Detection of Cracking Levels in Brittle Rocks by Parametric Analysis of the Acoustic Emission Signals

Determination of the cracking levels during the crack propagation is one of the key challenges in the field of fracture mechanics of rocks. Acoustic emission (AE) is a technique that has been used to detect cracks as they occur across the specimen. Parametric analysis of AE signals and correlating t...

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Bibliographic Details
Published in:Rock mechanics and rock engineering 2016-03, Vol.49 (3), p.785-800
Main Authors: Moradian, Zabihallah, Einstein, Herbert H., Ballivy, Gerard
Format: Article
Language:English
Subjects:
Acoustic emission testing
Analysis
Civil Engineering
Classification
Coalescence
Crack initiation
Crack propagation
Cracking (fracturing)
Earth and Environmental Science
Earth Sciences
Energy
Fracture mechanics
Geology
Geophysics/Geodesy
Microcracks
Original Paper
Parametric analysis
Rocks
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Summary:Determination of the cracking levels during the crack propagation is one of the key challenges in the field of fracture mechanics of rocks. Acoustic emission (AE) is a technique that has been used to detect cracks as they occur across the specimen. Parametric analysis of AE signals and correlating these parameters (e.g., hits and energy) to stress–strain plots of rocks let us detect cracking levels properly. The number of AE hits is related to the number of cracks, and the AE energy is related to magnitude of the cracking event. For a full understanding of the fracture process in brittle rocks, prismatic specimens of granite containing pre-existing flaws have been tested in uniaxial compression tests, and their cracking process was monitored with both AE and high-speed video imaging. In this paper, the characteristics of the AE parameters and the evolution of cracking sequences are analyzed for every cracking level. Based on micro- and macro-crack damage, a classification of cracking levels is introduced. This classification contains eight stages (1) crack closure, (2) linear elastic deformation, (3) micro-crack initiation (white patch initiation), (4) micro-crack growth (stable crack growth), (5) micro-crack coalescence (macro-crack initiation), (6) macro-crack growth (unstable crack growth), (7) macro-crack coalescence and (8) failure.
ISSN:0723-2632
1434-453X
DOI:10.1007/s00603-015-0775-1