紧邻原水管及工作井的深基坑工程设计实践

Design and Application of Deep Excavation Support adjacent to Water Supply Pipeline and its Working Well

随着城市建设的发展,新建工程基坑周边往往建筑物密布,道路管线众多,基坑项目实施对周边环境的影响与保护要求愈发严格。本文以位于上海浦东新区洋泾街道的项目为依托,该工程基坑挖深16.0 m,形状不规则,其中两侧紧邻1000~1600 mm原水管及工作井,距离基坑开挖边线约6.2 m,保护要求高。且原水管面临清障、围护体施工、基坑开挖及降水等多重影响,设计施工难度大。结合基坑规模、周边环境保护要求和土层特点,采用"两墙合一"地下连续墙+三道混凝土支撑的支护体系,地墙受力段下方设置隔水段形成悬挂式隔水帷幕以减少承压水降压对原水管的影响;此外,清障过程中在障碍物与原水管之间设置了钢板桩,并预埋跟踪注浆管;基坑开挖过程制定了详细的分区、分块开挖方案,并利用地墙压顶梁在原水管下方设置水平非约束的刚托架。通过上述设计、施工措施的结合使用,确保了基坑开挖期间对邻近原水管的保护,对同类型基坑支护设计具有指导意义。

With the development of urban construction,most excavations of new projects are surrounded by dense buildings and numerous roads and pipelines,raising more strict requirements for environmental protection.The background project is located in Yangjing subdistrict,Pudong District,Shanghai,with an excavation depth of 16 m and irregular shape.An 1000~1600 mm-in-diameter water supply pipeline and its working well were adjacent to two sides of the excavation with a distance of 6.2 m,which required strict protection.The water supply pipeline was affected by multiple processes of obstacle removal,supportting structure construction,excavation,and dewatering,which brought diffculties to scheme design and construction.Considering the excavasion scale,environmental protection requirements and soil characteristics,dual-purpose diagraph wall and three layers of strut system scheme was applied to excavation support.In order to minimiaze the influence to pipeline,depth of the diagraph wall was extended forming waterproof curtain,steel sheet pile and track-grouting were applied during obstacle removing phase,proper block division was applied during the excavation phase,and steel bracket was installed to support the pipeline.Benefiting from measures of both design and construction,the water supply pipeline was successfully protected during the excavation,which can be referred to other similar projects.