Frost Heave Force Research Articles

A Simplified Viscoelastic Solution of the Frost Heaving Force of Cavity Water behind Tunnel Linings

With the high demand for construction of tunnels in China’s severe cold regions, the problem of frost heaving has become an important factor that endangers tunnel safety. This paper attempts to investigate the effect of frost heave of cavity water that widely exists in the tunneling engineering on the tunnel stability. According to the actual deformation of the surrounding rock of the tunnel, the viscoelastic behavior is considered to the surrounding rock. On the premise of the elastic solution of stagnant water frost heave, the viscoelastic solution of frost heaving pressure is deduced by Laplace transform using the generalized Kelvin model based on the elastic‐viscoelastic correspondence principle. The frost heaving force is analyzed through a case study with variations in the size of the cavity defect as well as the constitutive model parameters. It is concluded that the frost heaving force increases with the cavity defect size; over time, the frost heaving force gradually increases, but it will eventually stabilize. It is found that when the frost heaving force reaches a certain level, the surrounding rock with low strength or the lining with insufficient strength will crack, and the frost heaving force will not continue to increase.

Влияние антикоррозионного покрытия на величину касательных сил морозного пучения грунтов

Влияние антикоррозионного покрытия на величину касательных сил морозного пучения грунтов

Experimental Study on Normal Frost-Heave Force Generated from Loess upon Freezing considering Multiple Factors

An experimental study on the normal frost-heave force generated by loess was conducted by subjecting loess with various water contents and densities to different temperature conditions. The experimental results show that the interaction of the three factors has a significant effect on the normal frost-heaving force. Normal frost-heave force increases exponentially with an increase in dry density and linearly with a reduction in the freezing temperature or an increase in water content; of these factors, dry density has the greatest influence on frost-heave force, followed by water content then temperature. A frost-heave force model is developed that includes overall consideration of the interactions of water content, density, and temperature based on fitting of the test results. The value calculated with the model is in good agreement with values measured in verification tests, indicating that the model has high accuracy and can provide scientific guidance for engineering design in loess areas.

Experimental and Theoretical Determination of the Frost-Heave Cracking Law and the Crack Propagation Criterion of Slab Track with Water in the Crack

Crack propagation produced by frost heave affects the durability of slab-track structures in high-humidity and cold regions in China. This work is intended to reveal the evolution laws of frost-heave crack propagation, establish evaluation criteria for crack propagation, and investigate factors involved in frost-heave crack propagation. Firstly, by preparing slab-track specimens with initial cracks, an experiment of frost-heave crack propagation was designed. The process of frost-heave crack propagation was carried out by means of digital image correlation (DIC) technology and acoustic emission (AE) technology, respectively. These experiments revealed the evolution laws of generalized strain and AE events’ location during crack initiation and propagation, respectively, and the key parameters of micro-crack initiation strain and unstable propagation strain were obtained. By using theoretical and experimental analysis, a double-strain criterion for frost-heave crack propagation was proposed. Finally, factors involved in frost-heave crack propagation were investigated. The results show that crack initiation can be reflected by the crack-tip strain. The average micro-crack initiation strain and unstable propagation strain were found to be 224 με and 243 με, respectively. Moreover, it was found that the frost-heave crack propagation was caused by an ice plug which formed at the crack opening. When the crack width is larger than 2.7 mm and the external temperature is lower than −6.6 °C, cracks propagate easily under the frost-heave force.

Frost-heaving mechanical model for concrete face slabs of earthen dams in cold regions

Earthen dams are widely applied in the cold regions of northern China. However, the frost-heaving damage of concrete face slabs on the dam slopes is very serious under the dual effect of ice sheets and frost action during winter seasons. For this problem, a theoretical model is still lacking in the engineering design for water conservancy projects in cold regions. Starting with the study of the frost-heaving damage of concrete face slabs of earthen dams, this paper analyzes the damage types of the slabs under the effect of the static ice pressure and frost action, and clarifies the mechanism of the frost-heaving damage. The calculation method of the normal frost-heaving force of concrete face slabs is put forward, and a mechanical model suitable for the frost-heaving damage of concrete face slabs of earth-filled dams is established based on the mechanical analyses and engineering practice. The mechanical model can well explain the failure of frost heaving, extrusion and tensile strength of concrete face slabs under the double effect of the ice sheet and frost action, and a checking method for frost-heaving destruction is given. Finally, the mechanical model is used for the numerical analysis for an engineering example. The calculated results show that the model is reasonable and reliable, and it can provide theoretical basis for the design of concrete face slabs of earthen dams in cold regions.

Analysis of Temperature Field of Tunnel Surrounding Rocks in Freezing-Thawing Environment

On the background of large scale rocks engineering in cold regions, Temperature Field and Stress Field of Tunnel Surrounding Rock under the freeze-thaw environment are numerically analysed. According to the single temperature field equation of tunnel surrounding rock and Da Ban mountain tunnel project in Qinghai province as an example, large scale finite element software is used to simulate temperature distribution under freeze-thaw cycles, which is from the rising temperature to the decreasing temperature and from the rising temperature to the decreasing temperature again. The frost heaving force of the tunnel in the cold region is introduced and the mathematical model about rocks temperature field is also researched. Finally, finite element method is used to calculate the frost heaving force of rock tunnel in the cold regions. The results show that in the freezing and thawing environment, the area near the inner wall of the tunnel is more likely to be affected by the ground temperature and the effect of open ventilation and convection, and the temperature and stress changes more violently. In the design and construction of the cold regions, the influence of the frost heave force of the surrounding rock must be considered. Because freeze-thaw circles could cause the destruction of the tunnel structure, convective heat transfer will occur between tunnel mouth and walls and the environment, resulting in large temperature difference. Therefore, in order to reduce freeze-thaw disasters in the cold regions, we should consider the Protection measures about the hole and the wall. In this way, it reduces the range of freeze-thaw circles and prevent the convective heat transfer effectively.

Определение касательной силы морозного пучения грунтов: рекомендации

Определение касательной силы морозного пучения грунтов: рекомендации

Guidelines for determining tangential forces of frost heaving of soils.

Guidelines for determining tangential forces of frost heaving of soils.

Frost heaving of foundation pit for seasonal permafrost areas

Frost heaving can cause support structures to crack and even instability of the foundation pit. This paper describes the frost heaving features of the steel pile pre-stressed tendon composite foundation pit support system (SPPTCFPSS). As a combined rigid–flexible support system during the overwintering stage in Northeast China, these systems were used to investigate the transient heat conduction and fixed boundary one-dimensional frost heaving stress equations. The axial force sensors of the tendons used for the in-situ test accurately recorded the changing values of the axial forces of the pre-stressed tendons during the integrated working period for the foundation pit frost-heaving effect. Practical support data for the frost heaving stress analysis of the system were thus provided. The thermo-physical properties were obtained from the soil experiments, including the coefficient of thermal conductivity, specific heat of the foundation soil, and thermal expansion factor, among others. Base on this, the fluid effective velocity, saturation, and temperature fields were received from the heat flow coupling analysis of finite element methods (FEM).The results show that the actual axial force applied to the SPPTCFPSS is approximately equal to the theoretical value of the pit frost-heaving force calculated for the one-dimensional fixed boundary conditions corrected by saturation index from FEM. The SPPTCFPSS can adapt to a large-scale frost-heaving deformation to enable a reasonable increase in adaptive capacity in a region that has seasonal periods of frozen soil.

Freeze–thaw durability of air-entrained concrete under various types of salt lake brine exposure

The properties of air-entrained concrete (AEC) subjected to freeze–thaw cycles in various salt lake brines were investigated. The relative dynamic elastic modulus (RDEM) and weight loss of the AEC were measured after different numbers of freeze–thaw cycles. In addition, the microstructure and composition of the AEC under the combined action of freeze–thaw cycles and salt lake brine attack were analysed using X-ray diffraction and scanning electron microscopy. The results showed that the RDEM and weight losses of AEC subjected to freeze–thaw cycles in salt lake brines from Tibet and Inner Mongolia decreased sharply. For AEC immersed in salt lake brines from Qinghai and Sinkiang, the RDEM was slightly reduced and the weight loss was slightly increased. The coupling effect of freeze–thaw cycles and salt lake brine thus had only a slight influence on concrete damage in Sinkiang and Qinghai regions. The X-ray diffraction and scanning electron microscopy results demonstrated that only chemical corrosion occurred in the AEC under freeze–thaw action in the Qinghai and Sinkiang salt lake brines. However, the coupled effects of water frost-heaving force, salt crystallisation and chemical corrosion rapidly led to damage to the concrete under freeze–thaw action in the Tibet and Inner Mongolia salt lake brines.

Mechanical behavior and fracture spatial propagation of coal injected with liquid nitrogen under triaxial stress applied for coalbed methane recovery

Fracturing technology through liquid nitrogen (LN2) injection alters the physical properties of coal and rock masses because of the thermal and pressure effects. In order to investigate heat transfer and fracture propagation behaviors under in situ geological condition with LN2 injections, experimental work was conducted to study the LN2 induced rock/coal failures under true triaxial stress conditions. During the experiments, the temperature, ultrasonic waves, and acoustic emission location detection were monitored to determine the intensity and complexity of specimen failure under singular or cyclic LN2 injections. The results show that a single LN2 injection mainly transfers heat through the solid skeleton and only damages areas adjacent to the injection tube. However, cyclic injections formed a propagated fracture network and the heat can sequentially transfer further along the induced fractures. Moreover, plastic deformation occurred in the entire volume of the sample and the main fractures coalesced until the sample failed. Based on the spatial locations of the acoustic emission sources, the dynamic fracturing within the sample progressed after LN2 injection was clarified. The experimental results can provide evidences for the proposed crack propagation model for the coal masses. The research revealed that high-pressure nitrogen gas transferring liquid water to the tips of new fractures is essential for cyclic LN2 injection to form effective frost-heaving forces and fracturing. Therefore, the fracturing efficiency of the cyclic LN2 injection is far higher than that of singular LN2 injections.

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.

Study on Preliminary Design of the Transmission Towers’ Foundation in Arctic Permafrost Region

The design and construction of the foundation of transmission towers in permafrost regions is influenced by permafrost soil. Many characteristics of permafrost threaten the construction and safe operation of the transmission line engineering. These characteristics include frost heave, thaw settlement, and frost lifting, all of which have been aggravated by global warming and permafrost degradation. The principle applied in calculating the frost-heave force of the line tower foundation in permafrost regions is analyzed in this study based on the climate of both arctic and permafrost regions and on the characteristics of permafrost. The commonly used foundation types and the working conditions suitable for such types are also summarized.

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.

Coupled Thermo-Hydro-Mechanical Analysis of Freeze–Thaw Behavior of Pavement Structure over a Box Culvert

Evaluation of frost heave is essential for good design of a geotechnical structure in cold regions. Frost heave often causes severe roughness and cracking of structures like pavements. To model frost heave around a box culvert, a practical coupled thermo-hydro-mechanical (THM) model is presented. The performance of the proposed THM model, which can predict the freeze–thaw behavior of unsaturated soil, is demonstrated through frost heave tests under different conditions. A pavement structure located above a box culvert was simulated, and the analysis could reproduce phenomena observed in the field, including uneven upheave of the pavement and frost-heaving force induced by frost-susceptible backfill. To mitigate such damages, the mechanism and countermeasure of uneven frost heave were investigated. It was revealed that the freeze–thaw action considerably affects smoothness and failure of the pavement structure. In addition, the use of insulation may reduce roughness and extend the fatigue life of the pavement structure. The findings of this study are useful for minimizing frost heave in geotechnical structures.

Coupled effects of chemical environments and freeze–thaw cycles on damage characteristics of red sandstone

To study the influence of freeze–thaw cycles under complex chemical environments on the red sandstone, nuclear magnetic resonance (NMR) technology was used to analyze the damage evolution law of red sandstone. The freeze–thaw cycles were carried out on four groups of samples soaked in sulfuric acid solution, sodium hydroxide solution, sodium chloride solution and pure water, respectively. Further, NMR tests were performed on the samples and the porosity change of samples, T2 distribution and nuclear magnetic resonance images were analyzed. Results show that: (1) chemical environments have significant effects on the freezing-thawing damage, and the porosity increases linearly with increasing number of freeze–thaw cycles. (2) Under the frost-heaving force and ionic reactions, the T2 spectrum will successively shift towards the left and then to the right with increasing number of freeze–thaw cycles. Micropores will constantly appear, and small pores will dynamically expand into macropores. (3) With increasing number of freeze–thaw cycles, the areas of light spots in NMR images will increase gradually, which means that the damage degree is aggravated with continuous development of internal pores. (4) The samples soaked in sodium hydroxide solution and sodium chloride solution are damaged more seriously than those soaked in sulfuric acid solution and pure water. By analyzing and comparing the NMR characteristics of rock under the coupled effects of chemical environments and freeze–thaw cycles, more reliable test data will be available to study the damage mechanism of rock.

Reliability research on the 5-cm-thick insulation layer used in the Yuximolegai tunnel based on a physical model test

The Yuximolegai tunnel was built in the Tianshan mountain of Xinjiang. A 5-cm-thick insulation layer designed by engineering analogy was laid to project the surrounding rocks. To investigate the reliability of the design, a model test, primarily including a refrigeration system, a circulation system and a temperature control system, was developed. Two tests were designed and conducted: (1) a tunnel without insulation layer is studied using the freezing test; (2) a tunnel with a 5-cm-thick insulation layer is studied using the same test. The results show that the 5-cm-thick insulation layer employed in the field can only stop 86.5% of the lowest temperature to transfer to the surrounding rocks on average. On the basis of the analysis for the temperature law from in situ monitoring results and the model test results, the freezing depth is approximately 1.5–2m away from the lining. When the 5-cm-thick insulation layer is laid, the freezing depth still reaches 0.5m, which indicates that the preservation measure cannot fully protect the rocks surrounding the tunnel against freezing damage. In addition, comparing the frost heave force from the model test is found to have good consistency with the in situ test. The results obtained can serve as a guide for the design and the numerical simulation research of cold-region tunnels.

Stress and deformation characteristics of transmission tower foundations in permafrost regions along the Qinghai–Tibet Power Transmission Line

A transmission tower foundation embedded in frozen soil is subject to both the wind-induced uplift and frost heave forces. The frost heave results in an upward force acting on the foundation, while additional stress induced by the structure load may compress the underlying soils. The freezing- and thawing-induced deformations tend to cause further structural loads and lead to instability problems within the structure. To evaluate the engineering risk and ensure the safety of the Qinghai–Tibet Power Transmission Line (QTPTL) system, stress sensors were installed at the bases of two test tower foundations to investigate the stress state of the tower foundations. Using data on air and ground temperatures, and the deformation of tower foundations, we analyzed the stress variation, and the causes were discussed here. The results showed that the stresses at the bases of tower foundations had a close relationship with air and ground temperatures. The cooling of the underlying soils led to the occurrence of frost heave, which pushed the foundations upward and caused a significant stress bulb under the bases of tower foundations. Seasonal variations in the contact stress depended on the seasonal freezing and thawing of foundation soil. The contact stress increased with the cooling of the underlying soils and decreased with the warming of the underlying soils. The results also showed that the contact stress was free of the wind influence, i.e., the wind-induced uplift force was minor for the contact stress. To fully understand the influences of freezing and thawing on the stress state of tower foundations, a thermal–elasto-plastic finite element model for the tower foundation–soil system was established, and the stresses and deformations of a tower foundation subject to frost heave and thaw settlement were simulated. The results showed that the frost heave force induced by soil freezing potentially threatens the safety and normal operation of the QTPTL. Thaw settlement may lead to harmful deformation of tower foundations if global warming is considered in the numerical model. The remedial measure with thermosyphons only can reduce the settlement of the foundation and will increase the frost jacking risk of the foundation.

Study on the Model Test of Tunnel Lining Deformation Characteristic under the Frost Heaving Force

To study the lining deformation characteristic of the cold region tunnel under the frost heaving force, a model test was designed, and the low temperature environment in the tunnel of model was made by refrigeration equipment, the groundwater inside the model was frozen, the lining structure deformation characteristic under the frost heaving force was analyzed. The results show that the lining was distorted under the frost heaving force, the lining strain of the tunnel crown and side wall was greatly, the maximum strain is 122μ, the lining strains of inverted arch and foot of wall was less, the minimum strain is 25μ.

Experimental Study on Influence of Seasonally Frozen Ground on Horizontal Frost-Heave Force of Frozen Wall

To investigate the influence of seasonally frozen ground on frost-heave force of artificial frozen wall, 6 artificial frozen wall model tests were performed with different temperature of seasonally frozen ground on developed test platform. Experimental data indicate that compared with the final horizontal frost-heave force of artificial frozen wall without seasonally frozen ground, it increased 8.6% and 9.1% with-3°C and-12°C seasonally frozen ground layer, separately, and it shows that there is an important influence of seasonally frozen ground on the horizontal frost-heave force of artificial frozen wall. It also can be concluded that the lower the temperature of seasonally frozen ground is, the less the freezing time is and the bigger the final horizontal frost-heave force is, but, among all the model tests, the freezing time that is taken to get a stable state is the most for the artificial frozen wall without seasonally frozen ground , and its the final horizontal frost-heave force is the smallest.