摘要
某深基坑场地位于南京河漫滩地貌,场地上部存在流塑状淤泥质粉质黏土,下部存在深厚的具有承压性强透水卵砾石层。基坑呈狭长矩形,东西向长约250m,南北向宽约50m,基坑深度约为11~14m。基坑南侧紧邻既有敏感建筑,北侧紧邻天然气、供水等重要的市政管线。经方案比选结合帷幕现场试桩,对基坑采用支护桩+混凝土内支撑支护体系,基坑地下水控制采用三轴水泥土搅拌桩帷幕止水+坑内疏干方案。充分考虑狭长形基坑受力与变形特点,结合基坑环境变形控制要求,对基坑南侧长边支护和止水采取了加强设计。为规避基坑全面开挖产生的长边效应,基坑开挖和地下结构施工采用分区、分坑、分时方案。针对超长帷幕穿越不同地层,通过试桩施工优化并确定了合理有效的施工参数。基坑检测与监测结果表明,帷幕桩连续完整、强度满足设计要求,基坑支护结构及周边环境变形满足设计与规范要求。该基坑工程的设计与施工情况可供类似基坑工程参考。
A deep foundation pit is situated in the flood plain of Nanjing.The geological condition is that the flowing plastic mucky silty clay is distributed in the upper part,and a deep gravel layer with high permeability and strong bearing ability is distributed in the lower part.The foundation pit is a narrow cuboid with 250 m in east-west length,50 m in north-south width,and 11~14 m in depth.Some adjacent sensitive buildings are existed in the south side of the foundation pit while some important municipal pipelines including natural gas pipeline and water supply pipe are close to the north side of the foundation pit.Based on the scheme comparison and pile testing,the combined supporting system composed of retaining pile and concrete inner support was adopted.To effectively control the underground water level,the triaxial cement-soil mixing column was taken as the waterproof curtain and the drainage was carried out through the dewatering well inside the foundation pit.Considering the mechanical property of narrow foundation pit and deformation control of the surrounding environment,the supporting structure and waterproof curtain in the south of the foundation pit were enhanced.A specific scheme of subarea and time-sharing construction was conducted to avoid the shape effect induced by pit excavation.The rational construction parameters for ultra-long waterproof curtain crossing different stratums were determined using pile testing.The detection and monitoring results show that the waterproof curtain is continuous and integral.Both the strength and deformation of structure and surrounding environment fit the requirement of design and specification.These situations can be a reference for the similar foundation pit engineering.
作者
方庆
陈胜
潘忱
刘雪珠
Fang Qing;Chen Sheng;Pan Chen;Liu Xuezhu(Jiangsu Geotechnical Engineering Company,Nanjing 210000,Jiangsu,China)
出处
《岩土工程技术》
2024年第4期453-458,共6页
Geotechnical Engineering Technique
关键词
复杂敏感环境
深厚卵砾石层
止水帷幕
长边效应
分坑施工
变形控制
complex sensitive environment
deep layer of gravel
waterproof curtain
long side effect
pit dividing construction
deformation control
