The frozen soil processes and their interaction with the environment in the vadose zone of cold regions is vital in both agricultural and engineering practice applications. In a frozen soil, unfrozen water and pore ice coexist. The relationship between the unfrozen water content and subzero temperature is widely known as the soil‐freezing characteristic curve (SFCC). The SFCC is a valuable tool for predicting the hydromechanical properties and for modeling the coupled thermal–hydraulic–mechanical–chemical process in frozen soils. In spite of its importance, the effect of freeze–thaw (F–T) cycling on SFCC has not been well investigated or understood. In this technical note, the effect of F–T cycles on the SFCC of five soils from cold regions of Canada were investigated. The SFCC (including both freezing and thawing branches) of the five soils for different F–T cycles were measured using frequency domain reflectometry (FDR) technique. The experimental results suggest that the effect of F–T cycles on the SFCC of the five soils is not significant. Such a behavior may be attributed to the destruction of soil structure during the saturation process. However, all the five soils’ SFCC exhibited hysteresis behavior for all the F–T cycles. The results of the study are valuable and contribute towards better understanding of the fundamental behavior of SFCC of various cold region soils.

中文翻译：

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冻融循环对加拿大五种土壤冻结特性曲线的影响

在寒冷地区的渗流带中，冻土过程及其与环境的相互作用对于农业和工程实践应用都至关重要。在冻结的土壤中，未冻结的水和孔隙冰共存。未冻结的水分含量与零度以下温度之间的关系被广泛称为土壤冻结特征曲线（SFCC）。SFCC是预测冰冻土的水力学性质和建立热-水-力-化学-化学耦合过程的有价值的工具。尽管它很重要，但冻融（F–T）循环对SFCC的影响尚未得到充分研究或了解。在本技术说明中，研究了F–T循环对加拿大寒冷地区的五种土壤的SFCC的影响。使用频域反射法（FDR）技术测量了五种土壤在不同F-T循环中的SFCC（包括冻结和解冻分支）。实验结果表明，FT循环对5种土壤的SFCC的影响不显着。这种行为可能归因于饱和过程中土壤结构的破坏。然而，在所有的F–T循环中，所有五种土壤的SFCC都表现出滞后行为。研究结果是有价值的，有助于更好地理解各种寒冷地区土壤的SFCC基本行为。这种行为可能归因于饱和过程中土壤结构的破坏。然而，在所有的F–T循环中，所有五种土壤的SFCC都表现出滞后行为。研究结果是有价值的，有助于更好地理解各种寒冷地区土壤的SFCC基本行为。这种行为可能归因于饱和过程中土壤结构的破坏。然而，在所有的F–T循环中，所有五种土壤的SFCC都表现出滞后行为。研究结果是有价值的，有助于更好地理解各种寒冷地区土壤的SFCC基本行为。