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Interpretation of the deep geological and tectonic setting is a key step for safety assessment of the potential sites for a deep geological repository of radioactive waste. However, the conventional geological mapping is difficult in the agricultural landscape with lacking rock outcrops. To address this task, we combined geological and hydrogeological mapping, morphostructural analysis and geophysical methods to construct a new geological map and a 3D model of the Březový potok site in the southwestern Czech Republic. They provide unique constraints for the understanding of the subsurface geological and tectonic architecture. The results are compared with the archive geological data and the usefulness of individual geophysical methods to detect the lithological contacts and tectonic zones is discussed. We present this multi-disciplinary research strategy as a workflow for detailed geological characterization, which can be successfully applied on other sites with similar geological environment. [ABSTRACT FROM AUTHOR]

The recently opened Bukov underground research facility is used by the Czech national authority for radioactive waste repository for underground research and safety assessment purposes as part of the Czech deep geological repository (DGR) development programme. The laboratory, which is both site-specific and generic at the same time, is located at a depth of 550 m below ground level in the former Rožná uranium mine in the southeast of the Czech Republic in crystalline rocks of the Bohemian Massif. During the laboratory construction, a multidisciplinary approach was used in order to document and visualize the environment for the following experimental programme. The obtained data are important for understanding the geological environment and the rock characteristics of the Bohemian Massif in the process of deep repository planning and siting. The multidisciplinary approach included petrology, structural geology, geochemistry, geochronology, geotechnical parameters and excavation damage zone description, as well as 3D visualization of the rock environment and laboratory itself. New field observations reveal the Cambrian–Ordovician volcano-sedimentary origin of the studied rocks that have been affected by two-phase reworking during the Variscan orogeny. The rock mass is of high to very high strength and low permeability and the rock mass properties are mainly influenced by tectonic structures. Above all, the presented multidisciplinary approach enables unified and comparable evaluation of such facilities as well as the potential locations of the future DGR. • URF Bukov represents newly opened hybrid-type URF, unique in the Central Europe. • DGR planning and siting process in crystalline rocks in Bohemian Massif. • Quality and stress state assessment of the rock mass within underground laboratory. • Rock mass properties are mainly influenced by structural features. • Multidisciplinary approach enables unified and comparable evaluation of various sites. [ABSTRACT FROM AUTHOR]

Understanding the distribution of brittle structures throughout a rock mass is one of veryimportant factors for safety assessment of underground facilities, e.g., deep geologicrepositories for spent nuclear waste. In spite of the importance of geological data, in theinitial stages of the evaluation process it is often not feasible to perform extensive drillingcampaigns or geophysical measurements. To address the problem, we have developed amethodology which allows us to construct Discrete Fracture Network (DFN) models offractured rock mass using limited surface outcrop data. In order to fully exploit the information potential of rock outcrops, an enhanced procedureof structural data acquisition based on 3D photogrammetry has been proposed. First,using high-resolution digital images obtained in the field, realistic 3D models ofoutcrops are reconstructed and placed in correct geographical position and orientation.Subsequently, fractures are visualised via faces of the triangulated mesh and their spatialcharacteristics, such as trace length, dip, and strike can be extracted. The greatest benefit ofthe adopted approach is that properly oriented, reconstructed and geographicallyemplaced outcrop model can be used repeatedly as the need for more structural dataarises. The acquired structural-geological data are used to construct 3D DFN models of thefractured rock mass. The DFN modelling employs common statistical distributions offracture size (power law distribution) and orientation (Fisher distribution). In order tohonour the field observations, fracture volume density (P30) and the parametersof the fracture size distribution are obtained by minimizing objective functions,which quantify the discrepancy between the observations and model reproductionsat the outcrops. Once the model parameters are identified, any number of DFNrealizations can be created by a random process respecting the adopted statisticaldistributions. The algorithms for DFN identification and reconstruction have beenimplemented using Python programming language in an in-house specialized softwareDFraM. This work is a result of Radioactive Waste Repository Authority, Czech Republicproject "Research support for safety assessment of a deep geological repository". [ABSTRACT FROM AUTHOR]