Numerical analysis of the flattened Brazilian test: Failure process, recommended geometric parameters and loading conditions

Wu, Shunchuan; Ma, Jun; Cheng, Yao; Min, Xu; Huang, Xiaoqing

doi:10.1016/j.engfracmech.2018.09.024

Cited by 37 publications

(17 citation statements)

References 28 publications

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“…According to Shi et al [29], in the axial compression test of the particle flow test specimens, as the particle size decreases, the uniaxial compressive strength of the specimen tends to be stable and no longer changes with the change of particle size. It is recommended that the ratio of the shortest side of the model to the average ball radius of the model should be greater than 40, which is much larger than the value recommended by Wu et al [21]. Combined with this test, the average ball radius was less than 50mm/40 = 1.25mm.…”

Section: Selection Of Bonded Particle Model In Particle Flow Code 2dmentioning

confidence: 81%

“…Chen [20] revealed a linear correlation between the tensile strength of rock and the contact normal bond strength by conducting uniaxial tensile numerical experiments of 32 PFC models, but they did not discuss the influence of the ball radius ratio on the simulation results. Wu et al [21] discussed the influence of the geometric parameters on the Brazilian tensile strength using a 3D flat-joint model of PFC3D. Results show that only when the diameter of the Brazilian disc is at least 20 times the ball radius can the dispersion of the results be eliminated, but the effects of the contact normal bond strength on the Brazilian tensile strength were ignored.…”

Section: State Of the Artmentioning

confidence: 99%

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Effects of Contact Normal Bond Strength on Brazilian Tensile Strength by Particle Flow Code

Huang¹,

Fu²,

Miao³

et al. 2020

JESTR

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The Contact Bond Model (CBM) of Particle Flow Code (PFC) can effectively simulate the mechanical behaviours of rocks. The physical and mechanical parameters of CBM directly influence the results of the numerical simulation of rocks. To reveal the influence mechanism of the contact normal bond strength of the CBM on Brazilian tensile strength, this study proposes a numerical test model and calculation method for the Brazilian tensile strength. First, the theoretical relationship between the Brazilian tensile strength and the contact normal bond strength of the CBM was derived. Second, 70 groups (350) of PFC Brazilian disk numerical tests were designed, and a numerical model of the Brazilian tensile strength was established. Third, the effects of the contact normal bond strength on the Brazilian tensile strength under various ball radii and ball radius ratios were analyzed according to the PFC numerical simulation results, and the correctness of the theoretical relation was verified. Results demonstrate that the Brazilian tensile strength is significantly and linearly related to the contact normal bond strength and can be expressed as the product of the contact normal bond strength and the scale coefficient. The scale coefficient is affected by the geometric parameters of balls. The scale coefficient generally increases with the minimum particle size, whereas the change in the coefficient becomes irregular. Results reveal the physical significance of the PFC normal bond strength to a certain extent. The proposed method can determine the contact normal bond strength.

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Section: Selection Of Bonded Particle Model In Particle Flow Code 2dmentioning

confidence: 81%

Section: State Of the Artmentioning

confidence: 99%

Effects of Contact Normal Bond Strength on Brazilian Tensile Strength by Particle Flow Code

Huang¹,

Fu²,

Miao³

et al. 2020

JESTR

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“…The flat-joint model (FJM) and the smooth-joint model (SJM) are used to simulate shale matrix and layer planes, respectively. The details of these two models are exhibited by Wang et al (2014) and Wu et al (2018).…”

Section: Numerical Model Establishment and Validationmentioning

confidence: 99%

Mutual interference of layer plane and natural fracture in the failure behavior of shale and the mechanism investigation

et al. 2020

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Shale contains a certain amount of natural fractures, which affects the mechanical properties of shale. In this paper, a bonded-particle model in particle flow code (PFC) is established to simulate the failure process of layered shale under Brazilian tests, under the complex relationship between layer plane and natural fracture. First, a shale model without natural fractures is verified against the experimental results. Then, a natural fracture is embedded in the shale model, where the outcomes indicate that the layer plane angle (marked as α) and the angle (marked as β) of embedded fracture prominently interfere the failure strength anisotropy and fracture pattern. Finally, sensitivity evaluations suggest that variable tensile/cohesion strength has a changeable influence on failure mechanism of shale, even for same α or/and β. To serve this work, the stimulated fractures are categorized into two patterns based on whether they relate to natural fracture or not. Meanwhile, four damage modes and the number of microcracks during the loading process are recognized quantitatively to study the mechanism of shale failure behavior. Considering the failure mechanism determines the outcome of hydraulic fracturing in shale, this work is supposed to provide a significant implication in theory for the engineering operation.

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“…With the rapid development of computer technology and advanced numerical techniques, computational simulations help us overcome this limitation and determine the characterization of crack initiation and growth in more detail 21‐27 . In recent years, the DEM has received considerable attention for its use in modeling the dynamic process of rock failure owing to its three advantages 28‐31 . Firstly, considering its micromechanical foundation, the DEM is a useful simulation tool for understanding the dynamic mechanism of rock materials at a microscale directly.…”

Section: Introductionmentioning

confidence: 99%

“…[21][22][23][24][25][26][27] In recent years, the DEM has received considerable attention for its use in modeling the dynamic process of rock failure owing to its three advantages. [28][29][30][31] Firstly, considering its micromechanical foundation, the DEM is a useful simulation tool for understanding the dynamic mechanism of rock materials at a microscale directly. Secondly, real-time contact searching makes the DEM convenient for observing the dynamic process.…”

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confidence: 99%

Discrete element simulation for investigating fragmentation mechanism of hard rock under ultrasonic vibration loading

Tang

Zhao

Zhou

et al. 2020

Energy Science & Engineering

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With the gradual depletion of shallow resources, the energy exploration depth has been increasing and condition becomes complex. 1 Consequently, the explorations face increasingly harder rocks with higher strengths. Breaking hard rock rapidly in petroleum and mineral exploration is a popular and significant topic. 2-6 However, the current technologies cannot meet the demands of quick drilling. It is necessary to develop a more efficient technology for hard rock exploration. To achieve this goal, the assisted ultrasonic vibration technique (ultra-high-frequency cyclic loading), combined with the traditional drilling method, was first introduced by researchers at Aberdeen University. 7 To implement this technology more effectively, studies were conducted on rock-breaking characteristics under ultrasonic vibrations and optimization of the vibration parameters. The studies conducted by Wiercigroch et al 8 showed that the high-frequency axial vibration significantly enhanced the breaking rates compared to the traditional method. Subsequently, uniaxial compressive strength experiments were conducted on fine granite by Yin et al 9 to demonstrate that there exists a static force threshold for this technology. They found that the optimal value range of static loading was 200-300 N. An

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Numerical analysis of the flattened Brazilian test: Failure process, recommended geometric parameters and loading conditions

Cited by 37 publications

References 28 publications

Effects of Contact Normal Bond Strength on Brazilian Tensile Strength by Particle Flow Code

Effects of Contact Normal Bond Strength on Brazilian Tensile Strength by Particle Flow Code

Mutual interference of layer plane and natural fracture in the failure behavior of shale and the mechanism investigation

Discrete element simulation for investigating fragmentation mechanism of hard rock under ultrasonic vibration loading

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