Numerical simulation and fractal analysis of mesoscopic scale failure in shale using digital images

Wu, Zhonghu; Zuo, Yujun; Wang, Shanyong; Yi, Tongsheng; Chen, Shijiang; Yu, Qìng; Li, Wei; Sunwen, Jibin; Xu, Yunfei; Wang, Ruyue; Li, Bingfeng

doi:10.1016/j.petrol.2016.06.036

Cited by 44 publications

(33 citation statements)

References 34 publications

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“…The 3-D box-counting dimension (BCD) calculations can accurately reflect crack evolution law in the shale. The results indicate that the cracks have a more complex pattern and rough surface at an orientation of 90 • , due to crossed secondary cracks and shear failure.Various experimental methods, e.g., electromagnetic radiation (EMR), acoustic emission (AE), micro-seismic (MS), infrared technique, high speed digital imaging, and computerized tomography (CT), have been used to analyze the mechanical behavior of rocks (including shale) during uniaxial or triaxial loading [15][16][17][18][19][20][21]. CT scanning has been widely applied in the investigation of damage propagation since 1997, due to the three-dimensional (3-D) visualization and high-resolution imaging [22][23][24][25][26][27][28].…”

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confidence: 99%

Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression

et al. 2018

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The mechanical properties and fracture propagation of Longmaxi shale loading under uniaxial compression were measured using eight cylindrical shale specimens (4 mm in diameter and 8 mm in height), with the bedding plane oriented at 0 • and 90 • to the axial loading direction, respectively, by micro computed tomography (micro-CT). Based on the reconstructed three-dimensional (3-D) CT images of cracks, different stages of the crack growth process in the 0 • and 90 • orientation specimen were revealed. The initial crack generally occurred at relatively smaller loading force in the 0 • bedding direction specimen, mainly in the form of tensile splitting along weak bedding planes. Shear sliding fractures were dominant in the specimens oriented at 90 • , with a small number of parallel cracks occurring on the bedding plane. The average thickness and volume of cracks in the 90 • specimen is higher than those for the specimen oriented at 0 • . The geometrical characterization of fractures segmented from CT scan binary images shows that a specific surface area correlates with tortuosity at the different load stages of each specimen. The 3-D box-counting dimension (BCD) calculations can accurately reflect crack evolution law in the shale. The results indicate that the cracks have a more complex pattern and rough surface at an orientation of 90 • , due to crossed secondary cracks and shear failure.Various experimental methods, e.g., electromagnetic radiation (EMR), acoustic emission (AE), micro-seismic (MS), infrared technique, high speed digital imaging, and computerized tomography (CT), have been used to analyze the mechanical behavior of rocks (including shale) during uniaxial or triaxial loading [15][16][17][18][19][20][21]. CT scanning has been widely applied in the investigation of damage propagation since 1997, due to the three-dimensional (3-D) visualization and high-resolution imaging [22][23][24][25][26][27][28]. Kawakata et al. used CT to study the initial mesoscopic damage characteristics of rock materials, and observed spatial fault development in granite undergoing compression [29,30]. In the experiment, only the damaged specimens, rather than the entire process from crack initiation to specimen destruction, were scanned, and then observed by 3-D reconstruction of X-ray CT images. To examine the entire process, Ge et al. investigated rock compression with a real-time CT test [23]. Through the use of the industrial CT images, the rock meso-damage propagation law was revealed. Rock failure started with micro-pore and micro-crack compression, growth, bifurcation, and development, followed by fracture. Sun et al. displayed real-time deformation in backfill body under loading using industrial CT in several slices, and provided insights into the process of faulting [31]. However, the relatively low spatial resolution and image quality of conventional industrial CT is not suitable for fine-grained rocks. Furthermore, the 3-D information was not fully captured or used, which limited the accuracy of further calculation ...

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Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression

et al. 2018

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“…50 In Equation (15), S is E 0 , σ c , and K; S 0 is the average value corresponding thereto; and the specific values of the mechanical properties of the sample are shown in Table 1. 31 Table 2 shows the shale compressive strength obtained by the test. The inclination angle α is the angle between the bedding plane and the horizontal direction.…”

Section: Numerical Model Of Shalementioning

confidence: 99%

“…In addition, shale usually contains flaky joints, which causes shale to have different mechanical properties and fracture modes in different directions. [28][29][30] Wu et al 31 used the RFPA2D-DIP numerical software to simulate shale filled with calcite. The shale final failure modes were different under different loading conditions, and the compressive strength showed obvious anisotropy.…”

Section: Introductionmentioning

confidence: 99%

Acoustic and fractal analyses of the mechanical properties and fracture modes of bedding‐containing shale under different seepage pressures

Lou

Yin

et al. 2020

Energy Science & Engineering

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“…Multiple methods have been used to study the pore structure of coal, including mercury intrusion porosimetry, liquid nitrogen adsorption, nuclear magnetic resonance, electron microscopy, and digital image analysis. Scanning electron microscopy (SEM) imaging provides unique advantages for the quantitative analyses of pore characteristics in porous media (Wu et al 2016). Highresolution SEM imaging, capable of identifying pores and matrices of different gray levels, has become an important tool for analyzing micro-pore structures (Desbois et al 2011;Pan et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional SEM image-based analysis of coal porosity and its pore structure

Zou

She

Peng³

et al. 2020

Int J Coal Sci Technol

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A quantitative analysis of the porosity, pore size distribution, and fractal dimensions of pores is significant for studying the pore structure characteristics of coal. This study utilized 12 anthracite coal samples from the Sihe mining area to explore the pore structure characteristics of the coal therein. Hundred randomly selected points on each sliced coal sample were imaged via scanning electron microscopy, and a total of 1200 images were used for the analysis. The porosity and fractal dimensions of the coal samples were analyzed via digital image processing and box-counting dimension methods. This method is characterized by extensive graphical analysis, and the results are based on statistical methods. These were also used to analyze the structural and development characteristics of the microscopic pores in the coal. The results reveal that the surface porosity obtained via digital image processing was 16.11% lower than that measured experimentally. The fractal dimension and porosity of the pore surface were fitted to a natural logarithmic curve. The rate of change in the pore fractal dimension depends on the porosity such that, to some degree, a greater porosity is associated with more complex pore structures, a higher degree of micropore development, and improved pore connectivity.

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Numerical simulation and fractal analysis of mesoscopic scale failure in shale using digital images

Cited by 44 publications

References 34 publications

Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression

Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression

Acoustic and fractal analyses of the mechanical properties and fracture modes of bedding‐containing shale under different seepage pressures

Two-dimensional SEM image-based analysis of coal porosity and its pore structure

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