Experimental and numerical investigation of cracked chevron notched Brazilian disc specimen for fracture toughness testing of rock

Wei, Mingdong; Dai, Feng; Xu, Nuwen; Zhao, Tao

doi:10.1111/ffe.12672

Cited by 65 publications

(27 citation statements)

References 60 publications

(113 reference statements)

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“…Axial load is imposed on the surface of specimens at a constant loading rate of 0.05 mm/minute until the specimen fails. Besides load‐displacement measurements, the experimental observations also involve AEs . In this study, a total of four AE sensors with a resonance frequency of about 150 kHz and a fairly flat response from 0 to 400 kHz are used.…”

Section: Experimental Procedures and Data Processingmentioning

confidence: 99%

“…Brittle rocks are complex geological mediums, which always contain preexisting flaws such as faults, joints, and voids . Under the actions of external force, the tips of micro flaws probably become the source of initiation of new cracks.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, the modes I and II fracture toughness and the mixed mode fracture toughness of rocks have attracted much attention. Typical Brazilian‐type compression tests, three‐point bending tests, and impact experiments were performed creatively to investigate the mechanical problems associated with the fracture toughness of rocks and the related crack evolutions. Experimental investigations, involving different flaw configurations, advance the understanding of the roles of preexisting flaws in rock failure.…”

Section: Introductionmentioning

confidence: 99%

“…Brittle rocks are complex geological mediums, which always contain preexisting flaws such as faults, joints, and voids. 1,2 Under the actions of external force, the tips of micro flaws probably become the source of initiation of new cracks. The initiation and propagation of new cracks lead to the progressive degradation of the strength and stiffness of rock mass.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Progressive failure of brittle rocks with non‐isometric flaws: Insights from acousto‐optic‐mechanical (AOM) data

Zhang

Zhou

et al. 2019

Fatigue Fract Eng Mat Struct

124

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Uniaxial compression tests combined with nondestructive testing techniques are performed to explore the roles of non‐isometric flaws in crack developments in brittle rocks. The acoustic emission (AE) rate‐process theory is adopted to analyze fracture‐related AE event rate characteristics. The full‐field optical method is applied to detect cracking modes. Experimental results show that AE activity is quite active when the matrix microcracking is dominant, while after each macrocracking event, AE activity becomes inactive because of the stress release. Multiphysical data for each tested flaw configuration faithfully confirm the rupture progressivity. The larger the flaw length ratio, the lower the peak stress (also peak axial strain and elastic modulus), as well as the more progressive the cracking process. Moreover, ultimate failure is triggered by the shear fracturing from the relatively long flaw. The short flaw is conditionally involved in ultimate failure when the stress buildup effect dominates. Finally, the fracture mechanism of brittle rocks with non‐isometric flaws is revealed.

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Section: Experimental Procedures and Data Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Progressive failure of brittle rocks with non‐isometric flaws: Insights from acousto‐optic‐mechanical (AOM) data

Zhang

Zhou

et al. 2019

Fatigue Fract Eng Mat Struct

124

View full text Add to dashboard Cite

show abstract

“…From the viewpoint of laboratory experiments, acoustic emission (AE), photographic monitoring, digital image correlation (DIC), and computed tomography (CT) scanning techniques are adopted to capture the crack evolution process in rock that contains pre-existing flaws under compression or tension. [12][13][14][15] From the view point of numerical simulation, crack initiation and coalescence process of rock is reproduced in RFPA3D, 16 FLAC, 17 AUTODYN, 18 FEMDEM, 19 NOSB-PD, 20 NMM, 21 GPD, 22 and particle flow code (PFC). 23 To simulate the loading-type failure of underground openings, Fakhimi et al 24 tested a sandstone specimen that contains a central hole under biaxial compression.…”

Section: Introductionmentioning

confidence: 99%

Cracking process of a granite specimen that contains multiple pre‐existing holes under uniaxial compression

Huang

Yang

Tian

2019

Fatigue Fract Eng Mat Struct

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The pre‐existence of openings, which play an important role in the mechanical properties and cracking behaviours of rock, is prevalent in rock mass. The interaction among pre‐existing openings (or holes) complicates the instability problems when rock contains multiple holes. Studying the strength failure behaviour of rock that contains multiple pre‐existing holes contributes to the fundamental knowledge of the excavation and stability of underground rock engineering. In this study, first, a series of uniaxial compression tests were performed on granite specimens that contain multiple small holes to investigate the effect of the geometry of pre‐existing holes on the strength and fracture behaviours of rock. The crack initiation, propagation and coalescence process, and acoustic emission (AE) characteristics were investigated using photographic and AE monitoring. Three failure modes were identified, ie, splitting failure, stepped path failure, and planar failure modes. Second, a set of micromechanical parameters in the PFC3D model were calibrated by comparison with the experimental results of an intact granite specimen. The numerically simulated peak strength, peak strain, and failure mode of preholed specimens were consistent with the experimental results. In accordance with the numerical results, the failure modes of the preholed specimens were dependent on the bridge angle and number of holes. Last, the internal fracture characteristics of numerical specimens were revealed by analyzing the horizontal and vertical cross sections at different positions.

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Introduction of a Scaling Factor for Fracture Toughness Measurement of Rocks Using the Semi-circular Bend Test

et al. 2021

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This article discusses the scale dependence of the mode $$\mathrm {I}$$ I fracture toughness of rocks measured via the semi-circular bend (SCB) test. An extensive set of experiments is conducted to scrutinise the fracture toughness variations with size for three distinct rock types with radii ranging from 25 to 300 mm. The lengths of the fracture process zone (FPZ) for different sample sizes are measured using the digital image correlation (DIC) technique. A theoretical model is also established that relates the value of fracture toughness to the sample size. This theorem is based on the strip-yield model to estimate the length of FPZ, and the energy release rate concept to relate the FPZ length to the fracture toughness. This theoretical model does not rely on any experimental-based curve-fitting parameter, but only on the tensile strength of the rock type as well as the fracture toughness at a specific sample size. The size effects predicted by the theoretical model is in a good agreement with the experimental data on both fracture toughness and the FPZ length. Finally, theoretical correction factors are introduced for various geometrical configurations of the SCB specimen, using which a scale-independent mode $$\mathrm {I}$$ I fracture toughness of the rock material can be estimated from the results of experiments performed on small samples.

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Experimental and numerical investigation of cracked chevron notched Brazilian disc specimen for fracture toughness testing of rock

Cited by 65 publications

References 60 publications

Progressive failure of brittle rocks with non‐isometric flaws: Insights from acousto‐optic‐mechanical (AOM) data

Progressive failure of brittle rocks with non‐isometric flaws: Insights from acousto‐optic‐mechanical (AOM) data

Cracking process of a granite specimen that contains multiple pre‐existing holes under uniaxial compression

Introduction of a Scaling Factor for Fracture Toughness Measurement of Rocks Using the Semi-circular Bend Test

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