Thaw Penetration Research Articles

Research on the Preparation and Performance of Biomimetic Warm-Mix Regeneration for Asphalt Mixtures

To determine the formula for biomimetic warm-mix regeneration and fulfill the requirements of a “high waste asphalt mixture content, high quality, and high level” for its usage in reclaimed asphalt pavement (RAP), this paper first determined the suitable preparation process and formula for biomimetic warm-mix regeneration based on orthogonal experiments and a gray correlation analysis. Then, the optimum dosage of the warm-mix regenerant was determined by a uniaxial penetration test, low-temperature splitting test, and freeze–thaw penetration test. The rutting test was conducted to characterize the high-temperature performance of the asphalt mixture. The Immersion Marshall Test and the freeze–thaw splitting test were used to characterize the water stability of the recycled asphalt mixture. The low-temperature small beam test was employed to study the low-temperature performance of the recycled asphalt mixture. The asphalt’s short-term and long-term aging processes were simulated using the rotary thin-film oven test (RTFOT) and the pressure aging test (PAV). The action mechanism of biomimetic warm-mix regeneration was revealed by Fourier-transform infrared spectroscopy (FTIR). Finally, a comprehensive thermal performance test was conducted on the aged asphalt after biomimetic warm-mix regeneration. The results showed that the self-made biomimetic warm-mix regeneration agent exhibited an excellent regenerative effect on RAP and significantly reduced the mixing temperature of the styrene–butadiene–styrene (SBS)-modified asphalt mixture. In addition, the self-made biomimetic warm-mix regeneration agent effectively improved the high- and low-temperature performance of the recycled asphalt mixture, but had no noticeable effect on the water stability. The suggested dosage of the biomimetic warm-mix regeneration agent was 6%, and the mixing temperature was 130 °C. The microscopic chemical analysis revealed that biomimetic warm-mix regeneration restored the performance of aged asphalt by supplementing the light component. The change rules of the chemical functional groups and the comprehensive thermal properties of the recycled mixture showed a good correlation with the change rules of its high- and low-temperature performance.

Widespread Permafrost Degradation and Thaw Subsidence in Northwest Canada

AbstractLong‐term (1991–2018) thaw tube measurements highlight widespread permafrost thaw and ground surface (GS) subsidence over a large portion of northwest Canada. Statistically significant positive trends in thaw penetration (TP), measured with respect to a fixed datum, were observed at 18 of 28 sites with data that span three decades at a median rate of 0.8 cm a−1. This rate implies thawing of about 22 cm of permafrost over the study period. Similarly significant trends in GS subsidence occurred at 21 of 28 sites, at a median rate of 0.4 cm a−1. In contrast with TP and GS elevation, long‐term trends in active layer thickness (ALT) were less consistent, with 10 of 28 sites having statistically significant trends indicating increasing ALT (median rate: 0.6 cm a−1), and 7 sites having trends indicating decrease in ALT (median: 0.3 cm a−1). The ALT measurements underestimated the thawing of ice‐rich permafrost due to GS subsidence. Sites with high rates of thaw had relatively warm permafrost, deep snow cover, and poor drainage. Masking of ice‐rich permafrost degradation by ALT measurements has important implications for modeling permafrost thaw and climate change reporting. Accurate simulation of ice‐rich permafrost thaw is conceivable for sites where conditions are well‐defined. However, the prediction of subsidence and TP at regional or broader scales is only possible in general terms due to variation in surface conditions and ground ice content. Trends in TP and GS subsidence more accurately characterize ice‐rich permafrost degradation than trends in ALT.

Climate Change Impacts on Frost and Thaw Considerations: Case Study of Airport Pavement Design in Canada

Rising temperatures due to climate change can significantly impact the freeze–thaw condition of airport pavements in cold regions. This case study investigates the implications of warming temperatures on the freeze–thaw penetration and frost heave of pavements in critical airports across Canada. To this end, different methods were used in the quantification process through climate change simulations considering emission scenario RCP8.5 in 20 and 40 year time horizons. The results show that climate change would have different design implications for airport pavements, depending on their location. The predictions suggest a shallower frost penetration depth, and possibly less frost heave, for the airports not underlain by permafrost, while airports over permafrost areas might experience an increase in thickness of the active layer, ranging from 41 to 57 percent, by 2061. Among the different methods used in this study, it was observed that some methods performed better in predicting the frost depth of fine soils, while others worked better in the frost depth prediction of coarse soils. The results indicate the need for more mechanistic models to provide a more realistic prediction of freeze–thaw penetration, as compared to existing empirical models.

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.

Spatial and temporal freeze-thaw variations in Alaskan roads

Seasonal freeze and thaw impact a road’s ability to bear loads. Temperature index models are one of the methods being used to manage seasonal weight restrictions on roads. Many of these methods are limited to specific regions in which they have been calibrated and more universally applicable models are sought. We conducted a multi-year study of road subsurface temperature data in Alaska to understand temperature variations among stations and support the development of generally applicable models. Time-stability analysis showed that stations located within 25 km had consistent temperatures with the consistency increasing with measurement depth. At greater separation distances, stations’ relative cold or warm biases were maintained across years. Up to 95% of temperature differences among stations was explained by latitude when linear regression was used. Temperature time series showed distinct isothermal conditions in spring at temperature below 0 oC. For stations located further south, thaw penetration rates were greater, and surface n-Factors varied more. A constant thawing index was also tested to determine thaw dates. Thaw depths corresponding to these dates were relatively consistent for northern stations but varied substantially for southern stations.

One-dimensional large-strain thaw consolidation using nonlinear effective stress – void ratio – hydraulic conductivity relationships

A one-dimensional model for the consolidation of thawing soils is formulated in terms of large-strain consolidation and heat-transfer equations. The model integrates heat transfer due to conduction, phase change, and advection. The hydromechanical behaviour is modelled by large-strain consolidation theory. The equations are coupled in a moving boundary scheme developed in Lagrangian coordinates. Finite strains are allowed and nonlinear effective stress – void ratio – hydraulic conductivity relationships are proposed to characterize the thawing soil properties. Initial conditions and boundary conditions are presented with special consideration for the moving boundary condition at the thaw front developed in terms of large-strain consolidation. The proposed model is applied and compared with small-strain thaw consolidation theory in a theoretical working example of a thawing fine-grained soil sample. The modelling results are presented in terms of temperature, thaw penetration, settlements, void ratio, and excess pore-water pressures.

Analysis of thermal regime under riverbank in permafrost region

A riverbank was constructed on ice-rich permafrost in the far north of China in 2015, and its performance is closely related to the thermal stability of the permafrost foundation. To investigate the thermal regime evolution of the foundation, a numerical simulation using a coupled hydro-thermal model that involves concrete hydration, heat transfer by conduction and convection is performed over 20years in this paper. The monitored ground temperatures help confirm the accuracy of the simulation. A dramatic thaw penetration in the permafrost foundation is anticipated in the future under current geological and structural conditions. Moreover, this paper highlights the importance of concrete hydration, backfilled soil temperature, seepage and the mean annual ground temperature in effecting the geothermal evolution. These discussions suggest a requirement for some measures in construction and maintenance of hydraulic structures over permafrost.

Thaw Subsidence in Undisturbed Tundra Landscapes, Barrow, Alaska, 1962–2015

AbstractIn some regions underlain by ice‐rich permafrost, a consistent, long‐term increase in ALT under changing climatic conditions is not supported by observations. The apparent lack of ALT may be attributed to soil consolidation from thawing of the uppermost ice‐rich permafrost and subsidence of the ground surface. Four plots established in 1962 at Barrow, Alaska, were re‐instrumented in 2003 and surveyed annually using differential GPS technology, accompanied by active‐layer probing. Elevation change from 1962 to 2003 was within the interannual variability of the 2003–15 period, indicating net stability in the area. Over the 2003–15 period, however, all four plots experienced subsidence trends of 0.4–1.0 cm/year, resulting in a net elevation change of 8–15 cm. Warmer winters and increased snow depth during this period decreased the potential for frost heave. Warmer summers resulted in thaw penetration into the ice‐rich transient layer and ice wedges, leading to the net subsidence in recent years. Copyright © 2016 John Wiley & Sons, Ltd.

Thaw Penetration in Frozen Ground Subjected to Hydronic Heating

Acknowledgments This study is funded by Nordland County council, the ColdTech project (RT4-01), and Heatwork AS. The authors are grateful for the support in establishing the Frost in Ground laboratory (FiG-lab) and the access to the facilities during this work. The authors also thank Heatwork AS for providing the defrosting system used during the experiments.

Thermal performance of a combined cooling method of thermosyphons and insulation boards for tower foundation soils along the Qinghai–Tibet Power Transmission Line

Preliminary field observations along the Qinghai–Tibet Power Transmission Line (QTPTL) show that foundation soils of some shallow footings (with an embedding depth of 3.7m) with thermosyphons in permafrost regions still suffer substantial and rapid thaw settlement in warm seasons. In this paper, a series of numerical simulations on the long-term thermal performance of foundation soils of these shallow footings are carried out. The simulated results show that thermosyphons could do effectively cool foundation soils at depths 2.5 to 8.0m under the footing. However, in warm season from mid-May to mid-October, the rapid warming of shallow foundation soils near the footing caused by heat transfer through the concrete footing could not be prevented. The maximum thaw around the footing could be as much as 1.0m deeper than that in the natural ground. Under a warming climate, the maximum thaw around the footing would go deeper than the embedding depth of the footing with four thermosyphons in very warm (≥−0.5°C) permafrost regions and with two thermosyphons in warm (≥−1.0°C) permafrost regions during a 50-year operational period. To retard thaw penetration around the footing, a combined cooling method of thermosyphons and insulation boards is proposed for foundation soils. Numerically simulated results show that the additional placement of the boards on ground surface could prevent the rapid warming of shallow foundation soils and effectively reduce the maximum thaw around the footing. The method could also effectively delay permafrost warming under the footing. Thus, it is recommended to be used at shallow footings in very warm, ice-rich permafrost regions along the QTPTL.

Spatiotemporal characteristics of freezing and thawing of the active layer in the source areas of the Yellow River (SAYR)

Based on the analysis of data on temperatures and moisture of soils in the active layer at four different permafrost sites in the source areas of the Yellow River (SAYR) in 2010–2012, the freeze–thaw processes of soils in the active layer were compared and contrasted for understanding the spatiotemporal variations. At the four studied sites, the thickness and mean annual temperature of permafrost are different. The temperatures at the top of permafrost (TTOP), i.e., the maximum depth(s) of seasonal frost and/or thaw penetration, are −1.9 °C at the Chalaping site (CLP), −0.9 °C at the site on the southern bank of the Zhaling Lake (ZLH), −0.4 °C at the Maduo Town site (MDX), and 1.1 °C at the site on the northern bank of the Eling Lake (ELH). Differences in the mean annual ground temperature of permafrost and TTOPs may be responsible for the differentiations in the freeze–thaw processes of soils in the active layer. With rising TTOPs, the ground thawing started earlier: CLP in early June, ZLH in late May, MDX in early May, and ELH in mid-April, while the freezing began later: CLP in early October, ZLH in early to mid-October, MDX in mid-October, and ELH in the mid- to late October. With increasing TTOPs, the freeze-up periods for permafrost sites were shortened: 202 days at CLP, 130 days at ZLH, 100 days at MDX, and the period of complete thaw was 89 days at ELH. At the CLP and ZLH sites, the two-directional ground freezing (downwards from ground surfaces and upwards from the permafrost table) and thawing finished in the same year, but the ground freezing at the MDX continued to the end of the next January, with very slow freezing rates in the end. At the ELH site, ground freezing kept on until early May when thawing began on the surface, and upward and downward thawing became increasingly stable in late June to early July. At each site, with rising TTOPs, the downward freezing accelerated in comparison with the upward freezing, and with an increasing proportion of downward frozen depth, and with the larger ratios of freezing to thawing duration. In summary, the patterns of thawing and freezing processes in the active layer in the SAYR differ from those in other parts of the Qinghai–Tibet Plateau to a noticeable extent.

Implementation of Decision Support System (DSS) through the Integration of Commercial Remote Sensing (CRS), Model-View-Controller (MVC) Architecture and Object-Relational Mapping (ORM)

order to aid in the processes of data collection, interpolation, analysis, and predictive model development the integration of commercial remote sensing and spatial information technologies (CRS&SI) with object oriented modeling (OOM) using the model view controller architecture (MVC) has been applied. A Decision Support System (DSS) application that uses CRS&SI for collecting atmospheric, subsurface, and predicted weather data, is used to compare, interpolate, measure, predict, and determines the depth of frost and thaw penetration into the subsurface of roadways across New England, This process is used in order to guide State Departments of Transportation (DOT) in determining when to impose Seasonal Load Restrictions (SLR). Seasonal load restrictions limit the travel of heavy trucks on certain roads such that state DOT's can limit the damage to the roadway surface. The implemented DSS consists of a web based front end graphical user interface (GUI) that leverages popular web based technologies, programming interfaces, data collection scripts, data evaluation scripts, data interpolation scripts, predictive modeling, and a centralized database. The database was developed for storing newly collected, historic, and predicted data. This paper includes the description of the general purpose and use of the system and a discussion regarding the architecture, individual components, interactions, and a description of the sequence of events for data collection, processing, prediction, and interpolation.

Permafrost studies in northern Québec

In cooperation with mining companies, temperature data are being acquired at several sites in the Cape Smith — Wakeham Bay Belt of Northern Québec. Cables, containing up to twenty thermistors, are lowered into exploratory diamond-drill holes upon completion, and allowed to freeze in place. Three temperature profiles at Asbestos Hill yield low geothermal gradients; thermal conductivities of core are moderate to low and hence low values of the terrestrial heat flow are observed. Extrapolating temperature profiles to greater depths gives a permafrost thickness of at least 540 m. The uncorrected terrestrial heat fluxes calculated for the shallow holes are about 2/3 that of the lower section of the deeper hole. Such contrast in heat flow is used to develop a simple model of surface temperature history for the area for the past 85 000 years. Using this geothermal data, engineering estimates may be made of such parameters as maximum active layer thickness and thaw penetration of both open pit walls and underground drifts.

Modelling the thermal response of permafrost terrain to right-of-way disturbance and climate warming

Field observations from a permafrost thermal monitoring network in the Norman Wells pipeline corridor Northwest Territories, and thermal modelling have been utilized to gain insights into the relative effects that both environmental disturbance associated with vegetation clearance and ongoing climate warming have on the ground thermal regime in the vicinity of a right-of-way (ROW). This analysis was conducted to generate information that may aid engineering design of northern development projects, the assessment of environmental impacts associated with these projects and the development of related environmental monitoring and management plans. The separate and combined effects of environmental disturbance and climate change on the ground thermal regime beneath and adjacent to a ROW in an area of discontinuous permafrost are investigated using a two-dimensional finite element thermal model. A simplified soil profile consisting of one metre of peat overlying a fine-grained mineral soil is considered. A limited set of scenarios consider the effect of: ROW clearing alone; ROW clearing followed by vegetation recovery; ROW clearing combined with climate warming of 0.5 °C per decade; and ROW clearing followed by vegetation recovery combined with climate warming. Simulation results for warm thin permafrost (mean annual ground temperature above − 1 °C; 20 m thick) indicate that the combined effects of ROW disturbance and climate warming are likely to result in permafrost degradation within 20 to 40 years, and ROW-disturbance effects may extend off-ROW under scenarios of climate warming. In colder and thicker permafrost (mean annual ground temperature below − 1 °C; 50 m thick), the combined effect of climate warming and ROW disturbance will not likely lead to talik formation within 50 years, although seasonal thaw penetration will increase. For the range in ground thermal conditions considered, the results of the simulations indicate that the effects of ROW disturbance outweigh those associated with climate warming in the initial 10 to 15 years following disturbance, although climate warming becomes important over longer time periods. Climate warming and its influence on the ground thermal regime should therefore be incorporated into the design of northern development projects (and assessment of associated environmental impacts) expected to operate over two decades or more and where ground instability associated with permafrost thawing is a concern.

Simulating Active Layer Thaw in a Boreal Environment

A large part of the boreal zone of the western Canadian Arctic is underlain by ice-rich discontinuous permafrost which when thawed, can lead to settlement of the ground surface that has implications for the integrity of northern infrastructure, including oil and gas pipelines. A simple yet physically-based model is desired to simulate thawing of the active layer in different materials commonly found along the Mackenzie Valley pipeline corridor. Stefan’s algorithm determines the phase change of soil moisture using ground surface temperature as the upper boundary condition and conduction to transfer heat to the freeze-thaw front. It is tested on a permafrost site near Wrigley, Northwest Territories, where the computed thaw penetration compares satisfactorily with field data. To further explore the effects of climate and soil types on active layer depth, three representative sites in the Mackenzie valley where ground surface temperatures are available were selected for simulation of ground thaw, under two summer conditions. Results of the simulation demonstrate the sensitivity of active layer thaw to (1) soil materials due to differential thermal properties, (2) moisture content, which largely controls the latent heat requirement for phase change, and (3) inter-annual variations in ground surface temperature. Given the strong potential for environmental changes in the vast boreal region, the model allows the active layer thaw responses to be easily assessed.

Climate warming and active layer thaw in the boreal and tundra environments of the Mackenzie Valley

The variability of maximum active layer thickness in boreal and tundra environments has important implications for hydrological processes, terrestrial and aquatic ecosystems, and the integrity of northern infrastructure. For most planning and management purposes, the long-term probability distribution of active layer thickness is of primary interest. A robust method is presented to calculate maximum active layer thickness, employing the Stefan equation to compute phase change of moisture in soils and using air temperature as the sole climatic forcing variable. Near-surface ground temperatures (boundary condition for the Stefan equation) were estimated based on empirical relationships established for several sites in the Mackenzie valley. Simulations were performed for typically saturated mineral soils, overlain with varying thickness of peat in boreal and tundra environments. The probability distributions of simulated maximum active layer thickness encompass the range of measured thaw depths provided by field data. The effects of climate warming under A2 and B2 scenarios for 2050 and 2100 were investigated. Under the A2 scenario in 2100, the simulated median thaw depth under a thin organic cover may increase by 0.3 m, to reach 1 m depth for a tundra site and 1.6 m depth for a boreal site. The median thaw depth in 2100 is dampened by about 50% under a 1 m thick organic layer. Without an insulating organic cover, thaw penetration can increase to reach 1.7 m at the tundra site. The simulations provide quantitative support that future thaw penetration in permafrost terrain will deepen differentially depending on location and soil.

Canadian cryospheric response to an anomalous warm summer: A synthesis of the climate change action fund project “the state of the arctic cryosphere during the extreme warm summer of 1998”

As of 2003, the warmest year on record in Canada (and globally) was 1998. Extensive warming was observed over the Canadian Arctic during the summer of 1998. A collaborative, interdisciplinary project involving government, universities, and the private sector examined the effect of this unusual warmth on cryospheric conditions and documented the responses, placing them in a 30–40 year context. This paper represents a synthesis of these results. 1998 was characterized by a melt season of exceptional length, having both an unusually early start and late finish. Extremes were noted for cryospheric variables that included ground thaw penetration, snow‐free season, lake‐ice‐free season, glacier melt, and the duration and extent of marine open water. The warm conditions contributed to the break‐up of two long‐term, multi‐year ice plugs in the north‐west Canadian Arctic Archipelago, which allowed floe ice into the Northwest Passage. Synoptic events and preconditioning were observed to play an important role in governing the response of some variables to the warming. It was also noted that response was not uniform in all regions. This study provided an opportunity to examine possible cryospheric response to future, warmer conditions. It also provided a chance to assess the capability of current cryospheric monitoring networks in the Canadian Arctic. This study has suggested the manner of cryospheric response to low frequency, high magnitude events occurring within the broader milieu of large‐scale forcing.

Numerical Modeling of Thaw Penetration in Frozen Ground Subject to Low-Intensity Infrared Heating

This research investigated the efficacy of low-intensity, radiant, infrared heating for inducing thawing in frozen ground. Specifically, the performance characteristics of a 22 kW infrared tube heater were evaluated. A commercial building site in Park City, Utah, was instrumented with thermocouple piers for field testing over a period of approximately 5 days. The experimental data were used to calibrate a numerical model of the infrared heating process, and several numerical simulations were then performed. The simulations facilitated evaluation of the effects of radiation intensity, air temperature, and ice content on thaw penetration rates achieved using infrared heating. While ice content has a marked influence on thaw penetration rates in all the simulations, the air temperature becomes less important with increasing infrared radiation intensity. The results of the testing also indicate that the tube heater exhibits a steady reduction in emitted radiation between propane tank exchanges and that the he...

Temporal and spatial variations in periglacial soil movements on alpine crest slopes

AbstractThis paper describes up to ten years of continuous monitoring of frost heave, creep and associated parameters on high mountain crest slopes in the Japanese and Swiss Alps, aiming to evaluate spatial and interannual variations in the rates and controls of soil movement. Shallow frost creep reflecting diurnal frost heave activity dominates the crest slopes that lack a vegetation mat and have a thin debris mantle with good drainage. Seasonal frost heave activity can induce slightly deeper movement where fine soil exists below the depth reached by diurnal freeze–thaw penetration, although the shallow bedrock impedes movements below 20 cm depth. As a result, downslope velocity profiles display strong concavity with surface velocities of 2–50 cm a−1. The frost creep rates vary spatially, depending on the soil texture, slope gradient, frequency of temperature cycling across 0 °C and moisture availability during freeze–thaw periods. Soil movements recur in every freeze–thaw period, although with some interannual variations affected by the length of seasonal snow cover and the occurrence of precipitation during freeze–thaw periods. The Swiss Alps encounter more significant interannual variations than the Japanese Alps, reflecting the large variability of the annual snow regime. Copyright © 2005 John Wiley & Sons, Ltd.

Relations between air and surface temperature in discontinuous permafrost terrain near Mayo, Yukon Territory

The association of site characteristics with the n-factor, a ratio of air to ground surface temperature, was investigated at five sites in the boreal forest near Mayo, Yukon Territory. Permafrost was in equilibrium with surface conditions at three sites, was degrading at another, and was absent from the fifth. Air and near-surface ground temperatures were recorded by data loggers between September 2000 and April 2002, and mean daily temperatures were accumulated to calculate n-factors for the freezing (nf) and thawing (nt) seasons. Air temperature did not vary between the sites, so inter-site differences in nf and nt were because of variations in surface temperature. Variations in nf between the sites over the two winters were primarily because of differences in snow depth, but at sites with similar snow cover, the surface temperatures were relatively high when the site was underlain by unfrozen ground. During summer, daily mean surface temperatures were initially less than air temperatures. However, once the thawing front had penetrated below the depth of diurnal temperature fluctuation, the air and ground surface temperatures converged. Since the rate of thaw penetration is governed by soil thermal diffusivity, nt varies directly with this property. These results indicate that subsurface conditions, particularly absolute temperature and ground thermal properties, exert considerable influence on n-factors, and, at the Mayo sites, the influence is greater than that of the vegetation.