Study of natural fracture topography in 50cm scale granodiorite rock block including natural fracture intersection measured by precision grinder

Tetsu, Keiichi*; Takayama, Yusuke; Sawada, Atsushi

JAEA-Research 2022-005, 84 Pages, 2022/08

JAEA-Research-2022-005.pdf:10.32MB
JAEA-Research-2022-005-appendix(CD-ROM).zip:35.68MB

Nuclide migration analyses are conducted for the safety assessment in geological disposal system of HLW. Nuclide migration evaluation of fractured host rock mainly uses a model that approximates the fracture with parallel flat plates. However, the actual fractures in the host rock are different from the parallel flat plates, the fractures have complex characteristics such as roughness of fracture surface and the fillings in the fracture. In approximating a fracture model, the methodology development how to set parameter values such as the transmissivity coefficient and the fracture aperture is an issue. One of the issues is to investigate the geometrical features of actual fractures in the host rock. In this study, for the purpose of understanding the geometrical features of fractures including fracture intersection, the internal fracture shape was measured in detail using the method of surface grinding on 50cm scale granodiorite with natural fracture intersection. Thus, the fracture width, fracture aperture, and the shape of the fracture surfaces were obtained. From the obtain data, characteristics such as the average value of the fracture width, the roughness of the fracture surfaces, and the distribution of the fracture aperture were evaluated. As a result, it was confirmed that one of the fractures near the fracture intersection has a particularly large fracture width and fracture aperture as compared with the other part of fractures. Thus, in the granodiorite rock block used in this study, it was inferred that the most permeable path is not the fracture intersection itself, but the particularly large fracture aperture in the vicinity of the fracture intersection.

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

Tetsu, Keiichi*; Sawada, Atsushi

JAEA-Research 2010-041, 24 Pages, 2010/11

JAEA-Research-2010-041.pdf:4.3MB
JAEA-Research-2010-041-appendix(CD-ROM).zip:18.12MB

In this study, we measured fracture aperture by using a series of the digital image data of a single natural fracture in the 50 cm scale of the granite rock block by grinding the rock surface in 1 mm increment perpendicular to the fracture. The fracture aperture was measured by scaling of the width of void space in between fracture walls, without taking account fracture infilling materials. Thus, we obtained both fracture characteristics, fracture width (separation distance between the fracture walls) and fracture aperture, in 50 cm scale of a natural rock. Ratio of infilling to fracture width is large in which fracture width is relatively small. In this area, fracture aperture tended to become small. Consequently, the flow channel by connecting the fracture aperture become to be localized.

A Study on fracture geometrical characterization by grinding 50 cm scale of granitic rock sample

Sawada, Atsushi; Tetsu, Keiichi*

Dai-38-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.266 - 271, 2009/01

no abstracts in English

Measurement of Fracture Aperture by Observing Fracture Geometry in Grinded Granitic Rock

Tetsu, Keiichi*; Sawada, Atsushi

JNC TN8430 2005-001, 47 Pages, 2005/03

JNC-TN8430-2005-001.pdf:100.76MB

Radionuclide migration analysis in natural barrier is important for the evaluation of the safety of HLW geological disposal system. Hydraulic tests and tracer tests using granitic rock including an artificial fracture or a natural fracture are widely performed to understand permeability and transport properties that are important parameters for radionuclide migration analysis in granitic rock. In this study, in order to understand the hydrology and mass transport properties in a single fracture, geometry and aperture of the single fracture was observed by grinding surface of the rock and recording the photograph iteratively, and fracture aperture was measured. 10cm10cm10cm scale of granetic rock block which has an artificial single fracture was used in this study as a trial of the measurement.

Hydraulic property evaluation by geometrical measurement of a natural single fracture

Sawada, Atsushi; Tetsu, Keiichi*; Sakamoto, Kazuhiko*

no journal, , 

no abstracts in English