下穿沈大铁路立交框架桥顶进施工的几个关键技术

辽阳市新华街下穿既有沈大铁路立交框架桥基底坐落在细砂砾土层上，加之桥址处地下位较高，框架桥的地基承载力不足，需要加强。在框架桥顶进前，用高压旋喷桩对框架基底和两侧路基基底进行加固；框架桥上方的既有铁路线采用纵、横梁架空体系加固；采用挖孔桩对既有线路基进行防护。顺利地完成了框架桥顶进施工任务，既保证了施工的安全，也保证了既有线的运营安全。详细介绍了框架桥顶进施工方案、工艺流程及采用的关键技术措施，为解决类似工程问题提供了较好的解决方法。

Key Techniques for the Jack-in Construction of the Frame-Type Flyover Underrunning the Shenyang-Dalian Railway

As the bottom of the frame-type flyover underrunning the existing Shen-Da Railway at Xinhua Street of Liaoyang City is located in the fine gravel stratum, the level of underground water at the site is rather high,and the bearing capacity of the foundation of the frame-type bridge is insufficient, the roadbed has to be strengthened. Before the frame-type bridge is jacked in,high-pressure swirly-sprayed piles are adopted to consolidate the base of the frame and the bases of the roadbeds on both sides; the existing railway over the frame-type bridge is strengthened with the overhanging supporting system of longitudinal and lateral beams; bored piles are adopted to consolidate and protect the roadbed of the existing railway line. All the above-men- tioned technical measures taken, the construction task of jacking in the frame-type bridge is smoothly completed ,with both the safe construction of the project and the safe operation of the existing railway ensured. Introduced in detail in the paper are the jack-in construction scheme for the frame-type bridge, the process flow, and key techniques adopted for the project. The paper may serve as a useful reference for solving similar engineering problems in other projects.