Damage constitutive model of gas-bearing coal using industrial CT scanning technology

Wu, Yan; Wang, Dengke; Wei, Jianping; Yao, Banghua; Zhang, Hongtu; Fu, Jianhua; Zeng, Fanchao

doi:10.1016/j.jngse.2022.104543

Cited by 25 publications

(7 citation statements)

References 42 publications

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“…The triaxial stress-displacement test system can perform uniaxial and triaxial loading tests on ϕ25 mm × h50 mm samples, with a maximum axial compression of 100 kN, a maximum confining pressure of 30 MPa, and a loading rate range of 0.1-3 mm/min. The attenuation coefficient of the X-ray intensity and the density of the material satisfy the following equation [24]:…”

Section: Experimental Device and Methodsmentioning

confidence: 99%

Characterization of 3D Displacement and Stress Fields in Coal Based on CT Scans

Li¹,

Pan³

et al. 2022

Mathematics

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Computed tomography (CT) scans were performed on samples of an outburst-prone coal seam at different loading stages. The area and roundness of the CT images were used to quantify the degree of the coal macroscopic deformation under different loads. A spatial matching algorithm was used to calculate the three-dimensional (3D) displacement fields of different regions of interest (ROIs, containing primary fractures, minerals, and only coal) under different loads. The presence of fractures and minerals were found to promote and inhibit displacement, respectively, and the 3D displacement field data followed a normal distribution. A meshfree numerical simulation was used to determine the 3D maximum principal stress, shear stress and displacement fields under different loads. The following results were obtained: fractures and minerals significantly affect the stress state and displacement field distribution features, the maximum principal stresses and shear stresses in different matrices differ significantly, and the presence of minerals and fractures induce a prevalent shear stress in coal and make coal prone to stress concentration.

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Section: Experimental Device and Methodsmentioning

confidence: 99%

Characterization of 3D Displacement and Stress Fields in Coal Based on CT Scans

Li¹,

Pan³

et al. 2022

Mathematics

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“…A large amount of adsorbed gas will reduce the surface free energy of coal, thus weakening coal strength. In addition, the gas adsorbed on the surface of the fracture between matrices will form an adsorption film, which can lubricate and reduce friction resistance . Therefore, it is very important to know how the deformation induced by gas adsorption affects coal permeability.…”

Section: Modelingmentioning

confidence: 99%

Coupling between Damage Evolution and Permeability Model with the Adsorption Effect for Coal under Gas Extraction and Coal Mining Conditions

Ren

et al. 2022

Energy Fuels

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During coalbed methane (CBM) extraction and coal mining, the stress state, adsorption/desorption, and seepage behavior in coal will change significantly, which is the principal cause of the outburst accidents. Therefore, it was considered particularly important to investigate permeability behavior under damage conditions. In this paper, to simulate gas extraction and coal mining conditions, two triaxial seepage experiment schemes were designed: the first relating to the coal seepage experiment of gas pressure reduction under constant external stress (GPR seepage experiment) and the other relating to the coal seepage experiment of gas pressure constant under different confining pressures (GPC seepage experiment). Based on the principle of strain equivalence, the total damage variable was obtained, which revealed the combined result between adsorption stress and external stress. The internal expansion coefficient was introduced into the permeability model, which was developed from the poroelastic deformation theory. Moreover, when the effects of damage evolution on coal permeability were considered, a coal damage-permeability model was proposed. The results revealed that, during the pore pressure reduction process, the coal permeability increased slowly at first and then sharply. When pore pressure was constant, permeability decreased with an increase in confining pressure. Whether it was in the stage of reducing pore pressure or in the whole stress–strain stage, the proposed permeability model had a good correspondence with the experimental results. Finally, the cohesion force expression was modified to take into account the mechanical induced effect and adsorption induced effect on the gas. The effect of adsorbed gas on the coal reservoir stress state (strength criterion and Mohr circle) and in the in situ state was further discussed. The proposed theoretical findings could be applied to CBM extraction and coal mining problems to describe the coal damage evolution and gas seepage behavior.

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“…Microfractures are the main channels for gas and water flow in coal seam and also determine the steady coal mass. ,,, With the development of the X-ray computed tomography (CT) scanning device, the fracture structure and permeability evolution of the coal/rock sample under different stress conditions have been widely investigated by many researchers. By an industrial CT scanner equipped with a loading system, researchers found that the fracture volume and permeability decreased first and then increased during the complete compaction process of coal, exhibiting a U-shaped variation trend involving a decrease stage, an increase stage, and a jump-increase stage. − In addition, by the 3D reconstruction method, Li et al found that the fracture propagation in coal samples is controlled by confining pressure, which also influences the fracture shape and its fractal dimension . For the jointed coal/rock, CT scanning technology was also adopted to reconstruct the fracture surface morphology .…”

Section: Introductionmentioning

confidence: 99%

Evolution of Acoustic Emission and Microcrack in Jointed Coal under Loading and Their Correlations

Wang,

Guan,

et al. 2023

ACS Omega

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Understanding of continuous damage and cracking process of compressed jointed coal is critical to predict its stability. Herein, for jointed coal under uniaxial compression with bedding planes perpendicular (sample A) and parallel (sample B) to the loading direction, an acoustic emission (AE) monitoring device and a computed tomography (CT) scanner were employed to study the damage and cracking process. Furthermore, the correlations between the AE signals and internal fracture parameters were analyzed. Results show that (1) shear and tension cracks are respectively main damage forms in samples A and B; (2) there is a drop valley of variations of AE count fractal dimension (D 1) over time before the stress peak, and compared with sample B, the drop valley for sample A are much wider; (3) many fractures between joint planes formed at yielding and postpeak stages, fracture fractal dimensions (D 2) first increase slightly with loading and then increase significantly at yielding and postpeak stages; especially D 2 of sample A is larger than that of sample B; (4) the accumulative value of D 1 (AD 1) increases with D 2 monotonously, and an expression of porosity or connectivity of the compressed jointed coal was developed, by which the porosity and connectivity of jointed coal could be calculated. The study outcomes could contribute to predict coal stability and the variations of water and gas flowing channels in seam in underground coal mines.

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Damage constitutive model of gas-bearing coal using industrial CT scanning technology

Cited by 25 publications

References 42 publications

Characterization of 3D Displacement and Stress Fields in Coal Based on CT Scans

Characterization of 3D Displacement and Stress Fields in Coal Based on CT Scans

Coupling between Damage Evolution and Permeability Model with the Adsorption Effect for Coal under Gas Extraction and Coal Mining Conditions

Evolution of Acoustic Emission and Microcrack in Jointed Coal under Loading and Their Correlations

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