Quantitative damage assessment of in-situ rock mass using acoustic emission technique

Abstract

From the perspective of long-term stability of a waste repository, the real-time monitoring and damage assessment of rock mass are critical issues in a deep geological disposal, which is saliently characterized by an extremely long containment time, high temperature from the decay heat of the spent fuel, and saturated condition with the groundwater. Recently the acoustic emission (AE) technique has been recognized as a promising method for the real-time structural health monitoring of a repository. AE has long been widely used to evaluate the damage mechanism because it is very sensitive to the initiation and growth of cracks in materials. While, most damage assessments in rock using the AE technique have been focused on a qualitative analysis such as detecting the onset of crack generation or crack source location, very little effort has been made to use micro-seismic AE monitoring to quantify the damage of a rock mass. The primary objective of this study, therefore, is to obtain an in-situ damage evolution curve in a rock mass, and to subsequently propose a more reliable methodology for quantifying the rock mass damage (degree of damage, corresponding strength of rock mass, and their predictions) based on real-time AE monitoring. For this purpose, the estimation of the damage evolution curve, that is, the normalized degree of damage vs. the normalized stress, is obtained from an in-situ rock mass, and its reliability is confirmed through theoretical verification procedures. For a systematic approach for this purpose, this thesis is mainly composed of a site characterization of KURT rock mass, a laboratory study, an in-situ application, and verification and utilization. As part of a site characterization, the mechanical, hydraulic and dynamic behaviors of the KURT rock mass are preferentially measured from the various in-situ tests. In detail, the deformation modulus, permeability, and dynamic shear modulus of the rock mass are estimated, which can be used a...