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Shock and Vibration
Volume 2017, Article ID 9760940, 11 pages
https://doi.org/10.1155/2017/9760940
Research Article

Acoustic Emission Monitoring and Failure Precursors of Sandstone Samples under Various Loading and Unloading Paths

1Geotechnical Research Institute, Hohai University, Nanjing 210098, China
2Nanjing Hydraulic Research Institute, Nanjing 210029, China
3Laixi Water Conservancy Bureau, Laixi 266600, China

Correspondence should be addressed to Jingdong Jiang; moc.qq@662453563

Received 21 July 2017; Accepted 17 October 2017; Published 27 December 2017

Academic Editor: Rafał Burdzik

Copyright © 2017 Jie Xu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

To explore the failure precursors of hard rock, a series of triaxial loading and unloading experiments were carried out on sandstone sample using the acoustic emission systems. The extreme-point symmetric mode decomposition method (ESMD method) was used to denoise and reconstruct the AE data. The AE quiet period in Scheme I becomes much more obvious with the confining pressure increasing, which can be regarded as the precursor information of the sample failure under conventional triaxial compression. Unlike Scheme I, there are no obvious precursory characteristics before failure in Schemes II and III, and the count rate reaches the maximum at the peak point. When the stress ratio ranges from 0.8 to 1.0, the fractal values of acoustic emission can be used to investigate the failure precursors of samples at a lower confining pressure. When the time ratio is greater than 0.8 under higher confining pressures, the fractal values of sandstone samples under unloading paths are rapidly reduced, which can be used to predict rock failure at higher confining pressures.