Cold Regions Engineering 2015: Developing and Maintaining Resilient Infrastructure

To investigate the influence of temperature, water content, and dry density on ultrasonic wave velocity, a serial of ultrasonic tests were conducted on frozen silty clay by using the supersonic test meter. In the mean time, compressive strength of frozen silty clay was measured under various temperature conditions. Results indicate that the ultrasonic wave velocity rapidly changed in the range of −1°C to −7°C, due to the frozen pore water, and that their relations can be described by the same formula. The ultrasonic wave velocity increased with an increase in dry density and showed a good linear relationship with dry density. Ultrasonic wave velocity increased with an increase in water content until the water content reached the critical water content. In terms of the ultrasonic wave velocities versus unfrozen water content, it was found that they have linear relationships. Based on the ultrasonic tests and strength tests results, it is found that, as the compressive strength increased, ultrasonic wave velocity increased and both of them increased with the temperature. In terms of the ultrasonic wave velocities versus temperature and compressive strength versus temperature, the relationship can be set up between ultrasonic wave velocities and compressive strength. Based on the previous research and experimental data, the relationship between ultrasonic wave velocity and frozen silty clay strength was obtained through analysis. The fitting curves show that good correlations exist between them.

In the North Atlantic Treaty Organization Reference Mobility Model, the bearing capacity of frozen soils is a function of vehicle weight and frozen layer thickness. This relationship is based on the failure criteria of elastic plates extended to vehicle bearing capacity of ice sheets. In practice, this is found to be very conservative. A new study to investigate different approaches is underway. As part of this study, we examine how inherent soil physical properties change as a function of ice content, temperature, and engineering soil type. The final step will be to determine how these parameterizations affect the different bearing capacity formulations and to compare them to field data.

A series of indoor tests were conducted to study the changes of soil particles and pores under freezing and thawing cycles. Testing results showed that grain breakages of coarse particles occurred during freezing and thawing cycles, resulting in an increase of the Atterberg limits and specific surface area of the soil samples. Meanwhile, the pore size distribution, tested by the mercury intrusion method, was also changed during the cycles; macro pores increased, mini pores reduced, and micro pores remained roughly unchanged. The interaction of soil particles (solid phase), soil pores (gas phase), and soil water (liquid phase), namely soil’s three phase components, is discussed to explore the change mechanisms of soil structures under freezing and thawing cycles.

Environmental reclamation of mine waste disposal facilities often requires their confinement under engineered soil covers to control gas migration and water infiltration. In temperate climates, covers with capillary barrier effects (CCBE) are successfully used to control oxygen flux; these covers require a fine-grained material that acts as a moisture-retaining layer. In Nordic environments, where such natural fine-grained soils are not always available, soil or crushed rock-bentonite mixtures could be used instead. A key parameter in the design and performance evaluation of CCBE is the effective diffusion coefficient of oxygen (D_e) of the moisture-retaining layer. This paper aims at presenting the development of a laboratory column testing and interpretation method to evaluate the D_e of a crushed rock-bentonite moisture-retaining layer in a CCBE and the effect of freeze-thaw cycles on D_e. The numerical approach used to analyze the experimental diffusion test results allowed obtaining D_e for various saturation conditions observed in the moisture-retaining layer. Preliminary results show that the initial measured value of D_e increased by two orders of magnitude after 3 freeze-thaw cycles. Steady-state flux calculations based on the obtained D_e showed that despite a good initial cover performance, the capacity of the tested cover to act as an oxygen barrier is reduced in the longer term. This study demonstrates that the proposed laboratory column oxygen diffusion test could be an effective tool to assess the performance of CCBE to control oxygen migration when exposed to cold climate conditions.

Gravity measurements were made using a Scintrex CG-5 Autograv gravimeter in permafrost terrain conditions where bodies of buried ice were expected. The main objective was to assess the feasibility of using gravimetric technology to detect massive ice bodies at Dry Creek, Yukon Territory, Canada. Tests at 11 gravimetric survey lines and 10 boreholes were performed during the summers of 2013 and 2014. Residual anomaly profiles provide a quick first estimate of the amount of ice in underlying soil strata. A mean anomaly of −0.10 mGal was found near a thermokarst, south of the Dry Creek rest area along the Alaska Highway. The cryostratigraphy comprises at depth an ice-rich diamicton covered by massive ice with suspended silty inclusions and an overlying layer of glacio-fluvial gravel. At the base of a small glacio-fluvial hill deposit, on the southeast side of the road, a mean anomaly of −0.260 mGal was found. A massive ice body of 9.3 m of maximum thickness was drilled through. Since drilling is planned after gravimetric surveys, it is possible to assess whether or not this technique is effective for detecting sub-surface ice features. This paper presents an overview of the site, the gravimetric detection technique employed, and gravimetric and borehole test results and analysis.

Frozen debris lobes (FDLs) are slow-moving landslides along permafrost-affected slopes. Within the Dalton Highway corridor in the southern Brooks Range, Alaska, we have identified 43 FDLs, with 23 occurring less than one mile uphill of the Dalton Highway. FDL-A, which is the largest and closest FDL to the Dalton Highway, was just over 42 m away from the highway embankment when measured in August 2014. Since the completion of a preliminary subsurface investigation in 2012, we continue to collect subsurface temperature and inclinometer data, to measure surface movement rates, and to make field observations, which reveal the dynamic nature of FDLs. Significant rainfall during the summer of 2014 caused a deepening of the active layer on FDL-A and exposed massive “infiltration” ice in the head scarps of two retrogressive thaw slumps on its surface. The infiltration ice occurs in bands associated with transverse and longitudinal cracks, and the 2014 observations indicate that FDL-A may contain more massive ice than previously indicated. FDL-A moves mostly through basal shearing and through slow to moderate flow, which is highly dependent on temperature. The average rate of movement of FDL-A from 2013 to 2014 was 1.3 cm day⁻¹. Comparing this value to the trend of historic rates indicates that the overall rate of movement of FDL-A continues to increase.

In permafrost areas, environmental changes, such as infrastructure, building, and climate change, have effects on the thermal regime of soil and can initiate permafrost degradation. As a result, this will lead to the degradation of the mechanical properties of the soil. Thus, good knowledge of permafrost characteristics is essential to make the right decisions during the design and construction phases of a project and to anticipate potential problems related to climate change. The goal of this project was to improve our capacity to characterize thaw-sensitive permafrost by developing a drilling tool that is able to carry out in situ tests. In partnership with the Mechanical Engineering Department of Laval University, an oedometric core barrel was designed, and a prototype was built. As the core barrel is modular, it is easy to clean and maintain. Once the barrel has penetrated frozen soils, thawing is initiated by an electric heating element. A pneumatic cylinder then allows the user to set a consolidation pressure, and drainage occurs radially along the first 20 cm of the core. The drained water is discharged at the top of the drill hole, and information on the thaw consolidation behavior is recorded during the test. The complete testing procedure can be made during the in situ drilling operation. In order to validate the testing procedure, laboratory tests were made in pure ice and synthetic permafrost reconstituted in barrels. The testing program has allowed improvement of the initial design of the equipment as well as the test procedure. The reliability of the thaw settlement/consolidation tests was evaluated for fine and coarse soils.

A number of theories have been proposed in order to model the thaw consolidation behavior of frozen soil. However, they are not valid over a wide range of complex problems because of simplifications made in their formulation. The relevance of the development of an extension to the existing theory of thaw consolidation is discussed in this paper. The current available thaw consolidation theories are presented, focusing on their own specific insights into the thaw consolidation behavior of soil. The two main components of a thaw consolidation theory, namely thawing and consolidation, are discussed with special regards for the shortcomings of the currently used theories. The coupling of these two components into a unified theory is examined. Brief discussions on two-dimensional problems and on additional considerations regarding thaw consolidation precedes the conclusion.

Remote sensing was used as a site investigative tool for the portion of the Hudson Bay railway embankment underlain with discontinuous permafrost in northern Manitoba, Canada. Imagery from Landsat 5’s Thematic Mapper were analyzed to observe changes in land surface temperatures, vegetation cover, and water content in vegetation canopies over the past three decades. The Landsat image analyses show evidence of the occurrences of significant wildfires near the railroad over the years. Temperature data indicate that land surfaces that have been burned are approximately 20°F warmer on average than the surrounding unburned areas. The data also show that significant amounts of vegetation have been destroyed by these wildfires and that fire scars and temperature anomalies often persist for several years. Satellite imagery has also been used to map the severity of these wildfires by calculating normalized burn ratios before and after the fires and then solving for the differenced normalized burn ratio. Previous studies have shown that fire damage results in the removal of the insulating organic layer of the permafrost and exposing the mineral soil, which causes a decrease in thermal conductivity and thereby increases the active layer depth. Such increase in the depth of active layer typically results in ground subsidence and can be detrimental to engineered structures, such as rail embankments. However, ground subsidence is not exclusive to regions affected by fire and, therefore, more ground data, such as ground penetrating radar, maintenance records, and track geometry survey data are needed to validate this relationship.

The Qinghai-Tibet Railway traverses 550 km of permafrost region. After embankment construction in 2003, considerable detrimental permafrost-related embankment deformations developed along the railway. Based on field monitoring data collected from 2005 to 2012, typical embankment deformations, as well as their mechanisms along the railway were analyzed, taking into account the thermal regime and ice content of the subgrade soil layers. Results showed that frost heave of the embankment was slight and only occurred on a few in-cut roadbeds and air convection crushed rock embankments (ACCEs) in colder permafrost regions (< −1.5 °C). It mainly developed with upward movement of the permafrost table under the roadbed during the first 3–4 years after embankment construction. Settlement of embankments was significant, and some already threaten the railway’s safe operation. As ACCEs successfully cooled the shallow subgrade and underlying permafrost, embankment settlement was relatively slight and acceptable. Settlement of traditional sand gravel embankments (TSGEs) was generally greater than that of ACCEs. In warmer permafrost regions (> −0.7 °C), thaw consolidation of the underlying permafrost resulted in significant settlement on TSGEs, some of which reached 40 cm.

Relocation of the Barter Island Airport included a new 4,500-foot long runway, taxiway, apron, and 1.4 miles of access road near the Village of Kaktovik on Barter Island, Alaska. Barter Island lies approximately 115 miles east of Deadhorse along the Arctic Coast of Alaska. The relocated airport and access roads were constructed over tundra in a previously undeveloped area with ice-rich, frozen soils below the tundra. To provide a runway and road surface that was stable and resilient to rising global temperatures, the embankment sections were designed to prevent thawing of the underlying materials after completion. Finite element, thermal modeling was conducted using TEMP/W to design the embankment and insulation thickness. Subgrade soil temperatures were recorded before and during construction. Data collected during the first year of construction were used to calibrate the model and validate that the proposed design will resist the expected increases in global temperatures. The calibrated model parameters are compared to estimates from published relationships, and the measured thaw depths are discussed.

In Finland, increases in the maximum allowable operating speed on railways have led to stricter smoothness requirements for rails. Despite continuous rehabilitation of the track structures, decreased speed limits have been required due to seasonal frost action. To improve the understanding of frost action phenomena in railway structures, a real-time in-situ monitoring system was installed at 14 sites within the Finnish railway track network for the purpose of measuring temperatures in the track structures and vertical displacements of selected railway sleepers. Based on 5 years of data collected from 2009 to 2013, during which time the maximum frost depth was observed to range from 0.9 m to 2.4 m, multivariable regression models for predicting the maximum frost depth at the instrumented sites were developed. Several factors were shown to influence the maximum frost depth, including latitude, longitude, air-freezing index, rainfall, elevation, and ditch depth. With comparatively high R² values of 0.73 and 0.87, the resulting regression models may provide satisfactory utility for predicting maximum frost depth at sites similar to those that were instrumented for this research. When considered with other information such as track structure thickness, predictions of maximum frost depth can be useful for development of site-specific reasons for observed frost problems in railways.

The long-term performance of a pavement structure largely depends on the underlying soil foundation. When poor subgrade soils are encountered, many highway agencies employ “remove and replace” or chemical stabilization techniques to strengthen the subgrade. Due to rising cost of good materials and traditional stabilizers such as lime, cement, and asphalt, highway agencies are looking for recycled materials for subgrade stabilization. These materials include cement kiln dust (CKD), lime kiln dust (LKD), fly ash (FA), and concrete fines (CF). etc. Previous studies on these recycled materials have demonstrated the immediate benefit of their usage in building a stable platform for construction of upper pavement layers. However, the long-term durability of subgrades stabilized with recycled materials has not been completely studied. This study is aimed at understanding the freeze-thaw durability of subgrades stabilized with recycled materials. An extensive laboratory study is underway to characterize the freeze-thaw durability of laboratory soil samples stabilized with CKD, LKD, FA, and CFs. Laboratory samples were subjected to different number of freeze-thaw cycles in a laboratory freezer and the unconfined compressive strength (UCS) of those samples were measured after 0, 1, 3, 7, and 12 cycles. This paper examines the preliminary results of the short- and long-term benefits and risks of using recycled materials for subgrade stabilization in cold climate areas. Only CKD has shown long-term stabilization benefits from the above materials. However, laboratory freeze-thaw testing of CKD stabilized soils showed significant strength loss after 12 cycles. Field performance of a pavement subgrade stabilized with CKD was also examined during this study and showed retained subgrade strength after 6 years of service life.

The purpose of this research was to better establish a correlation between the results of freeze-thaw and vacuum saturation durability tests, with particular respect to mass loss in the freeze-thaw test, for cement-treated base and subgrade materials. Seven materials were used in the laboratory testing, including five aggregate base materials and two subgrade soils. Materials were stabilized with various cement contents and subjected to three different performance tests, including the standard freeze-thaw test, the standard 7-day unconfined compressive strength (UCS) test, and the vacuum saturation test. Correlations between the results of these tests were investigated, with the primary measure of durability being the rate of mass loss. The correlation between freeze-thaw mass loss rate and the baseline UCS had an R² value of 0.87, and the correlation between freeze-thaw mass loss rate and the UCS after vacuum saturation had an R² value of 0.89. In both cases, increasing UCS was associated with decreasing mass loss. Corresponding to the threshold of 14 percent mass loss in the freeze-thaw test, values for baseline UCS and UCS after vacuum saturation were determined at confidence levels of 70, 80, and 90 percent, and the resulting values are recommended for design purposes. The researchers recommend UCS testing after vacuum saturation as a viable alternative to the freeze-thaw test. The standard 7-day UCS test could also be used but may yield false positives for some materials, as shown in this study. The correlation between baseline UCS and UCS after vacuum saturation is strong, with an R² value of 0.92; on average, the UCS after vacuum saturation was 90 percent of the standard UCS in this study. Other correlations with freeze-thaw mass loss rate were not as strong.

The purpose of this research was to assess the residual structural capacity of the cement-treated base (CTB) layer on Interstate 84 in Weber Canyon following premature fatigue cracking of the overlying asphalt layer. Field testing included falling-weight deflectometer (FWD) testing by Utah Department of Transportation personnel and portable falling-weight deflectometer (PFWD) testing, dynamic cone penetrometer (DCP) testing, and coring by research personnel. The results of the testing indicated that the average modulus and unconfined compressive strength (UCS) values measured in the wheel path were consistently lower than the corresponding values measured between the wheel paths; reductions in structural capacity in the wheel path probably occurred as a result of asphalt cracking, water ingress, freeze-thaw cycling, and continued trafficking of the pavement in these conditions. Despite these effects, the average CTB modulus, California bearing ratio (CBR), and UCS values were still considerably higher than those of typical unbound granular base materials. Specifically, the average CTB modulus values measured during the spring using the FWD in the eastbound and westbound lanes were determined to be 1699 and 852 MPa (246.4 and 123.6 ksi), respectively, while the average CTB modulus values measured during the fall using the PFWD in the eastbound lane were 2609 and 3378 MPa (378.5 and 490.0 ksi) in the wheel paths and between the wheel paths, respectively. Furthermore, based on DCP testing, the average CBR value in the wheel path of the eastbound lanes was determined to be 198. Finally, the average UCS values were determined to be within or just above the range of 2070 to 2760 kPa (300 to 400 psi) recommended by the Portland Cement Association for the 7-day design strength of CTB.

Laboratory tests on small soil specimens under cold weather conditions found that curing temperature significantly influenced the strength of unsuitable soil improved by adding a stabilizer. The improved soil was found to develop little strength when the ambient temperature was below 0°C. However, we considered that the temperature inside a full-scale embankment might not decrease as much as in the small specimens in the laboratory tests because the ambient temperature is expected to have a smaller effect on the soils in the full-scale embankment than on the small soil specimens. In this study, we conducted a field experiment to investigate the extent of freezing and the strength improvement of soils that have been modified with stabilizers. In addition, we measured the effects of a quicklime-mixed soil blanket placed on the constructed embankment. The field experiment confirmed that the embankment underwent little freezing while the soil was developing strength.

In order to limit heat intake in the ground underneath pavements, high albedo surfaces can be used in cold regions to mitigate permafrost degradation. In this study, experimental sections at Site Experimental Routier de l’Université Laval (Québec, 2014), on the Alaska Highway (Beaver Creek, Yukon, 2012 and 2014 and at km post 1786, Yukon, 2014), and in Tasiujaq (Nunavik, Québec, 2015) were used to document the effectiveness and durability of high albedo surfacing materials. The test sections were equipped with thermistors and data loggers recording surface temperatures. Albedo and skid resistance were also monitored at these sections. In addition to the experimental sites, several albedo measurements were made on asphalt surfaces to develop a relationship between albedo and pavement age.

Many roads in seasonal frost areas experience costly damage as a result of freeze-thaw processes. In order to reduce damage, road management agencies apply Spring Load Restrictions (SLRs), which restrict the allowable load on a road during the critical time interval when the pavement is most vulnerable to damage. Methods of determining SLRs include use of set dates and/or visual inspection procedures, conducting falling weight deflectometer (FWD) testing, monitoring subsurface temperatures and/or moisture, and use of predictive models (based upon atmospheric weather data) to predict subsurface frost-thaw profiles. Regardless of which approach is used, a challenge in SLR posting is that many miles of roadway must be posted based on a very limited set of observations and data. This paper presents data from two closely spaced field test sections: one located in a very sunny area and the other located in a shaded area. Other than solar exposure, conditions at the two sites were considered the same. During the two-year study period, subsurface temperature monitoring showed substantial variation in frost-thaw patterns, particularly with regard to the end of thaw dates, which occurred 30 and 38 days later at the shaded site compared to the sunny site. FWD testing conducted at the sites also showed similar differences in thaw weakening and recovery patterns. Results of this study suggest that variability in solar radiation can have a significant impact upon appropriate SLR posting dates, particularly with regard to removing the SLR. Additionally, the project suggests a need for more cost-efficient monitoring systems, so that variability might be better quantified and accounted for by agencies charged with making SLR posting decisions.

The structural behavior of flexible pavement in cold regions is greatly affected by environmental factors and traffic loads. The main objective of this study was to better understand the response of pavement structures during thawing and to better predict the loss and recovery of the bearing capacity as a function of the evolution of the thaw and temperature in the pavement. Two identical test sections were used; one was built in the geotechnical laboratory of Laval University and one was located at the Laval University Road Experimental Site (SERUL). Each layer of the tested sections was instrumented with strain, stress, moisture, and temperature sensors. In the laboratory, a heavy vehicle and environmental simulator, which can control the air temperature on the pavement surface, was used to apply real traffic loads and control temperature. A temperature of −10°C was used for freezing, and a temperature of 10°C was used for thawing. The carriage speed was set a 5 km/h, the tire pressure was set at 700 kPa, and loads of 5000, 5500, and 4000 kg were tested to simulate standard, winter premium, and spring load restriction conditions. At the SERUL, a falling weight deflectometer (FWD) was used to simulate heavy loads. The results indicate that the freezing of a given structural layer reduces the strains and stresses in the layer, as well as in the underlying layers. After one freeze-thaw cycle, the reduced moduli in unbound materials indicate that some damage occurs during freezing and thawing. Also, strain increases significantly when the thaw front penetrates into the pavement and at the beginning of summer when the rise of temperature reduces the stiffness of the asphalt concrete layer. Finally, we noticed that, during freezing, a 10% load increase induces a 10% increase of strain and stress in the pavement structure.

Low-temperature cracking is one of the major causes of pavement distress during the winter season. Research has shown that measuring the flexural stiffness of asphalt mixture beams using a bending beam rheometer (BBR) is a good way to control the low temperature properties of asphalt mixtures. However, before such a test is adopted as a specification, the repeatability and reproducibility of the testing protocol need to be verified. This study uses the draft American Association of State Highway and Transportation Officials protocol established by Marasteanu et al. to evaluate the variability of results from two separate laboratories, one at the University of Utah and one at the Utah Department of Utah central laboratory. The purpose of this research is to examine the reproducibility of test results across different laboratories. A series of gyratory asphalt mixture samples were examined based on mixture designs from Utah highways; each of the samples was cut into thin asphalt mixture beams and divided evenly between the two laboratories. Each set of tests shared the same variables for both laboratories and were conducted on the same day. The testing was performed at a temperature of -18°C, which corresponds to the low temperature performance grade plus 10°C. One variable was altered between each pair of tests, namely the amount of time between cutting of the gyratory asphalt mixture sample and running of the test. The variations in time conducted after cutting included four intervals: two days, three days, one week, and two weeks after cutting, which highlight the effects of any steric hardening for both short and long periods on the repeatability of results. The results of these tests demonstrated consistency across both laboratories. These results also indicate that steric hardening has no effect on testing samples after 48 hours and that the test results are repeatable for the same asphalt mixture specimen. Therefore, the BBR test can be used as a low-temperature specification for asphalt mixtures.

Pavement performance in cold temperature regions is a concern to highway agencies. Laboratory methods need to be established to test the cold temperature performance of asphalt mix designs. Research conducted at the University of Utah has shown that testing asphalt concrete mixtures using the bending beam rheometer (BBR) is a viable method to measure low temperature performance. Data collected from field cores were used to develop performance relations. However, testing field cores from already constructed roads does not prevent poor performance mixes from being placed on the road. A better approach is to use laboratory-compacted samples from field mixes that are already used for volumetric quality control. While this still relies on material obtained at the time of construction, it is closer to the ultimate goal of evaluation of materials at the mix design stage for cold temperature performance. Typically, volumetric cylinders are gyratory compacted to an air void content of 4% by mass, while field cores target an air void content between 6% and 7%. The question arises in the variability of BBR results from air content ranging between 4% and 7%. For this research, gyratory cylinders were compacted at varying levels of compaction in order to achieve a range of air voids to evaluate stiffness measurements with the BBR. Different binder contents were also tested, with compaction level held constant and binder content varying. For varying air voids, the 60 and 120 second creep modulus was seen to decrease by as much as 30% within the 6% air void range. The m-value for varying air voids was not affected. Results also showed that, at binder content levels close to optimum, no noticeable change was observed in beam measurements. In addition, the m-value was seen to be independent of binder content.

Corn and soy based bio-derived warm mix asphalt (WMA) additives are currently being developed. In the past, additives with similar properties have been shown to successfully reduce the mixing and compaction temperatures of asphalt by as much as 30°C. Isosorbide distillation bottoms (IDB), a WMA additive, is a co-product from the conversion of sorbitol to isosorbide, where sorbitol is derived by hydrogenating glucose from corn biomass. Past research utilizing IDB at several dosage rates showed there was improvement in low temperature binder performance using the bending beam rheometer (BBR) between dosage rates of 0.5% and 1.0% by weight of the binder. This research investigates whether low temperature improvement occurs with several new bio-derived material additives that have similar properties to materials used in past research, as well as compares their performance to two commercially available/bio-derived WMA additives from the forest products industry. In cold regions of the United States, the main observed distress in asphalt pavements is low temperature cracking. Characterization of binder performance at low temperature is possible with the use of the BBR. For asphalt mixtures, characterization is more challenging at low temperatures due to the response from the aggregate phase of a mixture. To examine low temperature performance of hot mix asphalt (HMA) and WMA, the semi-circular bend (SCB) test was used to characterize the fracture properties. SCB tests showed that additive choice was a statistically significant factor in fracture energy properties but not for stiffness and fracture toughness. All of the new additives were successfully used at reduced mixing and compaction temperatures and did not adversely impact low temperature mix fracture properties of WMA when compared against the control HMA. However, improvement of fracture energy was observed when comparing the epoxidized esterified fatty acid additive to the other five additives used in this work.

Concrete overlay pavements are expected to have reduced crack widths when the concrete mixture contains fibers. However, it is still unknown how much the crack widths can be reduced due to the fiber-bridging effect in these fiber- reinforced concrete (FRC) overlays. A previously constructed full-scale thin FRC overlay was investigated for this study. This full-scale experiment has only been subjected to environmental loading for 5 years. Field observation results showed that crack width increased as the cracked-joint spacing increased for the same FRC material. This study investigates determining the average crack width and debonding length through a numerical study and is validated by the field project. A two-dimensional finite element model was developed to verify fiber-bridging effect and the amount of layered-interface debonding in FRC overlay structure. A cohesive behavior was defined for both the joint location and the underlying interface between the FRC and existing pavement. The vertical deflection, crack widths, and debonding length were studied based on the modeling inputs of varying fracture energy and elastic modulus of the FRC overlay, as well as varying interface tensile bond strength and elastic foundation stiffness. The developed model matches the measured crack widths from the experimental field project. Additional data from the numerical study indicate that crack opening widths, vertical joint deflection, and debonding length all decreased as the fracture energy and tensile bond were increased.

Thaw degradation of permafrost is increasingly becoming an issue for existing and new construction in the northern regions of the globe. A modular tubular foundation system for permafrost and discontinuous permafrost has been developed and continues to prove its worth by providing stability to buildings in even the worst soil conditions. This paper describes a foundation system as it applies to medium to small buildings ranging from 1,500 to 15,000 square feet. For the last 20 years, this modular foundation system has been used in a wide variety of northern soil conditions for both new and retrofit construction. It is now also being used in flood regions such as the San Francisco Valley and has recently found application at a problem soil location near Regina, Saskatchewan. This foundation concept accepts the unreliable and ever-changing bearing capacity of the soil and gives strength to the building in its entirety. The foundation and building combined become one unifying torsionally stable entity. Case studies to show how the foundation system works are discussed for applications in Alaska, the Canadian Northwest Territories, and San Francisco.

Active hydronic cooling systems have several advantages over passive cooling methods for preservation of thaw-susceptible permafrost soils in arctic regions. Currently, passive cooling systems are primarily used in maintaining the integrity of foundations in permafrost soils. Some limitations of passive cooling systems include high construction costs and reliance on weather conditions to operate. Passive cooling systems do not operate in the summer and allow the active layer to thaw each season. With the recent occurrence of more extreme weather events and warming air temperatures throughout the arctic, passive systems do not provide sufficient cooling capacity for some applications. An active cooling system can be programmed to deliver energy during the summer months when it is needed and can be designed to prevent the active layer from thawing. By maintaining a frozen state for the site soils, the energy requirements of the system are greatly reduced due to the elimination of the phase change of moisture within the soil. When the cooling load is reduced to sensible heat only, the system can be powered by electricity produced from a small photovoltaic power plant. Other advantages of active cooling systems over passive cooling devices include lower material and freight costs, lower construction costs due to the ease of installation, and more flexibility in construction scheduling. In February of 2014, the Alaska Native Tribal Health Consortium installed an active cooling system under a lift station located in Old Kasigluk, a rural Alaskan village. The system consists of a low-pressure cooling coil made of cross-linked polyethylene tubing laid out in a grid above the existing permafrost. Coolant is circulated through the coil by a self-contained chiller. Heat is absorbed from the surrounding soils by the circulated coolant. Ground temperature data from this system were collected and are presented in this paper.

The stability of piles used for the Qinghai-Tibet Power Transmission Line (QTPTL) is important for the operation of the line because this type of foundation is generally used in areas with unfavorable geological conditions. Intensive heat influence of casting temperatures and hydration heat means that the refreezing of cast-in-place piles obviously affects the schedule and cost of the project. The refreezing process was simulated on a cast-in-place pile based at tower 1443 of QTPTL in the warm and ice-rich Touerjiu region, Qinghai-Tibet Plateau. The results show that the thermal energy, originating from the casting temperature and hydration heat of cement, dissipates mainly through lateral heat flux, resulting in the warming and thawing of surrounding soil. The stability of the pile will dramatically decrease during the process. It was also found that the dissipation of the thermal energy is affected by the heat conductivity and water/ice content of the surrounding soil. The refreezing process of a 1-m-diameter pile in Touerjiu region continues for about 67 days. The maximum thermal influence range is about 9.8 m for a single pile, and group pile effects exist for towers of QTPTL in Touerjiu region. The duration of the thermal impact of casting temperature and hydration heat of a single pile is about 630 days.

Australia has three permanent bases on the Antarctic continent that are occupied year round: Casey, Davis, and Mawson stations. For the expeditioners at these stations, adequate shelter is essential to survival, and these buildings must be engineered to withstand the extreme weather conditions that Antarctica generates. The design of these buildings needs to address not only the severe climatic conditions, the large variation between the internal and external temperature, and the annual freeze/thaw of the permafrost, but also construction limitations at such a remote site. The structural approach of buildings has evolved over the years due to improved understanding and developments in technology. The original post-tensioned buildings were based on a series of prefabricated huts (surplus WWII stock) that were trialed at the sub-Antarctic outposts established at Macquarie and Heard Islands in 1948. The station rebuilding program that commenced in the 1970s addressed many of the constraints that faced the designers of Antarctic buildings and resulted in the distinctive, large steel-framed, cool-room panel style AANBUS buildings. Containerized buildings have also been used over the past 30 years, providing an alternative, more cost-effective approach to the AANBUS buildings. Most recently, a large fiber composite building was commissioned at Davis to provide living facilities for up to 120 personnel. This building uses the inherent strength within large fiber composite panels to minimize the steel framing requirements. This paper details the various building approaches and the motives for the structural improvements undertaken at the Australia’s Antarctic stations over the past 60 years.

Methods for evaluating snow loads on roofs are described within building standards and codes such as American Society of Civil Engineers 7 and the National Building Code of Canada. These recommendations are often simplified and generic in order to be applicable to most structures and, as a result, do not account for the unique aerodynamics that can occur around a structure. In addition, these codes and standards do not address serviceability concerns, such as accessibility to building entrances, nor identify where mechanical air intakes may be prone to snow ingestion as is common to buildings located in cold regions. Scale model testing within an open channel water flume allows for the rapid assessment of the building aerodynamics and snow drifting conditions for the purposes of design. This paper presents snow accumulation patterns representing a snowfall event from a single direction for a building with commonly seen geometries including roof steps, arched roofs, and a projecting tower with mechanical penthouse. Multiple test directions are presented to illustrate the influence of wind directionality and resulting building aerodynamics on snow accumulations at grade level, on roof areas, and where mechanical intake equipment is often sited.Parapets, canopies, and recommendations for mechanical air intakes for reducing problematic snow accumulations are presented and discussed.

Snow loads for structural design are calculated using the product of the ground snow load and several coefficients that transform the ground load to a roof load. The basis for the ground snow load is a statistical analysis of the annual extreme snow-water equivalents. This statistical analysis traditionally uses the lognormal distribution and is based on an initial analysis of 76 weather stations in the northeastern United States between 1952 and 1980. Since the original study by Ellingwood and Redfield, additional data have been collected, thus enabling a reanalysis of ground snow load data for 113 weather stations with at least 40 years of data.In reevaluating the data, the authors first conducted a statistical analysis for trends or nonstationarity at all stations. The ground snow load data were then evaluated using multiple extreme-value distributions at each station. An Anderson-Darling statistical goodness-of-fit test was applied to each analysis at each station, and the results were compiled to determine which extreme-value distribution is most appropriate for analyzing snow loads. Conclusions showed that 90 percent of the stations analyzed display no significant temporal trend in ground snow load over the four-decade period of record and confirm the findings of Ellingwood and Redfield that the lognormal distribution is a reasonable model for estimating ground snow load for structural design.

The harsh environmental conditions and the remoteness of Antarctica dictate that traditional building form cannot be economically and safely applied to building construction. Limitations such as the shortness of the Antarctic summer construction season, a single annual resupply voyage, and the reduced availability of plants, equipment, and skills all influence the design of any new infrastructure. Over recent years, a new living quarters building has been designed and constructed at Davis station, Antarctica, using a hybrid building technique. This building comprises exterior fiber-composite thermal panels secured to an internal steel frame. The design of the structural steel frame and foundation system was tailored to exploit the inherent panel strength, thus resulting in less material usage and lower transportation and erection costs as well as time savings on site. However, the fiber-composite panels did create their own specific challenges. The use of fiber-composite panels and a steel building frame resulted in considerable variation in thermal expansion and contraction. With the building construction being undertaken at below-freezing temperatures, the steel frame was predicted to increase in size considerably more than the fiber-composite panels as the building was heated to operational temperature. Furthermore, the impact of the tremendous difference in temperature between the inside and outside on external wall cladding meant that material selection required careful consideration. These thermal challenges were among the many issues that needed to be addressed before the new building could be completed. The building has now been operational for the past 5 years and is exceeding original expectations.

The objective of this research was to measure both the in-situ moisture content and diffusivity (in the form of electrical conductivity) of both lightweight and normal-weight concrete bridge decks over time. Two lightweight concrete bridge decks and two normal-weight concrete bridge decks constructed as part of the Interstate 15 Corridor Reconstruction project in northern Utah were selected for instrumentation and monitoring. Sensors that could measure volumetric moisture content, electrical conductivity, and temperature were installed in each bridge deck prior to placement of the concrete, and air content, slump, and wet unit weight measurements were obtained during concrete placement. Sensor readings were taken frequently throughout the next approximately 2 years, and laboratory compressive strength and rapid chloride permeability tests were also performed. The measurements of 28-day compressive strength indicate that both the lightweight and normal-weight concrete mixtures exceeded the specified design strength and were also similar to each other. In rapid chloride permeability testing, both types of concrete changed from “high” chloride permeability at 28 days to “very low” chloride permeability at 6 months and 1 year, but the amount of current passed by the lightweight concrete was 25, 45, and 79 percent higher than that passed by the normal-weight concrete at 28 days, 6 months, and 1 year, respectively. The sensor readings showed that the lightweight concrete bridge decks were 33, 18, 33, and 19 percent wetter, on average, than the normal-weight concrete bridge decks at 28 days, 6 months, 1 year, and 2 years, respectively. The sensor readings also showed that the lightweight concrete bridge decks were 4 percent less conductive than the normal-weight concrete bridge decks at 28 days but became 107, 177, and 267 percent more conductive, on average, than the normal-weight concrete bridge decks at 6 months, 1 year, and 2 years, respectively.

In cold regions, chloride-based deicing salts are commonly applied to roads and bridges during winter to melt ice. The objective of this work was to demonstrate the utility of a new technology, vertical impedance testing, for assessing the condition of concrete bridge decks treated with membranes and asphalt overlays to reduce chloride-induced corrosion of the reinforcing steel. The vertical nature of the impedance testing allows interrogation of all layers from the deck surface down to the reinforcing steel, specifically permitting evaluation of the protection against chlorides provided by any deck surface treatments, the full depth of the concrete cover, and any rebar coatings. Spatial variations in vertical impedance measurements on a bridge deck in Wendover, Utah, were compared to the occurrence of cracking in the asphalt overlay, half-cell potential values, and chloride concentrations measured at specific locations before deck rehabilitation. The data were also compared to the occurrence of actual deck repairs completed after the asphalt overlay and membrane were removed. The impedance data were well aligned with the distress and half-cell potential data and were used as a basis for strategically selecting locations for coring and chloride concentration sampling, which enabled further interpretation of the impedance data. Of the 29 patches corresponding to delaminations identified by the contractor, nine were positioned at locations originally characterized by cracking of the asphalt overlay surface, 18 were positioned at locations characterized by low impedance magnitude, and eight were positioned at locations characterized by uncertain half-cell potential classifications. The vertical impedance testing method therefore shows great promise as a tool for evaluating the protection against chlorides provided by an asphalt overlay system. Furthermore, contour plots of impedance magnitude may possibly be used to estimate the scope of work, including the location and extent of deck repairs, that may be required during deck rehabilitation.

Chloride-induced corrosion of reinforcing steel in concrete structures is a leading cause of deterioration of highway infrastructure in cold regions, where the source of chlorides is usually deicing salts applied to roads and bridges during winter to melt ice. The objective of this work was to evaluate applications of lithium silicate and a combination of lithium silicate and silane for sealing concrete barrier walls exposed to chloride-based deicing salts. The procedures followed in this research involved selection of three field sites for topical applications of lithium silicate and silane, chloride concentration sampling before and after treatment, and chemical analysis of the samples. The field sites were all located along the newly constructed Mountain View Corridor in northern Utah and were evaluated after each of the first two winters. The results of the statistical analyses completed in this research indicate that treatment with silane and lithium silicate and treatment with lithium silicate by itself provide 79.9 and 42.4 percent reductions, on average, in chloride concentration, respectively, compared to the control, which was not treated. In addition, the data indicate that the chloride concentration of the deeper lift was, on average, 64.2 percent less than the chloride concentration of the shallower lift, where the depth ranged from 0 mm to 13 mm (0 in. to 0.5 in.) and from 13 mm to 25 mm (0.5 in. to 1.0 in.) for the shallower and deeper lifts, respectively. Finally, the data indicate that the chloride concentration increased by 258.0 and 330.2 percent, on average, after the first and second winters, respectively, compared to the baseline values measured before the wall sections were exposed to chlorides. Evaluation of the permanency of the treatments will require continued monitoring for several more years.

In cold regions, as the soil temperature drops below the freezing point, available water starts to freeze and form ice lenses. The growth of ice lenses depends on many variables, including temperature, soil type, capillarity, availability of water, proximity of the ground water table, and applied load or overburden pressure. Ice growth causes heave in the soil, which may precipitate extensive damage to structures such as pavements, shoulders, utility lines, utility poles, and even unprotected foundations. Most existing mechanistic-empirical frost heave prediction models are based on two theories, capillary (primary frost heave) and frozen fringe (secondary frost heave).Unfortunately, none of the models have received universal acceptance. The capillary theory has some limitations, which result in inaccurate prediction of frost heave. The frozen fringe theory involves complex models that require numerous input variables, which are often unavailable or expensive to collect. This paper addresses the modifications that are made to one of the secondary frost heave models. The modified model uses simplified input data and a statistical frost depth model that is developed during the study using measured frost depth data from the state of Michigan. The use of the statistical frost depth model simplifies the solution and improves the accuracy of the results. Finally, the modified model is evaluated using the pavement and shoulder frost heave data collected in the state of Michigan.

The ground anchor method for slope stability is widely used for cut slopes and walls as either a permanent or temporary stabilization of ground in cold regions. However, we have observed deformation of top steel plates, failure of concrete frames, and even pull out of wires due to over tensioning forces, all possibly caused by the frost heave of ground during low temperatures. We do not have an appropriate design method or code in Japan to take into account the frost heave force acting on ground anchor wires when the ground is supposed to be frost susceptible. In this paper, a design method is introduced to estimate the frost heave forces acting on ground anchors as a required additional force, using a well-used frost heave model, results of laboratory frost heave tests, and several assumptions on the elasticity of frozen ground. The estimated values are compared to the observed failure data at the ground-anchored slope, and the method is evaluated as a reasonable approach.

Foundation structures in cold regions can be subjected to uplift forces, such as basal heave forces and tangential heave forces, that are caused by the freezing of frost-susceptible soils. Tangential heave force refers to the upward shear force that acts along the outer surface of the foundation after the adfreeze bond between the pile and soil is broken due to the frost heave of the soil. Deep foundations in cold regions need to be designed so that the shaft resistance provided by soils below the frost depth is greater than the tangential heave force induced by soils above the frost depth. The magnitude of the tangential heave force should typically be determined by multiplying the tangential heave stress by the outer surface area of the foundation within a frost depth. Therefore, tangential heave stress is one of the key parameters in design of deep foundations in cold regions. However, values of tangential heave stress reported in the literature show large variability. Part of this variability results from the conceptual confusion about the terms “tangential heave stress” and “adfreeze shear strength” and also from the different test methods and procedures used to measure tangential heave stress. This paper carefully reviews previous research on determination of tangential heave stress. The test procedures and methods are described and classified, and test conditions such as foundation material, soil type, frost depth, and ground temperature are described in detail when such data are available. Although some sources of the large variability in reported values of tangential heave stress can be resolved, more research is clearly needed to improve the fundamental understanding of ice-soil-foundation interactions.

An innovative approach to mitigate frost heave problems in flexible pavements is to inject a two-part expanding polymer at the bottom of the subbase. As the polymer expands, it creates an insulation layer that minimizes heat loss from the profile and prevents the frost front from entering the subgrade. The technique has been used in a section of Wyoming highway WY-70 6.4 km west of Encampment, WY. A two-year study measured road surface deviations and temperatures in the soil profile. The frost heave over a 30-m long section was reduced from greater than 75 mm to less than 17 mm. The maximum frost penetration depth was determined in five holes over two seasons using the measured temperature data in the road/soil profile including boreholes with 0, 25, and 75 mm of expanded polymer. These data were compared to depths predicted by the Modified Berggren Equation. The standard deviation for the ten estimates was 52 mm over a range of freezing depths from 500 mm to 1100 mm. The maximum error of prediction was 82 mm, while five of the ten errors were less than 20 mm. It was determined that the polymer behaved like volumetric latent heat. The technique appears to successfully predict the frost depths well enough to use as a predictor in design. However, these results are based solely on an analysis using Uretek 486 STAR #3 structural polymer at this site and time period.

The snow roads at McMurdo Station, Antarctica, are the primary transportation corridors for moving personnel and material to and from the airfields servicing intra- and inter-continental air traffic. The majority of the road system is made of snow overlying a snow and ice subsurface. However, at the Scott Base Transition (SBT), the aggregate road leading from Scott Base transitions from the landmass of Ross Island on to the ice shelf and becomes a full depth snow road. Because of the transition between materials, the topography of the area, and extensive use during the austral summer, the SBT is prone to problems unique to that portion of the McMurdo road system and requires specific maintenance activities to remain passable during periods of high temperatures. The SBT area is divided into two subsections. One is the land transition, a soil- or aggregate-surfaced road underlain by permafrost, and the other is the ice transition, a snow-surfaced road underlain by snow and ice. The two sections of the SBT need entirely different construction and maintenance techniques to maintain road surface conditions that will support vehicle traffic. This paper presents some of the issues at the transition area along with maintenance and drainage control measures to alleviate them.

Pavement surface temperature is an essential requirement for the winter maintenance decision-making processes when determining suitable deicers and optimal application rates for transportation facilities such as parking lots. Currently, there are very few services/methods available to directly measure the pavement surface temperature. One method, the Road Weather Information System (RWIS), has less utility for parking lot and sidewalk maintenance purposes due to the operational constraints and high cost of using the RWIS service. This paper presents the results of a two-year field study focused on developing parametric and non-parametric models to forecast pavement surface temperature in parking lots based on a rigorous investigation of its correlation with common meteorological variables. The models were developed using available metrological data alongside measured pavement temperatures obtained through field observations. This study also evaluates the effects of different types of pavement (asphalt, interlocking bricks, and portland cement concrete) on pavement surface temperature. Evaluation results show that the developed models are able to predict pavement surface temperatures in different winter weather conditions with acceptable accuracy.

The highway agencies in snowy regions are constantly looking for new approaches for winter maintenance operations. These approaches include a search for new equipment, new materials, or improved methods for winter operations. Improved methods and materials could provide safer driving conditions with improved mobility during winter storms. The use of performance measures to measure the effectiveness of winter maintenance operations is critical to highway agencies to select the best methods. Several performance measures for winter maintenance were developed in the past based on material usage, equipment usage, and other input-based quantities. However, the traveling public is always keen on outcome-based quantities such as travel time, travel speed, and travel safety. Since vehicle speeds are significantly reduced during winter storms, performance measures based on traffic speeds seem to be good indicators for winter maintenance operations. In this study, average and minimum traffic speed during winter events are studied as a case study to use as performance measures for winter maintenance operations. Traffic-speed based performance measures were obtained by analyzing archived speed data of University of Maryland’s Regional Integrated Transportation Information System (RITIS). RITIS stores thousands of traffic speed data from multiple sources and archived them in their databases. Data was analyzed for 2012-2013 winter season for I-96 and US-23 roadways in Livingston County, Michigan.

Optimal and sensible salting for deicing operations in transportation facilities is an indispensable need, since salting operations consume a significant amount of resources and pose significant challenges to infrastructure and the environment. To realize optimal salting, a thorough understanding of the snow melting performance of salt is required. This understanding can then be used to develop optimal salt application rates, providing potential reductions in material usage and cost. This paper presents the results of a three-year field study focused on developing optimal salt application rates that apply an understanding of the physical snow melting process on empirical evidence. During the field tests, snow melting performance data, along with maintenance and weather data, were collected in the winter seasons of 2011-2014. With the collected data, a mechanistic-empirical model was developed to determine the recommended application rates for parking lots and sidewalks. The model developed through this study is the first of its kind and is a valuable tool for effective snow and ice control in parking lots and sidewalks. This research also outlines a solid framework to develop optimum application rates for other kind of transportation facilities, such as the road sector.

Joint Task Force North conducted Operation NUNALIVUT 2014 during March and April of 2014 in the vicinity of Resolute Bay, Nunavut Territory, Canada. The aim of the exercise was to develop force projection capabilities and further knowledge for operating in an austere and remote environment while demonstrating capability in the Arctic. As part of this exercise, the 109th Airlift Wing (109AW), New York Air National Guard, demonstrated the capabilities of the LC-130 Hercules in support of and in coordination with the Royal Canadian Air Force and the Engineering Research and Development Center, Cold Regions Research and Engineering Laboratory (ERDC-CRREL). The 109AW is the U.S. Department of Defense’s only ski-capable tactical airlift unit. The goals of the skiway exercise were to test skiway reconnaissance and construction techniques for austere polar environments and to provide LC-130 ski-landing and snow field combat offload resupply to Canadian arctic ground forces. The reconnaissance portion of the mission was conducted by personnel from the 109AW and engineers from ERDC-CRREL between March 18 and 22, 2014, and was supported by the 440 Squadron CAF (CC-138 Twin Otters). Camp setup and runway construction began April 12, 2014, followed by LC-130 landing and combat offload operations shortly after. This project demonstrated joint operational capabilities for Arctic search and rescue (SAR) and science support. It also supports ERDC-CRREL research efforts to generate geospatial and weather focused search algorithms for suitable landing and drop zones in austere environments.

The Port MacKenzie Rail Extension project is an approximately 51.5-km-long rail spur extending south from the existing Alaska Railroad mainline in Houston, Alaska, to Port MacKenzie on the north end of the Cook Inlet. The rail spur alignment crosses largely undeveloped land and approximately 8 km of poorly drained, boggy wetland areas. Many of the wetland areas are incapable of supporting construction vehicle traffic during the summer season. To facilitate embankment construction in these wetlands during the summer, an approach to constructing the base of embankments over firm, frozen ground during the winter (winter embankment base stabilization (WEBS)) was developed. Several configurations to the WEBS construction were considered using soil fill and geosynthetics. A test section was constructed and instrumented using horizontal slope indicators and vertical thermistor strings during the first winter season of construction for four variations of fill thickness and reinforcement. The results of the test section and observations during construction of the WEBS during the first summer construction season were used to refine the approach for subsequent construction seasons. After three construction seasons, a significant amount of real-world performance and construction observations were available to evaluate the effectiveness of the WEBS over seasonally frozen ground. Additional comparisons of the WEBS construction approach to several embankments constructed in wetlands under summer conditions were also available. This paper provides settlement and ground temperature data collected at the WEBS test sections, observations of WEBS performance, recommended construction approaches over seasonally frozen ground, and a review of the efficacy of the recommended approaches. Conditions where WEBS should be utilized and lessons learned are discussed.

The Utah Department of Transportation completed the Utah County Interstate 15 (I-15) Corridor Expansion (CORE) project in an unprecedented 35 months, making I-15 CORE the fastest billion-dollar public highway project ever built in the United States. In an area like Utah, where a cold dry climate prevails, construction activities tend to taper off during the winter. On the I-15 CORE project, however, cold weather construction practices were incorporated throughout all levels of the project to accommodate year-round construction. The 35-month project flew through two winters that routinely saw temperatures drop below 0°F. Construction of portland cement concrete pavement, hot mix asphalt, mechanically stabilized earth walls, and bridge structures continued even during these cold periods. In order for continuous construction to proceed during these colder periods, the planning and staging of summer activities was scheduled to set up a queue of winter activities that were inherently less sensitive to the low temperatures and weather conditions. In addition, construction materials less sensitive to temperature drops were designed or selected for use during the winter months. With the aid of innovative techniques and materials including maturity meters, non-frost susceptible materials, tenting, ground heaters, blankets, and hot water, the project moved on, even allowing for a 2011 Christmas Eve pavement placement. Although cold weather construction activities tend to cost more, the I-CORE project was completed six months ahead of schedule and $260 million under budget. The objective of this paper is to present a review of the cold weather construction practices, techniques, and lessons learned on the I-15 CORE project in the form of two project-specific case studies.

McMurdo Station watershed in Antarctica is one of the southernmost basins that annually experiences active water flow during the austral summer. This runoff, primarily from snowmelt, has daily and seasonal fluctuations. The flow fluctuation and variation depend on the air temperature and on many other factors. At times, extreme runoff has occurred at McMurdo Station such that water overflows across the roads and bypasses the culverts, creating disruption and massive erosion. Knowing when the peak runoff occurs is critical for operation and maintenance of the channels. We conducted an analysis of indicators relating the air temperature and cloud cover to flow rate to quantify when significant flow occurred. Flow data taken during austral summers 2009–2010 and 2010–2011 were used in the analysis. Based on the correlation between the change in accumulated thawing degree-days and cloudiness expressed as clearness, the time delay in the peak discharge can occur between 4 and 14 days after a peak temperature. Relating temporal indicators and flow records, a relationship between real time data and the need for maintenance personnel to implement mitigation factors could be achieved.

Hydropower development has resulted in efficient and inexpensive power throughout the world. The construction of large reservoirs allows for the control of river discharge to meet the electric power demands of a region but also leads to alteration of the natural hydrologic cycle of the river. Hydropower development can result in changes to discharge levels, sediment transport, riverine and riparian habitat, and water quality.In cold regions, the ice regime must also be considered and understood prior to development. This paper describes the typical ice regime on cold regions rivers and how the natural processes of ice formation, growth, and breakup impact fish habitat and other resources. In addition, the paper reviews the documented impacts of hydropower development on cold regions rivers resulting from changes to the natural hydrologic cycle, changes to the ice regime, and the resulting changes to fish habitat and other resources. Numerical modeling has been used to predict potential changes and impacts from the development of hydropower projects in cold regions. Two examples of past modeling efforts are reviewed with respect to their performance in identifying changes to the ice regime.

The Fargo-Moorhead Metropolitan Area Flood Risk Management Project, located at Fargo, ND, and Morehead, MN, is to include an aqueduct to carry the flow of the Maple River over a proposed diversion channel. The aqueduct is 250 ft long with an internal width of 50 ft. A V-shaped low-flow channel is built into the floor slab at the center of the channel and is 12 ft wide. The aqueduct will operate throughout the winter when frigid conditions will cause ice to form. This study quantified the amount of ice that forms in the aqueduct under different winter operating scenarios. To achieve this, the study developed an aqueduct flow and ice simulation model composed of five modules. These modules determine the water surface profile through the aqueduct, the water temperature resulting from the interaction of proposed bed heaters and the surface ice conditions, the formation of bed ice by heat conduction through the aqueduct to the outside air, the formation of surface ice through heat transfer from the water surface to the atmosphere, and the interaction of the bed and surface ice.In addition, a HEC-RAS and a finite-element thermal conduction model of the aqueduct were used. The HEC-RAS model was used to determine the aqueduct’s downstream water surface elevation boundary condition. We also used the HEC-RAS model to verify the open water flow estimation of the aqueduct model. We used the finite-element thermal conduction model to develop a 2-D simulation of the thermal conduction through the aqueduct cross section. The thermal conduction model allowed us to analyze the heat flow through the aqueduct structure under different flow conditions, heating elements applications, and thermal insulation applications. The model simulated flow through the aqueduct based on the conditions for each day for the winters of 1995 to 2013 for a variety of operating scenarios.

The Alaska Energy Authority (AEA) is currently in the study phase of a long and complex federal licensing process under the Federal Energy Regulatory Commission (FERC) for the Susitna Watana Hydro Project. The Proposed Study Plan, filed with FERC in July 2012, included 58 individual studies that cover everything from geology and soils to water resources, fish and aquatic resources, wildlife, recreation, subsistence, and transportation. The integrated studies will help determine the impacts of the proposed hydropower operation on the Susitna River basin. The development of hydropower on a cold region river like the Susitna entails significant changes to the natural hydrologic cycle as well as the ice regime of the river. The Ice Processes on the Susitna River Study was designed to provide an understanding of the existing ice regime, how the river freeze-up and breakup processes progress over the October to May ice season. This paper describes the existing freeze-up processes, ice cover progression, ice cover changes, and breakup dynamics but also discusses the variability of these natural conditions. The expected changes to the ice regime due to the proposed Susitna Watana hydropower operation include later freeze-up, higher flows during the winter, and earlier but more controlled breakup. These changes are discussed along with how they could affect other resources along the river.

A pipeline integrity dig was recently completed during the early winter months of 2013 in the Upper Peninsula of Michigan. In addition to snowfall, extreme temperatures, and difficult access, the integrity investigation required excavation within a designated National Wild and Scenic River flowing into Lake Superior. The integrity investigation required an excavation 9 feet deep and 16 feet in length to expose a section of 30 inch pipeline. The excavation extended out approximately two thirds of the way into the river, requiring several design considerations and extensive environmental permitting. During the initial design phase, two main methods were evaluated for excavation support and river diversion, including sheet piling and cofferdams with trench box support. Due to the high gravel and cobble content of the riverbed, sheet piling was ruled out, and a HEC-2 water profile analysis program was utilized to predict the water elevations of varying storm events for cofferdam placement. Upon completion of design, permitting was approved over the next 12 months by seven different government agencies. The final approval was received in late 2012, and mobilization to the project site commenced in early 2013 due to the nature of the integrity investigation. The contractor, United Piping Inc., completed the project safely and successfully while dealing with temperatures ranging from −18 to 42 degrees Fahrenheit, with wind chills dropping to −42 degrees Fahrenheit. This paper details the initial site evaluation, conceptual plans, hydraulic design, and environmental permitting, as well as the unique construction techniques and safety practices employed to successfully complete the project.

In permafrost regions, buried oil pipelines have a substantial thermal impact on the surrounding permafrost due to the large temperature difference between the oil and ground. The change in the thermal regime of the permafrost may trigger frost heave and thaw settlement of the pipeline, and can even destroy the pipeline. In this paper, an example of parallel-buried pipelines is performed, and a numerical method is employed to simulate the thermal impact of pipelines on permafrost foundations for both ice-poor and ice-rich permafrost with various kinds of distances between parallel pipelines. The results show that the thermal effect caused by the operation of pipelines can increase the temperature of permafrost, as well as cause the underlying permafrost foundation to thaw gradually. The thermal impact of parallel pipelines on the permafrost foundation depends on the distance between the parallel pipelines, ice content of the permafrost, initial permafrost temperature, and so on. The degree of influence on each other decreases as the distance between parallel pipelines increases. With an insulated pipeline that has been in operation for 50 years, the thaw depths under the parallel pipelines, with distances of 5 m, 10 m, and 15 m, increase by 1.4 m, 0.4 m, and 0.1 m compared to the single pipeline in the ice-rich permafrost district with the average ground temperature being −0.5°C and the ice content being 35%. Nevertheless, there is no difference between the single and parallel pipelines if the distance is more than 20 m. The recommended distance between parallel pipelines in this district should be greater than 15 m. Different permafrost districts should set separate recommended distances, and the corresponding protective measures should be made outside the recommended distance.

Wind turbine towers built in warm permafrost usually adopt steel pile group foundations due to construction cost and structural safety. This foundation may be softer than expected.In addition, the fundamental frequency of the tower-foundation-soil system fluctuates as the ambient temperature and ground condition changes significantly from season to season in cold regions. Therefore, it is possible, particularly for tall towers, that the fundamental frequency may match the operational frequency in the starting or braking cases or during normal operation; hence, resonance between the tower-foundation system and the rotor may occur. This paper simulates the resonance situation by numerical methods and compares it with field monitoring data. An aerodynamic model was built for the rotor system to simulate its interaction with the wind and provide dynamic loads for the wind turbine tower-foundation-soil system. P-y, t-z, and Q-z curves were used to model the interaction between the pile foundation and the permafrost. Modal analysis shows that the tower fundamental frequency is very close to what is observed in the field data. Time history analysis with the wind load as input on the tower top shows resonance is possible when the rotor operates at a speed around 50 rpm; the peak acceleration on the tower top can reach 0.5 g and peak displacement can reach 20 cm, both of which agree with field observation.A tuned mass damper (TMD) is proposed to reduce the peak acceleration and displacement. Computer models show that a properly designed TMD can be effective in reducing the resonance response and has potential to lengthen the service life of the wind turbine.

In January 2014, a freezing fog weather event moved through an area in the state of Washington, near the Columbia River, affecting several utility lines and facilities. As frost began to accumulate on the structures and wires, the loads supported by the structures increased. A partial failure of the primary load supporting system for one section of a 230 kV transmission line was discovered by maintenance crews, and a temporary solution was implemented. Upon investigation the following day, it was discovered that the temporary solution had failed, and a 1.75-mile section of the line had collapsed. An engineering consultant was mobilized to investigate the collapse and determine the cause and mode of the failure. A review of the design details was also performed to determine if a design flaw contributed to the collapse. This paper discusses the forensic investigation process, the findings of the investigation, and the results of the detailed design review. Recommendations to avoid a similar collapse in the future are also presented. This paper is of international interest for all areas subject to similar ice loading situations. Readers will become familiar with the forensic investigation process and learn how to use the investigation results to develop proposed improvements to design criteria.

Climate change issues specific to the northern tier states and Alaska are related to the active layer, the timing and magnitude of precipitation in the form of snow, the gradual (permanent) warming of the ground temperature, and an increase in the frequency of extreme events (e.g., two successive, abnormally warm summers or an abnormally wet and heavy snowfall). Climate is changing in the cold regions of the United States, but there is significant uncertainty regarding the magnitude of the change over the design life of the systems and elements of our built environment. It will be difficult to reliably estimate the change that will occur over several decades. The prediction of future extreme events and their frequency of occurrence have even greater uncertainty and less reliability than projections of long-term trends in temperature or precipitation. Downscaling does not reduce the uncertainty inherent in global climate model projections and most likely would increase the uncertainty. Engineers should develop a new paradigm for engineering practice in a world in which climate is changing but cannot be projected with a high degree of certainty. Engineers should use low-regret, adaptive strategies such as the observational method to make a project more resilient to future climate and weather extremes. Engineers should also seek alternatives that perform well across a range of possible future conditions.

In the coming decades, climate change will have significant impacts on the long-term performance of the road network of Quebec, particularly during winter periods. This study quantifies the effect of climate change expected in winter, specifically focusing on the effect of a decrease in the freezing index and an increase in the number of winter thaw episodes. First, milder winter temperatures will have a positive impact by reducing pavement damage caused by frost heaves. Increased duration of life of about 6–17% is expected for the middle of the century due to milder winters. Also, an expected increase in the number of winter thaw events is likely to have a negative impact on pavements, increasing damages by permanent deformation in the granular base and by fatigue in the asphalt concrete layer. Triaxial tests were conducted to evaluate the performance on permanent deformation of different grain-size distribution of base materials subjected to repeated winter thaw. The triaxial tests concluded that by mid-century, flexible pavements in Québec will experience a 7 to 13% reduction in service life regarding permanent deformation during winter partial thaws.

Qualitative analysis processes are currently used to design and allocate maintenance monies for linear infrastructure on permafrost. The routing and maintenance locations are generally selected using a qualitative process, with probabilities and consequences of each potential failure mode evaluated using a scalar rating system. A quantitative risk assessment utilizes calculated values of failure probability and consequence. In either analysis method, the values of probability and consequence are multiplied to determine a risk importance factor, which is used to rank and analyze each risk. While qualitative analysis methods have been used for many years, there is a push within the engineering community towards probability-based methodologies, quantifying the analysis process. This paper presents a review of probabilistic methods used to analyze geotechnical properties and calculation uncertainty, problems and failure modes of embankment-supported infrastructure on permafrost, and risk analysis methods. This review is an initial step in the development of a tool and methodology for quantitative risk assessment of linear infrastructure on permafrost; a brief discussion of the research plan is also included.