Soil covers for cold region mine closures

Soil covers for cold region mine closures

Soil covers are widely used in the closure of tailings and waste rock. However, current soil cover practices are based on experience from temperate regions, and on the theoretical basis provided by agricultural soil physics, which is also derived largely from studies in temperate zones.

Two recent research projects led by SRK’s Vancouver office identified several dozen “cold region” processes with the potential to significantly affect soil covers in high latitude or high altitude locations. Natural cold region soils are subject to ground freezing and ground ice formation, ground thawing and thaw settlement, and seasonal freeze-thaw cycling. But more exotic processes like cryoturbation, solifluction, gelifluction and convective cooling can also occur. These processes result in a range of exotic terrain features, such as ice wedges, pingos, thermokarst, patterned ground, boulder fields, mounds, hummocks, and mudboils. The rates at which these processes occur can be slow enough that they would not be obvious in current observations of soil covers, but fast enough that they might have significant effects over a cover’s design life.

The research surveyed over 100 examples of soil covers either proposed for or constructed on mine wastes in cold regions. Very few of the constructed or proposed covers have been reviewed from a cold region perspective. But several large-scale cover trials in cold regions were identified, and SRK made recommendations for ensuring that those projects make the most of opportunities to advance the state of the art.

Maritz Rykaart: mrykaart@srk.com

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