OFFICIAL longholes; ring spacing is typically 3-5 m. Depending on ring spacing and geometry, each blast can yield roughly 15 000-24 000 t of ore (assuming a bulk density of ~3.0 t/m³). Explosives consumption is about 120 g/t, using different energy products to maintain uniform loading density. Blast design is critical. Broken rock is loaded from the bottom level where remotely operated equipment controlled from surface can be used. Stopes will be backfilled with cemented plant tailings. The principal process of Raise Mining with backfill is outlined as follows (Figure 5): a. Platform lowering: Lower a platform into the raise, from which drilling and explosive loading are conducted. b. Detonation preparation: Raise the platform before detonation. c. Material handling: Muck the blasted material from the draw bell on the foot drift, crush it, and transport it to the surface via a conveyor belt. d. Backfilling: Seal the access to the stope from the foot drift and backfill the stope by bringing in material from the stope Figure 5 – Schematic illustration of the Raise mining method; vertical cross section; only steps (a) to (c) are shown 6.2 Stope and panel layout Design of stopes varies in shape and size to give enough flexibility to account for changing geological and geotechnical conditions of the rock mass. In addition, challenges facing mix optimization, curing and strength development of backfill which are not fully resolved at the current state of the project (PFS) can be met by a change in stope layout without change of the overall layout of the mine. Three variations of stope layout are considered (Figure 6): ● Option 1: Circular-shaped stopes; full extraction; diameter = 45 m; cross section = 1 582 m² ● Option 2: Hexagonal-shaped stopes; full extraction; cross section = 1 754 m² ● Option 3: Hexagonal-shaped stopes; reduced extraction; honey-comb structure
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