Search

The occurrence of preset flaws can influence the mechanical, physical, and other related properties of rock samples. To study the failure characteristics and crack growth of rock samples containing spatial-rotation (SR) fissures subjected to freeze–thaw (FT) cycles and loading, laboratory tests of SR fissured red sandstone under various factors were conducted. The frost heave pressure, creep deformation, P-wave velocity and damage variable of SR fissured rocks were monitored and analysed. Failure processes and 3D fracture patterns of the specimen were studied in great detail using Digital Image Correlation (DIC) and Acoustic Emission (AE) technologies. Based on the experimental results, a damage constitutive model of the SR fissured rocks under the freeze–thaw and loading (FT-L) was explored. The results revealed that the frost heave pressure can be classified into five types: hibernation, growth, eruption-stabilization, fluctuation, and dissipation. In addition, with the increase of initial damage and temperature (absolute value), the corresponding wave and creep curves increase gradually. Under the coupling of FT cycle and load at each stage, the damage variable exhibited a U-shaped change trend, and gradually increases with the increase of load level. It is worth noting that, the fracture pattern of rock bridge can be classified into three fundamental types (progressive, undulating and opening fracture). A new nonlinear damage constitutive model containing the Nishihara model and a rheological element was established in which the coupling model can characterize the whole creep process of SR fissured red sandstone under the combined action of FT cycles and creep loading. Thus, the proposed model is a very good tool for the analysis of load coupling problems involved in the slope of cold area. Highlights: The compression tests of spatial-rotation fissured sandstone under the freeze–thaw and loading were carried out. The progressive damage process of sandstone with a spatial-rotation fissure was given. The 3D fracture patterns containing rock bridge extension and fissure penetration were revealed. A damage rheological model that considers the temperature and load was established. [ABSTRACT FROM AUTHOR]

The phenomenon of water–ice phase transition in frozen soils is the key to explaining the mechanism of frost heaving and thawing settlement disaster. However, numerical analysis of water–ice phase transitions in frozen soils at mesoscale is rarely reported. This study combines the modified Gibbs-Thomson equation and the enthalpy-based lattice Boltzmann model, and develops a mesoscale numerical method to simulate the water–ice phase transition in the local pores of saturated frozen soil during freezing and thawing process. In order to accurately simulate this process, a new η coefficient is proposed to modify the Gibbs-Thomson equation, which is unrelated to the type of soil sample and gradation characteristics. According to the particle size distribution curve, the two-dimensional random circle generation method is used to reconstruct the soil pore structure. The freezing and thawing processes are verified with the experimental data. A larger non-uniformity coefficient Cu and curvature coefficient Cc of the grain size distribution result in a lower degree of subcooling and lower residual water content of the soil during the freezing process. The new model provides an effective means to understand the water–ice phase transition in frozen soil at a mesoscopic scale. [ABSTRACT FROM AUTHOR]

• A new elastoplastic model of the double-layer plastic zone in cold region tunnels. • Revealing the distribution law of double-layer plastic failure zone. • Considering the non-uniform frost heave of rock caused by the temperature gradient. • The outer plastic layer has a significant effect on the stress of the lining. The frost heave force and the plastic zone caused by the frost heave of the surrounding rock are the primary causes of tunnel frost damage. Current research mainly focuses on the plastic damage caused by the frost heave rock zone on the inner layer rock, while neglecting the damage caused by the outer layer rock. It will not accurately evaluate the stability of tunnels in cold regions. A new elastoplastic calculation model of the tunnel surrounding rock double-layer plastic zone in cold regions is proposed to reveal the failure law of the surrounding rock under frost heave based on thermodynamics and elastic-plastic mechanics theory. The stress field and radius of the surrounding rock in the two-layer plastic zone are determined using the Unified Strength Theory. The radius and stress distribution of the double-layer plastic zone obtained by the theoretical solution are in accordance agreement with the numerical calculation, which verifies the correctness of the theoretical solution. The case analysis of the Yuximolegai Tunnel shows that the thicknesses of the inner and outer plastic zones of the surrounding rock reach 0.57 and 2.34 m, respectively. The outer plastic zone caused by non-uniform frost heaving of the surrounding rock has a larger influencing range than the inner plastic zone. The double-layer plastic zone expands rapidly with the increase in the volumetric frost heave coefficient and elastic modulus of the surrounding rock, but are significantly suppressed by the in-situ stress. The influence of lining thickness and non-uniform frost heave coefficient on the plastic zones is relatively minor, yet their impact on the frost heave force should not be overlooked. [ABSTRACT FROM AUTHOR]

The efficiency of geosynthetics has been proven in stone column-reinforced foundations. In this paper, loading tests were conducted on three stone column-reinforced foundations, experiencing four freeze-thaw cycles. The effects of geosynthetic encasement and lateral reinforcement were investigated on the behavior of ordinary stone column (OSC) – reinforced and geosynthetic encased stone column (GESC) – reinforced foundation. The results showed that particles of OSCs spread into foundation soil during freezing and thawing, and top of OSCs were replaced by foundation soil. The temperature gradient along the depth in OSC-reinforced foundation was smaller than in GESC-reinforced foundations, resulting in a lower negative pore pressure at the beginning of freezing. However, it was found that geosynthetic encasement helped maintain the integrity of GESCs, and increased the stress concentration ratio (SCR) during thawing, which led to a lower excess pore pressure in GESC-reinforced foundations. The lateral reinforcement was also found to not only reduce the differential settlement between GESCs and soil during thawing, but also restrain the frost heave during freezing. The tensile membrane effect of lateral reinforcement redistributed the stress and the overburden pressure throughout the freeze-thaw process. More water moved upwards during freezing in the OSC-reinforced foundation, leading to a larger amount of frost heave. However, the moisture migration became complex in the OSC-reinforced foundation, as OSCs were damaged by freeze-thaw cycles. • This paper studied the behavior of GESC-supported embankment under freeze-thaw cycles. • The effects of geosynthetics encasement and lateral reinforcement were investigated in partially frozen ground. • Encasement helped keep entity of stone columns, and enhanced the bearing capacity. • Lateral reinforcement redistributed stress on column and soil in both freezing and thawing. • Lateral reinforcement restrained frost heave, and reduced differential settlement between column and soil. [ABSTRACT FROM AUTHOR]

Compared to traditional tunnel construction, artificial freezing involves two distinct stages: freezing and thawing. However, this process can pose a risk to the surrounding environment if it is not possible to accurately analyze the frost heave and thawing settlement during the freezing process. The thermomechanical coupled mathematical model of formation frost heave was established by considering boundary conditions, such as formation temperature and convective heat transfer, and introducing the parameters of instantaneous volumetric strain and denaturation characteristic coefficient. In addition, the numerical analysis method for the whole construction process of the tunnel by the horizontal freezing method was established by programming the user subroutine that takes into account the characteristic coefficients of frozen soil relying on the secondary development technology of ABAQUS (version 2022). Then, the method was applied to the horizontal freezing engineering of a double-line tunnel, and the distribution laws of the freezing temperature field and frost heave displacement field were obtained and compared with the field measurement results. The numerical analysis method for determining the deformation law of the ground surface has been shown to be reliable through comparison with field measurements. This method can serve as a reference for designing effective ground surface heaving control schemes during the freezing construction period of tunnels in complex environments. [ABSTRACT FROM AUTHOR]

Differential interferometric synthetic aperture radar (InSAR) is a remote sensing technique for measuring surface displacements with precision down to millimeters, most commonly from satellites. In permafrost landscapes, InSAR measurements can provide valuable information on geomorphic processes and hazards, including thaw subsidence and frost heave, thermokarst, and permafrost creep. We first review recent progress in InSAR data availability, InSAR processing and uncertainty analysis methods relevant to permafrost studies. These technical advances have contributed to our understanding of surface deformation in flat and sloping terrain in polar and mountainous regions. We emphasize two emerging trends. First, InSAR increasingly enables insight into the mechanisms, controls, and drivers of permafrost landscape dynamics on subseasonal to decadal time scales. Second, InSAR observations in conjunction with models enable novel ways to infer subsurface parameters, such as near‐surface ground ice content and active layer thickness. We anticipate that in the coming decade, InSAR will mature into a widely used operational tool for monitoring, modeling, and planning across rapidly changing permafrost landscapes. [ABSTRACT FROM AUTHOR]

Water migration behavior is the main cause of engineering disasters in cold regions, making it essential to understand its mechanisms and the resulting mechanical characteristics for engineering protection. This study examined the water migration process during soil freezing through both experimental and numerical simulations, focusing on the key mechanical outcomes such as deformation and pore water pressure. Initially, a series of controlled unidirectional freezing experiments were performed on artificial kaolin soil under various freezing conditions to observe the water migration process. Subsequently, a numerical model of water migration was formulated by integrating the partial differential equations of heat and mass transfer. The model's boundary conditions and relevant parameters were derived from both the experimental processes and existing literature. The findings indicate that at lower clay water content, the experimental results align closely with those of the model. Conversely, at higher water content, the modeled results of frost heaving were less pronounced than the experimental outcomes, and the freezing front advanced more slowly. This discrepancy is attributed to the inability of unfrozen water to penetrate once ice lenses form, causing migrating water to accumulate and freeze at the warmest ice lens front. This results in a higher ice content in the freezing zone than predicted by the model, leading to more significant freezing expansion. Additionally, the experimental observations of pore water pressure under freeze–thaw conditions corresponded well with the trends and peaks projected by the simulation results. [ABSTRACT FROM AUTHOR]

The Yamal-Nenets Autonomous District, especially the Yamal Peninsula located in the permafrost zone, stores Russia's largest oil and gas resources. However, development in the area is challenging because of its harsh climate and engineering–geological features. Drilling in oil and gas fields in permafrost faces problems that are fraught with serious accident risks: soil heaving leading to the collapse of wellheads and hole walls, deformation and breakage of casing strings, gas seeps or explosive emissions, etc. In this respect, knowledge of the permafrost's structure is indispensable to ensure safe geological exploration and petroleum production in high-latitude regions. The extent and structure of permafrost in West Siberia, especially in its northern part (Yamal and Gydan Peninsulas), remain poorly studied. More insights into the permafrost's structure have been obtained by a precise sTEM survey in the northern Yamal Peninsula. The sTEM soundings were performed in a large oil and gas field where permafrost is subject to natural and anthropogenic impacts, and its degradation, with freezing–thawing fluctuations and frost deformation, poses risks to exploration and development operations, as well as to production infrastructure. The results show that permafrost in the western part of the Yamal geocryological province is continuous laterally but encloses subriver and sublake unfrozen zones (taliks) and lenses of saline liquid material (cryopegs). The total thickness of perennially frozen rocks is 200 m. The rocks below 200 m have negative temperatures but are free from pore ice. Conductive features (<10 Ohm﮲m) traceable to the permafrost base may represent faults that act as pathways for water and gas fluids and, thus, can cause a geohazard in the oil and gas fields (explosion of frost mounds, gas blow during shallow drilling, etc.). [ABSTRACT FROM AUTHOR]

The stability and performance of loess infrastructure in cold regions are often challenged by seasonal freezing–thawing action. The action of the foundation loess is a complex thermo-hydro-mechanical coupling process, and it is crucial to understand this process for the loess infrastructure in cold regions. A series of controlled tests were conducted to observe the changes in temperature, moisture, and frost heave variations within loess samples under freezing–thawing, and the influences of cycle period, freezing–thawing amplitude, and cycle number on the thermo-hydro-mechanical behavior of loess were investigated. The results reveal that freeze–thaw cycles significantly affect the heat transfer, water migration, and deformation of the loess. The temperatures of sample at different heights periodically vary under freezing–thawing. Water is absorbed to the samples, which undergoes a rapid water intake stage, a water drained stage, and a slow water intake stage under freezing–thawing, resulting in moisture redistribution in loess. Loess undergoes frost heave, thaw settlement, and consolidation processes during freezing–thawing, and a slight wetting collapse may occur after several freezing–thawing cycles. Within the same cycle, frost heave is the largest while consolidation deformation is the smallest. Frost heave and consolidation deformation reach their maximum values at the second cycle, whereas thaw settlement reaches its maximum value during the second or third cycle. Each stage deformation increases with an extended cycle period and almost decreases as the freezing–thawing amplitude increases. Freeze–thaw cycles can induce wetting collapse of loess, resulting in negative residual deformation. Furthermore, the thermo-hydro-mechanical coupling process and the deformation mechanism of loess have been elucidated. These insights contribute to a more comprehensive understanding of the failure mechanisms in loess engineering in cold regions. [ABSTRACT FROM AUTHOR]

This research work presents a comprehensive experimental study of frost heave in a fine-grained material to investigate the effects of top freezing (TF) and bottom freezing (BF) mechanisms with ice lens formation. A novel test device was built to investigate artificial ground freezing (AGF)-related temperature and load boundary conditions. This paper includes 62 frost heave experiments and test observations up to 10 days. The long test duration allows a precise examination of ice lens growth during thermal steady state when the frost line remains largely stable and the ice lens grows. This state corresponds to the holding phase of a practical in situ AGF implementation where the cooling is used to maintain the frozen body thickness. The freezing observations show that BF heaving is larger than TF heaving in most cases. This is caused by the more favorable hydraulic conditions caused by gravitational effects and vertical cracking that occurs during ice lens formation due to suction. This facilitates water accumulation at the ice lens. An applied load reduces the differences between BF and TF conditions beyond a certain value which corresponds to an overburden capable of preventing the formation of the longitudinal cracks. [ABSTRACT FROM AUTHOR]

Water drives the decay of road subgrades such as frost heave in cold areas and collapse in saline soil areas, which influences the safety and comfort of vehicle transportation. This paper proposes a novel geotechnical material, namely hydrophobized soil, as a subgrade fill material to mitigate water-induced degradation of subgrade. Hydrophobized soil has a low affinity to water and therefore can prevent the subgrade from water infiltration, enhancing the volume stability of subgrades. To demonstrate its feasibility, the hydrophobicity and its durability were investigated in this study. A one-year outdoor weathering test on hydrophobized soil columns was conducted, with the hydrophobicity measured. The results show that hydrophobized sand has different durabilities and exhibits different degradations depending on the chosen hydrophobizing agent and its concentration. Based on the testing results and capillary rise model, the design of hydrophobic hydraulic barrier in subgrade was discussed at the end. [ABSTRACT FROM AUTHOR]

Frost-heaving resistance of canals can be designated to evaluate the control parameters in cold regions. As proposed in the national standard of SL23-2006 "Design Code for Frost Heave Resistance of Canal System Engineering", the frostheaving deformation of the canal concrete lining structure can be expected to readily monitor and control in practice. However, the specification cannot provide the specific calculation of uneven frost-heaving deformation in the canal concrete lining. This study aims to facilitate the accurate and practical calculation for the frost-heaving deformation of concrete lining structures under uneven frost-heaving deformation conditions. The fluctuation of groundwater levels was considered across different points along the canal cross-section, together with the continuous deformation within the canal foundation soil. A calculation model was developed for the frost-heaving deformation and internal force of trapezoid concrete lining canal in cold regions under differential frost heave conditions, according to the two-parameter foundation beam of frozen soil. Taking the main trunk canal of Jinghui in Gansu Province as an example, the presented model degenerated into the Winkler model under uniform frost heave conditions. Comparative analysis showed that the traditional Winkler model was regarded as a special case within the proposed model. Some measuring points were simultaneously considered for the shady slope, sunny slope, and bottom of the canal. The Root Mean Square Error (RMSE) between the presented model and observed values was determined to be 0.23, with the Mean Relative Error (MRE) of 4.82%. Taking a trapezoidal concrete lining canal in the Tarim Irrigation area of Xinjiang Uygur Autonomous Region as the prototype, the frost-heaving deformation of the concrete lining structure was calculated at the same time. The results show that the better mechanical performance of the concrete lining canal was achieved in the improved model considering the frozen soil-structure interaction and diffusion of shear force in the frozen soil foundation under uneven frost heave conditions, compared with the material mechanics and traditional Winkler model. The calculated values of the improved model were more consistent with the observation, indicating the rationality and applicability of the model. The engineering example was combined to solve the improved model. The first was the conventional analytical, while the second involved the power series. Among them, the various distributions of free frost heave deformation were expanded into the power series using the comparison coefficient. A special solution with a homogeneous solution was then obtained to introduce the boundary conditions. The general solution was derived for the original control differential equation. The MRE between the frost-heaving deformation was calculated by the power series. Among them, the observed value was 4.31% with an RMSE of 0.17, indicating a reasonable calculation. The power series was utilized to represent the natural frost-heaving displacement of canal foundation soil. Therefore, the improved model effectively enhanced the applicability for the various differential frostheaving modes in foundation-frozen soil. The mechanical response of frost heave was found in the trapezoidal concrete lining canal under differential or uniform frost-heaving deformation. Then, some implication was gained to clarify the influence of transverse groundwater replenishment on the mechanical behavior of concrete lining structures under the frost-heaving deformation of foundation soil. In addition, the improved model can be expected to effectively capture the non-uniform and asymmetric distribution of tangential freezing force at the contact interface, due to the non-equilibrium axial force on both ends of the bottom plate that is caused by the difference between shady and sunny slopes. The finding can provide an effective computational model for the frost heave mechanics of trapezoidal canals in cold regions, especially on differential frost heave conditions. [ABSTRACT FROM AUTHOR]

Climate warming accelerates permafrost thawing, causing warming‐driven disasters like ground collapse and retrogressive thaw slump (RTS). These phenomena, involving intricate multiphysics interactions, phase transitions, nonlinear mechanical responses, and fluid‐like deformations, and pose increasing risks to geo‐infrastructures in cold regions. This study develops a thermo‐hydro‐mechanical (THM) coupled single‐point three‐phase material point method (MPM) to simulate the time‐dependent phase transition and large deformation behavior arising from the thawing or freezing of ice/water in porous media. The mathematical framework is established based on the multiphase mixture theory in which the ice phase is treated as a solid constituent playing the role of skeleton together with soil grains. The additional strength due to ice cementation is characterized via an ice saturation‐dependent Mohr–Coulomb model. The coupled formulations are solved using a fractional‐step‐based semi‐implicit integration algorithm, which can offer both satisfactory numerical stability and computational efficiency when dealing with nearly incompressible fluids and extremely low permeability conditions in frozen porous media. Two hydro‐thermal coupling cases, that is, frozen inclusion thaw and Talik closure/opening, are first benchmarked to show the method can correctly simulate both conduction‐ and convection‐dominated thermal regimes in frozen porous systems. The fully THM responses are further validated by simulating a 1D thaw consolidation and a 2D rock freezing example. Good agreements with experimental results are achieved, and the impact of hydro‐thermal variations on the mechanical responses, including thaw settlement and frost heave, are successfully captured. Finally, the predictive capability of the multiphysics MPM framework in simulating thawing‐triggered large deformation and failure is demonstrated by modeling an RTS and the settlement of a strip footing on thawing ground. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Active moisture control of wicking geotextiles is an effective way to prevent roadbed frost heave diseases. The performance of water conducting fibers determines the drainage function of the wicking geotextile. This study proposes a design method of the cross-sectional structure that synergistically consider drainage and mechanical properties in fibers. The circular or elliptical fiber profile and semicircular groove shape are first determined based on the maximization of the fiber cross-sectional specific surface area. Then, numerical simulation orthogonal experiments are conducted using COMSOL Multiphysics software to investigate the water conductivity and uniaxial tension of irregular fibers. The CRITIC weighted indicator of water conductivity to fiber volume ratio, tensile stress peak and fracture elongation is used as the analysis objects. The influence weights of fiber contour morphology, fiber size, groove number and groove area ratio on the weighted indicators are analyzed, and their optimal values are determined. The optimal "M"-shaped fiber is obtained, and the effectiveness of optimization design is verified through scanning electron microscopy and uniaxial tensile test. The "M"-shaped fiber is woven into the wicking geotextile, and geotextiles water conversion corporation test and drainage test of silty clay soil column is carried out. The test find that mass moisture content of the soil sample decreased by 4.73% within 8 days, which is 2.24% more than that of the staple fibers needling geotextile. This proves the effectiveness of "M"-shaped fibers and wicking geotextiles woven into them. [ABSTRACT FROM AUTHOR]

Roads are exposed to various degradation mechanisms during their lifetime. The pavement deterioration caused by the surrounding environment is particularly severe in winter when the humidity and subfreezing temperatures prevail. Frost heave-induced damage is one of the winter-related pavement deterioration. It occurs when the porewater in the soil is exposed to freezing temperatures. The study of frost heave requires conducting a multiphysics analysis, considering the thermal, mechanical, and hydraulic fields. This paper presents the use of a coupled thermo-mechanical approach to simulate frost heave in saturated soils. A function predicting porosity evolution is implemented to couple the thermal and mechanical field analyses. This function indirectly considers the effect of the water seepage inside the soil. Different frost heave scenarios with uniform and non-uniform boundary conditions are considered to demonstrate the capabilities of the method. The results of the simulations indicate that the thermo-mechanical model captures various processes involved in the frost heave phenomenon, such as water fusion, porosity variation, cryogenic suction force generation, and soil expansion. The characteristics and consequences of each process are determined and discussed separately. Furthermore, the results show that non-uniform thermal boundaries and presence of a culvert inside the soil result in uneven ground surface deformations. [ABSTRACT FROM AUTHOR]

The soil beneath buildings constructed in cold regions is affected by frost heave, causing the walls to crack and even the buildings to incline and collapse. Therefore, predicting the frost heave when subjected to overburden pressure is crucial for engineering buildings in cold areas. Utilizing the conservation equation of mass, Darcy's equation, and the assumption that the pore water pressure at the top of a frozen fringe, denoted as uw, during the quasi-steady state can be approximately estimated using the Clapeyron equation, a quasi-steady frost heave rate model considering the overburden pressure was proposed. This study considered the difference in pore water pressure within the frozen fringe, which causes water to move from the unfrozen zone to the ice lens, where it subsequently accumulates and freezes into ice. The pore water pressure at the bottom of the frozen fringe, denoted as uu, can be estimated using the soil water characteristic curve (SWCC). The thickness of the frozen fringe was determined using the freezing temperature, segregation temperature, and temperature gradient. The segregation temperature was determined using the two-point method. Additionally, the model suggested that, when uw = uu, the movement of water stopped, leading to the end of frost heave. To validate the proposed model, three existing frost-heaving experiments were analyzed. The findings demonstrated that the estimated rates of frost heave of the samples closely matched the experimental data. Additionally, external pressure delayed water migration. This study can offer theoretical support for building engineering in cold regions. [ABSTRACT FROM AUTHOR]

The deformation and damage to seasonal permafrost roadbeds, as seasons shift, stems from the intricate interplay of temperature, moisture, and stress fields. Fundamentally, the frost heave and thaw-induced settlement of soil represent a multi-physics coupling phenomenon, where various physical processes interact and influence each other. In this investigation, a comprehensive co-coupling numerical simulation of both the temperature and moisture fields was successfully executed, utilizing the secondary development module within the finite element software, COMSOL Multiphysics 6.0. This simulation inverted the classical freezing–thawing experiment involving a soil column under constant temperature conditions, yielding simulation results that were in excellent agreement with the experimental outcomes, with an error of no more than 10%. Accordingly, the temperature, ice content, and liquid water content distributions within the seasonal permafrost region were derived. These parameters were then incorporated into the stress field analysis to explore the intricate coupling between the moisture and temperature fields with the displacement field. Subsequently, the frost heave and thaw settlement deformations of the roadbed were calculated, accounting for seasonal variations, thereby gaining insights into their dynamic behavior. The research results show that during the process of freezing and thawing, water migrates from the frozen zone towards the unfrozen zone, with the maximum migration amount reaching 20% of the water content, culminating in its accumulation at the interface separating the two. Following multiple freeze–thaw cycles, this study reveals that the maximum extent of freezing within the roadbed reaches 2.5 m, while the road shoulder experiences a maximum freezing depth of 2 m. A continuous trend of heightened frost heave and thaw settlement deformation of the roadbed is observed in response to temperature fluctuations, leading to the uneven deformation of the road surface. Specifically, the maximum frost heave measured was 51 mm, while the maximum thaw settlement amounted to 13 mm. [ABSTRACT FROM AUTHOR]

Masonry buildings in high-intensity seismic and cold regions of China face the dual challenges of frost heaving and seismic hazards. To explore the potential of a sand cushion instead of the frozen soil layer to deal with these problems, a cost-effective sand cushion-based Geotechnical Seismic Isolation System (GSI-SC) was developed in this study, where a sand cushion is introduced between the structural foundation and natural soil, while the space around the foundation is backfilled with sand. Shaking table tests on a one-story masonry structure equipped and non-equipped with the GSI-SC system were undertaken to investigate its effectiveness in seismic isolation, where the input wave adopted the north–south component of the EL Centro wave recorded in 1940, and the peak input acceleration (PIA) was set as 0.1 g, 0.2 g, and 0.4 g. It is found that the GSI-SC system significantly reduced the seismic response of the structure, effectively achieving seismic isolation. For a PIA of 0.4 g, the GSI-SC system reduced the acceleration of the roof panel and the inter-story displacement of the structure by 33% and 39%, respectively. Numerical simulations were performed to evaluate the seismic response of buildings equipped and non-equipped with the GSI-SC system. The simulation results matched well with the experimental results, verifying the effectiveness of the newly developed seismic isolation system. The GSI-SC system can provide the potential to reduce frost heave and earthquake disasters for buildings in high-intensity seismic and cold regions. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms responsible for the origin, evolution, and failure of pingos with explosive gas emissions and the formation of craters in the Arctic permafrost requires comprehensive studies in the context of fluid dynamic processes. Properly choosing modeling methods for the joint interpretation of geophysical results and analytical data on core samples from suitable sites are prerequisites for predicting pending pingo failure hazards. We suggest an optimal theoretically grounded workflow for such studies, in a site where pingo collapse induced gas blowout and crater formation in the Yamal Peninsula. The site was chosen with reference to the classification of periglacial landforms and their relation to the local deformation pattern, according to deciphered satellite images and reconnaissance geophysical surveys. The deciphered satellite images and combined geophysical data from the site reveal a pattern of periglacial landforms matching the structural framework with uplifted stable permafrost blocks (polygons) bounded by eroded fractured zones (lineaments). Greater percentages of landforms associated with permafrost degradation fall within the lineaments. Resistivity anomalies beneath pingo-like mounds presumably trace deeply rooted fluid conduits. This distribution can be explained in terms of fluid dynamics. N–E and W–E faults, and especially their junctions with N–W structures, are potentially the most widely open conduits for gas and water which migrate into shallow sediments in the modern stress field of N–S (or rather NEN) extension and cause a warming effect on permafrost. The results obtained with a new workflow and joint interpretation of remote sensing, geophysical, and analytical data from the site of explosive gas emission in the Yamal Peninsula confirm the advantages of the suggested approach and its applicability for future integrated fluid dynamics research. [ABSTRACT FROM AUTHOR]

Shallow groundwater or narrow-deep lined canals have suffered the vertical frost heave at the top of the canal in cold regions. The lining fracture and whole uplift frost damage are also prone to occur, leading to the low stability of the canal at low temperature. However, the existing engineering models of canal frost heave have focused only on the normal one of the canal slope. This study aims to consider the combined effect of vertical frost heave on the top of the canal and normal frost heave on the slope. A mechanical engineering model was established to consider the canal frost heave. Sensitive soil was selected to simulate the moisture-heat-mechanical coupling numerical models in the canal. The frost heave was then used under different dip angles of the slope, width-to-depth ratios, and groundwater levels. The maximum tensile stress was calculated to locate the different freezing depths and dip angles of the slope during frost-jacking. The specific mechanism of canal lining was then explored to clarify the distribution of vertical and normal frost heave during frost-jacking. The internal force of canal lining plate and frost-jacking strength of canal slope were evaluated to calculate the critical slope length, critical groundwater level, and dangerous location of frost-jacking failure. Finally, the engineering mechanics model was proposed to test the actual case. The experimental data was in agreement with the field observation. The results show that the freezing counterforce was failed to offset the upper tangential frost-jacking force, particularly for the lower lining with the short slope length. The lining was also suffered from the jacking disease as a whole. Otherwise, a frost-jacking force was formed inside the lining. The greater the freezing depth and the dip angles of the slope were, the larger the area of the lining bearing the upward tangential force was, and the greater the frost-jacking tensile stress was. The position of the maximum tensile stress caused by jacking was shifted to the lower part of the canal with the increase of freezing depth and inclination angle of the canal slope. The maximum tensile stress was negatively related to the groundwater level. The critical water level of the lining was the critical groundwater level of the original ground frost heave. At the same time, the frost heave of the original ground was a necessary and insufficient condition for the canal to produce the frost pull. The numerical fitting indicated that the minimum curvature radius of the frost depth line at the top of the canal increased with the increase of frost depth and dip angles of the slope. The depth of frost shared a linear relationship with the minimum curvature radius. The dip angles of the slope exhibited a greater impact on the fitting slope. The maximum error of tensile stress was verified by the numerical model to be 1.5%. The frost-jacking position error was within 16.01%. Therefore, the slope range of the freezing line radius function was 1.047 to 4.040 in the soil conditions of the Ningxia irrigation area. There were the overall uplift pattern of small canal and the cracking failure pattern of large canal linings. The damage mechanism was then clarified to prevent and control the anti-frost heave of canal lining. The finding can also provide a strong reference for engineering design and code revision. [ABSTRACT FROM AUTHOR]

In the design and upkeep of canals in areas of seasonal permafrost, resistance to frost heave is a critical factor for ensuring the stability of water conveyance canals. Mechanical modeling is the key to frost heaving‐resistant design. In this study, the theory of elastic thin plates was used to build a mechanical model of frost heaving damage to rectangular canals. The model's plausibility was confirmed using a prototype canal as an example, and the canal's deformation, internal force, and stress distribution were examined. The findings demonstrate that, compared to beam theory, the internal forces and deformations computed by the model are not evenly distributed along the plate width; the base slab and side walls both saw their greatest deformations in the middle portion and two‐fifths from the canal's top, respectively; at the junction of the two, the bending moments and tensile stresses are maximum and distributions are consistent; transverse moments should be used as control moments in the structural design of canals, and stick feet should be placed at junctions to stop damage. In addition, the maximum normal frost heaving force and optimal thickness that four various canals can withstand were estimated, and the results were biased in favor of safety. The calculation's results can serve as a theoretical guide for antifreeze design concrete rectangular canals in places that experience seasonal freezing. [ABSTRACT FROM AUTHOR]

In this paper, an experiment study was carried out to identify the fundamental behavior of geosynthetic-encased stone column (GESC) reinforced foundation under freeze-thaw cycles. Three loading tests under four freeze-thaw cycles were considered. A 10-m thick reinforced foundation unit consisted of four floating GESCs with 2.5-m underlain clay layer, and the foundations were preconsolidated to three different initial degrees of consolidation (U = 1.0, 0.6 and 0.3, respectively). The results showed that soil near GESCs had a larger frozen depth due to the excellent heat transfer ability of GESCs. An extra uneven subsidence of soil also appeared around GESCs. Voids could be found between foundation soil and the loading plate after thawing, which indicated that only GESCs carried the overburden pressure. The GESCs showed outward bending under lower initial degree of consolidation, while inward bending under higher one. A bulging failure was observed on frozen part of GESCs, especially at the connection of encasement in foundation with lower initial degree of consolidation. In the first freezing process, a rapid decrease in frost heave force was noticed, inferring the fracture of frozen soil. The stress on GESC was found to almost have no change until complete freezing, when the soil was freezing and the stress on soil exceeded that on GESC. Negative pore pressure was observed in the foundation soil, and the absolute value decreased with the increasing overburden pressure. Both the peak positive and negative pore pressures were reduced as the foundation was preconsolidated to a higher degree. The freeze-thaw cycles were also found to generate excess pore pressure in soil during thawing. Moisture migration was also analyzed using Electrical Resistivity Tomography (ERT) method, and the results showed that moisture tended to go upwards and outside the reinforced unit from thawing to freezing, while downwards and inside the unit from freezing to thawing. • This paper investigated the behavior of GESC-reinforced foundation under freeze-thaw cycles. • Significant differential settlement was observed in the foundation. • The deformation patterns of GESCs were influenced by the initial degree of consolidation. • Only GESCs carried overburden pressure by the rigid base during thawing, and SCR reduced to less than 0.5 during freezing. • Moisture migration was studied using ERT, and negative pore pressure was observed. [ABSTRACT FROM AUTHOR]

In cold regions, rock fractures can expand under the force of frost heave pressure, potentially triggering severe geological catastrophes such as collapses and landslides on rock slopes. Nevertheless, a comprehensive study of the evolution patterns and causes of frost heave pressure within rock fractures is currently lacking. To address this gap, this paper focuses on single-cracked sandstone and identifies four distinct types of frost heave pressure curves by conducting monitoring tests under various conditions. Each type of curve was thoroughly analyzed to understand its evolution and the underlying causes. It was found that the rupture and drop type curve can be segmented into five stages: incubation, eruption, drop, equilibrium, and dissipation. The drop stage is predominantly attributed to the fracturing of the crack influenced by frost heave pressure. Compared with the rupture and drop type curve, the stable type curve, where the crack does not expand during the freeze–thaw cycle, lacks a drop stage. Furthermore, samples displaying a stable descent type curve possess a higher freezing temperature, causing a noticeable delay in the emergence of their frost heave pressure. This curve, when compared with the stable type, shows a faster reduction in frost heave pressure during the equilibrium stage. For the secondary frost heave type curve, secondary frost heave emerges within the rock fracture at the onset of thawing, with the rupture of ice proving critical to this phenomenon. The frost heave pressure distributed along the crack surfaces of the four types of curves displays a lack of uniformity. This unevenness is observed to correlate with the inconsistent growth of ice according to its self-purification principle. Finally, based on the experimental results, a novel criterion for frost heave pressure and rock fracture cracking is proposed. Highlights: Four distinct frost heave pressure curves are obtained, and the underlying causes of each are examined. The uneven growth of ice causes non-uniform frost heave pressure distribution within the fracture. Ice rupture is pivotal to the formation of secondary frost heave. A novel criterion for frost heave pressure and rock fracture cracking is proposed. [ABSTRACT FROM AUTHOR]

Water freezing in rock fractures causes volumetric expansion and fracture development through frost heaving. This study introduces a novel analytical model to investigate how uneven freezing force and surrounding rock pressure influence fracture initiation, based on mass conservation, elasticity, and water-ice phase transition principles. A model for rock fracture initiation considering freezing temperature, uneven freezing expansion, in-situ stress, and lateral pressure was proposed based on fracture mechanics. Equations for stress intensity factors were developed and validated using the phase field method. The effects of rock elastic modulus anisotropy and critical fracture energy density on fracture initiation were also discussed. The results show that the values of KI and KII exhibit an upward trend as the freezing temperature, uneven expansion, in-situ stress, and lateral pressure increase. The uneven freezing expansion has the most significant influence on KI and KII values among these parameters. As the uneven freezing expansion coefficient increases to 0.5, the fracture initiation mode shifts from tensile fracture to shear fracture. As the lateral pressure coefficient increases to 1, the fracture initiation mode shifts from tensile fracture to shear fracture. Rock elastic modulus anisotropy causes fractures to propagate in a clockwise direction, forming a 'butterfly' pattern. Critical fracture energy density an isotropy causes counterclockwise deviation in propagation direction, resulting in branching paths and an 'H'-shaped pattern. [ABSTRACT FROM AUTHOR]

The frost deterioration and deformation of porous rock are commonly investigated under uniform freeze-thaw (FT) conditions. However, the unidirectional FT condition, which is also prevalent in engineering practice, has received limited attention. Therefore, a comparative study on frost deformation and microstructure evolution of porous rock under both uniform and unidirectional FT conditions was performed. Firstly, frost deformation experiments of rock were conducted under cyclic uniform and unidirectional FT action, respectively. Results illustrate that frost deformation of saturated rock exhibits isotropic characteristics under uniform FT cycles, while it shows anisotropic characteristics under unidirectional FT condition with both the frost heaving strain and residual strain along FT direction much higher than those perpendicular to FT direction. Moreover, the peak value and residual value of cumulative frost strain vary as logarithmic functions with cycle number under both uniform and unidirectional FT conditions. Subsequently, the microstructure evolution of rock suffered cyclic uniform and unidirectional FT action were measured. Under uniform FT cycles, newly generated pores uniformly distribute in rock and pore structure of rock remains isotropic in micro scale, and thus the frost deformation shows isotropic characteristics in macro scale. Under unidirectional FT cycles, micro-cracks or pore belts generate with their orientation nearly perpendicular to the FT direction, and rock structure gradually becomes anisotropic in micro scale, resulting in the anisotropic characteristics of frost deformation in macro scale. [ABSTRACT FROM AUTHOR]

An extended ordinary state-based peridynamic model was developed to investigate the crack propagation of surrounding rock due to tunnel excavation. The frost heave effect on the crack surface was described by an equivalent pressure density. Two numerical examples were conducted to verify the effectiveness and robustness of the proposed model. Moreover, the influence of frost heave pressure, buried depth and rock elastic modulus on damage characteristics of the surrounding rock was investigated. The results demonstrate that massive microcrack damage will be formed at the invert when the tunnel is excavated in a deeply buried rock mass or soft rock stratum. A peridynamic model of rock mass under excavation and frost heave was constructed. Damage characteristics of surrounding rock could be simulated efficiently. Frost heave load was exerted on the crack surface by an equivalent pressure density. The effects of frost heave load, buried depth and rock elastic modulus were studied. [ABSTRACT FROM AUTHOR]

In response to the frequent accidents caused by freezing-induced deformation of anchor rod support structures in seasonal frozen soil areas, this study proposes a simplified calculation method. Based on the deformation coordination relationship of the slope frost heave soil under the constraint of the frame beam, the initial frost heave force distributed in the beam was obtained. Using the Pasternak double-parameter foundation model, a differential equation for the freezing-induced deformation of the frame columns, accounting for the shear effect of the freezing layer and the anchoring action of the anchor rods, is established. To validate the proposed method, a finite element model is developed using the ABAQUS thermal coupling module. The results demonstrate that the results obtained from the simplified method and numerical simulation solution in this article are basically similar, and about 11% higher than the numerical simulation solution. However, compared with the Winkler foundation model, it can more accurately reflect the distribution law of frost heave displacement of frame columns. And the Winkler foundation model overestimates the frost heave deformation and internal forces by about 21%, indicating that considering the shear effect of the frozen layer can more accurately reflect the actual stress state of the frame columns. In addition, according to the sensitivity analysis of the influencing parameters, it can be concluded that the changes in the spacing between anchor bolts and the frost heave rate of the soil have a more significant impact on the deformation of the frame columns. Consequently, it is crucial to assess the freezing grade of the slope and determine anchor rod positions thoughtfully during the design phase. This research sheds light on the fundamental characteristics of the frame beam anchor structure under the influence of soil frost heave, enhancing calculation precision, and offering valuable scientific insights for practical engineering design. [ABSTRACT FROM AUTHOR]

The 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. [ABSTRACT FROM AUTHOR]

The temperature dynamics of conjugated soils of a paleocryogenic soil complex on chalk deposits in the Orenburg oblast is studied. Temperature measurements are combined with the study of cryogenic characteristics. The freezing point of soil moisture has been measured in laboratory. The temperature field within the soil complex is most heterogeneous. In the fall–winter season, the soil of microhighs is colder than the soils of microlows and microslopes; however, the microslope warms up faster than the microelevation and microlow in the spring–summer season. The differences between the temperature of soils in the frozen layer of microhighs and microlows reach –4.5°C at the beginning of freezing (December 15, 2019 at a depth of 15 cm), –4.0°C at the end of winter (February 10–11, 2020 at a depth of 5 cm), and –6.5°C during thawing (March 21–23, 2020 at a depth of 5 cm). The differences in the temperature regime along the microrelief are accompanied by the differences in the moisture distribution along the profile and determine the manifestation of cryogenic processes. The soils of microhighs freeze deeper and lens-type cryostructure forms in the entire frozen layer; this is accompanied by frost heaving, cryogenic sorting of coarse fragments, and formation of a crust on the soil surface ensuring preservation of the microtopography and soil cover pattern of chalk polygons. Cryogenic processes determine the formation of a platy soil structure in microhighs. Freezing in microlows is blocked in the middle part of the profile because of relatively high soil temperatures and low soil freezing points. The cryogenic characteristics and processes described in microhighs are unobservable in microlows. [ABSTRACT FROM AUTHOR]

In practice, little attention has been paid directly to freeze-thaw (FT) cycles during the design and analysis of geogrid-reinforced soil (GRS) walls due to a lack of relevant literature. This study investigates the pavement vertical deformation (s), panel lateral deformation (d), lateral earth pressure (σh), and geogrid strain (ε) of a field GRS wall using an ABAQUS-based numerical model considering variations of the recorded five-year ambient temperature (TR). Numerical results show that the s distribution follows a convex shape instead of the initial concave shape after FT cycles and can be divided into high, transition, and stable deformation zones. FT action alters both location and amplitude of the maximum d within the first two cycles, making the d distribution evolve from a J-shaped curve into an S-shaped one. During freezing, the developments of s and d are coordinated and can be described using a unified model; σh is larger than the Rankine active earth pressure; ε state depends on the interplay of two factors resulting from d and frost heave force. Furthermore, the hysteresis of s, d, σh, and ε with TR was discussed and several beneficial suggestions were proposed for GRS walls to avoid such FT destruction. [ABSTRACT FROM AUTHOR]

Copyright of Mountain Research (10082786) is the property of Mountain Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ultralow-temperature fluids (such as liquid nitrogen, liquid CO2) are novel waterless fracturing technologies designed for dry, water-sensitive reservoirs. Due to their ultralow temperatures, high compression ratios, strong frost heaving forces, and low viscosities, they offer a solution for enhancing the fracturing and permeability of low-permeability reservoirs. In this study, we focus on the combined effects of high-pressure fluid rock breaking, low-temperature freeze-thaw fracturing, and liquid-gas phase transformation expansion on coal-rock in low-permeability reservoirs during liquid nitrogen fracturing (LNF). We systematically analyze the factors that limit the LNF effectiveness, and we discuss the pore fracture process induced by low-temperature fracturing in coal-rock and its impact on the permeability. Based on this analysis, we propose a model and flow for fracturing low-permeability reservoirs with low-temperature fluids. The analysis suggests that the Leidenfrost effect and phase change after ultralow-temperature fluids enter the coal support the theoretical feasibility of high-pressure fluid rock breaking. The thermal impact and temperature exchange rate between the fluid and coal determine the temperature difference gradient, which directly affects the mismatch deformation and fracture development scale of different coal-rock structures. The low-temperature phase change coupling fracturing of ultralow-temperature fluids is the key to the formation of reservoir fracture networks. The coal-rock components, natural fissures, temperature difference gradients, and number of cycles are the key factors in low-temperature fracturing. In contrast to those in conventional hydraulic fracturing, the propagation and interaction of fractures under low-temperature conditions involve multifield coupling and synergistic temperature, fluid flow, fracture development, and stress distribution processes. The key factors determining the feasibility of the large-scale application of ultralow-temperature fluid fracturing in the future are the reconstruction of fracture networks and the enhancement of the permeability response in low-permeability reservoirs. Based on these considerations, we propose a model and process for LNF in low-permeability reservoirs. The research findings presented herein provide theoretical insights and practical guidance for understanding waterless fracturing mechanisms in deep reservoirs. [ABSTRACT FROM AUTHOR]

Abstract The methane in the coal seams of abandoned mines is a valuable natural gas resource. However, the ultra-low permeability of coal seams restricts the extraction of coalbed methane. The liquid nitrogen fracturing technology is a novel approach suitable for enhancing the permeability of coal seams in abandoned mines. The ultra-low temperature could potentially facilitate the growth and propagation of pores and fractures in coal seams. In this study, we observed inconsistent alterations in coal properties measured by multiple instruments at different scales, whether in dry or wet coal specimens. This suggests that the mechanisms influencing the pore structure due to LN2 treatment differ across various scales in dry and wet coal specimens. For dry specimens, heterogeneous thermal deformation and freezing shrinkage exhibited opposing effects during LN2 treatment. Thermal stress-induced micro-fractures might counteract the freezing contraction of micropores in coal matrices, preventing a significant decrease in coal macropores and fractures. In wet specimens, the effects of LN2 treatment on wet coal specimens were predominantly controlled by frost heaving. However, due to low water saturation, LN2 treatment had negligible effects on coal micropores, even in the presence of local frost heaving. In field applications, water migration from smaller to larger pores could further diminish the impact of LN2 treatment on micropores.

The advancement of massive construction in urban subway projects contributes to the increased use of the artificial ground freezing (AGF) method in the construction of cross passages due to its reliability and environmental friendliness. However, the uplift or subsidence of the ground surface induced by the frost heave and thawing settlement of the soil can be a problem for existing buildings, and the current design method places way too much emphasis on the strength requirement of the freezing wall. In this study, FLAC3D was employed to develop a series of state-of-the-art numerical models of the construction of a typical subway cross passage by the AGF method, utilizing freezing walls with different thicknesses. The results of this study can be used to examine the ground deformation arising from the AGF method and the influence of the thickness of the freezing wall on the AGF method. [ABSTRACT FROM AUTHOR]

The phenomena of freezing damage in the cold regional tunnels have happened frequently. Therefore, in order to precisely calculate frost heaving force ( σ 1 ), based on the displacement method, a new analytical solution was proposed. The analytical solution presented in this paper was verified by the results of the model test and field measurement of σ 1 , the imperfect contact effect between frozen and unfrozen zones of surrounding rock was considered and the influence of the interaction between any two factors on frost heaving force was studied by means of orthogonal experiment and analysis of variance. The results show that: (1) the inner radius of lining ( r a ), excavation radius ( r 1 ) and freezing radius ( r f ) are highly significant for σ 1 and the interaction between the inner and outer radiuses of lining (i.e., changes of the size in inner and outer radius of lining) is also highly significant for frost heaving force ( σ 1 ); (2) the analytical solution presented in this paper can avoid the frost heaving force ( σ 1 ) with tensional property under the condition of the circular tunnel under hydrostatic pressure; and (3) sensitivity function shows that the larger Young's modulus of lining ( E I ), inner radius of lining ( r a ), freezing radius ( r f ), linear frost heaving rate ( β 0 ) and Young's modulus of frozen surrounding rock ( E II ) are, the more sensitive the factors E I , r a , r f , β 0 and E II are to σ 1 . It is expected that the results of this paper can give some novel insights for the anti-freezing design of tunnels. Highlights: Inner radius of lining is the more sensitive to frost heaving force. The interaction between the inner and outer radiuses of lining is highly significant. The ra, r1 and rf are highly significant for frost heaving force. The analytical solution can avoid frost heaving force ( σ 1 ) with tensional property. [ABSTRACT FROM AUTHOR]

Freeze–thaw action leads to soil volume changes, which significantly influence the stability of earthen structures. The volumetric strain of soil is sensitive to the changes of temperature. Recent research has identified the potential application of microencapsulated phase change materials (PCM) as a temperature regulator to reduce thermal-induced volumetric strain in soil. However, the effect of PCM inclusion on the soil volumetric behaviour has not been clarified yet. In this study, soil samples to which 2% PCM was added were tested using a double-cell triaxial apparatus to investigate the influence of the PCM on the soil volumetric strain. To estimate and predict the volumetric behaviour of soil with PCM mixture subjected to freeze–thaw action, a numerical model based on the thermo-hydro-mechanical (THM) framework and large strain consolidation theory is adopted. The results of laboratory tests reveal that soil containing PCM exhibits lower frost heave during the freeze–thaw action. Compared with unamended soil, volumetric strain is reduced from 4.2 to 3.4% by adding PCM when soil temperature stabilised at − 6 °C. Meanwhile, the volumetric strain after thawing induced by thaw consolidation was 2.4% for unamended soil and 1.5% for soil with PCM. The computed result from THM model reveals that the thermoregulation effect of PCM can effectively decrease the rate of soil temperature change and therefore, both frost heave and thawing contraction is reduced. The rates of temperature change for soil with PCM were 24% and 10% lower than those of unamended soil during thawing and freezing, respectively. The decrease in the rate of soil temperature change is caused by the release of PCM latent heat and reduction in thermal conductivity of the soil mixture. [ABSTRACT FROM AUTHOR]

To study the freezing characteristics and the effects of the horizontal freezing method of shield tunneling on the surrounding environment at a complex site, a systematic study with field measurements of the temperature and frost heave displacement fields of horizontal cup-type freezing was conducted on the south end shield tunneling of the Shuanghehu station of Zhengzhou metro line 17. The conclusions of the current research are: (1) the soil has a greater effect on freezing than the average moisture content of the soil layer. On the premise of a similar average moisture content, silt continues to cool at a faster rate after reaching the freezing point; (2) within the outer circle of the freezing tube, the rate of expansion of the freezing curtain decreases with distance from the freezing tube. The rates of development measured by the outer holes of the left and right line tests are 2.40 and 6.03 times those of the inner holes, respectively; (3) frost heave displacements are larger near the frozen area. The maximum frost heave in the frozen area is about 1.60–1.83 times that in the unfrozen area; (4) the temperature measurement holes in the left line fell below 0 °C 6 days later than the right line. The flow of groundwater has an adverse effect on the effect of freezing consolidation. [ABSTRACT FROM AUTHOR]

Engineering usually considers coarse-grained soils as non-frost swelling soils, but serious frost swelling still occurs in coarse-grained canal bases, which is directly related to the recharge conditions and the fine particle content in the soil. Little attention is currently paid to the effect of different fine particle contents on coarse-grained soil frost swelling, especially after the fine particle admixture content exceeds 16%. This paper considers the characteristics of coarse-grained soils in water conservancy projects with fines content between 0% and 50%. The coarse-grained soils with 5%, 15%, 25%, 35%, and 45% fines content were designed for freezing and swelling tests. The evolution of temperature and moisture fields and the amount of freezing and swelling of coarse-grained soils during the freezing process were studied by using servo-type freezing and swelling and thawing tester. The experimental results show that the cooling process of soil samples can be divided into a rapid cooling stage, a slow cooling stage, and a freezing stabilization stage. The cooling rate and the frost heave amount with increasing fines content showed a trend of first increasing and then decreasing. [ABSTRACT FROM AUTHOR]

Frost heave susceptibility is a key index for designing the subgrade fillings of high-speed railways in cold regions. The existing methods for assessing frost heave susceptibility are mainly empirical or semi-empirical, and most of them are defined based on the fine content of soils. This study attempts to propose a new criterion based on the analytical solution of frost heave in the soil. A number of experiments are used to validate the proposed analytical model, which shows that the computed value of frost heave matches well with the measured data. The proposed model indicates that frost heave is a proportional function of the square root of time. Thus, the slope R named frost heave classification index of the proportional function is defined as a new index for frost heave susceptibility classification. A value of R less than 0.21 corresponds to a non-frost heave susceptibility condition, a value greater than 1.18 corresponds to a high frost heave susceptibility condition, and a value in the range of 0.21 and 1.18 means a frost heave susceptibility condition. R is directly related to the boundary temperatures and soil–water and soil-freezing characteristics. The parameter study shows that reducing the values of SWCC fitting parameter α and cold end temperature Tc or increasing the values of permeability of frozen soil kf, the saturated volumetric water content θs, the unfrozen water content at the frost front θu and the residual volumetric water content θr increases the possibility of frost heave. Compared with the existing method, the new index has a clear theoretical basis, and the parameters are easily obtained. It may be a rational method for assessing frost heave susceptibility. [ABSTRACT FROM AUTHOR]

Featured Application: Optimizing infrastructure design, agricultural planning, and environmental management in Romania through precise assessment of frost depth and frost heave. The investigation of extreme weather and climate events has gained momentum in the last few decades, spurred in part by political involvement. However, not enough attention has been paid to the historical recorded data of climate monitoring. An accurate estimate of maximum soil frost depth is an important factor in determining construction costs and structures' foundations, and designers also need reliable information about local meteorological parameters. In this study, the calculations of the parameters for the city of Arad are presented as an example. An updated Romanian frost depth map and a new Romanian freeze–thaw cycle (FTC) map are needed since recent climate studies have documented an increase in global and regional surface temperatures, with the greatest shift in warming occurring over the last three decades. This trend is particularly pronounced when comparing the 1990–2020 period with earlier periods, which could be indicative of broader climate change trends. It is important to note that these conclusions are based solely on the provided statistical parameters and do not take into account other potential factors influencing temperature trends in the region. The results from this investigation could be used to achieve a reduction in frost disasters and the formulation of policies and measures for the adaptation of geotechnical/structural design for Romanian territory. They may also support the development of maps that help to visualize and understand the evolving climate patterns in the region, including changes in frost depth and the frequency of freeze–thaw cycles, which are important for various sectors such as agriculture, construction, and infrastructural planning. Given the documented increase in global and regional surface temperatures, updating such maps will also provide valuable information for policymakers, researchers, and stakeholders on how to adapt to ongoing climate change and its impacts on the Romanian region. [ABSTRACT FROM AUTHOR]

In the context of the accelerating impacts of climate change on permafrost landscapes, we use Unpiloted Aerial Vehicle (UAV) LiDAR technology to investigate seasonal terrain changes in palsas – mounds of frozen peat – since other remote sensing methods have struggled to capture the full dynamics of these landforms. We investigated two palsas (4–5 m in height) in Sweden's largest palsa mire complex, where we performed five field campaigns between September 2022 and September 2023 to track intra-annual frost heave and thaw subsidence. Our approach allowed us to create digital terrain models (DTMs) from high density point clouds (>1,000 points/m²) and analyze elevation changes over time. We found that both palsas heaved on average 0.15 m (and up to 0.30 m) from September to April and subsided back to their height from the previous year, or slightly below, over the course of the following summer. At one of the palsas, we observed notable lateral degradation over the study period in a 300 m2 area, with 0.5–2.0 m height loss, likely initiated during the preceding warm and wet summer months. Part of this degradation occurred between September 2022 and April 2023, suggesting that the degradation of these palsas is not limited to the summer months. Our study shows the substantial value of using UAV LiDAR for understanding how permafrost areas are changing. It helps in tracking the ongoing effects of climate change and highlights palsa dynamics that would not be captured by annual measurements alone. [ABSTRACT FROM AUTHOR]

The degree of water saturation significantly affects the rate of rock deterioration caused by freeze–thaw weathering, which may trigger serious geological engineering hazards. This study aimed to explore the impacts of water saturation on freeze–thaw-induced deterioration of sandstone, and to improve our understanding of this damage mechanism. Sandstone specimens with varying degrees of moisture saturation were subjected to freeze–thaw tests, computed tomography scanning, and uniaxial compressive tests. The distribution of the areal porosity along the computed tomography slices, evolution of the pore volume, and changes in the pore network model parameters of the sandstone samples were visually and quantitatively characterised to assess the damage evolution. The results show that the parameters of the pore-fracture structure reflect the influence of saturation and cyclic freeze–thaw actions on rock deterioration. As the moisture saturation increased, the sandstone transformed from being dominated by pores with a radius ranging from 0 to 100 μm to being dominated by pores of 200–300 μm. The increase in the equivalent radii of pores caused the rock to be more susceptible to deformation and failure, whereas an increase in the number of throats represents a disruption of the cementation between the rock grains, making to rock more susceptible to freeze–thaw actions. Furthermore, the damage mechanisms of sandstone can be interpreted by volumetric expansion and hydrostatic pressure theory in a rapid freeze–thaw environment. The results of this study provide a comprehensive insight into the influence of water saturation on freeze–thaw-induced damage evolution of rocks in cold regions. Highlights: With the increase of water saturation, the radius of the dominant pores in the rock gradually expands. With the increase of saturation, the number of throats between connected pores increases, which disrupts the cementation between the rock grains, thereby making the rock more susceptible to freeze–thaw cycles. The frost heave force accelerates the coalescence of pores and prolong the pore closure stage in the stress–strain curves of the tested rocks. Volumetric expansion and hydrostatic pressure are jointly responsible for the damage caused by freeze–thaw cycles. [ABSTRACT FROM AUTHOR]

Frost heave, which is related to the variation in the hydrothermal interaction properties of soil, is the main factor causing the inhomogeneous deformation of structures in cold regions. The relevant requirement for describing frost heave is to obtain the soil freezing characteristic curve, which contains fundamental information for describing the hydrothermal behavior of frozen soil. In this study, the unknown parameters of the van Genuchten equation and the hydraulic conductivity of partially frozen soil were indirectly derived using the pulsed nuclear magnetic resonance (P-NMR) technique based on the soil freezing characteristic curve and Clapeyron equation. Based on continuum mechanics, a hydrothermal coupling model combined with the unknown parameters obtained from a P-NMR experiment was applied to quantify the hydrothermal performance of the frozen soil. The mathematical module of COMSOL Multiphysics was employed to solve the coupling equation numerically. To validate the proposed coupling model, water transfer experiments were conducted on silty clay in closed and open systems under freezing conditions in our laboratory. The measured experimental data were consistent with the prediction results, confirming the applicability of the coupling model of the frozen soil in predicting the hydraulic parameters based on the new soil freezing characteristic curve. [ABSTRACT FROM AUTHOR]

Frost heaving in soils is a primary cause of engineering failures in cold regions. Although extensive experimental and numerical research has focused on the deformation caused by frost heaving, there is a notable lack of numerical investigations into the critical underlying factor: pore water pressure. This study aimed to experimentally determine changes in soil water content over time at various depths during unidirectional freezing and to model this process using a coupled hydrothermal approach. The agreement between experimental water content outcomes and numerical predictions validates the numerical method's applicability. Furthermore, by applying the Gibbs free energy equation, we derived a novel equation for calculating the pore water pressure in saturated frozen soil. Utilizing this equation, we developed a numerical model to simulate pore water pressure and water movement in frozen soil, accounting for scenarios with and without ice lens formation and quantifying unfrozen water migration from unfrozen to frozen zones over time. Our findings reveal that pore water pressure decreases as freezing depth increases, reaching near zero at the freezing front. Notably, the presence of an ice lens significantly amplifies pore water pressure—approximately tenfold—compared to scenarios without an ice lens, aligning with existing experimental data. The model also indicates that the cold-end temperature sets the maximum pore water pressure value in freezing soil, with superior performance to Konrad's model at lower temperatures in the absence of ice lenses. Additionally, as freezing progresses, the rate of water flow from the unfrozen region to the freezing fringe exhibits a fluctuating decline. This study successfully establishes a numerical model for pore water pressure and water flow in frozen soil, confirms its validity through experimental comparison, and introduces an improved formula for pore water pressure calculation, offering a more accurate reflection of the real-world phenomena than previous formulations. [ABSTRACT FROM AUTHOR]

Soil frost deformation significantly influences engineering projects in cold regions. The anisotropic behavior of soil, involving surface and internal deformation in three dimensions (3D), introduces inaccuracies in evaluating freeze–thaw geological hazards. To explore the relationship between internal strain and surface displacement of soil in a 3D space during the freezing-thawing process, a platform for monitoring coupled surface-internal deformation in 3D were developed using binocular recognition technology and a novel 3D strain rosette. Subsequently, a freezing-thawing model test of soil in Dalian Offshore Airport filling is conducted using the platform. The results show that, the internal strain of soil is closely associated with the boundary conditions of the test unit. During freezing test, the vertical strain exhibits a more significant increase in comparison to the horizontal strain. Surface displacements in soil primarily occur during the initial freezing and thawing stages. The variation of surface horizontal displacement in each direction is minimal throughout the freezing-thawing process. A surface freezing boundary leads to an increment in internal strain, while the deep frozen stress relief causes the soil surface expand during thawing. This study provides a suggestion for the control of the cold source in cold region engineering.

Water migration behavior is the main cause of engineering disasters in cold regions, making it essential to understand its mechanisms and the resulting mechanical characteristics for engineering protection. This study examined the water migration process during soil freezing through both experimental and numerical simulations, focusing on the key mechanical outcomes such as deformation and pore water pressure. Initially, a series of controlled unidirectional freezing experiments were performed on artificial kaolin soil under various freezing conditions to observe the water migration process. Subsequently, a numerical model of water migration was formulated by integrating the partial differential equations of heat and mass transfer. The model’s boundary conditions and relevant parameters were derived from both the experimental processes and existing literature. The findings indicate that at lower clay water content, the experimental results align closely with those of the model. Conversely, at higher water content, the modeled results of frost heaving were less pronounced than the experimental outcomes, and the freezing front advanced more slowly. This discrepancy is attributed to the inability of unfrozen water to penetrate once ice lenses form, causing migrating water to accumulate and freeze at the warmest ice lens front. This results in a higher ice content in the freezing zone than predicted by the model, leading to more significant freezing expansion. Additionally, the experimental observations of pore water pressure under freeze–thaw conditions corresponded well with the trends and peaks projected by the simulation results.

Frost heave action is a major issue in permafrost regions, leading to various geotechnical engineering problems. In this study, we assess the mechanical behavior of a concrete retaining wall subjected to frost heave under different ground conditions. The assessment utilizes ABAQUS integrated with several user subroutines. The numerical simulation model employs a thermo-mechanical coupled analysis with a porosity rate function, which enables to simulate time-dependent variations in porosity and frost heave of the backfill soil. After verification of the predictive reliability of the simulation model, the frost heave action in the soil and mechanical response of the retaining wall were evaluated regarding the initial groundwater level and presence of a drainage material on the backside of the retaining wall. According to the simulation results, as the initial groundwater level decreased in the backfill soil, the area susceptible to frost heave decreased. However, the von Mises stresses applied to the retaining wall increased. Under the same ground conditions, when the drainage material was installed on the backside of the retaining wall, the frost heave pressure acting on the wall significantly decreased, and less deformation and distortion of the retaining wall occurred. [ABSTRACT FROM AUTHOR]

In this paper, two centrifuge tests were conducted on geosynthetic-encased stone column (GESC) supported embankment to investigate the behavior under freeze-thaw cycles considering the effects of initial degree of consolidation and number of freeze-thaw cycles. The embankments with a height of 4.5 m supported by GESC-reinforced foundation with a thickness of 9 m in prototype were first consolidated to initial degrees of consolidation of 30% and 60%, respectively, and then subjected to three freeze-thaw cycles. The results showed that the foundation soil under the embankment toe experienced a higher degree of freezing than the soil outside the embankment with non-uniform frozen depths observed at different positions in soil under the embankment, and that multiple freeze-thaw cycles contributed to extra settlement in the foundation. Both the frost heave and thaw settlement appeared on GESCs prior to soil. During freezing, the stress on GESC increased first, while decreased rapidly when soil began freezing. The stress concentration ratio (SCR) reached nearly 1.0 before complete freezing. After the complete thawing of GESCs, the stress on GESC increased significantly. As the number of freeze-thaw cycles grew, the variation in settlement, stress and pore pressure was reduced. The final settlement on soil was greater in the foundation with lower initial degree of consolidation, as well as the SCR. The GESCs had larger deformation and showed outward bending under lower initial degree of consolidation, but inward bending appeared on GESCs under higher one. • This paper investigated the behavior of GESC-supported embankment under freeze-thaw cycles. • The frozen depths were found to vary in different positions, and frost heave and thaw settlement were observed. • The deformation modes of GESCs were different considering the initial consolidation degrees. • Stress on soil and GESCs experienced increase and decrease according to different timing nodes during freeze-thaw cycles. • Dissipation of excess pore pressure depended on the periods of freezing or thawing. [ABSTRACT FROM AUTHOR]

The dynamic mechanical behavior of frozen rock with a flaw is essential for plateau alpine region mining. However, the freezing temperature's strengthening and damage mechanism on dynamic strength is still unclear. Drop weight impact tests (single factor) and orthogonal tests (3 factors and 5 levels) were used to examine the influence of flaw dip angle (β), impact height (H), and freezing temperature (T) on the dynamic response of frozen sandstone in plateau alpine region. Different factors' effect on peak strain and failure mode was compared, as well as a significant analysis of three factors' influence on peak strain. The results reveal that with the increase of β, the ultimate strain (εu) of sandstone shows a 'M' type variation, while the linear increase of εu occurs with the increase of H and the decrease of T. At the same time, β and T have a substantial effect on εu, and T has a significant influence on the occurrence time of εu. In addition, tensile failure is the failure mode of sandstone with tensile cracks mainly parallel to the direction of impact. Moreover, a two-dimensional particle flow code was used to supply the stress–strain curve, cracking process, and energy absorption characteristics. The obvious rebound phenomenon can be observed, and the peak stress increases with the increase of H and decreases as β and T increase. Furthermore, the energy usage rate has a linear relationship with β and T, but it decreases first and then increases as impact energy increases. At the end, the effect of the strengthening mechanism of T on single-flaw sandstone dynamic strength and the damage evolution was discussed. The effect of pore ice is primarily responsible for the strength enhancement of frozen sandstone, but the frost heave damage at a certain T (− 20 °C) will inhibit the strength growth. The damage constitutive model based on logistic function can accurately describe the stress–strain properties of single-flaw frozen sandstone before εu. Highlights: The dynamic mechanical responses of single flaw frozen sandstone were studied by drop weight impact tests and numerical simulation. The influence of flaw dip angle, impact height and freezing temperature on peak strain, stress, and energy consumption were revealed. The strengthening mechanism of freezing temperature on dynamic strength was discussed. The frost heave damage formed at a certain freezing temperature (– 20 °C) will inhibit the growth of strength. [ABSTRACT FROM AUTHOR]