OFFICIAL 7. CONCLUSIONS Raise stoping with cemented tailings backfill is the preferred concept for Fen, combining low pre-production development, high potential for mechanization/automation and remote operation, and markedly reduced personnel exposure to rockfall and radiation hazards. The method provides high operational adaptability, as stope geometry can be selected after development based on observed ground conditions and ore quality while keeping raise centrepoints fixed on a 45 m grid. Panel design options allow a trade-off between recovery and stability: full-extraction stopes (circular/hexagonal) achieve higher 2D recovery (~47–52%) than honeycomb layouts (~36%) that introduce panel pillars for increased geomechanical robustness. The main technical constraint is backfill strength development: cemented paste-fill typically requires 12–24 months to reach target strength, imposing strict sequencing. Under a 24-month curing assumption, a 12-stope panel requires ~6 years, so multiple panels must operate in parallel to sustain 5 Mt/y, improving schedule smoothness but demanding disciplined backfill logistics and quality control. By contrast, LHOS remains feasible but is less attractive operationally due to high development demand, reliance on parallel horizons to meet 5 Mt/y, and increased support requirements in barrier-pillar drifts. ACKNOWLEDGEMENTS This study has been supported by the European Union’s Horizon Europe Research and Innovation Program through the project REESOURCE Project under Grant Agreement number 101138460. REFERENCES Dahlgren, S. (2006). Fenvulkanen In: Ramberg, I. B., Bryhni, I. & Nøttvedt, A. (eds.) Landet blir til: Norges geologi, 146. Itasca (2023): FLAC3D. Version 7.0: Itasca. Online verfügbar unter http://docs.itascacg.com/flac3d700/contents.html. Jager, A. J.; Ryder, J.A (1999): A handbook on rock engineering practice for tabular hard rock mines. Johannesburg. Wiseman, N. (1979): Factors Effecting the Design and Conditions of Mine Tunnels. Research Report No. G01G10. Chamber of Mines Research Organization. Johannesburg.
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