Civil Engineering, Architectural Engineering |
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Case study on deep excavation for metro ventilation shaft in Shanghai soft clay |
TAN Yong, KANG Zhi jun, WEI Bin, DENG Gang |
1. Geotechnical Department, Tongji University, Shanghai 200092, China; 2. China Railway Eryuan Engineering Group
Company, East China Survey and Design Co.Ltd, Shanghai 200032, China; 3. Sichuan Provincial Transport
Department Highway Planning, Survey, Design and Research Institute, Chengdu 611130, China |
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Abstract Based on the basic project information of a ventilation shaft excavation in Shanghai soft clay, the deformation behaviors of the foundation pit were studied through analysis and comparisons of field instrumentation data including displacements of retaining walls, axial strut force, column uplift and ground settlement, considering geological conditions and main construction stages. Results show that retaining walls develop significant timedependent lateral displacements due to long construction duration for casting and curing of concrete struts. Since rigid concrete struts shared in load supposed to be sustained by steel pipe struts braced at next levels, axial forces of the steel pipe struts were unable to be fully utilized. Due to the confined aquifer in deeper layers, ground experienced noticeable upheaving as excavation went deeper. The construction of diaphragm wall panels resulted in significant ground settlement, and the associated settlement influence zone was even comparable to that caused by excavation. Compared with the settlement data from metro station excavations in Shanghai, ground settlement and the relevant settlement influence zone of the case are relatively smaller.
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Published: 01 June 2016
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上海软土地区某地铁风井深基坑案例分析
针对上海软土地层中某地铁风井深基坑的工程概况,结合地质条件和现场施工工序,分析围护结构变形、支撑轴力、立柱隆起和地表沉降等现场监测数据,并与其他工程案例进行对比,研究该基坑的变形性状.研究结果表明:虽然钢筋混凝土支撑刚度较大,但其浇筑及混凝土养护时间较长,在软土流变作用下,围护结构侧向位移在支撑施工期间随时间大幅增加.由于承受较大的土压力,混凝土支撑下的钢支撑设计轴力无法被完全利用,实测轴力值偏小.由于深部承压含水层的作用,当基坑开挖深度较大时,地表经历明显的上升.地下连续墙施工将导致不容忽视地表沉降,其沉降影响范围与基坑开挖所造成的影响范围相当.与上海地区地铁车站基坑变形对比发现:本风井基坑开挖所造成的地表沉降和沉降影响范围都较小.
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