Experimental investigation of progressive cracking processes in granite under uniaxial loading using digital imaging and AE techniques

Zhou, Xiaoping; Zhang, Jian‐Zhi; Qi, Qian; Niu, Yong

doi:10.1016/j.jsg.2019.06.003

Cited by 210 publications

(70 citation statements)

References 57 publications

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“…The opening or slipping of these fractures in the plastic zone will dissipate a considerable amount of strain energy, 44 which is consistent with the conclusions in Sections 2.3 and 3.3 that the strain energy is dissipated in the plastic zone. Strain softening is closely associated with the microcrack growth in the surrounding rock, as well as the upscaling fracturing 45‐48 . These fractures are not uniformly distributed in the plastic zone, indicating that the strain softening of the surrounding rock is discontinuous, verifying the conclusion in Section 3.3.…”

Section: Verification Via Field Monitoring Datasupporting

confidence: 65%

Transfer and dissipation of strain energy in surrounding rock of deep roadway considering strain softening and dilatancy

Liu

Lü

et al. 2020

Energy Science & Engineering

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In this study, the transfer and dissipation of strain energy in the surrounding rock of a deep roadway were analyzed, considering the objective strain softening and dilatancy behaviors. The strain energy increment was decomposed, and its variation was analyzed based on the incremental plastic flow theory; then, a numerical simulation was conducted for verification and further analysis. The results were verified by the field monitoring data of a coal mine gateway. The results show that in the elastic stage, the volumetric elastic strain energy density Uev decreases, while the shear elastic strain energy density Ues increases. In the plastic stage, both Uev and Ues decrease. The volumetric plastic strain energy density Upv is negative, and its absolute value increases, leading to strain energy accumulation. In contrast, the shear plastic strain energy density Ups is positive and increases, leading to strain energy dissipation. Considering strain softening, the elastic strain energy decreases, the plastic strain energy increases, and the region of strain energy dissipation expands. Considering dilatancy, the plastic strain energy varies more significantly, and the effect of strain softening is amplified. The strain energy is transferred from the deep part to the shallow part of the elastic zone and then to the plastic zone. The preexisting and input strain energies in the plastic zone are transformed into considerable amounts of plastic strain energy and then dissipated. Thereafter, a significant plastic strain appears, leading to the large deformation of the surrounding rock.

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Section: Verification Via Field Monitoring Datasupporting

confidence: 65%

Transfer and dissipation of strain energy in surrounding rock of deep roadway considering strain softening and dilatancy

Liu

Lü

et al. 2020

Energy Science & Engineering

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“…Pre‐existing flaw, an analogy to in situ discontinuities such as joints, faults, and fissures in natural rocks, is capable of inducing mechanically the formation of catastrophic rupture (Amitrano et al, 2005; Hall et al, 2006; Raynaud & Vasseur, 2014; Vasseur et al, 2015; Zhang et al, 2019; Zhou et al, 2018, 2019; Zhou et al, 2020). In the present study, a “through‐thickness” pre‐existing flaw of 10 mm in length and 1 mm in width, with a changing flaw inclination angle (denoted by α in Figure 1a), is designed at the midlength of the specimen.…”

Section: Samples Experimental Method and Data Processingmentioning

confidence: 99%

Forecasting Catastrophic Rupture in Brittle Rocks Using Precursory AE Time Series

Zhang

Zhou

2020

JGR Solid Earth

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An evidently precursory acoustic emission (AE) time series, characterized by a time‐reversed Omori law, is registered prior to the unconfined catastrophic rupture of brittle sandstone. This provides insights into the physical process controlling catastrophic rupture and underlies the failure forecast. The onset of acceleration of damage is first identified based on the acousto‐optical characteristics. The precursory time series of rise time (RT) rate is used to forecast pseudo‐prospectively the catastrophic rupture in the framework of the time‐reversed Omori law. Investigations on multiple unconfirmed failure cases on the laboratory scale show that forecasts become more precise and less biased as the precursory AE time series proceeds toward rupture. In contrast to retrospective forecast, pseudo‐prospective forecast obtains a higher quality. Moreover, the use of amplitude as a precursor benefits the increase of warning time, and the flaw‐to‐flaw interaction introduces a strong disturbance on the forecast.

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“…ese include (1) crack closure stress σ cc , (2) microcrack nucleation stress σ cn , (3) crack initiation stress σ ci , (4) crack damage stress σ cd , and (5) peak stress σ c . As shown in Figure 1, the stress-strain curve is usually divided into five stages (I-V), where σ ci and σ cd are the focus of rock mechanical studies [26][27][28][29]. e determination of σ cd has been widely reported, namely, the axial stress corresponding to the volume strain reversal point.…”

Section: Crack Initiation Mechanism Of Rock Under Uniaxial Compressionmentioning

confidence: 99%

Relationship between Brittleness Index and Crack Initiation Stress Ratio for Different Rock Types

Jiang

Wang

Han

et al. 2020

Advances in Civil Engineering

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Brittleness and crack initiation stress (σci) are important rock mechanical properties and intrinsically related to rock deformation and failure. We establish the relationship between σci and uniaxial tensile strength (σt) based on the Griffith stress criterion of brittle failure and introduce brittleness indexes B1–B4 based on the ratio of uniaxial compressive strength (σc) to σt. The crack initiation stress ratio (K) is defined as the ratio of σci to crack damage stress. The relationship between brittleness index and K is obtained from laboratory mechanics tests including uniaxial compression and Brazilian splitting tests. The results show that B1 and B2 have an inversely proportional and variant inversely proportional relationship with K, respectively, whereas no apparent relationship is observed between B3 and B4 and K. The fitting of experimental data from igneous, metamorphic, and sedimentary rocks shows that B1 and B2 have a power and linear relationship with K, respectively, whereas no functional relationship is observed between B3 and B4 and K. We collected 70 different types of uniaxial compression test data for igneous, metamorphic, and sedimentary rocks and obtained laws that are consistent within each rock type. The experimental data are used to verify K estimations using a specified constant α based on the experimental data. According to results of the limestone tests, α = 3 for σc < 60 MPa (high porosity), α = 5 for 60 MPa ≤ σc ≤ 90 MPa (moderate porosity), and α = 8 for σc > 90 MPa (low porosity) as well as for igneous and metamorphic rocks. Estimates of K for 127 different rock types using the newly defined brittleness index are in good agreement with the experimental results. This study provides an important new brittleness index calculation method and a simple and reliable method for estimating K.

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Experimental investigation of progressive cracking processes in granite under uniaxial loading using digital imaging and AE techniques

Cited by 210 publications

References 57 publications

Transfer and dissipation of strain energy in surrounding rock of deep roadway considering strain softening and dilatancy

Transfer and dissipation of strain energy in surrounding rock of deep roadway considering strain softening and dilatancy

Forecasting Catastrophic Rupture in Brittle Rocks Using Precursory AE Time Series

Relationship between Brittleness Index and Crack Initiation Stress Ratio for Different Rock Types

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