Application of autocorrelation analysis for interpreting acoustic emission in rock

Vilhelm, Jan; Rudajev, Vladimı́r; Lokajı́ček, T.; Živor, Roman

doi:10.1016/j.ijrmms.2007.11.004

Cited by 38 publications

(11 citation statements)

References 49 publications

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“…Uniaxial compression causes stress concentrations and slippage friction around freeze-thaw induced fractures. Some of the strain energy in the coal is released in the form of elastic waves and these waves can be detected as acoustic emissions (AE) 22 . By collecting the acoustic emission signals from the frozen-thawed coal during the compression, the extension, connection, and failure of the freeze-thaw induced fractures in the coal can be inferred 23 – 25 .…”

Section: Resultsmentioning

confidence: 99%

Factors controlling the mechanical properties degradation and permeability of coal subjected to liquid nitrogen freeze-thaw

Qin

Zhai

Liu

et al. 2017

Sci Rep

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Freeze-thaw induced fracturing coal by liquid nitrogen (LN2) injection exerts a significant positive effect on the fracture permeability enhancement of the coal reservoir. To evaluate the different freeze-thaw variables which modify the mechanical properties of treated coals, the effects of freezing time, number of freeze-thaw cycles, and the moisture content of coal were studied using combined uniaxial compression and acoustic emission testing systems. Freezing the samples with LN2 for increasing amounts of time degraded the strength of coal within a certain limit. Comparison to freezing time, freeze-thaw cycling caused much more damage to the coal strength. The third variable studied, freeze-thaw damage resulting from high moisture content, was restricted by the coal’s moisture saturation limit. Based on the experimental results, equations describing the amount of damage caused by each of the different freeze-thaw variables were empirically regressed. Additionally, by using the ultrasonic wave detection method and fractal dimension analyses, how freeze-thaw induced fractures in the coal was quantitatively analyzed. The results also showed that the velocity of ultrasonic waves had a negative correlation with coal permeability, and the freeze-thaw cycles significantly augment the permeability of frozen-thawed coal masses.

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Section: Resultsmentioning

confidence: 99%

Factors controlling the mechanical properties degradation and permeability of coal subjected to liquid nitrogen freeze-thaw

Qin

Zhai

Liu

et al. 2017

Sci Rep

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“…An explanation for the aforementioned phenomenon is that the intact sandstone is not homogeneous and isotropic on a microscopic level, and different amounts of inherent cracks were generated during its millions or billions of years of evolution. Hence, some AE activities can be detected before the crack closure threshold, and it is normal for a natural intact rock mass to express uniform AE activity distribution until the final fracture [ 36 – 38 ]. However, a restored rock mass with some reinforcement materials, such as an MEYCO-364 injection, can also exhibit fracture sandstone changes in the distribution proportion of the inner cracks, and most of the macroscopic cracks and some microscopic cracks inside the sandstone are filled up with adhesive material.…”

Section: Resultsmentioning

confidence: 99%

Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions

et al. 2015

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Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE) testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three-dimensional damage source locations manifest such that AE events are highly correlated with a strength recovery coefficient; the AE events show a decreasing tendency when the coefficient is larger than 1, and vice versa. This study provides a feasible scheme for the reinforcement of fractured rock masses in underground constructions and reveals an internal mechanism of the crushing process for restored rock masses, which has certain instructive significance.

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“…The autocorrelation method may be used in order to determine the fundamental frequency, as it is often used in measuring signal parameters when noise or random interference occurs [28][29][30][31]. A correlation between two signals is a measure of their similarity.…”

Section: Abrasive Grains Identification Methodologymentioning

confidence: 99%

The identification of abrasive grains in the decohesion process by acoustic emission signal patterns

Sutowski

Nadolny

2016

Int J Adv Manuf Technol

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The article presents the results of basic research focused on the decohesion phenomenon characteristics of selected abrasive grains using acoustic emission signal patterns. On the basis of the recorded signals, their detailed analysis in the time-frequency domain and their characteristic harmonic components were selected. The method developed for estimating the similarity of the harmonic sequences will be further used in a comparative analysis with the degree of similarity of acoustic emission signal patterns to determine the type of grain in the decohesion process inducted by an external force or stress field. The proposed technique of grain recognition can be used in grinding wheel wear diagnostic systems, especially in cases where it is significant for supervision or inspection of cracking and chipping abrasive grain vertices.

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Application of autocorrelation analysis for interpreting acoustic emission in rock

Cited by 38 publications

References 49 publications

Factors controlling the mechanical properties degradation and permeability of coal subjected to liquid nitrogen freeze-thaw

Factors controlling the mechanical properties degradation and permeability of coal subjected to liquid nitrogen freeze-thaw

Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions

The identification of abrasive grains in the decohesion process by acoustic emission signal patterns

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