Experimental and Numerical Modeling of the Freeze–thaw Response of U-Shaped Channel Lining on Sulfate Saline Soil Foundation

Under the influence of seasonal freeze-thaw cycles, the concrete lining of channels situated on saline soil foundations is highly vulnerable to an array of deleterious phenomena, such as frost heave, salt expansion, and corrosion. To investigate the synergistic interplay among saline soil substrates, U-shaped channel lining structures, and ambient temperatures during freeze-thaw cycles, a novel Hydraulic-Thermal-Salt-Mechanical (HTSM) model is established in this study. The HTSM model elucidates the migration of moisture and salt solute, ice-water phase transitions, and sodium sulfate crystallization within unsaturated saline soils throughout the freeze-thaw cycles. It considers the variations in volume and pore solution volume before and after the phase transition of sodium sulfate. Temperature and salt frost heaving force measurements obtained from outdoor freeze-thaw cycles are compared with numerical simulation results to validate the efficacy of the HTSM model and investigate the distribution patterns of salt frost heaving force (frost swelling force) along the channel. The results showed that the frost swelling force and depth exhibit a great linear relationship and the maximum stress of the U-shaped channel appears at the bottom of the channel, highlighting the good arching force characteristics of the U-shaped structure which prove that bottom of the channel is also the most prone to fracture. Significantly, the initial water content significantly impacts the frost swelling force—it increases by 4% while the frost swelling force increases by 76%. Comparing the numerical simulation results of temperature variations, moisture changes, and salt-frost heaving forces with the outdoor experimental data, it is evident that the proposed HTSM model effectively simulates the salt-frost heaving patterns observed in U-shaped channel linings.