上跨规划地铁线路的软土深基坑支护设计实践

Design Practice of Deep Excavation in Soft Soil Above Subway Lines

为既有或规划待建的地铁隧道所贯穿的基坑工程越来越多,其设计与施工一直是行业难题。结合杭州市区某上跨规划地铁线路的软土深基坑工程实例,详细介绍并分析了工程特点、基坑支护设计选型以及监测结果。针对地铁隧道下穿既有基坑的若干设计技术难点,包括基坑变形控制、端头土体加固、预留盾构穿越通道、减少交叉施工影响等,总结了几点设计关键技术。监测结果表明,基坑支护选型合理,对周边环境影响较小;且地下室底板浇筑完成以后,地铁隧道盾构再穿越对基坑变形控制较为有利,对于类似的基坑支护工程的设计和施工具有一定参考意义。

There are more and more deep excavation projects directly above or very close to the existing or planned subway tunnels.The design and construction aspects of deep excavation support have always a challenge in the industry.This paper presents a case history of deep excavation in soft soils directly above the planned subway line in Hangzhou urban area.The engineering characteristics,deep excavation support design selection and monitoring results are introduced in detail in the paper.Technical difficulties in the design of subway tunnel underneath the existing excavated foundation,including deformation control of supporting structures,soil strengthening at the bottom of excavation,reservation of the shielded tunnel crossing pass and reduction of the influence of various construction stages are also summarized.The monitoring results show that the selection of deep excavation support system is reasonable and its impact to the surrounding environment is minimal.After the basement floor was completed,the shielded tunnel crossing is favorable to the control of deep excavation deformation.