常泰长江大桥6号墩沉井下沉施工监控技术  

Techniques to Monitor Caisson Sinking Construction of Pier No.6 of Changtai Changjiang River Bridge

作　　者：刘少成 黄锐 马远刚 颜天成 谭国宏[3] LIU Shaocheng;HUANG Rui;MA Yuangang;YAN Tiancheng;TAN Guohong(China Railway Bridge Science Research Institute Co.,Ltd.,Wuhan 430034,China;State Key Laboratory of Bridge Intelligent and Green Construction,Wuhan 430034,China;China Railway Major Bridge Reconnaissance&Design Institute Co.,Ltd.,Wuhan 430056,China)

机构地区：[1]中铁大桥科学研究院有限公司,湖北武汉430034 [2]桥梁智能与绿色建造全国重点实验室,湖北武汉430034 [3]中铁大桥勘测设计院集团有限公司,湖北武汉430056

出　　处：《桥梁建设》2024年第5期7-15,共9页Bridge Construction

基　　金：国家重点研发计划项目(2021YFB1600300)。

摘　　要：常泰长江大桥主航道桥为主跨1208 m的公铁两用斜拉桥,大桥6号墩采用平面圆端形、立面台阶型的超大钢壳混凝土沉井基础,沉井基础底平面尺寸为95.0 m×57.8 m,总高72.0 m,下沉穿过黏土、砂交互地层。为有效控制6号墩沉井下沉施工风险,提高下沉效率,提出“一条主线、三个限定”的总体控制原则。在沉井下沉可行性控制方面,将沉井底面支承反力监测点布置在内、外井壁和隔墙的刃脚踏面上,兼顾了沉井下沉阻力计算、地基土失稳破坏风险预警和取土效果评价的功能;提出基于CPT评估砂土层沉井外井壁刃脚踏面反力的经验算法,解决了施工前难以评估沉井下沉端阻力的问题;提出采用分项计算下沉阻力、分状态评估沉井下沉可行性的方法,解决了下沉系数的力学意义不明确、难以准确评估下沉可行性的问题。在地基土稳定性控制方面,提出基于圆弧滑动理论评估地基土稳定性的方法,确定保证地基土稳定需控制外井壁刃脚踏面反力不小于1.0 MPa。在沉井姿态控制方面,提出将下沉侧阻力占下沉总阻力的比重系数作为沉井突沉风险判定指标,根据该指标判断该沉井突沉风险较低。基于上述监控技术,6号墩沉井实现了平稳、高效下沉。The main navigation channel bridge of Changtai Changjiang River Bridge is a rail-cum-road cable-stayed bridge with a main span of 1208 m.The pier No.6 is supported by a giant stepped caisson foundation of a steel shell and concrete composite structure that needs to sink through the intersected clay and soil layers.In plan,the caisson is round-ended,measuring 95.0 m by 57.8 m,with the height reaching 72.0 m.To effectively control the sinking construction risk and improve caisson sinking efficiency,a control philosophy of"one dominant alignment and three constraints"was proposed.Considering the constructability,the uplift monitoring points were arranged in the interior and exterior caisson walls as well as the treads of cutting edges,to satisfy the demands of sinking resistance calculation,foundation soil erosion prediction and soil excavation effect evaluation.An empirical algorithm based on cone penetration test(CPT)to evaluate the reaction forces at treads of cutting edges of exterior caisson walls was proposed,to calculate the bottom resistance of the caisson during the sinking process.To elucidate the significance of the sinking factor and accurately evaluate the sinking feasibility,itemized calculation of the sinking resistance and state-based sinking feasibility evaluation were employed.An arc-sliding-theory-based method was utilized to evaluate the foundation soil stability,finding that controlling the reaction forces of treads of the cutting edges below 1.0 MPa was critical to the foundation soil stability.To bring the attitudes of the caisson under control,the portion of lateral resistance during sinking in the total sinking resistance must be taken as the judging index of abrupt sinking risk,and for the Changtai Changjiang River Bridge,the abrupt sinking risk was low.By taking the measures,the caisson of pier No.6 sank smoothly and expeditiously into position.

关 键 词：斜拉桥 台阶型沉井基础 下沉可行性 地基土稳定性 姿态 安全性 施工监控 

分 类 号：U448.27[建筑科学—桥梁与隧道工程] U443.131[交通运输工程—道路与铁道工程] U445.557