软土超大面积深基坑整坑顺作实施工程设计与实践

Engineering practice of large-scale deep foundation pit in soft soil area

软土地层中施工的深基坑工程,往往存在围护结构外侧水土压力大、变形不易控制、开挖对周边环境影响显著等问题。上海虹桥国际机场配套业务用房项目基坑面积近4万m^2,开挖深度达8.45 m,受限于建设单位造价和工期的要求,基坑采用"整坑围护+1道水平支撑体系"的围护设计方案。本基坑综合采用了分区分段开挖实施、大刚度的双半圆环结合中部对撑混凝土支撑体系、坑内设被动区土体加固等技术措施,以控制基坑开挖对周边环境的影响。实施过程中通过对换撑构造进行优化,进一步缩短了南北两侧塔楼的工期。实测数据表明,本基坑实施方案在满足业主造价和工期要求的同时,确保了基坑的安全实施。

Deep foundation pit projects in soft soil areas have the characteristics of large water and earth pressure on the outer side of the retaining structure,difficulty to control deformation,and significant impact on the surrounding environment due to excavation.The excavation area of the Shanghai Hongqiao International Airport’s Business Project was 40000 m^2,and the depth was 8.45 m.Limited by factors such as construction cost and construction period,the whole foundation pit was retained by bored pile walls which were supported by one level horizontal struts.In order to reduce the impact of the excavation on the surrounding environment,zoned excavation method,large stiffness double-half ring concrete supporting system and reinforcement of soil at the passive zone of the pit were adopted in this project.During the implementation process,by optimizing the support structure,the construction period of the towers on both sides of the north and south was further shortened.The measured data shows that the implementation plan of the foundation pit ensures the safe implementation of the foundation pit while meeting the owner’s cost and construction period requirements.