the dumped backfill. The inclination of the roof is 40°. This angle has to be steeper than the natural slope angle of the backfill material. Besides that, the inclined roof enhances the stability of the stope. Furthermore, it is possible to mine the stopes with inclined drilling to be able to mine the wedges formed by inclination of the deposit between two sublevels. The adaption of the stope heights and the levels where the historical infrastructure is integrated can be found in Figure 4. The stope pillars have a width of 6 m, which is based on the experience from a mine with a similar mining method. Moreover, backfilling the mined stopes supports the stope pillars which provide local support. For regional stability barrier pillars with a width of 20 m split the deposit in three mining panels. The barrier pillars are a key element for the control of shear stresses which could be induced by the movement of the porphyroid. The mining panels have maximum span of 100 m and include 6 stopes which are separated by 5 stope pillars. In order to exclude the influence of discarded mining areas from old mining operations, the immediate vicinity of these areas is bypassed over a large area, see red line in Figure 4. 4.2 Mining sequence and operations To mine the Bürgl deposit it is necessary to adhere to a strict sequence which is based on rock mechanics and mining planning principles. From operational and stability perspective it is necessary to backfill one stope after it is completely mined. This is necessary to mine the stope above. The drift that was the top drift of one chamber becomes the bottom drift of the new stope above. The floor of this “new” bottom drift is the dumped backfill material. With that method one stope can be mined above each other. There will be 8 stopes in maximum above each other. Another restriction regarding mine stability is the necessity of neighboring stopes being backfilled after a new one at the same sublevel is mined. In general mining should start at lowest and most eastern stopes and should end at the western uppermost stopes. There is a strong dependence on the availability of backfill to continue mining. Besides the restrictions which are given by the backfill, the mining sequence in the panels is prioritized with mining panel 1(blue stopes in Figure 4) which is the easter most with highest priority to mining panel 3 (green stopes in Figure 4) which is on the western side. Within the mining panel the priority for mining a specific stope decreases from east to west. The overall sequence is displayed by the pink arrow in figure cc.
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