| Project/Area Number |
04650446
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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 |
Space and upper atmospheric physics
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| Research Institution | Tokuyama College of Technology Civil |
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Principal Investigator |
KUDO Yozo Tokuyama College of Technology, Engineering and Architecture, Professor, 土木建築工学科, 教授 (00035081)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1993: ¥500,000 (Direct Cost: ¥500,000)
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| Keywords | Stress-induced crack / Double-torsion Test / Stress-intensity factor / Anisotropy / Granite / Pre-existing crack / Quartz / 破壊機構 |
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| Research Abstract |
1) Double-torsion test was performed to clarify the role of pre-existing microcracks which are preferentially oriented in granite in relation to a stress-induced crack path. Six kinds of specimen of different crack-opening directions and propagating directions associated with three anisotropy axs of Oshima granite were prepared. After polishing the bottom side of each specimen where the stress-induced crack could possibly propagate, pictures of original rock surfaces were taken by reflecting microscope to identify the pre-existing cracks from the latent stress-induced cracks. In the double-torsion test, crack velocity was controlled at 10^<-6> m/s while systematic anisotropy was observed in stress intensity factors. Thin sections were made so as to maintain the original bottom surfaces of dyed specimens. Thin section analysis was taken as both pre-existing cracks and stree-induced cracks are quantified according to their sizes and orientations. Kinds of mineral grain associated with st
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ress-induced crack path were also classified. Mechanisms which bring upon anisotropy in stress intensity factor were discussed.
2) The stress-induced crack path was divided into two types, transgranular and intergranular cracks, and each path was subdivided with respect to mineral grains. The crack paths were all jagged, and often showed detour around the grain boundary when faced with obstacles like hard grains or preexisting cracks. That is to say, quartz grain playd an important role as an obstacle. Feldspar grain could change the crack path because of its cleavage plane. Biotite grain had a serious effect on the path even when its constitution ratio is very small.
Fractal dimensions of the crack paths were calculated by three methods, as indicators of surface roughness. The fractal dimensions were shown in a slight trend with the change of crack velocity. Mechanisms which bring upon anisotropy in stress intensity factor were discussed. The major role of preexisting cracks within quatz grains was confirmed from the analyzes. Less
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