Thaw Settlement Research Articles

A Quantitative Graph-Based Approach to Monitoring Ice-Wedge Trough Dynamics in Polygonal Permafrost Landscapes

In response to increasing Arctic temperatures, ice-rich permafrost landscapes are undergoing rapid changes. In permafrost lowlands, polygonal ice wedges are especially prone to degradation. Melting of ice wedges results in deepening troughs and the transition from low-centered to high-centered ice-wedge polygons. This process has important implications for surface hydrology, as the connectivity of such troughs determines the rate of drainage for these lowland landscapes. In this study, we present a comprehensive, modular, and highly automated workflow to extract, to represent, and to analyze remotely sensed ice-wedge polygonal trough networks as a graph (i.e., network structure). With computer vision methods, we efficiently extract the trough locations as well as their geomorphometric information on trough depth and width from high-resolution digital elevation models and link these data within the graph. Further, we present and discuss the benefits of graph analysis algorithms for characterizing the erosional development of such thaw-affected landscapes. Based on our graph analysis, we show how thaw subsidence has progressed between 2009 and 2019 following burning at the Anaktuvuk River fire scar in northern Alaska, USA. We observed a considerable increase in the number of discernible troughs within the study area, while simultaneously the number of disconnected networks decreased from 54 small networks in 2009 to only six considerably larger disconnected networks in 2019. On average, the width of the troughs has increased by 13.86%, while the average depth has slightly decreased by 10.31%. Overall, our new automated approach allows for monitoring ice-wedge dynamics in unprecedented spatial detail, while simultaneously reducing the data to quantifiable geometric measures and spatial relationships.

Seasonal InSAR Displacements Documenting the Active Layer Freeze and Thaw Progression in Central-Western Spitsbergen, Svalbard

In permafrost areas, the active layer undergoes seasonal frost heave and thaw subsidence caused by ice formation and melting. The amplitude and timing of the ground displacement cycles depend on the climatic and ground conditions. Here we used Sentinel-1 Synthetic Aperture Radar Interferometry (InSAR) to document the seasonal displacement progression in three regions of Svalbard. We retrieved June–November 2017 time series and identified thaw subsidence maxima and their timing. InSAR measurements were compared with a composite index model based on ground surface temperature. Cyclic seasonal patterns are identified in all areas, but the timing of the displacement progression varies. The subsidence maxima occurred later on the warm western coast (Kapp Linné and Ny-Ålesund) compared to the colder interior (Adventdalen). The composite index model is generally able to explain the observed patterns. In Adventdalen, the model matches the InSAR time series at the location of the borehole. In Kapp Linné and Ny-Ålesund, larger deviations are found at the pixel-scale, but km or regional averaging improves the fit. The study highlights the potential for further development of regional InSAR products to represent the cyclic displacements in permafrost areas and infer the active layer thermal dynamics.

Validation of Permafrost Active Layer Estimates from Airborne SAR Observations

In permafrost regions, active layer thickness (ALT) observations measure the effects of climate change and predict hydrologic and elemental cycling. Often, ALT is measured through direct ground-based measurements. Recently, synthetic aperture radar (SAR) measurements from airborne platforms have emerged as a method for observing seasonal thaw subsidence, soil moisture, and ALT in permafrost regions. This study validates airborne SAR-derived ALT estimates in three regions of Alaska, USA using calibrated ground penetrating radar (GPR) geophysical data. The remotely sensed ALT estimates matched the field observations within uncertainty for 79% of locations. The average uncertainty for the GPR-derived ALT validation dataset was 0.14 m while the average uncertainty for the SAR-derived ALT in pixels coincident with GPR data was 0.19 m. In the region near Utqiaġvik, the remotely sensed ALT appeared slightly larger than field observations while in the Yukon-Kuskokwim Delta region, the remotely sensed ALT appeared slightly smaller than field observations. In the northern foothills of the Brooks Range, near Toolik Lake, there was minimal bias between the field data and remotely sensed estimates. These findings suggest that airborne SAR-derived ALT estimates compare well with in situ probing and GPR, making SAR an effective tool to monitor permafrost measurements.

Cool, CALM, collected: the Circumpolar Active Layer Monitoring program and network

ABSTRACT The Circumpolar Active Layer Monitoring (CALM) program is the primary global-change monitoring program concerned with the seasonally frozen active layer above permafrost. The active layer has been designated by the Global Climate Observing System and the Global Terrestrial Observing Network as an ‘Essential Climate Variable’. CALM was launched in 1991 on a volunteer basis in cooperation with the International Tundra Experiment. CALM observatories in Russia and Alaska have been supported since 1998 by the U.S. National Science Foundation through five consecutive five-year funding cycles. In its current configuration, the CALM network includes observation sites throughout the circum-Arctic region and a substantial number of sites in Antarctica. Open access to data and data harmonization are hallmarks of the program. In addition to its ongoing emphasis on field observations of active-layer thickness, temperature, soil moisture, and thaw subsidence are currently being monitored at many sites. Increased emphasis is being placed on observing the dynamics of other landscape and ecosystem parameters, including vegetation, landscape patterns, and soils. Other developing features of the program include expanded education and outreach activities, close cooperation with other international programs, and provision of quality-controlled, standardized data products that meet the needs of the wider scientific community.

Long-term Circumpolar Active Layer Monitoring (CALM) program observations in Northern Alaskan tundra

ABSTRACT The Circumpolar Active Layer Monitoring (CALM) network is an ongoing international effort to collect and disseminate standardized measurements of active-layer dynamics to monitor the response of near-surface permafrost parameters to climate change. This work presents a distillation of 25 years (1995–2019) of observations from three north–south transects of CALM sites in tundra environments of Alaska. Transects examined in this work bisect tundra regions of discontinuous permafrost on the Seward Peninsula, and the continuous permafrost zone on the western and eastern sections of the Arctic Foothills and Arctic Coastal Plain. These transects represent regional climatic gradients, several physiographic provinces, and regionally characteristic landcover associations. Total active-layer thickening at observed sites ranged from 7 to 26 cm; more significant thaw occurred in the foothills despite less pronounced warming air temperature trends. This summary highlights several regional active layer responses to climate warming, complicated by distinct thermal landscape sensitivities, landscape variability, and documented thaw subsidence. Data summarized in this report are publicly available and represent an important validation resource for earth-system models that include regions in the continuous and discontinuous permafrost zones of northern and western Alaska.

Centrifuge modelling of gas pipelines undergoing freeze–thaw cycles

Frost heave and thaw settlement are two critical factors that need to be considered in the design of chilled gas pipelines in cold regions. Due to the variation in seasonal temperature and operating conditions (e.g., pressure and temperature at the compressor stations), the pipeline temperature in some segments might vary from subzero to above zero during winter and summer, respectively. This study examines the freezing and thawing for cyclic and constant temperatures at the pipeline and ground surfaces based on the response of 14 model pipes tested in a geotechnical centrifuge. The cyclic (temperature) operation reduces the frost heave rate per year and causes net settlement in some cases. When the thaw bulb resulting from an above-zero operating temperature is less than the previously developed frost bulb, upward water flow occurs through the thawed soil, which could alter the pipeline–soil interaction behaviour. Five types of freeze-thaw-induced vertical displacement of the pipe have been identified from the centrifuge test results.

Ground temperature and deformation characteristics of anti-freeze-thaw embankments in permafrost and seasonal frozen ground regions of China

Embankment engineering in cold regions are at risk of seasonal freeze-thaw damage which seriously threatens the safe operation of vehicles. To ensure the long-term stability of embankment engineering in these areas, novel anti-freeze-thaw measures with differential filling materials should be taken. This study first analyzes the thermal-deformation characteristics and effects of two typical railway embankments with differential anti-freeze-thaw filling materials in permafrost and seasonal frozen ground regions based on ground temperature and deformation monitoring data. Then, on the basis of these results and previous research, the similarities and differences between the thermal-deformation characteristics of different embankments in permafrost and seasonal frozen ground regions are studied. Finally, the study summarizes fundamental principles for anti-freeze-thaw embankment measures in accordance with frozen ground type. Results demonstrate that: 1) the thaw settlement of permafrost embankments demonstrates persistence and is non-uniform, while the frost heave of embankments in seasonal frozen ground regions demonstrates cold shrinkage and heave delay; 2) understanding the development of the temperature and thickness of the seasonal thawing/freezing layer in time and space is key for preventing freeze-thaw damage in frozen ground regions; 3) the long-term stability of embankments in permafrost regions can be maintained by controlling the quantity of cold entrance and diffusion. For embankments in seasonal frozen ground regions, frost heave may be controlled by changing the property, water content, and temperature of filling materials. These findings will be helpful for better understanding the thermal-mechanical characteristics of embankments in different frozen ground regions, and for providing important technical guidance to ensure the operational efficiency of engineering projects.

Snow Patches and Their Influence on Coastal Erosion at Baydaratskaya Bay Coast, Kara Sea, Russian Arctic

The Arctic coastal environment is a very dynamic system and sensitive to any changes. In our research we demonstrate that nivation (snow patch activity) impacts the Arctic landscape especially in the coastal dynamic at the western part of Russian Arctic. During fieldwork, snowbanks were described and studied and their qualitative role in the development of coastal systems was revealed for Baydaratskaya Bay coast, the Kara Sea. On one side, the large snow cover protects the coastal slope from thermodenudation and thermoabrasion; on the other side, a thick layer of snow affects the ground temperature regime. During snow melting, snow patches contribute to the removal of material from the coastal slope. The quantitative effect of snow on the ground temperature regime was assessed according to numerical simulations. The critical snow thickness was determined based on a calculation. Critical snow thicknesses based on simulation and field data correlated well. The numerical simulation showed the talik formation under the snow patch. Talik size essentially depends on the freezing temperature of sediment (influenced by salinity). The changes of ground temperature regime might further generate thawing settlement of sediment under snow and contribute to beach topography, which might be a trigger for thermoabrasion.

Laboratory study and predictive modeling for thaw subsidence in deep permafrost

Laboratory study and predictive modeling for thaw subsidence in deep permafrost

Thermal gradient–dependent fracture behavior of ice-rich frozen soils

Fractures in frozen soils are strongly associated with thermal gradient–dependent heterogeneity and significantly affect frost heaving and thaw subsidence in permafrost by altering the soil structure and the moisture migration path. An experimental study was conducted to investigate the quantitative relationship between fracture behavior and stress-induced heterogeneity of frozen soils with a thermal gradient. A series of visualization-aided unconfined compression tests on frozen soil columns with a thermal gradient under various water contents and temperatures was performed. The results indicated that the influences of water content and temperature on the observed fracture can be unified into an heterogeneity level. An increase in the heterogeneity level weakened the peak strength and enhanced the volumetric dilation of the frozen samples. The strain localization zone was the main location for fracture initiation and development, and its range accounted for over 70% of the fracture. The height of the fracture reduced with stress-induced heterogeneity level increased, while its reducing rate was over 2 times more than that of the maximum lateral deformation and strain localization zone. A mean asymmetry coefficient over 1.2 in the heterogeneity level observed at the two sides of the frozen specimens was attributed to the occurrence and change in location of the shear fracture. These observations and findings have significant importance for development of a fracture model that incorporates the influences of stress-induced heterogeneity in frozen soils with a thermal gradient to improve the mathematical formulations on frost heave.

A study on frost heave and thaw settlement of soil subjected to cyclic freeze-thaw conditions based on hydro-thermal-mechanical coupling analysis

Frost heave and thaw settlement are the main cause for damaging the engineering structures in the region of seasonally frozen soil. The soil freeze-thaw (FT) deformation is a typical complex result of multiple physical fields and involves the process of water transfer, heat transfer, ice-water phase transition and stress redistribution. While the theory and model of frost heave have been studied for decades, less attention has been paid to the simulation for soil deformation under FT cycles. In this study, coupled equations for water, heat and the deformation of frozen soil are derived based on previous theories and are realized in numerical software. The volumetric water content of the frozen soil in the experiment was tested by nuclear magnetic resonance (NMR) technology, and the obtained data were imported into the model. Experimental soil samples were arranged in improved model equipment, and the temperature and frost heave at different heights of the soil column varied with time. The model validity and applicability based on the hydro-thermal-mechanical coupled equations is verified by comparing the results of both the experiment and numerical simulation. In this research, from the curves of the soil temperature change, water content distribution, water flux occurred at the soil bottom surface, as well as the displacement of frost heave and thaw settlement, and the pore size distribution, the characteristics of the soil subjected to cyclic FT conditions was analyzed. The existed theoretical model cannot well model the soil FT deformation. Therefore, this study may provide references for developing more accurate theoretical models on the soil subjected to FT cycles.

Nonlinear Analysis of the Thaw Settlement in Ice-Rich Embankments

In this paper, the law of ice-rich permafrost embankment thaw consolidation is studied based on three-dimensional nonlinear large strain thaw consolidation theory. To avoid problems associated with numerical simulation efficiency and stability when a nonlinear stress-strain relationship is employed, a segment interpolation function is used to implement the nonlinear relationship between the compression modulus and the void ratio, and the corresponding simulation strategy is proposed. Through a comparison of the monitoring and calculated results, it is indicated that the calculation accuracy on ice-rich embankment thaw settlement can be notably improved after nonlinear theory is implemented with the proposed numerical simulation method. A further analysis of the calculated results indicates that the interactive effects between the thermal and mechanical fields can be more reasonably described by nonlinear theory than by linear theory. It is also determined that the postthaw pore water in the shallow embankment dissipates in the early operation period, while in the following long operation period, the development of the permafrost embankment thaw settlement is mainly due to the dissipation of newly postthaw pore water at the thaw depth or the permafrost table. This is one of the main differences in the law of permafrost embankment thaw settlement compared with that of unfrozen embankments.

Permafrost thaw and ground settlement considering long-term climate impact in northern Alaska

Alaska’s North Slope is predicted to experience twice the warming expected globally. When summers are longer and winters are shortened, ground surface conditions in the Arctic are expected to change considerably. This is significant for Arctic Alaska, a region that supports surface infrastructure such as energy extraction and transport assets (pipelines), buildings, roadways, and bridges. Climatic change at the ground surface has been shown to impact soil layers beneath through the harmonic fluctuation of the active layer, and warmer air temperature can result in progressive permafrost thaw, leading to a deeper active layer. This study attempts to assess climate change based on the climate model data from the fifth phase of the Coupled Model Intercomparison Project and its impact on a permafrost environment in Northern Alaska. The predicted air temperature data are analyzed to evaluate how the freezing and thawing indices will change due to climate warming. A thermal model was developed that incorporated a ground surface condition defined by either undisturbed intact tundra or a gravel fill surface and applied climate model predicted air temperatures. Results indicate similar fluctuation in active layer thickness and values that fall within the range of minimum and maximum readings for the last quarter-century. It is found that the active layer thickness increases, with the amount depending on climate model predictions and ground surface conditions. These variations in active layer thickness are then analyzed by considering the near-surface frozen soil ice content. Analysis of results indicates that thaw strain is most significant in the near-surface layers, indicating that settlement would be concurrent with annual thaw penetration. Moreover, ice content is a major factor in the settlement prediction. This assessment methodology, after improvement, and the results can help enhance the resilience of the existing and future new infrastructure in a changing Arctic environment.

Long‐term field measurements of climate‐induced thaw subsidence above ice wedges on hillslopes, western Arctic Canada

AbstractNear‐surface wedges of massive ice commonly outline polygons in tundra lowlands, but such polygons have been difficult to identify on hillslopes because soil movement flattens the ridges and infills the troughs that form beside and above the ice wedges. Over the past three decades, the active layer has thickened near the western Arctic coast of Canada and consequent thawing of ice wedges has been detected by remote sensing for flat terrain but not, generally, on hillslopes. Annual field surveys (1996–2018) at the Illisarvik field site of thaw depth and ground surface elevation show the mean subsidence rate above hillslope ice wedges has been up to 32 mm a−1 since thaw depth reached the ice‐wedge tops in 2007. Annual mean ground temperatures at the site are about −3.0°C beneath late‐winter snow depths characteristic of the ice‐wedge troughs but about −5.3°C under conditions of the intervening polygons. The rate of thaw subsidence is high for natural, subaerial disturbances because meltwater from the ice wedges runs off downslope. The rate is constant, because the thickness of seasonally thawed ground above the ice wedges and the ice content of the ground remain the same while the troughs develop. Observations of changes in surface elevation in northern Banks Island between the late 1970s and 2019 show troughs on hillslopes where none was previously visible. Development of these troughs creates regional thermokarst landscapes, distinct from the widely recognized results of thawing relict glacier ice, that are now widespread over Canada's western Arctic coastlands. Recognition of ice‐wedge occurrence and accelerated thaw subsidence on hillslopes is important in the design of infrastructure proposed for construction in rolling permafrost terrain.

Mathematical Model and Numerical Simulation of hydrothermal Coupling for Unsaturated Soil Subgrade in the Seasonal Frozen Zone

The subgrade in the seasonal frozen zone is easy to induce uneven settlement, frost heave and thaw settlement under the action of environmental factors such as precipitation, evaporation, radiation, etc. The subgrade is mostly unsaturated soil. In non-saline soil areas, its diseases are mostly related to moisture migration and phase change in the soil. In order to study the moisture migration and temperature distribution of the unsaturated soil subgrade in the seasonal frozen zone, a hydrothermal coupling mathematical model was established. Based on the mathematical model, the hydrothermal coupling numerical simulation was carried out by using the COMSOL Multiphyscis finite element program, Given the basic parameters and variables, the model was solved by assigning the same initial and boundary conditions as the field test, and the simulation results were compared with the field test results to obtain very satisfactory temperature simulation results and a good fit between the moisture migration results and the field test values, proving the reliability of the mathematical model.

Application of the Frozen and Unfrozen Soil model to modelling effects of freeze-thaw on low-volume roads

Freezing and thawing of soils are of the utmost importance in the design of infrastructure in seasonally cold regions. Cycles of freezing-thawing can severely affect the performance of thinly paved low-volume roads, causing frost heave during the winter and thaw weakening in the spring. Thus, a designer must have an understanding of freezing effects on infrastructure and adequate design tools to deal with them. Freezing of soils entails several coupled processes, necessitating advanced analysis tools such as numerical modelling. This paper applies the Frozen and Unfrozen Soil material model for the finite element program Plaxis 2D into a case study of freezing and thawing induced deformation of a low-volume road on dry-crust clay subgrade in Vesilahti, Finland supported by a literature review and a laboratory study. The Vesilahti test site monitoring results of frost heave, temperature and groundwater level were used in this study to simulate the frost heave of a pavement with shallow structural layers. In addition, soil sampling and laboratory tests were performed to determine the Vesilahti dry-crust clay material properties at the Aalto University. These were combined to simulate the frost heave and thaw settlement measured on the site and to study the feasibility of the material model in replicating actual measured frost action. The road deformation at the measurement times was replicated qualitatively well and the model performed mostly according to expectations. However, the multitude of parameters, complexity of the coupled phenomena modelled and the black box nature of the model implementation in Plaxis make the evaluation of calculation errors tough and time-consuming. Further research on the model could include the implementation of various user-friendly improvements in Plaxis, development of cryogenic suction-and temperature-controlled laboratory testing for the model parameter determination and better utilization of the model’s predictive capabilities by studying continuous frost heave measurements.

Water and salt migration mechanisms of saturated chloride clay during freeze-thaw in an open system

Water and salt migration mechanisms are of great significance for understanding the frost heave and thaw settlement of saline soils during freeze-thaw (F-T). In this study, unidirectional open-system F-T tests were conducted on saturated clay specimens with various chloride salt contents to investigate water and salt migration mechanisms. Relevant parameters, including temperature, unfrozen water content, bulk electrical conductivity, matric suction, and water intake volume, were measured continuously during testing. Besides, the water molecule mobility was obtained by the Nuclear Magnetic Resonance relaxometry tests to help understand the water and salt migration mechanisms. The test results indicated that the freezing front development was highly dependent on salt content. The matric suction gradient was found to be the driving force of water-salt migration, which was larger in specimens with lower salt content and led to more water intake. The migration of water and salt was asynchronous due to their different driving mechanisms during F-T. Specifically, salt migration was affected by both convection and diffusion, while water migration was primarily driven by convection. This phenomenon was also confirmed by the different patterns in water and salt redistributions after F-T. Meanwhile, pore water in the frozen specimens with different salinity and the same unfrozen water content was found to have the same water molecule mobility. Both the matric suction and water molecule mobility were dependent on unfrozen water content but independent on salt content. However, the salt content has a significant effect on the soil freezing point depression, which further affects the matric suction and water molecule mobility.

Frost Heave and Thawing Settlement of Frozen Soils around Concrete Piles: A Laboratory Model Test

Abstract The frost heave and thawing settlement of soils around piles could cause a series of problems, such as freezing of the pile and reduced bearing capacity of the pile. Based on the soil profiles recorded at a permafrost region in Western China, laboratory tests were performed to investigate the frost heave and thawing settlement of frozen soils around piles. The ambient temperature was adjusted in such way that the thawing and freezing of soils occurred from top to bottom, respectively. As the thawing and freezing reached different depths, the temperature, unfrozen water content, and displacements of soils around eight piles were recorded. The results showed that when the thawing was completed, the unfrozen water content of soil located at a distance equal to the pile’s diameter measured from its face was larger than that of the soil located at a distance equal to triple the pile diameters. At the end of freezing, the unfrozen water content of the soil located at a distance equal to the pile’s diameter (from the pile’s face) was smaller than that of the soil located farther (triple pile diameters). It was also shown that for the soil region between 1 and 2 times the pile diameters from its face, the amount of thawing settlement and frost heave increases, while the magnitude of the soil thawing settlement and frost heave decreases from 2 to 3 times the pile diameters. The laboratory results also showed that the difference in the frost heave and thawing settlement is related to the difference of the performance of heat transfer between the pile and soil during the freezing process. Therefore, a transverse temperature gradient exists in the pile-soil system, causing the unfrozen water to migrate toward the pile–soil interface and freeze.

The Effect of Ceramsite Replacement Ratio on Frost-Heave Deformation of Power Transmission and Transformation Foundation in Extreme Condition

Under the impact of frost heave and thaw settlement of seasonal frozen soil, freezing pulling and horizontal tilt of piles often occurs. Aim to the above problems, this paper proposed a material using ceramsite replacement concrete as the foundation to reduce heat exchange with atmosphere. The results showed that when the replacement rate of ceramsite is 80%, the density of the blocks is 1896 kg/m3, which is 19.3% lower than that of plain concrete. Also, the addition of ceramsite significantly reduced the thermal conductivity of concrete. The minimum thermal conductivity of tested blocks is 0.524 W/(m.K), which is 58.6% lower than that of ordinary concrete. Meanwhile, the strength of concrete decreased the addition of ceramsite. When the replacement rate is 80%, the compressive strength and splitting tensile strength are 18.1 and 2.7 MPa, respectively, which are 54.7% and 42.6% lower than that of plain concrete. Taking the climatic environment in the Hexi area as the boundary conditions, a numerical simulation on the design and optimization of the thickness of the insulation system was carried out. It was found that the installation of 2 m insulation concrete can effectively increase the temperature of the soil in extreme environments and avoid frost heave.

Temperature Field Distribution and Thermal Stability of Roadbed in Permafrost Regions

Many highways and railways in western China are built on permafrost roadbed. Frost heave and thaw settlement might cause diseases to frozen soil roadbed, such as deformation and cracking. For long-term operation, frozen soil roadbed should be kept stable and durable. Therefore, this paper analyzes the distribution law of temperature field of roadbed in permafrost regions, under the effect of thermal stability. Based on the thermodynamic properties of permafrost, the authors analyzed the influence of engineering geological factors, roadbed structural factors, and natural environmental factors on the thermal stability of frozen soil roadbed. Next, the antifreeze mechanism of frozen soil roadbed was described, together with the calculation methods for the relevant parameters. Afterwards, the temperature field of the roadbed with low thermal conductivity insulation material was analyzed by two methods, namely, steady-state thermal analysis and transient thermal analysis, and the solving process of roadbed temperature field was explained in details. The proposed analysis method and solving algorithm were proved valid through experiments. The research results provide a reference for the reasonable design of frozen soil roadbed.