Frost Heave Research Articles

Modeling and numerical analysis of the canopy effect with time-varying top boundary conditions of soil with an ice-water-air multiphase zone

The canopy effect refers to the effect that road surfaces or other surface coverings have when they block the water evaporation from subgrade soil, causing moisture accumulation underneath the road surface. For railway subgrades, evaporation is not completely blocked by the stone ballast layer. When shallow soil gradually freezes in winter, the top cover effect becomes stronger. This effect is called the canopy effect with time-varying top boundary conditions. Numerical simulation of this kind of canopy effect is important to the control of frost heaving of railway subgrades. In this paper, the previously presented canopy effect model is extended by considering the top boundary variation in addition to unsaturated soil moisture migration and frost heave formulation. Moreover, it is clarified that an ice-water-air multiphase zone exists during the development of this kind of canopy effect. Consideration of the interaction and development process of each phase in this multiphase zone is necessary for accurate analysis of this kind of canopy effect. Water migration, the thickness of the ice-water-air multiphase zone and the development of frost heave in the subgrade soil under different initial volumetric water contents or temperature differences are analyzed to demonstrate the applicability of the proposed mathematic model.

Coupled thermal-hydro-mechanical model of deep artificial freezing clay

The research on the thermal-hydro-mechanical coupling theory is important to explore the freezing mechanism of deep shaft. It is difficult to accurately describe the moisture migration and law of frost heaving characteristics of the clay during the freezing process. In this study, a thermal-hydro-mechanical formulation is established to simulate the freezing process of soil according to the dual-porosity medium approach. The reasonability of the coupling model is verified by the comparisons of the calculated results with the model and field tests. It is indicated that the moisture migration can be represented by the combination action of the matrix and fracture permeability during the freezing process. As the freezing time increases, the permeability of freezing clay decreases greatly, the moisture gathers around the freezing pipe, and a high frost heaving stress is formed close to the freezing pipe due to the moisture migration. Then, the temperature evolution, the moisture migration and the frost deformation of frozen soil wall are investigated to explore the freezing mechanism of deep shaft.

Frost Heaving and Induced Pressure of Unsaturated Interfacial Zone between Gravel Ballast and Subgrade

Most existing railroads are composed of gravel ballast. One of the major issues with gravel ballast is frost damage in cold regions. Gravelly soils are known to be not prone to frost action due to their low water retention capacity and high hydraulic conductivity. However, reports indicated continued frost damages resulting from the mixed zone between gravel ballast and subgrade. This study evaluated the frost heaving and induced pressure of gravel ballast–subgrade soil mixtures via 1D soil column testing in a cold chamber. Gravel ballast and subgrade soil were collected from the railroad in situ. Various mixing ratios and degrees of saturation were used as factors affecting the frost experiments. The mixtures were placed in the cold chamber, and vertical displacements and pressures were measured. Overall evaluations showed that gravelly soils are not a geomaterial prone to frost damage; however, the frost potential of gravel ballast increases as the degree of saturation and the mixing portion of the subgrade soil increase. Therefore, the interfacial zone between gravel ballast and subgrade soil, especially where possible mixing with low drainage exists, needs cautions of potential frost damage.

Study on the frost heave behavior of the freezing unsaturated silty clay

The frost heave behavior of unsaturated soils is related to the water-vapor redistribution, whereas the water-vapor migration processes cannot be directly observed due to the limitations of measurement techniques. To reveal the frost heave behavior of the unsaturated silty clay, five specimens for unsaturated silty clay were prepared. One-side freezing tests for the five specimens were carried out under uniform conditions. The test durations are 12 h, 24 h, 48 h, 96 h, and 192 h, respectively, and the water content profiles in the freezing process were studied by testing final water content profile of each specimen as the profile at that time. The heat-water-vapor migration and frost heave behavior of the freezing unsaturated silty clay were interpreted. The results showed that the temperature variations can be divided into three stages (a sharply cooling stage, a slowly cooling stage, and a steady stage) according to the change rate of temperature, and the duration times of the first and the second stage are short. A mix migration of liquid water and water vapor in unsaturated soils can be experimentally determined during the freezing, and a thin ice forms at the top of the specimens due to the vapor migration and condensation. Meanwhile, the liquid water in unfrozen zone mainly migrates to frozen fringe, and segregated ice forms in the freezing unsaturated soil once enough water accumulates at the frozen fringe. In addition, the frost heave of the specimens is discrete under the uniform test conditions. We selected the relative error and absolute error of the frost heave as evaluation indexes, and further evaluated the repeatability of the test results. Evaluation results showed that the one-side freezing test results are repeatable, and it is an useful testing method to study the heat-water-vapor migration through one-side freezing tests with different test durations under uniform testing conditions. Moreover, the confusion that the frost heave mainly occurred in the top layer of high-speed railway subgrade was explicit solved by the behavior revealed in this paper.

Experimental study and prediction model on frost heave and thawing settlement deformation of subgrade soil in alpine meadow area of Qinghai-Tibet Plateau

Experimental study and prediction model on frost heave and thawing settlement deformation of subgrade soil in alpine meadow area of Qinghai-Tibet Plateau

A non-local frost heave model based on peridynamics theory

Multitudes of physical phenomena have non-local effects. However, non-local effects are not considered by most soil frost heave models. Peridynamics takes into account non-local interactions, and has not yet been applied in the field of permafrost research. Thus, this study is a preliminary attempt to introduce peridynamics into permafrost research. In this paper, a one-dimensional frost heave model of saturated soils for local theory is established, and then converted to a non-local model of peridynamics. A program of the model is used to verify the model. The comparison between the numerical simulation results and the measured results shows that the model can basically reflect the characteristics of the physical field evolution in the frost heave process of saturated soils. To accelerate the model, the integral term in the mathematical model is deduced into the form of convolution. The modified model can use fast Fourier transform to calculate the convolution term in the model. Compared with the original program, the program accelerated by the fast Fourier transform has a lower memory cost and a higher calculation efficiency.

Frost heaving strain monitoring for lining structure in extreme cold and high-altitude area with FBG strain sensors

Due to the extreme temperature with significant variation in the alpine region, the tunnels in this area are subjected to intense freeze–thaw cycles and frost heaves, which leads to the cracking of the second lining structure. We propose an approach to monitor the frost heaving strain of the second lining and simultaneously measure the thermal strain and applied stress strain of the structure. The Fiber Bragg Grating (FBG) strain sensors are installed on the structure surface to measure the strains caused by the thermal strain and loaded stress. Meanwhile, one FBG temperature sensor is installed on the structure surface to measure the local temperature. Then, the structure thermal strain and applied stress strain are simultaneously measured based on the sensitivity difference for temperature and strain response of the above two measurement methods. The proposed approach is implemented in an alpine region tunnel. The results show that the local temperature is inversely proportional to the total strain and the thermal apparent strain of the second lining. The applied stress–strain of the lining fluctuates in a small range, and the thermal strain from the daily temperature difference incremental demodulation is very close to the daily strain difference. Therefore, the main cause of lining frost damage is the thermal strain due to the local temperature variation, and there is no frost heave occurred in the surrounding rock. Thus, the method is offered to monitor the freeze–thaw cycles and freeze-swelling effects in the extreme cold and high-altitude tunnels.

Investigating the mechanism of frost penetration under railway embankment and projecting frost depth for future expected climate: A case study

A common issue for railways constructed in cold regions is the development of localized frost heave on the surface of railway tracks during winter and track softening during the spring thaw. Both frost heave and thaw softening cause track geometry degradation and often require frequent maintenance and the reduction of train speeds to ensure safe operating conditions. This study investigated the mechanism of frost development within a railway embankment through field observations and numerical simulations. This paper uses the temperature measurements from an instrumented section of railway track in Ontario, Canada to calibrate a numerical model and then uses this model to quantify the effect of ambient temperature and the amount of snowfall on the frost penetration within railway foundations. The results show a widespread frost zone develops within the embankment that could last until spring. The sensitivity analysis conducted as part of this study shows ambient temperature has a stronger effect on frost penetration than snow on the ground. Moreover, this paper proposes a simplified methodology to combine numerical model results and data from climate models to project future frost depth at a given location. The application of this methodology at the study site of this project indicated the frost will penetrate less under future climate but still to sufficient depths to reach the frost-susceptible layers of subgrade.

Evolution Patterns of Frost-Heaving Pressure with Partial Ponding in Cold Region Tunnels

The calculation of the frost-heaving pressure is one of the key issues in the frost-resistant design of tunnels in cold regions. To reveal the frost heave mechanism of partial ponding behind the tunnel linings, a three-dimensional geo-mechanical model test was developed that only considered the frost heave load. A self-designed water bladder equipment was set up to simulate the partial ponding. The frost heave response characteristics of the surrounding rock with partial ponding were simulated to analyze the change law of temperature field and frost-heaving pressure under freezing by using air-conditioning to reduce the ambient temperature of the model test. The changes in the internal temperature of the surrounding rock and the evolution of the frost-heaving pressure over time under different thicknesses of partial ponding and different levels of surrounding rock were compared. The theoretical calculation value of frost-heaving pressure and the test values of the model test were compared and analyzed using the numerical simulation method. The results showed that the temperature of the surrounding rock presented three-stage changes, which showed a lagging characteristic relative to the environmental temperature. The empirical equation for the relationship between the frost-heaving pressure and time was obtained by nonlinear fitting of the experimental results. Taking advantage of the regular tetrahedron calculation model, the paper established a semiempirical frost-heaving pressure model considering time and space effects, which was identical with the frost-heaving phenomenon from the experiments. Theoretical analysis, experiments, and numerical simulation show that the frost-heaving pressure increased along with the depth of partial ponding and the elastic resistance coefficient of surrounding rock, which could provide references for revealing the frost-heaving pressure of partial ponding behind tunnels of cold regions and has a significant meaning in the engineering application.

Experimental study on deformation characteristics of chloride silty clay during freeze-thaw in an open system

Artificial ground freezing (AGF) is widely applied in coastal urban areas for underground transportation infrastructure construction. It is vital to understand deformation characteristics and the mechanisms of chloride soils during freeze-thaw (F-T) for the safe application of AGF. A series of unidirectional open-system F-t-tests were conducted to investigate the deformation characteristics of saturated clay with various NaCl content. Continuous measurements were performed on important parameters such as temperature, solution intake volume, frost heave, and thaw settlement during F-T. Besides, the pore size distributions were obtained via the Nuclear Magnetic Resonance relaxometry to help reveal the deformation mechanism. The results indicated that the freezing front propagated rapidly (Phase I) and then reached a plateau at the thermal equilibrium stage (Phase II). The location of the freezing front in Phase II was dependent on salt content. The amount of solution intake decreased with increased salt content. The rate of solution intake in two phases was also found to be salt content-dependent, while for a certain specimen the order of the rates in two phases varied with increasing salt content. The total frost heave for the same freeze time decreased with increasing salt content and the solution intake induced frost heave mainly contributed to the total frost heave. Total thaw settlement was relatively insensitive to the salt content of higher values. At the end of freezing and thawing processes, minimal frost heave ratio and thaw settlement coefficient were both identified in the specimen with 1% salt content. Moreover, the evolution of pore structure was found to be more prominent in specimens with lower salt content due to more water-ice phase change during freezing, which caused more significant frost heave.

Evolution Law and Mechanism of Freeze–Thaw Damage of Cement-Stabilized Weathered Sand

To explore the damage evolution law of cement-stabilized weathered sand under the action of freeze–thaw cycles, relevant experimental research was carried out on stabilized weathered sand with a cement content of 3%, including unconfined compressive strength (UCS), scanning electron microscope (SEM), and mercury intrusion porosimetry (MIP) testing. Using the surface appearance, mass, and UCS of the specimen, combined with the changes of microscopic characteristics, the freeze–thaw damage law and microscopic degradation mechanism of cement-stabilized weathered sand were analyzed. The test results showed that with the increase of the number of freeze–thaw cycles, the surface appearance of the specimen continued to deteriorate, the unconfined compressive strength gradually decreased, and the mass of the specimen first increased and then decreased. After nine freeze–thaw cycles, the specimen was seriously damaged, and the strength loss was as high as 55%. From a microscopic point of view, the freeze–thaw cycles caused the pore water inside the specimen to continuously change between ice crystals and liquid. Frost heave and shrinkage weakened the cement bond between the weathered sand particles and made the pores in the specimen develop and expand continuously. With the decrease of the number of micropores and the increase of the number of medium and large pores, the particle skeleton changed from a dense structure to a porous structure, which eventually led to the deterioration of the macroscopic properties of the cement-stabilized weathered sand.

Heat and Mass Transfer by Vapour in Freezing Soils

Vapour mass transfer is often underestimated when designing the bases for structures in frost susceptible soils. Intensive and long-term vapour transport may lead to excessive frost heaving and associated issues. A vapour transport model and the algorithm of its calculation is presented in this study based on the results of experimental freeze–thaw cycles of nine soil samples with varied density. The temperature field distribution, air voids volume and the energy comprising latent heat for the phase transition and heat extracted during the temperature drop are the main parameters for determining the vapour velocity and the amount of ice formed. According to the results, the average speed of vapour transport in frozen soils was about 0.4 m/h. The amount of ice built in 1 h during uniaxial freezing due to the saturated vapour pressure difference was 1.64 × 10−5–3.6 × 10−⁵ g/h in loose samples and 1.41 × 10−⁶ g/h to 5.61 × 10−⁷ g/h in dense samples of 10 cm diameter and 10 cm high sections. The results show that vapour mass transfer can increase the risk of ice growth and related problems.

Prediction of the unfrozen water content in soils based on premelting theory

The variation of unfrozen water content with temperature has a significant effect on the coupled heat-water transport in freezing soil, which can cause the frost heave and thaw settlement, and thus influence the stability of infrastructures. The premelting theory for water–ice in soils is developed to study the unfrozen water variation in freezing soil. The developed theory integrates the interfacial premelting of contact ice, the soil particles, the melting of the ice surface, and the premelting induced by impurity and curvature. A model to predict the unfrozen water content is then established by considering the change of unfrozen water film. The equivalent grain size is introduced to improve the solving efficiency in the calculation. Finally, the proposed analytical model is verified by the test data. The results indicate that the thickness of water film in soils increases when the surface charge density and the impurity concentration increase under the same supercooling degree. The surface melting on the interfaces of soil particle and the pore ice has key influence on the variation of the liquid water content. Meanwhile, the unfrozen water content increases with the increasing impurity concentration and surface charge on soil particles. Besides, the unfrozen water content also increases with the decreasing radius of soil particles.

Water Migration and Segregated Ice Formation in Frozen Ground: Current Advances and Future Perspectives

A characteristic of frozen ground is a tendency to form banded sequences of particle-free ice lenses separated by layers of ice-infiltrated soil, which produce frost heave. In permafrost, the deformation of the ground surface caused by segregated ice harms engineering facilities and has considerable influences on regional hydrology, ecology, and climate changes. For predicting the impacts of permafrost degradation under global warming and segregated ice transformation on engineering and environmental, establishing appropriate mathematical models to describe water migration and ice behavior in frozen soil is necessary. This requires an essential understanding of water migration and segregated ice formation in frozen ground. This article reviewed mechanisms of water migration and ice formation in frozen soils and their model construction and introduced the effects of segregated ice on the permafrost environment included landforms, regional hydrological patterns, and ecosystems. Currently, the soil water potential has been widely accepted to characterize the energy state of liquid water, to further study the direction and water flux of water moisture migration. Models aimed to describe the dynamics of ice formation have successfully predicted the macroscopic processes of segregated ice, such as the rigid ice model and segregation potential model, which has been widely used and further developed. However, some difficulties to describe their theoretical basis of microscope physics still need further study. Besides, how to describe the ice lens in the landscape models is another interesting challenge that helps to understand the interaction between soil ice segregation and the permafrost environment. In the final of this review, some concerns overlooked by current research have been summarized which should be the central focus in future study.

Intra‐Annual Ground Surface Deformation Detected by Site Observation, Simulation and InSAR Monitoring in Permafrost Site of Xidatan, Qinghai‐Tibet Plateau

AbstractThe permafrost degradation can cause long‐term ground surface subsidence, and the surface undergoes frost heave and thaw settlement due to the ice‐water phase change in the active layer. The multi‐year surveys by leveling observations and Interferometric Synthetic Aperture Radar monitoring (InSAR) are helpful to understand the characteristics of seasonal deformation and to model the permafrost terrain surface deformation. In this paper, we studied the characteristics of seasonal deformation over permafrost terrain in Xidatan, obtained by leveling measurements from 2010 to 2018, Sentinel‐1 data from 2014 to 2020, and hydrothermal‐data‐based simulation. The results consistently showed a four‐stage pattern of seasonal deformation characteristics: Summer thaw subsiding, warm‐season stable‐standing, winter freeze heaving and stable‐standing. The leveling measurements proved that spatial heterogeneity also exists on a small spatial scale (400 m2). The deformation amplitude obtained by leveling data is the largest, and the InSAR data is the smallest.

Investigation About Variation Law of Frost Heave Force of Seasonal Cold Region Tunnels: A Case Study

The frost heave force (FHF) is one of the most important reason of inducing freezing damages of tunnel in seasonal frozen regions. Analyzing the change law of FHF is helpful to design for avoiding freezing damages in the tunnel lining. Field measurement is an approved method used in mechanical analysis of tunnel lining, however, it is difficult to measure the FHF directly, which is changed coupled with the original surrounding rock pressure (OSRP). In this paper, in order to clarifying the change law of the FHF, a new measuring method was presented. The best advantage of this method is that the FHF could be separated from the OSRP by measuring the surrounding rock temperature and the lining pressure at the same time. A lot of field measurement work about the FHF was conducted based on Jichoushan tunnel and the change law of the FHF was analyzed using the presented method. The results can provide preference for the antifreeze design of tunnel in seasonal cold regions.

The lining responses for shallow mountain tunnels subjected to frost heaving

The lining responses for shallow mountain tunnels subjected to frost heaving

Experimental and multiscale modeling investigations of cryo-thermal cycling effects on the mechanical behaviors of carbon fiber reinforced epoxy composites

In cryotank applications, carbon fiber reinforced epoxy composites are required to face the challenge of extreme cryo-thermal cycles while rare relevant research work has been conducted. This paper reports cryo-thermal cycling effects on the mechanical behaviors of carbon fiber reinforced epoxy composites via experimental and multiscale finite element method (FEM) investigations. Four types of cryo-thermal cycling are designed to explore the roles of the cycling number and the cycling period under normal and severe conditions. Unidirectional and orthotropic laminates are prepared to demonstrate intralaminar and interlaminar expansion mismatch phenomena. For unidirectional laminates, the transverse tensile strength shows a dramatic initial decrease of 18.7%, 21.2%, 4.1% and 17.4% while the interlaminar shear strength is lowered by 4.9%, 14.2%, 5.1% and 14.0% after cryo-thermal cycling for four cycle types, respectively. Meanwhile, it is exhibited that the interlaminar shear strength of orthotropic laminates is reduced by 17.1%, 18.1%, 13.1% and 17.9%, respectively. Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) measurements are executed to detect the secondary curing. Based on the constitutive relationship affected by temperature and moisture absorption, a microscale unit cell with random fibers and a specimen-sized model with cohesive elements are established to reveal the intralaminar and interlaminar damage evolutions during cryo-thermal cycling. After elucidating typical damage modes, such as interface debonding, matrix microcracks, surface frost heave and interlaminar gap generating, the multiscale FEM model is modified to evaluate mechanical degradations quantitatively, which gives reasonable explanations for experimental results and provides an efficient and convenient method for composite design.

Model test on the development of thermal regime and frost heave of a gravelly soil under seepage during artificial freezing

In order to investigate the development of thermal regime and frost heave of a gravelly soil under seepage during artificial freezing, a large-scale model test system was designed. The typical gravelly soil in Beijing obtained from a construction site was taken as the study object. Artificial freezing tests were carried out on the soil layer under different seepage velocities. The test results indicated that the greater was the seepage velocity, the longer the closure time of frozen wall was needed, while the frozen wall would not intersect when the seepage velocity was too large. Lagged frost heave was observed after the thermal balance was reached. The frost heave of soil layer increased with the increase in the distance from the freezing pipes. Within the frozen range, frost heave increased with the increase in seepage velocity. Under seepage, the soil layer would turn into a soil of weak frost heave according to the Chinese code, while it was classified as non-frost heave under the hydrostatic condition. The model test showed that when the artificial ground freezing is used in the gravelly soil layer under seepage, the influence of seepage on thermal regime should be sufficiently considered, and considerable frost heave of soil layer might be expected.

Effect of environmental factors on mechanical properties and damage characteristics of mine overburden used in subgrade

ABSTRACT The resource utilisation of mine overburden in subgrade is an essential approach to accelerate environmental governance in mining areas. The present study focuses on investigating the mechanical properties and damage evolution of mine overburden under different environmental factors. The influences of water immersion, freeze–thaw cycles, water and salt migration on the road characteristics of mine overburden with different coarse grain contents (CGCs) were systematically studied and a cumulative damage model of mine overburden was proposed. The durability of mine overburden under the effect of the environmental factors was further compared. The results showed that mine overburden has less frost heave and can be utilised as subgrade filler in seasonally frozen region. With the increase of CGC of mine overburden, the resilient modulus and CBR gradually increase, and the UCS increases first and then decreases. The cumulative damage model of mechanical properties can effectively characterise the failure evolution of mine overburden. The infiltration of sulphate solution turns the mine overburden filler into weak frost heaving soil. The mine overburden with a CGC of 40% – 60% can be selected to improve the environmental adaptation. The wrapping method is recommended to reduce the impact of negative temperature and moisture on mine overburden subgrade.