8.2.3 Fletcher Mine Backfill Plant
The Fletcher lxlckfill plant is located on the surface (Figures 8.3 and 8.4). The plant consists of a Denver high-intensity mixer, which is fed cement and fly ash stored in 64 and 45-tonne bins, respectively. Cement and f!y ash are transferred by screw conveyors to a bucket elevator, which then elevates the cement and fly ash to a weigh hopper that feeds the material into the mixer by gravity. Dried, cydoned mill tailings are also fed into the mixer via a conveyor belt from a 45·tonne tailings storage bin. A batching cycle takes 12 min to complete, and batch composition is similar to that produced at the Buick Mine.
Once the batch is complete, it is dumped down a 305·m-long cased hole through a pipe of 15-cm inside diameter into a storage bin. The cemented slurry is then loaded into a 7-m3 truck, which transports the slurry to the fill area and dumps it into a sump on top of 23 m3 of run-of-mine waste rock (-1 m). This cycle takes 20 min. Placement of backfill from this point forward is similar to that previously described for the Buick back-fill operation.