Abstract
Mineral resource depletion drives the need for mining in increasingly remote areas using novel methods. Severe conditions in these remote areas can include permafrost. The Chidliak diamond mine Arctic circle is one such operation. There are many challenges to Arctic mining projects, such as transportation limitations and severe climate conditions. Furthermore, the Chidliak mine has been planned to have the lowest possible carbon footprint. The mining operation applies a novel vertical boring technique into an open pit, by which the vertical kimberlite pipe with a diameter of approximately 125-150 m will be excavated. Each boring operation results in a vertical shaft, having a diameter of roughly 5 m, that is subsequently backfilled. The design of the backfill while considering the mine and environmental limitations is the first step of this study. Cement or binder is omitted from the backfill mixture due to the transportation cost and the adverse effects of low temperature on cementation. Alternatively, frozen backfill in which water plays the role of binder will be used. The backfill is thus prepared as a water-bearing paste and is frozen after deployment into the excavated shafts, as these shafts are surrounded by permafrost rock and sub-zero air temperature. A series of experimental test programs has been carried out to feature sub-zero temperature testing cavity for determining the UCS of frozen backfill, applied to different frozen backfill mixtures in order to obtain the optimum amount of mixture percentages. The water content which has been examined in this study was between 13% and 27%. The frozen UCS test results showed that the highest UCS was obtained by the water content of 20-22%. Moreover, the UCS of backfill ranged almost from 2 to 5 MPa, which was high enough.