地铁隧道下穿异型连续梁桩基托换设计

Design of Pile Foundation Underpinning for Metro Tunnels Under-passing Irregular Continuous Beam

西安北至机场城际轨道项目双线暗挖隧道下穿咸阳机场T3航站楼主线桥22-1和22-2桥墩共8根桩基,上部结构为异型变宽钢筋混凝土连续梁,为保证不中断既有桥梁交通,设计采用桩基主动托换方案,托换力达30 000 kN,托换梁计算跨度近20 m,工程复杂,设计及施工难度大。通过分析周边控制条件,介绍该托换的相关设计和部分关键控制措施,包括托换梁设计、主要监测项目控制值、施工步骤和关键控制工序等,目前该工程已施工完毕,整个托换过程符合设计预期,实践表明该托换设计合理,结构安全可靠。

As the double track tunnel of the intercity rail from Xi＇an North Railway Station to the airport passes under the main bridge,eight piles of 22-1 and 22-2 bridge piers have to be removed. The existing upper structure is irregular continuous beam. To insure that the traffic of the existing bridge is not interrupted,active pile underpinning is adopted. The underpinning force is approaching 30 000 kN,meanwhile,the span of the underpinning beam is close to 20 meters,which make the project complex and difficult to design and construct. By analyzing the ambient control factors,the paper introduces relevant designs and main controlling measures,including design of underpinning beam,control value of main monitoring projects and main construction procedures. At present,the project is completed and the whole process is in line with the design expectation. Practice shows that the underpinning process design is rational and the structure is reliable.