复杂地层条件下邻近地铁超深基坑关键技术

Critical techniques for super-deep and near-subway foundation excavation under complicated formation condition

以钱塘江畔某超深基坑项目为背景,针对项目基坑开挖深度大,地层条件(地层中含有承压水、富含沼气)、周边环境条件和施工条件复杂等技术难点,介绍了基坑围护设计所采取的复杂地层超深地下连续墙技术、超深基坑施工对邻近既有轨道交通结构的保护技术、超深基坑防承压水突涌技术和超深基坑支撑优化布置等4项关键技术。项目实施结果表明,整个项目安全顺利施工,对周边环境的影响也在安全范围内,获得了显著的社会效益和经济效益,可为在复杂地层、邻近地铁条件下同类型超深基坑工程提供参考。

Based on the project of the super-deep foundation pit beside the Qiantang River,this paper introduces four critical design techniques including super-deep underground diaphragm wall under complicate formation condition,protection technique for existing subway structure adjacent to excavation of super-deep foundation pit,prevention technique against sudden welling of confined groundwater and optimization method of bracing structure arrangement,to tackle the main problems of the project which are super-deep excavation,complicated formation condition containing confined groundwater and rich in methane and adjacent to subway,complicated surrounding environment and construction condition.The practice results show that the whole construction process of the project has reached the safe and controllable target,the influence on the surrounding environment is also in the safe range,and great social and economic profits are acquired,which can provide reference for similar super-deep,near-subway foundation pit projects built under complicated formation condition.