As an effective engineering countermeasure against frost heave damage in seasonally frozen regions, thermal insulation boards (TIBs) were employed in embankments. This study established a test section featuring a thermal insulation–waterproof geotextile embankment in Dingxi, Gansu Province. Temperature and water content at various positions and depths within both the thermal insulation embankment (TIE) and an ordinary embankment (OE) were monitored and compared to analyze the effectiveness of the TIB. Following the installation of the insulation layer, the temperature distribution within the embankment became more uniform. The TIB effectively impeded downward heat transfer (cold energy influx) during the winter and upward heat transfer (heat energy flux) during the warm season. However, the water content within the TIE was observed to be higher than that in the OE, with water accumulation notably occurring at the embankment toe. While the TIB successfully mitigated slope damage and superficial soil frost heave, the waterproof geotextile concurrently induced moisture accumulation at the embankment toe. Consequently, implementing complementary drainage measures is essential. In seasonally frozen areas characterized by dry weather and relatively high winter temperatures, the potential damage caused by concentrated rainfall events to embankments requires particular attention.

ABSTRACTIn desert regions, precipitation is one of the significant water sources and a key driver of ecohydrological processes over a range of spatiotemporal scales. When precipitation infiltration was combined with the original soil water, the soil water and plant water use will experience significant dynamic changes, which play an important role in the stability and sustainability of the artificial vegetation. Therefore, soil water dynamics and water use strategies of Haloxylon ammodendron were studied by the hydrogen and oxygen stable isotope technique in this study. The results showed that precipitation in the desert soil was mainly in the form of piston flow, and the precipitation that led to the significant increase of infiltration and recharge was different in different precipitation events. The precipitation of 12.8 and 19.6 mm can make the surface soil water sufficient and continue to penetrate into the deep soil, and the duration of soil water response and the recharge depth were much longer and deeper than those for 4.4 and 7.8 mm events. In addition, the H. ammodendron mainly relied on stable and abundant deep soil water and groundwater. The water use source of H. ammodendron showed no significant response to 4.4 and 7.8 mm precipitation. However, a significant difference in water source proportion occurred before and after 19.6 mm of precipitation. The use proportion of shallow soil water increased from 10.7% to 24.2%, while that of groundwater decreased from 48.8% to 23.2%. Therefore, we concluded that precipitation levels have a major impact on soil water at various depths; in particular, heavy precipitation has a significant impact on deep soil water that deeply controlled the survival of the H. ammodendron plantation. These results offer an essential theoretical foundation for vegetation restoration and sustainability in arid regions.

Abstract Soil freezing characteristics are predominantly governed by the mechanism of bound water, which essentially constitutes a multicomponent cations distribution within the electrical double‐layer (EDL) on clay particles. The freezing behavior of bound water is determined by two critical factors: (a) the distribution characteristics of cation solutions; (b) the quantitative relationship between cation concentration and freezing point. Although EDL‐based unfrozen water model has been proposed, the freezing characteristics of multicomponent cation solutions remain poorly understood. Our findings indicate that: (a) The synergistic effect of multicomponent cations increases the freezing point depression coefficient of bound water (i.e., the degree of freezing point lowering per unit concentration) by several‐fold compared to NaCl solution; (b) For typical mineral soils with low Na+ content (<15%), a linear freezing point depression equation can accurately characterize the freezing process of multicomponent cation solutions; (c) typical mineral soils exhibit highly similar cation distribution characteristics. By integrating the freezing point depression equation with EDL theory, this study not only improves the EDL‐based unfrozen water model but also develops a parameterized model applicable to typical mineral soils, and elucidating the intrinsic mechanisms of the model's robustness. Validation using measured data from 12 typical soil types demonstrates that this parameterized model can accurately predict unfrozen water content in sands, silts, and clays with low to moderate clay content within the temperature range of −0.263°C to −20°C. The study establishes a theoretical framework distinct from conventional water potential theory, thereby deepening the understanding of freezing characteristics in frozen soils.