Research on the analytical methods for water-heat coupling in the frost-thaw process of canal slopes under saturated conditions

As a typical seasonal frozen soil region, the slopes of canal projects in Heilongjiang Province frequently experience significant landslide damage due to a high water table and freeze-thaw cycles. This study addresses the limitations of existing models in analyzing the hydrothermal coupling processes of saturated soil. It is based on the principles of mass conservation, energy conservation, Darcy's law, and heat conduction theory. A hydrothermal coupling model was developed for saturated soil, incorporating temperature and porosity as variables. By comparing the model's predictions with actual engineering monitoring data, the study effectively validates the model's reliability and elucidates the dynamic changes in the temperature field, water field, and ice content of the saturated canal slopes during the freeze-thaw cycle. The findings indicate that the saturated soil is filled with water in the pore spaces, the temperature field changes gradually during freezing, the water field exhibits minimal fluctuations, and the ice content increases steadily. During the thawing process, the soil rapidly becomes re-saturated, the thawing rate accelerates, the water distribution becomes uniform, and the ice content decreases swiftly to a very low level. In spring, the shallow temperature increased to 23 °C but began to drop in the fall. The upper slope temperature fell to −10 °C during winter, and the freezing depth grew as temperatures decreased. The warming in spring facilitated a rise in temperature and shallow melting. There were significant fluctuations in temperature, water, and ice content in the shallow layer of the slope (up to 1.5 m deep). At a depth of 0.5 m, the water content was 38% on day 230, dropped to 1.5% on day 257, and further decreased to 0.9% on day 303. The ice content at 0.5 m depth fell from 38.9% on day 303 to 24.4% on day 350, while at 1 m depth, it decreased from 36.4% on day 303 to 30% on day 350.