Journal of Cold Regions Engineering

Winter conditions in northern climates and permafrost regions make mining and excavation in frozen ground very difficult. Current methods of weakening frozen ground by thawing with combustible materials or electric heaters are slow and need improvement. Instantaneous volume heating is achieved by radiation heat transfer with microwave energy. The objective of this work by the U.S. Bureau of Mines was to determine the ability of microwaves to thaw frozen soil and gravel. The thawing rates and penetration depths as a function of soil types were experimentally determined at field test sites using a 6-kW microwave system operating at 2.45 GHz. Five types of soil were tested ranging from washed sand to clay with moisture levels from 7 pct to 44 pct. Field thawing tests were performed in Minnesota in winter, with ambient temperatures down to −23°C. The lowest specific energy obtained during field tests was 18 kW$\dot{s}$h/m ³ for a run of mine gravel.

A climatography of 100-year return-period air-freezing indexes (AFIs) has been developed to accompany recommendations for the design of frost-protected shallow foundations (FPSFs) in the U.S. residential construction industry. These design recommendations are based on European FPSF procedures and proposed consensus standards, so this paper investigates and compares the different methods of generating freezing indexes in Norway, Finland, and the United States. Previously overlooked, the differences in these methods have a substantial influence on the estimated AFI and the application of return-period statistics. The method used in the United States to calculate the AFI better represents the ground-freezing effect for all climate regimes. Additional research related to this topic has also shown that the Weibull distribution provides superior predictions of the AFI at long return periods.

The use of wetlands for low-cost and energy-efficient treatment of municipal wastewater is not a new process. In the Northwest Territories, Canada, wetlands have not been used much for wastewater treatment due to the lack of adequate design criteria. As a first step toward greater use, the current status of technology for using wetlands for wastewater treatment has been reviewed. The potential for use of wetlands for municipal wastewater treatment in the Northwest Territories is evaluated. At present, the design of wetland systems for municipal wastewater treatment is based on an empirical approach. There are only a few design models available, which have been tested with limited southern data. The critical design parameter for wetland systems is the hydraulic loading rate, while the organic loading rate is used as a check to ensure that aerobic conditions prevail in the wetland system.

This paper is intended to be the first of a series of papers presenting the results of a comprehensive study aimed at evaluating the influences of two large hydropower generation stations on ice transport and jamming in the upper Niagara River. It provides the background to subsequent papers on the topic. Described herein are the main features of the river, the hydropower facilities, and nine characteristic stages of ice-jam development in the river. The main components of a plan developed to address the questions related to ice transport and jamming in the river are described in general terms. They include the strategy formulated for the study, possible schemes to mitigate jamming, and the evaluation methods used to investigate the efficacy of the schemes. The details of the individual studies prescribed in the plan are intended for presentation in subsequent papers submitted to this journal.