Soil Freezing Research Articles

Optimizing CLM4.5 simulations of the active layer: The role of gravel in Tibetan Plateau permafrost

Gravel is widely distributed in soils of the Tibetan Plateau (TP), where permafrost also occurs over approximately half of the total area. Gravel has different thermal and hydrological properties to those of fine-grained soils, which may have a considerable impact on hydrothermal transport within TP soils. However, few land models consider gravel. Here, we incorporated the thermal and hydraulic properties of gravel into the Community Land Model and explored the effect of differing gravel contents on land surface processes. We found that all parameters affecting soil hydrothermal transport were sensitive to gravel content. Soil thermal and hydraulic conductivities increased with increasing gravel content, ultimately leading to variations in soil temperature, soil water content, and radiation fluxes with changing gravel content. Soil containing gravel exhibited higher infiltration and greater total water storage capacities. We also compared different model schemes in an attempt to improve the simulation of active layers in permafrost regions with high gravel content on the TP. The scheme in which both gravel and freeze–thaw parameterizations were applied (i.e., SP3) improved both the latent heat flux and ground heat flux transfer. The SP3 scheme performed best in terms of soil temperature and soil moisture simulations at both the Nagqu and Madoi field stations, demonstrating a particular ability to better characterize soil moisture processes as a function of temperature during soil freezing and thawing.

Relationship between soil structure and hydrological properties of the active layer in the permafrost region of the Qinghai–Tibet Plateau based on fractal theory

Soil structure and hydrological properties influence ecosystem stability and hydrological cycles. Fractal theory has been widely used in the quantitative analysis of soil particle-size distribution (PSD), aggregate and pore distribution, and evaluation of soil degradation, desertification, and wind erosion. However, the complex relationships between soil physiochemical properties and soil hydrological processes based on fractal theory have not been thoroughly investigated. This study focused on the correlation among soil structure, physicochemical properties, and hydrological properties in the active layers of various soil types and vegetation coverages in the permafrost region of the Qinghai–Tibet Plateau (QTP) using the principles of fractal theory. The results showed that the fractal dimension of soil PSD (DPSD) in the active layer of the QTP was predominantly within the range of 2.13–2.70, which is notably smaller than the fractal dimension of the soil water retention curve (DWRC: 2.72–2.93). With decreased vegetation coverage, the alpine soil particles exhibit gradual fineness, increasing the DPSD. Soil physicochemical properties were affected by the interactions among internal factors and the external environment, such as geographical locations, slope orientations, vegetation coverages, and soil freeze–thaw cycles. The results of correlation analysis indicated that the fractal dimension of PSD and the soil water retention curve (WRC) were significantly correlated with soil textural, physicochemical, and hydraulic properties, particularly in clay, silt, and very fine sand content. Finally, a fractal model of WRC in the permafrost region was established based on DPSD and WRC parameters of the Gardner and van Genuchten models. The study provides an improved perspective for revealing the transport process and influencing mechanism of soil water and salt in the active layer of the QTP and a more accurate prediction of soil physiochemical and hydrological properties for climate warming and wetting.

Dynamic characteristics of soil pore structure and water-heat variations during freeze-thaw process

Freeze-thaw processes in cold regions alter soil pore structure and properties, leading to engineering geological issues. Soil pores are crucial, but research on their changes and freeze-thaw impacts is limited. This study used MRI-Cryogenic Soil Moisture Analyzer (MRI-CSMA) to explore pore structure, water, and temperature changes in saturated loess during freeze-thaw, and Scanning Electron Microscopy (SEM) to compare changes before and after. The results indicate that during the freezing process, the temperature in the frozen zone of the soil sample exhibited a staged change characterized by rapid cooling, transitional cooling, and stabilization at low temperatures, while the temperature decrease in the unfrozen zone showed no significant stages. Freeze-thaw action significantly affected the macropores and mesopores in the frozen zone, with an average increase of 15 % in macropores, a decrease of 16 % in mesopores, and minimal change in micropores (about a 1 % increase). In the unfrozen zone, there was a slight increase in micropores and mesopores (2 % and 3 %, respectively), and a 4 % decrease in macropores. Furthermore, during the freezing process, macropores in the unfrozen zone gradually decreased, while mesopores and micropores increased, leading to soil structure densification and promoting water migration towards the freezing front. This resulted in an initial increase followed by a decrease in water content near the freezing front during the early stages of freezing, confirming the view that pore structure compression drives water migration in the early stages of soil freezing. This study provides important insights for addressing engineering geological issues in cold regions under freeze-thaw conditions.

High-resolution soil moisture and freeze–thaw records toward the third pole using GNSS-R reconstructed observations during 2018–2022

High-resolution soil moisture and freeze–thaw records toward the third pole using GNSS-R reconstructed observations during 2018–2022

Моделирование теплового режима дорожной одежды и земляного полотна лесовозных дорог

Soil freezing is observed throughout almost the entire forested area of the Russian Federarion in winter. The effect of negative temperatures on dusty-clay soils causes a number of adverse processes that change the properties of the soils themselves. One of the most unfavorable of these processes is the accumulation of moisture in soils under the influence of the movement of the freezing front. When freezing, water-saturated clay soils increase dramatically in volume. This leads to the appearance of frost heaving in the active zone of the forest roadbed, which has an extremely adverse effect on the structure of the entire pavement and can lead to damage to the pavement with a sharp deterioration in the transport and operational qualities of forest roads. To combat frost heaving, it is necessary to study the patterns of changes in the water-thermal regime of road structures. The depth of freezing of the pavement and the roadbed is of the greatest importance for predicting frost heaving and developing measures to combat this phenomenon. The article describes the developed system for monitoring the temperature of the road structure to a depth of 3 m and the measurement results which allow us to evaluate the temperature change at different depths from the road surface and determine the freezing depth. A total of 32 sensors have been installed with a step of 10 cm. A numerical simulation of the freezing process of the pavement and the upper part of the roadbed of a forest road has been performed, with the results compared with the indicators of field observations. Good data convergence has been revealed. According to the results of experimental studies, the freezing value has been 173 cm, and according to the results of numerical simulation – 190 cm. The average error in the results of numerical simulation of the freezing process of the pavement and the upper zone of the forest roadbed has been 8–10 % compared to the experimental data.

Развитие модели динамики снежного покрова Гидрометцентра России

Conceptual models of runoff formation used in the operational practice of hydrological forecasting by the Hydrometeorological Center of Russia include simplified parameterization of snow cover dynamics based on the use of snow cover melting coefficient, water-retaining capacity of snow and secondary freezing of meltwater in case of return of negative air temperatures. This schematization of the process is well established for the reliable calculation of the snow water equivalent for subsequent use in the calculation of meltwater inflow to the catchment surface and the calculation of streamflow characteristics. At the same time, the lack of calculation of snow density and snow height in the used schematization restricts the use of schemes for calculating of soil freezing depth in hydrological models, which seems to be extremely important for modelling runoff on mid-latitudes rivers, i.e. for the most Russian rivers. To overcome this disadvantage, the snow density and snow height parameterization was added to the calculation scheme of the model, which was verified using Roshydromet’s snow measurement routes data and shown a good and satisfactory quality of modeling of model characteristics.

Predicting the volumetric heat capacity of freezing soils using the soil freezing characteristic curve

The heat capacity during the freezing process is a vital hydrothermal parameter. It is difficult to experimentally measure the heat capacity of freezing soils. Therefore, in this study, we proposed a new method to estimate the volumetric heat capacity based on the combination of the weighted arithmetic mean model for volumetric heat capacity and soil freezing characteristic curve (SFCC) estimation model. Five specific heat capacity models for solid particle and six SFCC estimation models were introduced. It can be concluded that the six SFCC-based volumetric heat capacity models with specific heat capacity of solid particle = 0.725 MJMg-1K−1 exhibited the best performance. Among the six SFCC-based volumetric heat capacity models, the Kong et al-based volumetric heat capacity model has the best performance in predicting the volumetric heat capacity. The predicted SFCC-based volumetric heat capacity model is easy to use and can be applied to mimic the variation of volumetric heat capacity with subzero temperature.

A systematic investigation of the freezing process of silty clay through unidirectional stepwise freezing method combined with digital imaging processing technology

Soil freezing represents a complex thermo-hydro-mechanical coupling process that encompasses a range of physical and mechanical phenomena, such as heat transfer, moisture migration, cryostructure development, ice lens segregation, frost heave, and consolidation, all of which interact and influence one another throughout the freezing process. This study conducted a unidirectional stepwise freezing test, comprising three distinct freezing stages, to investigate the freezing behavior of Qinghai-Tibet silty clay using digital imaging processing technology (DIPT), which includes an image acquisition system and a digital image processing system. The results demonstrate that the stepwise freezing test provides a more comprehensive insight into the physical and mechanical processes occurring during unidirectional soil freezing. At various stages of freezing, the temperature distribution within the sample achieves a linear stabilization, with the frozen zone exhibiting a slightly larger extent compared to the unfrozen zone. The longitudinal section of the sample developed layered cryogenic cracks, whereas the horizontal section revealed interconnected cryogenic polygonal cracks of varying sizes, which facilitated moisture migration and ice segregation. Furthermore, ice lenses can segregate within a broad temperature range below the soil freezing point in the frozen zone, resulting in frost heave within the frozen zone and consolidation of the unfrozen zone. This study proposes an experimental method to clarify the complex phenomenon and mechanisms of frost heave during soil freezing.

Premelting Theory‐Based Mechanism for Water Freezing in Saline Soil

AbstractThe unfrozen water content constitutes a pivotal parameter in freezing soil, significantly impacting its thermal‐mechanical and deformation behavior. This study delves into the alterations in soil attributes as unfrozen water content varies. It examines the influences of impurities, van der Waals forces, and Coulomb forces on the water film, employing the premelting theory as a foundation. A critical state curve quantifying the ratio of the surface charge density to impurity concentration is parameterized for various soil types. Subsequently, combining the theory of effective solution concentration, we have provided calculation methods for the particle surface parameters of pore solutions as ideal and non‐ideal dilute solutions, respectively. This has determined the key variables in the model. Additionally, through the integration of equivalent particle sizes, packing structure, and water film thickness, a calculation model is devised and verified for determining the unfrozen water content and residual water content within in freezing soil. The findings indicate that fluctuation in the unfrozen water content primarily stem from impurities. In soils with equivalent saline content, impurity levels exhibit proportionality to the equivalent particle sizes. The residual unfrozen water is predominantly present within the absorbed water layer.

A critical assessment of geological weighing lysimeters: Part 2—Modelling field scale soil moisture storage and hydrological fluxes

AbstractLand surface models (LSMs) are used to simulate the terrestrial component of water, energy, and biogeochemical cycles. These simulations are useful for water resources management, drought and flood prediction, and numerical climate/weather prediction. However, the usefulness of LSMs are dependent by their ability to reproduce states and fluxes realistically. Accurate measurements of water storage are useful to calibrate and validate LSMs outputs. Geological weighing lysimeters (GWLs) are instruments that can provide field‐scale estimates of integrated total water storage within a soil profile. We use field estimates of total water storage and subsurface storage to critically evaluate two different land surface models: the Modélisation Environnementale communautaire—Surface Hydrology (MESH) which uses the Canadian Land Surface Scheme (CLASS), and the Structure for Unifying Multiple Modeling Alternatives: (SUMMA). These models have differences in how the processes and properties of the land surface are represented. We attempted to parameterize each model in an equivalent manner, to minimize model differences. Both models were able to reproduce observations of total water storage and subsurface storage reasonably well. However, there were inconsistencies in the simulated timing of snowmelt; depth of soil freezing; total evapotranspiration; partitioning of evaporation between soil evaporation and evaporation of intercepted water; and soil drainage. No one model emerged as better overall, though each model had specific strengths and weaknesses that we describe. Insights from this study can be used to improve model physics and performance.

Структурный подход к оценке работоспособности системы мониторинга инженерных конструкций вантового моста через Петровский канал в створе автомобильной дороги «Западный скоростной диаметр» в городе Санкт-Петербурге. Часть 2

Purpose: assessing the performance of the monitoring system for engineering structures and assessing the current state of the structures of the cable-stayed bridge across the Petrovsky Canal in the alignment of the Western High-Speed Diameter highway in the city of St. Petersburg due to the occurrence of emergency situations in which accelerometers on the pylons record values exceeding the limit. Methods: statistical data from the databases of the existing system of monitoring engineering structures is used to obtain the results. The tasks, set within the framework of the study, are accomplished by applying the theoretical methods of scientific knowledge: the analytical method, the mathematical statistics theory, induction. Results: the resulting structural approach to assessing the performance of the monitoring system for engineering structures on cable-stayed bridges makes it possible to reduce the number of false alarms of the system and assess the current state of the bridge structure. Within the framework of the III stage of the structural approach, it is proposed to develop a methodology for assessing the performance of the monitoring system for engineering structures with subsequent assessment of the current state of cablestayed bridge structures. Practical significance: the results of the work are important for construction as they expand the understanding of the features of the mechanism of soil freezing.

Numerical Simulation of Water Migration during Soil Freezing and Its Resulting Characterization

Numerical Simulation of Water Migration during Soil Freezing and Its Resulting Characterization

Changes in the spatiotemporal distribution of the timing and duration of the soil freeze–thaw status from 1979 to 2018 over the Tibetan Plateau

AbstractChanges in the soil freeze–thaw status will inevitably affect the thermal conditions and properties of the Tibetan Plateau (TP), thereby affecting its upper atmosphere, and further afield in East Asia and even globally. In this study, using the soil temperature simulated by the Community Land Model Version 5.0 (CLM5.0), the timing and duration of the soil freeze–thaw status were divided into freeze start‐date, freeze end‐date and freeze duration. Then, using linear trend estimation, correlation analysis and other methods, the changes in the spatiotemporal distribution of the timing and duration of the soil freeze–thaw status from 1979 to 2018 over the TP were analysed, and the relationships between them and surface temperature, altitude and latitude were analysed. The results obtained were as follows: (1) The soil temperature simulated by CLM5.0 can reasonably reproduce the seasonal changes in multilayer soil temperature, and correlated well with observations. Simulated by CLM5.0 of the time and duration of the soil freeze–thaw status also correlated well with observations. (2) The spatial distribution of the soil freeze–thaw status is characterized by a trend of delayed freezing, advanced thawing and shortened freeze duration from northwest to southeast over the TP. From 1979 to 2018, the freeze start‐date postponed by 7.3 days and became delayed at a rate of 1.9 days per decade, while the freeze end‐date advanced by 6.4 days at a rate of 1.7 days per decade, and the freeze duration shortened by 13.7 days at a rate of 3.6 days per decade. The timing and duration of the soil freeze–thaw status vary across different regions of the TP. The freeze start‐date in all areas of the TP has been delayed in the past 39 years. Except for the subcold zone and arid regions of the TP, the freeze end‐date has occurred earlier and the freeze duration has shortened, with the most significant changes in the subcold zone and humid regions, while the freeze end‐date has advanced at a rate of 3.6 days per decade and the freeze duration has shortened at a rate of 6.3 days per decade. (3) The timing and duration of the soil freeze–thaw status are significantly correlated with surface air temperature, elevation and latitude, exceeding the 99% confidence level. The correlation between the timing and duration of the soil freeze–thaw status and surface temperature is strongest, followed by altitude, and correlation with latitude is weaker. The correlation between surface air temperature and the timing and duration of the soil freeze–thaw status in the western TP is stronger than that in the eastern TP. The rate of change in the soil freeze–thaw status increases with altitude to 3000 m above sea level, while this rate decreases with elevation above 3000 m. The rate of change in the soil freeze–thaw status is greatest at 29°N, while the rate of delay in the freeze start‐date is minimal at 33°N and the rates of advancement in the freeze end‐date and shortening of the freeze duration are minimal at 35°N.

Road Site Inspection and Measures to Avoid Further Deformation

Strength and stability of the roadbed and engineering structures in permafrost conditions and deep seasonal freezing of soils always remain complex scientific, technical and technological problem in construction and reconstruction of roads in northern regions. Particularly important is the spread of subgrade subsidence during construction and further operation and maintenance of roads in these regions. The road destruction is mostly caused by both global warming and geological and hydrogeological conditions.To prevent the deformation development, it is necessary to provide a number of special engineering measures to prevent thawing of permafrost soils or strengthen supra-permafrost layers of foundations. The purpose of the work is to study methods for eliminating deformation of the road bed in permafrost and choosing the main method for eliminating subsidence of the road.The article discusses several ways to solve the problem of eliminating subsidence on of the federal highway. Options for reconstruction of the roadbed are considered. These are different methods of thermal stabilization, i.e., horizontal (sloping) thermal stabilization system with inclined thermal stabilizers, temporary vertical thermal stabilizers for pre-construction freezing of foundation soils, and hybrid thermal stabilization system (horizontal and vertical thermal stabilizer in one product). A method is proposed for stabilizing the road base by installing soil-cement piles. The main advantages of and disadvantages the methods are noted and cost assessment is made. A conclusion is drawn on the effectiveness of different methods to restore the subgrade structure in order to ensure the road base stability. The main method is elimination of subsidence by stabilizing the road base with installation of soil-cement piles.

Effect of Cyclic Soil Freezing and Thawing on the Lateral Load Response of Bridge Pile Foundations

In this article, a nonlinear static analysis model of a bridge pile foundation is established using numerical simulation, and the correctness of the model is verified via experiments. Then, the damage characteristics and mechanical behaviors of bridge pile foundations in cold regions under lateral loads are investigated based on the validated analysis model. The results showed that the impact of soil freeze–thaw cycles on the lateral performance of the pile–soil system is more pronounced in seasonally frozen regions compared with permafrost regions. Specifically, as the number of soil freeze–thaw cycles increases, there is a tendency for the lateral load capacity of the pile–soil system to decrease initially and then stabilize. It is worth noting that soil freeze–thaw cycles significantly influence both the stiffness and deformation capacity of the pile–soil system, with these parameters exhibiting a decreasing trend followed by stabilization as the number of freeze–thaw cycles increases. However, it has little effect on the shear force and bending moment of the pile foundation.

Pore-Scale Formation Characteristics of Impermeable Frozen Walls for Shallow Groundwater Contamination Remediation

Impermeability and water blocking are crucial for remediating shallow groundwater contamination. Traditional methods often employ curtain-grouting technology to create impermeable layers. However, cement slurry curing is irreversible, leading to permanent closure of underground aquifers and secondary pollution. This study employs an innovative approach by fabricating cylindrical models that simulate actual strata and utilizing a high-temperature and high-pressure displacement device. It systematically analyzes the variations in soil pore structure, distribution, porosity, and permeability under different temperatures, pressures, and freezing durations. The microscopic characteristics of the freezing process in water-bearing soils were studied. Results demonstrate that longer freezing time improves the effectiveness of soil freezing, reaching complete freezing at temperatures as low as −4 °C for samples with low water content. For water-saturated samples, freezing below −6 °C results in nearly zero porosity. Increased pressure at a certain freezing temperature significantly reduces permeability. When freezing temperature falls below −4 °C, water permeability in saturated samples after freezing reaches near-zero levels, while unsaturated samples experience complete freezing. These findings provide a theoretical foundation for constructing freezing curtains in remediating shallow groundwater pollution.

Evaluating soil freezing characteristic curve models for predicting unfrozen water content in freezing soils

Frozen soil is widely distributed around the world, and the phase change and migration of ice and water contribute to various engineering and agricultural challenges. The Soil Freezing Characteristic Curve (SFCC), which elucidates the relationship between water and temperature in permafrost, serves as a crucial tool for studying permafrost and forms the foundational equation for coupled numerical simulations involving permafrost water-heat-force. Different choices of SFCC result in variations in the predicted values of unfrozen water, thereby affecting the accuracy of other issues or numerical simulations. Moreover, there is a lack of studies on the performance of SFCC models under diverse conditions. Therefore, we review and classify some existing SFCC models, selects 14 SFCC models according to functional form, derivation process, physical significance etc., and evaluates these models through published data and statistical indicator RMSE, Radj2 and BIC. The effects of functional form, soil type, cooling stage and initial water content on each model were analyzed using cluster analysis and other means. It is concluded that the SFCC model is affected by the function form, and the power and exponential functions need to be modified by more parameters. The nested soil water characteristic curve model also needs to be modified for the low water content section. Meanwhile, each model also shows sensitivity to the characteristics of datasets, and the performance under different conditions is not the same. Some models may not fit data features under certain conditions. Therefore, it is necessary to reasonably select the SFCC model in different use backgrounds and conditions.

Dynamic responses of soil microbial communities to seasonal freeze-thaw cycles in a temperate agroecosystem

Soil freeze-thaw cycles (FTCs) are common in temperate agricultural ecosystems during the non-growing season and are progressively influenced by climate change. The impact of these cycles on soil microbial communities, crucial for ecosystem functioning, varies under different agricultural management practices. Here, we investigated the dynamic changes in soil microbial communities in a Mollisol during seasonal FTCs and examined the effects of stover mulching and nitrogen fertilization. We revealed distinct responses between bacterial and fungal communities. The dominant bacterial phyla reacted differently to FTCs: for example, Proteobacteria responded opportunistically, Actinobacteria, Acidobacteria, Choroflexi and Gemmatimonadetes responded sensitively, and Saccharibacteria exhibited a tolerance response. In contrast, the fungal community composition remained relatively stable during FTCs, except for a decline in Glomeromycota. Certain bacterial OTUs acted as sensitive indicators of FTCs, forming keystone modules in the network that are closely linked to soil carbon, nitrogen content and potential functions. Additionally, neither stover mulching nor nitrogen fertilization significantly influenced microbial richness, diversity and potential functions. However, over time, more indicator species specific to these agricultural practices began to emerge within the networks and gradually occupied the central positions. Furthermore, our findings suggest that farming practices, by introducing keystone microbes and changing interspecies interactions (even without changing microbial richness and diversity), can enhance microbial community stability against FTC disturbances. Specifically, higher nitrogen input with stover removal promotes fungal stability during soil freezing, while lower nitrogen levels increase bacterial stability during soil thawing. Considering the fungal tolerance to FTCs, we recommend reducing nitrogen input for manipulating bacterial interactions, thereby enhancing overall microbial resilience to seasonal FTCs. In summary, our research reveals that microbial responses to seasonal FTCs are reshaped through land management to support ecosystem functions under environmental stress amid climate change.

Calculating the Soil Freezing Characteristic Curve of Saline Soil With Equivalent State of Bulk Solution

AbstractThe relationship between unfrozen water content and temperature, called as soil freezing characteristic curve (SFCC), is of importance for hydrologic, engineering, environmental issues related to frozen soil. The SFCC of saline soil is essentially a result of phase equilibrium of pore solution, which is similar but not identical to that of bulk solution. However, there is still a vacancy of study on the phase equilibrium of pore solution in frozen soil. In this study, image transformation was used to establish the relationship of phase equilibrium between bulk solution and pore solution, with four introduced parameters. Then, the new model of SFCC for saline soil was proposed based on the equivalent state of bulk solution with Pitzer model and SFCC of nonsaline soil. The model was validated by the experimental data from published articles and showed good performance in calculating SFCC of saline soils regardless of soil type, phase transition path, and soil initial water‐salt condition, and some advantages when compared to other three models. All the four introduced parameters have clear physical meanings and their relationships with soil type and initial salt concentration were discussed. Finally, the evolution of phase diagram from bulk solution to pore solution at icing stage was figured out. Further studies are needed for their relationship at salt crystallization stage. Shifting the research perspective from unfrozen water content to pore solution, this study gives a new approach to research of freezing characteristic of saline soil and could promote hydrological and engineering research in cold regions.

Variation in Soil Hydrothermal after 29-Year Straw Return in Northeast China during the Freeze–Thaw Process

In seasonal agricultural frozen soil areas, the straw return may influence the freeze–thaw characteristics by changing the soil organic matter and porosity. Monitoring moisture and heat in the freeze–thaw period is significant for preventing spring waterlogging and reasonable planting arrangements. However, the effect of long-term straw return on the soil freeze–thaw process is still unclear. In this study, we investigated the dynamics of soil temperature (ST) and soil moisture (SM) between straw-return cropland (SF) for 29 consecutive years and no-fertilization cropland (NF) during freeze–thaw progress in northeast China. The soil in both sites underwent unidirectional freezing and bidirectional thawing processes. The soil freezing and thawing dates in the NF of the profile occurred earlier than that in the SF. The NF had higher frozen depth and freezing rate than the SF and exhibited a larger range of ST variation and higher heat transmission efficiency. The SM showed a declining trend before the ST started to decrease to a freezing point at different depths in both sites. The migrated SM in most soil layers decreased during monitoring. The relationship between SM and negative ST was a power function at different frozen depths. The SM decreased rapidly in the range of −2–0 °C in both sites. During phase changes, the SF and NF consumed 33.0 and 43.6 MJ m−2, respectively. The results can partially explain the response of straw return to soil hydrothermal variation during the freeze-thaw process. This study may provide an integral theory for effectively utilizing agricultural soil hydrothermal resource in northeast China.