洞桩法地铁车站顺行密贴下穿既有隧道方案优化研究

摘要

北京地铁15号线奥林匹克公园站下穿大屯路隧道为国内首例大断面隧道长距离顺行密贴下穿既有隧道的典型工程.该工程原设计施工方案采用四上四下八导洞PBA工法,由于存在群洞效应,且车站主体结构赋存于富水的软弱粉质粘土中,使得其施工风险极大.鉴于此,文章对该地铁车站的施工方案进行了优化,取消了原方案下侧的4个导洞,改为施作长钻孔灌注桩,并针对改进的四导洞洞桩法的工程特点,最终形成了暗挖导洞大直径桩施工工艺.在车站施工期间对既有大屯路隧道结构进行跟踪监测,监测结果表明,车站主体结构的施工方案合理,新施工工艺能够确保既有隧道结构和地铁车站施工的安全.%The Olympic Park Station crossing the existing Datun-Road tunnel covers a long distance and closely approaches an existing metro tunnel.Initially,the PBA construction method was adopted with eight pilot tunnels.In light of the tunnel group cavern effect and the surrounding soft silty clay with abundant water,the construction risks were very.Optimization of the metro station construction scheme was conducted,and the four pilot tunnels at the downside were cancelled and replaced with long drill hole grouting piles.Construction technology for a large-diame-ter pile for a bored pilot tunnel was adopted based on the engineering characters of the PBA method using four pilot tunnels.Monitoring on the Datunlu tunnel structure was performed during metro station construction and the results indicate that the construction scheme for the station′s main structure was rational; the new construction technology ensures construction safety for the existing tunnel and metro structure.