Influence on High-Speed Railway Bridge Caused by Shield Tunneling in Sandy Pebble Stratum and Its Controlling Technologies

摘要

During the construction of interval tunnel from the Tianqiao Station to the outside of Yongdingmen Station of Metro Line 8 in Beijing City, the shield machine will have to pass beneath an existing bridge. On top of the bridge, it is the Beijing-Tianjin intercity railway and the Beijing-Shanghai high-speed railway. At the project worksite, sand and gravel is the main component of ground formation. The stratum is a typical unstable one, so it is easy to induce the excavation face instability and ground subsidence or even collapse during the process of shield tunneling, which will inevitably affect the safe operation of the above railway bridge as the highspeed train has extremely strict requirements on track smoothness. Therefore, the risk of shield crossing construction is rather high. In this paper, the impact of tunnel excavation on the stress and deformation of the bridge structure as well as ground settlement, distribution of pore water pressure caused by shield tunneling were analyzed by means of three-dimensional numerical simulation. Furthermore, a series of countermeasures and monitoring schemes were proposed to ensure the safe operation of bridge before and after the shield crossing construction. The research results can not only guide the construction of this project, but also provide some reference for other similar issues.