Impact from falling objects can easily cause the local deformation of pipeline, which threatens the safe and stable operation of pipeline. In order to study the dynamic response behavior of impacted buried pipelines in cold regions, the buried pipelines, frozen soil and falling objects are taken as the object. Considering the nonlinearity of pipeline material, the contact nonlinearity between pipeline, falling objects and frozen soil, a double nonlinear dynamic analysis model of buried pipeline in cold regions is established by explicit dynamic analysis method. The rationality of the model method is verified by comparing the curves in this paper with those from the experiment. Furthermore, the changing laws of dynamic response of pipeline influenced by different factors are discussed. The results show that: when the buried depth of pipeline is 2 m, the deformation and residual stress of pipeline increase with the increase of pipeline's diameter-tothickness ratio, the impact velocity of falling object and the water content of frozen soil, and the impact velocity of falling objects influences the dynamic response behavior of pipelines most significantly, followed by the diameter-thickness ratio of pipelines and the water content of frozen soil; When the diameter-thickness ratio of the pipeline is 58, the deformation and residual stress of pipeline decrease with the increase of buried depth by 75 % and 88 % respectively. Among the four influencing factors, when the impact velocity of falling objects is 10 m/s and the buried depth of pipeline is 3 m, the deformation amplitude of pipelines caused by falling objects is the smallest. It is suggested that in the high-risk regions of falling objects, the diameter-thickness ratio, buried depth and the water content of frozen soil can be reasonably controlled under the condition of predicting the maximum potential impact velocity of falling objects, so as to improve the ability of the pipeline to resist external impact damage, which provides theoretical basis and quantitative control standards for the impact design of pipeline engineering in cold regions.

Heating method shows considerable potential for mitigating frost heave of subgrade in cold regions. However, the water-heat-deformation characteristics of subgrade under the coupling effect of freezing-thawing and heating effect remain unclear, which hampers the optimization and widespread application of heating method. Therefore, this paper proposes a numerical model of subgrade water-heat-deformation considering heating effect. The influence and mechanism of heating effect on water-heat-deformation of subgrade is systematically analyzed. The results show that the heating effect changes the water-heat-deformation state of subgrade. Furthermore, the combined influence of shady-sunny slope effect and ballast layer ensures that ground temperature near the subgrade center remains above 0 degrees C, thereby preventing the formation of ice lenses and frost heave. However, the shoulders on both sides enter a freezing state, and freezing rate, freezing depth and frost heave are reduced by more than 45 %, 60 % and 60 % respectively compared with the comparison subgrade. The freezing depth, driving force and rate of water migration are significantly affected by heating effect, which increases the pathways of water upward migration and greatly weakens the segregated frost heave of subgrade. This is the primary mechanism through which the heating method effectively mitigates frost heave in subgrades.

The lining and surrounding rock around tunnels constructed in cold areas exhibit nonuniform material properties due to the existence of a temperature field. This study considered the effects of these properties on the integrity of tunnel structures. By establishing an elastoplastic mechanical model, analytical solutions to the stress and displacement under five different elastoplastic states were derived and compared based on distinct yield criteria. The findings showed that with increasing relative radius, the displacement in the lining elastic zone initially decreased before increasing, whereas the shift in the plastic zone continued to increase. The displacement in the elastic zone of the frozen surrounding rock intensified with increasing relative radius, whereas the shift in the plastic zone experienced a gradual decline. The displacement of the inner wall of the lining was always greater than that of the outer wall, and this phenomenon occurred only after the frozen surrounding rock exhibited a plastic zone. The maximum displacements of the liner in its elastically limited and plastically limited states were 1.39, 1.77, 2.28, and 2.37 mm and 15.93, 25.51, 44.28, and 48.58 mm based on the Drucker-Prager (DP), Mohr-Coulomb (MC), Tresca, and double-shear strength criteria, respectively; the maximum limit displacements of the frozen surrounding rock were 12.74, 20.41, 35.43, and 38.87 mm and 85.32, 103.38, 569.23, and 680.43 mm, respectively. With increasing relative radius, the radial stresses within both the lining and the frozen surrounding rock intensified; and the tangential stress in the elastic zone of the lining decreased whereas the opposite change rule was observed in the plastic zone. The tangential stresses in the frozen surrounding rock and lining exhibited the same variation trend. Based on calculations with four distinct strength criteria, the elastic and plastic ultimate bearing capacities of the lining were 1.81, 2.31, 2.95, and 3.07 MPa, and 3.31, 4.84, 7.48, and 8.05 MPa, while those of the frozen surrounding rock were 8.52, 13.24, 22.17, and 24.18 MPa, and 16.76, 32.46, 74.15, and 85.64 MPa. In addition, with the expansion of the plastic zone, the phenomenon of a sudden change in the tangential stress at location r2 became progressively attenuated. The study findings can provide some theoretical guidance for the design and construction of tunnels in cold areas.

Accurately quantifying the impact of permafrost degradation and soil freeze-thaw cycles on hydrological processes while minimizing the reliance on observational data are challenging issues in hydrological modeling in cold regions. In this study, we developed a modular distributed hydro-thermal coupled hydrological model for cold regions (DHTC) that features a flexible structure. The DHTC model couples heat-water transport processes by employing the conduction-advection heat transport equation and Richard equation considering ice-water phase change. Additionally, the DHTC model integrates the influence of organic matter into the hydrothermal parameterization scheme and includes a subpermafrost module based on the flow duration curve analysis to estimate cold-season streamflow sustained by subpermafrost groundwater. Moreover, we incorporated energy consumption due to ice phase changes to the available energy, enhancing the accuracy of evaporation estimation in cold regions. A comprehensive evaluation of the DHTC model was conducted. At the point scale, the DHTC model accurately replicates daily soil temperature and moisture dynamics at various depths, achieving average R-2 of 0.98 and 0.87, and average RMSE of 0.61degree celsius and 0.03 m(3)m(-3), respectively. At the basin scale, DHTC outperformed (Daily: R-2 = 0.66, RMSE = 0.75 mm; Monthly: R-2 = 0.90, RMSE = 15.7 mm) the GLDAS/FLDAS Noah, GLDAS/VIC, and PML-V2 models in evapotranspiration simulation. The DHTC model also demonstrated reasonable performance in simulating daily (NSE = 0.70, KGE = 0.84), monthly (NSE = 0.86, KGE = 0.90), and multi-year monthly (NSE = 0.97, KGE = 0.93) streamflow in the Source Regions of Yangtze River. DHTC also successfully reproduced the snow depth in basin-averaged time series and spatial distributions (RMSE = 0.86 cm). The DHTC model provides a robust tool for exploring the interactions between permafrost and hydrological processes, and their responses to climate change.

The risk of geohazards associated with frozen subgrades is well recognized, but a comprehensive framework to evaluate frost susceptibility from microstructural characteristics to macroscopic thermo-hydro-mechanical (THM) behaviors has not been established. This study aims to propose a simple framework for quantitatively assessing frost susceptibility and compressibility in frozen soils. A systematic THM model was devised to predict heat transfer, soil freezing characteristics, and stress states in frozen soils. Constant freezing experiments and oedometer compression tests were performed on bentonite clays under varying temperatures (-5 degrees C, -10 degrees C, and -20 degrees C) and stress levels to validate the proposed model. Additionally, soil electrical conductivity measurements were employed to assess the temperature- and stress-dependent volumetric and mechanical properties of frozen soils. The model used Fourier's law to compute the transient soil temperature profile and estimated the volume change and stress states based on the soil freezing characteristic curve. Experimental results showed that frost heave of bentonite reached between 9.0% and 26.6% of axial strain, which was largely predicted by the proposed model. It also demonstrated that the frost heave was mainly attributed to the fusion of the porewater. Additionally, the preconsolidation pressure of frozen soils exhibited a rapid increasing trend with decreasing temperature, which was explained by the temperature-dependent ice morphology in the soil interpore. Furthermore, the findings also demonstrated a remarkable sensitivity in the electrical conductivity in response to the soil temperature during the frost heave process and the stress state under the loading or unloading path.

In cold regions, the freezing and thawing of embankments often cause significant damage to road surfaces. Research indicates that this freeze-thaw process is closely related to the distribution of temperature and moisture within the embankment. Therefore, an in-depth study of the moisture and temperature conditions and the resulting deformation under freeze-thaw effects is fundamental for analyzing crack-related diseases inAroad surfaces. The authors have developed a monitoring system for moisture and temperature in cold region highway embankments to conduct long-term observations. Based on the collected data, the distribution patterns of moisture and temperature fields in the embankment were analyzed. The results indicate that temperature changes at different locations within the embankment generally correspond to atmospheric temperature changes, exhibiting a periodic sinusoidal pattern. The annual variation in embankment temperature shows a nonlinear negative correlation with depth.

A growing rock engineering activity in cold regions is facing the threat of freeze-thaw (FT) weathering, especially in high mountains where the sunny-shady slope effects strongly control the difference in weathering behavior of rocks. In this paper, an investigation of the degradation of petrophysical characteristics of sandstone specimens subjected to FT cycle tests to simulate the sunny-shady slope effects is presented. To this aim, non-destructive and repeatable testing techniques including weight, ultrasonic waves, and nuclear magnetic resonance methods on standard specimens were performed. For the sunny slope specimens, accompanied by the enlargement of small pores, 100 FT cycles caused a significant decrease in P-wave velocity with an average of 23%, but a consistent rise of 0.18% in mass loss, 34% in porosity, 67% in pore geometrical mean radius, and a remarkable 14.5-fold increase in permeability. However, slight changes with some abnormal trends in physical parameters of the shady slope specimens were observed during FT cycling, which can be attributed to superficial granular disaggregation and pore throat obstruction. Thermal shocks enhance rock weathering on sunny slopes during FT cycles, while FT weathering on shady slopes is restricted to the small pores and the superficial cover. These two factors are primarily responsible for the differences in FT weathering intensity between sunny and shady slopes. The conclusions derived from the interpretation of the experimental results may provide theoretical guidance for the design of slope-failure prevention measures and the selection of transportation routes in cold mountainous regions. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Climate warming is causing significant changes in the Arctic, leading to increased temperatures and permafrost instability. The active layer has been shown to be affected by climate change, where warmer ground surface temperatures result in progressive permafrost thaw and a deepening active layer. This study assessed the effects of thermal modeling parameters on permafrost ground response to climate warming using the fifth phase of the Coupled Model Intercomparison Project (CMIP5) and TEMP/W software. We analyzed how variations in depth, water content, and soil type affect predictions of future active layer depths and settlement under various climate scenarios using the soil characteristics along Hudson Bay Railway corridor. The results indicate that, for finegrained soils, the depth of the model is a more significant parameter than for coarse-grained soils. The water content of all soil types is a critical factor in determining the time at which permafrost thaws and the depth at which the active layer is located, as higher water content leads to larger active layer changes and more settlement in most cases. Our findings have important implications for infrastructure and land use management in the Arctic region.

The principle of effective stress is widely recognized as the cornerstone of soil mechanics, with its application extending beyond soils to other porous materials such as rocks and concrete. In recent decades, there has been a significant surge in scientific research and engineering practice in cold regions, where the classical framework of effective stress in soil mechanics is frequently invoked. However, there is no consensus either on mathematical expressions or especially on the physical nature of effective stress in a soil when ice is involved. This paper starts from Terzaghi's principle of effective stress for saturated soils, and subsequently Bishop's work for unsaturated soils and the Clapeyron equation for phase change are introduced as the basis for further discussions. Focus is laid on a comprehensive analysis on formulas for effective stress with respect to cold regions geotechnical engineering. Two categories are classified, in which the effective stress is considered to be undertaken by soil skeleton only and by soil skeleton-ice system together, respectively. They may generate calculated results that can efficiently interpret experiments or observations, while both are rather speculative and faced with major challenges. Controversies on effective stress for unfrozen soils are analyzed with respect to cold regions geotechnical engineering. It is recognized hardly possible to develop a mechanism-based principle of effective stress based on the current understandings, while it is questionable to develop it based on that for unfrozen soils. Two potential approaches are suggested that might be applicable for cold regions geotechnical engineering.

Roadway and railway embankments in seasonally changing climates, i.e., where freeze and thaw cycles are likely to occur, are prone to different kinds of foundation and structural damage. This includes accelerating consolidation rate, soil stiffness reduction, and permafrost damage in permafrost regions. As it is vital to maintain the safety and serviceability of embankments, several risk mitigation measures are adopted to maintain the integrity of the foundation soils and embankment bodies. These measures include, but are not limited to, thermosyphons, air convection sections, and increasing albedo. As climate change impacts are further maximized, especially in cold regions with high seasonal temperature variability, new strategies need to be developed to cope with these changes. Some of these strategies are geared toward providing minimal intervention with the climate change process so as to minimize the resources allocated to preserving the current conditions while maintaining the resilience of infrastructures. In this paper, we present a systematic review of the current state of practice of embankments built in seasonally changing climates. In addition, we discuss the outstanding challenges pertaining to fundamental understanding and modeling tools of thermal-mechanical interactions. Finally, we discuss some of the implications of climate change impacts on embankment design and possible risk mitigation measures.