2026 Volume 21 Issue 2 Pages 299-308
A box-structure-type underpass at a new road–railway embankment crossing was constructed using the JES method, a non–open-cut underpass technique. For constructing the intermediate reinforced-concrete (RC) wall, we adopted a “temporary beam support method” to support the overburden until the wall is constructed. Because there are few precedents for this method, its influence on track displacement was uncertain; in particular, significant track movement will be considered a high risk at the time of temporary beam removal due to load transfer. To mitigate this risk, hydraulic jacks were installed at the beam supports, and a controlled preload–unload procedure was planned to regulate track displacement during both installation and removal of the temporary beams. During construction, we monitored track displacement as well as displacement of the box structure, and compared the measurements with the design values. Although the measured displacement of the box was slightly larger than the design value, the track displacement remained at or below 80% of the measured box displacement. Track movements progressed gradually during the construction period, and timely track maintenance (e.g., surfacing and lining) prevented the occurrence of large track displacements that could have affected train operations.
