Study on Unloading-wet Swelling Mechanism of Upper Arch Deformation of Mudstone Subgrade in a High-speed Railway

Mudstone subgrade may exhibit rather complicated deformation behavior under the coupling effect of unloading and wet swelling caused by excavation. To study mechanism mudstone subgrade, mudstones were sampled from NO.3 branch tunnel Badong section Zhengzhou-Wanzhou High-speed Railway a series wet-swelling tests carried out on them. We studied long-term excavation based creep test with conditions. The expansion rate complete cylinder samples was extremely low wetting drying cycle, while that soil after disintegration between 1% 10% when immersed in water. Excavation damage, groundwater infiltration, deformation, dry-wet hot-cold alternation catalyzed each other, leading to aggravation obvious increase expansibility underwater disintegration. maximum arch can be divided into three parts: rebound during short-term excavation, related time deformation. Generally, would not converge two years if support measures taken, could tend steady value certain period