两侧双基坑开挖对密贴既有线路基变形的影响

Effect of excavation of double foundation pits on deformation of existing railway subgrade

本文以北京某新建地铁车站双基坑开挖密贴既有线工程为背景,利用FLAC3D对双基坑开挖过程进行模拟,分析了基坑开挖对既有线路基变形的影响,并和现场监测结果进行对比。结果表明:基坑开挖工序直接影响既有线路基变形,且距基坑越近,沉降值越大;双基坑开挖对既有线路基变形的影响是叠加的,西侧基坑的开挖首先引起西侧路基下沉,此时东侧路基整体上浮;东侧基坑开挖过程中,西侧路基继续下沉,但沉降最终趋于稳定,东侧路基变形从上浮逐渐转变为下沉,且随着开挖的进行沉降不断增大。现采取的对既有线路基的支护措施和施工工序能有效控制路基沉降,确保既有线安全运营;研究结果可为以后类似工程的优化和施工提供有利的参考和借鉴。

Based on the construction of a new metro station in Beijing,the excavation process of two foundation pits closely to it were simulated by FLAC3 D,the influence of foundation pit excavation on the deformation of existing metro subgrade was analyzed and compared with the field monitoring results.The results show that the excavation process of foundation pits directly affect the deformation of existing subgrade.The closer to the foundation pit,the larger the settlement value of two foundation pits.The influence of excavation on the settlement of subgrade is superimposed,the settlement induced by the western foundation pit excavation was observed firstly on the western subgrade,while the eastern subgrade floats at the same time.During the excavation of the eastern foundation pit,the western subgrade continues to sink with the reduced velocity the eastern subgrade deformation changes from floating to sinking,and the sinking gradually increases with the excavation.The supporting measures and construction procedures adopted in this project can effectively control the settlement of subgrade and ensure the safety operation of existing line.The results can also provide useful reference for the optimization and construction of similar projects in the future.