Ground support challenges in arctic mining conditions

Authors: Falmagne, V; St-Onge, N Download Paper

DOI https://doi.org/10.36487/ACG_rep/1925_08_Falmagne

Cite As:
Falmagne, V & St-Onge, N 2019, 'Ground support challenges in arctic mining conditions', in J Hadjigeorgiou & M Hudyma (eds), Ground Support 2019: Proceedings of the Ninth International Symposium on Ground Support in Mining and Underground Construction, Australian Centre for Geomechanics, Perth, pp. 139-154, https://doi.org/10.36487/ACG_rep/1925_08_Falmagne



Abstract:
The Meliadine and Amaruq mines, inaugurated by Agnico Eagle in 2019, are located in the Canadian Arctic, in areas of deep and continuous permafrost. Excavation of the exploration ramp at Meliadine started in 2013 and at Amaruq in 2017. These underground mines are being developed in conditions that vary from perennially frozen rock, through a transition zone where the rock temperature is below 0°C but where groundwater may be present in a liquid state depending on its salinity, to rock masses with a temperature perennially above 0°C. Brine is required as service water and for all drilling activities in permafrost but may be replaced by naturally saline groundwater below the permafrost. Ambient air conditions underground vary seasonally with depth and following ventilation patterns. As such, ground support elements and materials need to be adapted to the temperature and environmental conditions specific to each stage of mine development and operation. During the initial stages of ramp development, the freezing air and rock temperatures encountered throughout most of the year make the use of resin-grouted rebar difficult. The primary ground support within the permafrost areas therefore consists of inflatable bolts and friction bolts with mesh. As the mine progresses deeper and equipment becomes available, resin-grouted rebar and cement-grouted cable bolts are introduced. The integration and implementation of each type of ground support element require testing and the development of quality assurance and/or quality control protocols. Heating mine air in an arctic environment is costly and was a matter of debate during the project evaluation and development phase. The experience at Meliadine has shown that very cold air in the presence of groundwater can lead to the rapid formation of ice in joints, causing the premature failure of ground support elements. It is concluded that the combined presence of groundwater and freezing temperatures is problematic and that mine air heating is required in such conditions.

Keywords: ground support, corrosion, ice formation, groundwater, permafrost, risk management

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