),南京210096

出　　处：《特种结构》2019年第5期44-50,共7页Special Structures

基　　金：国家自然科学基金项目(51878160)

摘　　要：静钻根植竹节桩是采用静钻根植工法将预制竹节桩插入到水泥土中的新型组合桩基,对于这种桩型极限承载力的计算方法尚未统一。基于预制桩-桩周水泥土和水泥土-土两组接触面的试验和理论分析,提出考虑根植桩两种破坏模式的竖向抗压极限承载力的计算方法。若发生水泥土-桩周土界面破坏,按水泥土桩直径计算,桩侧土层的极限承载力标准值可取钻孔灌注桩的1.05~1.10倍;若发生预制芯桩-桩周水泥土界面破坏,按芯桩直径计算,桩侧土层的极限阻力标准值介于挤土桩与水泥土-土界面破坏模式侧阻之间,可取相应挤土桩的推荐值,下段竹节桩尚应考虑竹节的挤密效应系数。此外,考虑桩端水泥土扩大头对桩端承载力有改善作用。静钻根植竹节桩单桩极限承载力为两种破坏模式计算值的较小值。最后根据该计算方法得到工程实例中竹节桩极限承载力的计算值,并与静载自平衡测试结果对比,验证该计算方法的可行性。The static drill rooted nodular pile is a new kind of composite pile foundation with precast nodular pile inserted into cemented soil. There is no general accepted ultimate capacity calculation method for this pile type. In this paper a pile vertical ultimate capacity calculation method considering two failure modes is pro- posed. This method is based on the tests and analysis of side resistances between pile shaft-cemented soil interface and cemented soil-soil interface. If the cemented soil-soil interface failure mode happens the diameter of the cemented soil pile is used to calculate the ultimate capacity. Thus the static drill rooted nodular pile ulti- mate capacity is about 1. 05 ~1. 10 times of that of the bored pile in the same soil layer. If the pile shaft-cemented soil interface failure mode happens the diameter of the precast pile shaft is used to calculate the side resistance. Since the upper pile side resistance is greater than that of the displacement pile and less than that of ce- mented soil pile the upper pile side resistance is taken as that of the displacement piles. The lower part side resistance should consider the nodular pile compaction effect. Besides the improvement of the pile tip resistance due to cemented soil expanding should also be taken into consideration. The ultimate capacity of the static drill rooted nodular pile will be the smaller values of those two failure modes. Finally the ultimate capacity a nodular pile in a project is calculated using this method. A field self-balance test is performed to verify this method.

关 键 词：静钻根植竹节桩 破坏模式 桩侧摩阻力 桩端阻力 自平衡法 

分 类 号：TU473.1[建筑科学—结构工程]