Study of natural fracture topography in 50cm scale granitic rock block measured by a precision grinder

Tetsu, Keiichi*; Sawada, Atsushi 

For the safety assessment of HLW geological disposal system, the homogeneous parallel plate model is usually applied as one of the nuclide migration evaluation models. The transmissivity and the fracture aperture as an average characteristic is one of important parameters in the parallel-plate model. However, the natural fractures have complex characteristics such as infilling of gauge, branching and roughness of fracture surface. The methodology how to justify those parameter values is one of the important issues. In this study, 50cm scale of the rock block includes single natural fracture was excavated from Kamaishi in-situ experiment site and observed a fracture by grinding the rock surface iteratively. A series of the digital image data of the fracture was obtained in 500 grinding sections, perpendicular to fracture profile. The coordinate of fracture topography was measured in interval of 1mm at each section, and the fracture data was obtained about 250,000 data points.