1895 4. MINING METHODS – GENERAL Favorable geology and geotechnical conditions, together with the relatively shallow planned mining depth, make the Fen deposit attractive for a mining complex targeting 5 Mt of ore per year. The study for this paper compares two mining methods that maximize resource extraction, ensure high safety standards, minimize workforce radiation exposure, and reduce environmental impacts by using processing-plant tailings as backfill to avoid large surface tailings dams. Additional objectives include high mechanization, automation, and digital/remote operation, strong equipment reliability, high labor productivity, and flexibility under changing conditions through large primary excavations that are subsequently backfilled. Methods based on large primary stopes followed by cemented paste backfill made from dewatered plant tailings are considered most suitable under these conditions. Mining would typically start at the lowest horizon and advance upward. Stopes are mined, backfilled via belt or pipelines with cement added near the stope, then allowed to gain strength before adjacent ore pillars are extracted. Success depends strongly on backfill quality, supply reliability, and backfill operational performance. 5. LONGHOLE OPEN STOPING WITH CEMENTED BACKFILL (LHOS) 5.1 Mining method concept and layout logic Sublevel stoping is suited to competent rock masses where open stopes can be maintained during extraction. For Fen, a backfilled variant is considered to enhance stability and reduce deformation/subsidence risk. The deposit is subdivided into multiple sublevels; stopes are mined transversely, requiring two drifts per stope (top and bottom). A slot/initial opening is created (e.g., boxhole or start slot), then longhole production drilling and blasting proceed. Mined stopes are subsequently backfilled to provide support and enable adjacent stopes to be extracted safely. Planning architecture is hierarchical: ● Stopes are grouped into blocks (10 neighboring stopes at the same stope level). ● Barrier pillars separate blocks to maintain regional stability and host main access drifts. ● A stope level comprises 12 blocks. ● Five stope levels stacked form a mining field. ● Mining fields are separated by a sill pillar to decouple interactions between stacked levels. Figure 2 – Horizontal and vertical sections of one mining field, including drift positions (red).
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