Estimating Macrofracture Toughness of Sandstone Based on Nanoindentation

Zhou, Zilong; Lei, Boxiang; Cai, Xun; Rui, Yichao

doi:10.1155/2021/6621643

Cited by 3 publications

(3 citation statements)

References 47 publications

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“…The elastic energy is induced by the pure elastic deformation, while the plastic energy is caused by the pure plastic deformation (pure plastic energy, U pp ) and energy lost due to the microcracks generation (fracture energy, U c ). The fracture toughness can be calculated by the fracture energy ( U c ) according to (Sun et al., 2020; Zhou et al., 2021). More detailed information on the calculation of Young's modulus, hardness, and fracture toughness can be seen in the Supporting Information S1 (Text S3).…”

Section: Methodsmentioning

confidence: 99%

Micromechanical Contrast of Ordos Basin Sandstone‐Mudstone Interbedded Layered Rocks

Yang,

Cong,

Gong

et al. 2023

JGR Solid Earth

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Layered rocks are heterogeneous media composed of multiscale minerals with contrasting geomechanical properties. It remains unclear how the mechanical responses of constituent minerals among different adjacent layers vary in a microscale. Based on the grid nanoindentation tests assisted by high‐resolution scanning electron microscopy and energy‐dispersive spectroscopy techniques, we quantified the mechanical responses of various minerals in an interbedded sandstone‐mudstone core sample and provided visual mineralogies and indentation patterns of different adjacent layers. Results show that the Young's modulus, hardness, and elasticity index of quartz and dolomite decrease, whereas their fracture toughness and plastic work ratio increase from the sandstone layer to the mudstone layer. Quartz displays elastic‐dominated deformations in the sandstone layer whereas transforms into medium‐plastic deformations in the mudstone layer. The mean values of Young's modulus, hardness, and elasticity index of quartz in the sandstone layer are 1.28, 2.00, and 1.56 times higher than that in the mudstone layer, respectively. Dolomite and phyllosilicate minerals show prominently plastic‐dominated deformations in each layer. When an indenter encounters multiple minerals simultaneously, the mechanical responses are determined by the softer phases and irregular indent impressions are generated. Shear and radical cracks are prone to occur in the elastic‐dominated minerals, while chipping damage is induced in the plastic‐dominated minerals. This work provides new insights and fundamental understandings in geomechanical properties contrasts in multilayered rocks, and can facilitate the geomechanical modeling and upscaling schemes in multilayered formations.

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Section: Methodsmentioning

confidence: 99%

Micromechanical Contrast of Ordos Basin Sandstone‐Mudstone Interbedded Layered Rocks

Yang,

Cong,

Gong

et al. 2023

JGR Solid Earth

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“…The surface of a shale sample for nanoindentation testing must be completely flat to obtain reliable results [18,[30][31][32]. In this study, the shale was cut perpendicular to the bedding and then cast into epoxy resin.…”

Section: Sample Preparationmentioning

confidence: 99%

Modeling the Viscoelastic Behavior of Quartz and Clay Minerals in Shale by Nanoindentation Creep Tests

et al. 2022

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The viscoelastic behavior of minerals in shales is important in predicting the macroscale creep behavior of heterogeneous bulk shale. In this study, in situ indentation measurements of two major constitutive minerals (i.e., quartz and clay) in Longmaxi Formation shale from the Sichuan Basin, South China, were conducted using a nanoindentation technique and high-resolution optical microscope. Firstly, quartz and clay minerals were identified under an optical microscope based on their morphology, surface features, reflection characteristics, particle shapes, and indentation responses. Three viscoelastic models (i.e., three-element Voigt, Burger’s, and two-dashpot Kelvin models) were then used to fit the creep data for both minerals. Finally, the effects of peak load on the viscoelastic behavior of quartz and clay minerals were investigated. Our results show that the sizes of the residual imprints on clay minerals were larger than that of quartz for a specific peak load. Moreover, the initial creep rates and depths in clay minerals were higher than those in quartz. However, the creep rates of quartz and clay minerals displayed similar trends, which were independent of peak load. In addition, all three viscoelastic models produced good fits to the experimental data. However, due to the poor fit in the initial holding stage of the three-element Voigt model and instability of the two-dashpot Kelvin model, Burger’s model is best in obtaining the regression parameters. The regression results indicate that the viscoelastic parameters obtained by these models are associated with peak load, and that a relatively small peak load is more reliable for the determination of viscoelastic parameters. Furthermore, the regression values for the viscoelastic parameters of clay minerals were lower than those of quartz and the bulk shale, suggesting the former facilitates the viscoelastic deformation of shale. Our study provides a better understanding of the nanoscale viscoelastic properties of shale, which can be used to predict the time-dependent deformation of shale.

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“…Recently, the holding states of nanoindentation experiments have been widely used to analyze the time-dependent deformations of biomaterials [10], metals and alloys [11,12], ceramics [13,14], polymers and composites [15][16][17][18], types of cement [19,20], and even crystals [21,22]. Besides, the estimation of the macrofracture toughness of minerals and rocks is given in [23], while the analysis of the micromechanical properties of mineral crystal grains is becoming more and more extensive [24][25][26]. All those above mean that the experimental technique was a robust way to conduct creep tests.…”

Section: Introductionmentioning

confidence: 99%

Explanation on the Abnormal Behavior during the Nanoindentation Holding Stages by Amplifying Oscillation

et al. 2022

Advances in Civil Engineering

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Recently, the holding states of nanoindentation experiments have been widely used to analyze the time-dependent deformations of various rocks, and the dynamic mechanical analysis (DMA) method seems to be more applicable than the quasi-static mechanical analysis (QMA) method when the influence of creep deformation on mechanical properties of rocks was analyzed. However, the former method causes an abnormal behavior during the creep holding stages that was not clearly interpreted.2 Consequently, in this study, by amplifying the oscillation of the DMA method, the mechanical mechanism of this phenomenon was explained. Experimental results confirm that the rheological deformation of rocks consists of the creep deformation (depth increasing) and the elastic aftereffect deformation (depth decreasing) during the creep time with small oscillation; once the elastic aftereffect deformation exceeds the creep deformation, the abnormal behavior can be observed. Besides, some other abnormal behaviors might be found for other rock materials when the DMA method with different oscillations is used, which illustrates the complexity and limitation of applying this method. Thus, the QMA method was recommended to investigate the above questions in future studies.

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Estimating Macrofracture Toughness of Sandstone Based on Nanoindentation

Cited by 3 publications

References 47 publications

Micromechanical Contrast of Ordos Basin Sandstone‐Mudstone Interbedded Layered Rocks

Micromechanical Contrast of Ordos Basin Sandstone‐Mudstone Interbedded Layered Rocks

Modeling the Viscoelastic Behavior of Quartz and Clay Minerals in Shale by Nanoindentation Creep Tests

Explanation on the Abnormal Behavior during the Nanoindentation Holding Stages by Amplifying Oscillation

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