2002 Fiscal Year Final Research Report Summary
Study on long-term permeability of fracture in rock mass
| Project/Area Number |
12450411
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
資源開発工学
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| Research Institution | Tohoku University |
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Principal Investigator |
MATSUKI Koji Tohoku University, Graduate School of Engineering, Professor, 大学院・工学研究所, 教授 (10108475)
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| Co-Investigator(Kenkyū-buntansha) |
KIZAKI Akihisa Tohoku University, Graduate School of Engineering, Research Associate, 大学院・工学研究所, 助手 (60344686)
SAKAGUCHI Kiyotohshi Tohoku University, Graduate School of Engineering, Assistant Professor, 大学院・工学研究所, 講師 (50261590)
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| Project Period (FY) |
2000 – 2002
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| Keywords | Permeability of fracture / Shear deformation / Time-dependent closure / Theory of viscoelasticity / Confining pressure test / Control of confining pressure / rock |
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| Research Abstract |
For prediction and control of the long-term permeability of a fracture in rock mass, it is indispensable to clarify permeable change of an underground fracture with time. The purpose of this study is to establish a method for prediction of long-term permeability of a fracture. For this purpose, firstly, it was carried out that theoretical study of time-dependent closure of a fracture with rough surfaces under constant normal stress. Secondary, the relaxation modulus of rock was measured by using proposed indentation-test system. Finally, the permeable change of a fracture in the rock under both of shear stress and normal stress with time was clarified experimentally and theoretically.
Main results obtained in this study are summarized as follows:
1) A formula for the relationship between constant normal stress and time-dependent closure as a function of time was derived, based upon the distributions of aperture local minima and their radii. It was shown that the ultimate closure of a fra
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cture under constant normal stress can be estimated from the normal stress-elastic closure curve and the relaxation modulus of rock. The ultimate time-dependent closure was shown to be independent of the normal stress if the elastic closure is linear with the logarithm of the normal stress (Goodman's fracture).
2) Indentation-test system for estimating the relaxation modulus and the elastic constant of rock was developed. A Monte Carlo simulation on time- dependent closure of a fracture under constant normal stress was performed by using the fracture model and the measured relaxation modulus.
The results qualitatively showed that the time-dependent closure for granite is not dependent on normal stress and that for sandstone is dependent on normal stress. However, simulated time-dependent closure was fairly smaller than that of experimental results. It was thought that this difference was the main causes with the size effect by the difference of contact area.
3) Permeability test of a fracture applying shear deformation with constant/uniform normal stress under confining pressure was carried out. Less
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