2130 spans of the rooms in the post-pillar layout. The dimensions of rooms and stopes were calculated using Mathews stability graphs method (Mathews et al. 1980; Mawdesley et al. 2001). The dimensions of the local pillars were calculated after Esterhuizen pillar strength formula (Esterhuizen 2008). The outlined dimensions were used to compare post-pillar mining and sublevel stoping at an early stage. However, an additional rock mass classification campaign is planned for more detailed planning. 3.2.3 Dimensions of mining panel In sublevel stoping and post pillar mining the valuable mineral is mined from larger stopes or rooms. Normally these excavations are intersected by pillars, material which remains in the mine for stability reasons. So called stope-pillars provide local roof support to the stopes or the rooms. Depending on deposit geometry, mining method and rock mechanics conditions, these mining areas consisting of stope and pillars, can be divided in mining panels. These panels are limited in extension. In the case of Bürgl mine an approach including local pillars and regional barrier pillars is chosen to ensure stability. In this mixed case, a beam develops above the mined panel, where the rock mass beam spans the excavation while local panel pillars provide partial support. Since the panel pillars cannot carry the full overburden load, stability is primarily controlled by the spanning capacity of the overlying rock. Regional support is provided by the abutments of the mining panel and the barrier pillars, which are also limiting failure to the affected panel and enhancing overall safety. The extension of the mining panel has to be designed in way, that in case of the failure of local pillars, the barrier pillars could bear the additional load. It was necessary to develop a numerical Voussoirbeam DEM-model to determine the dimensions of the mining panel. The results showed that a conservative mining panel width is 100 m. (Brandner 2022) The barrier pillars have a width of 25 m. Figure 3 gives an overview how a mining panel in a sublevel stoping layout could look like. The red arrows indicate the load transfer to the barrier pillars and abutment and the green arrows show the local support provided by the stope pillars. 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
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