A fractal approach for surface roughness analysis of laboratory hydraulic fracture

Movassagh, Abbas; Haghighi, Manouchehr; Zhang, Xi; Kasperczyk, Dane; Sayyafzadeh, Mohammad

doi:10.1016/j.jngse.2020.103703

Cited by 22 publications

(4 citation statements)

References 37 publications

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“…Upon rock fracture, the width of the inelastic zone significantly decreases to around 10 pixels and remains relatively constant. Notably, the Type I FPZ exhibits distinctive features, mainly attributed to the accumulation of microcracks induced by tensile stress …”

Section: Resultsmentioning

confidence: 99%

“…Notably, the Type I FPZ exhibits distinctive features, mainly attributed to the accumulation of microcracks induced by tensile stress. 34 Figure 9 illustrates the variation in the horizontal displacement field at the crack tip during the loading process of the rock core at a 75% relative humidity. Compared to the saturated rock core, reducing water saturation shortens the length of the inelastic zone.…”

Section: Full-fieldmentioning

confidence: 99%

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Investigating the Effect of Water Saturation on Rock Fracture Characteristics: Some Insights from Digital Image Correlation Technology

Wang,

Deng,

Zhang

et al. 2024

Energy Fuels

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To investigate the fracture characteristics of rocks during the hydraulic fracturing process, Brazilian splitting experiments were conducted on cores with varying water saturations. Digital image correlation (DIC) technology was employed to capture full-field displacement and strain information during the rock fracture, facilitating the calculation of the rock fracture toughness using the path-independent J-integral. Additionally, displacement opening modes and fracture surface morphologies were obtained for rocks with different water saturations. The results show that the rock tensile strength decreases significantly as the water saturation increases. Under higher water saturations, the rock residual strength increases, showing a more obvious ductile failure mode. The fracture surfaces are found to display self-affine regimes, with a Hurst exponent β ≈ 0.62 in saturated conditions and with β ≈ 0.17 in dry conditions. Furthermore, as the integrated area of the crack tip increases, the fracture toughness gradually increases and stabilizes. The observed significant change in fracture toughness under high water saturation may be attributed to the increased plastic zone around the rock crack tip.

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Section: Resultsmentioning

confidence: 99%

Section: Full-fieldmentioning

confidence: 99%

Investigating the Effect of Water Saturation on Rock Fracture Characteristics: Some Insights from Digital Image Correlation Technology

Wang,

Deng,

Zhang

et al. 2024

Energy Fuels

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“…However, during crack propagation, due to differences between the mechanical environment and the coal structure, the crack surface is usually not smooth. To investigate the relationship between crack deformation and fluid flow, some scholars have also carried out accurate quantitative characterization studies on rough surfaces [1,[35][36][37][38]. Overall, the main factor explaining the formation of cracks during coal seam water injection appears to be mechanical damage: the water injection pressure would cause an expansion of the damage range and aggravate the damage [39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

Coupling Mechanism of Coal Body Stress–Seepage around a Water Injection Borehole

Liu

Yang

et al. 2022

Sustainability

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In China, coal seam water injection technology is widely used in the prevention and control of mine gas and dust disasters. The evolution law of stress–seepage field in the range of hydraulic influence in the process of coal seam water injection is the most basic theoretical problem in coal seam water injection technology. Therefore, this paper first uses the radial seepage experimental system to test the permeability of raw coal samples, and then numerically inverts the stress–seepage evolution law of the coal body around the water injection hole. The results show that the coal seam permeability decreases exponentially with the increase in the experimental overburden pressure. The dynamic water intrusion causes the pressure relief area and the stress concentration area to transfer to the deep part of the coal body, and abnormal stress occurs near the water injection hole wall. The composite stress area formed by the superposition of stress and pore water pressure reduces the permeability of the hole wall. During the radial development of water injection, the pore water pressure dropped sharply and eventually tended to zero, while Darcy’s velocity decreased significantly (within the pressure relief zone, it rapidly decreased from 7.26 × 10−3 m s−1 to 2.5 × 10−3 m s−1 (by 65.56%)). Near the initiation point, the maximum step-down height of Darcy’s velocity decreased from 6.73 × 10−3 m s−1 to 5.27 × 10−3 m s−1 (by 22.73%). This can make it clear that the seepage velocity presents a non-Darcy seepage phenomenon under the influence of pore pressure.

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“…e main aim of either the hydraulic-fracturing technique or the presplit blasting technique in treating the hard overlying strata is to generate a series of manmade cracks or fractures [16][17][18]. In practice, it is not very easy to maintain the accurate application of hydraulic fractures/cracks and therefore the effect of which will be somehow affected.…”

Section: Introductionmentioning

confidence: 99%

Presplit Blasting Technique in Treating Hard Overlying Strata: From Numerical Simulation to Field Practice

Yang

Yang²,

Zhang

2021

Advances in Civil Engineering

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The potential dynamic risk of the mined underground space with hard overlying strata is one of the main concerns for coal operators. This paper presents a comprehensive study on treating the hard overlying strata upon the coal seam through the presplit blasting technique. The properties of the overlying strata were firstly investigated and evaluated via the laboratory tests and theoretical analysis. With the consideration of the geological and mining condition of the research area, the critical parameters of the presplit blasting technique (e.g., unsaturation coefficient, borehole spacing, and the slit width) were consequently determined via the numerical simulation with the application of LS-DYNA. Then, the field practice in accordance with the determined parameters was carried out in Yuwu coal mine. The effectiveness of the presplit blasting technique was well verified when the microstructures of the surrounding rock were investigated. The success presented in this paper does not only demonstrate the feasibility of using the presplit blasting technique in treating the hard strata of underground mines but also provide a guideline in determining the critical parameters by the numerical simulation and theoretical analysis from the design aspect.

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A fractal approach for surface roughness analysis of laboratory hydraulic fracture

Cited by 22 publications

References 37 publications

Investigating the Effect of Water Saturation on Rock Fracture Characteristics: Some Insights from Digital Image Correlation Technology

Investigating the Effect of Water Saturation on Rock Fracture Characteristics: Some Insights from Digital Image Correlation Technology

Coupling Mechanism of Coal Body Stress–Seepage around a Water Injection Borehole

Presplit Blasting Technique in Treating Hard Overlying Strata: From Numerical Simulation to Field Practice

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