Journal of Cold Regions Engineering

Thermal effluents are often discharged by municipalities, industries, and thermal power plants into nearby streams. In northern regions, where rivers are ice‐covered for part of the year, these thermal effluents have the effect of melting the ice cover over long reaches. Ice‐cover melting is primarily a function of the prevailing meteorological conditions, the hydrodynamic characteristics of the receiving stream, and the effluent thermal and flow conditions. A two‐dimensional numerical model for the melting of ice covers in rivers is presented. The flow field is simulated by use of the St. Venant's equations incorporating the effect of the ice cover on the flow. The temperature distribution is modeled using the unsteady two‐dimensional energy equation, while ice thickness is simulated via heat exchange with the atmosphere, through the ice cover. The model is tested in a number of cases and compared to analytical solutions. A numerical simulation is carried out for a reach on the Mississippi River near Bettendorf, Iowa, where a power plant discharges its effluents into the river. The results compare favorably with documented field observations.

Eccentric and concentric unconfined compression tests are conducted to examine the influence of strain gradients on the brittle failure of ice. Fresh‐water columnar‐grained ice specimens are tested at a temperature of $-10°C$ and average strain rates of approximately ${10}^{-4}{s}^{-1}\text{.}$ Considering the strain varies linearly across a specimen, the stress distribution is determined from conditions of equilibrium of forces and moments. At failure, the average stresses for eccentrically loaded specimens are usually less than those for concentrically loaded ones. In the case of eccentrically loaded specimens, however, local stresses at some point along the specimen's width (usually one of the sides) reach a maximum value exceeding the average stress for a concentrically loaded specimen. Measured failure stresses show some scatter, which is commonly observed for brittle failure. Nonetheless, the maximum local stress reached in a specimen appears to increase with increasing strain (or stress) gradient. The maximum stress‐strain gradient dependence provides an explanation of the apparent size effect on ice failure stresses.

The increasing use of spray ice in arctic offshore exploration and construction initiated a study that includes a series of triaxial compression tests on saline, laboratory‐made spray ice. Factors affecting spray‐ice behavior and its engineering properties are independently selected and assessed, and the results are compared with the existing literature on spray ice and similar materials. The stress‐strain behavior of spray ice is studied for isotropic consolidation pressures ranging from 45 to 172 kPa, applied for four to 19 hours. The constant rates of strain used during the triaxial compression are $1.5\times {10}^{-4}{s}^{-1}$ and $1.8\times {10}^{-5}{s}^{-1}\text{.}$ The test temperature is $-10°C$ with a few tests performed at $-5°C\text{.}$ For the range of strain rates considered, a yield strength envelope for spray ice is suggested that separates the initial quasi‐elastic behavior from plastic deformations; beyond the yield surface, the material behaves as a frictional medium. The results compare well with previous published analysis, despite the limited number of tests.