下向き円錐孔底ひずみ法の測定精度に及ぼす接着剤の影響と地圧評価の高精度化 [in Japanese] The Effect of an Adhesive on Accuracy of Rock Stress Measurement by Overcoring Method [in Japanese]
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By performing experiments in the laboratory, we verified how the measuring accuracy of the Downward Compact Conical-ended Borehole Overcoring (DCCBO) technique is affected by the time dependence of the mechanical characteristics of an adhesive to bond the strain cell together. In order to quantify the mechanical characteristics of the adhesive by the correct evaluation of experimental results, we determined the strain coefficients using numerical model including models of adhesive and strain cell.<BR>Consequently, we found that the best evaluation of experimental results measured two hours after affixing the strain cell, was achieved when Young's modulus was 1.45 MPa and Poisson's ratio was 0.00. We also demonstrated that proposed method was capable of highly accurate rock stress evaluation.<BR>Performing in-situ tests, we clarified the requirements for the general characteristics of the adhesive and the strain cell (epoxy section). Young's modulus of adhesive and strain cell (epoxy section) should be set to about 100 MPa for moderately hard or hard rocks having a Young's modulus of about 10 GPa or greater and to about 10 MPa for soft rocks having a Young's modulus of about 1.0 GPa.
Shigen-to-Sozai 123(2), 68-74, 2007-02-25
The Mining and Materials Processing Institute of Japan