Authors: Dight, PM; Dyskin, AV


Cite As:
Dight, PM & Dyskin, AV 2008, 'On the Determination of Rock Anisotropy for Stress Measurements', in Y Potvin, J Carter, A Dyskin & R Jeffrey (eds), Proceedings of the First Southern Hemisphere International Rock Mechanics Symposium, Australian Centre for Geomechanics, Perth, pp. 575-585.

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Abstract:
The traditional methods of in situ stress determination can be seriously affected by rock anisotropy, which necessitates both development of the corresponding interpretation methods and accurate determination of the elastic characteristics of the anisotropic rocks. In this contribution we consider the method of determination of anisotropic moduli by testing small subcores drilled in different directions. Rock anisotropy is often induced by the presence of joints, foliation, schistosity, bedding or similar features. In the case when the spacing between the theses features exceeds the length of the subcores the results of moduli determination in separate subcores shows considerable variability. A mechanism of this variability lies in the fact that a particular subcore may or may not be intersected by a joint. We show that despite this, the averaging procedure used in the method of moduli reconstruction, developed previously by the authors, can still be successfully applied, since the averaging over the subcores recovers the large-scale moduli. However, the standard deviation associated with the randomness of joint-subcore intersection can in some case be very large (potentially unlimited) which explains the observed variability.

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