基于双荷载箱的超长桩自平衡试桩法试验研究

Experimental Study on Self-balancing Test Pile Method for Super-long Piles Based on Double Load Cell

南京仙新路过江通道主桥采用悬索桥结构形式,跨度布置为580m+1760m+580m,主墩拟采用66根直径2.8m超长桩基础。所在场地地质情况较复杂。在工程正式实施前,为获得主墩超长桩极限承载力及其分布规律,同时验证该类地层超长桩施工工艺的适应性,通过基于双荷载箱的自平衡试桩工艺试验进行桩基承载力分析和钻孔工效分析,为正式工程超长桩的设计及施工提供参考。结果表明,采用基于双荷载箱的自平衡试桩工艺能较准确地模拟该类地层超长桩荷载传递机理,并能获得场地原位单桩竖向抗压极限承载力和极限侧摩阻力,为桩基优化设计提供较准确的计算参数;通过优化钻头配置、增加钻头配重可大幅度提高钻孔工效。

Nanjing Xianxin Road river-crossing tunnel is built by a three-tower suspension bridge structure form,with the span arrangement of 580m+1760m+580m.66 super-long pile foundations with diameter of 2.8m are proposed for main piers,and the geologic site condition is relatively complex.Before the project implementation,in order to obtain the bearing capacity and its distribution of the superlong pile foundation in main pier,meanwhile,and verify the adaptability of super-long pile construction technology in the selected stratum,the self-balancing pile test process based on double load cells is used to test bearing capacity of pile foundations and analyze drilling efficiency,which can be viewed as the reference for design and construction of super-long pile in the formal project.The results show that the self-balancing pile test technology based on double load cells can accurately simulate the load transfer mechanism of super-long pile in this type of stratum,and can obtain the ultimate bearing capacity and ultimate lateral friction resistance of in-situ single pile,which can provide more accurate calculation parameters for the optimal design of pile foundation.The drilling efficiency can be greatly improved by optimizing the bit configuration and increasing the bit counterweight.