Cold Regions Engineering 2019

Frozen soils can withstand heavy vehicle loads and provide major maneuver corridors in locations where the soils are otherwise too weak to support the loading conditions. Vehicle mobility models require input of the ground conditions to assess seasonal traffickability. Increasingly, measured air temperatures from weather station locations are becoming more widespread, however they lack a global gridded coverage. Similarly, ground profile measurements, such as soil temperature and moisture, are significant inputs to estimate depths of frost. New data products, such as gridded reanalysis data provides weather and soil data on a gridded global scale. This study compared frost depths determined from measured soil temperatures at stations in North Dakota and Minnesota with frost depths determined from soil temperatures from NASA’s Modern Era Retrospective Analysis for Research Application Version 2 (MERRA-2). The objectives of the study were to evaluate the usefulness of the MERRA-2 data to provide estimates of frost depth, and to determine the accuracy of estimated frost depths from modelling using either measured air temperatures or reanalysis air temperature data. To estimate the maximum frost depth a one-dimensional decoupled heat and moisture flow model was used. Differences in estimated frost depth resulted from modelling when compared to the measured soil temperatures. These differences are likely due to the influence of a snow layer. The properties of the snow layer play an important role in estimating the depth of frost. Improved material properties of the snow layer are needed to more accurately estimate the depth of ground freezing.

Effective and efficient mapping of permafrost subsurface composition at scales relevant to the design and maintenance of horizontal and vertical infrastructure has been a long-standing challenge. Of utmost utility would be the development of standoff measurement techniques that could discern at the meter to submeter spatial scale and up to 10 m into the subsurface the presence or absence of ice features. Ground-based geophysical measurement techniques, including ground penetrating radar, borehole logging, and electrical resistivity, have been used to interrogate the subsurface in permafrost terrains at the meter to kilometers scales. Airborne measurement techniques have broad applicability at the larger, kilometers to tens of kilometers scale and could support linear infrastructure development and terrain mapping. However, there is a broad need for cost effective airborne geophysical techniques to obtain high-resolution measurements of specific areas of interest. We present a frequency domain electromagnetic induction sensor weighing less than 10 pounds mounted on an unmanned aerial system capable of assessing the frozen state of soil to 10 m depth. We consider system design and motor interference as well as present a 3D model capable of identifying discrete ice inclusions on the order of 1 m in size.

Nunavik is a territory in Northern Quebec where 14 communities depend essentially on aerial transportation for their subsistence, economic development, and quality of life. Some airport runways built on permafrost in the late 80s showed worrying degradation signs only a few years after construction. The effect of runway embankments on the thermal regime at the embankment toes and where drainage is deficient, among other things, is well documented throughout the literature. These phenomena, as well as the general permafrost degradation, are amplified by climate changes, especially in northern regions. Because the permafrost degradation is worrying for transportation infrastructure, a project was undertaken to characterize the physical and mechanical properties of some permafrost soils in Northern Quebec, with the objective to assess their creep and thaw sensitivity. Frozen core samples were recovered at seven airstrips and two access roads, and undisturbed specimens were brought back to Laval University geotechnical laboratory. The samples from the most critical and representative study sites were subjected to basic geotechnical characterization along with triaxial creep. The creep tests allowed obtaining estimates of the creep rate for the soils at different deviatoric stress and temperatures. As for the thaw consolidation tests, they allowed estimating the settlements associated with a potential thawing of permafrost for various ice contents. The present paper focuses on the creep behavior. With the available ground thermal regimes and climate change scenarios, the results allow anticipating the thaw and creep settlements for some soils in Nunavik and can be used as part of a global adaptation strategy for infrastructure built on permafrost.

The previous laboratory study of joint electrical resistivity and acoustic velocity measurements is reviewed for both consolidated and unconsolidated permafrost in this paper. The relation of logarithm of resistivity log(R) and P-wave velocity V_p is a concave function. An increase of temperature, fine content, and salinity results in a decrease of both acoustic velocity and electrical resistivity. Electrical resistivity is sensitive to salinity, while acoustic velocity changes substantially near thawing temperature. The joint measurement results could be used to estimate unfrozen water saturation (UWS) based on Archie’s law, weighted equation (WE), or Kuster-Toksoz equations (KT). However, the estimated UWS from different methods is not always consistent. The difference can be up to 20%. It might be due to the fact that UWS is not the only parameter influencing the electrical and acoustic properties. In order to obtain consistent UWS, a joint model that combines the electrical effective medium theory (EMT) and the acoustic self-consistent approximation (SCA) is proposed. In this method, UWS and aspect ratio which describes particles shape are found simultaneously from the joint SCA-EMT model. Most of the results from the proposed method are between that of Archie’s law and WE method, which indicates that the electrical method might overestimate UWS and acoustic method might underestimate it.

An electrical resistivity and temperature piezocone penetration test (RTCPTu) was carried out in ice-rich permafrost near Umiujaq, Nunavik, Québec, Canada, to assess the permafrost cryostratigraphy. A penetrometer with temperature and piezometer sensors and electrical resistivity module was used for this RTCPTu. Signal processing of RTCPTu logs and forward modelling to simulate the response of the electrical resistivity module penetrating in ice-rich layered medium were performed to discriminate the ice lenses from the layers of frozen silt within permafrost. The cryostructure of permafrost, made of a complex sequence of ice lenses and layers of frozen silt, induces very noisy RTCPTu logs. Ice-rich permafrost is characterized by extremely variable values of cone resistance, friction ratio, pore pressure, and electrical resistivity. Based on the wavelet analysis of RTCPTu logs, the wavelengths of electrical resistivity are shorter than the ones of cone resistance, friction ratio, and pore pressure while all these sensors penetrated the same ice-rich layered medium. As found from forward modelling of the response of an electrical resistivity module penetrating in a resistive ice lens of different thicknesses embedded in conductive frozen silt, the variations in electrical resistivity as a function of depth are more complex than the ones of cone resistance, friction ratio, and pore pressure. This complex response is due to the four electrodes of the electrical resistivity module which are alternately in contact with the ice lens inducing complex electrical current flow and potential induction in this ice-rich layered medium. Knowing the simulated responses of the electrical resistivity module penetrating in ice-rich layered medium, the ice lenses, and layers of frozen silt in ice-rich permafrost were discriminated using cross-correlation between the electrical resistivity log and these simulated responses. Therefore, the cryostratigraphy of permafrost and ice content per penetrated linear meter of 42% were assessed from this RTCPTu.

The machining of ice-rich permafrost samples for thaw consolidation tests in an oedometer is challenging due to the heterogeneous mixtures of ice, soil, and small pebbles characteristics of frozen ground. During the machining, the discontinuities in a sample are critical planes of rupture that may lead to the loss of the sample due to cracking. In addition to the cutting shear, trimming with a lathe provokes additional mechanical stresses on the rotating sample. With the goal to carry out thaw consolidation tests on frozen ground samples, a new machining method was developed. Ice-rich permafrost samples were recovered with a portable drill in a permafrost mound at Umiujaq in Nunavik, Québec, Canada. They were kept frozen in an electrical freezer and transported back to the laboratory. In an environmental cold room at -15°C, the base of each core sample was immobilized and centered in a two-orthogonal-motion-axes sample holder on a vertical drill press. The machining device at the head of the drill press which rotates at a controlled speed of about forty rotations per minute is composed of four stages of pairs of high speed steel tool bits in opposition. The first two stages with bits at an angle of 45° relative to the motionless sample are for rough trimming while the last two stages of bits perpendicular to the sample are for finishing. With a motionless sample and a machining device in rotation, the rotational stresses in the sample and the cracking potential are greatly reduced. Several core samples of ice-rich permafrost in excess of 50% in volumetric ice content were successfully trimmed to the right size with this new machining method and driven in an oedometer for thaw consolidation tests.

In this paper, we present a numerical modelling approach that simulates the melting of an ice-filled rock discontinuity. Using a finite element model, we implement an ablation process to simulate the thawing of ice and removal of the resulting meltwater, assuming a well-drained system, under specific environmental conditions defined by appropriate boundary conditions. By extending an earlier version of an ablation model, we demonstrate the importance of the strength loss due to melting ice in a rock mass discontinuity that is influenced by convective and conductive heat transfer. The results from the numerical model provide input for analytically computing the tensile strength of the ice-rock interface to further characterize the strength of ice-filled discontinuities.

DC electrical resistivity tomography (ERT) is increasingly being used to delimit permafrost bodies, but a threshold value to differentiate between frozen and unfrozen ground is needed for data interpretation. Here we compare resistivities measured in peat and silts across a range of temperatures in both the field and the laboratory. ERT surveys were conducted at four sites with instrumented boreholes in the southern NWT (60.9–62.5°N). In the laboratory, remoulded soil samples were wetted to field moisture content, frozen in closed containers, and resistivity was measured across a range of temperatures during thaw. Between 0°C and -0.5°C, the resistivity of peat ranged from approximately 3,000–6,000 Ωm. For frozen silt, maximum resistivities were about 1,000 Ωm while the lowest was 85 Ωm, well below the value typically used to delimit permafrost. The relationship between resistivity and temperature allowed a two-dimensional temperature field to be generated from the tomograms, but predictions were not always consistent due to intra-site differences in moisture content and the presence or absence of segregated ice. This study illustrates the great range of resistivity values possible at temperatures close to 0°C, and demonstrates the importance of validating ERT results for warm permafrost.

Damage due to the frost penetration in soils can be detrimental to buried utilities such as water and gas pipes. It would not only reduce their service life but may also induce service interruptions and public safety concerns. Therefore, buried pipes should be located below the frost depth to prevent them from the frost damage. An alternative approach to protect buried utilities against frost damage and reduce the construction cost is to install insulations over and around the pipes. This paper aims to study the performance of the insulation materials with various geometries to prevent buried utilities from the frost damage in frost-susceptible soils. For this purpose, a comparative study is performed to determine the effect of phase change on the performance of the insulating foam with various geometries. Also, various geometries of insulation including horizontal, inverted U-shaped, and cylindrical insulations are modeled in order to present the best insulation configuration.

Crushed rock aggregates are widely used for transport infrastructure construction in Norway. During winters 2009/10 and 2010/11, differential frost heave severely affected the Norwegian transport network. Currently there is no system in the Norwegian road design to calculate expected frost heave from sub-grade and crushed rock aggregates. The segregation potential (SP) can be used to estimate heaving according to climatic data with the SSR model. Consequently, the frost protection of roads and railways project was created in part to improve knowledge about the frost susceptibility sensibility of crushed rock aggregates. The goals of this paper are to a) introduce the Norwegian University of Science and Technology (NTNU) freezing cell apparatus and laboratory methodology, b) present soil characterization and SP results of 7 different rock types, and c) discuss SP relationship with fine fraction content and mineralogy. A 150 mm diameter by 200 mm high multi-ring frost heave apparatus was used to perform the tests. Samples were frozen from top and hydraulic pressure other than cryosuction was avoided. Temperatures, heaving rate and magnitude, and water mass were recorded for the 96 hours duration of each test. A wide variety of rocks, including granitic gneiss, gneiss, anortosite, granodiorite, slate, gabbro, gneiss, and porphyr, was chosen. Fine fraction <63, <20, and <2 μm varies from 12.5% to 25.6%, 7.1% to 14.8%, and 0.53% to 2.45% respectively. The SPs varied from 60 to 197 mm²/°C·d. SP results are in accordance with value range showed by Konrad (2005), Konrad and Lemieux (2005), and Nurmikolu (2005) for granitic aggregates. SPs for the other rock type are proposed to be used as reference values. The SP as a function of fine content <2 μm calculated from the <80 μm fraction showed a trend of R²=0.84 for this study.

The Dempster Highway is the only all-season road connecting Canada’s western Arctic to the national highway network. Completed in 1979 it is built almost entirely on permafrost. Climate changes and infrastructure effects are expected to increase the temperature of permafrost near and beneath the road, resulting in increased active-layer thickness (ALT), drainage disruptions, and embankment subsidence. Four monitoring sites were established in 2014 to study such effects. Ground temperatures have been recorded along the highway at km 124 and 421 in Yukon and km 8.5 and 51.5 in NWT. Three boreholes up to 10 m depth were drilled at each site, to measure permafrost conditions at the highway centerline, embankment toe, and in undisturbed ground. The annual mean temperature at the top of permafrost (T_p) has been lowest beneath the centerline at each site (-1.5°C to -4.2°C), with the index decreasing northward. The active layer has thickened at each site, with only the centerline at km 124 in equilibrium. Ground temperatures at the centerline have fluctuated in response to changing air temperatures throughout the year due to clearing of snow from the highway. Degradation of permafrost at the toe has been the result of increased snow cover from ploughing and additional drifting. Thaw depths at the centerline of the NWT sites indicate permafrost initially aggraded within the embankment. The difference between T_p at the centerline and annual mean air temperature has decreased northwards, from 4.5°C at km 124 to 1.0°C at km 51.5; due to shorter freezeback periods at the NWT sites. The four years of measurements provide a baseline against which future changes may be assessed.

Measuring properties of frozen soil and snow in cold environments is an important problem in science, meteorology, engineering, and military applications. For example, soil geophysical properties, such as air flow resistivity, porosity, and snow or ice depth can inform other models to predict the structural integrity and strength of the surfaces for engineering and vehicle mobility applications in harsh environmental conditions. However, traditional methods are not quite suitable or available in most cold regions. Scientists cannot rely on an established network of geophysical stations, or on a handful of in situ measurements at sparse locations. Such measurements are difficult and expensive to make, frequently require laboratory analysis, and cannot deliver robust estimates for extended areas. Remote measurements of some properties using satellites are possible, but have their limitations. We propose to use a fast and cheap alternative by recording a waveform of an acoustic pulse propagating over frozen ground (or other surface of interest) to estimate these properties. The physical mechanism of the phenomena is based on acoustic pulse interaction with a surface, whose acoustic impedance depends on frequency such that the measured acoustic waveform changes its shape in accordance to the specific surface. A model for acoustic propagation over an impedance surface allows one to obtain best-fit parameters of the frozen soil or snow. We present such a propagation model and show how some soil and snow geophysical parameters can be estimated using the proposed technique. Simulations are verified by experimental measurements, and results indicate that some geophysical parameters of frozen soils and snow can be estimated by analyzing acoustic waveforms.

Ice roads in Northern Canada provide vital access for the transportation of supplies to remote communities and mining operations which are otherwise inaccessible by road. When vehicles drive across an ice road, waves in the ice are created which reach a maximum at the critical speed of the ice. The transportation efficiency is limited by the critical speed of the ice, therefore it is important to accurately determine critical speed without causing failure of the ice. To analyze the effect of varying truck speeds on ice deflection, a field study was conducted near Yellowknife, Canada. The majority of field tests use survey tools or instrumentation to measure the deflection which are effective however, they are also expensive and subject to operational difficulty in the cold environment. In this study, digital image correlation (DIC) techniques were used to capture and measure ice deflection due to a moving truck. The deflection results of the DIC method and the traditional survey method are compared for the moving load test. The greater number of DIC measurement points installed along the ice allowed for a wide area to be covered at one time, compared to the traditional survey methods. In addition, the cameras used for DIC did not experience the same disruptive operational errors as the survey total stations due to the cold temperatures. Overall, it is shown that this methodology is effective, reliable, and cost efficient in capturing ice road deflection.

Winter roads in Canada, which comprise over-land and over-ice segments, account for approximately 10,000 km of roadways. Operator experience has shown that over-ice segments often limit the operating window for winter roads—reducing the time available to haul essential goods to isolated communities and to service the private sector (e.g. mining, forestry). The operating windows for over-ice segments have generally decreased in time with a warming climate. When a floating ice cover incorporates a reinforcing element, it may better resist fracture propagation and breakthrough, and may thus better support vehicle traffic. Ice cover reinforcement could be applied to weak links in a winter road, i.e. segments known to be unreliable, or to help close off open leads in a river. Ice reinforcing elements may include wood pulp, steel cables, timbers, natural fibers, and geomembranes among many other options. Such microscopic and macroscopic ice reinforcement techniques have been tested in the past by various research groups. This paper reviews established ice reinforcement methods, proposes criteria for selecting appropriate methods, and presents preliminary results of testing on reinforced ice. In addition to strength characteristics, the environmental compatibility, the constructability, and stakeholder acceptability are primary screening criteria for reinforcement selection. Four-point beam testing has been initiated on reinforced ice samples. These tests confirm an increase in breakthrough resistance, but not an increase in strength, which may have to do with a weakly bonded surface at the ice/reinforcement interface.

Construction of highway embankments vary in thickness along its planned alignment to maintain horizontal and vertical road geometry requirements. In regions of continuous permafrost, however, the thickness of the overlying embankment greatly impacts the thermal regime of the frozen foundation soil. Thick embankments, exceeding 5 m, usually provide considerable thermal insulation where the frozen soil used to construct the embankment remains frozen in the core, while thin embankments, usually less than 2 m thick, can contribute to permafrost degradation. Climate boundary conditions also play a significant role in the thermal performance of these embankments. In order to study the thermal impact of embankment thickness on permafrost degradation and thermal embankment performance, test sections along the newly-constructed Inuvik-Tuktoyaktuk Highway in the Northwest Territories, Canada, were instrumented with thermistor strings to measure temperature readings at different locations in the embankment fill and foundation soil. This paper presents the results of the monitored temperature for two phases of instrumentation in April 2015 and April 2017 for the thick and thin embankments, respectively. Thermal numerical modelling using site climate data showed considerable agreement with field values and provides confidence for future performance prediction.

Maintenance costs have risen since 1996 along the northern Dempster Highway, especially for snow clearing. The purpose of this paper is to investigate the wind regime of the region and determine its association with increased maintenance activities. Hourly wind speed and direction were measured at four sites near the territorial border crossing (YT km 465/NT km 0) for July 2006–December 2018 at the Environment Canada Rock River station (YT km 457) and February 2014 to July 2018 at YT km 421, NT km 8.5, and NT km 51.5. Wind speeds were classified according to the Beaufort Scale and wind type: calm (force 0–1), breeze (2–6), gale (7–9), and storm (10–12). The mean winter wind speed was highest at Rock River (4.1 m/s), followed by km 8.5 (2.4 m/s), km 421 (2.3 m/s), and km 51.5 (2.1 m/s). At all sites the mean wind speed was lower in winter than summer, but the highest winds were measured in the winter. At Rock River, 9.1% of observations were for gale or storm winds, considerably more than at kms 8.5 (0.5%), 51.5 (0.1%), and 421 (1.1%). In Yukon the dominant and strongest winds were easterly off Richardson Mountains, while in the NT the dominant winds were southwesterly, but more variable in direction. There were no apparent increases in winter wind speeds over the period of record. Although Rock River experienced the strongest winds throughout the year, it exhibited the same seasonal trends in wind speed as the other locations. The dominant easterly wind direction at Rock River was consistent with km 421. The valley near Rock River is well nicknamed Hurricane Alley.

Spontaneous corrugation can occur at intersections on snowy and icy roads due to the repeated passage of moving vehicles. Corrugation adversely affects driving safety due to reduced friction between the wheels and road; it can also cause passenger discomfort and transform crosswalks into unstable surfaces for pedestrians. Because the causes and timing of spontaneous corrugation remain poorly understood, effective countermeasures cannot be applied to prevent its formation. In this study, we installed time-lapse cameras at an intersection in Sapporo, Japan, to observe the formation of corrugation in two consecutive winters (2015–2017). To determine the relationship between corrugation and environmental conditions, we obtained meteorological data from the observatory closest to the intersection and recorded the temperature distribution on the road using a thermographic camera. Our analysis showed that a threshold amount of fresh snowfall was necessary for corrugation. The air temperature required for corrugation was between 0 and -2° environment, snow, temperature, vehicle, washboard road C. Surface snow showed a tendency to thaw due to energy provided by heat transfer from the chassis of vehicles; thus, corrugation emerged at the headstream side of the traffic flow, where vehicles frequently stopped for red lights. As a result, corrugation can be predicted by forecasting environmental conditions. We also initiated a social network survey, where participants were asked to upload photographs of corrugation on snowy and icy roads to a website, along with the time and location. An analysis of these corrugation events and the associated environmental conditions supported our results. This study will contribute to improving the safety of winter travel in regions where spontaneous corrugation is common.

Climate change might increase the frequency of events such as heat waves, freeze-thaw cycles (FTC), and flooding, and more specifically in permafrost rich regions. These climate hazards are expected to have an impact on railway track performance. There is little publicly available data on their quantitative impacts on railway operations. Such quantitative data is essential for determining when, where, and to what extent climate adaptation measures are needed. Freeze and thaw cycle results in frost heave and thaw softening in track foundation (substructure). Both frost heave and thaw softening may lead to unsafe operating conditions especially for rail transit and passenger rail systems as their high operating speed makes them much less tolerant to deviations in track geometry parameters. In order to investigate the effects of a freeze-thaw cycles on an active railway, a structural and geotechnical monitoring system was designed and installed on a section of VIA’s track in Ontario. The instruments measure various track parameters such as pore water pressure, heave, and deformation at different depth within track foundation, track temperature, strain in the rail, and track surface deformation during freeze-thaw cycles. The data logging system relays static data and high speed data that are triggered by train passages. We show that the selection of instruments and design of the data logging system provide relevant geotechnical data in a manner that could be applied to northern regions and introduce recommendations for future installations. Moreover, we discuss the installation methods appropriate for cold climates because some instruments are temperature-sensitive. Since such systems typically need to be self-sufficient special considerations have to be taken to account for the relatively high power requirements of dynamic monitoring. The suggested system is shown to be useful for track monitoring projects in permafrost-rich regions where freeze-thaw cycles are a concern.

The natural freezing and thawing of soils can dramatically affect their thermal and mechanical properties, which can have destructive effects on structures built upon those soils. Previous testing in this field has attempted to predict the frost penetration depth, based on the soil, thermal, and hydrodynamic properties. A thermodynamic finite element model was developed using multiple frost-susceptible soil types tested with a variety of moisture conditions. Thermal conductivity and temperature were measured throughout several multi-day freeze-thaw cycles. It was identified that moisture migration was likely the most significant factor in frost heave and frost penetration, as free water sources in porous soils produced the largest deformations, while there was minimal heave in other frost susceptible materials. The thermal conductivity was found to increase near the freezing front across all samples, such as for low-plasticity silt soils where the thermal conductivity rose from 301 to 357 milliBTU/(hr*ft*°F), which was theorized to correspond to where the moisture was concentrated, and ice formation was highest. This guided the finite element model development by incorporating moisture flow and porosity, along with other parameters with respect to time, temperature, and ice and moisture production during freeze-thaw cycles. This was found to improve frost depth prediction compared to the standard modified Berggren equation, where for our tested conditions the equation had an error of 2.2 inches for a frost depth of 8 inches, while our model had an error of 1.4 inches for the same depth. These developments will be of great importance to airfield runway and general pavements design and maintenance in frost-affected regions, allowing for a more accurate prediction of frost depth and deflection during freezing and thawing periods, and expected frost heave damage across multiple seasons.

A common road insulation practice in Norway is to use a layer of crushed rock material, which is called a frost protection layer (FPL). The current regulations allow a large variation of particle size distribution into this layer. This paper presents field investigations on frost insulation performance of crushed rock material with three distinct grading. A full-scale test site was built in Røros, Norway, with each FPLs composed of 1 meter of crushed rock aggregates and built as: Ro-3 section was a coarse dense-graded material (0/120 mm), Ro-1 section, a coarse open-graded material (40/120 mm) and section Ro-2, a fine dense-graded material (0/32 mm). The sections were monitored for two winters (2016–17 and 2017–18). The results showed a significant difference in frost penetration and capacities between the sections. For winter 2016–17, the frost depth reached 194, 136, and 175 cm in Ro-1, Ro-2, and Ro-3 sections respectively, for a surface freezing index of 22,630^oC·h. For winter 2017–18, the frost depth reached 232, 171, and 209 cm in Ro-1, Ro-2, and Ro-3 sections respectively, for a surface freezing index of 36,683^oC·h. The 0/32 mm material provided the best insulation capacity with a frost protection capacity of 443°C·h/cm. The frost protection capacity for the 0/120 and 40/120 mm material were of 253 and 85°C·h/cm respectively. The study showed that fine dense-graded material provided superior frost protection mostly due to the larger amount of water retained that increased latent heat. For similar road design and layer thicknesses, the coarse, well-graded material seemed to be the most cost-effective material adapted to Norwegian regions with F₁₀₀ < 28,000°C·h. Coarse, open-graded material should be used in low FI areas, and convection effect should be taken into account.

The lightweight deflectometer (LWD) was designed to test the compaction or bearing capacity of in-place aggregate base-course materials. This study evaluated the LWD at temperatures near and below freezing, below of its typical temperature range for road construction. Initial field LWD tests were run on a variety of compacted snow surfaces over asphalt pavement, gravel, and soil in the winter of 2018 in both Montana and Michigan. The LWD measures load and deflection, enabling calculation, and backcalculation of stiffness parameters for the test surface layers. The field results were reasonable for the snow layers analyzed. However, the results indicated LWD may also have issues with the effects of low temperature testing on its components, specifically the rubber load buffers. Therefore, in the fall of 2018 a series of LWD tests were performed in cold rooms to evaluate the equipment without the variability of the snow surfaces as a parameter. This series of controlled tests determined that the LWD could be operated in conditions as cold as -25°C. However, care must be taken in interpreting the results of tests conducted at cold temperatures. The ambient temperature and the duration of the LWD’s exposure to these conditions will affect the accuracy of testing. Significant changes in the LWD test results occurred after 24 hours of exposure to 0°C, after two hours of exposure to -10°C, and after only one hour of exposure to -20°C or a half hour of exposure to -25°C. The LWD should not be stored in freezing temperatures prior to testing, and temperature and length of exposure should be monitored and recorded during field testing.

Roads and highways in cold regions are affected by the settlement of embankments leading to dangerous trafficability issues. There are uncertainties regarding the mechanical behaviour of embankments built on permafrost. The objective of this project is to quantify the relative importance of consolidation, frost heave, and long-term creep of the foundation material. Understanding the predominant mechanism of instability and deformation of the embankments for different types of soil contributes to the development of efficient mitigation strategies; thus, providing better transportation infrastructure for northern communities in permafrost regions. The studied site is located in continuous permafrost at kilometre 82 of the Inuvik Tuktoyaktuk Highway 10 (ITH) in the Northwest Territories, where vertical and horizontal inclinometers were installed to monitor and collect data from the movements of the embankment. Investigation also includes temperature recording with thermistor strings to monitor the influence of the embankment on the thermal regime of the ground. The results of the field data analysis show that the displacements observed are the result of a combination of multiple mechanisms occurring in the foundation material, where horizontal and vertical settlement can both be observed. The effect of those mechanisms is greater at the natural ground surface and decreases exponentially with depth. However, multiple uncertainties exist about ground conditions, which makes attempts to assess the role of each mechanism very difficult.

Given the properties of the materials and the typical cross-section of an embankment or dam, the use of structural models (i.e. finite element method) to analyze the response by calculating the set of stress-strain is straightforward. However, the use of such analysis requires accurate input information; otherwise, the results obtained may be questionable. The analysis of the effect of heavy vehicle loads on earth dams is poorly documented in past research. However, in these structures, some materials such as fine-grained core materials, can be sensitive to damage induced by stresses under moving heavy vehicles. This paper presents the formulation of empirical models associated with the mechanical response of the top part of a dam core constituted of glacial till to support the assessment of the effect of heavy loads circulating on rockfill dams. Laboratory tests and field measurements were used as a reference to develop analytical and empirical analysis models. Resilient modulus and permanent strain rates were evaluated to support the development of the approach.

In cold regions, differential frost heave during winter and bearing capacity loss during spring, induced by seasonal temperature variations, lead to several types of surface profile deterioration. Thermal insulation is commonly used as a preventive measure to limit the frost penetration in frost sensitive subgrade soil, thus reducing the associated damages and rehabilitation costs. In Canada, extruded polystyrene is widely used for pavement insulation. However, new alternative materials are now available, including foam glass aggregates made from recycled glass of various origins. Foam glass aggregates can be considered as a lightweight and insulating granular material. This research focuses on the thermal behavior of this material in two case studies, i.e. in the laboratory and on site. The laboratory-controlled pavement section was built in a pit where thermal conditions and water table levels are precisely controlled. Using in situ road sections built on frost sensitive soils, several flexible pavement design techniques used in Québec were compared. The first section was insulated using foam glass aggregates designed following European producer recommendations, the second was insulated using extruded polystyrene panels, and the third is a conventional pavement structure without insulation. The thermal and performance data collected at both sites were used to assess the thermal behavior of the sections and to calibrate a thermal model. The results obtained from this study support the validity of the European recommendations and will be used to develop new optimized design procedures adapted for the Canadian context.

The use of thermal insulation layers in flexible pavement structures increases the durability of the pavement and decreases the maintenance and rehabilitation costs. Indeed, this technique limits frost penetration in the frost-sensitive subgrade soil, thus reducing the impact of freezing and thawing cycles responsible for the winter differential heaving and the spring bearing capacity loss experienced on the road network. The impact of climate change on pavement performance can result in rolling comfort deterioration. However, because of its intrinsic characteristic, a thermal insulation layer is typically weak from a mechanical perspective. Therefore, for an adequate design, a compromise needs to be made between mechanical and thermal characteristics. In Quebec and the rest of Canada, extruded polystyrene is the recommended material for pavement insulation. New alternative materials are becoming available, among others foam glass aggregates made from recycled glass of various origins, which are lightweight granular materials. This study presents the mechanical performance assessment of a foam glass aggregate layer based on three levels of experimentation, from the laboratory to in situ flexible pavement structures in cold regions conditions. The results presented were obtained using the resilient modulus test, the response of an indoor experimental pavement tested with a heavy vehicle simulator, as well as using falling weight deflectometer (FWD) measurements taken on an experimental test track, which is composed of a standard section without insulation and two insulated sections. The results indicate that foam glass aggregate layers have interesting mechanical properties.

The release of water from hydropower plants into downstream rivers is primarily driven by electricity demand, creating sub-daily fluctuations in flows, a phenomenon known as hydropeaking. In Southwestern Yukon, the Aishihik plant releases most of its annual volume during the winter, when non-controlled rivers are at their lowest levels. Massive volumes of water released during that period of the year may be enhancing freeze-up ice jams and associated flooding. The present study uses a multi-method approach that includes signal treatments to characterize the influence of water releases from the Aishihik plant on river discharge at selected downstream gauging stations. Overall, this study shows that water releases from the Aishihik plant significantly influence the Dezadeash River discharge at a station located approximately 50 km downstream. The average Dezadeash River discharge is approximately double what its natural level would be during the winter. The effects of hydropeaking from the plant are clearly observable in the Dezadeash discharge sub-daily time series, even during months when plant operations are limited. During the winter, the Alsek River discharge, measured at a station located at more than 150 km from the plant, is also influenced by the Aishihik hydropower plant. The lack of data availability at that station did not allow for an estimation of the degree to which winter discharge may exceed its natural regime.

The U.S. Army Corps of Engineers supports accurate terrestrial, atmospheric, and environmental awareness from tactical to global scale in support of its national security, international development, and humanitarian functions. Moreover, the Cold Regions Research and Engineering Laboratory specifically estimates geospatial snow properties in support of the Corps civil works mission which include managing waterways in snow impacting watersheds, winter vehicle mobility, and other national intelligence functions. Snow is a spatially and temporally evolving medium that has a diverse set of impacts on engineering applications and operations. While some operational organizations provide general snow information with a regional to global perspective, the time and length scales do not match tactical or engineering requirements. Fine-scale spatial representation of snow requires observations or simulation of several snow characteristics including snow depth, density, albedo, stratigraphy, microstructure, and temperature. The Remote Snow Assessment Team at the Cold Regions Research and Engineering Laboratory has addressed user needs through the use of a combined multi-sensor, modeling framework to improve global snow characterization and enable assimilation of remotely sensed observations. Case studies from both military and civil works applications are highlighted showing successful methods developed to provide high spatial/temporal resolution snow products, snow climatologies from historical analyses, and solutions to solve snow issues with respect to water resource management, flood hazard assessment, and winter mobility modeling.

The Cree Community of Whapmagoostui is facing serious runoff water management issues on its territory. During periods of heavy rain and during the snow-melting season, significant accumulation of runoff water in certain sectors of the community impedes pedestrian and vehicular traffic, in addition to causing damage to streets and buildings. Traffic areas become difficult and frequent interventions (levelling and surfacing) are required. Repeated levelling operations caused aggregate segregation and exacerbated the emergence of surface holes and depression. This situation worsened over the recent years as the effects of climate changes become more a reality. CIMA+ proposed and tested in 2016–2017 a simple concept using conventional detention plastic chambers to achieve water storage, at a first location in the elementary school yard. These chambers allow for water percolation but also for sand and particles sedimentation. After two years of service performance in the field, the system has proven efficient and has provided a practical solution adapted to the needs of the community. Due to the remoteness of the Whapmagoostui Community which has no terrestrial link to other southern communities, supplies and construction materials can only be sea or air lifted. The lightweight plastic detention chambers become a preferred component of the drainage system, relatively easily transported, stored, and put in place. One of the key elements of the success of this project is the implication of a local Cree workers crew that has been assembled by the public works department. The Cree workers and CIMA+ team learned to work together, to plan the work sequence, to secure the materials and equipment ahead of time, to prevent health and safety hazards, and to measure the importance of quality craftsmanship. The CIMA+ team will take a leadership role in the community as the construction work activities intensify in the near future.

The manual measurement of snow density through sample collection and liquid water content by calorimetry can be cumbersome and time consuming, while electronic methods are considerably faster. Field and laboratory experiments were conducted to compare several techniques for measuring snow density and moisture content. Two methods for the measurement of snow moisture were used in both field and laboratory settings: the Denoth meter capacitance plate and the Toikka Oy “Snow Fork” microwave resonance technique. Snow density was measured using three techniques: a direct sample measurement (rectangular snow scoop); snow fork; and, in the lab setting, the Bruker Sky-Scan 1173 Micro CT-X-ray scanner using image analysis techniques. Results show that the snow fork densities are generally reliable in dry snow but become inaccurate (low) in wet snow. Density from direct sampling was on average 0.037 g/cc greater than the snow fork density. Densities measured by the Micro-CT were inaccurate once the snow began to melt, primarily due to sample collection and processing technique. For moisture measurements, we found the Snow Fork to be a reliable tool for measuring the moisture content and density of snow. The Denoth moisture values are on average 0.054% by volume higher than the snow fork moisture. All Denoths tested, report similar moisture values, which was encouraging as these devices are over 20 years old and there is no other source for calibration.

In permafrost regions, the movement of water during winter has important implications for hydrology, land use, and infrastructure. Knowledge of winter hydrothermal dynamics in small, extensive tundra stream networks is limited. Climate warming, changing precipitation regimes, and increases in tundra vegetation coverage may delay active layer freeze-back, potentially increasing winter water movement. The primary goals of this research are to improve knowledge of the thermal regime of small stream channels in continuous permafrost, explore the implications of a changing climate and runoff, and describe the influence of infrastructure on channel thermal regime. A program of temperature monitoring in stream channel beds and riparian margins between Inuvik and Tuktoyaktuk is presented here. Preliminary results, if representative of several years, suggest that permafrost is not present at depths shallower than 3.5 m below the bed of a small stream with a contributing area of <30 km², and that this layer does not likely re-freeze during winter. This thermal regime may be modified by highway crossings that reduce or eliminate stream snow cover, and the degree of thermal disturbance may be a function of contributing watershed size. This research and further related work have the potential to provide new insight on channel thermal regime and winter hydrology in permafrost regions, offer projections of change in the context of a warming climate, and help inform the design, operation, and mitigation of hydrological issues associated with linear infrastructure in permafrost.

In the event of an Arctic oil spill, ice in the water is a complicating factor. The presence of ice complicates the forecasting of the movement and spreading of oil as well as the planning of the oil spill clean-up process. The underside of Arctic Sea ice is not flat, rather it presents non-geometric, unpredictable protrusions into the water column. The depth to which these protrusions grow relates to the longevity of the ice itself. The challenge faced by the oil spill forecaster is that information on the under-ice storage capacity is not readily available. Hence, we explored how to estimate under-ice storage capacity based on the ice stage. Historical reports on Arctic sea ice stage (e.g., first year, thin ice) were obtained from the Alaska Ocean Observing System. Ice stage data is available daily in the form of an ice “egg” code, similar to the CIS/WMO egg. Next, we acquired historic data on under-ice storage capacity. During the winters of 2010–2013, Shell deployed upward looking sonar at several sites in the Beaufort and Chukchi Seas. The sonar made direct measurements of ice draft. The under-ice storage capacity—defined as the volume of pore space above the average ice draft level—was estimated based on the ice draft data. Analyzing the ice draft alongside the ice stage data, we developed low, medium, and high estimates of oil storage capacity. When the primary ice stage is assigned an ice egg code of 1 to 3, storage capacity is deemed “low,” identified by less than 15,000 m³/km². For primary ice stage with a 7 to 10 ice egg code, storage capacity is “medium,” between 15,000 and 50,000 m³/km². Older ice with an ice egg code of 11 or greater has a “high” storage capacity of 50,000 to 80,000 m³/km².

This study investigated the use of deep convolutional neural networks (DCNN) for monitoring river ice imagery generated by remote cameras on the Pend Oreille River, Idaho. The cameras were installed at selected locations along the river to provide information on ice conditions to aid in the wintertime operation of the Albeni Falls Dam. Manually reviewing the imagery for the presence of ice is difficult for large volumes of imagery. The primary advantage of DCNNs compared to other machine learning algorithms is that features in the image can be directly inferred from the image data without any subsequent data transformations or derivative products. High-angle oblique imagery collected periodically (e.g. hourly) on the Pend Oreille River was used to repurpose a highly-efficient, pre-existing DCNN. A transfer learning methodology was employed to retrain and test the DCNN using ground training tiles derived from a weakly supervised conditional random field. The tiles represented river ice, snow, terrain, water, and vegetation. The model converged with an average testing accuracy of 95%, an average f1 score of 94%, and an ice classification accuracy of 82%. The operational effectiveness of the model was assessed by applying it to several years of winter imagery which contained a large spectrum of lighting and weather conditions. The resulting time series of predicted conditions was validated against manually sorted images. The DCNN classifier accurately predicted the daily presence of river ice with an f1 score of 76% when compared to the manual classification. The model presented in the study can aid winter operation engineering decisions of water managers by providing automated alerts of river ice conditions.

Gas pipeline transportation crossings (trench method) under the large rivers with destructive spring flood and intensive ice jams involves very different safety hydro-technical issues of operation. Such as changing the riverbed, the banks destruction, the new channels formation, erosion, and formation of alluvial sedimentation. For the effective application of the remote control method of underwater gas pipelines for the purpose of operational inspection of its technical condition it is necessary to improve the methodical of GPR application. Low-frequency linear GPR with a frequency of 50 MHz and 100 MHz (OKO-2, Logis-GEOTECH Company) to study the water surface of the Lena River depth up to 20 meters are applied. A special device for waterproof of antennas is developed. And also, if it necessary, a special equipment to submersibility the antennas to a depth of 1 meter is constructed. The paper presents the results of the survey of the operated main gas pipeline in the period 2014 to 2017, including monitoring of changes in the conditions of occurrence, as well as determining the exposure of the pipeline due to the erosion of the banks after the destructive spring flood. For the first time, the technology of changing the orientation of the receiving and transmitting antenna are applied to increase the search area of the pipeline in the bottom sediments at a depth of more than 8 meters, which is also disclosed and described in the paper. Experimentally proved the effectiveness of the GPR using in the inspection of gas pipelines at river crossings with a depth of more than 10 meters, buried in the sediments with a capacity of more than 6 meters. The method of increasing the search area of pipelines is developed.

Lake shoreline erosion is caused by wind-generated waves (mechanical erosion) and, in areas of permafrost, can be compounded by thawing ground ice (thermal erosion). In southwest Yukon, erosion patterns along the shorelines of Aishihik and Canyon Lakes reflect the combined effects of climate change and lake level regulation for hydroelectricity, which began in 1975. An investigation characterizing shoreline erosion and aiming to determine the relative contributions of lake level regulation and climate change was undertaken to support an environmental and socio-economic effects assessment associated with hydroelectric facility relicensing. The investigation involved three phases: (i) compilation and review of pertinent topographic, geological, and hydrological information; (ii) helicopter- and ground-based field reconnaissance; and (iii) mapping of shoreline types, relative severity of erosion and recession from former beaches at select sites. Three types of shorelines were identified based on their distinct responses to lake level regulation and climate change. Type 1 shorelines exhibit a moderate slope of coarse-grained sediment and may contain ice-poor permafrost; they are relatively insensitive to climate change and quickly self-stabilize when exposed to higher lake levels. Type 2 shorelines typically exhibit an abruptly steep embankment of ice-rich, fine-grained sediments; they are vulnerable to recession through long-term retrogressive thaw and slumping in response to climate change and lake level regulation. Type 3 shorelines are typically low-relief and composed of fine-grained, ice-rich sediments; they are most sensitive to higher lake levels due to inundation-induced thaw. Erosion along the Type 2 and Type 3 shorelines of Aishihik and Canyon Lakes appears to be driven primarily by climatic effects, despite an anomalous peak in lake level at the onset of regulation that locally initiated and exacerbated erosion.

The U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) provides cold regions research and development in support of the U.S. military and the nation. For winter military operations this support includes vehicle mobility modeling over snow. Many factors relate to vehicle performance, fuel efficiency, and operation efficiency, including the vehicle specifications and the land surface conditions. Comprehending snow macromechanical characteristics—such as elastic modulus, stiffness, and strength—is critical in understanding how effectively a vehicle will travel over snow covered terrain. Vehicle instrumentation data (inertial measurement units and vehicle telemetry) and observations of the snow pack (both satellite and ground-based) are leveraged to improve the modeled index for winter vehicle performance. Currently, the available mobility models are physically-based and consider numerous factors related to cross country mobility such as slope, soil type, terrain strength, land classification, and vegetation. The algorithms related to the impact of snow, however, are driven by snow depth and bulk snow density alone. This research deployed a SnowMicroPenetrometer (SMP) whose capabilities were expanded to measure several types of snow, including virgin snow, vehicle tracked snow, and processed or groomed snow roads. The SMP high-resolution snow structural profiles show the value of the instrument as a tool for mobility studies. Correlation analysis was conducted between the SMP and Rammsonde penetrometer using median values from different snow types at a particular site. The data express a trend that rupture force, penetration force, density, strength, and ram hardness increases when the snow is deformed by the vehicles. Instrument modifications were assessed with recommendations made to further improve SMP performance for use in mobility studies.

In the North Slave region, permafrost developed in a time transgressive manner throughout the Holocene with lake-level recession, giving rise to the Great Slave Lowland and Great Slave Upland ecoregions of the subarctic Canadian Shield. Thermokarst in the region is commonly associated with degradation of numerous ice-cored mounds called lithalsas. Here we use site descriptions and air photos to document the distinctive geomorphic signatures associated with degrading lithalsas and develop a conceptual model for lithalsa degradation in this region, which builds upon an earlier model of lithalsa development. Physical degradation of lithalsas is dominated by two main processes: (i) subsidence indicated by the common occurrence of ponded water with partially submerged standing dead trees, and (ii) colluviation of thawed sediments toward the lithalsa margin that results in a rampart. According to these diagnostic criteria, satellite image analysis suggests that lithalsas were more widespread at higher elevations in the past, but the majority have degraded. This explains, in part, the reduction of lithalsa abundance with increasing elevation. The results suggest that lithalsas are vulnerable to thaw. Following from our observations and findings, we develop a conceptual model of lithalsa degradation. It suggests that soil hysteresis effects would likely prevent re-initiation of lithalsa formation if permafrost were to re-aggrade in the future.

Permafrost is generally sustained in tundra lakes beneath water depths less than 2/3 of the maximum ice thickness. Few talik development models consider areas of shallow water even though widespread talik development beneath shallow water may result from environmental change. In thaw lakes where frost does not penetrate the lake bottom, talik development has been successfully predicted using models such as the Stefan solution based on mean annual lake-bottom temperatures (T_lb). In the nearshore zone of the tundra lakes of Old Crow Flats, YT, frost penetrates the lake bottom sediment in early winter, yet T_lb are greater than 0°C and permafrost sustainability is controlled by the thermal offset. This research assessed whether the Stefan solution can provide reasonable estimates of talik development under such conditions. We compared model results to talik depths measured by water-jet drilling along transects perpendicular to four receding shores. The Stefan solution predicted talik depth and shape well where seasonal freezing and thawing of the sediment was limited in duration by rapid subsidence of the lake bottom beneath maximum lake-ice thickness. Prediction accuracy increased when talik depth was calculated in two stages to reflect an increase in T_lb once the lake bottom subsided to depths exceeding maximum lake-ice thickness. The Stefan solution was ineffective where shore erosion was slow (<0.2 m a^-1 over 50 years) and water depth was shallow (<0.5 m) over an extended area near shore, because variations in snowpack thickness determined permafrost sustainability and degradation rates, resulting in irregular talik geometry.

During the winter of 2018 field experiments were conducted to assess the mechanical properties of virgin, groomed, and compacted snow. These strength measurement techniques assessed the bearing and shear capacity of the snow, or a combination thereof. Many of the methods were adapted from those used in soil and pavement assessments and could be related to California bearing ratio; and others were techniques specifically designed for snow characterization (Rammsonde, Russian snow penetrometer, CTI penetrometer, Yamaha drop cone). The results illustrate typical values and ranges for the strength of different types of snow surfaces, and the applicability or effectiveness of the different tests to specific snow conditions.

The Heart River drains approximately 3,360 square miles in southwest North Dakota, flowing through the city of Mandan, ND, before entering the Missouri River near Bismark, ND. Flood protection and irrigation projects have been constructed over the years in the Heart River basin, including the Heart Butte Dam constructed in 1949 by the U.S. Bureau of Reclamation approximately 100 miles upstream of Mandan. While this altered the hydrology of the basin slightly by providing storage, irrigation opportunities, and increasing evaporation, the Lower Heart River can cause both open water and ice jam flooding in the city of Mandan. Flood protection levees have been constructed over time in Mandan starting in 1959 with improvements added in 1963 and in 1989. An effort to provide increased flood protection and to re-certify the levee system in Mandan to Federal Emergency Management Agency (FEMA) protection levels is being undertaken by the Lower Heart Water Resource District. The effort included a reanalysis of the historic discharge and stage records of the USGS gage at the upstream edge of the city. An analysis of past ice jamming events, river and floodplain geometry, and ice jam mechanics found that there is a peak discharge for which an ice jam can remain in place and that this discharge varies depending on river location and local geometry. The analysis indicated that the 1% annual exceedance probability ice jam discharge is 42,000 cfs, but the peak discharge for which an ice jam could remain in place varied between 15,000 and 25,000 cfs depending on river location. The paper describes the analysis techniques used to develop the combined stage frequency values for the levee recertification.

The design of buried pipelines in permafrost regions or artificially frozen grounds requires knowledge of the uplift resistance. The uplift resistance of frozen soil is dependent on soil mechanical properties such as tensile strength, shear strength, and deformation modulus, and those properties are critical for characterizing the plastic yielding zones in the frozen soil around the pipe. Due to the existence of a large amount of unfrozen water, frozen clay soil displays complex mechanical properties which vary with temperatures. Previously, extensive experimental and simulation work has been done on the soil pipe interactions at normal temperatures, but less attention is given to the frozen soil pipe interactions. There are limited researches on frozen clay pipe interactions with the consideration of temperature changes. In this study, finite element analysis is conducted to investigate frozen clay soil-pipe interactions at varying temperatures, where a pipe is simulated as being subjected to vertical load-controlled or vertical displacement-controlled stress path conditions. The temperature-dependent mechanical properties of frozen clay soil are obtained from the literature. Both tensile yielding and shear yielding behavior are included in the modeling and the temperature-dependent yielding surfaces are included in an explicit way. A comparison of results from the Mohr-Coulomb model with tensile cut off and the hyperbolic Drucker-Prager model is presented. The results indicate that hyperbolic Drucker-Prager model is an effective model for analyzing the plastic zones. Under a plane strain condition, the applied hyperbolic Drucker-Prager model gives more conservative uplift resistance-displacement relation when compared with the result from the Mohr-Coulomb model.

Following four years of construction, a new open-pit to access a diamondiferous kimberlite pipe (A21 Pipe), was officially opened at the Diavik Diamond Mine on August 20, 2018. The site is located approximately 300 km northeast of Yellowknife, NT, in a zone of continuous permafrost. The A21 Pipe is in a depression just offshore of South Island in Lac de Gras that had developed a through talik. A 2,200 m long ring dike was constructed to allow dewatering of the depression and to mine the kimberlite pipe by open-pit mining. Near the lake shore, the rockfill dike is founded on permafrost, whereas in deeper waters, the foundation is on unfrozen lakebed sediments and till over bedrock. A cut-off wall was installed to reduce seepage through the dike and its unfrozen foundation. Within the section of the dike founded on permafrost, the frozen soil and bedrock are used as a hydraulic barrier. It was therefore essential to understand the extent of the permafrost into Lac de Gras, especially on the South Abutment, where the water is shallow, and the lakebed topography forms a complex-shaped submerged peninsula with talik under the permafrost. Boreholes and geophysical surveys were used to estimate the extent of the talik and provide input for the design. During the initial phase of construction, extensive ground temperature monitoring and detailed observations were used to verify the extent of permafrost assumed in the design. These measures helped with the understanding of the complex ground thermal regime and provided information on the thermal behaviour of the foundation required to guide some of the construction decisions, such as the required initiation of active freezing by the use of thermosyphons or the timing of the placement of additional dike embankment construction material to accurately lock in winter frost and protect the permafrost from thawing.

Different heat transfer mechanisms are possible depending on the particle size and on the saturation degree of the foam glass aggregates. Foam glass aggregates of particle size between 20 and 60 mm were tested with downward and upward heat flows. While the main transfer mechanisms during downward heat flow were conduction and radiation, convection cells were noted when the bottom plate was heated and the upper plate cooled. A linear and uniform temperature distribution was noted in the cell when the heat flow was downwards (conduction and radiation heat transfer mechanisms). The equivalent thermal conductivity of the tested sample is 0.18 W/°C.m. When upward heat flow was induced, the heat flow increased with the difference of temperature between the top and bottom plates. However, unlike downward heat flow, the temperature distribution was not linear and uniform in the cell. The convection cells created a non-uniform heat flow distribution and consequently a non-uniform temperature distribution. The intrinsic permeability of the tested sample is 0.345×10^-6 m².

Currently, facility managers are faced with many advanced decisions regarding when and how to inspect, maintain, repair, or renew existing facilities in a cost-effective manner. The evolution of the deteriorations of road structures in reinforced concrete depends on the exposure of the elements to water in liquid form or vapour and to other aggressive agents such as chloride. Current models of ionic transport neglect the effect of real ionic concentration in contact with concrete structures, it means boundary conditions are considered with simple tendency as uniform concentration during the winter period and model parameters are derived from the fitting method. Therefore, it implies in ineffective prediction models of deterioration, i.e. steel rebar corrosion by chloride presence or carbonation, alkali-granular reaction, acid attacks, etc. Structure are sensitive to their environment and their interaction with it is directly related to the processes of deterioration. The degradation of structures exposed to salt-laden mist is faster in the wetter areas. On the contrary, the deterioration of the structures caused by salt spray in the drier zone is slower. The structures, exposed to splashing (precipitation, wind, splash, etc.), have a slower rate of degradation in the wetter regions. The amount of rain has an indirect effect in the process of deterioration of the structure exposed to salt-laden mist because it changes the contact time of chloride on the surface of the structures. For this purpose, a unique exposure monitoring was developed. This mobile station, named MExStUL, contains an atmospheric sensor and new possibilities of chloride detection contained in splashes, mist, and static water near the road improving the real exposure of structure and the boundary conditions. First results highlight the real influence of environmental parameters on structures durability on highways. Salt concentration is not uniform during winter period and water thickness demonstrate important periods of drying.

An LNG storage tank in Fairbanks, Alaska, is one of the first LNG storage tanks constructed on permafrost soils that has been designed as an at-grade foundation. An at-grade mat foundation was selected for this tank over the typical pile supported foundations due to the seismic hazards at the site. Above-grade construction activities for the LNG storage tank were planned to occur over an 18-month period. The construction included a large poured concrete mat foundation, which generated significant heat during curing and had the potential of impacting the underlying permafrost. In addition, the outer concrete tank shell was planned to be heated over the next year to facilitate construction of the inner steel tank. An active cooling system installed below the storage tank was designed, constructed, and used to maintain the permafrost, thereby mitigating the thermal impacts of tank construction activities. Thermal finite element modeling of the system was performed before construction to develop an adequate design. During construction, soil temperature measurements were collected at and above the level of the active cooling system to monitor system effectiveness. Comparisons between the modeled and actual soil temperatures are compared and an evaluation of the active cooling system is presented.

The ever-increasing need to maintain aging existing reinforced concrete structures, especially in severe winter environments, in good condition and a cost-effective manner arises mainly in structural health monitoring methods, where it is necessary to adopt approaches that allow early detection of corrosion. Chloride-induced corrosion is a significant durability issue in cold regions where de-icing salts are used. This paper presents an embedded optical fiber chemical sensor that detects reliable free chloride concentrations into concrete cover in a precise non-destructive manner. It is based on fluorescence measurements using a chloride-sensitive fluorescent calcium-alginate sol-gel. Optical fibers were not affected by environmental factors, ions presences, or cold climate. Nevertheless, the fluorescent chemical sensor showed sensitivity towards alkalinity, temperature, leaching, and photo-bleaching. These restraints were encountered by applying a successfully validated ratiometric fluorimetry approach. Also, the durability and long-term stability of the sensor were studied. This sensor detects low chloride concentrations in a range of 0.045–0.45 M present in pore solution. It demonstrates a robust behavior, and excellent long-term stability so that it can withstand harsh environments. Thus, this sensor could provide a new approach towards the rapid, simple, and non-destructive monitoring of the structural health for detected the onset of corrosion damage.

Ground anchor and soil nailing have been mainly applied in Japan as permanent and stable construction technology for unstable cut slopes. However, slope surface structures, such as ground anchor and soil nailing, may be damaged in cold districts like Hokkaido. Cut slopes in cold districts have experienced surface layer loosening due to the repetition of freezing and melting. Such a frost heaving phenomenon of the foundation is thought to be one of the causes of cut slope damage. However, the effects of the frost heaving pressure and time, acting to cause the damage, have not been confirmed, and as a consequence, no design or maintenance methods considering countermeasure technologies against frost heaving in slope surface structures have been established. Therefore, to study countermeasure technologies against frost heaving acting on slope surface structures, the load acting on ground anchor and soil nailing was measured in many places in Hokkaido. The results of the study enabled confirmation that the load acts on ground anchor and soil nailing in winter and is released in the early spring. Moreover, this phenomenon was repeated in the investigation period of more than multiple year years. Furthermore, it was found that the load does not act on ground anchor or soil nailing in regions with non-frost heaving soil, much snow, and cover soil.

The Inuvik to Tuktoyaktuk Highway includes eight bridges. The 140 km route is underlain by continuous permafrost, much of it ice-rich. Bedrock is generally too deep to be accessed for foundation construction. Mean annual ground temperatures ranged from about -1.8°C to -4.3°C near proposed bridge locations. Adfreeze steel pipe piles, which are generally suited to relatively light sustained loads, were selected as the foundation type for the bridges. Bridge loads tend not to be light and there is not much precedent for the use of adfreeze piles as bridge foundations. There were two particular challenges for the pile designs in this application. Firstly, the strength of permafrost is time-dependent. Adfreeze piles are designed by assuming they will settle in creep under load. For these bridges, traffic live load was a high proportion of the overall foundation load. Permafrost has higher resistance to short-term loads than sustained loads, all else being equal. The short duration of individual traffic load events was considered to justify correspondingly high capacities for traffic loading. Second, the bridges are required to have a 75 year design life. Warming of the permafrost is anticipated in response to predicted climate warming. It is likely that at least some of the permafrost will approach the onset of thaw over the design life of the bridges. A strategy is being implemented to monitor ground temperature response and implement mitigative measures, if pile capacity is determined to be compromised in the future. This paper describes the design rationale, including an adaptive response to climate change using thermosyphons.

The initial ground temperature response for the first building supported on a thermopile foundation in Canada is reviewed. The building is the RCMP detachment in Inuvik, NT. Challenging geotechnical ground conditions at the site that influenced the selection of the foundation type included an up to 3 m thick unfrozen zone (talik) below the active layer, up to 10 m thick ice and ice-rich soils, and warm permafrost temperatures. At the time of design, it was not known if water flowing through the talik would impede foundation freeze-back. The structural design of the building proposed a total of 128 piles in five pile loading groups with variable pile spacings. These were consolidated into three design groups for geotechnical design, which considered projected climate warming for a design life of 50 years. Four thermistor cables were installed to permit ground temperatures to be measured, and the data is being collected with dataloggers. The first four years of data is summarized. It shows that the thermopiles have cooled the ground more than what was predicted during the design, which was intentionally conservative, due to the precedent-setting use of this technology in Canada. Two significant practical implications from this review are that the observed cooling suggests that this foundation type will be resilient to climate change and the performance data being collected data will permit future designs to be optimized.

In fact, huge number of ground anchors with concrete frame are used to protect landslide of slope in cold regions, which may have a serious risk of rupture or pop out of wires due to over tensioned and loosening caused by frost heave and thaw settlement of slope. Center hole type load cells are generally used to monitor tension force of wires at ground anchor head, which have not been effectively used to cover wide area of slope because they are expensive, large, and heavy to deal. Authors are developing a new monitoring system of anchored slope protections making use of small, light, and low-cost MEMS inclinometer and wireless communication device, which might be replaceable with the direct measurement of wire tension using large load cells. Tension force of anchored wires is calculated using precise data of inclination angle of anchored concrete frame obtained by sensors fixed near to anchor head. The frame inclination data are telecommunicated by wireless through communication base nearby to display on web site in real time. Monitored data in field, laboratory test results using model frame, and FEM analysis are shown in the paper, which support the system is highly practical to know real time condition of slope stability, and to judge optimal time of re-tense of wires effectively in minimum number.

Numerous case studies are presented with regularity which show that compaction of soils during the winter is fraught with generally inadequate results. The LNG storage tank construction timeline provided very few options for excavation and backfill activities to occur in warmer months. Careful consideration was given to key parameters required for compaction during the winter in Fairbanks, where the average winter temperature is -15°C. Air temperature, wind, soil temperature, and moisture conditioning constraints were defined prior to the start of winter compaction efforts. Careful execution of the plan and attention to the weather and soil behavior allowed for a successful structural backfill compaction effort. The paper identifies the key parameters and discusses instances when conditions varied those parameters and how construction was impacted. Additional discussion is presented regarding the integration of other site work and construction activities at adjacent facilities.

Transport infrastructures built on frost-susceptible soils may require insulation layer to minimize frost penetration. In Norway, one of the approaches is the use of lightweight aggregates (LWA) as an insulation layer, especially when there are specific restrictions for pavement thickness. Performance and design thicknesses of LWA are included into the Norwegian Road Design Handbook. The current regulations allow the use of LWA layers with or without an underlying lower frost protection layer (LFPL). The goals of this paper are to a) observe the frost insulation capacity of lightweight aggregates and b) investigate the necessity of lower frost protection layer below the lightweight aggregate layer. A full-scale road test site was built in Røros, Norway, with three sections using LWA for insulation purposes. For these sections, a 0.6 m thick insulation layer of expanded clay (Leca) with particle size of 10/20 and 0/32 mm and foam glass (Glasopor) with particle size of 10/60 mm was constructed. An underlying LFPL with a thickness of 0.7 m was made of crushed rock material with particle size of 0/120 mm. Temperature was monitored for two winters (2016/2017 and 2017/2018). The cumulative surface freezing index (FI_s) for the two winters resulted in 22,630 and 36,683°C·h respectively. Field observations show that the performance of all three insulations layers was generally the same. The results showed that for both winters the frost front remained in the LWA layer. The study shows that lightweight aggregates could be placed directly on frost-susceptible soils and the frost front will remain in the 60 cm insulation layer even at FI_s of 36,683°C·h.

Fine-grained soils are normally not suitable as subbase in road, railway, and other largescale constructions due to their compressibility, low shear strength, and/or frost susceptibility. Common procedures to improve the subbase are soil replacement, lightweight fill, or insulation. The engineering properties of fine-grained soils can also be improved in situ by mixing them with hydraulic binders. A SWOT analysis based on literature study indicates that near-surface soil stabilisation has opportunities as a method. However, one major weakness of the method of near-surface soil stabilisation is the question of strength reduction as a consequence of freeze-thaw cycles. It is unclear how near zero curing temperature followed by freeze-thaw cycles, representing conditions in northern countries, might influence the curing as well as the ultimate strength of the stabilised soil. The impact of freeze-thaw cycles on the engineering properties of stabilised soils was investigated with focus on the reduction of strength. In these laboratory investigations, curing took place at temperatures of +4°C with freeze-thaw cycles interrupting the curing period. Variations in the laboratory set up contained different soil types, binders, binder contents, and curing times before the freeze-thaw cycles. The results show, that the strength increases with curing time in spite of the near zero temperature; but for one binder, a strength-over-time development with decrease after 90 days has been observed in the cold curing conditions in the experiments. In general, the strength gained during curing was reduced by freeze-thaw cycles. However, strength was regained during curing afterwards, and reached a higher level of strength than the original soil before stabilisation.

Thermal performance of a proposed group of geothermal piles for supplying the energy demand of a building is studied in this paper. The building is located in the Fort-Garry campus of the University of Manitoba in Winnipeg, MB, Canada. Due to the heat loss of the below-grade envelope of buildings in urban areas, soil temperature rises significantly. The proposed geothermal piles are aimed at re-harvesting the heat leaked into the ground through the basement structure. Further, the thermal performance of the proposed geothermal pile system has been analyzed numerically. One of the most important impediments for wide application of geothermal piles in cold regions like Canada, where annual heat extraction from the soil is higher than heat rejection into it, is the underground thermal imbalance which is widely investigated in this study. Based on the results, the temperature of the soil increases up to 6°C due to the heat leakage of basements of both studied building and its surrounding buildings. Despite the injected heat to the ground due to the building heat leakage, the thermal imbalance occurs in the soil in case of supplying 100% of the building heat demand during the winter and 100% of its cold demand during the summer by geothermal piles which necessitates further consideration for efficient application of geothermal energy using thermal piles in Canada.

Due to common heavy snowfall in winter, concrete structures in cold countries are regularly in contact with water. Hence, concrete undergoes abnormal leaching of ionic species present inside the liquid pores of the material. The leaching slowly degrades the structures and may have an influence on the diffusive properties of the chloride ions, coming from the de-icing salts and responsible for the corrosion of the steel reinforcements present in the reinforced concrete. In this work, an experimental and numerical study is propounded to better understand the influence of the leaching state of cementitious material on the diffusive behaviour of chloride ions. Natural and accelerated diffusion tests were performed on samples of hydrated cement paste and concrete samples with lower chloride concentrations (50 mol/m³). The materials were conserved at different leaching state with care not to degrade the microstructure: safe (S), partially leached (PL), and leached (L). The simulation of those various tests was carried out on the reactive transport software PhreeqC to quantify the chloride diffusion. This numerical model allows distinguishing the influence of the geometry of the material (porosity, tortuosity, constrictivity…) to the chemical reactions occurring between chloride ions and the cementitious phases. It then appeared that chloride ions do not diffuse in the same way depending on the leaching state of the cementitious material. Same observations are made on hydrated cement paste and concrete samples. In a safe material, the chloride ions diffuse slowly than in a leached material. It seems not to be due to the material geometry nor chemical reactions. The numerical model developed confirms this hypothesis as it allows to distinguish and quantify their both influence on the chloride diffusion. This study, therefore, highlights the importance of considering the leaching effects in the prediction model for concrete structure durability in cold countries.

Since 2012, site geotechnical studies have been performed for the development of an LNG storage tank in Fairbanks including the design of several foundation alternatives. The geotechnical effort was phased and included subsurface studies of several potential tank locations and at the existing LNG facility, observations related to prior construction impacts on warm permafrost soils, and shear wave velocity profiling for seismic hazard analyses. In addition to the subsurface studies, a scaled pile load test was performed to better understand the potential pile performance in warm permafrost for a heavily loaded structure. LNG storage tanks are designed to maintain internal temperatures of -160°C, and heaters are installed in thawed soil to avoid the development of permafrost below the LNG storage tanks. Typically, large LNG storage tanks on permafrost soils have been supported on deep foundations with elevated pile caps to provide separation between the storage tanks and ground to avoid aggrading permafrost and associated basal frost heave below the tanks. Because of the seismic demand at the site, a foundation system with a thermal break became very expensive. Several alternatives were considered to maintain permafrost at the site.

Fairbanks Natural Gas (FNG) has been evaluating the need for a new liquefied natural gas (LNG) storage tank since 2012. The new tank is required to support expanded service of natural gas in the greater Fairbanks and North Pole areas of Interior Alaska. Because of the seismic demand, an at-grade mat foundation was selected for this tank over the typical pile supported foundations. LNG is typically stored at temperatures around -160°C and then warmed before passing into service lines. Traditionally, LNG storage tanks constructed on thawed ground include heater systems between the foundation and underlying soil to avoid the generation of permafrost and basal frost heave. In regions with permafrost, LNG storage tanks are generally supported on pile foundations with elevated pile caps that allow for a thermal break between the tanks and soil. The FNG LNG storage tank is one of the first LNG storage tanks constructed on permafrost soils that has been designed as an at-grade foundation. Because the permafrost soils only extend approximately 40 m deep and the site is adjacent to the Tanana River, the aggradation of permafrost would not be acceptable over a 75 year design life. The delicate balance of maintaining warm permafrost was evaluated, modeled, and designed to allow for the construction of an at-grade foundation system. The system balances the cold from the LNG within the storage tank to maintain the permafrost, but not to significantly lower the temperature of the permafrost. The methods and design considerations will be presented.

The hydrology and carbon balance of cold regions are drastically influenced by the presence of permafrost in the subsurface. There is little work in the literature attending to the impact of heterogeneities upon the long-term and short-term evolution of permafrost bodies. This local heterogeneity, however, may be a major driver in talik formation which, in turn, can impact landscape evolution, hydrologic connectivity, and greenhouse gas emission. In this research, a freeze-thaw code based on the non-isothermal phase transition criterion (enthalpy-based) is used for studying the effect of heterogeneity on the soil-water-ice system’s thermal processes. A trust region algorithm is implemented for solving the highly non-linear system of equations. The results of the developed tool are successfully verified against the existing analytical solution for a three-zone one-dimensional medium presented by Lunardini (1985). Using the FEM-based tool developed in this research, two-dimensional freeze/thaw simulations are run in ensembles of spatially correlated heterogeneous soils with spatially heterogeneous freezing points in order to better elucidate the relative impact of various forms of heterogeneity on local permafrost table evolution. The results of the simulations of a domain with stochastically distributed thermal properties illustrate that local heterogeneity has conditional influence on the long-term permafrost body evolution and talik formations.

This paper summarizes the long-term monitoring (2007–2018) of three test sections in the shoulder of the runway embankment of Tasiujaq Airport. The objective of this test site is to conduct a performance review of three permafrost protection techniques: gentle slope, air convection embankment (ACE), and heat drain. Each of these techniques and a reference section were installed on the side-slope of the embankment, over a length of 50 m. The results of 10 years of thermal monitoring have shown that the three methods tested have had positive effects on the thermal regime of the ground. While the convective techniques (ACE and heat drain) extracted enough heat from the ground to protect permafrost, the gentle slope was the most effective with a significant decrease in active layer thickness and ground temperature. In Tasiujaq, crosswinds during winter favour snow accumulation along the embankment; the gentle slope is the best option to minimize this effect and to limit the insulation of natural ground. Air convection and heat drain techniques are dependent on the temperature differential between ground and air to initiate convection. Therefore, those techniques are much more effective in regions where the temperature differential is greater.

Local knowledge, BTS measurements, and observations of interstitial ice suggest the presence of permafrost in talus slopes near Thunder Bay, ON. The nearest known permafrost is 400 km to the north. Mean annual air temperatures in the region are less than 2.5°C, similar to and lower than other locations where permafrost has previously been found in blocky materials. In order to determine whether permafrost exists in talus slopes in the region, ground temperature sensors were installed at the bottom of two talus slopes to measure conditions at the surface and within the talus for two years beginning on 15 October 2016. Interstitial ice at these sites was monitored over the same period in summer and autumn. Mean annual surface temperatures were -4.0°C and -5.8°C and mean annual temperatures in the talus ranged from -4.3°C to -7.3°C. During the winter, talus surface and internal temperatures fluctuated in response to multi-day trends in weather, with mean freezing season temperatures below -9°C. During the thawing seasons, the sites experienced prolonged zero curtains. Mean thawing season temperatures were below 2°C, and lower than 0°C at several internal sensors. Bodies of interstitial ice persisted into the autumn at both sites. The temperature record and observations of the interstitial ice indicated the presence of permafrost at the bottom of one of the slopes.

With changing climatic conditions and increasing infrastructure demands, infrastructure owners, operators, and planners must possess tools to objectively aid their decisions on climate change adaptation and infrastructure maintenance. Risk analysis tools, either qualitative or quantitative, would be very beneficial to select engineering designs and allocate funds for the expected maintenance of linear infrastructure on permafrost. To this end, the paper provides an example application of a newly developed Excel spreadsheet, called Arquluk-RISK, which quantitatively calculates hazard and risk based on site soil, permafrost, and climate condition variabilities. This example focuses on the hazard analysis of total and differential thaw settlement, active layer detachment slides, and culvert collapse and gradient failure for current climate conditions for the airport access road in Salluit, Nunavik (northern Quebec), Canada. The software and analysis includes the variation in hazard due to increasing mean annual air temperature in the coming decades.

Frozen debris lobes (FDLs) within the Brooks Range, Alaska, are elongated, lobate permafrost features that consist primarily of silty sand with gravel, are covered by mature spruce forests, and move primarily through basal shear. Over the last decade, researchers from the University of Alaska Fairbanks and the Alaska Division of Geological and Geophysical Surveys have studied FDLs, determining their current and historic rates of movement, composition, likely formation, and any hazards they pose to the adjacent infrastructure (i.e., the Dalton Highway and the Trans Alaska Pipeline System). Although most FDLs are some distance from the Dalton Highway, the Alaska Department of Transportation and Public Facilities (ADOT&PF) already experiences increased maintenance due to changes in sedimentation within certain streams that intersect the highway. Visual observations of FDL surface degradation suggest that sediment production will increase in the future. This is crucial for maintenance and operation of the Dalton Highway, as it is the only land-based transportation route to the Alaskan Arctic. In this paper we present an analysis of sedimentation along the Dalton Highway. We use two LiDAR-derived digital elevation models (DEMs) from 2011 and 2015 to conduct change detection and estimate volumetric sediment transport from FDLs and associated catchments, and from catchments without FDLs (or NDLs for “no debris lobe”). Results indicate that NDL catchments currently produce 1.5 times as much sediment as FDL catchments, suggesting that FDLs are effective sediment storage landforms. Identifying current sedimentation areas and volumes provides ADOT&PF with a long-term maintenance planning tool.

Simulating permafrost is impeded by the lack of meteorological forcing datasets at most locations of interest. Here, we present the first application of GlobSim, a new Python toolkit that extracts site-level meteorological time series from global atmospheric re-analyses and makes them easily available for forcing permafrost simulations using land-surface models. The software downloads, interpolates, and heuristically scales data to point locations. In this example, we use the model GEOtop and four re-analyses datasets to simulate permafrost in five terrain types that characterize the variability of tundra environments in the Northwest Territories. We evaluated model results using two years of air- and ground-temperature observations from sites near Lac de Gras. The range of observed mean annual ground surface temperatures during the two years was 6.0°C. Results show that the reanalysis data can support permafrost simulations quite well. Compared to individual re-analyses, the ensemble mean improved results for all terrain types. Using the ensemble mean reduced the root-mean-square error by 0.07–1.78°C for mean annual air temperature, 0.10–0.34°C for daily ground surface temperature, 0.11–0.31°C for mean annual ground surface temperature, and 0.08–1.03°C for surface offset. These results demonstrate that reanalysis-driven ensemble simulation is a promising tool for simulating permafrost in remote locations.

Within the Brooks Range of Alaska are slow-moving permafrost-landslide features known as frozen debris lobes (FDLs). These features were originally identified during the construction of the Trans Alaska Pipeline System and the Dalton Highway in the 1970s, at which time they were thought to be inactive. In 2008, members of our research team recognized that FDLs are indeed actively moving, spurring on a long-term monitoring and field investigation program. Over the last decade, we have increased our understanding of FDLs through drilling, sampling, analyzing ground temperatures and strain rates obtained via subsurface instrumentation, measuring surface movement, and analyzing long-term and seasonal movement rates using historic imagery, light detection and ranging (LiDAR), and interferometric synthetic aperture radar (InSAR) data. Our research indicates that FDL movement is sensitive to temperature and water pressure, which is expressed in seasonal fluctuations of movement rates. In an effort to learn more about FDL temperature dynamics, here we explore the interaction between subsurface temperature and FDL vegetation coverage using two-dimensional, finite element thermal modeling. Model results indicate that when a section of an FDL is simulated to have an exposed mineral surface, a through-talik forms within the permafrost after 50 years. As more of the FDL surface is disturbed by movement and transitions to a bare, mineral surface, the size of the talik increases. When the entire surface is bare mineral soil, permafrost conditions are no longer sustainable beneath the FDL. We present comparisons of model results to observed field conditions, and predict surface destabilization for FDL-A.

A physically-based interface model of active layer evolution and permafrost thaw is presented. This computationally efficient, semi-analytical, non-equilibrium solution to soil the freeze-thaw problem is proposed as a component of hydrological models to describe seasonal ground ice, active layer, and permafrost evolution. The model is developed and validated against the Neumann solution and a benchmarked numerical model. Unlike similar semi-analytic models, the interface model does not assume a linear temperature profile. The model is implemented for use in discontinuous permafrost peatlands where soil properties are highly dependent on soil ice content. It is demonstrated that the model is suitable for the representation of active layer and permafrost evolution for one representative year of data. Future applications of the model are proposed such as the simulation of the formation and evolution of taliks (perennially thawed soil in permafrost environments), the stability of permafrost, and many others.

The fast-growing population in the village of Salluit creates important housing and infrastructure needs, on a terrain that has difficult topographical constraints and ice-rich permafrost. Those challenges require regularly updated information on permafrost temperatures, rates of summer thawing of the active layer, and on georisks. There is an abundance and spatially distributed monitoring instruments in Salluit [e.g. thermistor cables, distributed temperature sensing (DTS) with fiber optic cables, and SILA, automatic weather station of the CEN network]. The integration of data in an easy access database will allow monitoring of permafrost behavior and assessment of georisks, particularly active-layer detachment failures, in the community. This paper discusses data integration and the relevance of information on permafrost temperature and climate monitoring for land use planning in Salluit. These data are synthesized into an online database regularly updated and easily accessible. The updated version of the mapping will be available in ArcGIS Online for the institutions and stakeholders involved in the development of northern communities. The overall purpose is to facilitate decision-making towards a sustainable development, offering a support to land use planning, construction, and security assessments.

The Arctic air mass is the cold, dry body of air slowly moving eastwards around the North Pole in the northern hemisphere. Its southern boundary consists of four planetary waves known as the Rossby waves that mark the interface with subtropical air bringing heat polewards. The Arctic air mass is constantly being modified by the addition of heat and moisture over the oceans, as well as by winter cooling over the land masses due to minimal incoming solar radiation and constant reradiation of heat into the atmosphere. The coldest air in winter is located over northeastern Siberia and moves east, cooling Canada. Research in Tibet and Northeast Asia shows that the Late Wisconsin cold event (75–10 ka B.P.) resulted in severe cooling of northeast Siberia and northern Tibet, as well as eastern and northern Canada. Extreme changes in sea level resulted in vast quantities of sea water being sequestered on land primarily as cold-based ice sheets including the Laurentide Ice Sheet, reaching a maximum extent between 30–20 ka B.P. The East China Monsoon slowly redeveloped and a gradual warming took place on both continents after about 20 ka. In contrast, in southern British Columbia, the Late Wisconsin glaciation only began in 29 ka B.P. but continued along the west coast until about 10 ka B.P. This paper explores the relationship of the Late Wisconsin history on the two continents, together with the mechanisms causing the landforms and climatic changes.

The Inuvik Airport access road is a section of the Dempster Highway which extends from the Inuvik Airport to the junction of MacKenzie Road within the town of Inuvik. As a result of an increase in the mean annual air temperature of approximately 3°C to 4°C over the last five decades, the active layer thickness within road embankments in the region has increased considerably. The increase of the active layer led to intensifying various earth processes on the road surface and embankment slopes. In recent years, distress/failures of embankment slopes had been observed at various sections along the Inuvik Airport access road. Numerous transverse cracks were encountered at intervals of 10 m to 40 m along the entire length of the investigated road. Several embankment failures were also observed. Failure of the embankments led to the formation of water ponds and thaw movements/settlement of native terrain. Field investigations via boreholes were carried out to evaluate the causes of the earth processes causing road embankment distress and to develop geotechnical recommendations for the rehabilitation of damaged portions of the road. Rehabilitation methods included excavation of the damaged sections, placement of insulation, and backfilling the excavation with gravel. The paper summarizes the findings of the existing permafrost conditions from the field investigation and demonstrates various types of earth processes observed during the site reconnaissance. The paper also provides rehabilitation options for the damaged embankments.

Climatologists regularly warn that communities underlain by ice rich permafrost are at risk due to climate change. Unfortunately, a formal risk assessment Alaskan community has not been done. The Denali Commission funded a study to assess 187 Alaskan communities to determine the vulnerability of infrastructure to thawing permafrost. According to available data, many of these villages, especially in northern and central parts of the state, are. According to available data, many Alaskan villages, especially in northern and central parts of the state, are in the areas with wide-spread ice-rich permafrost, and one of the main objectives of this study was to identify such communities. A permafrost profile was developed for each community based on available information including scientific publications, maps, satellite imagery and aerial photographs, geotechnical reports, hazard mitigation plans and other community plans and reports, authors’ field data, and personal communications. Coupling these data with anticipated thaw settlement and the impact of that settlement on infrastructure, a vulnerability score was developed for each community allowing the identification of communities with the highest risk of damage due to thawing permafrost.

Peatlands in the Hudson Bay Lowlands (HBL) extend from the sporadic to the continuous permafrost zones. They store ~30 Pg of soil carbon, ~10% of which is sequestered in permafrost. Palsa fields and peat plateaus are dominant features in the HBL of northern Ontario, but pronounced warming trends in the area are associated with accelerated degradation of these features. This research investigated greenhouse gas production potential (CO₂ and CH₄) from HBL peatlands near Peawanuck, ON, in the context of rapid palsa degradation. Active layer and permafrost samples from palsas, and samples from fens adjacent to the palsas were collected at sites exhibiting different degradation rates and patterns, identified via the sequential analysis of historical aerial photographs and recent satellite imagery. The samples were incubated anaerobically at 4°C and 14°C to assess CO₂ and CH₄. In general, CO₂ production potential was higher than CH₄, however the production of CH₄ was extremely sensitive to increased temperatures. Between 4°C and 14°C CH₄ production increased by factors ranging from 6 to 90, whereas CO₂ production consistently increased by a factor of ~2. The production of both gases was higher from fen peat then from permafrost and active layer peat at either temperature when incubated in anaerobic conditions for 225 days. This suggests that higher production rates of CO₂ and CH₄ from thermokarst features compared to intact permafrost landscapes are not only the result of environmental conditions such as wetness and increased temperatures, but also likely a result of organic matter chemistry and bioavailability associated with increased sedge growth following permafrost degradation.

Permafrost degradation often leads to thaw settlements and engineering problems. Convective stabilization techniques have been developed to generate cooling effects to avoid permafrost thawing. However, little information on the design procedures or guidelines can be found. This research is to develop improved engineering tools for the design of convective stabilization techniques. Whether permafrost degradation happens or not depends on the heat balance across the embankment-soil interface. One heat balance chart for conventional embankments and several heat extraction capacity charts for selected stabilization techniques are proposed from a design point-of-view, using heat balance approach. Particular interest was paid to air convection embankment (ACE) and heat drain, two promising methods based on wintertime density-driven convection.

Differential interferometric synthetic aperture radar (DInSAR) is commonly used to assess thaw subsidence in permafrost regions. However, the method is vulnerable to noise, processing strategy, and other environmental processes. In this study, we present a post-processing correction method applied to DInSAR displacement maps over a study area near Rankin Inlet, Nunavut. The correction removes residual noise, and permits quantitative comparison between different DInSAR maps and other data. Our correction method does not require advanced InSAR processing, but requires the presence of stable bedrock outcrops uniformly distributed over the DInSAR scenes. Results show that the method successfully corrects for local errors without drastic deviation from uncorrected maps. By using corrected displacement maps from C-band (RADARSAT-2) and L-band (ALOS-2 PALSAR-2) satellites, we combine seasonal and inter-annual displacements to create a permafrost terrain map that describes current and short-term permafrost conditions. The permafrost terrain map also highlights areas where DInSAR results could preferentially be affected by soil moisture or flooded vegetation. For the Rankin Inlet area, the permafrost terrain map shows that permafrost is relatively stable, with localized high subsidence related to the melting of frost blisters and, to a lesser extent, the melting of segregated ground ice near top of permafrost.

The snow/sun shed is a proven mitigation technique effective in stopping progressive permafrost thawing beneath embankment side-slopes. However, safety concerns and high-construction expenses have prevented the widespread use of snow/sun sheds for embankment protection. To find a better low-cost deployable system that still uses the same cooling principles than the snow/sun shed, a new mitigation technique was tested at Laval University. A series of half pipes were applied on a small-scale embankment slope in a cold room set at -20°C. The temperatures measured in the embankment slope at 0.22 m below the soil surface are: 1) -5.2°C lower compared to the reference embankment when the half-pipes extremities were left open to air circulation; 2) -4.6°C lower when the inlets of the half-pipes were sealed with mineral wool (to simulate snow clogging); 3) -4.2°C when both extremities were sealed with mineral wool. In terms of heat fluxes, the three configurations of half pipe cover tested were between 1.7 to 1.8 times more effective at extracting heat than the reference embankment. Finally, implementing this mitigation technique on the slopes of a road embankment has the potential to induce a significant cooling of soil temperatures.

Terrain mapping has been successfully applied to the planning and design of linear infrastructure in North America since the 1940s. A natural extension of terrain mapping in northern regions is the interpretation and characterization of permafrost and ground ice potential. This application has become increasingly important as climate change accelerates permafrost degradation, affecting the development and maintenance of infrastructure. It is, therefore, critical to forecast changes in permafrost terrain to optimize roadway routing, design, and maintenance forecasting. The accuracy and resolution of permafrost interpretations are increased markedly when based on newly available, high-resolution digital elevation models derived from structure from motion photogrammetry and airborne LiDAR surveys, in addition to traditional aerial photography. Using these resources, we have developed a predictive mapping approach to identify permafrost terrain that is susceptible to subsidence or thaw-induced mass movements as a result of climate change or anthropogenic disturbance. We have applied this approach to proposed resource access road corridors in two permafrost settings in northern Canada: the Coffee Gold Project in unglaciated west-central Yukon and a portion of the Slave Geological Province Access Corridor in formerly glaciated Northwest Territories. Terrain mapping representing current conditions was first produced to establish the distribution of distinct terrain units and indicators of excess ground ice. We then derived predictive mapping representing the variable response of distinct permafrost terrain units to projected climate conditions or disturbance. This mapping highlights the most hazardous areas, which are commonly explained by the surficial geological setting, as a basis for optimizing geotechnical field investigations. It also informs recommendations for roadway avoidance, insulative or resilient road designs, and spatio-temporal allocation of resources for maintenance.

Long-term measurements (1991–2016) from 17 thaw tubes in the Mackenzie Delta region were analyzed to investigate changes in thaw penetration (TP), ground surface (GS) elevation relative to a stable benchmark, and active-layer thickness (ALT). TP increased significantly during the study period at 10 of the sites, at a median rate of 0.5 cm a^-1 (min: 0.2, max: 1.5 cm a^-1). Significant subsidence occurred at 10 sites, at a median rate of 0.4 cm a^-1 (min: 0.2, max: 0.8 cm a^-1). These results indicate long-term regional permafrost degradation and surface subsidence in the western Canadian Arctic. About 5 to 38 cm of permafrost have thawed over 25 years at the sites, and ~5 to 20 cm of excess ground ice have melted. ALT increased significantly at only 5 of the sites and decreased at 4 sites. In ice-rich ground, increases in TP can more than double increases in ALT. For example, at a site near Inuvik, ALT increased by only 19 cm between 1994 and 2016, but TP increased by about 40 cm and was accompanied by 20 cm of surface subsidence. At sites in ice-poor ground, negligible settlement occurs, and increases in TP and ALT are similar. In ice-rich terrain, the degradation of permafrost cannot be detected by probing for active-layer thickness alone.

Predictive ground temperature modelling at permafrost sites rely on calibrated computational models that are inherently dependent on all inputs, including climate data. In a perfect case, a local weather station that measures all inputs required to calculate the surface boundary condition are readily available including air temperature, wind speed, relative humidity, albedo, vegetation thickness, solar radiation, and snow depth. However, if one or more of these inputs are not measured, then assumptions are often, if not always, required. Snow cover, in particular, is one such input for which assumptions are required in many cases. At elevated sites in the eastern Canadian Arctic the ground is covered by snow for most, and occasionally all, of the year which increases albedo and insulates the ground against seasonal heat flux. In this paper the effect of four snow cover functions is examined on near-surface and deeper ground temperatures over a six-year model period. The results show that the snow depth and cover duration play a significant role in the modelled ground temperatures. If snow remains year-round, ground temperatures remain below zero throughout the modeled profile. With zero snow cover, near-surface ground temperatures vary widely in accordance with the uncovered surface boundary. Between the two extremes the maximum ground temperature profiles are similar to the ‘no snow’ scenario, while minimum ground temperatures vary based on the depth and duration of snow cover. The results show snow cover assumptions significantly affect temporal and spatial variation of ground temperatures and need to be carefully selected for predictive modelling.

Permafrost thaw can destabilize terrain, initiate thermokarst processes that alter landscapes, and create geohazards for communities and infrastructure. A robust, standardized methodology was developed to map indicators of thaw-sensitive permafrost terrain, including mass wasting and periglacial features. The method was applied to a 10-km wide corridor centred on the Dempster and Inuvik-Tuktoyaktuk Highways, which are constructed over a wide range of terrain and permafrost conditions. Here we use random forest models, trained and validated with mass movement and ice-wedge polygon inventories, to develop thaw-susceptibility models for two regions along the corridor, Peel Plateau, and Anderson Plain and Tuktoyaktuk Coastlands. Geomorphological and hydrological variables were used as predictors providing insights into the characteristics constraining the distribution of thaw-sensitive terrain. In the Peel region, mass movements have a higher potential of occurring on concave, moderate to steep slopes (7 to 18°) in fluvially-incised valleys. In uplands of Anderson Plain and Tuktoyaktuk Coastlands, mass movements occur on moderate slopes (5 to 15°) adjacent to incised stream channels, and along lakeshores. The ice-wedge polygon model across the forest tundra transition north of Inuvik highlights the northward increase in polygonal terrain with decreasing ground temperatures.

Ground temperatures collected in Northern Canada in the decade following the international polar year (IPY 2007–09) have been compared to the IPY baseline to assess recent change in permafrost thermal state. Since IPY, permafrost has generally warmed with greater changes in temperature (>0.5°C) occurring in colder permafrost of tundra sites than at forested sites underlain by warm permafrost. The permafrost warming over the last decade continues the trend observed in longer term records, at some sites over three to four decades. Trends in permafrost temperature are consistent with those in air temperature although other factors such as vegetation, substrate conditions, and proximity of ground temperature to 0°C are also important in explaining regional differences. Although temperature increases in warm permafrost have generally been of lower magnitude, thaw is occurring at many sites.

Arctic deltas are dynamic and complex environments influenced by the presence of permafrost and affected by a wide range of processes. Erosion may directly impact communities and local ecosystems, while there may be consequences at the global scale such as the release of greenhouse gases. Channel migration and erosion must also be considered in the routing and design of linear infrastructure, including pipelines, roads, and bridges built for oil and gas development on the North Slope of Alaska. Assessing channel migration and erosion helps evaluate future changes, while cryofacies and terrain analysis approaches allow estimation of ground properties over extended areas. We studied erosion rates, and ground loss (areas, volumes) by terrain unit along a major distributary in the Colville River Delta (Alaska), the Nigliq Channel, from 1948 to 2013. We integrated an analysis of digital elevation models with a channel migration analysis and available data on local terrain units and subsurface conditions. The long-term maximum erosion rates from 1948 to 2013 averaged 0.9 m y^-1 and ranged from 0.4 to 3.3 m y^-1. The inactive- and active-floodplain cover deposits experienced the highest erosion (269,960 m² and 150,830 m², respectively); however, the alluvial terrace in the Gubik Formation had the largest ground loss volume due to banks being over twice higher, on average. Eroding the older ice-rich terrain units forming the floodplain toposequence, such as the inactive-floodplain cover deposits, resulted in ground loss volumes of about 208,357 m³ as soil solids and about 833,429 m³ as ground ice. Our study supports the pertinence to integrate terrain analysis and cryofacies approaches in erosion assessment at the landscape scale along a permafrost-influenced deltaic channel.

The Illisarvik Lake basin was experimentally drained in 1978 to study growth of permafrost in the lake-bottom sediments ab initio. Ground freezing began during the first winter after drainage and led to the development of permafrost throughout the lake basin, except beneath a residual pond. This paper reports the range in near-surface ground temperatures in the basin 40 years after drainage. In summer 2016, vegetation and soil characteristics were determined throughout the basin. Snow surveys were conducted in April 2017. Since drainage, seven principal vegetation communities (units) have developed in the basin: bare ground, sparsely vegetated soil, grass meadow, sedge marshes, and three shrub types. Characteristic snow depths in these units and in tundra surrounding the basin were 16, 27, 38, 62, 52–127, and 47 cm, respectively. Illisarvik’s coastal location ensures that there is abundant snow to fill the high snow retention capacity created by tall shrubs and basin topography. Mean annual ground temperatures (T_g) at 25 cm depth were recorded by miniature data loggers in 2016–18 in the different vegetation units at 10 sites within the basin and the surrounding tundra. T_g in 2016–18 ranged from -0.1 °C beneath tall dense willows to -5.6°C in bare ground. T_g in tundra surrounding Illisarvik was -5.2°C. The factors most strongly associated with the variations in temperature were snow depth and soil moisture. Although near-surface ground temperatures at Illisarvik initially decreased as permafrost was established after drainage, the basin soils are no longer cooling due in part to increases in snow depth with the growth of vegetation.