超大型盖挖逆作法软土深基坑支护设计与实践

Design and practice of Super large deep foundation pit support in soft soil by top-down excavation method

以福州市中心城区某超大型地下空间工程为例,针对该基坑工程存在的技术难题,在设计上采用盖挖逆作法方案。围护结构未采用常用的地下连续墙,而是选取相对经济的混凝土灌注桩;止水帷幕根据周边环境和地质情况,采用三轴水泥搅拌桩、双轮铣深搅(CSM)止水帷幕、MSJ大直径旋喷桩、RD工法高垂直度咬合桩等新工艺;在坑内设置了止水分隔带,将大型基坑分成几个独立的止水区域,分块施工抽水。监测结果表明,在基坑施工期间,支护结构和周边环境变形正常,均满足规范要求。该工程逆作法的成功应用,可为类似超大软土深基坑工程提供借鉴和参考。

In this paper,a super-large underground space project in the central city of Fuzhou is taken as an example,in view of the technical problems existing in the foundation pit engineering,the cover-excavation top-down construction method is adopted in the design.According to the surrounding environment and geological conditions,new technologies such as triaxial cement mixing pile,CSM waterproof curtain,MSJ large diameter jet grouting pile,RD method high verticality occlusion pile and so on are adopted;A water stop separation zone is set up in the pit to divide the large foundation pit into several independent water stop areas for block construction and pumping.The monitoring results show that the deformation of the supporting structure and the surrounding environment is normal during the construction of the foundation pit,which meets the requirements of the specifications,and that the design and construction scheme of the project is successful and feasible.The successful application of the reverse construction method can provide reference for similar deep foundation pit engineering in super-large soft soil.