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JAEA Reports

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.

Journal Articles

Fracture hydraulic characterization based on aperture data measured by 50 cm scale rock sample

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

Dai-40-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.236 - 241, 2011/01

The homogeneous one-dimensional parallel plate model is usually applied for nuclide migration model in a single fracture. An actual fracture in the natural geological environment has complex rough surface. It is one of issues for developing the methodology how to define the representative parameters used for the parallel plate model, such as transmissivity and aperture. In this study, we conducted the fracture geometrical characterization by grinding 50 cm scale of rock block including a single natural fracture, and we obtained fracture aperture distribution. The relationship between fracture aperture distribution and hydraulic characterization was examined by comparing numerical simulation with hydraulic test results.

JAEA Reports

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.

Journal Articles

Evaluation study on flow and tracer experiments using fracture geometry data measured by grinding rock sample

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

Dai-39-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.54 - 59, 2010/01

no abstracts in English

Journal Articles

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

JAEA Reports

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

Tetsu, Keiichi*; Sawada, Atsushi

JAEA-Research 2008-079, 30 Pages, 2008/10

JAEA-Research-2008-079.pdf:6.81MB

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.

JAEA Reports

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. 10cm$$times$$10cm$$times$$10cm scale of granetic rock block which has an artificial single fracture was used in this study as a trial of the measurement.

JAEA Reports

Examination of hydraulic property of natural rock specimen

; Tetsu, Keiichi*;

JNC TN8430 2001-003, 58 Pages, 2001/03

JNC-TN8430-2001-003.pdf:10.04MB

Handling methods and test conditions of hydraulic tests for NETBLOCK system had been examined by using acrylic and/or artificial rock specimen. A natural rock specimen (granite : excavated from Kamaishi mine) with fracture intersection was formed into practicable size for NETBLOCK system. Recently, we conducted a series of hydraulic test, in order to study the influence of fracture intersection by using the natural rock specimen. Hydraulic tests were conducted under several centimeters of head, which could be controlled by improved system because hydraulic permeability of target fractures were high. As a result, 10$$^{-4}$$$$sim$$10$$^{-5}$$(m$$^{2}$$/s) orders of hydraulic transmissivity of target fractures could be measured. A low permeability in the NW direction at the lower fracture was estimated from the heterogeneous head distribution. However, it is also expected that turbulence flow might be occurred under this study condition because fracture permeability is high and flow rate through the fracture is relatively high. In case of turbulence-flow, an estimated hydraulic transmissivity is low. High-viscosity fluid hydraulic test to achieve laminar flow will be needed for correcting an evaluated transmissivity.

Oral presentation

Hydraulic property evaluation by geometrical measurement of a natural single fracture

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

no journal, , 

no abstracts in English

Oral presentation

Characterization of fracture aperture for groundwater flow and transport

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

no journal, , 

no abstracts in English

Oral presentation

A Study on fracture aperture measurement by grinding 50 cm scale of rock sample

Sawada, Atsushi; Tetsu, Keiichi*

no journal, , 

no abstracts in English

11 (Records 1-11 displayed on this page)
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