Experimental Investigation on Influence Factors of Acoustic Emission Activity in Coal Failure Process

Yang, Hengquan; Wen, Guangrui; Hu, Qianting; Li, Yuanyuan; Dai, Linchao

doi:10.3390/en11061414

Cited by 25 publications

(18 citation statements)

References 36 publications

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“…He et al [19] carried out single-face dynamic unloading tests under truetriaxial conditions for limestone samples, pointing out that the frequency amplitude of AE signals varies with coal bump stages. Yang et al [20] reported that the external stress condition has a transition effect on the AE event energy distribution and AE activity pattern. Kuksenko et al [21] found that the relaxation of the polarization is identical in nature for both cases and is basically a thermally activated process.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties of Bump‐Prone Coal with Different Porosities and Its Acoustic Emission‐Charge Induction Characteristics under Uniaxial Compression

Ding

Xiao

et al. 2019

Advances in Civil Engineering

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Discreteness of mechanical property affected by the intimal damage, which emerged with various degrees of material composition and geological structure, is the difference in porosity macroscopically. Although various porosities directly affect fracture activity, damage evolution and mechanical behaviour of coal bring on the bump-prone assessment error, and disaster happened “ahead of time” in deep underground energy source exploration, little research to date has focused on them. In this paper, the mechanical properties of bump-prone coal samples with different porosities were studied by uniaxial compression test and the initial damage caused by gangue and organic fracture in coal observed by CT. The result indicated that the evolution of coal strength and the logarithm of porosity were expressed by a linear negative correlation and the elastic modules decreased with the initial damage increased. A new quantitative description of damage variables is established by theoretical derivation to reflect the process of cracks formation and expiation in coal, based on volumetric strain and initial porosity. According to the Mohr–Coulomb principle, the effective stress of coal sample with higher the porosity is more likely to reach the shear strength and destruction. The amplitudes and accumulation of AE energy and charge pulse indeed vary with the stress loading stages and strength. The frequency of AE waveform is dominated in three bands (1∼50 kHz, 100∼150 kHz, and 175∼200 kHz) and that of charge induction had one frequency band 1∼100 Hz, and the amplitudes of time domain and main frequency components increased with stress improved. Both of them originated from cracks and belong to homologous signals, crack development bound to be accompanied by stress wavelet, not necessarily free charge; meanwhile, charge pulse being emerged means there must be cracks interaction and the acoustic emission signals are generated prior to charge induction.

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Section: Introductionmentioning

confidence: 99%

Mechanical Properties of Bump‐Prone Coal with Different Porosities and Its Acoustic Emission‐Charge Induction Characteristics under Uniaxial Compression

Ding

Xiao

et al. 2019

Advances in Civil Engineering

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“…Near peak strength point, with the increase of initial stress, the change trend of amplitude changed from "low-high" to "low-highlow" and the signal quantity is less and more concentrated, which indicates that the energy distribution characteristic changed from dispersed under low initial stress to concentrated under high initial stress; however, the energy remained calm all the time, which indicates that the failure form of saturated limestone was gradual. On the other hand, near rock-failure point, with the increase of initial stress, the change trend of amplitude changed from "intermittent gradual decrease" to " not appear," which indicates that the rock-failure behavior and AE event evolution form changed from ductility to brittleness [25]. The phenomena above can be used as the precursory information of peak strength point and rockfailure point.…”

Section: Different Initial Stressesmentioning

confidence: 94%

Limestone Acoustic Emission Evolution Characteristics Under Different Experimental Loading and Unloading Conditions

Liu

Zhou

et al. 2020

Front. Phys.

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To study the acoustic emission evolution characteristics of saturated limestone under different loading and unloading paths, three cyclic loading and unloading tests were conducted with different loading rates and initial cyclic peak stresses, and acoustic emission monitoring was performed simultaneously. The results indicate that, during loading and unloading, the intermediate-frequency signals of saturated rock exhibit a variation trend of sparse–dense–sparse signals, whereas the low-frequency signals are continuously and massively produced. With the increase in the loading rate, the development trends of cumulative hits and energy become closer, and the development form of ringing count changes from N-type to U-type and then to N-type. The slight increase period and attenuation period are extended, whereas the intense growth period and postpeak calm period are shortened. With an increase in the initial cyclic peak stress, the change in cumulative energy is more obvious than that in cumulative hits near the rock failure. The development form of the ringing count changes from U-type to W-type and then to N-type, and each period is first shortened and then extended. With the increase in loading rate, the increase in the slow-change period tends to change from gradually increasing to increasing and then decreasing. By contrast, the increase in the step tends to change to a gradual increase. With the increase in the initial cyclic peak stress, the duration of and increase in the energy in the step and the slow-change period tend to decrease and then increase.

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“…In the production process of an underground coal mine, production activities such as roadway excavation and coal face mining will cause strata movement and stress redistribution around the stope. us, a mining stress field is generated, and the stress changes continuously with mining activity [1][2][3][4]. Its superposition with the original rock stress acts on surrounding coal seams, the roof, and floor strata, which is a typical cyclic loading condition [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Study on Failure Modes and Energy Evolution of Coal-Rock Combination under Cyclic Loading

Song

Liu

Tan

et al. 2020

Shock and Vibration

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The loading modes and roof lithology have a significant influence on the mechanical properties of coal seams. To reveal the failure modes and energy evolution law of underground coal during the mining process, conventional uniaxial and uniaxial cyclic loading tests were carried out on three types of samples: coal, rock, and coal-rock combinations. The results show that the samples mainly behave with three failure modes (shear slip, tensile splitting, and fracture), and all the coal sections in the coal-rock combinations fail, whereas most rock sections remain intact. The compressive strength of the coal-rock combination is higher than coal and much smaller than rock. Compared with the conventional uniaxial loading condition, both the maximum deformation before failure and Young’s modulus under the cyclic loading condition are greater, and the latter increases quadratically with the cycle index. The energy densities are also calculated, and their variations are analysed in detail. The results show that with increasing cycle index, both the elastic energy stored in the sample and the dissipated energy increase in a quadratic function, and the failure process becomes more intense. This research reveals the failure modes, deformation characteristics, and energy evolution of the coal-rock combination under different loading conditions, which can provide strong support for controlling underground surrounding rocks of the coal face and roadway in coalmines.

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Experimental Investigation on Influence Factors of Acoustic Emission Activity in Coal Failure Process

Cited by 25 publications

References 36 publications

Mechanical Properties of Bump‐Prone Coal with Different Porosities and Its Acoustic Emission‐Charge Induction Characteristics under Uniaxial Compression

Mechanical Properties of Bump‐Prone Coal with Different Porosities and Its Acoustic Emission‐Charge Induction Characteristics under Uniaxial Compression

Limestone Acoustic Emission Evolution Characteristics Under Different Experimental Loading and Unloading Conditions

Study on Failure Modes and Energy Evolution of Coal-Rock Combination under Cyclic Loading

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