Propagation and Interactions of Acoustic Waves in a Waveguide Attached at the Surface of Rock

Measurements of the dynamic response of a rock mass are inevitable in the systematic long-term monitoring and the maintenance of the radioactive waste disposal repository. With this point of view, AE (acoustic emission) detection is considered to be a promising technique for monitoring the in-situ performance of a rock mass. In this study, the propagation and interactions of guided acoustic waves in a waveguide connector, which is required in an in-situ application of an AE monitoring system were investigated and the coupling methods of a waveguide to the surface of rock mass were compared. The changes in acoustic wave amplitude, time delay, frequency variation, and system transfer function were measured between the waveguide and a rock sample. Subsequently the waveguide coupling conditions filled with epoxy were compared with a mechanical type of coupling for the validity of field application. The results derived from this study can be valuable information for the quantitative analysis of signal processing in AE source localization and the degree of crack damage in a radioactive waste repository.