Geotechnische Risikoanalyse für den Oberbau des Schaubergwerkes Leogang mithilfe von Gesteins- und Gebirgsparametern

Parts of the historic mine district in the Salzburg municipality of Leogang have been open to visitors during the summer months since 1989. The visitor route runs through several former mining chambers, which are connected by adits and crosscuts. The ¿Schrattenbachzeche¿ represents the largest section within the exhibition mine. The so-called ¿Oberbau¿ is located directly above, for which the geotechnical risks are analysed. The ¿Oberbau¿ extends up to the highest areas closest to the surface and represents the most recent phase of mining activity. Weathering and disintegration processes lead to an increased risk of rockfall in the ¿Schrattenbachzeche¿. The mine workings closest to the surface are at risk of collapse or slope failure. The aim of the Master¿s thesis is to determine stability for critical areas and to propose protective measures. The investigations are based on structural and engineering geological mapping, laboratory tests and numerical simulations using UnWedge, RS2 and Slide 2 programmes. Based on fieldwork, the rock mass is characterised using the Geological Strength Index (GSI) and divided into homogeneous zones. For this purpose, two different methods for determining the GSI are applied and their results are compared. Based on these results, suitable sampling locations are selected. The required parameters for loose and bedrock are determined by appropriate laboratory tests. Numerical simulations are carried out to identify possible failure mechanisms. The outcomes of the mapping and laboratory tests indicate poor rock mass quality in the vicinity of the mineralised main fault zone, which is located directly above the ¿Schrattenbachzeche¿. In this area, there is a risk of rockfall affecting the visitor route due to the highly unconsolidated rock mass. Large block failure in this section can currently be ruled out as a failure mechanism. The evaluation of the laboratory tests confirms the low rock mass strength in this area. With increasing elevation within the ¿Oberbau¿, both the rock mass quality and the inflow of water increase. Conjugate, gouge-filled faults are present in the mine workings closest to the surface. Despite these zones of weakness, the numerical simulations indicate high safety factors against chimney-like failure, shear failure and slope failure. Based on the investigations carried out, locally limited safety and support measures to prevent loose rockfall, as well as monitoring measures, are proposed to ensure safe guided mine tours.