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<p>The saline soil freeze–thaw behavior significantly affects the ecological environment and engineering in cold regions. Existing theoretical models often inadequately address the distinct mechanisms governing freezing and thawing processes. Based on nucleation and premelting theory, a predictive model is established for phase transition thresholds, by introducing Coulomb field energy, latent heat of freezing and hydrogen bond interactions, and proposing a spherical ice crystal framework. The model can explicitly distinguish between freezing nucleation and beginning premelting temperatures. Controlled freeze–thaw cycling experiments with three soil types (sand, silt, and silty clay) under varying salinity and water activity conditions validate the model’s effectiveness (<i>R</i><sup>2</sup> = 0.8927, RMSE = 0.6619&#xa0;K, MPAE = 0.2250%). How factors influence phase transition temperatures is also examined, such as surface charge density, solute concentration, and water activity. Sand shows the most pronounced temperature change due to its large pores, loose structure, and high free energy, while silt and silty clay exhibit greater freeze–thaw stability due to their finer pores and uniform structure. When the quasi-liquid layer thickness is below a critical value, dispersion forces dominate in quasi-liquid layer collapse. And high surface charge density greatly increases the supercooling degree at low solute concentrations, with a weaker surface charge effect observed at high solute concentrations. At higher salinity, reduced water activity increases nucleation activation energy, lowering freezing temperatures and increasing supercooling. This study provides a quantitative framework for understanding saline soil freeze–thaw behavior and insights into the thermodynamic processes involved, aiding soil management and engineering practices in cold regions.</p>

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Quantification of phase transition critical temperature for saline soils based on nucleation and premelting theory

  • 期刊论文

  • 发表日期：

    2025年11月25日

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  • Jiaqi Tian,
  • Zunyi Wu,
  • Yumo Wu,
  • Shuangyang Li,
  • Yuanming Lai,
  • Chong Wang

摘要

The saline soil freeze–thaw behavior significantly affects the ecological environment and engineering in cold regions. Existing theoretical models often inadequately address the distinct mechanisms governing freezing and thawing processes. Based on nucleation and premelting theory, a predictive model is established for phase transition thresholds, by introducing Coulomb field energy, latent heat of freezing and hydrogen bond interactions, and proposing a spherical ice crystal framework. The model can explicitly distinguish between freezing nucleation and beginning premelting temperatures. Controlled freeze–thaw cycling experiments with three soil types (sand, silt, and silty clay) under varying salinity and water activity conditions validate the model’s effectiveness (R2 = 0.8927, RMSE = 0.6619 K, MPAE = 0.2250%). How factors influence phase transition temperatures is also examined, such as surface charge density, solute concentration, and water activity. Sand shows the most pronounced temperature change due to its large pores, loose structure, and high free energy, while silt and silty clay exhibit greater freeze–thaw stability due to their finer pores and uniform structure. When the quasi-liquid layer thickness is below a critical value, dispersion forces dominate in quasi-liquid layer collapse. And high surface charge density greatly increases the supercooling degree at low solute concentrations, with a weaker surface charge effect observed at high solute concentrations. At higher salinity, reduced water activity increases nucleation activation energy, lowering freezing temperatures and increasing supercooling. This study provides a quantitative framework for understanding saline soil freeze–thaw behavior and insights into the thermodynamic processes involved, aiding soil management and engineering practices in cold regions.