火车站地下广场内桩基托换并盖挖法施工地铁车站关键技术

Key Construction Technologies for Pile Foundation Underpinning and Metro Station Constructed by Cut and Cover Method

为保证重庆北站地铁车站施工过程中地面交通以及地下停车场的正常运行,提出火车站地下广场内桩基托换并盖挖法施工地铁车站技术:先采用桩基托换上部结构,然后以托板为基坑顶板进行盖挖施工地铁车站。既有桩基和结构的临时支撑以及托板与既有桩基、钢管柱的节点处理是工程的关键和难点:在桩基托换过程中,根据既有桩基上主梁数量设置H形临时支撑体系,并及时连接相邻临时立柱,形成整体;在托板与既有桩基节点处,凿除既有桩基基础部分混凝土,保留既有钢筋,长边方向底板部分纵筋从未凿除的桩体钻孔通过,短边纵筋绕行;钢管柱与托板节点施作时预留桩顶钢筋,将其伸入到托板中,连接成一个整体,一同灌注混凝土。现场监测最大变形为16.6 mm,说明本工程采用的桩基托换并盖挖施工技术合理可行。

During the construction of underground Metro station of Chongqing North Railway Station,the running of traffic on the ground and underground parking lot should be guaranteed. The construction technologies for pile foundation underpinning and the Metro station constructed by cut and cover method are proposed. The upper structure of the Metro station is underpinned by temporary piles and the underpinning plate is regarded as cover of cut and cover construction.The temporary support of existing piles and structures and the treatment of connection points between underpinning plate and existing foundation pile and those between underpinning plate and steel pipe column are the construction keys and difficulties of the project. During the pile foundation underpinning construction,H-shaped temporary support system is set according to amount of main beam on existing pile foundations and the adjacent temporary column should be connected in time. During the construction of connection between underpinning plate and foundation pile,part of concrete of foundation of pile foundation is cut off and the rebar is kept. During the construction of connection between underpinning plate and steel pipe column,the pile top rebar reserved is inserted into underpinning plate and then casted. The site monitored deformation results show that the above-mentioned technologies are feasible and rational.