Resume/ Abstract
Insulation covers for mine site reclamation take advantage of the cold climate of arctic regions to maintain mine wastes perennially frozen and below a target temperature in order to limit acid mine drainage generation. The thickness of the cover depends on atmospheric conditions, surface conditions (ex: snow cover), and the thermal characteristics of the cover materials, which vary with their water content.
The construction of in situ experimental cells is a useful tool to assess the thermal behavior and performance of cover systems. This study investigates the performance of two insulation cover configurations, using field experimental cells built in 2011 at Raglan Mine (Nunavik, Quebec). The first tested configuration is a 2.4 m thick insulation cover made of crushed rocks that aims to control the temperature of the tailings based on conduction-dominated heat transfer. The second configuration includes a coarse-grained layer that aims at favoring cold temperature in the tailings via convective cooling. Ground temperature was monitored at various elevations in the covers and the tailings. An analysis of the temperature profiles in the cover and at the cover-tailings interface provides insight on the behavior of the tested covers over the past 8 to 9 years. The performance of the cover systems is also assessed through a theoretical evaluation of the oxygen flux consumed by the reactive tailings when the target temperature is exceeded. Results show that water can influence considerably the behavior and performance of insulation covers by limiting the thaw depth during summer.