Geotechnical Characterization of Bukov Underground Research Facility

Bukov Underground Research Facility (Bukov URF) is designed to operate as a test site to assess the properties and behavior of the rock mass analogous to selected seven candidate sites in the Czech Republic. It is situated at a depth of about 600 m beneath Earth's surface, which corresponds with the proposed storage depth of the final locality for the national deep repository of high-level radioactive waste. Bukov URF, the construction of which has started in 2013, is situated in the southern part of the Rožná uranium deposit, about 40 km NNW from Brno. The rock mass is composed of relatively monotonous rock sequences mainly represented by migmatized biotite paragneisses up to stromatic migmatites, amphibole-biotite to biotite-amphibole gneisses, and amphibolites. Based on the analysis of physical and mechanical properties, intact rocks in the studied area exhibit a high to very high strength and may be only locally affected by metasomatic alterations. The research activities focus on a complex geological and geotechnical characterization of the rock mass of interest, which is necessary for further in situ research. This paper briefly describes the main results of the current stage of geotechnical exploration and research works made there by the Institute of Geonics of the CAS. These works especially include: determination and evaluation of physical and mechanical properties of the rocks taken from the drift walls and from the boreholes during driving, calculation of rock mass quality based on selected index rock mass classification systems, determination of stress and strain state of the rock mass using the methods of hydrofracturing, Goodman Jack, strain gauge probe measurements, long-term periodical tensometric and convergence measurements, and evaluation of the effects of technical and mining-induced seismicity on the rock mass of interest.