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Applied Sciences
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Application of Acoustic Emission (AE) on Rock Samples
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Application of Acoustic Emission (AE) on Rock Samples

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Acoustics and Vibrations".

Deadline for manuscript submissions: closed (31 May 2019) | Viewed by 23108

Special Issue Editor

Prof. Dr. Gerd Manthei

E-Mail Website
Guest Editor
THM University of Applied Sciences, 35390 Gießen, Germany
Interests: acoustic emission; moment tensor analysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

the application of acoustic emission technique during laboratory testing on rock samples is used to understand better the failure process of rock. The nature of tectonic earthquakes from observations of microscale fracture phenomena is a popular topic. Many researchers discussed the process of foreshocks, main shocks, and aftershocks from AE activity monitored through failure of rock specimens. Other studied the fracturing process of rock and discussed the relation between microcracking and inelastic deformation. Very common is the examination of focal mechanisms of AE activity during laboratory test on rock samples. Many researchers have used AE in novel ways. In this Special Issue of the Acoustics section of Applied Sciences, we seek contributions to compile resent study in this field. We also seek contributions describing case histories of AE applications to rock specimens that have achieved the goals of AE measurements and do so by giving adequate technical information supporting the success stories.

Prof. Dr. Gerd Manthei
Guest Editor

Manuscript Submission Information

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Keywords

  • rock samples
  • acoustic emission
  • microcracking
  • event counting
  • source location
  • energy release
  • Gutenberg-Richter relation
  • source mechanism

Published Papers (7 papers)

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Research

12 pages, 4766 KiB  
Article
Evolution of b-Value and Fractal Dimension of Acoustic Emission Events During Shear Rupture of an Immature Fault in Granite
by Xinglin Lei
Appl. Sci. 2019, 9(12), 2498; https://doi.org/10.3390/app9122498 - 19 Jun 2019
Cited by 21 | Viewed by 3310
Abstract
The present study investigated the evolutions of b-value and fractal dimension of acoustic emission (AE) events during shear rupture of a naturally-created rough fracture in a granite specimen under triaxial compression. Acoustic emission signals were monitored by 16 sensors mounted directly on [...] Read more.
The present study investigated the evolutions of b-value and fractal dimension of acoustic emission (AE) events during shear rupture of a naturally-created rough fracture in a granite specimen under triaxial compression. Acoustic emission signals were monitored by 16 sensors mounted directly on the surface of the specimen, and AE waveforms were sampled at 16 bits and 25 MHz. Reliable hypocenters were determined using P-wave arrival times picked up from the waveforms. Acoustic emission magnitude was determined from the maximum amplitude monitored by two peak detectors, which have a relative magnitude range of 0 to 2.75. A three-dimensional X-ray computed tomography scan was performed after the test to explore the fracture geometry. Acoustic emission activity was initiated during hydrostatic compression. With increasing differential stress, AEs demonstrated an increasing event rate, a decrease (from approximately 1.8 to 1.6) with a subsequent precursory increase (from 1.6 to 1.8) in fractal dimension, a quick decrease in b-value (from 1.0 to approximately 0.5), and a quick increase in fractal dimension (from 1.8 to 2.0). The exponentially increasing event rate, gradually decreasing b-value, and slowly increasing fractal dimension may be an intermediate-term indication of fault reactivation. In contrast, a progressively increasing event rate, a rapid drop in b-value, and a rapid increase in fractal dimension may facilitate short-term prediction of large events, which reflect the rupture of large patches. Acoustic emission hypocenters were clustered on the entire fracture surface. The present study sheds some light on detecting early signs of fault reactivation by monitoring injection-induced seismicity in areas with faults of different maturity. Full article
(This article belongs to the Special Issue Application of Acoustic Emission (AE) on Rock Samples)
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13 pages, 2744 KiB  
Article
Acoustic Emission Characteristics of Graded Loading Intact and Holey Rock Samples during the Damage and Failure Process
by Xiaofei Liu, Huajie Zhang, Xiaoran Wang, Chong Zhang, Hui Xie, Shuai Yang and Weikai Lu
Appl. Sci. 2019, 9(8), 1595; https://doi.org/10.3390/app9081595 - 17 Apr 2019
Cited by 24 | Viewed by 2424
Abstract
Rock burst is the result of the development and extension of micro-cracks during the loading process of large-scale rock mass in underground space engineering. Dynamic monitoring results by acoustic emission (AE) can accurately perceive the inner fracture evolution of rock mass and effectively [...] Read more.
Rock burst is the result of the development and extension of micro-cracks during the loading process of large-scale rock mass in underground space engineering. Dynamic monitoring results by acoustic emission (AE) can accurately perceive the inner fracture evolution of rock mass and effectively warn about its induced disasters early. By contrastive testing the AE parameters in the whole fracture process of the intact and holey rock samples under graded loading, their spatiotemporal evolution rules were analyzed in this paper, and the damage model of rock samples based on AE localization events was established to analyze the relationship between rock damage and loads. The results show that: (1) Under the condition of grading loading, AE parameter increases with the increase of axial stress and show three states, respectively, which are slow-growth, stabilization and rapid increasing; meanwhile, the damage of the sample has a cumulative effect with time. (2) The AE counts and energy are highly correlated with the fracture of the sample that the more severe the damage of the sample, the faster the crack propagation as well as the higher the acoustic emission counts and the energy amplitude. The damage state of granite sample can be accurately judged by two parameters to character the damage evolution process and fracture mechanism. (3) Compared with the intact rock sample, due to the pressure relief effect of the hole, the rock sample containing the hole takes a long time in the compaction stage and with higher load stress level. Although the AE counts and energy were lower in the damage process, the general law of their response during damage and instability process still exists. Full article
(This article belongs to the Special Issue Application of Acoustic Emission (AE) on Rock Samples)
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25 pages, 5255 KiB  
Article
Experimental Investigations on the Progressive Failure Characteristics of a Sandwiched Coal-Rock System Under Uniaxial Compression
by Jinwen Bai, Guorui Feng, Zehua Wang, Shangyong Wang, Tingye Qi and Pengfei Wang
Appl. Sci. 2019, 9(6), 1195; https://doi.org/10.3390/app9061195 - 21 Mar 2019
Cited by 32 | Viewed by 2816
Abstract
Overlapped residual coal pillars, together with the surrounding rock strata, play a combined bearing role in ultra-close multiple seam mining. Global stability of the whole bearing system is significant for the mining design, construction, and operation. Laboratory uniaxial compressive experiments for different kinds [...] Read more.
Overlapped residual coal pillars, together with the surrounding rock strata, play a combined bearing role in ultra-close multiple seam mining. Global stability of the whole bearing system is significant for the mining design, construction, and operation. Laboratory uniaxial compressive experiments for different kinds of sandwiched coal-rock specimens are carried out to investigate the progressive failure characteristics and mechanisms. Results show that: (1) The mechanical behavior of the sandwiched coal-rock specimen is mainly divided into four stages during the failure process. The response of the electrical resistivity and the evolution of acoustic emission (AE) energy are in good agreement with the mechanical behaviors at different stages, which are a reflection of the global failure characteristics of sandwiched specimens. (2) The distribution of AE events and the development of local strain can provide further insight into the local failure characteristics of coal elements or rock elements in sandwiched specimens. AE events are more likely to be generated in coal elements, which can propagate across coal-rock interfaces and induce damage to rock elements in a certain area. Similarly, the unbalanced deformation characteristics of coal elements and rock elements are apparently revealed in the progressive failure process. (3) Progressive failure of a sandwiched coal-rock specimen is closely associated with the interactions between the coal elements and rock elements. Initial failure usually appears in the coal elements. At this process, the recovery of elastic deformation and the output of strain energy are observed in the rock elements, which can accelerate the rupture of coal elements. In turn, the dynamic fracture energy generated in the rupture process of coal elements can propagate into rock elements and induce damage to rock elements a certain area. (4) The experimental results are helpful for maintaining the long-term stability of a sandwiched coal-rock system in ultra-close multiple seam mining. Full article
(This article belongs to the Special Issue Application of Acoustic Emission (AE) on Rock Samples)
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15 pages, 2683 KiB  
Article
Experimental Investigation on the Deformability, Ultrasonic Wave Propagation, and Acoustic Emission of Rock Salt Under Triaxial Compression
by Haoran Li, Zhikai Dong, Zuolin Ouyang, Bo Liu, Wei Yuan and Hongwu Yin
Appl. Sci. 2019, 9(4), 635; https://doi.org/10.3390/app9040635 - 14 Feb 2019
Cited by 27 | Viewed by 4082
Abstract
Ultrasonic waves, which constitute an active testing method, and acoustic emissions (AE), which can be applied as passive testing technology, can reveal rock damage processes in different ways. However, few studies so far have simultaneously adopted both, owing to the limitations of the [...] Read more.
Ultrasonic waves, which constitute an active testing method, and acoustic emissions (AE), which can be applied as passive testing technology, can reveal rock damage processes in different ways. However, few studies so far have simultaneously adopted both, owing to the limitations of the experimental apparatus. However, the simultaneous use of both methods can improve the experimental efficiency and help to understand the rock damage evolution more comprehensively. In this study, concurrent experiments of ultrasonic waves and AE activities were carried out on rock salt under uniaxial compression, and the deformation characteristics were measured. The fracture process was divided into four stages with individual characteristics: the elastic compression stage, brittle-ductile transition with crack initiation, brittle-ductile transition with damage initiation, and plastic deformation and strain hardening stage. The ultrasonic wave velocity, crack density, ultrasonic wave amplitude, and attenuation coefficient were obtained to evaluate the damage process. The ultrasonic wave amplitude and the attenuation coefficient were recommended as forecast indicators, owing to their sensitivity and operability of measurement. The confining pressure had an inhibitory effect on crack expansion and on the AE activity, and the damage ultimate stress was defined and determined according to the AE activity and energy release characteristics. Four critical strengths of the crack initiation threshold stress, dilatancy boundary stress, short-term strength, and damage ultimate stress of rock salt were determined and then discussed. These results are valuable in evaluating rock damage and guiding the operation of underground salt caverns. Full article
(This article belongs to the Special Issue Application of Acoustic Emission (AE) on Rock Samples)
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13 pages, 3267 KiB  
Article
An Experimental Investigation of Moisture-Induced Softening Mechanism of Marble Based on Quantitative Analysis of Acoustic Emission Waveforms
by Yiming Huang, Jianhui Deng and Jun Zhu
Appl. Sci. 2019, 9(3), 446; https://doi.org/10.3390/app9030446 - 28 Jan 2019
Cited by 11 | Viewed by 2562
Abstract
The decrease of strength after saturation of rocks is known as moisture-induced softening. To date, there are numerous studies on the mechanism of moisture-induced softening of different rocks. However, due to a lack of effective observational methods, the microcosmic mechanism of moisture-induced softening [...] Read more.
The decrease of strength after saturation of rocks is known as moisture-induced softening. To date, there are numerous studies on the mechanism of moisture-induced softening of different rocks. However, due to a lack of effective observational methods, the microcosmic mechanism of moisture-induced softening still needs to be understood. We collected and processed acoustic emission (AE) signals during the uniaxial compression test of marble specimens. The results of spectral and statistical analysis show that two dominant frequency bands of AE waveforms exist regardless of the specimen’s water content. Additionally, for the AE signals from the saturated specimens, the ranges of the low and high frequency bands are wider than dried rock samples. Besides, since the tensile and shear failures in the rock release low and high dominant frequency AE signals, respectively, the test results of this paper show that micro-shear and micro-tensile failures dominate the final failure of dried and saturated rocks, respectively. Full article
(This article belongs to the Special Issue Application of Acoustic Emission (AE) on Rock Samples)
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16 pages, 10593 KiB  
Article
Acoustic Emission Characteristics During Rock Fragmentation Processes Induced by Disc Cutter under Different Water Content Conditions
by Qibin Lin, Ping Cao, Rihong Cao and Xiang Fan
Appl. Sci. 2019, 9(1), 194; https://doi.org/10.3390/app9010194 - 07 Jan 2019
Cited by 18 | Viewed by 4111
Abstract
Based on a properly modified testing platform and Physical Acoustics Corporation (PAC) Micro-II acoustic emission (AE) system, a series of sequential indentation tests on granite samples with five different water contents was conducted to investigate the effect of the water content on the [...] Read more.
Based on a properly modified testing platform and Physical Acoustics Corporation (PAC) Micro-II acoustic emission (AE) system, a series of sequential indentation tests on granite samples with five different water contents was conducted to investigate the effect of the water content on the rock fragmentation process induced by a tunnel boring machine (TBM) disc cutter. During these tests, the effects of the water content on the characteristics of the peak penetration force, AE events, consumed energy, rock chip volume, and specific energy were analyzed. The results showed that the AE events were associated with the whole second indentation process of the granite. Under conditions with the same water content, the peak penetration forces and the consumed energy were smaller than those in the first indentation force. Additionally, subsequent chips were formed more frequently than the first indentation chips. The specific energy was lower, which meant that the rock breaking efficiency was higher. With the increase in the water content, the acoustic emission events reduced. The peak penetration force and consumed energy decreased with the increase in the water content. The volume of the chips increased significantly as the water content increased. The specific energy was promoted by the increase of the water content and then by the increase in the rock-breaking efficiency of the TBM disc cutter. Full article
(This article belongs to the Special Issue Application of Acoustic Emission (AE) on Rock Samples)
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10 pages, 2782 KiB  
Article
Seismic b-Value for Foreshock AE Events Preceding Repeated Stick-Slips of Pre-Cut Faults in Granite
by Xinglin Lei, Shinian Li and Liqiang Liu
Appl. Sci. 2018, 8(12), 2361; https://doi.org/10.3390/app8122361 - 23 Nov 2018
Cited by 14 | Viewed by 3059
Abstract
In this study, the b-values for acoustic emission (AE) events during stick-slip cycles of pre-cut faults in granite (as an analogue of unfavorably oriented immature faults) under triaxial compression (confining pressure: 40 MPa) are investigated. Using a multi-channel AE waveform recording system [...] Read more.
In this study, the b-values for acoustic emission (AE) events during stick-slip cycles of pre-cut faults in granite (as an analogue of unfavorably oriented immature faults) under triaxial compression (confining pressure: 40 MPa) are investigated. Using a multi-channel AE waveform recording system and two peak detectors, we recorded AE waveforms at 16 bits and at a sampling rate of 25 MHz, as well as the maximum amplitude of AE events with a dynamic range of 55 dB. For stick-slip events, the b-value decreases from 1.2 to 1.5 to approximately 0.6 as the shear stress increases, and then quickly jumps back to 1.0 to 1.3 immediately prior to the dynamic stress drop. The minimum b-value coincides with the maximum event rate and a stress level of 70 to 95% of the shear strength. It is also observed that the AE activity during each cycle was linked with the pre-failure fault slip, which accounts for 30% of the dynamic slip. Our results on b-value evaluation preceding repeated stick-slips can be used as an indicator of the degree of fault maturity and shear stress acting on the fault, which is important in seismic hazard assessment and earthquake prediction, especially for the injection-induced seismicity for fields in which reactivated shear rupture of unfavorable and immature faults or tensile fractures is important. Full article
(This article belongs to the Special Issue Application of Acoustic Emission (AE) on Rock Samples)
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