Frost heaving pressure in fractured rock under different freezing paths: Multiphysics analysis

Accurate prediction of frost heaving pressure in fractured rock remains challenging for cold-region engineering due to oversimplified models neglecting seepage and freezing-path effects. This study establishes a thermal–hydraulic-mechanical (THM) coupling model for fractured rock, introducing an equivalent water expansion method to simulate ice-water phase change, seepage, and frost heaving pressure distribution. Validated through laboratory tests on crack propagation and pressure evolution, the model quantifies how freezing paths govern frost damage. Simulations demonstrate that uniform freezing (Case B) generates 16.8 % higher peak pressure than unidirectional freezing (Case A) in low-permeability sandstone, primarily due to restricted seepage pathways inhibiting pressure dissipation. Rock permeability critically modulates this effect: frost heaving pressure increases by 3.91 MPa in Case A but only 1.29 MPa in Case B when permeability drops from 10⁻¹⁶ to 10⁻¹⁹ m². Furthermore, higher elastic modulus (5–30 GPa) increases frost heaving pressure by 111.9 %–125.3 % by constraining volumetric deformation. These findings underscore the necessity of integrating freezing path effects and seepage dynamics into frost damage predictions for cold-region geotechnical engineering.