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R. Secklehner:
"Untersuchungen zum Einfluss der Verteilung der Raumstellung von Trennflächen auf die Standsicherheit von Hohlraumbauwerken";
Supervisor: A. Preh; Institut für Geotechnik, 2019; final examination: 2019-04-12.

Rock mass behavior is extremely affected by the interaction of massive rock blocks, separated by joints (discontinuities). Depending on the characteristics of joint struc-ture, rock may be classified as a continuum or as a discontinuum. In nature, rock mass is generally assumed to be a discontinuum.
Individual joints of a joint set are considered mostly parallel one to another, according to the orientation of their significant (dominantly median) member. This assumption can lead to the negligence of a critical loss of stability, caused by joint orientation un-certainties (Poisel et al., 2017).
Software applications are preferred for the analysis of joint structure, which inhabit an extensive geometrical complexity and, therefore, pose difficulties for calculations by hand. The analysis is either performed with analytical or numerical software. A com-mon method for the analytical calculation of discontinuous systems is the Block Theo-ry (Goodman and Shi, 1985). Numerical calculations for discontinuous systems can be done with Discrete Element Method (DEM) (Cundall, 1988 und Hart et al., 1988). The analyses in this thesis were accomplished with the Block Theory and the DEM. For the examination with the Block Theory the applications Block Theorie (Langer, 1986) and Unwedge (Rocscience) were used. Numerical investigation, based on the Discrete El-ement Method, was realized by means of 3DEC from Itasca Consulting Group.
Presently, Eurocode regulations provide a basis for the verification of the stability of rock blocks. The Eurocodes consider partial safety factors, which are applied on ac-tions and shear strengths. However, joint orientation uncertainties are not addressed in the current version of Eurocode 7. Recent publications (Poisel et al. 2017 and Harri-son, 2017) demand a consideration of scientific issues, which are typical for rock me-chanics e.g. joint orientation uncertainties. The Eurocode 2020 amendment should ad-dress those particular issues. Consequently, the Eurocode 7 is formally not applicable in tunneling (Radoncic, 2012 und Hofmann et al., 2010). In Austria this gap is bridged on a national basis with supplemental documents, such as the OeGG Guidelines.
The aim of this thesis is to analyze the effects on the stability of subsurface buildings, resulting from natural joint orientation uncertainties. Investigations were performed on the model of a cavern in jointed rock.
The results of Block Theory and DEM were then compared with each other. Further-more, comparisons were drawn between the results of the application of partial safety factors and the consideration of joint orientation uncertainties.

Three different joint sets were investigated to answer the key question of this thesis. The first two systems are a result of geological mapping in the Renz quarry (Kolen-prat, 2019). The third system originates from the exercise for applied rock mechanics at the Vienna University of Technology (Poisel, 2015).
Results of Block Theory and DEM for block shapes, failure mechanisms and failure schemes (localization and extent of failure) are qualitatively comparable. In addition, it was determined that, in order to receive plausible results for the failure mechanism and the failure scheme, joint orientation uncertainties have to be considered. The ap-plication of partial safety factors is, on the contrary, not sufficient for the determina-tion of block failure.

rock mechanics, tunneling, Block Theory, DEM, joint orientations, Eurocode 7