Application of the Compact Conical-ended Borehole Overcoring Technique to Orthotropic Rock

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  • 円錐孔底ひずみ法の直交異方性岩盤への適用
  • エンスイコウテイヒズミ ホウ ノ チョッコウ イホウセイ ガンバン エ ノ テキヨウ

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Stress-measurement methods based on the overcoring method assume that the rock mass is linearly elastic, isotropic, continuous, and homogeneous. However, a rock mass is actually anisotropic to some degree. In this study, we carried out theoretical, numerical and experimental studies to apply the Downward Compact Conical-ended Borehole Overcoring technique to an orthotropic rock. Numerical experiments with the use of a 3D-FEM analysis were conducted to confirm the applicability and efficiency of the proposed measurement theory.The results showed that the measurement includes a non-negligible error if we do not consider the anisotropy of rock when such anisotropy is strong.For example, the isotropic assumption method gives an error of more than 20 % in the estimation of stress when the degree of anisotropy in the direction of the maximum applied stress exceeds 20 %. On the other hand, the error is less than 5 % in the orthotropic assumption method. Finally, laboratory experiments for four kinds of orthotropic rocks using a true-triaxial compressive apparatus were carried out to verify the efficiency of the proposed measurement theory. These experiments also verified that the proposed method is suitable for use in orthotropic rock.

Journal

  • Journal of MMIJ

    Journal of MMIJ 129 (7), 455-460, 2013

    The Mining and Materials Processing Institute of Japan

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