Frost Heave In Soils Research Articles

Characterization of freeze–thaw effects within clay by 3D X-ray Computed Tomography

Accurate quantification of moisture content redistribution and physical property change due to freeze–thaw is important for understanding frost heave and thaw settlement of fine-grained soils including clay. This paper presents 3D X-ray Computed Tomography (CT) data for a clay specimen before and after freeze–thaw and physical property data obtained by conventional laboratory testing, and the relationship among the date sets. Undisturbed clay specimens were subject to one-directional freeze–thaw in a closed system under different freezing temperatures to collect 3D X-ray CT images, and the variation in CT image intensity (CTI) before and after freeze–thaw were analyzed to reveal the spatial effects of freeze–thaw. Meanwhile, soil properties including moisture content, void ratio, and dry density were obtained for samples taken from different heights of the specimens with and without freeze–thaw to obtain their changes. Close correlations were observed between the physical property changes and the CTI variation. Linear equations were established between the changes of physical properties and the CTI variation. These equations could potentially be applied for high-resolution quantitative assessment of soil physical property changes due to freeze–thaw by using 3D X-ray CT. This study demonstrates that, compared with traditional test methods, CT scanning can be advantageous in revealing the internal change in soil physical properties due to freeze–thaw quantitatively and nondestructively.

РАЗРАБОТКА МАТЕМАТИЧЕСКОЙ МОДЕЛИ МАССОПЕРЕНОСА КОМПОНЕНТ ВОДНО-СОЛЕВОГО РАСТВОРА В ПУЧИНИСТЫХ ГРУНТАХ НА ОСНОВАНИИ КИНЕТИЧЕСКОЙ ТЕОРИИ ЖИДКОСТЕЙ

The reliability of engineering structures mostly depends on the possibility to resist adverse environmental factors. One of the most dangerous geological processes is frost heaving of soils, which is capable to develop a huge pressure and significant irregular vertical deformations. This processes is especially dangerous for non-rigid structures with a negative average annual temperature (–6...–0,5 ° С ), for example, for underground gas and condensate pipelines. Pipelines has a strong bends in short sections under the influence of frost heaving pressure, that often leads to emergency incidents. To predict the frost heaving it is necessary to solve the problem of mass transfer of water-salt solution from thawed to frozen soil. Using the kinetic theory of fluid, the authors of the article developed a mathematical model of the mass transfer of water and salt in thawed, freezing and frozen soils. The model allow to determine in an explicit form the contribution of different mechanisms of mass transfer: thermal diffusion, concentration diffusion, and filtration. The equations of diffusion transport allow to take into account the unequal mobility of molecules in an adsorbed film. In addition, it was shown that the classical expression for the diffusion flux density is valid only in the particular case of equality of the diffusion coefficients of each com-ponent in accordance with the kinetic theory of the liquid.

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.

CALCULATION OF TANGENTIAL FROST HEAVE STRESSES BASED ON PHYSICAL, MECHANICAL AND STRESS-STRAIN BEHAVIOR OF FROZEN SOIL

Development of northern territories opens up new opportunities for social and economic development of the society. However, designing construction facilities in such areas is complicated by special features of the severe climate; frost heave of soils is one of its manifestations. Normal frost heave forces under the foundation base can be neutralized by foundation embedment below the seasonal frost line. In these conditions, tangential heave stresses will act on the lateral surfaces of foundations, causing uneven lifting of structures, which will lead to the violation of the structure integrity. Regulatory and technical literature recommends determination of tangential frost heave stresses on the basis of generalized tabular data or experimentally, which is not always possible. A relevant technique for calculating tangential stresses is required, which takes into account climatic and hydrogeological conditions of the construction site. In this article, an attempt is made to reveal those aspects of originating and development of tangential frost heave stresses, which would allow carrying out their calculation. To solve this problem, the existing research experience, features of the cryogenic structure, mechanical and stress-strain behavior of frozen soils were analyzed. A relationship of tangential frost heave stresses with specific cohesion and moisture of frozen soil was revealed on the basis of the analysis. A point of view, according to which tangential frost heave stresses are a result of maximum compressive heave stresses, directed along the normal to the lateral surface of the foundation, was emphasized too; this allowed relating tangential heave stresses with the frozen soil deformation modulus. Based on the above statements, formulas for calculating tangential frost heave stresses were obtained. The calculation method for determining these stresses would provide the possibility of designing cost-effective and safe structures in areas with the severe climate.

Experimental study on the water-heat-vapor behavior in a freezing coarse-grained soil

A series of one-side freezing experiments of a coarse-grained soil with different contents of clayey loess were conducted in an open system with no-pressure water supply, to evaluate the influence of fines content and initial water content on the moisture migration and frost susceptibility of the coarse-grained soil, and to investigate the frost heave mechanism of coarse-grained soil under consideration of “pot” effect. The experimental results show that a thin ice layer appears in the cold end boundary by simulating the impervious cover, which is an important reason for the frost heave of coarse-grained soil. The frost susceptibility of the coarse-grained soil is influenced by fines content significantly, and the amount of frost heaving and frost heave ratio of soil samples increase linearly with the increase of fines content. The influence of external water on the frost susceptibility of the coarse-grained soil could not be neglected, and with the increase of fines content, the external water supply will increase. Meanwhile, with the increase of initial water content, the frost heave of coarse-grained soil increases. The start time of water intake is delayed, and it would be enlarged with the decreases of fines content and initial water content. Besides, it is also found that in the case of lower moisture content, the effect of vapor transfer on the frost heave of coarse-grained soil will become more obvious.

Алгоритм образования трещин на покрытии лесовозных дорог устраиваемых на склоне, в основании которых залегает глинистый грунт

In the article the algorithm of formation of cracks on the surface of forest roads arranged on the slope, overlain by clayey soil at the base is defined. The possible causes of the moisture transfer from the physical point of view, the movement of soil moisture in the cooling zone, the conditions of formation of cracks are considered. The principle of migration of moisture in freezing soils is formulated as follows: the migration of water into the freezing wet soils is the process of transfer of moisture, constantly arising from any violation of the equilibrium state of the phases of soil and the measurements of the external influences in the presence of temperature gradients, humidity, pressure, surface energy of mineral particles, mobility of the molecules in the water film. The ratio between the rate of migration and rate of cooling determines the number and power of ice layers in soils, freezing with the inflow of water from outside. The more delayed the temperature of ice formation at this level, the more powerful the ice layer arise here, as enough water have time to catch up with for the growth of ice crystals. Water migration in frozen soils is possible only due to the unfrozen water held by adsorption forces by the surface of the mineral particles of soil and ice, it is subjected to the same laws of motion of film water, which are established for soils having a positive temperature, but has its own characteristics due to the additional action of crystallization forces of ice; however, in this case the migration process of water film will be very slow. Transfer of energy and substances in multicomponent environments in the general case is described using the apparatus of the thermodynamics of irreversible processes. When creating temperature gradient in the dispersion medium the main effect occurs – the heat flow and cross effects, including mass flow. The results of the experiments and the numerical calculations made with the assumption that the termination of the water flow to the ice enabled the authors to assert that the frozen fracture of the porous bodies and of frost heaving of soil is the disjoining pressure of thin layers of unfrozen water and their pyro-crystallization flow.

The Phase Change Process and Properties of Saline Soil During Cooling

Detrimental frost heave and salt expansion may occur in saline soils of cold regions. The severity of these processes depends on the amount of salt precipitation and ice crystal growth in the pore solution at different temperatures. By employing nuclear magnetic resonance, the liquid water fractions in different concentrations of sodium chloride and sodium sulfate saline soils were measured at different temperatures. Based on the theory of solution phase diagram and phase change in porous media, the differences and similarities of phase change between pore solution and free solution were analyzed. The phase change sequence and effects of salt on frozen soils are also discussed. The theoretical and experimental results confirm that the phase diagram can reflect the phase change of pore solutions roughly, and pore size distribution is the cause of differences between the pore solution and free solution. Sodium chloride can mitigate the frost heave of soil, and frost heave and salt expansion occur together when the sodium sulfate soil is frozen.

REDUCTION IN TANGENTIAL FROST HEAVING FORCES BY THE PILE GEOMETRY CHANGE

The subject of research is shallow foundations in seasonally freezing soils. One of the main reasons of reaching by foundation structures limit states in the strength and position stability is such hazardous natural phenomenon as the frost heave of soils. The goal of this work is reduction of the negative effect of frost heaving forces on shallow foundations. The technique is suggested for protection of underground structures from the effect of the freezing soil. A bored pile with the upper inverted cone was developed allowing partial neutralization of tangential frost heaving forces due to the vertical component of frost heaving forces acting normally to the pile lateral surface. Use of the method will lead to increase in the life of structures, decrease in their erecting and operating cost.

Experimental measurement and numerical simulation of frost heave in saturated coarse-grained soil

A series of 1-D freezing experiments were conducted to simulate frost heave in saturated coarse-grained soil (CGS) with variable fines content. Visible frost heave occurred in CGS that contained a considerable fraction of fines when supplied by an external water source. Near the beginning of the experiments, a small amount of water was expelled, likely due to consolidation of the thawed portion of the sample. As time elapsed, the total amount of frost heave was proportional to the intake of water. Furthermore, frost heave increased linearly as the fines content increased. At higher fines content, frost heave occurred mainly due to water migration and segregated ice lensing. Finally, a simple finite element model that combined thermal and mechanical analyses based on Takashi's equation was developed. The model accurately reproduced experimental results and therefore can be used to simulate and predict frost heave in CGS.

Effect of hydro-thermal behavior on the frost heave of a saturated silty clay under different applied pressures

Abstract Civil engineering buildings are often damaged by frost heave of ground soils in cold regions. The hydro-thermal behavior is a key factor in determining frost heave of soils during freezing process. Moreover, the frost heave is also strongly affected by overburden pressure and external water source. Here, a series of one-directional freezing experiments with a water supply under different applied pressures were carried out to study the effect of hydro-thermal behavior on the frost heave of a saturated silty clay. Four different pressures were applied on the top of each soil sample, respectively, i.e. 50, 150, 300 and 500 kPa. The experimental results indicate that the frost heave of the supplied water is the main component of the total deformation for each soil sample with a water supply. However, the increased applied pressure can restrict water migration, and reduce frost heave during soil freezing process. Furthermore, for the saturated silty clay under different applied pressures, only when the advance rate of the freezing front drops to a critical value, the water intake begins. The start time of the water intake is also delayed with the increased applied pressure. Besides, the shut-off pressure of the saturated silty clay, at which no water flow into or out of the soil sample, is obtained based on the relationship between the critical advance rate of freezing front and the applied pressure.

The Construction of Transport Infrastructure on Permafrost Soils

The issues associated with freezing and thawing of soils in the subsoil of a complex of port facilities including transport infrastructure have been considered. The solution of thermal-physical problems of freezing, frost heave and thawing of soils has been made in spatial domain; the results of calculations are compared with the practical values. Numerical simulation of the problem of stability of structures on permafrost soils allowed predicting a possible soil thawing depth in time and optimizing the use of modern thermal insulation materials. The proposed calculation methods will provide reducing cost of development of transport infrastructure and port facilities under construction in the important northern regions of Russia.

FEATURES OF CALCULATION OF UNEVEN SWELLING SCREW PILES OF OIL AND GAS PIPELINES IN FROZEN GROUND

The article is devoted to the problem of buckling of helical piles and deformation of the superstructure of oil and gas pipelines under the action of forces of frost heaving of soils. Analyzed the characteristics of the nonuniform buckling of the piles. Revealed and substantiated the necessity of development of methods for the assessment of uniformity of buckling of piles on the distribution of frozen soils. On the basis of this study offers the calculation formula, taking into account the helical blade of the piles, the results of the calculations, built the graphical dependence, formulates relevant conclusions.

Characteristics and Prediction of Frost Heave of Saline Soil in Western Jilin Province

Characteristics and Prediction of Frost Heave of Saline Soil in Western Jilin Province

Development of a new method for checking frost heave in roads

The ground in Russia is frozen for between 2 and 9 months a year, resulting in a significant risk of frost heave damage – particularly on rural roads. While the standard solution is to use non-frost-susceptible materials up to the depth of frost penetration, such materials are not always readily available in the more remote parts of the country. This paper describes how research at universities in Saint Petersburg and Vologda has resulted in a new method for accurately predicting frost heave on roads built with frost-susceptible materials. The iterative method uses data from laboratory testing of frost heave in soils to determine the thickness of various grades of anti-frost layers that can then be incorporated in road construction to reduce heave. Russian regulations now allow the use of frost-susceptible materials for new road construction provided frost resistance has been calculated in accordance with the new method, resulting in significant cost savings.

Thermal-Hydro-Mechanical Analysis of Frost Heave and Thaw Settlement

AbstractFrost heave and thaw settlement are the cause of substantial damage to infrastructure in regions of seasonal freezing as well as seasonal thawing (permafrost). While frost heaving of soils has been researched for decades, less attention has been paid to quantitative estimates of settlement and loss of strength of soils due to thawing. A constitutive model is developed, capable of simulating freezing and thawing of soils, and associated changes in the soil strength. While the porosity growth parameters describing frost heaving have been calibrated and validated for a specific soil, the description of the thawing phase has not been validated due to a lack of experimental data. The yielding of the frozen soil is described using the critical state concept, with the pore ice content being an important parameter affecting the yield function. The model was calibrated using available laboratory test data and used in the simulation of a freezing–thawing cycle in the soil with embedded footing.

Methods of the transport tunnel protection from the frost heaving of soil based on the calculation of building structures

Methods of the transport tunnel protection from the frost heaving of soil based on the calculation of building structures

Experimental Study on the Influence of Different Cooling Rate to Frost Heave of Silty Clay

Freezing temperature is one of the main factors of soil frost heave, and different cooling modes will also have an effect on frost heave. To study the influence of stepwise cooling mode to frost heave of silty clay, this paper did the tests of frost heave on the silty clay in stepwise cooling mode and continuous cooling mode respectively, which got versus time of temperature gradient field and frost heave amount in the phenomena of frost heave and frost shrinkage by the two cooling modes. It turns out that stepwise cooling mode will produce greater frost heave and larger frost heave rate, and when frost shrinkage phenomenon occurs, the amount of frost shrinkage is bigger also. Its mechanism lies in the cooling rate with stepwise cooling mode is smaller than that with continuous cooling mode, and it can promote the water migration.

Numerical Simulation of Frost Heave in Soils around the Buried Oil Pipeline in Island Talik Permafrost Region

A systematic method to obtain the freezing characteristics and the amounts of frost heave in the soils around a buried oil pipeline in island talik permafrost region is presented on the basis of the simulation of soil temperature fields and a classic segregated potential frost heave model. The finite thermal effect domain and the equivalent heat capacity method were adopted to analyze the heat transfer process with phase change. The calculation parameters were derived from the China-Russia Crude Oil Pipeline engineering. The developments of the annual maximum freezing circles and frost penetrations emerging in typical years within the pipeline operation life cycle under different oil temperature, different thickness of thermal insulation layer, and different water content of soils were investigated. The maximum frost heaves in four typical sections of island talik were predicted. The results can be used to further mechanical calculation and can provide references for risk evaluation and site management of the buried pipelines in island talik permafrost regions.

Influence of Moisture Content to the Freeze-Thaw Performance of Roadbed in High-Cold Areas

Frost-heave and thaw-settlement of roadbed soil in highway will influence directly the durability, safe traffic flow and construction & maintenance costs in high-cold areas, therefore, recognizing and analysing the common embankment technologies of highway roadbed in high-cold areas accurately is significant to the effective controlling of project invest and the highway construction with limited funds in minority areas. The relations of Moisture Content and the freeze-thaw performances of roadbed fillers, subgrade soil were got respectively by experiments, and the results shows: Moisture Content has larger influence on the frost-heave and thaw-settlement performance of the soil. During the embankment of roadbed, the Moisture Content of fillers should be controlled nearby the optimum Moisture Content. The frost-heave and thaw-settlement occurs mainly in the subgrade soil, controlling the Moisture Content of subgrade soil is very important to improve the up-limit of frozen-soil, keep the stability of frozen-soil, control the thaw-settlement of roadbed and get rid of the roadbed diseases.

Numerical Calculation Method and Study for Frost Heave Deformation of Ground Heat Exchanger Pipe

For the frost heave deformation of ground heat exchanger with U-type heat exchanger pipe in subzero condition, a numerical calculation method was proposed by describing constitutive equations and establishing physical model. The finite element simulation study based on ABAQUS code was carried out to explore frost heave deformation behavior of saturated soil and interaction between pipe-soil interfaces ,focuses on the deformation of U-type pipe cause by saturated soil frost heave squeezing under the condition of different cooling rate.The distribution and change law of temperature,displacement, stress and strain on U-type heat exchanger pipe and soil were acquired.