Preferred orientations of open microcracks in granite and their relation with anisotropic elasticity

Takemura, Takato and Golshani, Aliakbar and Oda, Masanobu and Suzuki, Kenichiro (2003) Preferred orientations of open microcracks in granite and their relation with anisotropic elasticity. International Journal of Rock Mechanics and Mining Sciences, 40 (4). pp. 443-454. ISSN 1365-1609

Abstract

In order to study how to deal with open microcracks in rock, anisotropic behaviors of Oshima granite were investigated by carrying out wave velocity tests and uniaxial compression tests, together with observations of microcracks under an optical microscope equipped with a universal stage. Anisotropy in the longitudinal wave velocity VL and secant deformation modulus E10 at 10% strength is caused by pre-existing open microcracks, not by pre-existing healed microcracks. The structural anisotropy formed by open microcracks, which is quantitatively represented by a second-rank tensor (called crack tensor), is in good agreement with the directional changes of E10 and VL: The mechanical, as well as structural, anisotropy shows rhombic symmetry with orthogonal symmetry axes in the directions roughly normal to the rift, grain and hardway planes, which are parallel to the major joint sets in the field. Since longitudinal wave velocity changes drastically depending on the density and orientation of open microcracks in granitic rocks, it is suggested that the crack tensor can be determined from non-destructive wave velocity tests. The elastic modulus tensor theoretically formulated in terms of the second-rank crack tensor can be used, as a first-order approximation at least, to describe the anisotropic elasticity of Oshima granite induced by pre-existing open microcracks. It is of particular importance to point out that the micro-scale structure by open microcracks is geometrically similar to the macro-scale structure by joints and faults (scale independent). This finding strongly suggests that some of the conclusions related to open microcracks are applicable to deal with macro-scale cracks in rock masses.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Depositing User: Dr Aliakbar Golshani
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Agricultural, Civil and Environmental Engineering
Date Deposited: 29 Oct 2007 07:42
Last Modified: 02 Jul 2013 22:53
Uncontrolled Keywords: microcracks, rock mechanics
Fields of Research (FOR2008): 09 Engineering > 0914 Resources Engineering and Extractive Metallurgy > 091402 Geomechanics and Resources Geotechnical Engineering
Identification Number or DOI: doi: 10.1016/S1365-1609(03)00014-5
URI: http://eprints.usq.edu.au/id/eprint/3458

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