Estimation of Damage Evolution within an In Situ Rock Mass Using the Acoustic Emissions Technique under Incremental Cyclic Loading

The acoustic emissions (AE) technique has been regarded as a promising method for real-time structural health monitoring of a waste repository and is widely used to evaluate the damage mechanism. However, relatively little effort has been made to use AE monitoring to evaluate the quantitative damage assessment of a rock mass. The objective of this study was to identify the progressive damage evolution of an in situ rock mass based on AE monitoring under a dynamic loading condition, which could serve as primary information for quantifying rock-mass damage. The shape of the damage evolution curve in granite was first determined from a uniaxial compression test with incremental cyclic loading. Based on the results of a laboratory test, the in situ damage evolution curve of a rock mass was subsequently estimated from in situ tests using a Goodman jack and simultaneous AE monitoring in the Underground Research Tunnel of the Korea Atomic Energy Research Institute. With regard to in situ estimation of damage evolution, numerical simulation was also applied to infer the localized strength of a rock mass, in which elastic constants were measured using in situ tests and applied as the basic input parameters. The method suggested in this study could contribute to quantification of rock mass damage from AE observations.