Journal Article Estimation of Fracture Toughness of Anisotropic Rocks by Semi-Circular Bend (SCB) Test Under Water Vapor Pressure

Kataoka, Minami  ,  Obara, Yuzo  ,  Kuruppu, Mahinda  ,  カタオカ, ミナミ  ,  オバラ, ユウゾウ  ,  片岡, みなみ  ,  尾原, 祐三  ,  クルップ, マヒンダ

48 ( 4 )  , pp.1353 - 1367 , 2015-07 , Springer Vienna
In order to investigate the influence of water vapor pressure in surrounding environment on mode I fracture toughness (KIc) of rocks, Semi-Circular Bend (SCB) tests under various water vapor pressures were conducted. The water vapor is one of the most effective agents which promote stress corrosion of rocks. The range of the water vapor pressure used was 10-2 to 103 Pa, and two anisotropic rock types, African granodiorite and Korean granite were used in this testing work. Measurement of elastic wave velocity and observation of thin sections of these rocks were performed to investigate the micro structures of the rocks. It was found that the distribution of inherent micro cracks and grains have a preferred orientation. Two types of specimens in different orientations, namely Type-1 and Type-3 were prepared based on the anisotropy identified by the differences of the elastic wave velocity. KIc of the both rock types was dependent on the water vapor pressure in the surrounding environment and decreased withincreasing the water vapor pressure. It was found that the degree of the dependence isinfluenced by the orientation and density of inherent micro cracks. The experimental results 2 also showed that KIc depended on the material anisotropy. A fracture process was discussed on the basis of the geometry of fractures within fractured specimens visualized by X-ray CT method. It was concluded that the dominant factor causing the anisotropy of KIc is the distribution of grains rather than inherent micro cracks in these rocks.

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