Journal of Cold Regions Engineering

For safe transportation of loads on floating ice sheets, it is important to determine the breakthrough load of an ice sheet. At present, the breakthrough load is estimated using empirical relations developed from the results of full-scale field experiments. In this paper, a theoretical formulation is presented to derive an expression for the breakthrough load using plastic limit analysis. The velocity field in the vicinity of a distributed load is assumed, and the stresses induced in the columnar ice are assumed to be the biaxial strength, which depends on the strain rate derived from assumed velocity field. The breakthrough load is obtained by equating the rate of work done by the load to the rate of energy dissipation during compression of ice caused by radial and circumferential wedging of ice during deformation. The agreement between the theoretical estimates and the experimental breakthrough loads is good when energy dissipation due to radial deformation along circumferential cracks is ignored. The theoretical estimates of breakthrough loads are about twice the experimental loads when the radial crushing strength along circumferential cracks is assumed to be 1 MPa. Shear or punching failure due to concentrated load on a floating ice sheet is also briefly discussed.

Presented are the results of a water-distribution corrosion study conducted for the City of Yellowknife, Northwest Territories, Canada. Conducted were water-distribution system corrosion tests, the evaluation of corrosion inhibitors, and the sampling of the supply water and corrosion tubercles for corrosion-causing and corrosion-intensifying bacteria. Chemical treatment of Yellowknife's soft, poorly buffered, slightly acidic water using chlorine, hydrofluorosilicic acid, and heat during the winter substantially increases its corrosivity. Ductile iron corrosion increased by approximately 40%, moderately reducing its service life. Similarly, copper corrosion increased by 65%, although its service life was not seriously affected. Corrosion inhibitors identified in laboratory immersion tests as possible additives to the city's treated water were sodium hexametaphosphate between the dosages of 1 and 3 mg/L as phosphorus, and the combination of lime and carbon dioxide to produce a water with the tendency to deposit a protective coating of CaCO ₃ . Sampling of the city's untreated and treated water showed low concentrations of corrosion-causing and corrosion-intensifying bacteria. Corrosion tubercles, however, showed very high bacteria counts to indicate their potential participation in the water-distribution corrosion problem.

The stresses induced in ice covers by river waves are investigated as a possible mechanism for causing transverse cracks during breakup. The maximum stress levels that river waves can cause in the ice cover are determined over the entire spectrum of waves that may be present at breakup. The ice cover is analyzed as a continuous elastic plate. For a given wave amplitude, the amplitude of ice-cover bending stress has two possible maximums: one when the wavelength is equal to 2πl (where l is the characteristic length of the ice cover), and a second when the celerity of the propagating wave equals the celerity of a free (homogeneous) wave of the same wavelength. The present calculations indicate that the celerities of propagating waves are always less than the celerity of free waves of the same wavelength, and, as a result, only the first maximum is possible. The global minimum wave amplitude required to cause cracks is therefore found at a wavelength of 2πl. At this wavelength, a simple expression describing the minimum wave amplitude causing cracks can be derived.