Characteristics and controlling factors of frost heave in high-speed railway subgrade, Northwest China

Frost-heave of the subgrade significantly influences the stability of transportation infrastructure. In particular, small amounts of frost heave in coarse-grained subgrade fill may pose challenges to the safe operation of high-speed railway lines in cold regions. In this study, frost heave, ground temperatures, and soil moisture contents were examined at 15 test sections along Lanzhou-Xinjiang high-speed railway (LXHR), and the factors controlling the observed heave are discussed. The development of frost heave in three subgrade layers (0-0.5, 0.5-1.5, and 1.5-2.7 m depth) was examined at each section over two freezing seasons (October 2015 to September 2017). The frost depth in the subgrade reached 220-400 cm, significantly deeper than in surrounding natural ground. The frost penetrated 2.3 m of A/B group fill, a special fill material for high-speed railways. The frost heave in some sections is greater than the allowable total deformation limit of 19 mm. Most of the total frost heave (40-50%) occurred in the 50 cm thick subgrade surface layer. Residual deformation developed over the two years, which has likely resulted in increased porosity and decreased compaction and strength. Frost heaving is mainly controlled by supplies of water from the surface, from below, and laterally from adjacent ground, and the fines content of the material. The data presented provide valuable information on the construction and performance of high-speed railways in regions with seasonally-frozen ground.