1993 Fiscal Year Final Research Report Summary
Co-operative Study on a New Rock Fracture Mechanics based on Fractal Geometry
| Project/Area Number |
04305001
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| Research Category |
Grant-in-Aid for Co-operative Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
広領域
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| Research Institution | Tohoku University |
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Principal Investigator |
TAKAHASHI Hideaki Tohoku Univ., Faculty of Engineering, Professor, 工学部, 教授 (10005267)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAYASU Hideki Tohoku Univ., Department of Information Science, Professor, 大学院情報科学研究科, 教授 (00183062)
ITO Keisuke Kobe Univ., Faculty of Science, Professor, 理学部, 教授 (00030792)
HASHIDA Toshiyuki Tohoku Univ., Fraculty of Engineering, Associate Professor, 工学部, 助教授 (40180814)
MATSUKI Kouji Tohoku Univ., Faculty of Engineering, Professor, 工学部, 教授 (10108475)
ABE Hiroyuki Tohoku Univ., Faculty of Engineering, Professor, 工学部, 教授 (00005266)
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| Project Period (FY) |
1992 – 1993
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| Keywords | FRACTURE / FRACTAL / SUBSURFACE FRACTURES / NUMERICAL SIMULATION / ROCK |
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| Research Abstract |
The observed fractal nature of both fault length distributions and earthquake magnitude-frequency distribution suggests that there may be a relationship between the structure of active fault systems and the resulting seismicity. Here, we present the first experimental evidence for a correlation between the fractal dimension of fracture length distribution D and acoustic emission (AE) b-value based on a series of tensile fracture mechanics tests on crystalline rock, carried out in different environmental conditions, both air-dry water-saturated at ambient temperature and pressure. The constant stress intensity, K_I, and quantitative analyzes of the resulting fracture patterns were carried out on the same specimens. It is found that AE b-values, ranging from 1.0 to 2.3, correlate negatively with normalized stress intensity K_I/K_<IC>, where K_<IC> is the fracture toughness of the specimen. The fractal dimension of fracture length distribution D, ranges from 1.0 to 1.7. Fluid presence has a first-order influence on both the AE and structure produced in these experiments. For experiments at low stress or high fluid content, the activation of the stress corrosion mechanism for K_I<K_<IC> leads to a greater relative proportion both of small cracks and of low amplitude acoustic emissions, reflected in higher values of D and b. The fractal dimension D is found to correlate positively with the AE b-value.
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