| Co-Investigator(Kenkyū-buntansha) |
MOGI Kiyoo Earthquake Research Institute. University of Tokyo. Professor, 地震研究所, 教授 (40012893)
HORI Hideuki Faculty of Engineering, University of Tokyo. Associated Professor, 工学部, 助教授 (10181520)
IZUMI Masanori Faculty of Engineering, Tohoku University. Professor, 工学部, 教授 (10005506)
SATAKE Masao Faculty of Engineering, Tohoku University. Professor, 工学部, 教授 (50005188)
TAKAHASHI Hideaki Faculty of Engineering, Tohoku University. Professor, 工学部, 教授 (10005267)
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| Research Abstract |
The aim of this comprehensive research is to construct and systematize rock fracture mechanics through cooprative works between the nationalwide experts working in the fields of mechanical, civil, mining and architectural engineering, and seismology. From the cooperative testing programs and techical discussions with special reference to the development of fracture tooghness testing method, the following results were obtained;
A fracture toughness evaluation method was newly developed, which uses the core based specimens with chevron notches according to ISRM suggested methods. The specimen compliances and stress intensity factors were determined for the core based specimens by 3-D boundary element analyses, and extensive fracture tests were then conducted to examine the influence of specimen size on the measured fracture toughness value. The fracture toughness value determined by the present ISRM methods was found to be strongly specimen size dependent for most types of rock due to rising crack propagation resistance, R, which is caused by the formation of the fracture process (microcracking) zone ahead of the crack tips. Based on this result, the R-curve mothed for evaluating the valid fracture toughness value of rock was proposed. In addition, measurements of tension softening curve for rocks were made on CT specimens of various sizes. The tests showed the feasibility of applying the tension softening model to characterize the growth of the fracture process zone in rocks. Interlaboratory fracture toughness tests of rock (Westerly granite) and concrete are now being conducted, together with the development of the method for detecting the fracture process zone and the examination of the influence of microstructural features on the fracture toughenss, and the results of the research will be used to propose a new fracture toughness testing method which can be applied for concrete and ceramic as well as rock.
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