To investigate the short-term variation patterns and influencing factors of the temperature field for composite roadbeds in permafrost regions, four finite-element models of roadbeds were established using COMSOL Multiphysics software, and numerical simulations and analyses were conducted, with the following results. The subgrade is filled in July and, in the first year of filling, the thermal effect causes the four kinds of subgrade freezing front to move down. The center of the heat-pipe subgrade has the highest soil temperature. The thawing process is significantly pronounced, showing an obvious shady–sunny slope effect, and the negative effect of the heat pipe is more obvious. Raising the height of the protection path has little effect on the temperature field in the center of the roadbed but it will cause the soil temperature of the sunny slope to rise, exacerbating the degree of thawing and making thermal thaw slumping more likely to occur. The higher the temperature of the subgrade filling, the higher will be the average temperature and the temperature peak of the underlying frozen soil in the subgrade; the temperature change at the center of the subgrade is more significant than that at the foot of the sunny slope. Therefore, in cold-region construction projects, the height of the insulation shield and the initial temperature of the filling material should be reasonably controlled to prevent more significant thawing of the underlying frozen soil in the short term.
Han et al. (Thu,) studied this question.