| Project/Area Number |
03805040
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
基礎・土質工学
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| Research Institution | Kumamoto University |
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Principal Investigator |
OHTSU Masayasu Kumamoto University, Department of Civil and Environmental Engineering, Professor, 工学部, 教授 (80109016)
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| Project Period (FY) |
1991 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1992: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1991: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Acoustic Emission / Moment Tensor Analysis / Crack / アコ-スティック・エミッション / モ-メントテンソル解析 |
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| Research Abstract |
An application of a moment tensor analysis to acoustic emission (AE) is studied to develop a prediction technique of crack propagation. A moment tensor inversion based on P wave amplitude is employed to determine six independent tensor components. A computer code named SiGMA (simplified Green's functions for the moment tensor analysis) is developed for the AE inversion analysis. To classify crack type and to determine crack orientation from moment tensor components, a unified decomposition of eigenvalues is proposed. The aim of the decomposition is to determine the proportion of shear and tensile contribution on AE sources, and to classify cracks into a crack type of the dominant motion. The SiGMA inversion and the unified decomposition are applied to AE waveforms detected during an in-situ hydrofracturing test. AE waveforms detected by eight accelerometers deployed during the hydrofracturing test are analyzed. Crack types and orientations determined are in reasonable agreement with a predicted failure plane from bore-hole TV observation. The results suggest that tensile cracks are generated first at weak seams, and then shear cracks follow on the opened joints.
The SiGMA procedure is modified to solve the 2-D problem and is applied to experiments of a 2-D model with an internal slit. Mixed-mode crack propagation from the slit under uniaxial-compression is investigated and AE waveforms are recorded by a four-channel AE system. Crack locations, crack types, and crack orientations are determined from AE waveforms, based on the moment tensor analysis. The results are compared with crack trajectory observed in the model. The results confirm that the SiGMA analysis is applicable to predicting failure process of subsurface materials.
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