Laboratory study on heat, moisture, and deformation behaviors of seasonally frozen soil under the influence of solar radiation and underlying surface colors

Seasonally frozen soil (SFS) is a critical component of the Cryosphere, and its heat-moisture-deformation characteristics during freeze-thaw processes greatly affect ecosystems, climate, and infrastructure stability. The influence of solar radiation and underlying surface colors on heat exchange between the atmosphere and soil, and SFS development, remains incompletely understood. A unidirectional freezing-thawing test system that considers solar radiation was developed. Subsequently, soil unidirectional freezing-thawing tests were conducted under varying solar radiation intensities and surface colors, and variations in heat flux, temperature, water content, and deformation were monitored. Finally, the effects of solar radiation and surface color on surface thermal response and soil heat-moisture-deformation behaviors were discussed. The results show that solar radiation and highabsorptivity surfaces can increase surface heat flux and convective heat flux, and linearly raise surface temperature. The small heat flux difference at night under different conditions indicates that soil ice-water phase change effectively stores solar energy, slowing down freezing depth development and delaying rapid and stable frost heave onset, ultimately reducing frost heave. Solar radiation causes a significant temperature increase during initial freezing and melting periods, yet its effect decreases notably in other freezing periods. Soil heatwater-deformation characteristics fluctuate due to solar radiation and diurnal soil freeze-thaw cycles exhibit cumulative water migration. Daily maximum solar radiation of 168 W/m(2) and 308 W/m(2) can cause heatmoisture fluctuations in SFS at depths of 6 cm and 11 cm, respectively. The research findings offer valuable insights into the formation, development, and use of solar radiation to mitigate frost heave in SFS.