根式桩基础竖向荷载传递机制研究与极限承载力计算  

Vertical load transfer mechanism and ultimate bearing capacity calculation of root pile foundation

作　　者：于炎成 任伟新 殷永高 罗晓光 YU Yancheng;REN Weixin;YIN Yonggao;LUO Xiaoguang(School of Civil and Hydraulic Engineering,Hefei University of Technology,Hefei 230009,China;School of Civil and Transportation Engineering,Shenzhen University,Shenzhen 518061,China)

机构地区：[1]合肥工业大学土木与水利工程学院,安徽合肥230009 [2]深圳大学土木与交通工程学院,广东深圳518061

出　　处：《建筑结构学报》2023年第7期204-215,共12页Journal of Building Structures

基　　金：国家自然科学基金项目(51778204);深圳市科技创新委员会项目(KQTD20180412181337494,ZDSYS20201020162400001)。

摘　　要：根式桩基础由于根键的存在,可以有效提高桩基的竖向承载力,但其竖向荷载传递机制与极限承载力计算复杂于传统桩基础。根据秋浦河大桥现场根式钻孔灌注桩自平衡试验,建立相应的数值模型并通过荷载-位移曲线进行验证,对根式桩基础竖向荷载传递机制和承载模式进行探讨。现场试验与数值计算结果表明:根式桩基础具有足够的承载能力,根键可以充分调动桩周更大范围土体的承载力,根键对减小桩身轴力、增大桩侧摩阻力和极限承载力的作用明显;加载后期,根键分担荷载所占比例不断提高,最高可达36.37%,而混凝土用量仅增加了3.18%。根据根键层间距的不同可将根式桩基础承载模式分为环形剪切、根键相互影响和根键独立作用3种模式,考虑根键相互影响和桩端阻力折减分别给出了3种承载模式对应的极限承载力计算式,极限承载力计算值与现场3根试桩实测结果吻合良好,满足工程要求。Due to the existence of roots for the root pile foundation,the vertical ultimate bearing capacity of the pile foundation can be increased effectively.However,the vertical load transfer mechanism and ultimate bearing capacity calculation of root pile foundation are obviously more complex than that of the traditional piles.According to the field self-balance load test of the root bored pile foundation of Qiupu River Bridge,the corresponding numerical model was established and verified in terms of measured load-displacement curves.Subsequently,the load transfer mechanism and load-bearing mode of root pile foundation were investigated by the verified numerical model.Both numerical and field experimental results have shown that the root pile foundation has a sufficient bearing capacity where the roots can fully mobilize the bearing potential of a larger range of soil around the pile.The roots in the root pile foundation can significantly reduce the pile axial force,increase the shaft friction resistance,and improve the ultimate bearing capacity.The proportion of the load distributed by the roots continues to increase at the later stage of loading,up to 36.37%,while the amount of concrete only increases by about 3.18%.According to the different spacings of root layers,the load-bearing modes are divided into three types:circular shear mode,roots interaction mode and roots independent action mode.Considering the roots interaction and pile end resistance reduction,the ultimate bearing capacity calculation formulas according to the three bearing modes were proposed respectively in the paper.The calculation results by using proposed formulas are in good agreement with the measured results of three test piles on site,which meets the engineering requirements.

关 键 词：根式桩基础 现场试验 数值分析 荷载传递机制 承载模式 极限承载力计算 

分 类 号：TU473.14[建筑科学—结构工程] TU317.2[建筑科学—土工工程]