运营桥梁抬桩加固既有桩基础沉降分析及监测研究

摘要

为研究运营桥梁抬桩加固施工引起的既有桩基础扰动对结构安全性的影响,以沪渝高速(G50)太湖大桥抬桩加固施工为背景,采用有限元软件建立桥墩和基础(一半结构)有限元模型,分析抬桩施工过程桥墩位移规律和既有基桩弯矩;抬桩施工过程中,基于现有流体静力水准系统(HLS),在墩身内侧布置2个监测点,进行墩身沉降在线监测.结果表明:抬桩施工过程对既有桩基础沉降无影响,承台扩大后改善了既有基桩抗弯性能;监测期间,施工和车辆荷载对既有桩基础(桥墩)沉降的影响表现为数据整体平稳基础上的波动,无施工及车流量小的夜间,消除弹性变形(沉降)后的最终平均沉降约1.2 mm;采用高精度的 HLS可实现施工过程中桥墩(基础)沉降的在线监测,提高了效率,综合保障了运营桥梁的安全.%To study the influence of disturbance caused by the strengthening of existing pile foundation by adding piles on the structural safety of the bridge in service,the strengthening con-struction of the Taihu Bridge on the Shanghai-Chongqing Expressway using this method was taken as the study background.The finite element model of the piers and foundation(a half structure) was established,to analyze the law of pier displacement and the bending moment of the existing piles during the new pile construction process.In the strengthening process,based on the current hydrostatic level system(HLS),two monitoring points were set in the inner side of the pier shaft, to carry out online monitoring of the settlement of the pier shafts.The results show that the con-struction process of adding new piles has no influence on the subsidence of the existing pile founda-tion,and the enlargement of the pile cap improved the bending performance of the existing piles. In the monitoring process,the influence of construction and traffic loads on the subsidence of the existing pile foundation exhibits data fluctuation on the basis of the global stability of the data.At night,when the construction was stopped and the traffic volume was small,the average settlement amount was about 1.2 mm after the elimination of elastic deformation.The application of high-precision HLS can realize the online monitoring of the pier settlement during the construction process,which can improve the strengthening efficiency and ensure the safety of the bridge in serv-ice.