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Global warming is causing unprecedented changes to permafrost regions with amplified effects in the Arctic through a phenomenon known as Arctic amplification. This intensified climate warming thaws both the discontinuous and continuous permafrost resulting in changes in the mechanical properties of the soils found in these regions. Since permafrost regions constitute nearly 24% of the Northern Hemisphere, understanding the strength of soils in thawed conditions is essential to analyze the stability of existing structures, and to design safer and more economical infrastructure in these regions. Specifically, thawing of the permafrost is causing considerable reductions in its strength of soils, which may lead to massive landslides, foundation failures, and so forth. Since frozen soil is a multiphase structure that consists of soil particles, unfrozen water, ice, and air, each constituent will influence the mechanical properties. This paper reviews the current state of knowledge of the impact of temperature, volumetric ice content, unfrozen water content, and frozen density on the compressive strength, peak shear strength, residual shear strength, undrained shear strength, and tensile strength of soils. The undrained shear strength of soil is said to have a linear correlation with temperature. In addition, the undrained cohesion of soil was found to depend on the temperature, whereas the undrained friction angle of soil was significantly influenced by volumetric ice content. An increase in the volumetric ice content up to 80% to 90% will cause a reduction in the peak and residual deviatoric stresses. In addition, an increase in volumetric ice content resulted in an increase in the compressive strength of the soil. The tensile and compressive strengths were found to be functions of the unfrozen water content. Global warming is causing the temperature of the permafrost, which is permanently frozen ground, to rise. This paper provides valuable insights into the impact of the changes in this ambient temperature on the strength of frozen soils in permafrost regions for a wide range of applications. Such insights are crucial for the design of resilient and stable infrastructure, such as foundations, embankments, and retaining walls, in which consideration of the reduced strength of thawed soils due to climate change will be necessary. In addition, the knowledge will allow for better management of vulnerable areas prone to landslides and erosion caused by the weakened soil strength permitting the implementation of mitigation measures before lives are lost and costly economic damages are incurred. Finally, this information will aid in early warning systems, emergency planning, and decision making to minimize the impact of hazards on human settlements and infrastructure. In this paper, a review of the current state of knowledge regarding the strength of frozen soils and the associated fluctuations in these strengths because of a rise in temperature are presented. Guidelines on the best practices for sample preparation and testing along with correlations to estimate various strength parameters are also provided. [ABSTRACT FROM AUTHOR]

The application of existing gas transmission pipelines to deliver hydrogen-blended natural gas is the most operable method among many delivery methods. Hydrogen-blended natural gas with different hydrogen-blending ratios after passing through the throttling element is not the same. Using FLUENT to analyze the temperature variation after the Joule–Thomson effect for 0%, 5%, 10%, 20%, and 30% hydrogen mixing ratios. Workbench is used to analyze the soil temperature field around the pipeline and the stress displacement of the buried pipeline in the permafrost zone under different hydrogen mixing ratios. The analysis revealed that as the hydrogen mixing ratio increases, the temperature of the same point gradually increases after the Joule–Thomson effect, the low-temperature area around the buried pipe is gradually replaced by the high-temperature area, and the stress of the buried straight pipe also gradually decreases; while the maximum stress of the pipe initially decreases and then increases, and the displacement has no obvious change. Buried pipelines, which are generally accepted worldwide as one of the many forms of natural gas transmission, pass through permafrost areas during their laying, thus triggering freeze-ups and posing a potential hazard to the safe transportation of natural gas. Most of the existing methods to solve the frozen rise of buried pipelines in the permafrost zone have problems of high energy consumption and construction difficulties. Therefore, this paper, combined with the current trend of vigorous development of hydrogen-blending natural gas projects around the world, proposes a method to alleviate the purpose of freeze-ups by inputting a reasonable hydrogen-blending ratio before the regulator through the negative Joule–Thomson effect of hydrogen and using the phenomenon of temperature rise along the pipeline after the hydrogen passes through the regulator to neutralize the temperature drop of pure natural gas. In this paper, we applied finite element analysis software to simulate the effect of five mixing ratios of hydrogen gas, such as 0%, 5%, 10%, 20%, and 30%, on buried pipelines and also selected 0%–5% as the best mixing ratio to relieve freezing under the working conditions of the simulation environment. The feasibility of delivering hydrogen-blended natural gas at appropriate blending ratios to mitigate freeze-ups in buried pipelines in permafrost areas is demonstrated. It provides a new method for freeze-rise mitigation measures at gas transmission sites. [ABSTRACT FROM AUTHOR]

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]

This paper provides an outlook on the effects of climate change and the severity and frequency of extreme weather events on the performance of flexible pavements across North America. Now more than ever, the climate is changing at a rapid pace, which will alter long-term environmental loading parameters and extreme weather events. Such alterations will pose implications for the design, maintenance, and rehabilitation of flexible pavements, especially in terms of their serviceability, safety, and functionality. In northern Canada, roads are founded on various terrain types, including thaw-sensitive ice-rich permafrost underlying terrains. Such roads have experienced signs of embankment and pavement damage, which are usually induced by the degradation of the underlying permafrost due to climate change. Therefore, the development and implementation of new permafrost thaw mitigation techniques for vulnerable roads are essential and will be discussed in this paper. Resilient flexible roads should be designed to withstand the conditions that are likely to occur during their design life, taking into account the impact of the climate change on pavement performance in response to daily and seasonal changes in heat, precipitation, freeze–thaw cycles, and extreme weather events. [ABSTRACT FROM AUTHOR]

One of the main problems of wide expressway construction in permafrost regions involves protection of the thermal stability of roadbed. Although ventilating ducts and crushed-rock layers have been successfully used in railway embankment construction, their effects may fail to reach the requirements of large-width expressways. This paper proposes Convection-intensifying composite embankments composed of perforated ventilation ducts and crushed-rock layers and numerically studied their cooling effects. A numerical model for composite embankments in permafrost regions is established considering air flow and heat transfer characteristics in porous media. Temperature fields and cooling effects are simulated, and the results show that when the underlying permafrost temperature decreases, the position of the 0°C isotherm increases significantly. The installed position of the ventilation duct and the thickness of crushed-rock layer have a significant influence on thermal status of the underlying permafrost. The new convection-intensifying composite embankment is a potential cooling measure for high-grade, large-width highway construction in permafrost regions. [ABSTRACT FROM AUTHOR]

While the authors of current bridge management systems (BMSs) have noted the need for expanding the systems to include more functional aspects of bridge performance, to date no method has been proposed for the incorporation of bridge rating against climate change impacts. This paper presents a new procedure for extending the asset management scope for highway bridges to incorporate the bridges' resilience or vulnerability against climate change impacts. The proposed procedure draws from the projected demands of climate change--a worldwide phenomenon that is expected to produce its most dramatic impacts in cold regions. The following bridge resilience indicators are proposed: abutment washout, pier scour, abutment erosion, deck flooding, and abutment permafrost stability. The formulations for the proposed indicators require weights to be assigned to each indicator. The other requirement comprises capacity measures that indicate how well a bridge is equipped to withstand the projected climatic effects. The new procedure has been applied to 14 highway bridges in the Canadian Arctic to demonstrate how public investments in transportation infrastructure could be better managed and protected. The method comes with an Inspection Form that transportation agencies and their bridge inspectors can use for rating bridges on climate change resilience. [ABSTRACT FROM AUTHOR]

This paper presents a design approach to analyze the effects of lateral loads on piles embedded in a layered frozen soil profile. This design approach makes use of a commercially available computer program that uses p-y curves to model lateral pile loading and soil interaction. Shear strength and strain criteria for both fine-grained and coarse-grained frozen soil are presented for use in constructing p-y curves. These strength criteria are parameterized based on frozen soil temperature and load duration. Inuvik lateral pile load test measurements and deflections calculated using the strength criteria are compared. This comparison indicates that reducing shear strengths by a safety factor of 1.22 will ameliorate most unaccounted-for variations in soil profile. Deflections and moments are also calculated using the strength criteria for two Prudhoe Bay, Alaska, lateral pile load cases. [ABSTRACT FROM AUTHOR]

This paper reviews the effectiveness and costs of strategies to improve roadbed stability in permafrost regions, based on a synthesis of literature findings. Roadbeds in permafrost regions experience instability when the embankment loading and its heat absorption properties degrade the permafrost foundation. A variety of engineering strategies are used to mitigate this effect. The review summarizes the rationale, effectiveness, and costs of four types of strategies, namely those that control roadbed thawing, cool the roadbed, insulate the roadbed, and reduce roadbed fill weight. The literature reveals that strategies to control roadbed thawing, insulate the roadbed, or reduce roadbed fill weight do not reverse the long-term degradation of permafrost foundations. Strategies that cool the roadbed by implementing air convection embankments, ventilation ducts, thermosiphons, heat drains, or combinations of these are effective in reducing embankment temperatures and stabilizing the roadbed. Costs vary by geographic and climatic conditions and the proximity of materials to the construction site. Reported data suggest that conducting normal maintenance is less expensive than implementing roadbed cooling strategies, but maintaining serviceability may not be feasible. [ABSTRACT FROM AUTHOR]

Contamination of permafrost by hydrocarbons is an important issue in northern regions. In addition to harmful environmental impacts, diesel-fuel spills in permafrost associated with vehicle-storage areas, storage tanks, and pipelines can also lead to loss of strength of the frozen soils. Investigations of the reduction in strength of contaminated frozen soils have typically been restricted to salt contamination. However, the mechanical behavior of diesel-contaminated frozen soils may vary from that of salt-contaminated frozen soils. This paper presents the results of two series of unconfined uniaxial compression tests on artificial (laboratory produced) diesel-contaminated and uncontaminated frozen silty-soil specimens at two different temperatures ( and ). A total of 58 specimens were tested. The influence of total liquid content (water and diesel), density, freezing method, and amount of diesel contamination on the decrease in compressive strength of the specimens is examined. [ABSTRACT FROM AUTHOR]

This paper presents a design approach to analyze the effects of lateral loads on piles embedded in a layered frozen soil profile. This design approach makes use of a commercially available computer program that uses curves to model lateral pile loading and soil interaction. Shear strength and strain criteria for both fine- and coarse-grained frozen soil are presented for use in constructing curves. These strength criteria are parameterized based on frozen soil temperature and load duration. Inuvik lateral pile load test results and deflections calculated using the strength criteria are compared. Deflections and moments are also calculated using the strength criteria for two Prudhoe Bay, Alaska, lateral pile load cases. [ABSTRACT FROM AUTHOR]

In permafrost valleys, artesian wells often penetrate highly pressurized aquifers beneath confining subpermafrost. These wells must be quickly brought under control at installation, and heated through their operational life to prevent them from freezing in winter. However, water breakthrough of the permafrost barrier around the casing results in loss of control of the well. Seepage icing impacts to property and infrastructure can be catastrophic, and the costs to regain well control and mitigate damages high. Methods to regain control of artesian wells in permafrost are few and risky. A new method, cryogenic freezeback, was successfully used to mitigate an uncontrolled artesian well in a permafrost valley north of Fairbanks, Alaska. This paper documents the freezeback method, seepage and thermal analyses, and well abandonment and retrofit. Thermal monitoring results are presented to demonstrate the long-term effectiveness of the method. [ABSTRACT FROM AUTHOR]

This study formulates a heat flux boundary model to assess cold region ground temperatures and to distinguish the difference between this boundary type and a temperature boundary type. This formulation considers the impacts of the ground-surface albedo and of the environmental conditions (e.g., air temperature, wind speed, and solar radiation) on the ground-surface heat flux and subsequent subsurface temperature profiles. The predicted results are verified by the observed temperature profiles at a test station on the Qinghai-Tibet Plateau. A temperature boundary model is also used to simulate the ground temperature and is compared to the same field-observed temperature profiles. The paper speculates whether neglecting the evaporation-induced heat flux in the formulation of the heat flux boundary model compromises the ground temperature profile calculation. The effect of the evolution of the surface albedo on the redistribution of the ground temperature profiles is also discussed. [ABSTRACT FROM AUTHOR]

This paper reports on a case study of degrading permafrost beneath a road embankment in Northern Manitoba, Canada. Field measurements of ground temperatures for a three-year monitoring period have been used in calibrating the geothermal model developed to reproduce the conditions and trends in the subsurface thermal regime beneath the embankment. The numerical model was used to investigate the future ground thermal regime of the foundation and evaluate the potential impacts of embankment construction and climate change. Particular interest was paid to the foundation soil near the toe of embankment where relatively rapid permafrost degradation was occurring. [ABSTRACT FROM AUTHOR]

The Qinghai-Tibet railway, the highest railway in terms of elevation, was built under the harshest of weather conditions in the world. A new technique, called the ventiduct embankment, was used for the first time in railway construction in the Qinghai-Tibet permafrost region of China to overcome the specific difficulties of the permafrost plateau. To evaluate its effectiveness, several full-scale test embankments were constructed at a representative field site, the Qingshuihe experimental section. The effectiveness of the ventiduct embankment structure has been verified by comparing it with the performance of the nearby control embankment in terms of permafrost table, settlement, and thaw depth. These observations are presented in this paper. The ventiduct embankment structure based on this study has been adopted in Qinghai-Tibet permafrost railway construction. [ABSTRACT FROM AUTHOR]

This paper discusses the effect of route direction, embankment height, and pavement type on the thermal field of embankments built in permafrost regions. A finite-element model (FEM) is adopted to simulate diverse conditions of the embankment. The 30-year meteorological data including the solar radiation, air temperature, and wind velocity are used as the boundary conditions for the Qinghai-Tibet Highway. The results obtained from the FEM calculations are found to be in good agreement with the actual measurements on the thermal field. Further, the results show that route direction has great impact on the equilibrium of the thermal field within embankments in permafrost regions. The thermal imbalance is more obvious for embankments in the east–west direction and less in the north–south direction. In addition, the thermal asymmetry is closely related to seasonal variation and it is more pronounced in winter and less in summer. [ABSTRACT FROM AUTHOR]

This paper describes a study undertaken at Umiujaq, in northern Québec, on laterally loaded piles in permafrost subject to a constant displacement rate. Test results of bending moments, shear load, soil reaction, and pile displacements demonstrate the complex nature of creep of frozen soils. FEM simulations show a good concurrence with field test results and confirm a clear distinction between stationary and nonstationary creep. [ABSTRACT FROM AUTHOR]

With advances in the ability to model complex geothermal conditions, the aspect of soil structure interaction as it relates to long-term changes in the geothermal regime can be considered. Traditional geothermal modeling relied on the so-called -factor approach where the ground surface temperature was represented as the air temperature multiplied by some factor to account for ground surface effects. The application of surface energy balance formulations where the effects of the building including long wave radiation can be incorporated, allows for a more accurate representation of the geothermal regime under the structure. In considering the impact of climate warming on the performance of raised buildings in permafrost terrain, the use of a surface energy balance in the geothermal model is considered to be a more rigorous and technically preferable approach to addressing this problem. This paper addresses the use of a surface energy balance formulation in the geothermal analysis of raised buildings construction in permafrost terrain and its impact on the long-term geothermal regime. Specifically, the impact of building construction on the underlying geothermal regime have direct implication to the ongoing discussion regarding the need for climate change adaptation to address potential foundation capacity degradation in light of climate warming. Both existing field data and geothermal modeling results presented in this paper demonstrate that ground temperatures under a raised building cool over time and become colder than the ground remote from the building. When long-term climate warming is considered, the ground temperatures at depth do warm, but after 20 years of climate warming the ground temperatures under the building are still not warmer than the initial ground temperatures remote from the building. [ABSTRACT FROM AUTHOR]

Monitoring the soil freeze-thaw process is of great importance to engineering design of infrastructure, observation of hydrology, variation of climate, and existence of vegetation in cold regions. This paper presents experimental results to describe the soil freeze-thaw process using piezoceramic-based smart aggregate (SA) transducers. Two SAs are embedded in predetermined locations: one is used as the actuator and the other is used as a sensor. The active-sensing method is applied to excite a stress wave propagating between the two SAs. The alteration of the mechanical properties of the soil during the freeze-thaw process has an important effect on the stress-wave propagation, and the transition between the freeze and thaw states of the soil is monitored in real time. A wavelet packet-based soil freeze-thaw status indicator is established to quantitatively describe the soil status during the freeze-thaw process. Potentially, this freeze-thaw status indicator can be linked to soil mechanical properties, and therefore the methodology presented here can be used to characterize a partially frozen soil or warm permafrost site. [ABSTRACT FROM AUTHOR]