A dynamic soil freezing characteristic curve model for frozen soil

The soil freezing characteristic curve (SFCC) plays a fundamental role in comprehending thermo-hydraulic behavior and numerical simulation of frozen soil. This study proposes a dynamic model to uniformly express SFCCs amidst varying total water contents throughout the freezing-thawing process. Firstly, a general model is proposed, wherein the unfrozen water content at arbitrary temperature is determined as the lesser of the current total water content and the reference value derived from saturated SFCC. The dynamic performance of this model is verified through test data. Subsequently, in accordance with electric double layer (EDL) theory, the theoretical residual and minimum temperatures in SFCC are calculated to be −14.5 °C to −20 °C for clay particles and −260 °C, respectively. To ensure that the SFCC curve ends at minimum temperature, a correction function is introduced into the general model. Furthermore, a simplified dynamic model is proposed and investigated, necessitating only three parameters inherited from the general model. Additionally, both general and simplified models are evaluated based on a test database and proven to fit the test data exactly across the entire temperature range. Typical recommended parameter values for various types of soils are summarized. Overall, this study provides not only a theoretical basis for most empirical equations but also proposes a new and more general equation to describe the SFCC.