四线叠加超深群坑施工关键技术研究

Study on Key Techniques of Four-line Superimposed Ultra-deep Group Pit Construction

为了缓解日益拥堵的交通情况,由地下轨道交通、地下快速道路和地面道路组成的多线叠加的地下交通枢纽系统应运而生。同时随着基坑深度的增加,地下连续墙进入更深的土层,对施工技术和施工装备形成了全新挑战。通过上海轨道交通14号线、18号线昌邑路车站工程案例,对四线叠加超深群坑施工过程中的分坑施工、超深地下连续墙施工、封堵墙拆除施工、地下水控制等施工技术进行了分析,提出软硬复合地层地下连续墙“抓铣结合”施工工艺、66 m钢筋笼“分节吊装”的施工思路,还进一步研究了“双帷幕”止水体系在复杂水文条件下对超深基坑周边环境的保护性。结果表明,本项目地下连续墙的垂直度表现良好,地下连续墙钢筋笼均一次成形、一次入槽、一次浇筑完成、无明显渗漏点,同时基坑开挖及上撑速度加快,地下水也得到了良好的控制,可为同类型地下交通枢纽工程提供参考。

To alleviate increasingly congested traffic conditions,a multi-line superimposed underground transportation hub system,consisting of underground rail transit,underground expressways,and ground roads,is proposed.As the depth of the foundation pit increases,the diaphragm wall enters deeper soil layers,posing a new challenge to construction techniques and equipment.Based on the engineering case of Changyi Road Station of Shanghai Rail Transit Line 14 and Line 18,the construction techniques for the four-line superimposed ultra-deep group pit are analyzed,including aspects such as pit-dividing construction,the construction of ultra-deep diaphragm walls,the demolition of the blocking wall,and groundwater control.Additionally,the construction technique of the'grasping and milling combination'for diaphragm walls in soft and hard composite strata is proposed,as well as the'segmented hoisting'technique for 66 m steel cages.Furthermore,the protection offered by the'double curtain'water stop system on the surrounding environment of ultra-deep foundation pits under complex hydrological conditions is further studied.The results indicate that the verticality of the project's diaphragm wall is good,and the reinforcement cages for the diaphragm walls are formed,placed,and cast in one single operation,with no obvious leakage points observed.The speed of foundation pit excavation and support is accelerated,and groundwater is well controlled,providing a reference for similar underground transportation hub projects.