An experimental study on the validity of Kaiser effect in stress measurements by Acoustic Emission Method (AEM)

The acoustic emission method utilizes the Kaiser effect for inferring the stress state. Since stress tenser has 6 independent components, uniaxial or triaxial tests in 6 different directions are carried out. The acoustic emission response differs when the (deviatoric) stress level exceeds the one at which material was previously subjected to. The fundamental complexity is that the earth's crust has a stress history. As a result, one may find one or several stress levels during actual experiments. The question is how to select or define the one, which reflects the stress level that rock was subjected to. An experimental study on the acoustic emission responses of initially unstressed rock-like materials under uniaxial loading conditions was performed. On the basis of these experimental results, the validity of Kaiser effect for inferring stress state by considering the stress level with respect to its uniaxial compressive strength is checked and the applicability of the method for inferring the crustal stresses is discussed.