Interpretation of geological deformation history using flat-cutting surface of the inner wall of KURT

The KAERI Underground Research Tunnel (KURT) was constructed in 2006, and has been operated for site characterization research in terms of safety assessment of nuclear waste disposal. In this study, we will interpret the long-term brittle deformation history around the KURT site using flat-cutting surfaces and exposed outcrops of the inner wall of the Tunnel. From the study on the fracture system observed in the tunnel and the chemistry using samples from the flat-cutting surfaces, five sets of joints, two directions of major faults and three dominant rock types are identified. Although some relative ages are not yet clear, the simplified deformation history can be interpreted as follows. During the cooling, pegmatitic dykes were intruded. Uplifting and volume change of rock mass caused brittle deformation. Several sets of joints formed under local stress fields. Mafic dykes were intruded along the joint surfaces. Faults occurred and crosscut mafic dykes