Investigation of vertical cutter mining for increased primary resource recovery and decreased environmental impact
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Journal Title
Journal ISSN
Volume Title
Insinööritieteiden korkeakoulu |
Master's thesis
Authors
Date
2017-12-11
Department
Major/Subject
European Mining Course
Mcode
ENG211
Degree programme
European Mining, Minerals and Environmental Programme
Language
en
Pages
112 + 11
Series
Abstract
The purpose of this thesis is to aid in the development of vertical cutting mining as a mining method. In order to do so, the technical feasibility and viability, and environmental benefit of vertical cutting as a complementary mining method were investigated. The investigation was performed for the case of the Victor Diamond mine in northern Ontario, Canada, where open pit mining ends by the end of 2018 or beginning of 2019.Vertical cutting has been used for several decades for the construction of water retention walls in the civil engineering industry. By placing the vertical cutter system directly on top of an ore target and cutting straight, vertical trenches up to a maximum depth of 150 m, it is intended to cross over to the mining industry. Extraction with vertical cutting can occur according four extraction scenarios. Three of the scenarios are land-based, the fourth assumes flooding of the mine, and has not been considered for the Victor project. Checkerboard mining is the base case extraction scenario with an extraction rate of approximately 30%. The long trenching scenario would increase the recovery with an additional 15% but induces a high risk of instability in the existing pit walls and the kimberlite in between the trenches. Application of backfill is the third scenario and achieves a recovery of 98%. Backfilling of the trenches requires the movement of significant volumes of additional rock as well as induces time delays due to the curing time of the backfill. Financial evaluation of the vertical cutting scenarios shows a high dependency of the project value on a decreasing cutting performance. Cumulative cash flow analysis and NPV suggest that extending the mine life at the Victor Diamond mine with vertical cutting is favourable. Even in the case of increased rock strengths, as expected in the deeper parts of the Victor pipes, vertical cutting has a positive net present project value. Long trenching, which is considered to be of high risk for pit stability has only marginally greater project value than the base case. The development of alternative mining solutions also aims to reduce the impact of the mining operations on the surrounding environment. Vertical cutting combines multiple mining processes into one operating piece of equipment. It reduces the GHG emissions, improves the safety of extraction process and is expected to increase the support from stakeholders. Extending operational life using conventional methods would require large expansion of the mine involving the increase of the operational fleet, pumping capacity and land usage. The application of vertical cutting has the ability to prevent the negative impact of enlarged open pit mining while maintaining the benefit of continued production.Description
Supervisor
Rinne, MikaelThesis advisor
Buxton, MikeSchwank, Stefan
Keywords
alternative mining, trench cutting, kimberlite, residual resource recovery, rock stability