How does train heaving impact track geometry?

Train heaving, specifically frost heave, impacts track geometry by causing uneven vertical displacement of the track structure, leading to irregularities in the track surface and alignment. Frost heave occurs when water in the subgrade (the soil layer beneath the ballast) freezes and expands, causing the ground to lift. This lifting can be uneven, with some sections of track heaving more than others, resulting in irregularities in the track surface and alignment. This uneven displacement can cause dips and humps in the track, which can reduce ride quality and increase stress on the rails and wheels. Frost heave can also cause lateral displacement of the track, leading to changes in gauge (the distance between the rails) and alignment. These changes in track geometry can reduce train speeds and increase the risk of derailment. For example, in cold climates, sections of track that are located in areas with poor drainage or high water tables are particularly susceptible to frost heave. The uneven lifting of the track can cause significant irregularities in the track surface, requiring frequent maintenance to restore the track geometry. Therefore, mitigating frost heave through improved drainage, subgrade stabilization, and the use of frost-resistant materials is essential for maintaining track geometry and ensuring safe train operation in cold climates.