Pile-plate structure subgrade performance in seasonally frozen regions with freeze-thaw cycles

The pile-plate structure has proven highly effective support for high-speed railway subgrades, particularly in poor geological conditions. Although its efficacy in non-frozen regions is well-established, its potential in frozen regions remains underexplored. In seasonally frozen areas, F-T (freeze-thaw) cycles threaten subgrade stability, necessitating research on pile-plate structure's behavior under such conditions. To address this challenge, a scaled model experiment was conducted on a silty sand foundation, simulating F-T cycles using temperature control devices. Key parameters, including soil temperature, frozen depth, and displacement, were systematically monitored. Results indicate that the bearing plate functions as an effective insulation layer, significantly reducing sub-zero temperature penetration. Additionally, the anchoring action of the piles mitigates frost heave in the foundation soil, while the plate middle restrains soil deformation more effectively due to increased constraint. The thermal insulation provided by the plate maintains higher soil temperatures, delaying the onset of freezing. By the end of each freezing stage, the vertical displacement in the natural subgrade is approximately 4 times greater than that beneath the pile-plate structure. Furthermore, the frost depth is about 1.3–1.4 times and 1.6–4.9 times greater than that measured below the plate edge and middle, respectively. These insights contribute to the development of more resilient designs for high-speed railway subgrades in seasonally frozen regions, offering engineers a robust, scientifically-backed foundation for future infrastructure projects.