Comparison of Soil‐Freezing and Soil‐Water Characteristic Curves of Two Canadian Soils

Abstract

Core Ideas The similarity between SFCC and SWCC, and hysteresis of SFCC are reviewed. The SFCC and SWCC of two fine‐grained soils are measured and analyzed. No quantitative similarity is found between the measured SFCC and SWCC. Several concerns regarding the similarity between SFCC and SWCC are discussed. The drying–wetting and freezing–thawing cycles significantly influence the soil pore water in the vadose zone in permafrost and seasonally frozen regions. The soil‐freezing characteristic curve (SFCC) describes the relationship between unfrozen water content and subzero temperature in a soil at frozen condition. Several studies suggest that the SFCC of a frozen saturated soil is similar to soil‐water characteristic curve (SWCC), which describes the relationship between water content and suction for a soil under unfrozen unsaturated condition. In the present study, the similarity between SFCC and SWCC, and possible reasons for the hysteresis of SFCC are succinctly reviewed. The SFCC and SWCC of two Canadian soils were measured and critically interpreted to understand the fundamental behavior of SFCC in comparison with the SWCC. The observed hysteresis of SFCC for the two soils was mainly associated with the supercooling of pore water. The measured SFCC and SWCC of the two soils show quantitative dissimilarity rather than similarity. This may be attributed to the experimental limitations and possible fundamental differences between drying–wetting and freezing–thawing processes. In addition, several concerns regarding the similarity between SFCC and SWCC are discussed. The present study highlights that rigorous investigations are required for better understanding the SFCC to facilitate its use for cold‐region engineering practice applications.

Effect of freeze–thaw cycling on the soil‐freezing characteristic curve of five Canadian soils

“…The unfrozen water content of the soil specimens was measured by frequency domain reflectometry (FDR) technique without the effect of external stresses. The experimental investigation in the present study is valuable to better understand the fundamental behavior of the SFCC of fine‐grained soils with low plasticity and is a novel supplement to the previous studies by Kozlowski and Nartowska (2013) and Ren and Vanapalli (2019).…”

“…No plasticine was pasted around the overmolding of the EC‐5, as it could contribute to errors. More details regarding the calibration of the two sensors for obtaining SFCC can be found in Ren and Vanapalli (2019). The soil specimens were tightly sealed by cling wrap to prevent moisture loss during the testing period.…”

“…Ren and Vanapalli (2019) investigated the SFCC of two fine‐grained soils from Toronto, Canada. Different freezing methods (temperature paths) were imposed on these two soils for undertaking extensive experimental investigations.…”

In Situ Estimates of Freezing/Melting Point Depression in Agricultural Soils Using Permittivity and Temperature Measurements

“…Thus, in general, we expect SFC = θ(T) and STC = θ(T), but SFC ≠ STC. This hysteretic behavior can be attributed to several possible mechanisms, including supercooling effects, electrolyte concentration changes induced by the freezing/thawing processes, differences in ice-water interface curvatures during crystallization and melting, pore blocking effects, contact angle effects, changes in pore structure, and particle displacement from freezing expansion (Ren & Vanapalli, 2019).…”

“…Moreover, the effect of air is excluded; therefore, strict application of similarity theory requires the condition of saturated frozen soil. Recently, however, Ren and Vanapalli (2019) raised several concerns regarding the (lack of) similarity between the SFC and SMC.…”