Rock fracture-toughness determination by the Brazilian test

Guo, Hejun; Aziz, Naj; Schmidt, Lewis C.

doi:10.1016/0013-7952(93)90056-i

Cited by 182 publications

(73 citation statements)

References 11 publications

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“…Figure 10 plots the values of fracture toughness versus the material tensile strength. It can be observed that the proposed method is able to provide a range of values very close to the values of fracture toughness calculated using the method proposed by Guo et al (1993). It is important to consider that the calculated value of the fracture toughness is a function of the position of the crack initiation point.…”

Section: Fracture Toughness Calculationmentioning

confidence: 51%

“…Details of different testing specimens and measured data are presented in Tables 1 and 2. For all specimens, fracture toughness is calculated using the method proposed in Guo et al (1993). This method relies on the value of P min , which is the post-residual load being maintained by each fractured disk.…”

Section: Experimental Methods and Measurementsmentioning

confidence: 99%

“…As specified, for all of the specimens described above, fracture toughness was calculated using the method proposed in Guo et al (1993). However, for specimen A the fracture toughness was calculated using a different methodology, given for this specimen P min value was significantly low to be used for calculating a meaningful value of fracture toughness according to Guo et al (1993).…”

Section: Fracture Toughness Calculationmentioning

confidence: 99%

“…However, for specimen A the fracture toughness was calculated using a different methodology, given for this specimen P min value was significantly low to be used for calculating a meaningful value of fracture toughness according to Guo et al (1993). For this specimen it was decided to directly employ Irwin's equation, which describes the stress field distribution around the crack tip in Fig.…”

Section: Fracture Toughness Calculationmentioning

confidence: 99%

“…In this table, the calculated values are also compared with those values obtained from the method based on theories proposed by Guo et al (1993) and Hobbs (1964). The maximum and minimum values were evaluated considering two different distances between loading point and the crack initiation point.…”

Section: Fracture Toughness Calculationmentioning

confidence: 99%

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Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

et al. 2018

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Reliable prediction of fracture process in shale-gas rocks remains one of the most significant challenges for establishing sustained economic oil and gas production. This paper presents a modeling framework for simulation of crack propagation in heterogeneous shale rocks. The framework is on the basis of a variational approach, consistent with Griffith's theory. The modeling framework is used to reproduce the fracture propagation process in shale rock samples under standard Brazilian disk test conditions. Data collected from the experiments are employed to determine the testing specimens' tensile strength and fracture toughness. To incorporate the effects of shale formation heterogeneity in the simulation of crack paths, fracture properties of the specimens are defined as spatially random fields. A computational strategy on the basis of stochastic finite element theory is developed that allows to incorporate the effects of heterogeneity of shale rocks on the fracture evolution. A parametric study has been carried out to better understand how anisotropy and heterogeneity of the mechanical properties affect both direction of cracks and rock strength.

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Section: Fracture Toughness Calculationmentioning

confidence: 51%

Section: Experimental Methods and Measurementsmentioning

confidence: 99%

Section: Fracture Toughness Calculationmentioning

confidence: 99%

Section: Fracture Toughness Calculationmentioning

confidence: 99%

Section: Fracture Toughness Calculationmentioning

confidence: 99%

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Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

et al. 2018

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Effects of spatial heterogeneity and material anisotropy on the fracture pattern and macroscopic effective toughness of Mancos Shale in Brazilian tests

Sun

Ingraham

et al. 2017

JGR Solid Earth

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For assessing energy‐related activities in the subsurface, it is important to investigate the impact of the spatial variability and anisotropy on the geomechanical behavior of shale. The Brazilian test, an indirect tensile‐splitting method, is performed in this work, and the evolution of strain field is obtained using digital image correlation. Experimental results show the significant impact of local heterogeneity and lamination on the crack pattern characteristics. For numerical simulations, a phase field method is used to simulate the brittle fracture behavior under various Brazilian test conditions. In this study, shale is assumed to consist of two constituents including the stiff and soft layers to which the same toughness but different elastic moduli are assigned. Microstructural heterogeneity is simplified to represent mesoscale (e.g., millimeter scale) features such as layer orientation, thickness, volume fraction, and defects. The effect of these structural attributes on the onset, propagation, and coalescence of cracks is explored. The simulation results show that spatial heterogeneity and material anisotropy highly affect crack patterns and effective fracture toughness, and the elastic contrast of two constituents significantly alters the effective toughness. However, the complex crack patterns observed in the experiments cannot completely be accounted for by either an isotropic or transversely isotropic effective medium approach. This implies that cracks developed in the layered system may coalesce in complicated ways depending on the local heterogeneity, and the interaction mechanisms between the cracks using two‐constituent systems may explain the wide range of effective toughness of shale reported in the literature.

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Marble Discs under Distributed Loading: Theoretical, Numerical and Experimental Study

Markides

Sarris

Pazis

et al.

Fracture of Nano and Engineering Materials and Structures

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Rock fracture-toughness determination by the Brazilian test

Cited by 182 publications

References 11 publications

Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

Effects of spatial heterogeneity and material anisotropy on the fracture pattern and macroscopic effective toughness of Mancos Shale in Brazilian tests

Marble Discs under Distributed Loading: Theoretical, Numerical and Experimental Study

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