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Geomechanics and Engineering
  Volume 18, Number 1, May20 2019 , pages 11-20

A new approach for quantitative damage assessment of in-situ rock mass by acoustic emission
Jin-Seop Kim, Geon-Young Kim, Min-Hoon Baik, Stefan Finsterle and Gye-Chun Cho

    The purpose of this study was to propose a new approach for quantifying in situ rock mass damage, which would include a degree-of-damage and the degraded strength of a rock mass, along with its prediction based on real-time Acoustic Emission (AE) observations. The basic approach for quantifying in-situ rock mass damage is to derive the normalized value of measured AE energy with the maximum AE energy, called the degree-of-damage in this study. With regard to estimation of the AE energy, an AE crack source location algorithm of the Wigner-Ville Distribution combined with Biot\'s wave dispersion model, was applied for more reliable AE crack source localization in a rock mass. In situ AE wave attenuation was also taken into account for AE energy correction in accordance with the propagation distance of an AE wave. To infer the maximum AE energy, fractal theory was used for scale-independent AE energy estimation. In addition, the Weibull model was also applied to determine statistically the AE crack size under a jointed rock mass. Subsequently, the proposed methodology was calibrated using an in situ test carried out in the Underground Research Tunnel at the Korea Atomic Energy Research Institute. This was done under a condition of controlled incremental cyclic loading, which had been performed as part of a preceding study. It was found that the inferred degree-of-damage agreed quite well with the results from the in situ test. The methodology proposed in this study can be regarded as a reasonable approach for quantifying rock mass damage.
Key Words
    acoustic emission; quantitative damage; rock mass; wave attenuation; fractal theory; Wigner-Ville distribution; Weibull model
Jin-Seop Kim, Geon-Young Kim and Min-Hoon Baik: Radioactive Waste Technology Development Division, Korea Atomic Energy Research Institute, Daejeon 305-353, Korea

Stefan Finsterle: Finsterle GeoConsulting, Kensington, CA 94708, U.S.A.

Gye-Chun Cho: Department of Civil & Environmental Engineering, Korean Advanced Institute for Science and Technology, Daejeon 305-701, Korea

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