Evaluation of permeability of a fracture system under true triaxial compression
| Project/Area Number |
15206098
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Earth system and resources enginnering
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| Research Institution | Tohoku University |
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Principal Investigator |
MATSUKI Koji Tohoku University, Graduate School of Environmental Studies, Professor, 大学院・環境科学研究科, 教授 (10108475)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAGUCHI Kiyotoshi Tohoku University, Graduate School of Environmental Studies, Lecturer, 大学院・環境科学研究科, 講師 (50261590)
KIZAKI Akihisa Tohoku University, Graduate School of Environmental Studies, Research associate, 大学院・環境科学研究科, 助手 (60344686)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥28,860,000 (Direct Cost: ¥22,200,000、Indirect Cost: ¥6,660,000)
Fiscal Year 2005: ¥5,200,000 (Direct Cost: ¥4,000,000、Indirect Cost: ¥1,200,000)
Fiscal Year 2004: ¥9,230,000 (Direct Cost: ¥7,100,000、Indirect Cost: ¥2,130,000)
Fiscal Year 2003: ¥14,430,000 (Direct Cost: ¥11,100,000、Indirect Cost: ¥3,330,000)
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| Keywords | Sheared fracture / Large synthetic fracture / Permeability of a fracture / Fracture aperture / Size effect / Anisotropy in permeability / Heterogeneity in permeability / Localization of water flow / 真三軸圧縮応力 / 透水性 / 人工き裂 / 引張き裂 / フラットジャッキ / 花崗岩 / せん断変形 / き裂システム / き裂閉鎖 / せん断変位 / みず道 |
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| Research Abstract |
In this study, we performed both experimental studies on permeability of a fracture under true triaxial compression and theoretical studies on aperture and permeability of a fracture utilizing large synthetic fractures of up to 12.8m.
Main results obtained by experimental studies can be summarized as follows :
1. An experimental system developed in this study can evaluate the heterogeneity in the permeability of a fracture under uniform normal stress for a pore pressure of less than 0.3MPa and shear displacement of less than 50mm.
2. Experiments on an artificial fracture showed that the permeability of the fracture varied by 7.5 to 11.5% and that the hydraulic aperture gradually decreased with an increase in both normal and shear stresses.
3. Experiments on a tensile fracture showed that the experimental system could evaluate the permeability for a pore pressure of less than 0.3MPa, but a problem to be solved remained since air was trapped in the fracture.
Main results obtained by theoretic
… More
al studies can be summarized as follows :
1. A computer code for creating a synthetic fracture reproduced the ratio of the power spectral densities (PSDs) between aperture and surface height, measured for a tensile fracture of 1m in granite.
2. The size effect on the permeability of a normally closed fracture disappears when the fracture exceeds 0.2m since the size effect on the standard deviation (SD) of the initial aperture disappears when the fracture size exceeds 0.2m. We proposed an empirical formula for the permeability of a normally closed fracture, which is independent of the fracture size and the SD of the aperture. Similarly, the size effect on the permeability of a sheared fracture disappears when the shear displacement is less than about 3.1% of the fracture size since the size effect on the standard deviation (SD) of the initial aperture disappears under such conditions.
3. The anisotropy in the permeability of a sheared fracture increases with both shear displacement and closure. This anisotropy is caused by the difference in the aperture PSDs between two directions of macroscopic water flow ; perpendicular and parallel to the shear displacement. Furthermore, water flow is more localized with the shear displacement since a fewer channels with a greater area are formed as the shear displacement increases. Less
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Report
(4 results)
Research Products
(14 results)
