Journal of Cold Regions Engineering

A large scale 105-m-long, 0.9-m-diam chilled pipeline experiment was conducted to assess the response of a production pipeline that transits between unfrozen (seasonally frozen) and permafrost soils in discontinuous permafrost regions. Thermal and heave characteristics of the experiment for a three-year monitoring period are reported. In response to the chilled pipeline, the progressive cooling patterns within the permafrost and unfrozen soils were different, resulting in the development of a thermal boundary at the transition zone between the two thermally different soils. The absolute maximum movement of pipeline was 0.197 m near the thermal boundary, resulting in a differential heave of 0.148 m. Three distinct heave phases were identified within the unfrozen soil. Phase 1 of the first 200 days related to penetration and heave above the groundwater table and was characterized by heave rates between 0.211 and 0.237 mm/day. Phase 2 resulted in increased ice segregation due to interaction of the freez-ing front with the groundwater table. This phase lasted from approximately day200 to day 500 and corresponded to a heave rate from 0.206 to 0.313 mm/day. Phase 3 was characterized by a further decrease in the heave rate to about 0.081 mm/day and lasted from approximately day 500 to day 1,056.

This study was carried out to investigate organic and inorganic contaminant removal from melting spray ice produced from aerated stabilization basin treated pulp mill wastewater and the oil sands tailings pond water. The influence of the feedwater characteristics and the ice column contaminant concentration and distribution patterns induced by the degree of freezing during the spraying on the release of impurities were examined. The contaminant separation efficiency was not significantly influenced by the characteristics of the wastewaters. A dramatic decrease of chemical oxygen demand, total organic carbon, conductivity, color (pulp mill effluent), and ${\mathrm{Cl}}^{-}$ and ${\mathrm{SO}}_4^{2-}$ (oil sands tailings pond water) concentration in the early meltwater occurred in all ice columns produced with drainwater formation during spraying. Most impurities entrapped within the ice columns had moved to the bottom of the columns, therefore a greater volume of high-quality meltwater was produced. Release of impurities from these ice columns was best described using a power equation. Reduction of meltwater impurity concentration was much slower when the impurities were distributed uniformly in the ice columns as occurred when no drainwater was produced during spraying. In this case, the decay of the meltwater impurity concentration was best predicted using an exponential function. Preferential release of one type of contaminant over others occurred under some experimental conditions.