This report examines phenomena that could affect the performance of soil covers constructed on mine wastes located in cold regions. It reviews the state of knowledge about such phenomena, and their occurrence in existing mine waste covers. It also identifies priorities for research to develop soil cover design and construction methods suitable for cold regions.
Soil covers are widely used in the management of mine tailings and waste rock. However, current soil cover design and construction practices are based largely on experience from temperate regions, and on the theoretical basis provided by agricultural soil physics, which is also derived largely from experience in temperate regions. As a result, they do not take into account many potentially important features and processes that are common in cold regions.
Several dozen features or processes affecting soils have been identified in cold regions. The most widespread processes are ground freezing and ground ice formation, ground thawing and thaw settlement, and freeze-thaw cycling. Cryoturbation, solifluction, gelifluction and convective cooling can also occur in limited conditions. Combinations of these processes with specific soil or hydrologic conditions can result in terrain features such as ice wedges, pingos, thermokarst, patterned ground, boulder fields, mounds or hummocks, and mudboils, as well as a number of less common features. The rates of these processes 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.
Cold regions also exhibit distinct hydrologic phenomena. The effect of freezing conditions on infiltration is one example of importance to cover design and performance. Other less obvious effects may also be important in particular circumstances.
Nearly 100 examples have been found of soil covers either proposed for or constructed on mine wastes in cold regions. Detailed information is seldom available, but it appears that very few of the constructed or proposed covers have been reviewed from a cold regions perspective. The limited cases where cold regions considerations have affected cover design and cover performance are reviewed.
There is a need for additional research on fundamental cold regions phenomena, for development of predictive and design tools that take cold regions phenomena into account, and for the development of best practice guidelines. Several large-scale cover trials are currently underway in cold regions. Coordination of those programs offers opportunities to make significant advances in the understanding of the effects of cold regions phenomena on soil cover performance.
