Frozen Soil Area Research Articles

Sustainable stabilization/solidification of Cu-contaminated seasonal frozen soil by epoxy resin: environmental risk assessment and engineering applicability

There are significantly toxic Cu contaminants in seasonal frozen soil areas under industrial production and mineral exploitation. However, the hydration reactions of mainstream alkaline curing agents such as cement are disturbed by the solidification and thawing of moisture, and their solidification/stabilization is ineffective to heavy metals. Therefore, there is an urgent requirement to optimize the use of current curing agents to improve the solidification/stabilization (S/S) effect of Cu contaminants in seasonal frozen soil areas. In this study, the Epoxy resin (EP) with excellent waterproofing and frost resistance was incorporated into artificially prepared Cu-contaminated soil to maintain a steady engineering application strength and inhibit the outward diffusion of toxic Cu contaminants under freeze-thaw cycles. The freeze-thaw resistance of EP-cured Cu-contaminated soil and the feasibility of EP remediation technology have been investigated, including mechanical properties, environmental effects and microstructure. The decline in mechanical strength and the increment in Cu leaching during freeze-thaw cycles are effectively suppressed by the remediation of EP. Even after 8 freeze-thaw cycles, there is merely a mechanical strength decline of 5%, solely a secondary Cu leaching of 4.74mg/L, and astonishingly a leachable index of 11.70 in the specimens with 12% EP dosage. The expansion phenomenon of pores and clay fractures under freeze-thaw cycles were gradually alleviated after incorporation of EP. The above results demonstrate the Cu-contaminated seasonal frozen soil remedied by EP are high-strength, basically non-toxic, and environmentally friendly material which are suitable for in-situ stabilization/solidification in seasonal frozen soil areas.

Study on the mechanical properties, thermal properties, and microstructure of phase change concrete (PCC): The application of active frost resistance of concrete in frozen soil areas

This paper addresses the issue of freezing damage to concrete structures in regions with frozen soil and overcomes the limitations of traditional frost resistance enhancement methods by integrating both active and passive frost resistance strategies. A novel low-temperature phase change concrete (PCC) is developed using specially designed phase change aggregates and fly ash to replace gravel and cement, respectively. Macroscopic mechanical tests are employed to investigate the evolution of the mechanical properties of PCC. The temperature control capabilities of PCC are quantitatively assessed through thermal physical parameters, heat storage and release curves, and infrared thermal imaging, alongside the introduction of a temperature damping indicator to elucidate the mechanisms underlying active frost resistance enhancement. Furthermore, XRD NMR, and SEM are utilized to further explore the influence of fly ash and phase change aggregates on the microstructural characteristics of PCC. The results show that the addition of phase change aggregates can reduce the strength, porosity, and ductility of concrete. The PCC prepared by mixing phase change aggregates with fly ash demonstrates effective temperature control performance while maintaining satisfactory mechanical properties. The noticeable temperature plateau around 0 °C in the heat storage and release curve, along with the multi-layered annular flare distribution observed in infrared thermal imaging, suggests that the temperature damping effect significantly mitigates the freeze-thaw impact experienced by PCC. Overall, the A-8 sample, with 20 % phase change aggregate and 30 % fly ash added, exhibits the most favorable comprehensive performance, showing reductions of 2.63 %, 39.57 %, and 33.04 % in uniaxial compressive strength, porosity, and maximum temperature difference, respectively, compared to the control group, along with a 75.62 % increase in relative temperature damping.

Analysis on the cooperative variation law of pile-soil temperature field in Island permafrost region

To determine the cooperative variation laws of temperature fields in bridge concrete piles and the surrounding frozen soil during the freezing process in high-latitude, low-altitude insular permafrost regions, we utilized a practical bridge construction project within the frozen soil area of the Daxing'an Mountains, China. This served as the foundation for developing a method to remotely and dynamically monitor the temperatures of piles and soil in permafrost regions, enabling continuous, automatic monitoring of pile-soil temperature data. Employing this automatic temperature monitoring system, we collected temperature data from two 15-m-long concrete bored piles before and after freezing, and monitored the freezing process of the pile foundations in real-time. The cooperative variation laws of the pile-soil temperature field over time were summarized, and a calculation equation for the pile foundation's freezing time was established based on finite element analysis results. Monitoring and analysis reveal that under the influence of the frozen soil temperature field, the pile foundation initially freezes from the bottom up in a unidirectional manner. When the atmospheric temperature falls below 0 °C, the pile foundation freezes simultaneously from both the upper and lower directions. Post-freezing, the internal temperature of the pile body aligns with the surrounding soil temperature, with a temperature difference of less than 0.1 °C at the same depth. For similar in-place temperatures, the freezing time for a test pile with a 1.2m diameter is 1.14 times that of a 1.0m diameter test pile. The range of the hydration heat effect of cement concrete extends 1–2 times the pile diameter.

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

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

Seasonal frozen soil area frame beam anchor rod slope support structure frost heave mechanical characteristics simplified calculation model

Seasonal frozen soil area frame beam anchor rod slope support structure frost heave mechanical characteristics simplified calculation model

Application of New Polymer Soil Amendment in Ecological Restoration of High-Steep Rocky Slope in Seasonally Frozen Soil Areas.

In seasonally frozen soil areas, high-steep rocky slopes resulting from open-pit mining and slope cutting during road construction undergo slow natural restoration, making ecological restoration generally challenging. In order to improve the problems of external soil attachment and long-term vegetation growth in the ecological restoration of high-steep rocky slopes in seasonally frozen areas, this study conducted a series of experiments through the combined application of polyacrylamide (PAM) and carboxymethyl cellulose (CMC) to assess the effects of soil amendments on soil shear strength, water stability, freeze-thaw resistance, erosion resistance, and vegetation growth. This study showed that the addition of PAM-CMC significantly increased the shear resistance and cohesion of the soil, as well as improving the water stability, freeze-thaw resistance, and erosion resistance, but the internal friction angle of the soil was not significantly increased after reaching a certain content. Moderate amounts of PAM-CMC can extend the survival of vegetation, but overuse may cause soil hardening and inhibit vegetation growth by limiting air permeability. It was observed by a scanning electron microscope (SEM) that the gel membrane formed by PAM-CMC helped to "bridge" and bind the soil particles. After discussion and analysis, the optimum application rate of PAM-CMC was 3%, which not only improved the soil structure but also ensured the growth of vegetation in the later stage under the optimum application rate. Field application studies have shown that 3% PAM-CMC-amended soil stably attaches to high-steep rocky slopes, with stable vegetation growth, and continues to grow after five months of freeze-thaw action, with no need for manual maintenance after one year.

Effects of coupled biochar and snow cover on soil carbon components and CO2 emissions in seasonally frozen soil areas under climate change conditions

Global warming is profoundly altering soil freeze–thaw cycle (FTC) patterns, and the formation of different thicknesses and durations of snow cover by snowfall results in heterogeneity of environmental and biological factors, which can have complex effects on soil water and carbon cycle processes. In order to better develop rational regulation strategies to increase the potential of soil carbon sequestration and emission reductions under climate change conditions, a three-year in situ control trial of field snow was set up to simulate climate scenarios using two treatments: snow removal and natural snow. The effects of FTCs and biochar on soil CO2 emission flux (CO2 Flux) were analyzed by constructing a driven coupling model between soil hydrothermal environmental factors, unstable organic carbon components and stable organic carbon components. The results showed that CO2 Flux decreased by 9.36% to 11.34% for 1% biochar treatment, while CO2 Flux increased by 15.41% to 18.32% for 2% biochar treatment. Moreover, the snow removal treatment increased CO2 Flux by 9.86% to 13.99% compared to the natural snow treatment. The snow during freezing and thawing has a dual effect on soil hydrothermal dynamics, with snow removal making the freeze–thaw action more intense in perturbing the soil carbon matrix, while the interfacial behavior of biochar with soil minerals protects the stability of the soil structure. Biochar reduces soil carbon emissions thanks to its highly stabilized components and unique surface structure, which enhances the carbon sequestration and emission reduction effect by increasing the proportion of inert organic carbon, promoting the formation of organic–inorganic complexes, and encapsulating and adsorbing soil organic matter. The results of the study can provide important theoretical support and practical models for the assessment of the environmental effects of biochar and the reduction of carbon sequestration in agriculture under climate change conditions.

Evaluating annual soil carbon emissions under biochar-added farmland subjecting from freeze-thaw cycle

Straw biochar is a commonly recognized agricultural amendment that can improve soil quality and reduce carbon emissions while sequestering soil carbon. However, the mechanisms underlying biochar's effects on annual soil carbon emissions in seasonally frozen soil areas and intrinsic drivers have not been clarified. Here, a 2-y field experiment was conducted to investigate the effects of different biochar dosages (0, 15, and 30, t ha−1; B0 (CK), B15, and B30, respectively) on carbon emissions (CO2 and CH4) microbial colony count, and soil-environment factors. The study period was the full annual cycle, including the freeze-thaw period (FTP) and the crop growth period (CP). Structural equation modeling (SEM) was developed to reveal the key drivers and potential mechanisms of biochar on carbon emissions. Biochar application reduced soil carbon emissions, with the reduction rate positively related to the biochar application rate (B30 best). During FTP, the reduction rate was 11.5% for CO2 and 48.2% for CH4. During CP, the reduction rate was 17.9% for CO2 and 34.5% for CH4. Overall, compared with CK, B30 treatment had a significant effect on reducing total soil carbon emissions (P < 0.05), with an average decrease of 16.7% during the two-year test period. The study also showed that for soils with continuous annual cycles (FTP and CP), carbon emissions were best observed from 10:00–13:00. After two years of freeze-thaw cycling, biochar continued to improve soil physical and chemical properties, thereby increasing soil microbial colony count. Compared with B0, the B30 treatment significantly increased the total colony count by 74.3% and 263.8% during FTP and CP (P < 0.05). Structural equation modeling (SEM) indicated that, with or without biochar application, the soil physicochemical properties directly or indirectly affected soil CO2 and CH4 emission fluxes through microbial colony count. The total effects of biochar application on CO2 emission fluxes were 0.50 (P < 0.05) and 0.64 (P < 0.01), respectively, but there was no significant effect on CH4 emission fluxes (P > 0.05). Among them, soil water content (SWC), soil temperature (ST) and soil organic carbon (SOC) were the main environmental determinants of CO2 emission fluxes during the FTP and CP. The total effects were 0.57, 0.65, and 0.53, respectively. For CH4, SWC, soil salinity (SS) and actinomycete colony count were the main environmental factors affecting its emission. The total effects were 0.50, 0.45, 0.44, respectively. For freeze-thaw alternating soils, the application of biochar is a feasible option for addressing climate change through soil carbon sequestration and greenhouse gas emissions mitigation. Soil water-heat-salt-fertilization and microbial communities are important for soil carbon emissions as the reaction matrix and main participants of soil carbon and nitrogen biochemical transformation.

Response of soft rock and sand compound soil structure to freeze-thaw cycles in Mu Us Sandy Land, China

In order to accurately understand the relationship between soil structure and climate feedback in the frozen soil area of Mu Us Sandy Land, China, and to explore the key control factors for the structural stability of soft rock and sand compound soil under freeze-thaw environment, the indoor freeze-thaw simulation experiment was applied. The results show that the freeze-thaw period, clay content, organic matter and their interactions have significant effects on the stability of composite soil aggregates. After 10 freeze-thaw cycles, the aggregate content in the 1:0, 1:1, 1:2, and 1:5 composite soil with a diameter greater than 1 mm decreased by 55%, 34%, 44%, and 57%, while the aggregate content with a diameter less than 1 mm increased by 91%, 70%, 66%, and 87%, and the aggregate composition of each particle size is mainly concentrated in the range of 0.25–0.5 mm. Under freeze-thaw conditions, the changes of clay and aggregate content in different proportions of composite soil is the same, all showing 1:1&amp;gt;1:2:&amp;gt;1:5, and 1:1 composite soil with &amp;gt;0.25 mm aggregate content is the highest. Under freeze-thaw alternations, 1:1, 1:2 and 1:5 composite soil aggregates (&amp;lt;0.5 mm) showed a significant positive correlation with soil organic matter, while there is no significant correlation between large aggregates (&amp;gt;1 mm) and soil organic matter. In conclusion, the freeze-thaw cycle reduces the structural stability of composite soil aggregates, and clay are the key controlling factors for the formation and structural stability of composite soil aggregates.

Experimental study and numerical simulation verification of the macro- and micromechanical properties of the sandstone–concrete interface under freeze–thaw cycles

In cold-region tunnel engineering, the bonding surface between concrete and surrounding rock is highly susceptible to engineering disasters such as the cracking of support structures under the influence of freeze-thaw cycles, which severely affects the stability of tunnel engineering. This study investigates the macroscopic and microscopic mechanical properties of the sandstone–concrete interface under freeze–thaw cycles and reveals the microdamage and fracture evolutionary laws during the freeze–thaw loading process via the coupled expansion of water–ice particle phase changes via particle flow numerical simulation methods, aiming to provide theoretical support for the design and construction of rock–soil and tunnel engineering in high-altitude frozen soil areas. The results indicate that the interface strength characteristics of the sandstone–concrete specimens exhibit a stable decreasing trend with an increase in the number of freeze-thaw cycles and a decrease in roughness. Taking the most unfavorable condition as an example, the exacerbation of freeze-thaw deterioration resulted in shear strength reductions of 16.53%, 27.01%, and 37.17% for specimens (JRC=3.727), while an increase in roughness led to shear strength increases of 11.00% and 15.14% for specimens (NT=60 cycles). The acoustic emission characteristics during the loading process of the sandstone–concrete interface specimens reflect the microcracking evolutionary activity of the specimens quite well, and setting 1.0 as the recommended value for the precursor determination of the b-value and CV(k) index is most reasonable. Under freeze-thaw cycles, cracks first initiate partial microcracks at the interface and on the outer side of the specimen, primarily dominated by tensile cracks and evolving with a "slow–fast" trend toward both sides of the interface. Under shear stress, particles at the interface first undergo slip dislocation due to their lower bonding strength, generating cracks, subsequently inducing significant displacement of particles on both sides of the interface, resulting in crack propagation toward both sides of the interface, ultimately penetrating and forming shear bands leading to macroscopic failure.

Wavelet denoising of fiber optic monitoring signals in permafrost regions.

To address the noise issue in fiber optic monitoring signals in frozen soil areas, this study employs wavelet denoising techniques to process the fiber optic signals. Since existing parameter choices for wavelets are typically based on conventional environments, selecting suitable parameters for frozen soil regions becomes crucial. In this work, an index library is constructed based on commonly used wavelet basis functions in civil engineering. An optimal wavelet basis function is objectively selected through specific criteria. Considering the characteristic of small root mean square error in fiber optic signals in frozen soil areas, a multi-index fusion approach is applied to determine the optimal decomposition level. Field observations validate that denoised signals, with parameters set appropriately, can more accurately identify locations where settlement occurs.

Application of computer technology to numerical simulation of hydrothermal variation of subgrade enhanced by seepage drainage geoglage under freeze-thaw cycle

In seasonal frozen soil areas, engineering problems are common due to the high water content of subgrade soil. In view of this phenomenon, a new type of percolating drainage geogrid (SDG) is proposed for cooling and drainage. The changes of soil temperature and moisture at different time points were analyzed through computer simulation laboratory model test, and the changes and distribution of soil temperature and moisture under freeze-thaw conditions were obtained. The temperature and moisture changes and their distribution obtained by computer modeling agree with the experimental results. By optimizing the soil materials of the model samples, the changes of temperature and moisture with time under freeze-thaw conditions were more significant. Therefore, it can be inferred that, without changing the configuration of the percolation drain grid, the cooling drainage performance of the percolation drain grid can be improved under the same conditions by changing the heat transfer coefficient or the macroporous filling material. It provides theoretical support and data guarantee for the reinforcement of subgrade percolation and drainage grid in cold area.

Study on the formation mechanism and preventive measure of pot cover effect for subgrade in seasonal frozen soil area under freeze–thaw cycles

AbstractThe presence of an impervious cover layer inhibits the free evaporation of moisture in the soil during seasonal freeze–thaw cycles, leading to a phenomenon known as the pot cover effect. This can result in severe frost heave issues in airport runways, highway subgrades, railway subgrades, and other similar infrastructure. In this study, a disease investigation was conducted at a gas transmission station situated in an area with seasonally frozen soil. Meanwhile, the causes of moisture accumulation and frost heave in the lower part of concrete pavement slabs were analyzed. A coupled water–vapor–heat model for unsaturated frozen soil is then established to analyze the formation mechanism of the pot cover effect in the subgrade. Finally, the preventive effect of the impervious layer on moisture migration in the pot cover effect was analyzed. The results indicate that the pot cover effect causes a significant accumulation of moisture beneath the concrete pavement at the gas transmission station, resulting in a moisture content increase of 5%–35%. During the freezing period, the vapor of shallow soil migrates upward, while the liquid water remains unchanged. During the melting period, both vapor and liquid water migrate downward. The laying of the impervious layer can prevent moisture migration of the pot cover effect. When the impervious layer is placed on the freezing front (0°C), the prevention effect of the pot cover effect is the best.

Experimental study on progressive interfacial mechanical behaviors using fiber optic sensing cable in frozen soil

Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction. Optical frequency domain reflectometry (OFDR) based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas, where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy. In this paper, a series of pullout tests were conducted on fiber optic (FO) cables embedded in the frozen soil to investigate the cable‒soil interface behavior. An experimental study was performed on interaction effects, particularly focused on the water content of unfrozen soil, freezing duration, and differential distribution of water content in frozen soil. The high-resolution axial strains of FO cables were obtained using a sensing interrogator, and were used to calculate the interface shear stress. The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models. Three freezing periods, correlating with the phase change process between ice and water, were analyzed. The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times. A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information. Additionally, the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements. This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil, which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.

Solidification/Stabilization of Chromium-Contaminated Soils by Polyurethane during Freeze-Thaw Cycles: Mechanical, Leaching and Microstructure Characterization.

The treatment of chromium-contaminated soil in seasonal frozen soil areas has been the subject of recent interest. Polyurethane (PU), as a polymer material with excellent freeze-thaw resistance and abrasion resistance, has the potential to solidify Chromium-Contaminated soil in seasonal frozen soil areas. However, there is a lack of research on the mechanism of PU involved in solidifying/stabilizing chromium-contaminated soil in seasonal frozen regions from the perspective of pore structure and functional group coordination bonds. In this study, the leaching behavior of PU with different contents under different freeze-thaw cycles was analyzed, and the mechanism of PU in seasonal frozen regions was explored from the perspective of pores and functional groups by combining various microscopic characterization methods. The results show that PU can effectively resist the deterioration of chromium-contaminated soil after freeze-thaw cycles and can better prevent the harm of secondary leaching. The leaching concentration of chromium ion is only 1.09 mg/L, which is below China's regulatory limits. PU is beneficial for inhibiting the expansion of ice crystals in chromium-contaminated soil in seasonal frozen soil areas. PU solidifies chromium by physical encapsulation and complexation reactions. The amide functional groups, methyl-CH3 and isocyanate groups in PU play a leading role in the complexation with chromium. Although the freeze-thaw cycle will destroy the coordination bond between the PU functional group and chromium, chromium cannot break through the bond of PU film. This study confirmed the feasibility of using PU to solidify Chromium-Contaminated soil in seasonal frozen soil areas, which can provide research support and reference for in situ engineering in the future.

Soil environment, carbon and nitrogen cycle functional genes in response to freeze-thaw cycles and biochar

Freeze-thaw cycles (FTCs) are a common phenomenon in seasonal frozen soil areas, which can significantly affect the changes in the soil environment and functional genes of microorganisms. To explore the effect of biochar application on soil carbon and nitrogen cycling under FTCs, an indoor soil column simulation test was used in this study. The experimental setup included different application rates of biochar (0%, 1%, 2%), with the carbon and nitrogen cycle functional genes serving as indicator genes. Real-time fluorescence quantitative PCR technology was employed for analysis. Based on the correlation heat map and redundancy analysis (RDA), the response mechanism of soil environment changes and carbon and nitrogen cycle functional genes before and after FTCs was analyzed. The results revealed that the application of biochar significantly increased soil's water-holding capacity held available nutrients in soil, and increased the ability of environmental change. Due to the influence of soil moisture and aeration, biochar reduced the variation of soil carbon sequestration gene cbbL, cbbM, and nitrogen fixation gene nifH abundance after FTCs. The application of 2 % biochar significantly increased the abundance of the nitrification gene amoA and denitrification gene nirK and enhanced the respiration of soil microorganisms. Soil moisture (SM) is the main environmental factor that determines the abundance changes of the soil carbon sequestration genes cbbL and cbbM. Soil organic matter (SOM), pH, nitrate nitrogen (NO3−-N), and ammonium nitrogen (NH4+-N) were the main environmental factors determining the abundance of soil nitrogen fixation gene nifH, nitrification gene amoA, and denitrification gene nirK. This study can provide new insights into the internal mechanism of the soil carbon and nitrogen cycle in seasonal frozen soil areas, and provide some reference for the rational application of biochar and the efficient utilization of water and soil resources in seasonal frozen soil areas in the future.

Experimental study on the dealkalization of red mud using the freeze-thaw and acid washing method

The strong alkalinity of red mud is a key reason that threatens the environment and restricts the secondary use of red mud. Freeze-thaw (FT)-acid washing (AW) is proposed to remove alkali to improve the dealkalization efficiency of red mud. FT-AW tests were performed using red mud with oxalic acid (OA) and citric acid (CA) to examine the effect of FT cycles and eluent concentration on the dealkalization efficiency. Results showed that the FT-AW method significantly increased the dealkalization efficiency under the synergy of FT and AW. After 5 times of FT-AW, the alkali removal efficiencies of red mud with OA and CA as eluents reached 97.5% and 95.5%, which were 27.3% and 18.9% higher than those of the control group, respectively. The effect of OA on dealkalization was more sensitive than that of CA. The results of SEM-EDS and XRD showed that FT cycles destroyed the crystal structure of red mud and released part of the bonded alkali. The FT-AW method provides a novel idea for future large-scale red mud dealkalization by using FT alternation in seasonally frozen soil areas.

Study on the Damage of Permafrost to Tower Foundations in Permafrost Regions

The tower foundation is an important component of the tower grounding device. The conditions in permafrost areas are relatively harsh, and damage to the foundation can affect the grounding performance of the grounding device. However, the damage characteristics of permafrost to the tower foundation in permafrost areas are not yet clear, and effective protection of the foundation cannot be achieved. Based on this, this article constructs a simulated frozen soil experimental platform through experiments, replacing the tower foundation with concrete specimens. The electrical and mechanical properties after freeze-thaw were measured using the quadrupole method and resonance method, respectively. The self performance of the tower foundation under different moisture content freeze-thaw conditions was studied, and the performance change law of the tower foundation after freeze-thaw was obtained to explore the damage of frozen soil to the tower foundation in frozen soil areas. It can be considered that the frozen soil in permafrost areas does not cause significant damage to the tower foundation itself in a limited number of years.

Groundwater flow process in frozen soil areas and its relationship with surface water transformation

Groundwater flow process in frozen soil areas and its relationship with surface water transformation

Experimental study on mechanical behavior deterioration of undisturbed loess considering freeze-thaw action

To solve the problem that the mechanical behavior of undisturbed loess in seasonally frozen soil area is affected by freeze-thaw action, triaxial shear tests of undisturbed loess under freeze-thaw condition were carried out. The results show that the mechanical properties of undisturbed loess are greatly affected by factors including freeze-thaw process, water content, natural density and confining pressure. Freeze-thaw action has a certain impact on the failure surface shape and stress-strain curve. Before and after freeze-thaw, the shape of the shear failure surface is complex, including single oblique failure surface, double oblique failure surface, vertical failure surface, X-shaped failure surface, bulging failure, etc. And under the conditions of low water content, low confining pressure and high dry density, the stress-strain curve tends to be softened. Conversely, the curve tends to harden. Freeze-thaw action can make the stress-strain curve transition from softening to hardening. In addition, the freeze-thaw action significantly weakens the failure strength, shear strength, cohesion, initial tangent modulus and failure ratio of undisturbed soil, but does not change the internal friction angle obviously. Also, the heterogeneity of natural soil is also an important factor affecting the mechanical parameters, failure surface shape and stress-strain curve of undisturbed loess.