Fracture Energy-Based Brittleness Index Development and Brittleness Quantification by Pre-peak Strength Parameters in Rock Uniaxial Compression

Munoz, H.; Taheri, Abbas; Chanda, Emmanuel

doi:10.1007/s00603-016-1071-4

Cited by 147 publications

(40 citation statements)

References 36 publications

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“…Three-dimensional DIC measurements were performed based on random speckle patterns developed on the specimen surface. Generally, speckle patterns were formed using a black and white spray lacquer, which adheres to the specimen surface and deforms in-line with the specimen [5]. For accurate measurements, the speckle patterns must be irregular, randomly distributed, and possess high contrast.…”

Section: Specimens and Test Methodsmentioning

confidence: 99%

“…For example, the crack initiation stress can be used to estimate the lower limit value of spalling rock mass strength [3,4]. Some brittleness indices have strong correlations with the crack damage stress and peak stress [5]. Moreover, the lower and upper limits of long-term strength can be obtained from the crack initiation stress and crack damage stress [6].…”

Section: Introductionmentioning

confidence: 99%

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Study on the Progressive Failure Characteristics of Coal in Uniaxial and Triaxial Compression Conditions Using 3D-Digital Image Correlation

Tang

Okubo

et al. 2018

Energies

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Abstract:To investigate the progressive failure process of coal, a series of uniaxial and triaxial compression tests were conducted and a novel 3D digital image correlation instrument with six cameras combined with a special transparent pressure cell was used for the strain measurement. The stress thresholds of coal were obtained in uniaxial and triaxial compression. The energy evolution during the compression was discussed, coupled with the crack volumetric strain. The field strain of the whole specimen surface and crack propagation at different stress levels were described to study the progressive failure mechanism of coal. The average stress level of crack initiation and crack damage of coal in uniaxial compression are 43.75% and 63.03%, while that in the triaxial compression are 74.53% and 89.84%, respectively. The dissipation energy evolution corresponds to the crack volumetric strain, while the elastic energy release leads to flake ejection and coal failure. The crack evolution and localization of coal indicated the progressive failure process that the coal sample undergoes in tension failure in uniaxial compression and in tension-shear failure in triaxial compression. The findings of this study can serve as a reference to understand the failure process of coal and improve the stability and safety of mining engineering.

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Section: Specimens and Test Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Study on the Progressive Failure Characteristics of Coal in Uniaxial and Triaxial Compression Conditions Using 3D-Digital Image Correlation

Tang

Okubo

et al. 2018

Energies

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“…Rock mechanics studies have been extensively conducted in China and abroad, which cover a broad range, from uniaxial to triaxial compression, simple to multiple conditions, and single to complex paths [1][2][3][4][5][6]. In triaxial tests, the initial stress level mainly includes the initial confining pressure and the initial axial pressure.…”

Section: Introductionmentioning

confidence: 99%

Elastic-Plastic Threshold and Rational Unloading Level of Rocks

Guo

2019

Applied Sciences

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During loading and unloading test, various rocks manifest different stress values of elastic-plastic transformation. This study proposes to include axial pressure increment ratio in the conventional triaxial compression test to evaluate different variables (nominal elastic modulus, nominal Poisson's ratio, strain, and energy). The relationships among various factors including variables, the stress level of initial confining stress and axial pressures, were analyzed by analyzing the stress-strain plot record obtained from testing various rocks. The extreme value point of the deformation parameter, also known as the elastic-plastic threshold, was analyzed. In addition, the elastic-plastic thresholds were later used as unloading points during the unloading tests. Under the same confining condition, different rocks demonstrated different unloading levels. Furthermore, a linear correlation was observed between unloading levels and changing confining pressures, and the gradient is mainly related to the types of rocks. During the unloading tests of rocks, the rational unloading level is recommended to be no higher than the stress level at the elastic-plastic threshold under the corresponding confining pressure. Appl. Sci. 2019, 9, 3164 2 of 15 and the unloading level has no significant effect on the energy evolution process. Zhang [11] and Zhu [12] considered that the unloading stress level mitigated possible damage within rocks during the unloading damage stage. Regarding the initial axial pressure of unloading, Liu et al. [13] selected 50% of the conventional triaxial compressive strength and the corresponding confining pressure, whereas other researchers often adopted 60% and 80% [14][15][16], 70% [17][18][19][20], 80-90% [21], and 15-90% [22]. Most researchers selected 80% of the peak strength as the loaded axial pressure in unloading tests [23][24][25][26]. Details of studies discussed above can be viewed in Table 1. However, mentioned studies failed to consider the effects of the initial axial pressure during exploring the effects of unloading on rock failures.

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“…Understanding the energy evolution in rock is critical for rock engineering design and assessment and has been one of the key problems facing modern researchers [1][2][3][4][5]. The energy evolution in rock is determined by-and is therefore an indicator of-the deformation and failure of the rock [6][7][8][9]. In recent years, many scholars have researched the energy accumulation, dissipation, and release in the rock by way of theoretical analysis and laboratory tests.…”

Section: Introductionmentioning

confidence: 99%

Numerical Research on Energy Evolution in Granite under Different Confining Pressures Using Otsu’s Digital Image Processing and PFC2D

et al. 2019

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Research on energy accumulation and releasing in the rock plays a key role on revealing its failure mechanism. This paper establishes a microscopic structure model of granite using Otsu digital image processing (DIP) technology and particle flow code software (PFC2D). A series of numerical compression tests under different confining pressures were conducted to investigate the macro and micro characteristics of energy evolution in granite. The results showed that the energy evolution of granite is divided into three stages: stable accumulation, slow dissipation, and rapid release. With increasing confining pressure, the strain energy accumulation ratio decreased exponentially and the peak value of strain energy increased linearly. It was found that the energy accumulation speed in the pre-peak stage increased as a linear function, while the energy release speed in the post-peak stage decreased as an exponential function. In addition, the feldspar is the main microstructure which played a major part in accumulating energy in granite. However, the unit mineral energy of mica particles was bigger than that of feldspar and quartz. When subjected to increasing confining pressure, the feldspar’s total energy growth rate was fastest. Meanwhile, the mica’s unit energy growth rate was fastest.

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Fracture Energy-Based Brittleness Index Development and Brittleness Quantification by Pre-peak Strength Parameters in Rock Uniaxial Compression

Cited by 147 publications

References 36 publications

Study on the Progressive Failure Characteristics of Coal in Uniaxial and Triaxial Compression Conditions Using 3D-Digital Image Correlation

Study on the Progressive Failure Characteristics of Coal in Uniaxial and Triaxial Compression Conditions Using 3D-Digital Image Correlation

Elastic-Plastic Threshold and Rational Unloading Level of Rocks

Numerical Research on Energy Evolution in Granite under Different Confining Pressures Using Otsu’s Digital Image Processing and PFC2D

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