2133 The deposit is accessed via a main ramp which starts at the lowest level of the historical underground mine. This ramp facilitates connectivity between the individual sub-levels and infrastructural excavations as a crusher cavern or additional day access. From the main ramp striking drifts which are parallel to the ore bodies strike are excavated. From those drifts top and bottom drifts for mining the stopes are excavated. Long-hole-drilling is done from the top drift. After blasting, remote controlled mucking is utilized by loadhaul-dump (LHDs) vehicles. Depending on the stopes location underground trucks or LHDs transport the mined magnesite to nearest dump point. Material from elevated levels is transported to an ore pass leading to an ore bunker which is connected to a crushing cavern. The crushed magnesite can be transferred directly to the existing conveyor belt system. The conveyor ends at the mountain station of a cable way which transports the material directly to the processing plant 4 km away. 4.3 Backfill Management The availability of sufficient backfill material is imperative for the future operation of the Bürgl underground mine. The material used as backfill is obtained by processing and mining a historical waste dump in the vicinity of the mine. In consideration of the harsh alpine environment with sub-zero temperatures and substantial snowfall experienced in Hochfilzen during the winter months, operations at the waste dump are only feasible within the period not subjected to snowfall. However, it is imperative to note that underground operations are to be conducted throughout the whole year. An absence of backfill during the winter months, could lead to negative effects on the stability of the open stopes (which remain open throughout the winter months) and the mining sequence. The latter was demonstrated by simulations regarding the availability of backfill in GeoVia's MineSched software. It was determined that implementing six-monthly backfilling results in the removal of a significant degree of flexibility from the mining sequence, thereby extending the total mining period by a period of four years. Figure 5 – Bürgl open pit and historical waste dump (inside blue area). The red cone represents the future backfill storage in the former open pit. Consequently, it is imperative to ensure the availability of sufficient backfill material during the winter months as well. Therefore, it is proposed to follow a strategy where backfill material is stored in the historical open-pit, with subsequent extraction of the material via an underground drawing and backfill collecting system. Figure 5 illustrates the dumped backfill cone within the open-pit mine. The historical waste dump is marked by the blue line.
RkJQdWJsaXNoZXIy MTM0Mzk2