Ice Lens Formation Research Articles

The Modelling of Freezing Process in Saturated Soil Based on the Thermal-Hydro-Mechanical Multi-Physics Field Coupling Theory

The freezing process of saturated soil is studied under the condition of water replenishment. The process of soil freezing was simulated based on the theory of the energy and mass conservation equations and the equation of mechanical equilibrium. The accuracy of the model was verified by comparison with the experimental results of soil freezing. One-side freezing of a saturated 10-cm-high soil column in an open system with different parameters was simulated, and the effects of the initial void ratio, hydraulic conductivity, and thermal conductivity of soil particles on soil frost heave, freezing depth, and ice lenses distribution during soil freezing were explored. During the freezing process, water migrates from the warm end to the frozen fringe under the actions of the temperature gradient and pore pressure. During the initial period of freezing, the frozen front quickly moves downward, the freezing depth is about 5 cm after freezing for 30 h, and the final freezing depth remains about 6 cm. The freezing depth of the soil column is affected by soil porosity and thermal conductivity, but the final freezing depth mainly depends on the temperatures of the top and lower surfaces. The frost heave is mainly related to the amount of water migration. The relationship between the amount of frost heave and the hydraulic conductivity is positively correlated, and the thickness of the stable ice lens is greatly affected by the hydraulic conductivity. With the increase of the hydraulic conductivity and initial void ratio, the formation of ice lenses in the soil become easier. With the increase of the initial void ratio and thermal conductivity of soil particles, the frost heave of the soil column also increases. With high-thermal-conductivity soil, the formation of ice lenses become difficult.

Visualizing cation treatment effects on frozen clay soils through μCT scanning

X-ray micro-computed tomography (μCT) scanning is a proven technique with applications in geoscience, soil science, and geotechnical engineering. Here we apply the technique to investigate the effects of cation treatments on clayey soil micro-fabric in a frozen state. We imaged six suites of frozen cation-treated soils (montmorillonite, kaolinite, illite, illite-smectite, chlorite, and Copper River heterogeneous soil) at a resolution of 8.17 μm. Although this resolution was insufficient to observe differences in microaggregate formation as a result of cation treatment, we did observe micro-lenticular ice structures in the smectite-bearing soils that were invisible to the unaided eye. Quantitative analysis of the morphometric parameters from the illite-smectite and Copper River sample suites provided results that supported the visual observations, with the Copper River heterogeneous soil being more frost susceptible than illite-smectite, regardless of cation treatment. The μCT results of these small soil cores also indicate that within the Copper River suite, the Ca2+-treated and Na+-treated samples are the most and least frost susceptible, respectively, which is in agreement with previous frost heave testing. Results from this study indicate that μCT morphometric parameters can be used to quantify micro-lenticular ice lens formation in small samples and to serve as a quality control on sample preparation.

Moisture Transfer and Formation of Separate Ice in the Freezing Process of Saturated Soils

The formation and layer of ice lenses during the freezing of soil in cold regions is closely related to frozen heave and moisture immigration. The purpose of the paper is to explain the physical mechanisms pertaining to ice lens formation, which were analyzed and verified using numerical simulation results. Based on a few assumptions, the formation and layers of ice lenses are illuminated in the following steps: the initial stage of freezing, formation of the first layer of ice lens, formation of the second layer of ice lens, and formation of the final layer of ice lens. Compared with the numerical results of coupled thermo–hydro–mechanical simulations of one-side freezing of soil columns in an open system, the proposed analysis method of the formation and layers of ice lenses is verified to be reasonable, and it is demonstrated that the classical criterion for the formation of ice lens in freezing saturated soil is only suitable for the final layer of ice lens. Finally, a new criterion, in terms of flux rate, for the formation of ice lens is proposed.

Modelling frost heave in unsaturated coarse-grained soils

Coarse-grained soils were considered not susceptible to frost heave. However, substantial frost heave has been observed in unsaturated coarse fills in high-speed railway embankments. Recent experimental results in the literature show that vapour transfer has a considerable influence on the frost heaving of coarse-grained soil. However, vapour transfer has rarely been considered in modelling frost heave. This study presents a new frost heave model that considers vapour transfer and its contribution to ice formation. An updated computer program (PCHeave) is developed to account for the vapour transfer in unsaturated coarse-grained soils, where the rigid ice theory is applied to initiate ice lens formation in the frozen fringe. The results of the proposed model are compared with laboratory test results, which show reasonable agreement. The frost heave data monitored in 2013–2014 along the embankment of the Harbin–Dalian Passenger Dedicated Railway are also used to validate the proposed model. The prediction of the model agrees well with the measured results of frost heave and frost depth. This indicates that the proposed model can reasonably reflect the process of frost heave caused by vapour transfer in unsaturated coarse-grained soils.

Strength and microstructure characteristics of cement-soda residue solidified/stabilized zinc contaminated soil subjected to freezing–thawing cycles

The remediation efficiency of the solidification/stabilization (s/s) method on soil contaminated with heavy metals may deteriorate when the treated soil is exposed to freezing–thawing (F–T) cycles. In this study, a series of laboratory tests were conducted to investigate the strength and microstructural characteristics of Zn-contaminated soil treated by cement-soda residue under cyclical F–T conditions. Test results showed that the stress–strain curves were able to be characterized by a strain softening model and the failure mode could be classified as brittle failure before subjecting to F–T cycles. After exposure to the F–T cycles, the stress–strain curves gradually began to resemble the hardening model, and the compressive strength decreased significantly. Unconfined compressive strength (UCS) of the specimens obtained the maximum value at Zn2+ concentration of 2000 mg/kg, regardless of their exposure to the F–T cycles; sample Zn0.2 was the most vulnerable. After being subjected to F–T cycles, micro-cracks formed in the specimens. These cracks would be enlarged by the continuous exposure to F–T cycles, which resulted in the reduction of strength. F–T cycles could significantly damage the crystalline structures of cement hydrates; the damage could also contribute to the deterioration of soil structure. Microstructural analysis results showed that the size of the samples' micro-pores decreased due to the migration of pore water during freezing, while the size of larger pores increased due to ice lens formation and expansion.

A frost heave model of unsaturated coarse-grained soil considering vapour transfer

Substantial frost heave has been observed in coarse fills in high-speed railway embankments. These coarse fills have low fine contents and very low water content. The groundwater table is located below the coarse fills. The coarse fills were considered not susceptible to frost heave. Recent experimental results in the literature showed that vapour transfer has a considerable influence on the frost heaving of unsaturated coarse-grained soil. But vapour transfer has been rarely considered in the modelling of frost heave. This study presents a new frost heave model with considering vapour transfer and its contribution to ice formation. The rigid ice theory is applied to initiate an ice lens formation in the frozen fringe. An updated computer programme PCHeave is developed by considering the vapour transfer. The results of the proposed model are compared with laboratory test results, which show reasonable agreement. The prediction of the model agrees well with the measured frost heave and frost depth, which indicates that the proposed model can reasonably reflects the process of frost heave in unsaturated coarse soil.

Image processing method for observing ice lenses produced by the frost heave process

During the freezing process of soil, the pore water is segregated into ice lenses with the help of continuous water migration to the freezing front. The in situ and migrated water cause significant frost heave and stress in all directions, which can threaten surrounding structures. Pore ice and segregated ice lenses directly cause changes in the frozen soil properties, such as enhanced strength and water tightness. Although some researchers have developed proper procedures to observe and quantify the formation of ice lenses in soils, the authors are going to indicate a quantitative relationship between the forming of ice lenses with the absorbed water. Therefore, a direct observation method is proposed in this study which can measure ice lenses quantitatively and in real-time, to establish a relationship between ice lenses and absorbed water. Image processing software was applied to analyze pictures of ice lenses that were taken during a frost heave test. Based on the ice lens distribution, the forming pattern of ice lens was confirmed at the macro level. A relationship between the area of ice lenses and the absorbed water was identified, which is expected to be applied for the nondestructive detection of the water content and distribution in freezing soil for real engineering.

Frost heave and thaw consolidation modelling. Part 1: A water flux function for frost heaving

Although much effort has been made to develop various frost heave models in the past decades, a simple yet versatile model is still needed for engineering applications. This paper presents a method to estimate frost heave in frozen soil using a macroscopic water flux function that extends the segregation potential to make it applicable for both steady state and transient freezing and thawing states. The formation of an individual ice lens is modelled by combining previously developed stress and strain criteria. The water flux function, which includes various factors in accordance with the porosity rate function, can describe the growth of both new and old ice lenses. More importantly, every component of the water flux function is physically explained by the theory of pre-melting dynamics, where all the influencing factors are traced back to their impacts on the ice volume distribution. The performance of the model is demonstrated via simulations of one-dimensional freezing and thawing processes after the model is validated by a specific case from previous literature. Although adequate data are not available for a stricter experimental verification of the model, it is observed that the simulations predict the general course of events together with significant specific features that were identified in previous experimental studies.

Thermo-hydro-mechanical modeling of frost heave using the theory of poroelasticity for frost-susceptible soils in double-barrel culvert sites

Abstract The upward movement of soil due to the formation of ice lenses, known as frost heave, is detrimental to buried utilities, pavement structures and building foundations. In this paper, a fully coupled thermo-hydro-mechanical model was presented in the framework of the theory of poroelasticity and a porosity rate function aiming to predict frost heave, temperature distribution and pore water pressure in frost-susceptible soils. The model was verified by experimental and field data and applied to predict frost heave in two double-barrel concrete culvert sites in Manitoba, Canada. It was concluded that the insulation and non-frost-susceptible backfill can be used to effectively decrease frost heave and corresponding differential deformations at the road surface.

Seasonal Response and Damage Evaluation of Pavements Comprised of Insulation Layers

A well-known strategy for minimizing the negative effects of prolonged low temperatures on frost-susceptible subgrade is using insulation layers. Insulation layers help to mitigate the formation of ice lenses and frost heave in the subgrade. This paper evaluates the effect of using bottom ash (B.Ash), as well as polystyrene boards, on the seasonal response of the pavement at the University of Alberta’s Integrated Road Research Facility (IRRF) in Edmonton, Canada. Over the course of one year of data monitoring, from July 2014 until July 2015, different seasons (non-freeze-thaw, frozen, and recovering) were distinguished using the temperature and moisture data received from time domain reflectometers (TDRs) and thermistors installed across the pavement depth. Then, the time history data collected from falling-weight deflectometer (FWD) tests was used to identify the characteristic response of different sections. Results revealed that the B.Ash section performed similarly to the control section (CS) in terms of viscoelastic behavior, and the B.Ash performed considerably better than the CS in terms of the risk of fatigue cracking. However, the polystyrene sections were more prone to damages during the summer when the hot mix asphalt (HMA) temperature was more than 25°C.

Experience in designing and operating the buildings located on subsiding and heaving soils of the Minusinsk Hollows

The article presents the experience of design, expert research within the period of construction and operation of the buildings located on subsiding soils. It describes the experiment in conducting the organized soaking of a mounted house made of reinforced-concrete slabs and claydite-concrete panels. It shows the absence of danger of frost heaving while soaking the subsiding soils. There are tables demonstrating the expert studies during the inspections of deformable buildings and long-term observations over their behavior in freezing and thawing depending on the groundwater level and pressures under the bottom of the foundations. As a result of the analysis of long-term studies it has been established that the building load contributes to the reduction of frost heaving for sandy soils (fine and dust sands). In case of clayey soils, in contrast to the views on this problem emerged at the end of the 20th century, it is impossible to extinguish the migration process using pressure. If the migration flow slows down under the foundation bottom, it occurs due to the higher rate of soil freezing arising from the high thermal conductivity of the foundation body and the formation of vertical ice lenses on the borders of tension zones. The most important thing showed herein is that the thawing process in these lenses provokes the process of stability loss, where the soil protrudes from the foundation bottom. The long-term studies of frost heaving in a severe continental climate of the Minusinsk hollows enabled the development of the most effective direction of the anti-heave stabilization.

Freezing–Thawing Behavior of Lime Treated Fine–grained Soil

This research study was carried out to investigate the impact of freeze-thaw cycles on the mechanical and the mineralogical properties of lime treated fine-grained soil. The unconfined compressive strength, wave velocity, volume change, water content, pH and electrical conductivity values were determined during freeze-thaw cycles. Furthermore, Mercury porosimetry and X-ray diffraction tests were carry out to determine changes at microscopic level. The soil used in this study was taken at a site near Jossigny region in eastern part of Paris–France. The soil samples were treated with optimum lime percent 3% depending on the pH method, then cured for 28 days at 20 °C. The soil samples were subjected to 12 cycles of freeze-thaw following ASTM procedure. The result referred that, natural soil exhibit no strength resistance against freeze-thaw cycles and failed during the first hours of freeze-thaw cycles. Analyses indicated that freeze-thaw cycles reduce the unconfined compressive strength of all the tested samples. Moreover, water content during the applied cycles increases and induces significant volume changes. During freeze-thaw cycles, the cracks propagation which caused by the formation of ice lenses in the pores of lime treated soil samples were consider to have significant. The changes in the micro-structural and mineralogical properties reduce the durability of the lime treated soil samples when subjected to freeze-thaw cycles.

Freezing–Thawing Behavior of Lime Treated Fine–grained Soil

This research study was carried out to investigate the impact of freeze-thaw cycles on the mechanical and the mineralogical properties of lime treated fine-grained soil. The unconfined compressive strength, wave velocity, volume change, water content, pH and electrical conductivity values were determined during freeze-thaw cycles. Furthermore, Mercury porosimetry and X-ray diffraction tests were carry out to determine changes at microscopic level. The soil used in this study was taken at a site near Jossigny region in eastern part of Paris–France. The soil samples were treated with optimum lime percent 3% depending on the pH method, then cured for 28 days at 20 °C. The soil samples were subjected to 12 cycles of freeze-thaw following ASTM procedure.    The result referred that, natural soil exhibit no strength resistance against freeze-thaw cycles and failed during the first hours of freeze-thaw cycles. Analyses indicated that freeze-thaw cycles reduce the unconfined compressive strength of all the tested samples. Moreover, water content during the applied cycles increases and induces significant volume changes. During freeze-thaw cycles, the cracks propagation which caused by the formation of ice lenses in the pores of lime treated soil samples were consider to have significant. The changes in the micro-structural and mineralogical properties reduce the durability  of the lime treated soil samples when subjected to freeze-thaw cycles.

In situ observation of the unstable lens growth in freezing colloidal suspensions

There is a lack of knowledge on the growth dynamics of the formation of a new ice lens without frozen fringe in freezing colloidal suspensions. With experimental observations, we revealed that a new ice lens can be induced by a single ice spear rather than frozen fringe. This ice spear is possibly from the particle-induced undercooled region in front of the freezing interface and the consequent morphological instability. After the appearance of the new ice lens, its growth dynamics are quantitatively analyzed. The growth speed of ice decreases with time, which can be attributed to the premelted film flow-controlled interface movement.

A Mathematical Model of Melt Lake Development on an Ice Shelf

AbstractThe accumulation of surface meltwater on ice shelves can lead to the formation of melt lakes. Melt lakes have been implicated in ice shelf collapse; Antarctica's Larsen B Ice Shelf was observed to have a large amount of surface melt lakes present preceding its collapse in 2002. Such collapse can affect ocean circulation and temperature, cause habitat loss and contribute to sea level rise through the acceleration of tributary glaciers. We present a mathematical model of a surface melt lake on an idealized ice shelf. The model incorporates a calculation of the ice shelf surface energy balance, heat transfer through the firn, the production and percolation of meltwater into the firn, the formation of ice lenses, and the development and refreezing of surface melt lakes. The model is applied to the Larsen C Ice Shelf, where melt lakes have been observed. This region has warmed several times the global average over the last century and the Larsen C firn layer could become saturated with meltwater by the end of the century. When forced with weather station data, our model produces surface melting, meltwater accumulation, and melt lake development consistent with observations. We examine the sensitivity of lake formation to uncertain parameters and provide evidence of the importance of processes such as lateral meltwater transport. We conclude that melt lakes impact surface melt and firn density and warrant inclusion in dynamic‐thermodynamic models of ice shelf evolution within climate models, of which our model could form the basis for the thermodynamic component.

Composition and origin of a lithalsa related to lake‐level recession and Holocene terrestrial emergence, Northwest Territories, Canada

AbstractLithalsas of the Great Slave Lowland, Northwest Territories, occur within fine‐grained glaciolacustrine, lacustrine, and alluvial deposits. Detailed investigations of a lithalsa revealed that it is composed of ice‐rich sediments with ice lenses up to 0.2 m thick below 4 m depth. The observed ice accounted for about 2 m of the 4 m between the top of the lithalsa and adjacent terrain. The ice is isotopically similar to modern surface water, but enriched in δ18O relative to local precipitation. Total soluble cation concentrations are low in the basal, Shield‐derived and unweathered glaciolacustrine sediments of the lithalsa. Higher concentrations in the overlying Holocene‐aged lacustrine and alluvial deposits may be due to greater ion availability in Holocene surface waters. Increasing Cl‐ and Na+ concentrations in clays at depth likely relate to exclusion and migration of these dissolved ions in pore water during ice lens formation though total soluble cations remain comparatively low. The lithalsa developed 700 to 300 cal yr BP. A conceptual model of lithalsa formation and landscape evolution illustrates that this feature and more than 1800 other lithalsas in the region have developed in association with Holocene terrestrial emergence following lake‐level recession. Copyright © 2017 John Wiley & Sons, Ltd.

A separate-ice based solution for frost heaving-induced pressure during coupled thermal-hydro-mechanical processes in freezing soils

A frost heaving-induced pressure (FHIP) solution is developed in this paper based on the proposed separate-ice frost heave model. A coupled thermal-hydro-mechanical (THM) model, describing the growth of a single ice lens under the restraint, is firstly constructed by considering the relationship between soil porosity and effective stress. The new ice lens formation criterion indicates that the formation of a new ice lens occurs when the disjoining pressure at the ice-water interface exceeds the summation of the external pressure and the critical pressure of soil strength. With consideration of the influence of the external pressure on the deformation of unfrozen soil, equivalent water pressure and critical separation pressure for ice segregation, the FHIP model is established by combining the growth model of a single ice lens and the formation criterion of new ice lenses. The freezing tests of Xuzhou (China) silty clay under different restraints were conducted to verify our numerical results, and the observed consistency thus validates the FHIP model. Our numerical results demonstrate the stress induced deformation of the soil column and indicate that the FHIP increases with the restrained stiffness. Particularly, with the decrease of the restrained stiffness, the FHIP decreases following an exponential function. The prediction of the FHIP using the proposed method improves our understanding of the characterized behavior of the FHIP under various restraints, and thus contributes to the analysis of the coupled thermal-hydro-mechanical processes in freezing soils.

Laboratory observation and analysis of frost heave progression in clay from the Qinghai-Tibet Plateau

Frost heave has great impacts on the thermal and mechanical stability of structural foundations in cold regions. To account for these impacts, it is necessary to evaluate the soil frost heave process induced by water migration and ice segregation under different temperature gradients. By using the digital image processing Technology (DIPT), a series of laboratory one-dimensional freezing experiments were taken to investigate the ice lens formation, water migration and their distribution characteristics in the Qinghai-Tibet clay. The obtained results showed that the freezing front reached a stable state when a certain temperature gradient has been applied to the soil column for about 24 h. After that, the frozen parts in soil columns could be divided into three main zones along their longitudinal direction according to their morphological characteristics, change patterns and the contributions to sample deformations. There were the zone A in which very thin ice lenses were developed, the zone B in which thin ice lenses were developed, and the zone C in which a thick ice lens was developed. It was found that the ice segregating in the zone B had a significant influence on the soil frost heave, while ice segregating in the zone C caused consolidation in unfrozen zone. Generally, the segregating temperature happened in the zone B and zone C was between −0.31 °C and −3.53 °C. By analyzed the Computed Tomography (CT) pictures obtained from tested samples, we had reasons to believe that the inner cracks and gaps between irregular polygons had provided pathways for water migrating from unfrozen zone to frozen zone, especially to the zone B and zone C and resulted in sample’s frost heave and consolidation finally.

Image analyses of frost heave mechanisms based on freezing tests with free access to water

A freezing test apparatus was supplemented with a digital camera to allow for recording and monitoring one-dimensional freezing tests to analyze the development of ice lenses via particle image velocimetry (PIV) in the laboratory. Two tests on disturbed, partially saturated samples of silt loam were conducted. Image recording and correlation analyses provided detailed information about frost front penetration and ice lens formation(s) under varying temperature boundary conditions. Thawing has also been regarded in further studies.Results of the image analyses were compared to readings from conventional displacement measurements during the same test. Significant agreement between the results of image analyses and displacement measurements has been found. Advantages and disadvantages of utilizing image analysis methods were discussed. Potential remedies for overcoming the drawbacks of using image analysis are suggested.Image analysis is shown to be a viable method in further understanding of frost heave mechanisms.

Heating–freezing effects on the pore size distribution of a kaolinite clay

This study aims to quantify the effect of heating and freezing temperatures on the pore size distribution of saturated clays. Three kaolinite clay specimens were subjected to different temperatures: 20, 70, and − 10 °C. Upon achieving the desired temperature for each specimen, the specimens were flash frozen in liquid nitrogen to preserve their microstructure. Each specimen was, then, freeze-dried for 24 h after which consecutive two-dimensional (2-D) SEM images were taken using a dual focused ion beam/scanning electron microscope. The produced 2-D images of each specimen were used to reconstruct three-dimensional tomographies of the specimens, which were analyzed to determine the pore size distribution at each temperature. Compared to the specimen at room temperature, the pores in the specimen subjected to − 10 °C were larger; this is believed to be due to the formation of ice lenses inside the pores upon freezing and potential merging between initial pores to form larger pores. On the other hand, the heated specimen showed an increase in the volume of the smaller pores and a decrease in the volume of the larger pores compared to the specimen at room temperature. This opposite behavior between the small and large pores in the heated specimen is justified considering (1) the easier flow of water out of the larger pores compared to that in the smaller pores and (2) the anisotropic nature of the thermal expansion of the clay particles.