<p>Frost heave poses a critical threat to the stability of infrastructure built on or within frozen ground. Although coarse-grained soils are generally considered less susceptible to frost heave due to their high permeability, low capillarity, and limited water retention, field observations suggest that under specific hydrogeological conditions, such soils can still experience significant frost heave. This study investigates the role of hydraulic pressure in initiating ice growth in freezing coarse materials, using sand as a representative material. Several 1D freezing tests were conducted using a custom-designed apparatus capable of simulating water recharge under hydraulic pressure. Experimental evidence indicates that the presence of hydraulic pressure notably accelerates ice lens growth, even in soils typically classified as non-frost heave susceptible. A model incorporating external water migration via unfrozen water films was developed, revealing that hydraulic gradients enhance water migration toward the ice lens via film, thus accelerating ice segregation. These findings suggest that conventional soil-replacement method employed in cold regions engineering may not be entirely effective if subjected to hydraulic pressure. Overall, this work challenges traditional assumptions regarding the frost heave resistance of coarse-grained soils and highlights the importance of incorporating hydrogeological factors into the frost-prone engineering design. The study also provides a theoretical and experimental basis for frost damage mitigation in cold-region infrastructure.</p>