ABSTRACT
Acoustic emission (AE) has been described in ASTM E610-77 as the class of phenomena whereby transient elastic waves are generated by the rapid release of energy by a localized source or sources within a material, or the transient elastic wave so generated. The transient elastic waves will take a form of displacement vibration in the material which can be detected by diplacement gauges or accelerator gauges. Amplitude distributions are commonly represented as normal or cumulative plots. The studies of the AE intensity and the b-value show that fracturing occurs in rocks during the whole loading period, but the fracturing features are different for the linear and nonlinear deformation periods. The present study showed that the tested rock types can be divided into three groups according to the AE activity: The Kaiser effect is evident; AE activity for all stress levels and no evident Kaiser effect; Very low AE activity.
