Temperature Field and Soil Deformation of Seasonally Frozen Embankment Section Under River Operating Water Levels

The stability of engineering structures in frozen regions is primarily governed by the coupled evolution of temperature, moisture migration, and stress fields driven by freeze–thaw cycles. In this study, a typical embankment section in Heilongjiang Province, a seasonally frozen region of China, is selected as a case study. To investigate the influence of river operating water levels on the spatiotemporal evolution of temperature and deformation fields in freeze–thaw cycles, this study establishes a thermo-hydro-mechanical (THM) numerical analysis framework through Python 3.8.10.-based ABAQUS secondary development. A representative annual ground-surface temperature boundary derived from ERA5-Land reanalysis data is adopted as the continuous thermal boundary condition. Two middle-drainage water states, namely water-filled drainage and water-free drainage, are considered. Design and check water levels are applied to evaluate the evolution of the temperature field, freezing depth, and deformation in freeze–thaw cycles for the embankment section soil. The predicted temperatures show seasonal trends consistent with ERA5-Land soil-temperature reanalysis data at depths of 0, 25, and 50 cm. The maximum freezing depth at the representative location on the left slope is 1.66 m, which falls within the field-measured freezing-depth range of 1.5–2.0 m. These comparisons indicate that the temperature-field and freezing-depth simulations are reasonable. Under all operating conditions, soil deformation accumulates with freeze–thaw cycles and shows a stabilization trend characterized by rapid early growth and small later increments. After the ninth cycle, the maximum deformations under the water-filled/design-level, water-filled/check-level, water-free/design-level, and water-free/check-level conditions are 15.49, 15.95, 17.81, and 18.48 mm, respectively; these values are far smaller than the reserved settlement allowance of 18 cm. Compared with the water-filled case, the deformation for the water-free case increases by approximately 15.0% under the design water level and 15.9% under the check water level. The results indicate that the condition of water-filled drainage is a dominant factor in freeze–thaw deformation, and water level fluctuation is another influencing factor.