scholarly journals Study on Acoustic Emission Characteristics and Mechanical Behavior of Water-Saturated Coal

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Muhammad Ali ◽  
Enyuan Wang ◽  
Zhonghui Li ◽  
Haishan Jia ◽  
Dexing Li ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Mechanical Behavior ◽  
Uniaxial Compression ◽  
Engineering Practice ◽  
Slow Increase ◽  
Soaking Time ◽  
Emission Signal ◽  
Secondary Cracks ◽  
Water Saturated ◽  
Ae Counts

In terms of coal’s stability and failure, soaking time and water content play a significant role in geotechnical engineering practice. To determine the soaking time effect on the mechanical behavior of coal samples and the response of AE (acoustic emission) signal throughout loading, the samples with different soaking times (0–120 hours (h)) were prepared and tested under uniaxial compression. AE signals were continuously monitored during loading to examine the AE characteristic response via the AEwin Express-8.0 system. The results revealed that the mechanical characteristics of the coal samples decreased with an increase in soaking time. When coal samples were subjected to uniaxial compression, AE events occurred due to the formation of the cracks, which further propagated to cause coal fracture. AE counts and the accumulative counts fluctuated with time and corresponded very well to the load. Therefore, AE counts and the trend of the accumulative counts of AE qualitatively explained the rupture of the coal under stress. In addition, the variation in trends of AE counts, AE accumulative counts, and load with time at various phases of all samples were obtained. It is concluded that AE counts increase suddenly during a slow increase phase and peak at the active increase phase. During the attenuation phase, the AE counts first decrease significantly with stress drop, but also a slight increase was observed due to the initiation of secondary cracks. These research results are of great significance as a precursor in coal and rock failure.

scholarly journals Dynamic Mechanical Behavior of Dry and Water Saturated Igneous Rock with Acoustic Emission Monitoring

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Jun Guo ◽  
Guo-rui Feng ◽  
Ting-ye Qi ◽  
Pengfei Wang ◽  
Jian Yang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Mechanical Behavior ◽  
Igneous Rock ◽  
Water Injection ◽  
Brittle Behavior ◽  
Cyclic Loading And Unloading ◽  
Cyclic Loading Tests ◽  
Water Saturated ◽  
Water Contents

The uniaxial cyclic loading tests have been conducted to study the mechanical behavior of dry and water saturated igneous rock with acoustic emission (AE) monitoring. The igneous rock samples are dried, naturally immersed, and boiled to get specimens with different water contents for the testing. The mineral compositions and the microstructures of the dry and water saturated igneous rock are also presented. The dry specimens present higher strength, fewer strains, and rapid increase of AE count subjected to the cyclic loading, which reflects the hard and brittle behavior and strong burst proneness of igneous rock. The water saturated specimens have lower peak strength, more accumulated strains, and increase of AE count during the cyclic loading. The damage of the igneous rocks with different water contents has been identified by the Felicity Ratio Analysis. The cyclic loading and unloading increase the dislocation between the mineral aggregates and the water-rock interactions further break the adhesion of the clay minerals, which jointly promote the inner damage of the igneous rock. The results suggest that the groundwater can reduce the burst proneness of the igneous rock but increase the potential support failure of the surrounding rock in igneous invading area. In addition, the results inspire the fact that the water injection method is feasible for softening the igneous rock and for preventing the dynamic disasters within the roadways and working faces located in the igneous intrusion area.

scholarly journals Acoustic Emission Multi-Parameter Analysis of Dry and Saturated Sandstone with Cracks under Uniaxial Compression

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1959 ◽  
Author(s):  
Hongru Li ◽  
Rongxi Shen ◽  
Dexing Li ◽  
Haishan Jia ◽  
Taixun Li ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Fractured Rock ◽  
Rock Fracture ◽  
Failure Process ◽  
Parameter Analysis ◽  
Small Scale ◽  
Rock Interaction ◽  
Secondary Cracks ◽  
Ae Signals

In order to study the mechanics and acoustic emission (AE) characteristics of fractured rock under water-rock interaction, dried and saturated sandstone samples with prefabricated double parallel cracks were prepared. Then, uniaxial compression experiments were performed to obtain their AE signals and crack propagation images. The results show that water reduces the strength and fracture toughness of fractured sandstone and enhances plasticity. After saturation, the samples start to crack earlier; the cracks grow slowly; the failure mode is transformed from shear failure along the prefabricated cracks to combined shear and tensile failure; more secondary cracks are produced. The saturated samples release less elastic energy and weaker AE signals in the whole failure process. However, their AE precursor information is more obvious and advanced, and their AE sources are more widely distributed. Compared with dry specimens, the AE frequencies of saturated specimens in the early stage of loading are distributed in a lower frequency domain. Besides, the saturated samples release less complex AE signals which are dominated by small-scale signals with weaker multi-fractal characteristics. After discussion and analysis, it is pointed out that this may be because water makes rock prone to inter-granular fracture rather than trans-granular fracture. The water lubrication also may reduce the amplitude of middle-frequency band signals produced by the friction on the fracture surface. Multi-fractal parameters can provide more abundant precursory information for rock fracture. This is of great significance to the stability of water-bearing fractured rock mass and its monitoring, and is conducive to the safe exploitation of deep energy.

The EMD Analysis AE Signals of Rock Failure under Uniaxial Compression

2014 ◽  
Vol 571-572 ◽  
pp. 845-852
Author(s):  
Tian Jun Zhang ◽  
Sheng Hong Yu ◽  
Jin Hu Ren ◽  
Wei Cui
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Acoustic Emission Signal ◽  
Wavelet Packet ◽  
Testing Machine ◽  
Waveform Analysis ◽  
Mode Analysis ◽  
Emission Signal ◽  
Mode Decomposition ◽  
Emd Method

The wavelet packet basis is difficult to be extracted by wavelet analysis at present. To solve this problem, an experiment of Acoustic Emission under uniaxial compression is conducted by SAEU2S acoustic Emission system and Electro-hydraulic servo universal testing machine and the method of empirical mode analysis is adopted to explore the acoustic emission signal in this paper. Firstly with the method of empirical mode decomposition, the acoustic emission signal is decomposed into the forms of intrinsic mode function with several local time scale and residual components, and then these data is analyzed. After the noise-reducing IMF and residual components are refactored, the error between the final and the initial reconstruction signals is less than 10-6. The experiment indicates that the EMD method is effective in processing the local rock acoustic emission signals. The EMD method also provides an efficient way to predict deformation trend of rock damage through deformation of waveform analysis.

Rock’s Acoustic Emission and Damage Deformation Characteristic in Uniaxial Compression Condition

2012 ◽  
Vol 170-173 ◽  
pp. 486-491 ◽  
Author(s):  
Zi Hong Guo ◽  
Qian Tao ◽  
Bao Xian Liu ◽  
Chao Luo ◽  
Li Meng ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Deformation Characteristic ◽  
Constitutive Models ◽  
Emission Characteristic ◽  
Uniaxial Compression Test ◽  
Strength Based ◽  
Damage Constitutive Model ◽  
Set Up ◽  
Ae Counts

Rock’s uniaxial compression test is completed and the datum is analyzed, then relationship between loading time and AE amplitude, AE counts sum, AE total energy’s released rate come out. Rock’s critical damage is defined which equal result of one minus ratios of residual strength to critical strength. Based on strain equivalence discipline, damage constitutive models related with acoustic emission characteristic are set up. With damage constitutive models established with AE counts sum and AE total energy serving as damage variables respectively and testing datum, the relationship between rock’s damage and stress and strain is described. Then conclusions come out: 1) damage constitutive model with AE counts sum serving as damage variable manifest rock’s damage increasing process and accords with testing result better; 2) theoretical curve is well consistent with testing curve at rock’s peak strength zone.

scholarly journals Experimental Investigation of Progressive Failure Processes Using 3D Acoustic Emission Tomography

2021 ◽  
Vol 9 ◽  
Author(s):  
Yan Cheng ◽  
Paul Hagan ◽  
Rudrajit Mitra ◽  
Shuren Wang ◽  
Hong-Wei Yang
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Failure Modes ◽  
Progressive Failure ◽  
Three Dimensional ◽  
Stress Conditions ◽  
Compression Tests ◽  
Tomographic Images ◽  
Fracture Development ◽  
Ae Counts

In this paper, the potential of 3D acoustic emission (AE) tomography technique in demonstrating fracture development and delineating stress conditions was examined. Brazilian tests and uniaxial compression tests were monitored by 3D AE tomography. AE counts, AE source locations and 3D tomographic images of locally varying velocity distributions were analyzed along with stress and strain measurements. Experimental results revealed two distinct failure processes between Brazilian tests and uniaxial compression tests indicated by differences in AE counts, source locations and the temporal variation of velocity. Furthermore, the development of micro-cracks showed by the results correlated well with theoretical analysis and experimental observations. Additionally, stress patterns, failure modes and final failure planes were indicated by AE locations and velocity tomography. Three-dimensional velocity tomographic images indicated the anisotropy of samples caused by stresses as well. These results confirm the usefulness of AE tomography as a method to monitor stress induced failure and the potential of AE tomography for delineating stress conditions and predicting rock failure.

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