Listening to Rock: Acoustic Emission in Fracture Testing

ABSTRACT: Fracture of a material such as rock involves microcracking, which generates elastic waves known as acoustic emission (AE). These transient waves propagate through the medium with very small amplitudes and high frequencies, and the AE signals carry information about the source, including location and mechanism. The acoustic emission technique is reviewed and basic features of the experimental system are outlined. Analyses involving rates, locations, and source mechanisms are discussed, along with imaging results that support the AE statistics. Data from fracture testing of a brittle rock (quartzite) and a brittle solid (glass) are highlighted to demonstrate the ability of AE to monitor the evolution of fracture.

Joseph Labuz is Professor and Department Head of Civil, Environmental, and Geo- Engineering at the University of Minnesota. He earned his PhD (1985) in civil engineering from Northwestern University. His research interests include the behavior of fluid-saturated rock, fracture of brittle solids, and development of novel apparatus. He is a Fellow of ASCE and ARMA.