Macro- and Meso-Damage Evolution Characteristics of Coal Using Acoustic Emission and Keuence Testing Technique

Zhang, Qi; Li, Xiangchun; Gao, Jiaxing; Jia, Suye; Ye, Xinwei

doi:10.1007/s11053-021-10006-7

Cited by 17 publications

(4 citation statements)

References 35 publications

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“…Based on its theory, the AE waves enable spatial localization of internal cracking sounds of coal samples based on the arrival times acquired by different sensors. For more detailed information about the DS5–16C AE system, please refer to the relevant literature. − …”

Section: Materials and Methodologymentioning

confidence: 99%

Multifractal Characterization of Coal Deterioration Induced by Cyclic Hydraulic Pressure Based on the Acoustic Emission Test and X-ray Microscopy

Yu,

Xing,

Xiang

et al. 2024

Energy Fuels

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Pulsating hydraulic fracturing has been applied in industry to increase gas productivity or clear fluid channel blockage, such as coalbed methane recovery. It produces cyclic hydraulic pressure to generate fatigue damages in coal causing deterioration of the mechanical strength. However, difficulties still exist in the quantification of the coal deterioration in the lab. This work provides a way of measuring the internal events induced by the cyclic hydraulic pressure based on the acoustic emission (AE) test and threedimensional (3D) X-ray microscopy (XRM). It gives a method to quantify the damage in coal with the multifractal dimension and digital image analysis. The results show that the cyclic hydraulic pressure has a great impact on the fracturing behaviors of coal. As the reduction of initial crack pressure is proportional to the pretreated pulse pressure, the AE sensors receive more cracking signals during the whole procedure. For conventional hydraulic fracturing, the AE counts concentrate at the initial crack point with a big pressure drop. However, due to the influence of cyclic hydraulic load, changes exist in the AE count distribution. It represents that the fracture strength has been changed by the cyclic hydraulic loading. The average frequency-rise angle (AF-RA) eigenvalue provides the proportions of tensile and shear failures. It shows that the proportions of tensile and shear failures change from 56.38 and 43.62 to 41.79 and 58.21%, respectively. To observe the internal cracks of coal, the 3D XRM has been applied to directly illustrate the spatial distribution of created cracks. More cracks have been seen in fractured coal samples after higher pulse pressure loading. The multifractal analysis indicates that the AE spectra and computed tomography (CT) images can be characterized by the multifractal dimension. D q monotonically decreases with the increased q value. The relationship of f (α)-α is presented by the inverted U shape. Δf and Δα provide a quantitative analysis of pore structure heterogeneity. It shows that the heterogeneity of pore structure decreases with the increase of pretreated pulse pressures. The change of pore structure heterogeneity has been validated based on the AE localization and the CT images. With the increase of the pulse peak pressure, more microcracks emerge and evenly distribute around the borehole in coal. This work provides an experimental method to quantify the fatigue damage induced by the cyclic hydraulic pressure which is very significant for the investigation of the pulsating hydraulic fracturing.

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Section: Materials and Methodologymentioning

confidence: 99%

Multifractal Characterization of Coal Deterioration Induced by Cyclic Hydraulic Pressure Based on the Acoustic Emission Test and X-ray Microscopy

Yu,

Xing,

Xiang

et al. 2024

Energy Fuels

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“…Coal rock destabilization damage is a dynamic evolution process in which its internal cracks continuously start to crack and expand until penetration. Acoustic emission monitoring technology is considered to be an effective method to study the damage and destruction process of coal rock and to characterize the destruction mechanism of coal rock . Shan et al investigated the effect of water content on the damage characteristics of loaded coal rock with the help of acoustic emission technology .…”

Section: Introductionmentioning

confidence: 99%

“…Acoustic emission monitoring technology is considered to be an effective method to study the damage and destruction process of coal rock and to characterize the destruction mechanism of coal rock. 11 Shan et al investigated the effect of water content on the damage characteristics of loaded coal rock with the help of acoustic emission technology. 12 Cui et al elucidated the relationship between strain and damage variables during uniaxial compression by analyzing the acoustic emission ringing number.…”

Section: Introductionmentioning

confidence: 99%

Damage Evolution Characteristics and Constitutive Model for Coal and Rock under Asymmetric Loading

Wang,

Zhao,

Zhang

et al. 2024

ACS Omega

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Tunnels and shaft mining roadways are often subjected to varying degrees of asymmetric loading due to terrain relief or project excavation. In order to analyze the influence of the asymmetric degree of loading on the mechanical properties and damage rupture law of coal rock, uniaxial compression tests of coal rock under four asymmetric loading modes were carried out, the influence of the asymmetric coefficients of loading on macro- and micromechanical properties of coal and rock was analyzed, and a statistical damage constitutive model of coal and rock was established to reflect the asymmetric loading degree. The results of the study show that the peak stress of the coal rock decreases gradually with the increase in the asymmetric coefficient of loading, and the two are linear functions of each other. The distribution of the acoustic emission ringing count peak value is concentrated under uniform loading, while the acoustic emission ringing count rate presents a multipeak phenomenon under asymmetric loading, and the peak value points are scattered. In the case of asymmetric loading, the stress concentration on the edge of the upper loading plate leads to shear failure, and the microscopic cracks are concentrated near the interface between the loading zone and the nonloading zone. According to the established damage constitutive model, when the damage degree is the same, the larger the asymmetric coefficient, the smaller the strain value, which indicates that the asymmetric loading promotes the damage of coal and rock.

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“…Li et al used high-frequency AE to monitor true triaxial hydraulic fracturing of coal. Zhang et al , used AE in the experiments of coal-bearing rocks and different types of coal to detect the generation of microcracks and the evolution of macroscopic and microscopic failures. Hao et al obtained 3D reconstructed coal samples by CT scanning of bituminous coal with different water contents.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of the Fracture Network Expansion Mechanism and Three-Dimensional Reconstruction Characteristic of High-Rank Coal in Guizhou Province, China

et al. 2023

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To better understand the fracture propagation characteristics and spatial distribution pattern of a high-rank coal reservoir during hydraulic fracturing, a true triaxial physical simulation device was used to conduct a hydraulic fracturing experiment on large-sized raw coal from Zhijin, Guizhou Province, China. Computed tomography technology was used to scan the three-dimensional morphology of the fracture network before and after fracturing, then AVIZO software was used to reconstruct the internal fractures of the coal sample, and fractal theory was used to quantify the fractures. The results show that (1) the sudden increase of the pump pressure curve and acoustic emission signal is an important identification feature of hydraulic fractures, and the in situ stress difference coefficient plays a leading role in the complexity of coal and rock fractures. (2) When a hydraulic fracture encounters a primary fracture in the process of expansion, the opening of the primary fracture, the penetration, bifurcation, and turning of the hydraulic fracture are the main reasons for the formation of complex fractures, and the existence of a large number of primary fractures is the basis for the formation of complex fractures. (3) The fracture shape of coal hydraulic fracturing can be divided into three categories: complex fracture, plane fracture + cross fracture, and inverted T-shaped fracture. The fracture shape is closely related to the original fracture shape. The research results of this paper provide strong theoretical and technical support for coalbed methane mining design such as Zhijin high-rank coal reservoirs.

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Macro- and Meso-Damage Evolution Characteristics of Coal Using Acoustic Emission and Keuence Testing Technique

Cited by 17 publications

References 35 publications

Multifractal Characterization of Coal Deterioration Induced by Cyclic Hydraulic Pressure Based on the Acoustic Emission Test and X-ray Microscopy

Multifractal Characterization of Coal Deterioration Induced by Cyclic Hydraulic Pressure Based on the Acoustic Emission Test and X-ray Microscopy

Damage Evolution Characteristics and Constitutive Model for Coal and Rock under Asymmetric Loading

Experimental Study of the Fracture Network Expansion Mechanism and Three-Dimensional Reconstruction Characteristic of High-Rank Coal in Guizhou Province, China

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