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Granite, as an important natural building material, has a significant impact on the stability of engineering structures due to freeze-thaw (F-T) damage. This study aims to reveal the mechanical nature and damage mechanism of F-T damage in granite. The energy evolution law and cracking failure characteristics were investigated based on the unconfined uniaxial compression test, acoustic emission (AE) technique and multiple fractal theory. The early warning methods of granite fracture failure instability were proposed, utilizing the extracted acoustic emission Mel-frequency cepstral coefficients (MFCC). Additionally, the frost damage to pore walls was analyzed based on the thermodynamic principles and the theory of elastic mechanics. The results indicate that the average damage of granite specimen after 200 F-T cycles is 37.76 % and the F-T damage rate is reduced to 0.19 %. Notably, the frozen-thawed granite tends to a more homogeneous fracture mode, and a sudden decrease in the 2nd order coefficient of MFCC prior to rock fracturing could serve as an early warning for instability. The established computational modeling of pore wall mechanics demonstrated that temperature and porosity exert a significant influence on frost damage. This study comprehensively resolved the failure characteristics of frozen-thawed granite, laying a significant theoretical and experimental foundation for understanding the F-T damage mechanism in rock engineering. • Failure process of frozen-thawed granite was analyzed from the energy evolution perspective. • The cracking characteristics of frozen-thawed granite were resolved via multiple fractal theory. • The theoretical calculation model of frost heave stress was established. [ABSTRACT FROM AUTHOR]

• Thermokarst landslides mainly occurred before 2016 and expanded since then. • Thermokarst landslides exhibited slow creep besides seasonal deformation. • The slope effect showed serious thermokarst landslides on shady slopes. Permafrost degradation under warming climate causes a variety of topographic separation and collapses on hillslopes, collectively known as thermokarst landslides, which seriously affects the stability of the permafrost environment. However, quantitative understanding of the formation and evolution of thermokarst landslides under warming conditions is still limited, thus easily ignoring their realistic vulnerability. Here, we combined the visual interpretation of high-resolution optical satellite images, interferometric synthetic aperture radar (InSAR) measurement, and wavelet analysis to demonstrate the spatiotemporal distribution and the creep characteristics of thermokarst landslides. A total of 385 thermokarst landslides were cataloged on central Tibetan Plateau from 2010 to 2020, and most failures occurred before 2016 and then expanded. The spatial distribution of thermokarst landslides was closely related to topography. The slope effect explained a higher occurrence of thermokarst landslides on shady slopes compared to sunny ones. Time-series InSAR also documented their deformation rates from −40 to 30 mm/year, with much higher rates on shady slopes. Coupled with permafrost stratification, wavelet analysis and time-series displacement fitting traced the stratification characteristics of thermokarst landslides. The freeze–thaw cycle of the active layer results in seasonal frost heave and thaw subsidence, and when combined with the underlying permafrost degradation can form prominent thermokarst landslides. The results quantify the kinematic characteristics of thermokarst landslides and their obvious slope effects, providing a comprehensive understanding of their intrinsic development. [ABSTRACT FROM AUTHOR]

• Developed a novel inverse Peck formula for ground heave. • Integrated Peck formula with plane freezing theory. • Used maximum likelihood for accurate frost heave width. • Empirical validation shows superior predictive accuracy. • Innovative tool impacts tunnel construction practices. The Peck formula is widely used to predict subsurface settlement in tunnel excavation without freezing techniques. However, predicting surface uplift during tunnel construction with artificial ground freezing is still a challenge. This investigation introduces a groundbreaking methodology by creatively inverting the Peck formula. By integrating the inverted Peck formula with the principles of plane freezing theory and considering stratum constraint conditions, we've developed a time-varying model to quantify the volume of stratum frost heave and the subsequent surface uplift. Through a meticulous back-analysis coupled with maximum likelihood estimation, this approach enhances the precision in gauging the extent of the frost heave mound, thereby improving the accuracy and simplicity of predicting surface uplift deformation in the tunnel construction process employing ground freezing. The robustness and credibility of this innovative approach are substantiated through an exhaustive comparative analysis juxtaposed with empirical engineering monitoring data and calculations based on the stochastic medium theory. The outcomes demonstrate that the proposed inverted Peck formula excels in its explicit clarity and practical relevance, more closely aligning with the empirical data on surface uplift than predictions derived from the stochastic medium theory, thus offering enhanced predictive performance. This study provides a novel theoretical model for anticipating surface uplift deformations in tunnel construction endeavors using ground freezing techniques, delivering valuable insights and a promising predictive tool for both engineering professionals and academic researchers. [ABSTRACT FROM AUTHOR]

The complex dynamic processes of moisture, temperature, and deformation in soil are crucial factors affecting its engineering performance in freeze-thaw environments. In this study, a unidirectional freeze-thaw cycle (FTC) experiment was conducted on silty clay. The variations in soil temperature (ST), unfrozen water content (UWC), heat flux, and vertical deformation were analyzed. The findings indicate significant differences in the variation rates of ST during freezing and thawing processes. UWC is notably impacted by ST, with the infiltration and redistribution of unfrozen water occurring due to the temperature gradient in the soil. During the thawing process, liquid water in the soil column near the top zone migrates downward under gravity, while during the freezing process, it migrates upward near the bottom zone. Moreover, the maximum value of UWC hysteresis degree occurs during the apparent transition from water to ice, with the corresponding ST approximately aligning with the freezing temperature. The hysteresis degree of UWC increases with repeated FTCs, and the increase in liquid water can enlarge the hysteresis degree near the freezing temperature. Additionally, changes in heat flux generally align with ST during FTCs; however, the heat flux gradually deviates and lags behind ST when the ST is below zero. Furthermore, the first FTC plays a crucial role in determining the vertical deformation of the soil column. [ABSTRACT FROM AUTHOR]

The asymmetric heat-water-deformation responses to solar radiation on sunny and shady slopes cause the failure of water conveyance canals in cold regions, threatening water, food, and ecological security. To investigate the influence of solar radiation on differential heat-water-deformation behaviors, a novel model test equipment incorporating solar radiation and freezing-thawing conditions was developed. A canal model was tested under different solar radiation intensities between slopes during freezing-thawing. Results show that solar radiation intensifies heat flux on the canal surface, increasing temperature while enhancing convective heat loss. Frozen soil phase change leads to solar energy storage in the sunny slope, causing a temperature difference between slopes. This leads to increased disparities in freezing depth, water content, deformation, and strain. Additionally, the disparities in freezing depth, deformation, and strain of both slopes are linearly related to the difference in daily solar radiation absorption. Under a 39.2 W/m2 intensity difference at −15 °C ambient temperature, the freezing depth, deformation, and strain of the shady slope can reach 1.4 times those of the sunny slope. Furthermore, the sunny slope has higher surface soil water content, potentially damaging the lining during thawing due to reduced freezing force. These findings enhance our understanding of canal failure mechanisms. • Develop a model test system incorporating freezing-thawing condition and solar radiation. • Test thermal transfer and heat-water-deformation responses of a canal under solar radiation. • Discuss the effect of solar radiation on the sunny-shady slope effect of a canal. • Provide recommendations for mitigating canal frost heave using solar radiation. [ABSTRACT FROM AUTHOR]

Solidified sludge was an efficient method to consume the large amount of sludge, which can be used as the subgrade filler in road engineering. However, the traditional solidified materials, such as cement and lime, consumed a large amount of natural resources and increased carbon emissions. This study used the alkali-activated recycled concrete powder (ARCP) to solidify sludge, which could be used as a potential subgrade stabilization filler. The optimal factors of ARCP were firstly determined by orthogonal test according to the compressive strength. Then the influences of different ARCP dosage, sludge moisture content and curing method on the mechanical properties, freeze-thaw resistance and heavy metals immobilization of the ARCP solidified sludge (ARCPS) were investigated. At last, microstructures of ARCPS were analyzed by SEM, XRD and TG-DTG tests. The experimental results demonstrated that the optimal mixture for ARCP: the silicate modulus of 1, liquid-solid ratio of 0.48 and calcium hydroxide content of 3 %. The solidified process by ARCP improved the mechanical properties and freeze-thaw resistance of ARCPS greatly. The 7 d unconfined compressive strength of ARCPS could reach 1305–2033 kPa when the sludge moisture content was 15 %, which meet the requirement of 500 kPa from the Chinese standard. The frost heaving rates of ARCPS were between non-frost heaving and mild frost heaving. The sludge moisture content was the most important factor affecting the freeze-thaw resistance of ARCPS. The properties of ARCPS were further improved after carbonation curing. The leaching mass concentration of heavy metals decreased significantly after the solidification of sludge. After 5 freeze-thaw cycles, the heavy metal leaching concentration increased but was still met the requirement of standards. SEM results showed that the surface of carbonated ARCPS was covered by dense scale-like carbonation products, which further enhanced the strength and freeze-thaw resistance of ARCPS. The results can be used to guide the application of sludge and ARCP in construction. [Display omitted] • The optimal mxiture for ARCP was determined to solidified sludge. • Mechanical properties and freeze-thaw resistance of ARCPS were enhanced with ARCP. • The properties of ARCPS were further improved after carbonation curing. • The heavy metals leaching decreased greatly after ARCP solidified sludge. [ABSTRACT FROM AUTHOR]

Frost heave in cold regions requires urgent measures to improve the mechanical properties of soils. However, harsh climatic and environmental conditions escalate the costs of engineering construction and operation. Therefore, it is imperative to enhance the sustainability of engineering designs. In this study, different sisal fibre contents, specific proportions of metakaolin, and alkaline activators were added to silty clay to alleviate frost heave, as well improve the mechanical properties of soils. Firstly, the unconfined compressive strength (UCS) and shear strength of soil samples containing varying sisal fibre geopolymer were tested before and after freeze-thaw cycles (FTCs). To analyse the effect of FTCs on thermal conductivity, the thermal conductivity of fibre-geopolymer solidified soil (FGSS) with different sisal fibre contents was evaluated. Subsequently, X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry were conducted on the samples before and after the FTCs. Then, the variations in soil temperature, volumetric unfrozen water content, heat flux, vertical deformation, and soil pressure during the FTCs were analyzed. The results indicated the following: 1) Sisal fibre and geopolymer improved the mechanical performance and adhesion among soil particles of FGSS after the FTCs. 2) The thermal conductivities of FGSS showed a tendency of initially increasing, then decreasing, and finally increasing as the sisal fibre content increased. 3) The addition of sisal fibres did not cause new chemical reactions but inhibited the reaction between metakaolin and the alkaline activator. 4) The combination of sisal fibre and geopolymer effectively mitigated frost heave. 5) Sisal fibre incorporation reduces CO 2 emission index and economic efficiency index. Therefore, FGSS is proposed to provide a green and effective approach for addressing geotechnical engineering issues in cold regions. • Hydro-thermal-mechanical properties of FGSS are investigated. • Sisal fibre and geopolymer improve the mechanical properties of FGSS exposed to FTCs. • 0.3 wt% sisal fibre can mitigate the frost heave of GSS by 68.51 %. • Sisal fibre effectively reduces the CIco 2 of GSS during the FTCs. [ABSTRACT FROM AUTHOR]

To investigate the effects of traffic loads on frost heave behaviors, frost heave tests of silty clay soil were conducted using an improved temperature-controlled cyclic compression-shear device. This research employed three stress modes: vertical cyclic stress, horizontal cyclic shear stress, and complex cyclic stress that combines vertical cyclic stress with horizontal cyclic shear stress. Additionally, it considered the effects of the amplitude and frequency of complex cyclic stress. Test results show vertical cyclic stress densifies specimens and restrains vertical displacement development. Vertical cyclic stress's pumping effect promotes water absorption during frost heave. Horizontal cyclic shear stress can increase in-situ frost heave and induce minor consolidation than vertical cyclic stress, dramatically enhancing vertical displacement. Under complex cyclic stress conditions, vertical cyclic stress and horizontal cyclic shear stress at low amplitudes and frequencies enhance vertical displacement. The primary component that promotes the frost heave ratio is horizontal cyclic shear stress, which could lead to a looser frozen soil structure. Finally, an improved frost heave ratio prediction model was developed, considering the influences of vertical cyclic stress, horizontal cyclic shear stress, and loading frequency. • Frost heave tests considering cyclic compression and shear stresses were conducted. • Effects of traffic loads on soil frost heave were revealed. • An improved frost heave ratio model considering cyclic stresses was established. [ABSTRACT FROM AUTHOR]

Frost heave poses a serious hazard to geotechnical engineering. However, conventional experimental and theoretical methods, which have limitations in accurately describing the deformation behavior of soils during frost heave, struggle due to the nonlinear and uncertain nature of the process. For this reason, the study leverages the advantages of the Generalized Regression Neural Network (GRNN) in handling nonlinear problems and small sample datasets. The structure of the GRNN model is further optimized using the Particle Swarm Optimization algorithm (PSO) and K-fold Cross Validation (K). The input variables for the model include water content (W), temperature (T), dry density (ρ), and plasticity index (I p) under various working conditions. The frost heave rate (η) is considered as the output variable. Meanwhile, the model also considers the effects of both one-factor and two-factor interactions among the input variables on frost heave behaviors. Finally, a prediction model for η based on the K-PSO-GRNN is established. The results demonstrate that the K-PSO-GRNN model exhibits greater robustness and stability in predicting η compared to PSO-GRNN and GRNN (R2 = 0.94, MAE = 0.14), and the prediction residuals for η range from 0 to 0.4. Among these variables, W has the most significant influence on η , followed by T , ρ , and I p. Moreover, both ρ and I p have significant interactions with T and have a notable impact on the soil's frost heave behavior. At high ρ , the soil shows reduced sensitivity to frost heave in response to changes in T , while at high I p , the soil becomes more sensitive to frost heave with changes in T. η generally shows a positive correlation with W and ρ , and a negative correlation with T. The aforementioned K-PSO-GRNN model can be utilized for predicting η , which is valuable in forecasting non-uniform deformation hazards caused by frost heave and studying preventive measures. • A GRNN is optimized by PSO and K-fold Cross Validation to predict the frost heave, which exhibits strong reliability and stability. • The proposed K-PSO-GRNN model can predict the frost heave of soil under various soil types and working conditions. • The effects of input variables on the frost heave are visualized, and water content having the greatest impact. [ABSTRACT FROM AUTHOR]

• The time domain divided into two regimes, separated by the thermal penetration time. • Mechanical stresses is analyzed, including interfacial tension and frost heave effect. • The accuracy of the proposed model is demonstrated by visualization experiment and simulation. • Theoretical guidance is provided for tailoring the freezing resistance. Water-filled capillary tubes are a kind of standard component in both life science (e.g., blood vessels, interstitial pores, and plant vessels) and engineering (e.g., MEMS microchannel resonators, heat pipe wicks, and water-saturated soils). Under sufficiently low temperatures, water in capillary tubes undergoes phase transition and exhibits frost heave, which can cause deformation, damage, and even fracture of tube wall. However, the thermo-mechanical analysis of freezing water-filled capillary tubes remains obscure, particularly regarding the rapid change in water temperature due to thermal transient effects. We develop a thermal model of freezing in a water-filled capillary tube that is suddenly exposed to cold air flow, with the time domain divided into two regimes, separated by the thermal penetration time t p. The effect of thermal penetration on temperature distribution is solved. Then, a distinction is made between freezing occurring before thermal penetration and those occurring after thermal penetration. We next analyze transient mechanical stresses acting at tube wall, with interfacial tension and frost heave effect accounted for. Results obtained are not only useful for preventing frost heave failure but also provide theoretical guidance for tailoring the freezing resistance of microfluidic devices used in MEMS. [ABSTRACT FROM AUTHOR]

To investigate the effects of acidic erosion coupled with freeze-thaw (f-t) cycles on the strength and stability of grout-reinforced red sandstone, specimens with full-penetrating and half-penetrating fractures at different inclination angles (IAs, 0–90°) were fabricated. These specimens were then reinforced with a new high-strength fast anchoring agent (HSFAA) material and subjected to coupled treatments of acidic erosion (hydrochloric acid (HCI) solution at pH = 2) and f-t cycles (0–40 cycles). Subsequently, the grout-reinforced specimens (GRSs) were tested for mass, P-wave velocity, uniaxial compressive strength (UCS) to investigate the mechanism of strength deterioration induced by the coupled effects of acidic erosion and f-t cycles, whilst scanning electron microscopy (SEM) and industrial computed tomography (CT) tests were performed to explore their microstructure damages. The findings indicated that as the number of coupled treatment cycles increased, the mass, P-wave velocity, UCS, elastic modulus (E) and deformation modulus (D) of GRSs with full-penetrating and half-penetrating fractures experienced significant decreases, with the fastest decline occurring within the first 20 cycles. GRSs with full-penetrating fractures exhibited more severe performance deterioration compared with those with half-penetrating fractures. The coupled effects of acidic erosion and f-t cycles resulted in the gradual development of intergranular and transgranular cracks on the red sandstone surface, and the generation of a complex crack network on the HSFAA surface. After 40 coupling treatment cycles, the 3D crack volume of GRSs with full-penetrating and half-penetrating fractures increased by 30.31 % and 49.52 %, respectively, compared with untreated GRSs. The primary mechanisms responsible for the strength reduction and damage of GRSs included the chemical dissolution of gelling products in the HSFAA, the frost heaving stresses induced by f-t cycles, and the gradual detachment at the interface between HSFAA and sandstone. • The Red sandstone specimens with fractures were reinforced by grouting. • The coupling effects of acidic erosion and freeze-thaw cycles were studied. • The performance of the specimen deteriorated fastest in the first 20 cycles. • The mechanism of strength deterioration and microstructure damage was revealed. • The coupling treatment significantly increased the crack volume inside the specimen. [ABSTRACT FROM AUTHOR]

Damage development in rocks by freeze-thaw cycles, a phenomenon that is typical to cold regions, is known to reduce the strength and durability of structures. In this study, a series of freeze-thaw tests were performed on frost and non-frost heave rocks to examine the impact of frost heave susceptibility and temperature-changing conditions on rock behaviors. The freeze-thaw life and uniaxial compressive strength (UCS) of rocks subjected to freeze-thaw cycles were estimated using a model that was based on fatigue damage mechanisms. Furthermore, we proposed a method for estimating the freeze-thaw life of rocks, using expansive strain as an important factor. The results indicated that the Shikotsu welded tuff (a non-frost heave rock) exhibited higher durability than the Noboribetsu welded tuff (a frost heave rock); this may be because the Shikotsu welded tuff had a larger pore radius and more unsaturated pores. The one-dimensional (1D) cooling-heating conditions induced significantly less damage than the three-dimensional (3D) conditions, owing to the continuous migration of free water into the unfrozen zone. The damage model estimated that for the Noboribetsu welded tuff, the freeze-thaw life in the 1D conditions was approximately eight times longer than that in the 3D conditions. Notably, with respect to the Shikotsu welded tuff, a critical freeze-thaw period induced significant expansion, resulting in damage development in the tuff. The freeze-thaw life of each rock sample was estimated based on the magnitude of the volumetric expansive strain. This study contributes to the rational assessment of the stability and durability of rock structures in cold regions. • Non-frost heave rock samples exhibited higher durability than frost heave rocks • The 1D freeze-thaw cycles induced less damage compared to the 3D cycles • Damage development in rocks exposed to long freeze-thaw periods was elucidated • A model based on the fatigue damage mechanisms was employed • An estimation method based on the expansive strain was proposed [ABSTRACT FROM AUTHOR]

Despite substantial research on stabilizing sulfate saline soil, the behavior of post-stabilization pure salt expansion remains unclear. Understanding this behavior is essential because it can lead to soil degradation, potentially undermining the stability and lifespan of constructed infrastructure. To investigate the pure salt expansion and process of solidified and non-solidified sulfate saline soil under negative temperature, single-cycle cooling test, freeze-thaw cycles test were carried out. Various Na 2 SO 4 content (i.e., 0.3%, 1%, 2%, 3.5%, and 5%) and c(NaCl) / c(Na 2 SO 4) ratio (i.e., 0, 0.6, 1.2, and 2.0) were considered. Scanning electron microscope (SEM) observations and mercury intrusion porosimetry (MIP) were employ to analyze the pore structures and quantitatively characterize the multi-scale micropores. Results indicated that during a single-cycle cooling, the salt expansion of solidified saline soil was significantly smaller than that of non-solidified saline soil, with the difference reaching up to 36.4 times. After three freeze-thaw cycles at a Na 2 SO 4 content of 2%, the final average salt expansion of solidified saline soil was only 41.8% of that in non-solidified saline soil. Under the same salt content, solidified saline soil had smaller and more evenly distributed pores. The proportion of small pores below 1 μm was 37.1%, 4.5 times higher than in non-solidified saline soil. Solidified saline soils with higher Na 2 SO 4 content or chlorine-sulfate ion ratio had a greater proportion of large and small pores. Solidified saline soils with 3.5% Na 2 SO 4 content had a proportion of pores above 100 μm as high as 23%. The research findings will serve as a reference for controlling salt expansion disease and facilitating engineering construction in sulfate saline soil areas. • Ethylene glycol was added to eliminate frost heave in sulfate saline soil. • Pure salt expansion of solidified and non-solidified sulfate saline soil was investigated. • Pure salt expansion process of sulfate saline soil under single-cycle cooling and freeze-thaw cycles was investigated. • Pore structures and multi-scale micropores were quantitatively characterized. [ABSTRACT FROM AUTHOR]

Lined canals in cold regions often experience severe frost damage, posing a significant threat to the water supply safety. This paper proposes a modified analytical solution for the response of canal lining under soil frost heave, which is based on a Timoshenko beam on a Pasternak foundation considering tangential contact between the lining and frozen soil. This analytical solution can provide any solution using Timoshenko or Euler–Bernoulli beams on Pasternak or Winkler foundations with or without tangential contact. Then, the modified analytical solution, along with the traditional analytical solutions using Euler–Bernoulli beams on Winkle foundations, is compared against both model test and numerical simulation results. The modified analytical solution performs better than the traditional solution. Finally, the effects of foundation model, beam model, and tangential contact in simulating canal frost heave were discussed, and some measures to mitigate canal frost heave are proposed. The results show that solutions based on Winkler foundation overestimate frost heaves and tensile stresses of canal linings, and solutions without considering tangential contact only obtains overestimated frost heave. In addition, solutions based on Euler–Bernoulli beams underestimate frost heaves slightly and overestimate tensile stresses slightly. Therefore, the Pasternak foundation, Euler–Bernoulli beam, and tangential contact model can be used to simulate canal frost heave. The modified analytical solution directly uses field measurements of soil free frost heave to calculate canal frost heave, thereby enhancing result reliability. This analytical solution provides a simple method for canal frost heave design, and can be applied to frost heave analyses of flat and inclined structures. [Display omitted] • Propose analytical solution considering shear effects of the lining, frozen soil, and their tangential contact. • Perform model test and numerical simulation to verify the accuracy of the analytical solution. • Discuss the applicability of foundation and beam models on simulating canal frost heave. • Factors studied include the shear layer stiffness, and normal and tangential contact conditions. [ABSTRACT FROM AUTHOR]

• Severe permafrost degradation was found beneath the EBTS, with temperatures nearing thawing point. • 80% settlement from foundation ground, transition weakening can cause up to 49% of total settling. • Expansion joint was still observed narrowing during winter despite partial abutment-beam contact. • Backfill frost heave induced abutment displacement, resulting in expansion joint failure. Differential embankment settlement and expansion joint failure in the embankment bridge transition section (EBTS) are two main issues endangering the safety of the Qinghai-Tibet Railway (QTR) in permafrost. A better understanding of the causes of EBTS deformation can offer valuable guidance for engineering maintenance. In this study, a comprehensive field investigation and a series of simulations were carried out to reveal the formation causes. The results revealed significant permafrost degradation beneath the EBTS after 15 years of operation, with temperatures nearing the thawing point. Despite contact between the abutment and beam end, the expansion joint exhibited continuous narrowing, particularly during the cold season. Permafrost degradation was primarily attributed to the heating effect of adjacent bridge structures. Foundation ground settlement emerged as the primary cause of embankment settlement in the transition section, contributing up to 80 % of the total settlement. Differential embankment settlement of the EBTS primarily stemmed from the uneven warming or thawing of permafrost, induced by the thermal impact of the adjacent bridge structures. The weakening of the transition section had a concentrated impact on embankment settlement within a 12-meter span behind the abutment, inducing approximately 30 % to 50 % of the embankment settlement. The backfill soils near the abutment experienced severe lateral frost heave in cold seasons. Horizontal displacement of the abutment caused by the lateral frost heave was identified as the main reason for expansion joint failure. Additional cooling measures are necessary to ensure the long-term stability of the EBTSs along the QTR, considering the faster degradation of ambient permafrost than expected. The findings offer valuable insights for the maintenance and design of railways in permafrost regions. [ABSTRACT FROM AUTHOR]

During the horizontal freezing construction of a subway tunnel, the delay of the closure of the frozen wall occurs frequently due to the existence of groundwater seepage, which can be directly reflected by a freezing temperature field. Accordingly, the distribution of ground surface frost heaving displacement under seepage conditions will be different from that under hydrostatic conditions. In view of this, this paper uses COMSOL to realize the hydro–thermal coupling in frozen stratum under seepage conditions, then, the frost heaving distribution of seepage stratum in tunnel construction using horizontal freezing technique is researched considering the ice–water phase transition and orthotropic deformation characteristics of frozen–thawed soil by ABAQUS. The results show that the expansion speed of upstream frozen wall is obviously slower than that of the downstream frozen wall, and the freezing temperature field is symmetrical along the seepage direction. In addition, the ground frost heaving displacement field is asymmetrically distributed along the tunnel center line, which is manifested in that the vertical frost heaving displacement of the upstream stratum is less than that of the downstream stratum. The vertical frost heaving displacement of the ground surface decreases with the increase in tunnel buried depth, but the position of the maximum value remains unchanged as the tunnel buried depth increases. The numerical simulation method established in this paper can provide a theoretical basis and design reference for the construction of a subway tunnel in a water-rich stratum under different seepage using the artificial freezing technique. [ABSTRACT FROM AUTHOR]

Forest fires significantly impact permafrost degradation in the subarctic regions. However, interannual and seasonal variations in surface deformation due to permafrost thawing in burned areas were poorly understood. Measuring the ground surface displacement in fire scars helps us understand the freeze‐thaw dynamics of near‐surface ground and predict the future state, particularly in ice‐rich permafrost regions. This study used the L‐ and C‐band interferometric synthetic aperture radar technique to reveal interannual subsidence and seasonal thaw settlement/frost heave in a fire scar near Mayya, Sakha Republic in Eastern Siberia burned in 2013. We found that the cumulative subsidence was up to 7 cm between 2014 and 2020, most of which had occurred by 2016. The magnitude of seasonal thaw settlement and frost heave varied each year from 2017 to 2020 after the fire, but the interannual change in frost heave corresponded to the temporal variation in precipitation during the thawing season from 2017 to 2020. This suggests that the precipitation amount during the thawing season is related to the magnitude of segregation‐ice formation in the sediments, which determines the frost heave amount. The observed seasonal displacements could not be quantitatively explained by models inferred from the Stefan's equation and volume changes associated with ice‐water phase change. This implies that other models associated with segregated ice (ice lens) formation/thaw are required to explain the observed seasonal displacement. Plain Language Summary: Forest fires in permafrost regions significantly affect regional landscape changes and ecosystems through permafrost degradation and subsequent ground deformation. However, the number of observations of post forest fire surface displacement is extremely limited. We calculated surface displacement in a fire scar in Eastern Siberia from spaceborne radar images captured using interferometric synthetic aperture radar. Our observed data will help us understand permafrost degradation processes in forest fire scars. Key Points: Ground subsidence was primarily associated with the severity of forest fires, and slope orientation was likely an additional factorSeasonal frost heave measured by interferometric synthetic aperture radar was correlated to precipitation amount in thawing seasonExisting phase change model could not explain observed seasonal displacement quantitatively [ABSTRACT FROM AUTHOR]

Ground ice distribution and abundance have wide-ranging effects on periglacial environments and possible impacts on climate change scenarios. In contrast, very few studies measure ground ice in the High Arctic, especially in polar deserts and where coarse surficial material complicates coring operations. Ground ice volumes and cryostructures were determined for eight sites in a polar desert, near Resolute Bay, Nunavut, chosen for their hydrogeomorphic classification. Dry, unvegetated polar desert sites exhibited ice content close to soil porosity, with a <45 cm thick ice-enriched transition zone. In wetland sites, suspended cryostructures and ice dominated cryofacies (ice content at least 2× soil porosity values) were prevalent in the upper ∼2 m of permafrost. Average ground ice saturation at those locations exceeded porosity values by a factor between 1.8 and 20.1 and by up to two orders of magnitude at the ∼10 cm vertical scale. Sites with the highest ice contents were historically submerged wetlands with a history of sediment supply, sustained water availability, and syngenetic and quasi-syngenetic permafrost aggradation. Ice enrichment in those environments were mainly caused by the strong upward freezing potential beneath the thaw front, which, combined with abundant water supply, caused ice aggradation and frost heaving to form lithalsa plateaus. Most of the sites already expressed cryostratigraphic evidence of permafrost degradation. Permafrost degradation carries important ecological ramifications, as wetland locations are the most productive, life-supporting oases in the otherwise relatively barren landscape, carrying essential functions linked with hydrological processes and nutrient and contaminant cycling. [ABSTRACT FROM AUTHOR]

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A series of freezing experiments were carried out on the Qinghai silty clay using a one-dimensional soil column particle image velocimetry (PIV) system. The effects of the initial water content and temperature gradient on the frost heave of the soil column were analysed. The experimental results show that the total volumetric water content after the Qinghai silty clay freezing is much greater than the initial water content before freezing, and the total volumetric water content at the segregated layer reaches the maximum value. The average unfrozen water content firstly increases sharply with time and then decreases slowly. The obvious horizontal layered segregation cracks filled with unsaturated needle-columnar ice lenses have occurred above the soil column frozen fringe. The thickness of segregated ice is about 43% of the total frost heave. There is a small frost heave in the frozen fringe and a small compression deformation amount in the unfrozen zone. Under the same temperature gradient conditions, the soil column with the low initial water content has a smaller frozen depth, larger total volumetric water content, more water intake, smaller segregated ice thickness, and less total frost heave amount than that of the soil column with the high initial water content. Under the same initial water content conditions, the soil column with a large temperature gradient has a greater frozen depth, consistent total volumetric water content, larger segregated ice thickness, and greater total frost heave amount than that of the soil column with a small temperature gradient. [ABSTRACT FROM AUTHOR]

The installation of composite insulation material in canals will reduce the frost heave force of foundation soil and the displacement caused by uneven frost heave of canal slope plate. However, the research on the anti-freezing mechanism of composite insulation material in canals has not been proved. In this paper, the application of polymer material under the canal lining structure of Xinjiang Manas Power Station was taken as the actual engineering background. Considering the interaction between composite materials and the interaction between frozen soil and composite materials, the frost swelling model of concrete lining insulation structure in cold area was established according to the canal thermodynamic coupling mechanism, and three new composite insulation forms were proposed and analyzed by COMSOL Multiphysics5.2 a. The results show that compared with the conventional canal, the three thermal insulation methods have certain thermal insulation effect, and the third one has the most obvious frost resistance and thermal insulation effect. Under the action of this form, the maximum normal displacement of shady slope, sunny slope and base-plate is 9.63 cm, 4.74 cm and 1.87 cm respectively and compared with the prototype canal, the frost heaving force of form 1, form 2 and form 3 is reduced 65.8%, 76.2% and 89.5% respectively. [ABSTRACT FROM AUTHOR]

The stability of slope rock masses is influenced by freeze-thaw cycles in cold region, and the mechanism of stability deterioration is not clear. In order to understand the damage and progressive failure characteristics of rock masses under the action of freezing and thawing, a model test was conducted on slope with steep joint in this study. The temperature, frost heaving pressure and deformation of slope rock mass were monitored in real-time during the test and the progressive failure mode was studied. The experimental results show that the temperature variations of cracking and the rock mass of a slope are different. There are obvious latent heat stages in the temperature-change plot in the crack, but not in the slope rock masses. The frost heaving effect in the fracture is closely related to the constraint conditions, which change with the deformation of the fracture. The frost heaving pressure fluctuates periodically during freezing and continues to decrease during thawing. The surface deformation of the rock mass increases during freezing, and the deformation is restored when it thaws. Freeze-thaw cycling results in residual deformation of the rock mass which cannot be fully restored. Analysis shows that the rock mass at the free side of the steep-dip joint rotates slightly under the frost heaving effect, causing fracture propagation. The fracture propagation pattern is a circular arc at the beginning, then extends to the possible sliding direction of the rock mass. Frost heaving force and fracture water pressure are the key factors for the failure of the slope, which can cause the crack to penetrate the rock mass, and a landslide ensues when the overall anti-sliding resistance of the rock mass is overcome. [ABSTRACT FROM AUTHOR]

With the rapid development of agricultural economy, people are paying more and more attention to how to apply high-efficiency technologies that save resources to improve agricultural production efficiency, so water-saving irrigation technology has gradually developed. China's agricultural irrigation technology is relatively backward. In addition to the inappropriate irrigation methods and irrigation systems, problems such as siltation, seepage, and frost heave damage in irrigation canals have seriously affected the durability and service life of the canals. The backward irrigation technology seriously restricts the development of agricultural water-saving irrigation. Compared with large irrigation channels, the fabricated reinforced concrete small irrigation channels studied in this paper are less prone to frost heave damage and infiltration problems, and have the advantages of standardized production, simple transportation and installation, and convenient maintenance. In order to study the durability issues such as the basic characteristics, frost heave damage, and service life of fabricated irrigation channels, this paper takes the channel concrete and the formed channel as the research objects, and discusses the research on the properties of the channel concrete through theoretical research, numerical analysis, experiments, and other methods. Strength properties, water penetration resistance, cyanide ion penetration resistance and frost resistance; simulate the seasonal frost heave failure process of the channel; finally, on the basis of the test data, the service life aims to explore the safety and applicability of the fabricated reinforced concrete irrigation channel during the design use period. [ABSTRACT FROM AUTHOR]

The incorporation of steel fibers into the natural soil is generally considered to be a novel and effective way to reduce the amount of frost heave induced by an artificial freezing process in underground engineering. In order to analyze the frost heave behavior of the steel fiber improved soil, a one-dimensional frost heave test under the open recharge system was conducted in this paper, focusing on the influence of steel fiber content, size, and soil properties. The results show that small amounts of steel fibers in the soil will not significantly affect the freezing process and temperature distribution, while the water-conducting properties of the steel fibers and the effect of limiting the ice lens growth can reduce the frost heave rate of the samples incorporated with 0.5% steel fibers by 26.93%. At the same time, the reduction effect of the frost heave rate increases linearly with the increase of steel fiber content and length but weakens with the increase of steel fiber diameter. In terms of soil property influence, the frost heave rate of the clay samples was reduced by 14.31% compared to the silt samples, while the water migration was reduced by 11.99%. In addition, the cementation of the steel fibers with the soil will also inhibit the growth of the ice lens and reduce the external water migration, thus significantly lowering the frost heave rate. The results can provide a reference for the research of the frost deformation of similar modified soils. [ABSTRACT FROM AUTHOR]

Frost heaving damage of canal lining in cold and dry areas is one of the important causes of canal leakage. In this paper, based on the bending theory of thin plate, a mechanical model of canal lining under the action of frost heaving force is established and solved. Through parametric and engineering case analysis, the following conclusions are drawn: under the action of frost heaving force, the bending moment, shear force, and internal force of the slope plate show a nonuniform distribution, and the maximum values of bending moment Mx and normal stress σx are close to the bottom third of the slope, which is consistent with the existing research and engineering practice. Compared with the theory of beam, the results of the theory of thin plates show that the internal forces and stresses increase at the free boundary (longitudinal expansion joint). The bending moment Mxy and stress τxy are maximum at the four corners of the plate: although the numerical magnitude is lower than that of Mx, it may cause stress concentration to damage the lining plate and thus cause break. The shear force at the longitudinal expansion joint may lead to fracture of the joint material, which needs to be considered in the design process. Due to the uniform distribution of the frost heaving force on the bottom plate lining, its deflection, internal forces, and stresses also show a uniform distribution. The research results can provide scientific reference for the design and operation and maintenance of water transmission canal lining in cold areas. [ABSTRACT FROM AUTHOR]

There is a significant difference between ambient temperature and internal temperature of surrounding rock in the cold season. Based on the Dulongjiang (DLJ) Tunnel, this paper studies the influence of frost heave force on lining structure and establishes a thermos-dynamical coupling model using the field. The results show that the environmental temperature and the cavity behind the lining greatly influence the safety of the tunnel structure. The internal force of the tunnel lining increases with the decrease of the environmental temperature and stress. The existence of a water-bearing cavity causes the deformation of the vault position to improve and advance. In contrast, the deformation presence of a water-bearing hole causes the deformation of the vault position to increase and reach, while the deformation time of the arch foot position to delay. [ABSTRACT FROM AUTHOR]

To investigate the frost heaving properties of gravelly soil in alpine seasonally frozen regions and provide a foundation for the antifrost heaving design of the foundation tower in the Manzhouli 500 kV electrical transmission line. First, particle analysis and compaction tests were used to assess the basic characteristics of gravelly soil. Then, to investigate, a unidirectional freezing test of graded sand was performed to analyze the regularity and properties of the frozen process of graded sand. The test results demonstrate that the temperature gradient and the number of freeze-thaw cycles considerably affect the freezing of graded sand. The greater the temperature gradient and the number of freeze-thaw cycles, the greater the frost heave. In the freezing process, graded sand with zero fine-grain content exhibits obvious freezing shrinkage and thawing settlement. Still, the frost heave of sand is small. The frozen damage of graded sand is not caused by frost heaving deformation but by the deterioration of soil structure and the decrease of bearing capacity under hydrothermal coupling. Finally, experimental research is used to propose prevention and control measures for frost heave of power transmission and transformation projects. [ABSTRACT FROM AUTHOR]

Based on the similarity theory, a laboratory experiment considering the influence of rainfall was performed to study the water-heat behavior and freeze-thaw deformation between the normal embankment and the composite embankment, consisting of permeable geotextile, crushed-rock interlayer, and waterproof geomembrane. The results showed that due to the existence of crushed-rock interlayer, the effective frozen depth of the composite embankment was smaller than that of the normal embankment. In the rainfall period, because of the drainage function of permeable geotextile and a crushed-rock layer, the water content of soil upon the crushed-rock of the composite embankment was lower than that of the normal embankment. Meanwhile, the waterproof geotextile blocks the upward migration of water in the deep soil, which only changes under the freeze-thaw cycles. Therefore, compared with the normal embankment, the composite embankment can reduce the frost heave and uneven deformation of the embankment under the condition of rainfall infiltration, effectively avoiding the formation of longitudinal cracks of the embankment. [ABSTRACT FROM AUTHOR]

Air temperature in the Northern Hemisphere has been progressively warming in the recent decades, and the ground temperatures have increased correspondingly. The air temperature increasing due to the climate change induces degradation of permafrost and frost heaving activation. The frost heaving forces cause unevenly distributed damaging displacement of foundations and thus poses problems to the development of Arctic regions. Frost-heave uplift forces can be reduced by protecting piles with an OSPTReline (or Reline) polymer heat-shrinkable jacket. The interaction of heaving soil with a pile covered with the Reline jacket is modeled in laboratory to estimate the uplift force and the related shear strength of frozen soil along the soil-pile adfreeze surface at temperatures from −6 to −1 °C. The data are obtained for silty sand and silty clay soils and mortar (1:5 cement-sand mixture). The experiments show that frost-heave uplift forces on Reline-protected piles are 52% to 85% lower than on uncovered steel piles (steel grade 09G2S—analog to European steel grade S355JR), depending on soil type and temperature. [ABSTRACT FROM AUTHOR]

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower 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.)

The freeze-sealing pipe roof (FSPR) method was applied as an innovative construction technology to the Gongbei Tunnel of the Hong Kong–Zhuhai–Macau Bridge. A freezing scheme involving master freezing tubes, enhancing freezing tubes, and limiting freezing tubes is the key component of the freezing effect of the FSPR method during the construction process under various working conditions. This is related to whether the thickness and temperature of the frozen soil meet the design requirements under various complex working conditions, and it is also related to frost heave control and energy saving. Based on the unsteady-state conjugate heat transfer model, different freezing schemes of enhancing freezing tubes—that is, the shape, layout, operating duration, and heat preservation—were simulated to analyze the freezing effect, which can be measured by the thickness of frozen soil around the steel pipes and the average temperature of the frozen soil curtain. The results show that the greater the contact area between the enhancing tube and the inner wall of the steel pipe, the better the freezing effect, and that the semicircle enhancing freezing tube scheme is superior to the other three shapes of freezing tubes. The arrangement of enhancing freezing tubes far away from the excavation surface, without heat preservation measures, has a better freezing effect due to the function of the hollow pipe as a freezing pipe. Moreover, the enhancing freezing tube can be operated intermittently to control frost heave. Our research simulated the temperature fields of different media—such as steel pipes, frozen soil, and air—providing a design basis for similar projects, such as the combination of the pipe-roofing method and artificial freezing method. [ABSTRACT FROM AUTHOR]

Frost heave is an important factor affecting the safety and practicability of buildings in cold regions or artificial freezing engineering. In order to reduce frost heave, frost-susceptible silty clay was used in a one-dimensional frost heave testing system in three different freezing modes. The results show that, compared with the continuous freezing mode, frost heave in the intermittent freezing mode and the continuous-intermittent freezing mode is reduced by 14.4% and 43.6%, respectively. These results clearly demonstrate that frost heave can be restrained in the continuous-intermittent freezing mode more effectively than in the other two freezing modes. The periodic step growth on the frost heave curves in the continuous-intermittent freezing mode is the main reason for this, as explained by the frost heave theory in this paper. To acquire appropriate settings on the cold end temperature, frost heave tests were carried out at different amplitudes and periods of temperature change in the continuous-intermittent freezing mode. The frost heave decreases with the increase of the amplitude of temperature change and period of temperature change. The power function growth, periodic step growth and periodic polyline growth are shown on the frost heave curves at different periods of temperature change of 2, 4, and 8 h, respectively. Due to the good inhibition effect of frost heave, periodic step growth will be a better way to reduce frost heave, which is of great significance to the life cycle safety of buildings. [ABSTRACT FROM AUTHOR]

This study aimed to clarify the mechanism of the effect of surface charge of clay particles on the separation pressure between adjacent frozen clay particles. A general mathematical model of separation pressure between adjacent spherical clay particles was given based on the extended colloidal stability (DLVO) theory; it was introduced into the frost heave process, and the functional expression of separation pressure and freezing temperature between clay particles was derived by using the relationship between the pore throat's radius and freezing temperature, which was verified by the existing experimental results. Finally, the effects of the freezing temperature, mineral species and solution concentration on the freezing separation pressure and ice-lens growth were analyzed. Our results show that the surface distance of adjacent charged bodies is a single-valued function of their separation pressure, but the freezing temperature is the main factor affecting the separation pressure between adjacent frozen clay particles; the separation pressure between adjacent clay particles is proportional to its surface-charge density. For the same particle spacing, the separation pressures of kaolinite and illite are not much different, but they are both about one order of magnitude lower than montmorillonite; the separation pressure between clay particles is negatively correlated with the solution concentration. When the solution concentration is less than 0.1 mol · m−3, the effect of the solution concentration on the separation pressure between particles is negligible. The research results can provide a theoretical reference for improving the existing geotechnical frost heave theory. [ABSTRACT FROM AUTHOR]

Construction of oil and gas infrastructure facilities on permafrost soils is the most important task of increasing the raw material base of the entire fuel and energy industry in Russia. Permafrost soil is a complex, multicomponent system, state of which depends on many factors. Buildings and structures built under such conditions, on the one hand, have a complex thermal effect on permafrost soils, and on the other hand, they perceive the consequences of changes in the characteristics of such soils. This situation leads to the fact that buildings and structures on permafrost soil during their life cycle are subject to complex and poorly predictable deformations. Article presents the results of a study for various degradation processes of permafrost soils that can be implemented at construction sites of industrial facilities. Analysis of the deformations causes for engineering structures at the gas industry in the permafrost zone is carried out. Series of reasons causing such deformations have been investigated. Comprehensive criterion for assessing changes in permafrost-geological conditions of industrial sites is proposed. It is suggested to apply the method of calculating the individual characteristics for the temperature regime of the territory to monitor and assess the conditions of heat exchange and predict changes in the geocryological conditions of permafrost soil.

The object of the research is pile-soil interaction under freezing and frost heaving. Modeling of pile-soil interaction on the basis of joint solution of static equilibrium equations, physical equations for stresses and equation of thermal conductivity is considered. No such solutions have been found in existing publications. In this study, a model of pile-soil interaction in the form of a closed analytical solution with respect to the pile geometry was developed. Methods of continuum mechanics and elasticity theory were used. The model was a mathematical record of the equilibrium of forces acting on the pile. It was reduced to second-order algebraic equations with respect to its geometric parameters. The static equations of force equilibrium written in quadratic form related the geometric parameters of the pile to the stress-strain state and the thermal characteristics of the soil. Physical equations for heaving stresses and the thermal conductivity equation closed the problem. The model was developed as applied to a pile with an upper reverse taper. It reflected the performance of the pile during freezing and frost heaving and allowed determining its required geometric parameters under the given soil and climatic conditions.

This document is a discussion of a research paper titled "Experimental and Numerical Investigations of Frost Heave Characteristics of a Transmission Tower Foundation along the Lanzhou–Lintao Power Transmission Line." The authors conducted experimental and numerical studies on the behavior of the foundation of a transmission tower in frost-susceptible soils in Linto County, China. They investigated various conditions such as surface temperature, tangential frost heaving force, and water content distribution. The authors made recommendations based on their findings and addressed the results of both the experimental and numerical analyses. However, there are some areas in the presentation of the results that require further explanation or clarification. [Extracted from the article]

When the buried pipeline passes through the permafrost zone, the phenomenon of frost swelling occurs in the permafrost zone, which causes a certain degree of bending and deformation of the pipeline. As a result, the pipeline's structural safety is compromised, and the pipeline finally fails during operation, posing a serious hazard to the natural gas pipeline's operation. Whereas the theoretical research on soil frost heave is relatively comprehensive, the applied research on engineering problems is not yet complete. Therefore, it is necessary to predict frost heaving through experiments and numerical simulation, and put forward reasonable control measures for existing or potential problems. For the problem of pipeline damage caused by frost swelling of soil in the natural gas high-pressure regulator station in a river and creek region, the Drucker–Prager elastic-ideal plastic model of soil was selected for finite element analysis, and a reasonable finite element model of pipe-soil was established in this paper. Through the temperature field analysis, it was found that the soil around the buried pipe is affected by the pipeline and is lower than its freezing temperature, which makes the soil freeze and swell. Furthermore, through the thermal–structural coupling analysis, it was found that the buried pipe is affected by the freezing and swelling of the soil and the structure is greatly likely to be damaged. In addition, by analyzing the temperature distribution and frost heave deformation of the soil around the pipeline, as well as the deformation and force of the pipeline at different pipe temperatures, this paper also determined the ideal temperature for preventing frost heave damage to natural gas at high-pressure regulator stations as −1 °C. Finally, based on the results of the abovementioned analysis, the heating method was determined to improve the frost damage phenomenon at the high-pressure regulator. The results of the anti-frost and swell study were used to conduct field trials at natural gas high-pressure regulator stations where frost and swell had occurred. By adding heating furnace to increase inlet temperature, frost heaving of gas transmission pipeline can be effectively prevented. The results of the research provide a reference for both existing and new natural gas pipelines, and also accumulate experience for winter maintenance design and construction of pipeline engineering in seasonally frozen soil areas. [ABSTRACT FROM AUTHOR]

Projects in seasonal frozen soil areas are often faced with frost heaving and thawing subsidence failure, and the foundation fill of most projects is a mixture of soil and rock. Therefore, taking soil–rock mixture with different rock contents as research objects, the residual deformation of soil–rock mixture under multiple freezing–thawing cycles is studied. In addition, the deep learning method based on the artificial neural network was pioneered combined with the freezing–thawing test of the soil–rock mixture, and the Long short-term memory (LSTM) model was established to predict the results of the freezing–thawing test. The LSTM model has been verified to be feasible in the exploration of the freeze–thaw cycle law of a soil–rock mixture, which can not only greatly reduce the period of the freeze–thaw test, but also maintain a high prediction accuracy to a certain extent. The study found that the soil–rock mixture will repeatedly produce frost heave and thaw subsidence under the action of freeze–thaw cycles, and the initial frost heave and thaw subsidence changes hugely. With the increase of the number of freeze–thaw cycles, the residual deformation decreases and then becomes steady. Under the condition that the content of block rock in the soil–rock mixture is not more than 80%, with the increase of block rock content, the residual deformation caused by the freeze–thaw cycle will gradually decrease due to the skeleton function of block rock, while the block rock content's further increase will increase the residual deformation. Furthermore, the LSTM model based on an artificial neural network can effectively predict the freezing and thawing changes of soil–rock mixture in the short term, which can greatly shorten the time required for the freezing and thawing test and improve the efficiency of the freezing and thawing test to a certain extent. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & 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.)

Improving the temperature prediction accuracy for subgrades in seasonally frozen regions will greatly help improve the understanding of subgrades' thermal states. Due to the nonlinearity and non-stationarity of the temperature time series of subgrades, it is difficult for a single general neural network to accurately capture these two characteristics. Many hybrid models have been proposed to more accurately forecast the temperature time series. Among these hybrid models, the CEEMDAN-LSTM model is promising, thanks to the advantages of the long short-term memory (LSTM) artificial neural network, which is good at handling complex time series data, and its combination with the broad applicability of the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) in the field of signal decomposition. In this study, by performing empirical mode decomposition (EMD), ensemble empirical mode decomposition (EEMD), and CEEMDAN on temperature time series, respectively, a hybrid dataset is formed with the corresponding time series of volumetric water content and frost heave, and finally, the CEEMDAN-LSTM model is created for prediction purposes. The results of the performance comparisons between multiple models show that the CEEMDAN-LSTM model has the best prediction performance compared to other decomposed LSTM models because the composition of the hybrid dataset improves predictive ability, and thus, it can better handle the nonlinearity and non-stationarity of the temperature time series data. [ABSTRACT FROM AUTHOR]

It is very important to accurately calculate the frost heave force for the frost resistance design of tunnels in cold regions. A computational model will divide the lining and surrounding rock into eight parts, such as the support zone, the frozen zone (e.g., isothermal Rings I, II, III, IV, V, and VI), and the unfrozen surrounding rock Zone VII. The model will consider the influence of the inhomogeneity of the mechanical parameters of the frozen surrounding rocks that are caused by the temperature field on the calculation results for the frost heave force. Based on the case analysis, the elastoplastic analytical solution of the stress and deformation of the surrounding rock in a cold region tunnel will be obtained. The results show that: (1) if the basic physical and mechanical parameters of the frozen surrounding rock are taken as constants, the calculation results of frost heave force, plastic radius (rp), and circumferential stress (σθ) at the excavation radius will be smaller than that of the model proposed in this paper, and the freezing resistance design of the tunnel lining in cold regions based on the uniform parameter model might lead to lining damage due to insufficient support strength in the later stage; (2) the results of variance analysis show that the inner radius of the lining (ra) and radius of Zone 7 (r7) had a significant effect on the frost heave force in all cases, and the elastic modulus of the lining (E0) was significant. The influence of the elastic modulus of Zone 7 (E7) and in situ stress (p0) on the frost heaving force was not significant; and (3) the influence law of the displacement release coefficient (η), E0, and p0 on the force that acted on the lining will be analyzed. The model to calculate the frost heave force and the related conclusions could have guiding significance for the frost resistance design and numerical simulation of tunnels in cold regions. [ABSTRACT FROM AUTHOR]

This case study proposed and evaluated an approach to repair post-tensioned prestressed concrete bridge girders in cold regions. The girders had severe frost-heaving cracks and unhardened cementitious grout in the prestressing ducts. Three full-scale girders were retrieved from a real highway bridge located in the Tibetan Plateau. The girders were repaired with two types of polymeric adhesives and evaluated through borehole and anatomy examinations and flexural tests after repairing. The results of the borehole and anatomy examinations of the damaged and repaired girders showed that polymeric adhesives filled the ducts and cracks. Flexural test results showed that the repairing significantly enhanced the load capacity, ductility, and crack resistance of the bridge girders. The mechanisms of the improvement in flexural properties due to the repairing are discussed. This research offers practical solutions and insights into the mechanisms for the repairing of post-tensioned prestressed concrete girders with frost-heaving damage. [ABSTRACT FROM AUTHOR]

In order to reveal the instability law of open pit mine slope in high-cold and high-altitude area. Firstly, the slope structural plane is scanned by three-dimensional (3D) laser scanning technology, and the point cloud data is obtained to realize the intelligent identification of rock mass structural plane. The geometric parameters of rock mass are counted, and the physical structure model is established. Then, we carry out freeze-thaw cyclic tests on granite to obtain the corresponding mechanical parameters. Finally, according to the obtained mechanical parameters, we use RS2 finite element software to calculate the shear strength of structural plane and joint by generalized Hoek-Brown criterion and Barton-Bandis criterion, respectively, establish the geomechanical model, and use the finite element strength reduction method to calculate the safety factor of slope and judge the instability of slope. The results show that the physical and mechanical properties of granite deteriorate with the increase of the freeze-thaw cycle. Under the action of the freeze-thaw cycle, the pore water in the rock mass freezes and forms frost heaving force. The expansion of volume leads to the further development of joint fissures. The strength of rock slope decreases gradually with the increase of freeze-thaw cycle times, and the safety factor of slope decreases continuously. It shows that repeated freeze and thaw alternation makes the stability of mine slope worse and worse. The research results are helpful to prevent the occurrence of slope disasters in advance and are of great significance to effectively and safely manage the stability of slope, the treatment of open pit, and environmental treatment. [ABSTRACT FROM AUTHOR]

The water content of the foundation soil will change dynamically as a result of rainfall, snowfall, and ground surface evaporation, leading to a significant change in frost heave properties of the foundation soil in cold regions. One-dimensional freezing tests of the Qinghai-Tibet silty clay with three different initial water contents in an open system were carried out using CCD image acquisition technology and computed tomography (CT) scanning technology in combination with the traditional soil freeze-thaw test system. The heat conduct process, cryostructure formation, frost heave development, unfrozen zone consolidation, ice segregation, water migration, and redistribution during soil freezing are studied comprehensively. The results show that increasing the sample's initial water content will lead to the increase of frozen depth, ladder-like cryostructures in vertical sections, more structural polygons in horizontal sections, and also more obvious ice lens segregation, unfrozen zone consolidation, and water migration during the freezing of soil samples. [ABSTRACT FROM AUTHOR]

An elastic foundation beam theory can be used to properly and effectively deal with the interaction between soil and structure. The theory application has also been gradually promoted in the frost-heaving mechanical analysis of frozen soil engineering structures in recent years. However, the existing Winkler model cannot consider the continuity of frozen soil. It is very necessary to presuppose the distribution of tangential freezing force. In this study, the governing differential equations were presented for the normal and tangential directions. The Pasternak shear layer was also introduced to connect the adjacent soil springs and contact interface layer between the frozen soil and concrete lining plate. Then, the frost-heaving mechanical model of the trapezoidal concrete lining canal was established using the two-parameter Pasternak elastic frozen soil foundation. The model was effectively connected with the SL23-2006“Specification for Design of Anti-freeze of Canal Engineering”. The frost-heaving mechanical analysis was applied to the concrete lining canals with the deep groundwater table. The computational accuracy of the frost-heaving mechanical model was improved significantly, where the shear layer was introduced to describe the interaction between the Winkler soil springs. The distribution of tangential freezing force was incorporated into the elastic foundation beam theory through the introduction of the contact interface layer. As such, there was no need for an improved model for the distribution of tangential freezing force. Taking the trapezoidal main canal of the Jinghui irrigation area in Gansu Province of China as the prototype, the improved model was applied to calculate the normal frost-heaving displacement of each point on the concrete lining plate. A comparison was then made on the Winkler model, the Finite Element Model (FEM) and test values. The comparative analysis indicated that there was consistent overall variation and tendency in the presented model, Winkler model, and FEM simulation. The critical test points were set on the concrete lining plates. The two-parameter elastic foundation beam model was much more consistent with the test values than those in the Winkler model and FEM. Furthermore, the two-parameter elastic foundation beam model was reduced to the Winkler model, when the shearing factor of frozen soil g was equal to 0. These results demonstrated the rationality and reliability of the presented model. The presented model was also applied to calculate the tangential displace and tangential freezing force of each section of the concrete lining plate. A parameter analysis was then carried out for the tangential contact stiffness. Among them, different tangential contact stiffness was set as the contact surface layer between concrete lining plates and frozen soil. Consequently, there was a nonlinear distribution in the section tangential displace and tangential freezing force along the concrete lining plates. A general decreasing trend was found in the tangential displace of each section with the increment of tangential contact stiffness. The distribution of tangential freezing force showed that “when one side is relatively large, then the other side is small”. In addition, there was a linear and uniform distribution of tangential freezing force, when the tangential contact stiffness was smaller. By contrast, the more nonlinear and non-uniform distribution was observed with the increase of tangential contact stiffness. The finding can provide a strong reference to designing the frost heave damage resistance of canals. [ABSTRACT FROM AUTHOR]