Abstract
When constructing large caverns such as the one used for an underground powerhouse, it is of extreme importance to assure the stability of the cavern. As one of the techniques for stability monitoring, uniaxial compression tests were performed in various rocks and AE activity was measured. From the examinations of AE activity and the maximum amplitude of a single event, two types of AE occurence patterns and three types of m-value variations were found. When predicting failure modes by means of AE, it is thought that the total AE counts and the m-value can be useful for non-homogeneous rocks. On rocks of schistose or very homogeneous structures, the total AE counts provide useful information on failure prediction but the m-value does not. Furthermore, from the results of spectral analysis of AE signal waves measured, it is found that the dominant frequency increases with increasing load.
