Journal of Cold Regions Engineering

Literature on the effects of lowered temperature on the toughness of random short fiber composites have neither offered a clear trend nor explained the mechanisms of failure. In this work, unnotched and notched strengths at room temperature and −30°C of two glass mat polypropylenes with different fiber architectures are investigated. Observations are explained based on models for Young's modulus and notch sensitivity. Increases in strength and stiffness with lowered temperature are caused by increased matrix modulus and yield stress. Fiber bridging operating in a damage zone of substantial length was the major toughening mechanism and forms the basis for the modeling approach for notch sensitivity. Increased notch toughness at low temperature is caused by increased work of fracture in the damage zone. The increased matrix modulus and yield stress lead to an increased toughening efficiency of short fibers.

Communities located on small, northern rivers can experience severe breakup ice jams. While flood damages may be significant locally, they are often insufficient to justify the cost of conventional flood-control structures. Environmental concerns also tend to render these structures unattractive. A new, low-cost structure appears to be well suited to control breakup ice jams on small rivers. It consists of massive sloped blocks, partially buried in riprap, placed across the river adjacent to a natural floodplain. The blocks will arrest a breakup ice run and form a stable, partially grounded ice jam. Trees or boulders on the floodplain retain ice pieces in the river channel while allowing flow to bypass the structure. Large gaps between blocks allow easy fish and canoe passage. Refrigerated hydraulic model tests indicate that the structure should perform well even during severe breakup events. A prototype built in Hardwick, Vt., has performed well during the four mild breakup events experienced to date. Its cost of $3,600/m of river width represents about an order-of-magnitude reduction compared with previous ice-control structures.

Biological treatment has become increasingly popular as a remediation method for soils and ground water contaminated with petroleum hydrocarbon, chlorinated solvents, and pesticides. Bioremediation has been considered for application in cold regions such as Arctic and subarctic climates and Antarctica. Studies to date suggest that indigenous microbes suitable for bioremediation exist in soils in these regions. This paper reports on two case studies, one in Antarctica and one in the subarctic, in which indigenous bacteria were found that were capable of mineralizing petroleum hydrocarbons in soil contaminated with jet fuel and polychlorinated biphenyls (PCBs) in Antarctica and pentachlorophenol (PCP) and diesel in contaminated soil in the subarctic southwestern Alaska. However, in both instances, ex-situ bioremediation was recommended for treatment of the contaminated soil because ex-situ treatment allows greater control over soil temperature, a limiting factor in cold climates.

Ice conditions hamper winter navigation on major U.S. waterways. Accumulations of broken ice in the upstream approaches to locks and dams can interfere with lock operations and hydropower production. Conveying this ice downstream through dam gates can be difficult because of the low water velocities found in pool areas, and the limited available discharge for ice passage during winter low-flow periods. A physical hydraulic model study, using real ice, investigated the design and operation of submergible gates for ice passage at the U.S. Army Corps of Engineers Starved Rock Lock and Dam on the Illinois Waterway. Alternative gate locations were tested for a range of gate discharges and ice conditions. The effects of hydropower diversions, navigation, and high-flow air screens on ice passage were examined. The study found that, under some ice conditions, submergible gates alone may not be adequate for ice passage. During these times, tow and barge transits through the lock and deflector bubbler operation would need to be coordinated with submergible gate operation to pass ice.

A preliminary investigation has been performed to determine the feasibility of conditioning a sulfite pulp mill waste activated sludge (WAS) by freezing and thawing. A series of experiments quantifying dewaterability was performed on the frozen and thawed sludge (“conditioned”) and compared to sludge that had not been treated by freezing (“unconditioned”). These experiments consisted of quantifying the change in settling rates, filterability, and maximum attainable solids content, and were performed at −5°C, −10°C, and −25°C. As a result of freeze/thaw treatment, dewaterability improved dramatically for the conditioned sludges, with the greatest improvement noted for samples frozen at higher temperatures.