2134 5. CONCLUSIONS AND OUTLOOK The study demonstrates the technical feasibility of underground magnesite extraction at Bürgl using sublevel stoping with rockfill, selected for safety, selectivity, and cost-effectiveness in a complex alpine setting. Design parameters were derived from empirical and numerical methods, incorporating stope geometries, local stope pillars, and barrier pillars to manage shear along the porphyroid zone, alongside a strict mining-and-backfill sequence and integration of existing infrastructure. A key operational risk is seasonal backfill availability; the proposed winter storage in the former open pit with underground draw mitigates sequence disruptions and supports year-round stability. Next steps include refining geotechnical characterization of weak units, deploying instrumentation for pillar and stope monitoring. Moreover, the feasibility of an underground draw of backfill has to evaluated using DEM-simulations. Besides that, the design of appropriate ventilation has to done. REFERENCES Barton, Nick; Lien, R.; Lunde, J. (1974): Engineering Classification of Rock Masses for the Design of Tunnel Support. In: Rock Mechanics Felsmechanik Mecanique des Roches 6, S. 189–236. DOI: 10.1007/BF01239496. Bieniawski, Z. T. (1989): Engineering Rock Mass Classifications: A Complete Manual for Engineers and Geologists in Mining, Civil, and Petroleum Engineering: Wiley (A Wiley-Interscience publication). Online verfügbar unter https://books.google.at/books?id=pejDUvjwPdMC. Brandner, N. (2022): Untersuchungen zur Baufeldbreite im geplanten untertägigen Bergbau Bürgl. Mastersthesis. Montanuniversität Leoben, Leoben. Chair of Mining Engineering and Mineral Economics. Esterhuizen, G. S. (2008): Pillar Strength and Design Methodology for Stone Mines. In: Dept. of Mining Engineering, College of Engineering and Mineral Resources, West Virginia University (Hg.): Proceedings of the 27th International Conference on Ground Control in Mining. Unter Mitarbeit von G. L. Finfinger, K. A. Heasley, Khair AW, Luo Y, Mark C, Peng SS und S. C. Tadolini, S. 241– 253. Online verfügbar unter https://api.semanticscholar.org/CorpusID:149453954. Geosphere Austria (Hg.) (2024): Deliverable No 4.1. Part 1: Field Guidebook. Unter Mitarbeit von Holger Paulick, Kati Laakso, Matthieu Molinier, Michaela Frei, Veronika Kopačková-Strnadová, Piotr Lipiarski et al.: Zenodo. Heinisch, H.; Pestal, G.; Reitner, J. M. (2015): Erläuterungen zu Blatt 122 Kitzbühel. In: Geologische Karte der Republik Österreich 1:50.000: Erläuterung. Wien: Geologische Bundesanstalt (GBA). Online verfügbar unter https://opac.geologie.ac.at/ais312/dokumente/122_Kitzbuehel.pdf. Mathews, K. H.; Hoek, E.; Wyliie, D. C.; Stewart, S.B.V. (1980): Prediction of stable excavation spans for mining at depths below 1,000 meters in hard rock. Hg. v. CANMET (DSS Serial No. OSQ8000081). Online verfügbar unter https://api.semanticscholar.org/CorpusID:260229381. Mawdesley, C.; Trueman, R.; Whiten, W. (2001): Extending the Mathews stability graph for open stoke design. In: Mining Technology 110. DOI: 10.1179/mnt.2001.110.1.27.
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