京张高铁大型深基坑临近地铁设计施工管控技术

大型基坑开挖引起的卸载作用将导致基坑周边土层和建(构)筑物发生隆起变形,威胁周边建筑物的运营安全。针对京张高铁清华园隧道盾构工作井大型基坑临近地铁13号线面临的变形控制问题,从设计和施工2个方面提出管控技术要求。(1)工作井围护结构采用地下连续墙+混凝土支撑,将地表沉降和水平变形控制在0.15%基坑高度以内且小于30 mm;止水结构采用地下连续墙作为悬挂式止水帷幕,基坑底进行注浆封底;邻近城铁13号线的基坑一侧采用3排锚杆桩加固。(2)地连墙施工、基坑开挖和支撑施工及邻近地铁辅助措施施工的管理要点。

Design and Construction Control Technology of Large Deep Foundation Pit Near Metro for the Beijing-Zhangjiakou High Speed Railway

The unloading effect caused by the excavation of large foundation pit will lead to the uplift and deformation of soil layers and buildings(structures)around the pit,which will threaten the operation safety of surrounding buildings.In view of the deformation control problem faced by the large foundation pit of shield working well near Metro Line 13 in Qinghuayuan Tunnel of the Beijing-Zhangjiakou High Speed Railway,the management and control technology is put forward from the perspectives of design and construction.First,the underground diaphragm wall plus concrete support are adopted for the envelop enclosure of working well to control the surface settlement and horizontal deformation,which shall be within 0.15% of the foundation pit height and less than 30 mm;the underground diaphragm wall is used as the suspended water-stop curtain for the water-stop structure,and the bottom of foundation pit is grouted and sealed;three-row anchor piles are used to reinforce one side of the foundation pit near Metro Line 13.Second,the management points of diaphragm wall construction,foundation pit excavation,supporting construction and auxiliary measures construction of adjacent metro are emphatically introduced.