Abstract
Triaxial compressive stress was re-loaded to estimate the pre-stress using the Kaiser effect. In the case of cyclic incremental loading of differential stress until post-failure region, the remarkable AE increase appeared at pre-releasing stress level. The stress level at which the Kaiser effect was observed under the re-loading of hydrostatic stress corresponded to the pre-confining stress. The pre-confining stress, peak strength and residual stress were also able to be estimated under the re-loading of hydrostatic stress and differential stress from the Kaiser effect. Frequency estimated from ringdown counts and duration time of AE signal changed at the Kaiser effect point, which was determined by calculating the AE evevt count rate increment.
