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 elasto-plastic dynamic response of tunnels surrounded by frozen soil under loads applied to the tunnel invert is investigated in this study. Special attention is paid to the frozen soil in plastic zones around the tunnel in cold regions where anisotropic frost heave occurs. Analytical solutions of displacement and stress distributions in the lining, plastic zone of frozen soil, elastic zone of frozen soil, and unfrozen soil layer under load are derived. Unknown parameters are determined by satisfying continuity and boundary conditions between contact surfaces of different media. The parametric analysis reveals that the radial and circumferential stresses experience the most significant decrease in the plastic zone and at the contact surfaces of different media. The thickness of the frozen soil layer, along with the development of its plastic zone, influences the dynamic response of the frozen soil around the tunnel. Furthermore, variations in soil and lining parameters also have an impact on stress and displacement distributions in each medium. The findings of this study aim to provide valuable insights for the numerical simulation, design, and construction of future tunnels in cold regions.

Global climate change and permafrost degradation have significantly heightened the risk of geological hazards in high-altitude cold regions, resulting in severe casualties and property damage, particularly in the Qinghai-Tibet Plateau of China. To mitigate the risk of geological disasters, it is crucial to identify the primary disaster-inducing factors. Therefore, to address this issue more effectively, this study proposes a spatiotemporal-scale approach for detecting disaster-inducing factors and investigates the disaster-inducing factors of geological hazards in high-altitude cold regions, using the Kanchenjunga Basin as a case study. As the world's third-highest peak, Kanchenjunga is highly sensitive to climate fluctuations. This study first integrates the frost heave model and multitemporal interferometric synthetic aperture radar techniques to monitor ascending and descending track line-of-sight deformation of the frozen active layer in the study area. Subsequently, the surface parallel flow constrained model is employed to decompose the 3-D time-series deformation of geological hazards in the basin, with remote sensing imagery and field surveys used to identify a total of 94 disaster sites. In parallel, a database of potential conditioning factors is constructed by leveraging Google Earth Engine remote sensing inversion technology and relevant data provided by the China Geological Survey. Finally, by integrating monitoring results with a database of potential geological conditioning factors, the spatiotemporal-scale approach for detecting disaster-inducing factors proposed in this study is applied to investigate the disaster-inducing factors in the Kanchenjunga Basin. The research results highlight that surface temperature is the primary driving factor of geological hazards in the Kanchenjunga Basin. This research helps bridge the data gap in the region and offers critical support for local government decision-making in disaster prevention, risk assessment, and related areas.

There is 78 % permafrost and seasonal frozen soil in the Yangtze River's Source Region (SRYR), which is situated in the middle of the Qinghai-Xizang Plateau. Three distinct scenarios were developed in the Soil and Water Assessment Tool (SWAT) to model the effects of land cover change (LCC) on various water balance components. Discharge and percolation of groundwater have decreased by mid-December. This demonstrates the seasonal contributions of subsurface water, which diminish when soil freezes. During winter, when surface water inputs are low, groundwater storage becomes even more critical to ensure water supply due to this periodic trend. An impermeable layer underneath the active layer thickness decreases GWQ and PERC in LCC + permafrost scenario. The water transport and storage phase reached a critical point in August when precipitation, permafrost thawing, and snowmelt caused LATQ to surge. To prevent waterlogging and save water for dry periods, it is necessary to control this peak flow phase. Hydrological processes, permafrost dynamics, and land cover changes in the SRYR are difficult, according to the data. These interactions enhance water circulation throughout the year, recharge of groundwater supplies, surface runoff, and lateral flow. For the region's water resource management to be effective in sustaining ecohydrology, ensuring appropriate water storage, and alleviating freshwater scarcity, these dynamics must be considered.

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.

The stability of soil is an essential requirement for various geotechnical engineering projects. The application of composite materials made from cemented soil has become prevalent in road subgrade engineering and foundation treatment due to their affordability, quick construction, and ability to withstand high compression forces. However, the mechanism about the incorporating fibers into cemented soil to enhance strength characteristics, mitigate the formation of microcracks in the soil matrix, and increase frost resistance is still unclear. In this study, a composite improvement method of adding basalt fiber (BF) to cemented soil is proposed, which is to select a single subgrade filling material with most significant freeze-thaw (FT) durability on the basis of traditional cement improvement methods. A series of static/dynamic triaxial compression tests were performed with cemented soil samples reinforced by three BF contents (0, 0.25%, 0.50%, and 0.75%) after FT cycles. The physical properties of these samples were studied, such as the optimal ratio of fiber content, the stress-strain relationship, failure strength, shear strength, and shear modulus, among others. The results revealed that both the shear modulus and failure strength of cemented subgrade soil reinforced with BF showed a significant increase. Compared with cemented soil, fiber-cemented soil exhibited a lower reduction rate in its mechanical properties after 15 FT cycles. The cohesion of the reinforced soil exhibited a gradual decrease as the number of FT cycles increased. Conversely, the friction angle initially decreased but later exhibited an increase. Compared with the reinforcement effects of BF at 0.25% and 0.75%, fiber-reinforced cemented soil with BF content of 0.5% demonstrated the highest strength and performed well in minimizing the effect of FT cycles. It is therefore recommended that ratio of 6% cement and 0.5% BF should be used to enhance the integrity of subgrade filling materials on silty clay.

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.