Determination of Substructure and Sub-ballast Layer Thickness of High-Speed Railway

The thickness of trackbed layers plays a crucial role in distributing train loads to ensure that stresses on the sub-ballast and substructure remain within acceptable limits. Vietnam is currently studying the construction of a high-speed railway (HSR) on the North-South axis, with two scenarios involving train axle loads of either 17 tons/axle or 22.5 tons/axle. This study focuses on determining the appropriate thickness for the sub-ballast and substructure layers to accommodate these axle loads. Using analytical methods, calculations were performed to determine optimal trackbed thickness. The results indicate that for an axle load of 17 tons, the substructure thickness should be approximately 1.75 m, while the sub-ballast layer should be around 0.27 m. In contrast, for axle load of 22.5 tons, the substructure thickness increases to about 1.94 m, and the sub-ballast layer thickness grows to approximately 0.36 m. These variations highlight the impact of axle load on trackbed design. The substructure layer's thickness is particularly important as it directly influences stress distribution throughout the trackbed. A well-designed trackbed ensures the structural integrity of the railway system, sufficient load-bearing capacity, and cost-effective construction. Proper determination of layer thickness is essential to balance performance, durability, and economic feasibility in high-speed railway infrastructure projects. This research provides a foundation for optimizing trackbed designs in Vietnam's high-speed railway scenarios, contributing to safer and more efficient railway operations.