地铁区间隧道下穿桥梁大轴力桩基托换设计与施工

西安北客站至机场城际轨道项目全长27.33 km,其中机场站站后折返线区间隧道长256.45 m,该段暗挖隧道下穿机场T3A航站楼主线桥桩基,采用桩基托换处理。被托换的既有桥梁部为异型钢筋混凝土连续箱梁,受力复杂,结构变形敏感;桥面最大宽度35 m,桥墩墩底轴力近13 000 k N;新建托换梁跨度大于20 m,采用预应力混凝土结构,如此大跨度、大轴力的桩基托换工程实例很少。以T3A航站楼桥梁大轴力桩基托换设计为依托,通过对托换方案、关键连接节点、荷载转移机理的分析、研究,详细介绍大轴力桩基托换思路、托换梁设计、托换体系转换,给出托换关键节点的施工方案及监测技术要求,可为类似工程提供借鉴。

Design and Construction of Large Axial Force Pile Foundation Underpinning of Subway Running Tunnel Passing under Bridge

The intercity rail transit from Xi'an North Railway Station to the airport has a total length of27. 33 km,and the length of the subway running tunnel is 256. 45 m on the back-turning line after the airport station. This tunnel passes under the pile foundations of the main line bridge of the airport terminal T3 A and is excavated by underpinning beam processing. The beam of the existing bridge is underpinned in reinforced concrete continuous box,which is encountered with not only complex structural forces but also sensitive structural deformation. The maximum width of the bridge is 35 m,and the axial force at the bottom of the bridge piers is about 13 000 k N. Underpinning beam span is greater than 20 m,which is pre-stressed concrete structure. Based on the design of pile foundation underpinning,the researches on underpinning program,the key connection node and the load transfer mechanism,this article addresses in detail the concepts of large axial force pile foundation underpinning,underpinning beam design and underpinning system conversion, and presents the key nodes of underpinning construction scheme and technical requirements for monitoring,which may provide references for similar projects..