紧邻地铁站的超大深基坑逆作法变形规律研究

Research on deformation law of over-sized deep foundation pit which is adjacent to metro station and constructed by top-down method

某超大深基坑紧邻城市2条地铁线交汇处的换乘站,周围环境复杂,基坑施工难度大,因此基坑支护结构施工顺利及对相邻地铁站的变形控制成为工程成败的关键。文章结合基坑工程2种施工方案,利用有限元软件MIDAS GTS建立三维有限元模型,研究了基坑盖挖逆作法施工对地表沉降、支护结构和相邻地铁站的变形和受力影响,得出影响逆作法施工的相关因素,并提出相关解决措施与建议。采用盖挖逆作法施工能够较好地控制基坑支护结构的变形,同时减小对地表和地铁站的影响。综合考虑基坑施工对围护结构、地表和地铁换乘站的影响,首层土体暗挖法要优于明挖法,但是暗挖法对围护结构强度和刚度要求高,特别是楼板临时洞口处。所得相关结论和建议可供设计和施工参考。

The over-sized deep foundation pit is adjacent to the metro interchange station located at the intersec-tion of two subway lines .Considering the complexity of the surrounding environment and the difficulty of foundation construction ,the construction of foundation pit retaining structure as well as the deformation con-trol of the adjacent metro interchange station is the key to this project .According to two kinds of construction schemes of foundation pit engineering ,three-dimensional finite element model is established by the finite ele-ment software MIDAS GTS .The effect of top-down construction method on ground surface settlement and the deformation and stress of retaining structure and adjacent metro interchange station is studied .Finally the factors influencing the top-dow n construction are summarized ,and the relevant measures and suggestions are proposed .The top-down method can effectively control the deformation of retaining structure and reduce the impact on ground surface and the metro interchange station .Considering the impact of the foundation pit con-struction on retaining structure ,ground surface and the metro interchange station ,the subsurface excavation method is superior to the open-cut method in view of the first layer of soil .But the subsurface excavation method has high requirements of strength and stiffness of retaining structure ,especially near the hole at the floor .Relevant conclusions and suggestions could be reference for the design and construction of similar pro-jects .