Strength properties and evolution laws of cracked sandstone samples in re-loading tests

Zong, Yijiang; Han, Lijun; Meng, Qinbin; Wang, Yingchao

doi:10.1016/j.ijmst.2019.03.004

Cited by 24 publications

(11 citation statements)

References 3 publications

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“…The axial stress and confining pressure were gradually applied to fractured specimens at a constant rate of 0.05 MPa/s until the desired confining pressure was reached to ensure that the specimens were under uniform hydrostatic stress. According to the test methods suggested by the International Society for Rock Mechanics (ISRM) [30], the axial stress was loaded on fractured specimens at a constant axial displacement rate of 0.002 mm/s until failure occurred [28,29].…”

Section: Methodsmentioning

confidence: 99%

“…To quantify the damage (D) of fractured specimens, we defined the volumetric dilatation strain ratio between the points in the complete stress-strain curves and the starting points in the residual stage of the specimens under a confining pressure of 30 MPa to calculate D, which can be expressed by the following equation [28,29]:…”

Section: Fractured Specimen Preparationmentioning

confidence: 99%

“…where ε v , ε vd , and ε vr are the volumetric strain, the maximum compressive volumetric strain, and the volumetric strain of the starting points of the residual stage, respectively; ε 1 is the axial strain; ε 1d is the axial strain of the corresponding point for the maximum compressive volumetric strain; and K is a correction factor, which can be calculated by Equation (2) [28,29]:…”

Section: Fractured Specimen Preparationmentioning

confidence: 99%

“…where σ r and σ p are the residual strength and the peak strength of the specimen under a confining pressure of 30 MPa, respectively [28,29]. By substituting the mechanical parameters of the specimens listed in Table 1 into Equations (1) and (2), the damage of fractured specimens can be determined.…”

Section: Fractured Specimen Preparationmentioning

confidence: 99%

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Experimental Investigation on the Post-Peak Short-Term and Creep Behavior of Fractured Sandstone

et al. 2020

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Short-term and creep tests of fractured sandstone with different degrees of damage prepared using pre-peak and post-peak unloading tests on intact sandstone were carried out using a servo-controlled rock mechanics system. Based on our experimental results, the influence of confining pressure and damage on short-term mechanical behavior of fractured sandstone with different degrees of damage was first analyzed. The results show that the peak strength, residual strength, elastic modulus, and secant modulus of fractured sandstone increase linearly with increasing confining pressure, but decrease with increasing damage. The short-term failure modes depend on the damage and change from typical shear failure modes to multiple shear failure modes with increasing damage. Then, the influence of the differential stress, confining pressure, and the degree of damage on the creep mechanical behavior of fractured specimens was further investigated. The axial instantaneous strain and creep strain increase linearly with increasing differential stress, and the specimens exhibit significant time-dependent behavior under high stress. The steady creep rate increases with increasing stress, but it decreases with increasing confining pressure and damage. However, the long-term strength and creep failure strength of fractured specimens increase linearly with increasing confining pressure, but they decrease linearly with increasing damage. The creep failure modes of fractured specimens are also the main shear failure modes, which are similar to the short-term failure modes.

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Section: Methodsmentioning

confidence: 99%

Section: Fractured Specimen Preparationmentioning

confidence: 99%

Section: Fractured Specimen Preparationmentioning

confidence: 99%

Section: Fractured Specimen Preparationmentioning

confidence: 99%

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Experimental Investigation on the Post-Peak Short-Term and Creep Behavior of Fractured Sandstone

et al. 2020

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“…The damaged area and damage volume of the joint surface can only reflect the damage ratio at the end of the shear test, and it is difficult to reflect the damage evolution process during the shearing process [29,30]. Acoustic emission technology is widely used to study the damage of joint specimen during shear [31].…”

Section: Introductionmentioning

confidence: 99%

Exploring the Effect of Asperity Order on Mechanical Character of Joint Specimen from the Perspective of Damage

Yuan

Luo

2021

Geofluids

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The joint morphology is multiscale. The effect of each asperity order on the mechanical properties of joints is different. The shear mechanical properties of joint specimens are related to its surface damage characteristics. At present, there are still few studies on the effect of roughness on the shearing mechanical properties of joint from the perspective of damage of each asperity order. In this paper, the standard roughness profile was chosen as initial morphology. The standard roughness profile was decomposed into waviness and unevenness by the method combine the ensemble empirical mode decomposition (EEMD) and the cut-off criterion. Then, the joint specimen which contains waviness and unevenness and the specimen which only contains waviness were prepared by the 3D engraving technology. The 40 sets of joint specimens with different asperity order were subjected to direct shear tests under different normal stresses. Based on the 3D scanning technology and ICP iterative method, the damaged area and the damage volume were calculated. Based on the damage volume data and the acoustic emission (AE) data, the effect of asperity order to the joint mechanical behaviour was studied. The results indicate that (1) under low normal stress, the unevenness plays a control role in the failure mode of the joint specimen. Under low normal stress, the joint surface containing only waviness exhibits slip failure, and the joint surface with unevenness exhibits shear failure. With the increase of the normal stress, the failure mode of the specimen containing only waviness changes from slip failure to shear failure; (2) the unevenness controls the damage degree of the joint specimen. The damaged area, damage volume, AE energy rate, and accumulative AE energy of the joint specimen with unevenness are larger than those of the specimen with only waviness, and this difference increases with the normal stress increase; (3) the difference between the joint specimen with unevenness and specimen with only waviness mainly exists in the prepeak nonlinear stage and the postpeak softening stage. The characteristic parameters of acoustic emission generated in the postpeak softening stage of the joint specimen with unevenness are greater than those of the specimen with only waviness. This phenomenon can be used to explain the stress drop difference at the postpeak softening stage; (4) the AE b value can be used to evaluate the damage of joint specimens. Analysing the damage difference of each asperity order under different normal stresses is of great significance to the analysis of the influence of the morphology of the joint surface on the mechanical properties of the joint.

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Mechanical Properties and Energy Damage Evolution Characteristics of Coal Under Cyclic Loading and Unloading

et al. 2022

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Strength properties and evolution laws of cracked sandstone samples in re-loading tests

Cited by 24 publications

References 3 publications

Experimental Investigation on the Post-Peak Short-Term and Creep Behavior of Fractured Sandstone

Experimental Investigation on the Post-Peak Short-Term and Creep Behavior of Fractured Sandstone

Exploring the Effect of Asperity Order on Mechanical Character of Joint Specimen from the Perspective of Damage

Mechanical Properties and Energy Damage Evolution Characteristics of Coal Under Cyclic Loading and Unloading

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