Investigation on unfrozen water content models of freezing soils

Abstract

Unfrozen water content is a significant hydro-thermal property in numerical modeling in cold regions. Although numerous models have been developed to mimic the variation of unfrozen water content with subzero temperature, comprehensive evaluation of unfrozen water content models is scarce. This study collected a total of 29 models and divided them into four categories, namely, theoretical models, soil water characteristic curve (SWCC)-based models, empirical models, and estimation models. These models were evaluated with 1278 experimental points from 16 studies covering multiple soil types, including 24 clays, 18 silty clays, 7 silts, 19 sands, and 10 sandstones. Root mean square error and average deviations were applied to judge the performance of these models. Most unfrozen water content models can well simulate the relationship between unfrozen water content and subzero temperature. Among the aforementioned four categories of unfrozen water content models, Lizhm et al. model, Fredlund and Xing (C=1)-Wen model, Kozlowski empirical model, and Kozlowski estimation model performed best in their respective categories. Compared to the rest three categories, estimation models can be applied to predict the variation of unfrozen water content with subzero temperature by some easy-to-obtain soil physical parameters and provide guidance for the development of unfrozen water content models.

A Novel Generalized Clapeyron Equation-Based Model for Capturing the Soil Freezing Characteristics Curve of Saline Soil: Validation by Small Sample Lab and Field Experiments

“…What is more, the presence of salt will further complicate the influence of freezing and thawing on soil structure and landscape evolution [6]. Therefore, this study focuses on the freezing process of saline soil, which is prevalent in the middle and high latitudes of Asia [12][13][14][15], Europe [16,17], and America [1,12]. However, characterizing the ice-water phase change in saline soil is still challenging due to the complicated interaction between the soil matric potential and the solute potential [13,14].…”

“…The soil freezing characteristic curve (SFCC) describes the equilibrium state of the ice-water phase change [15] by illustrating the decline in the liquid volume ratio in the pore space as temperature decreases during the ice-water phase change [16]. As summarized by Bi et al [17], the models described by the SFCC can be categorized into four types: the theoretical models [18][19][20], the SWCC-based models [12,[21][22][23][24][25], the empirical models [26][27][28][29][30][31][32][33][34][35][36][37], and the estimation models [31,38,39]. However, only a few SFCC models have considered the presence of salt or solute [1,14,[40][41][42][43][44][45][46].…”

“…Wu et al [14] proposed an improved empirical model by substituting the freezing point of the SFCC model proposed by Xu et al [47] with the freezing point of the salt solution according to Banin and Anderson [48]. The empirical models could well capture the experimental soils [27] but might be hard to apply to soils of other types [17]. For the theoretical models [43,44], Wang et al [43] proposed a phase composition model based on the assumption that soil particles are spheres and the unfrozen water covers the spherical soil particles as a thin film.…”

“…Wan and Yang [44] built a theoretical model considering the soil pore size distribution and the effect of ion concentrations. The theoretical models have gained prominence in recent years [39] because they have clear physical meanings which are based on the pore size distribution of soil [17,18,44,49] or the surface effects of soil particles [18,43,50,51]. However, theoretical models usually possess complicated equations [18][19][20]50].…”

Mechanism of Unfrozen Water Content Evolution during Melting of Cryogenic Frozen Coal Body Based on 2D NMR

“…Not all of the liquid water in coal is converted to solid ice when the coal is frozen by a low-temperature medium; due to surface adsorption and pore capillary action in the coal matrix, a certain amount of liquid water is always maintained, which is called unfrozen water [14,15]. The unfrozen water is deposited between the ice crystals and the coal matrix in the form of water film, which has a great influence on the macroscopic properties of the frozen coal [16,17]. As an important part of low-temperature fracturing, the melting process, compared with the freezing process, is characterized by a long time, complex pore evolution and significant changes in coal physical properties.…”