scholarly journals Acoustic Emission Response Characteristics of Anthracitic Coal under Uniaxial Compression

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Haiyan Wang ◽  
Gongda Wang ◽  
Guojun Zhang ◽  
Feng Du ◽  
Ji Ma
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Coal Sample ◽  
Compression Process ◽  
Deformation And Failure ◽  
Response Characteristics ◽  
Fracture Evolution ◽  
Anthracite Coal ◽  
Coal Deformation

The damage evolution of coal is accompanied by the generation of acoustic emission (AE) signal. Through the analysis and research of the AE response characteristics of coal deformation and failure, it is helpful to reveal the initiation, propagation, and fracture evolution of microcracks in coal. In this work, taking the anthracite coal as research object, the basic mechanical parameters of the coal samples were obtained by ultrasonic tests and uniaxial compression experiments. Meanwhile, the AE response characteristics of coal samples during uniaxial compression were obtained through AE experiments. The results show that when the density is low, the wave velocity of the coal sample decreases with the increase of density. When the density is higher than a certain value, the wave velocity of the coal sample increases with the increase of density. Through the measurement of ultrasonic wave velocity, it is found that there is some nonuniformity and anisotropy in raw coal samples. The ring counts, energy counts, and AE events with time in uniaxial compression process have approximately normal distribution. The AE events are concentrated in the elastic stage and yield stage, and the energy amplitude of AE events is higher in the plastic stage. Compared with the ring counts and energy counts, the AE events have a good positioning function, which can better reflect the evolution of internal cracks of coal samples during uniaxial compression.

scholarly journals Acoustic emission response characteristics of anthracitic coal under uniaxial compression

2020 ◽  
Author(s):  
Feng Du ◽  
Kai Wang ◽  
Guojun Zhang ◽  
Gongda Wang ◽  
Qian Zhang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Coal Sample ◽  
Compression Process ◽  
Deformation And Failure ◽  
Response Characteristics ◽  
Fracture Evolution ◽  
Anthracite Coal ◽  
Coal Deformation

Abstract The damage evolution of coal is accompanied by the generation of acoustic emission (AE) signal. Through the analysis and research of AE response characteristics of coal deformation and failure, it is helpful to reveal the initiation, propagation and fracture evolution of micro cracks in coal. In this work, taking the anthracite coal as research object, the basic mechanical parameters of coal samples were obtained by ultrasonic tests and uniaxial compression experiments. Meanwhile, the AE response characteristics of coal samples during uniaxial compression were obtained through AE experiments. The results show that when the density is low, the wave velocity of coal sample decreases with the increase of density. When the density is higher than a certain value, the wave velocity of coal sample increases with the increase of density. Through the measurement of ultrasonic wave velocity, it is found that there are some non-uniformity and anisotropy in raw coal samples. The distribution of ring count, energy count and AE events with time in uniaxial compression process is approximately normal distribution. The AE events are concentrated in the elastic stage and yield stage, and the energy amplitude of AE events is higher in the plastic stage. Compared with the ring count and energy count, the AE events have good positioning function, which can better reflect the evolution of internal cracks in coal samples during uniaxial compression.

scholarly journals Mechanical Properties and Acoustic Emission Characteristics of Karst Limestone under Uniaxial Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Jianxun Chen ◽  
Qingsong Wang ◽  
Jiaqi Guo ◽  
Yanbin Luo ◽  
Yao Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Water Content ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Brittle Failure ◽  
Shear Failure ◽  
Testing Machine ◽  
Natural State ◽  
Saturated State

Firstly, I-RPT ultrasonic detector was used to test the wave velocity of karst limestone with different initial microstructure and water content. Then, RMT-150B rock testing machine and DS2-16B acoustic emission system were used to test the acoustic emission (AE) under uniaxial compression. Mechanical properties and AE characteristics were obtained during rock failure. The detailed relationship between stress-strain and AE characteristics was studied in this paper. Research results indicated the following: (1) For samples with many primary fissures and defects, wave velocity in dry state was larger than that in its natural state. From natural state to saturated state, the wave velocity tended to increase. For samples with good integrity, wave velocity increased with increasing of water content. (2) In the dry state, the samples presented tension failure. In saturated state, the samples presented tension-shear failure. For samples with cracks and good integrity, samples showed brittle failure. For samples with many corrosion pores which showed ductile damage under natural and saturated state, the spalling phenomenon was enhanced under saturated state. (3) With increasing of water content, the peak stress and AE peak reduced dramatically. In brittle failure, AE peak could be considered a sign of failure. In ductile failure, AE activity decreased gradually with the decrease of stress. (4) The mechanical properties and AE characteristics corresponding to four main fracture propagation types were also discussed.

scholarly journals Size Effect of Concrete Specimens on the Acoustic Emission Characteristics under Uniaxial Compression Conditions

2017 ◽  
Vol 2017 ◽  
pp. 1-12
Author(s):  
Jianbo Wu ◽  
Enyuan Wang ◽  
Xuekun Ren ◽  
Mingwei Zhang
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Uniaxial Compression ◽  
Stress Level ◽  
Peak Stress ◽  
Deformation And Failure ◽  
Nonlinear Growth ◽  
Concrete Materials ◽  
Felicity Ratio ◽  
Loading Methods

Acoustic emission (AE) experiments under uniaxial compression and cyclic loading-unloading compression conditions were performed using different sizes of cubic concrete specimens. The influences of the loading methods and the concrete sizes on the mechanical parameters and the concrete AE activities were analyzed. The loading method was found to have great impact on the deformation, failure, and energy dissipation of concrete materials. With the increase of the material size, the uniaxial compressive strength of the concrete specimens gradually decreased, while the corresponding strain of peak strength increased first and then decreased. The elasticity modulus fluctuated irregularly. Under the uniaxial compression conditions, five AE patterns corresponding to the deformation and failure of the concrete materials were observed. A significant nonlinear relationship was found between the AE and the stress level. The cumulative AE rings at the peak stress showed nonlinear growth with the increase of the concrete size. Based on an established relationship between the cumulative AE rings and the stress level, the necessary conditions for the existence of the quiet AE period were given. Under the uniaxial cyclic loading-unloading compression conditions, the Felicity ratio decreased first and then increased as the stress increased. The research results have some guiding significance to AE-based monitoring of internal stress evolution of coal, rock, and concrete materials and thereby enable assessment of their stability.

Uniaxial Compression with Acoustic Emission Experimental Study on Rock Damage Process

2012 ◽  
Vol 204-208 ◽  
pp. 173-176
Author(s):  
Jing Hong Liu ◽  
Xiao Hua Liu ◽  
Wen Han
Keyword(s):  
Acoustic Emission ◽  
Crack Propagation ◽  
Uniaxial Compression ◽  
Failure Process ◽  
Structure Stability ◽  
Uniaxial Compression Test ◽  
Concrete Material ◽  
Deformation And Failure ◽  
Disaster Assessment ◽  
Contrast Analysis

Acoustic emission technique is an important technique for monitoring crack propagation and failure process of rock, coal and concrete material. A uniaxial compression test with acoustic emission monitoring on coal and rock samples’ deformation and failure process were carried out. Failure precursor information of rock, coal and concrete material were studied through contrast analysis the experiment result include acoustic emission signals, strain, load correlation of sample inner crack propagation to failure process. The test provided necessary data to further understand on rock burst failure disaster. The test result provides a theoretical basis for further application of acoustic emission for prediction coal rock dynamic disaster, assessment rock and concrete structure stability and study rock concrete material failure process mechanism.

Study on Energy Accumulation and Damage Evolution of the Coal and Rock Using Acoustic Emission Test

2011 ◽  
Vol 105-107 ◽  
pp. 1597-1602 ◽  
Author(s):  
You Gang Wang ◽  
Xiang Feng Liu
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Solid Material ◽  
Damage Variable ◽  
Geometrical Parameters ◽  
Compression Process ◽  
Energy Accumulation ◽  
Ae Energy

Rocks and other rocklike solid materials have inherent defects inside. The defects of rock will be evolved under loading. The evolution process and extent of defects can be described by the damage variable. But which physical or geometrical parameters can be used to define the damage, there has no consistent conclusion domestic and aboard. Moreover, limited by the method of experimental, it is difficult to obtain the parameters to depict the damage variable directly. In order to obtained the evolution law of the interior defects in the solid material, the non-conduct geophysical prospecting measure as AE (Acoustic Emission) will be the leading measure to prospect the interior defects and it’s evolution under outside loading. In the present paper, the AE method was used to obtain the AE parameters during the uniaxial compression process of coal and rock. Therefore, uniaxial compression and AE tests on coal and mudstone were conducted, and the curves among the AE energy accumulation, stress and strain were obtained after analyzing the results of tests data. Based on the principle of damage mechanics and thermodynamics, the damage evolution of coal and rock was deduced through analyzing the experimental results, the curves of damage and AE accumulation were obtained also. By analyzing and fitting the curves of damage and AE energy accumulation, the relation between the AE energy accumulation and stress-strain was obtained and verified through the experimental data.

Study of the Damage Evolution of Concrete with Different Initial Defect Rates under Uniaxial Compression with Acoustic Emission Technology

2021 ◽  
pp. 1-27
Author(s):  
Yanlong Li ◽  
Junhao Chen ◽  
Lifeng Wen ◽  
Junzhong Wang ◽  
Kangping Li
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Load Level ◽  
Internal Damage ◽  
Cumulative Impact ◽  
Kaiser Effect ◽  
Initial Defect ◽  
Response Characteristics ◽  
Cumulative Function ◽  
Damage Process

It is important to evaluate the internal damage of concrete under load conditions in order to evaluate its stability and usability for building applications. In this study, the uniaxial compression of concrete with initial defect was performed, and the internal damage of concrete was monitored by acoustic emission(AE) technology in real time to study the damage process and mechanism. The mechanical properties of concrete specimens with different initial defect were determined, and the cumulative impact count of AE was recorded. The response characteristics of AE in the process of concrete compression and damage were obtained. According to the analysis of the influence of the initial defect on the Kaiser effect and since the irreversibility of the AE process is related to the degree of damage caused by the material under the pre-load, it was determined that the initial defect will aggravate the damage inside the concrete under the same load level. Based on the statistics and analysis of the Weibull cumulative function, the correlation between AE parameters and damage variables was discussed.

scholarly journals Desorption and Transport of Temperature-Pressure Effect on Adsorbed Gas in Coal Samples from Zhangxiaolou Mine, China

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Xiaohu Zhang ◽  
Wenxin Li ◽  
Gan Li
Keyword(s):  
Uniaxial Compression ◽  
Negative Pressure ◽  
Coal Sample ◽  
Coupling Effect ◽  
Test System ◽  
Effect Of Temperature ◽  
Compression Process ◽  
Sem Images ◽  
Adsorbed Gas ◽  
Roadway Stability

Abstract The development of coal seam fissures and gas migration process caused by mining disturbance has an extremely important influence on gas control and roadway stability. In this study, the desorption, diffusion, and migration tests of adsorbed gas under the coupling effect of temperature and uniaxial compression were conducted on four coal samples from Zhangxiaolou mine, using the temperature and pressure coupling test system of deep coal rocks. The test confirms that the higher the temperature, the faster the desorption and emission of the adsorbed gases in the coal, and the larger the volume of the emitted gases. Meanwhile, it is found that the adsorbed gases in the coal samples of Zhangxiaolou mine are carbon dioxide and methane in the order of content. It is found that during the uniaxial compression process, several large negative values of the pressure of the emitted gas occur during the stable growth stage of the crack. This indicates that the crack expansion makes a new negative pressure space inside the coal sample, and the negative pressure values increase continuously during the unstable growth phase of the crack until the coal sample is destroyed. And after the axial pressure is removed, the escaped gas pressure shows a large positive value due to the rebound of the coal matrix and the continuous desorption of a large amount of adsorbed gas from the new crack location, which has a significant hysteresis with respect to the occurrence of the peak stress. Meanwhile, the SEM images of the coal samples before and after the test are analyzed to confirm the cause of the negative pressure generation.

scholarly journals Laboratory Study of Deformational Characteristics and Acoustic Emission Properties of Coal with Different Strengths under Uniaxial Compression

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1070
Author(s):  
Shuangwen Ma ◽  
Han Liang ◽  
Chen Cao
Keyword(s):  
Plastic Deformation ◽  
Acoustic Emission ◽  
Bearing Capacity ◽  
Uniaxial Compression ◽  
Coal Sample ◽  
Hard Coal ◽  
Dissipation Energy ◽  
Deformation Stage ◽  
Soft Coal ◽  
Ae Counts

Acoustic emission (AE) can reflect the dynamic changes in a material’s structure, and it has been widely used in studies regarding coal mechanics, such as those focusing on the influence of loading rate or water content change on the mechanical properties of coal. However, the deformational behavior of coals with various strengths differs due to the variation in microstructure. Hard coal presents brittleness, which is closely related to certain kinds of geological disasters such as coal bursts; soft coal exhibits soft rock properties and large deformation mechanical characteristics. Therefore, conclusions drawn from AE characteristics of a single coal sample have application limitations. This paper studies the deformation patterns and AE characteristics of coals with different strengths. A uniaxial compression experiment was carried out using coal samples with average uniaxial compressive strengths of 30 MPa and 10 MPa; the SAEU2S digital AE system was used to measure the AE counts, dissipation energy, and fracturing point distributions at each deformation stage of the different coals. The results show that the bearing capacity of hard coal is similar to that of the elastic stage and plastic deformation stage, but it may lose its bearing capacity immediately after failure. Soft coal has a relatively distinct stress-softening deformation stage and retains a certain bearing capacity after the peak. The AE counts and dissipation energy of hard coal are significantly higher than those of soft media, with average increases of 49% and 26%, respectively. Via comparative analysis of the distribution and development of internal rupture points within soft coal and hard coal at 15%, 70%, and 80% peak loads, it was observed that hard coal has fewer rupture points in the elastic deformation stage, allowing it to maintain good integrity; however, its rupture points increase rapidly under high stress. Soft coal produces more plastic deformation under low loading conditions, but the development of the fracture is relatively slow in the stress-softening stage. We extracted and summarized the AE characteristics discussed in the literature using one single coal sample, and the results support the conclusions presented in this paper. This study subdivided the deformation process and AE characteristics of soft and hard coals, providing a theoretical guidance and technical support for the application of AE technology in coal with different strengths.

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