上跨既有隧道围护结构小插入比深基坑开挖变形关键技术研究

Study on Key Technology of Excavation Deformation of Deep Foundation Pit with Small Insertion Ratio for Retaining Structure of Over Span Existing Tunnel

天目山路提升改造工程受既有隧道空间限制13.7 m深基坑围护结构地连墙插入基底仅1.5 m,基坑开挖过程中围护结构及周围土体的变形速率和变形量直接决定既有隧道和基坑自身安全。通过基底加固、南北两侧地连墙外主动土压区加固,分层分块开挖、混凝土支撑支护、基底抽条开挖以及型钢支撑等措施,严格控制基坑开挖变形。

Due to the space limitation of the existing tunnel,the diaphragm wall of retaining structure of 13.7 m deep foundation pit is inserted into the basement only 1.5 m.The deformation rate and deformation amount of retaining structure and surrounding soil directly determine the safety of existing tunnel and foundation pit.The deformation of foundation pit excavation is strictly controlled by the measures of basement reinforcement,active earth pressure zone reinforcement outside diaphragm wall on both sides of North and south sides,layered and block excavation,concrete support,foundation strip excavation and steel support.