Journal of Cold Regions Engineering

Avalanche mitigation routinely uses explosives to both initiate avalanches and test slope stability. This project aimed to verify past findings and further develop an understanding of explosive shockwave interactions with hard and soft slab conditions within 2–5 m of the detonation. Pentolite cast boosters (0.9 and 0.45 kg) were detonated at 0.0, 0.5, 1.0, 1.5, and 2.0 m above the snow. Six orthogonally paired accelerometers inserted into the snowpack recorded snow accelerations. High-pressure sensors located at and above the snow surface measured air overpressures. Distances were scaled to trinitrotoluene (TNT) equivalents to aid in explosive placement comparisons. A substantial advantage was recorded in snow accelerations attributable to elevating explosives above the snow surface. Elevating charges not only increased overall response, but also increased the effective range and depth with no penalty in shock attenuation rates. Using attenuation relationships, a method for predicting the maximum range and affected volume for a specified acceleration value was developed. Field data showed the importance of explosive placement and how the affected volume, and thereby the probability of artificial avalanche release, can be greatly increased.

The U.S. Clean Water Act requires that the Environmental Protection Agency ensures that the location, design, construction, and capacity of water intakes for thermal power plants reflect the best technology available to reduce entrainment mortalities of fish and invertebrates during their early stages of life. Cylindrical wedge-wire screens are an efficient technology for protecting fish and invertebrates at water intakes, as they draw water at low flow velocities through a fine mesh. Although substantially reducing fish and invertebrate mortality, wedge-wire screens run significant risks of blockage by ice. This paper discusses how the characteristics of wedge-wire screens that enhance their ability to reduce mortalities also make them susceptible to blockage by frazil and anchor ice, and presents observations and field data regarding ice formation on a segment of wedge-wire screen placed in a small river. Ice formation on this screen involved initial frazil adhesion with subsequent metamorphism of the frazil disks through in situ ice growth. This resulted in accumulations of porous, relatively strong ice consisting of individual large, irregularly shaped ice crystals. The ice that formed on the wedge-wire screen was identical to anchor ice found on the surrounding riverbed. These findings indicate that ice blockage of wedge-wire screens typically comprises frazil deposition followed by in situ growth of frazil crystals, often resulting in a relatively impermeable, hard-to-remove ice accumulations on wedge-wire screens.

In this study, the flexural properties of large columnar-grained freshwater ice in the temperature range of $-0.5$ to $-10.0°\mathrm{C}$ and strain rates of $4.6\times {10}^{-7}{\mathrm{s}}^{-1}$ to $1.7\times {10}^{-3}{\mathrm{s}}^{-1}$ were reviewed, which is of engineering interest. Two loading modes were used in the test: the upward loading mode (bottom in tension) and the loading force perpendicular to the crystal growth direction (side in tension). The results showed that the flexural strength of large columnar-grained freshwater ice was not affected by the loading direction. In addition, the tests demonstrated the clear dependency of flexural strength on the temperature and strain rate. As the test temperature decreased, the ice became stronger but also very brittle. Because it is a viscoelastic brittle material, the mechanical properties of ice are sensitive to the strain rate. The effective modulus can be regarded as an indicator of the elastic and viscous deformation that is dependent on the strain rate and temperature. The results also showed that there was no significant correlation between the effective modulus of large columnar-grained freshwater ice and the increasing strain rate at test temperatures of $-0.5$ and $-2.0°\mathrm{C}$, but the effective modulus increased significantly when the strain-rate test temperature was between $-5.0$ and $-10.0°\mathrm{C}$.

Winter weather conditions such as extremely cold temperatures, heavy snowfall, and high wind chills are common occurrences in Canada. Impacts of such adverse weather conditions on total highway traffic volume have been the subject of several research studies in the past. However, none of the past studies investigated thoroughly the impacts of severe cold and heavy snowfall on temporal and spatial variations of truck traffic on Canadian highways. Impacts of weather on route choice behavior of truck and passenger car drivers have also not been addressed in the past. This paper presents an in-depth analysis of the winter weather impacts on classified traffic volume in terms of passenger cars and trucks with considerations of highway types. This study is based on large traffic and weather data sets from weigh-in-motion sites and weather stations in Alberta, Canada. The data were collected from six sites located on two primary highways: Highway 2 and Highway 2A, in Alberta. Winter-weather traffic models were developed using ordinary least-square regression to analyze the truck and passenger car traffic variations with snowfall and temperature. The study results indicate higher reductions for passenger car volumes than truck volumes. The reduction in car and truck traffic volume intensifies with rises in snowfall amount due to cold and snow interactions. Rural long-distance roads (Highway 2) experience higher passenger car volume reductions as compared to truck volume. An important finding for Highway 2A, which is largely a commuter road, is the increase in truck volume during severe winter conditions. This increase in truck traffic is contributed from the traffic shifting from parallel roads with inadequate winter maintenance programs. This paper discusses this unique phenomenon, unlike past studies in the literature.