Journal of Cold Regions Engineering

The resilient modulus of a base course granular material is an important input parameter for pavement design and analysis. In recent decades, numerous studies have been performed to characterize and model the resilient behavior of base course materials under unfrozen conditions. In cold regions, frost heaving and subsequent thawing significantly affect the resilient behavior of base course materials. Due to the complex nature of the problem, relatively less effort was dedicated to characterize and model the resilient behavior of base course materials after seasonal freeze-thaw cycles. Among the limited studies, very often the soil specimens were prepared in an open system with free water access to simulate the frost heave, which represented the worst-case scenario in terms of stiffness reduction during thawing. Sometimes omnidirectional freeze tests were performed to simplify the testing procedures. In reality, soils in the field often experience one-dimensional freeze and thaw. When the permeability of the soil is very low, the groundwater table is far from the freezing front, or the freezing temperature gradient is high, the freezing process can be considered to be in a closed system (i.e., limited or no water exchange). The closed system represented the best-case scenario in terms of stiffness reduction during thawing, which has rarely been investigated. Hence, an in-depth understanding of the seasonal resilient behavior of base course materials in a closed system is essential for cold region pavement design and analysis. In this study, repeated loading triaxial tests were performed to investigate the effects of nonplastic fines content, moisture content, temperature, thermal gradient, and freeze-thaw cycling on the resilient modulus of unbound granular base course materials under seasonal frost conditions. Soil specimens were prepared in the laboratory using a one-dimensional frost heave chamber with temperature–thermal gradient control. Specimens were subjected to a closed-system freezing (undrained) condition. Test results were analyzed and discussed, and models were developed to predict granular materials’ resilient moduli as a function of the state of stress, temperature, moisture, and fines content to complement the previous study.

The pulsed nuclear magnetic resonance (P-NMR) method is commonly used to determine unfrozen water content in frozen soils. Traditionally, unfrozen water content is calculated using first return data from the free induction decay (FID) signal intensity (SI); however, these data may contain both ice and liquid water responses, thus overestimating unfrozen water. To address this, the authors used the normalization method for calculating unfrozen water. First, the authors refined a P-NMR testing system for greater temperature control. Next, testing using two P-NMR instruments at different facilities yielded repeatable unfrozen water measurements to within 2.6% of each other. Results from a desorption test indicated excellent agreement (with an average difference of 0.33%) between P-NMR-derived unfrozen water and physical gravimetric water content data. Finally, comparing results from the normalization method to the first return data indicated that calculated unfrozen water in a frozen soil is up to 3.3 times greater for a given temperature using the first return data versus the normalization method. Because this difference is significant, the authors recommend further investigation using an independent method to confirm the results.

At the onset of winter in cold regions, border ice may form along the banks of a river and grow outward toward the center of the channel. This type of transient ice process is not well understood, and current empirical models of border-ice growth are not universally applicable from site to site. This may be in part attributable to a lack of understanding of the flow characteristics beneath a partial ice cover, because a very limited number of studies have investigated this phenomenon. To help address this knowledge gap, an experimental program was developed at the Hydraulics Research and Testing Facility at the University of Manitoba, Canada. A 14-m-long, 1.2-m-wide rectangular channel was constructed, and a simulated ice cover was installed on each side wall. A set of four experiments was designed to quantify the effects of channel-bed and border-ice roughness on the flow characteristics within a partially covered rectangular channel. Detailed streamwise velocity measurements were taken using an acoustic Doppler velocimeter beneath the ice, as well as within the open-water portion of the channel. It was found that roughness had a significant impact on flow redistribution beneath the ice cover by reducing flow beneath the cover and increasing flow in the open-water section. A rough surface was shown to decrease water velocity adjacent to the rough boundary while increasing the applied shear stress on the rough boundary. A corresponding increase in water velocity adjacent to the opposite smooth boundary and decrease in shear stress was observed. This flow and shear-stress redistribution may impact border-ice growth rates (both laterally and in terms of thickness) as well as sediment and ice erosion and deposition.

In Alaska and other permafrost regions, cut slopes are often required in order to achieve roadway design grades in ice-rich permafrost areas. However, excavation of a cut slope and subsequent exposure to sunlight destroy the existing thermal balance and result in degradation of ice-rich permafrost. Uncontrolled erosion and runoff, as well as slope failure of cut slopes, resulting from thawing ice-rich permafrost can cause environmental distress that is not acceptable by many environmental laws. This study investigates three potential environmentally acceptable thermal-erosion mitigation techniques to address the regulatory concerns raised by current practices. Four test sections, using 0.3 m wood chips, coconut blanket, coconut blanket and Tecco mesh, and 0.3 m crushed rock, respectively, were constructed at the Dalton Highway 9 Mile Hill in interior Alaska. Different sensors were installed to measure changes in the temperature and moisture in the four test sections with time and evaluate the effectiveness of the different thermal-erosion mitigation techniques. A weather station was also installed to monitor climate information at the test site. The thermal erosion of the cut slope was evaluated using a photogrammetric method. This paper presents results from the field monitoring period. The effectiveness of different thermal-erosion mitigation techniques is also discussed.

The use of water-saving appliances and heat exchangers is becoming increasingly popular to decrease water consumption and recover energy from preheated water. However, such in-household changes can bring particular implications for subarctic rural areas, in terms of solids deposition in sewers and drops in performance of wastewater treatment plants (WWTPs), because these are already experiencing diminishing wastewater flows due to depopulation and seasonal dips in wastewater temperature resulting from infiltration into sewers. Hence, this study has considered two communities in Sweden, postulating three different cases with various scales of retrofitting and usage. The results indicate that the decrease in in-pipe velocities when all households are retrofitted with water-saving appliances could be counteracted by sewer relining, but not by the inclusion of a conventional estimate of infiltration. However, for the case in which retrofitting was combined with decreased usage of the appliances, the decrease in self-cleansing capacity could not be counteracted. The retrofitting of heat exchangers under shower trays in all households did not have a significant effect on treatment processes at the WWTP.

Berming is a common nationwide practice in the United States for pavement shoulder maintenance, especially for states located in cold regions. Competent berming helps to improve the load support capacity of the pavement shoulder and prevent vehicle drop-off accidents. The durability of berm materials is compromised by snow plowing operations during the winter season. A nationwide survey of state departments of transportation shows that it is highly desirable to improve the effectiveness and safety during berming operations; compaction of berms is widely believed to improve their resistance to snow plowing, which will also lead to longer lasting berms. To evaluate the performance of alternative berm materials and compaction procedures, experimental studies were conducted on four common types of berm materials to evaluate the effects of compaction method (i.e., Proctor and vibratory compaction) and compaction energy. The experimental results indicate that vibratory compaction is effective for crushed limestone, but less effective for recycled asphalt pavement (RAP) material. Natural soil berm material is not well compacted by vibratory compaction. Heat treatment of RAP up to 60°C did not increase its interparticle adhesion. Sixteen trial sections that include combination of four types of berm compaction equipment and four types of berm materials were placed along two interstate highways routes. The berm compaction equipment studied include the berm monster, two-wheel vibratory roller, side-mounted roller, and pull-behind roller. Observations show that a side-mounted roller provides better compaction for both vertical edge and safety edge pavements. RAPs show a similar behavior under compaction as crushed limestone in the field. Tack coating significantly improves the stiffness of the berm and retains berm materials from erosion. Recommendations are provided to ensure effective and safe berm compaction, which will lead to longer-lasting berms to mitigate cold region pavement maintenance efforts.

A methodological study of modeling runoff from rain-on-snow events was conducted using the northern Swedish city of Kiruna as a test case, with respect to physiographic, drainage system, and the current and projected future climate data. Runoff simulations were carried out with the PCSWMM, which is a geographic information system (GIS) supported version of the U.S. EPA Storm Water Management Model (U.S. EPA SWMM5) developed by Computational Hydraulics International (CHI). In total, 177 simulations were run covering four scenario categories: eight rain events, three climates (the current and two projected), three soil infiltration rates, and five snow water equivalent (SWE) values. Simulation results were analyzed with respect to influential rainfall/snowmelt/runoff factors and the noted differences were statistically tested for significance. Result analysis revealed new findings concerning the differences between runoff generated by rain-on-snow and summer thunderstorm events. In particular, it was noted that a relatively frequent rain-on-snow event, with a return period of 1.4 year, caused fewer flooded nodes and surcharged pipes in the catchment sewer system, but almost five times greater runoff volume, when compared to the same drainage system performance indicators corresponding to a 10-year event occurring in the summer. Depending on the physical characteristics of the snow cover, among which the depth appears the most important, rainwater and snowmelt may be retained in, or released from, the snowpack, which acts as a dynamic reservoir controlling the generation and release of runoff. Smaller snow depths produce smaller volumes of melt, smaller storage capacity and less effective insulation of soils, which may freeze to greater depths and become practically impervious, until the process of soil thawing has been completed. The impacts of climate change in the study area, described by increases in precipitation and air temperatures, are likely to cause more frequent runoff problems attributed to the future rain-on-snow events. Even though the runoff tendencies reported here reflect the characteristics of the study area and climate, they suggest the need to consider rain-on-snow events in sewer design and storm water management in regions with seasonal snow covers, certainly with respect to runoff volumes.

Jackup structures that have cylindrical legs with gear teeth are widely used in shallow waters. Currently, there is a growing demand for the design of ice-resistant jackup platforms in ice-prone cold regions. Due to the limitations of ice load research, the design code for ice-resistant jackup structures is not based on dynamic response analysis that considers a dynamic ice force model. To develop a reasonable ice-resistant concept design and conduct a safety assessment, dynamic response analysis of jackup platforms under ice loads is essential. In this research, based on a model test of ice forces on a jackup platform, the interaction between ice and a cylindrical leg with gear teeth was observed. Then, the failure modes of compliant structures under the ice forces were presented. Finally, ice-induced dynamic responses were computed under typical ice conditions, and ice resistance performance was analyzed using a jackup platform in the Bohai Sea as an example. This study provides a reasonable basis for the ice-resistant conceptual design of jackup platforms in cold regions.

This study evaluated changes in moisture and temperature of clay soils next to an underground aggregate storage bed of a pervious concrete pavement system during the winter in Pullman, Washington. Sensors were installed in order to determine how a neighboring underground aggregate storage bed with retention capabilities might affect neighboring soils such as might occur from installing permeable pavement shoulders next to a roadway. The sensors were located at 30, 60, and 90 cm below the soil surface. According to the findings, none of the soil temperature readings dropped below freezing, nor did the soil moisture readings exceed saturation during the relatively mild winter. Also, during periods of precipitation, the soils near the aggregate storage bed cooled off and then warmed back up faster than soils farther away. The soils near the retention system at depths above the bottom of the aggregate storage bed tended to remain drier than those soils farther away, while closer soils below the bottom of the aggregate storage bed had higher moisture content than those farther away. Therefore, little additional water or colder temperatures are expected on neighboring soils under these conditions from these facilities. However, additional research under colder conditions is warranted to understand what might occur during more severe winters.

A novel anti-icing and deicing technique for wind turbine blades using surface-mounted continuous carbon fiber sheets is proposed and experimentally verified with model blades under both static and rotation conditions. Anti-icing and deicing tests on one model blade in a refrigerator are carried out using different levels of current. Three identical wind turbine scale-model blades are fabricated into a wind turbine model driven by a motor and anti-icing and deicing tests are carried out in a cold chamber. The temperature distribution of the electrically heated model blade under various input voltages, rotation speeds, and air temperatures are measured. The anti-icing and deicing performance including deicing time at different input voltages, energy consumption, and temperature variations with time at various locations along the model blades is presented. Results show that the proposed method is efficient and has great potential for the anti-icing and deicing of wind turbine blades in icing climate sites.

An alternate freezing and thawing cycle (F-T) is a weathering process that is very common in cold regions. In a laboratory, the durability of any stabilized or nonstabilized material can be studied by subjecting the material to alternate cycles of freezing and thawing. In this study, a study of strength and durability of lime-treated jarosite waste exposed to freezing and thawing is investigated. Jarosite with different ratios of lime is compacted in the laboratory and exposed to a maximum of five freezing and thawing cycles. In addition, an attempt has been made to quantify the potential of lime, F-T cycle, and ratio of F-T cycle (C)/curing period (t), in the assessment of unconfined compressive strength (${\mathit{q}}_{\mathit{u}}$) and split tensile strength (${\mathit{q}}_{\mathit{t}}$) of lime-treated jarosite. A number of unconfined compressive and splitting tensile strength tests are carried out on jarosite samples stabilized with various lime contents. The results show that both ${\mathit{q}}_{\mathit{u}}$ and ${\mathit{q}}_{\mathit{t}}$ increase polynomially with the increase in lime content (L), and a power function has been fitted to assess the optimum relationship between ${\mathit{q}}_{\mathit{u}}$ and C/t ratio, as well as between ${\mathit{q}}_{\mathit{t}}$ and C/t ratio. It is observed that for the relationship among ${\mathit{q}}_{\mathit{u}}$, L, and C/t, as well as ${\mathit{q}}_{\mathit{t}}$, L, and C/t, the optimum fit could be obtained after applying a power equal to 1.3 to the lime content (L) parameter and $-0.25$ to the C/t ratio parameter. Finally, a unique relationship between ${\mathit{q}}_{\mathit{t}}$ and ${\mathit{q}}_{\mathit{u}}$ is also established, i.e., ${\mathit{q}}_{\mathit{t}}/{\mathit{q}}_{\mathit{u}}=0.17$, being independent of the parameters C/t ratio and lime content (L).

It has been 10 years since the Qinghai–Tibet Railway (QTR), constructed from 2001 to 2005, was opened to traffic in 2006. Experts from around the world, in the field of cold regions, have been paying close attention to embankment stability in permafrost regions of the QTR. Using ground temperature and embankment deformation data obtained by a long-term monitoring system along the QTR in permafrost regions during the years 2006–2012, the thermal and deformation stability of the embankments are analyzed based on variation of the artificial permafrost table (APT) and the magnitude of settlement, respectively. The results indicate that both the mean annual ground temperature (MAGT) and the types of adopted engineering measures primarily determine the variation of the APT and also dominate the settlement of the embankment. In regard to embankment deformation, most of the embankments of the QTR in the permafrost regions are in a stable state.

This study measures the spectral reflectance from snow with known liquid water content (LWC) in a climate chamber using two optical sensors, a near-infrared (NIR) spectrometer and a Road eye sensor. The spectrometer measures the backscattered radiation in the wavelength range of 920–1,650 nm. The Road eye sensor was developed to monitor and classify winter roads based on reflected intensity measurements at wavelengths of 980, 1,310, and 1,550 nm. Results of the study suggest that the spectral reflectance from snow is inversely proportional to the LWC in snow. Based on the effect of LWC on the spectral reflectance, three optimum wavelength bands are selected in which snow with different LWCs is clearly distinguishable. A widely used remote sensing index known as the normalized difference water index (NDWI) is used to develop a method to estimate the surface LWC for a given snow pack. The derived NDWI values with respect to the known LWC in snow show that the NDWI is sensitive to the LWC in snow and that the NDWI and LWC are directly proportional. Based on this information, the NDWI is used to estimate the surface LWC in snow from measurements on a ski track using the Road eye sensor. The findings suggest that the presented method can be applied to estimate the surface LWC in order to classify snow conditions potentially for ski track and piste applications.

Redistribution of snow loads on two adjacent buildings of different heights is addressed. The term slippery roofs is used but it is not defined. Measurements of friction between snow and commercial roofing materials are carried out to help specify the term. In order to determine a static coefficient of friction, the Coulomb friction principle of measuring inclination increase until specimen movement begins is applied. A test apparatus is designed and produced. Single-ply roofing materials such as membranes made of polyvinyl chloride (PVC), thermoplastic polyolefin (TPO), ethylene propylene diene monomer (EPDM), and modified bitumen (MB), as well as painted industrial metal profile specimens are tested. Snow specimens from fresh snow are prepared and tests are carried out under laboratory conditions. For the given conditions, although deviating from full-scale realistic conditions, snow samples slid at different angles depending on the roofing material type. Average values of sliding angle for PVC, TPO, EPDM, and MB membranes and metal sheet are determined to be 6°, 15°, 20°, 57°, and 22°, respectively. Based on the published provisions and given test conditions, commercial roofing materials can be categorized as slippery.

Top-down longitudinal cracking in asphalt pavement is one of the serious issues in cold regions, although a recently developed pavement mechanistic-empirical (ME) design guide predicts the amount of this cracking damage is considered to be by repeated traffic loads only. Like repeated traffic loads, repeated temperature cycles due to lower night temperatures and higher day temperatures can cause damage in the asphalt concrete (AC) layer and contribute to the top-down longitudinal cracking. Recently, a closed-form equation was developed by the authors for calculating damage due to repeated day-night temperature fluctuations. In this study, the top-down longitudinal cracking predicted by the traditional pavement ME design approach is compared with the top-down longitudinal cracking predicted by the authors’ equation/model, which considers both traffic and temperature induced damages. A total of 29 long-term pavement performance (LTPP) test section data were used to compare the field and the predicted top-down longitudinal cracking. Results show that the top-down longitudinal cracking prediction error, which is the difference between the field measured and the prediction values, decreases by 13% when combining the temperature induced damage with the traffic induced damage.