ISRM Suggested Method for Laboratory Acoustic Emission Monitoring

Acoustic emission (AE) is defined as high-frequency elastic waves emitted from defects such as small cracks (microcracks) within a material when stressed, typically in the laboratory. AE is a similar phenomenon to microseismicity (MS), as MS is induced by fracture of rock at an engineering scale (e.g., rockbursts in mines), that is, in the field. Thus, seismic monitoring can be applied to a wide variety of rock engineering problems, and AE is a powerful method to investigate processes of rock fracture by detecting microcracks prior to macroscopic failure and by tracking crack propagation. A basic approach involves using a single channel of data acquisition, such as with a digital oscilloscope, and analyzing the number and rate of AE events. Perhaps the most valuable information from AE is the source location, which requires recording the waveform at several sensors and determining arrival times at each. Thus, investing in a multichannel data acquisition system provides the means to monitor dynamics of the fracturing process. The purpose of this suggested method is to describe the experimental setup and devices used to monitor AE in laboratory testing of rock. The instrumentation includes the AE sensor, preamplifier, frequency (noise) filter, main amplifier, AE rate counter, and A/D (analog-to-digital) recorder, to provide fundamental knowledge on material and specimen behavior in laboratory experiments. When considering in situ seismic monitoring, the reader is referred to the relevant ISRM suggested method specifically addressing that topic (Xiao et al. 2016).