Figure 3 – Mining panel in a sublevel stoping layout. Red arrows indicate the load transfer to the barrier pillars and abutment; Green arrows show the local support provided by the stope pillars. 3.2.4 Integration of old mine infrastructure Another challenge for mine planning in Bürgl mine is the integration of already existing mine infrastructure in the future mining layout. As described in section 2, underground mining has already been conducted in the 1960s in the Bürgl deposit. During that mining period, a number of drifts and also some mining areas were excavated. Some of the infrastructure is nowadays used for material transport from a nearby quarry. A ropeway station and belt conveyors are installed in the underground workings. An ore pass is used to connect different levels. There are also additional drifts, shafts and a cavern which could be used for the future mine. On the other hand, from the point of view of rock mechanics and mine planning, the presence of drifts and mining areas in specific parts of the deposit can be disadvantageous. Existing drifts intersect areas potential pillars and tunnels. When it comes to sublevel stoping it is necessary to adapt the elevation of the new sublevels to the existing ones, to eliminate unfavorable intersections of them. Especially mining areas, where caving was tried, have to be excluded from mining. 3.2.5 Comparison of mining methods Based on initial dimensioning, a sublevel stoping and a post pillar layout, were developed in Surpac. Besides the extraction areas, the design also included the development which has to be excavated for a safe and productive underground mine. Different indicators were compared to find the most appropriate mining method to mine the Bürgl deposit. The indicators which were used to compare the mining methods were: ● Recovery of deposit ● Development costs per ton mined ● Flexibility and selectivity ● Mining costs ● Productivity
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