管廊基坑长距离上跨既有地铁变形控制研究

Research on Deformation Control of Pipe Gallery Foundation Pit with Long-distance Upper Span of Existing Subway

在城市轨道交通规划建设过程中,新建管廊工程上跨轨道交通时,因管廊工程覆土较浅,一般采用明挖法施工。明挖施工过程,因开挖造成基底应力释放,会造成基底上浮隆起,基底的上浮会带动周边土体及轨道交通线路产生隆起上浮。鉴于轨道交通线路对变形的要求极为严格,如何减少基坑开挖对轨道交通线路的影响成为了基坑开挖方案选取的关键。针对此问题,采用数值模拟方法,结合工程经济性、工期等因素,对变形影响最大的基底注浆加固深度及基坑施工流水段长度进行研究,结果表明:采用基底注浆深度3 m,开挖流水段长度30 m,可明显减少本工程管廊基坑施工对既有地铁的变形影响。研究结果可为类似管廊上跨轨道交通线路工程设计或施工提供参考。

During the planning and construction of urban rail transit,when the new pipe gallery project crosses the rail transit,the open excavation method is generally used for construction because the pipe gallery project is covered with shallow soil.In the process of open excavation,the stress of the foundation base is released due to excavation,which will cause the uplift of the foundation base,and the uplift of the foundation base will drive the surrounding soil and the rail transit line to uplift.In view of the strict deformation requirements of rail transit lines,how to reduce the impact of foundation pit excavation on rail transit lines has become the key to the selection of foundation pit excavation scheme.To deal with this problem,the numerical simulation method,combined with engineering economy,construction period and other factors,is used to study the foundation grouting reinforcement depth and the length of foundation pit construction flow section,which have the greatest impact on deformation.The results show that the foundation grouting depth of 3 m and the length of excavation flow section of 30 m can significantly reduce the deformation impact of pipe gallery foundation pit construction on the existing subway.The research results can provide reference for the engineering design or construction of cross rail transit lines on similar pipe corridors.