Unloading Rheological Test and Model Research of Hard Rock under Complex Conditions

Zhang, Longyun; Yang, Shangyang

doi:10.1155/2020/3576181

Cited by 7 publications

(4 citation statements)

References 18 publications

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“…The transition creep method considers the maximum load that the rock can withstand without steady-state creep as the long-term strength of the rock [32]. It assumes that there is a stress threshold inside the rock, and when the applied external load is lower than this stress threshold, the rock is not damaged under long-term loads [33]-that is, the rock will only enter the decay creep phase during loading [34].…”

Section: Transitional Creep Methodsmentioning

confidence: 99%

Study on Creep Characteristics and Long-Term Strength of Mud-Calcareous Conglomerates in the Three Gorges Reservoir Area

et al. 2023

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The study of the time-dependent properties of engineering rock masses is a frontier topic in rock mechanics. In this study, creep tests and stress relaxation tests were conducted on mud-calcareous conglomerates from the Three Gorges Reservoir Area, and the long-term strength values of the conglomerate specimens were determined via different methods based on the test curves. By comparing these mainstream long-term strength determination methods, it was found that each of these methods have their own drawbacks. For example, the transition creep method requires a high accuracy of the test curve and only obtains an approximate strength interval rather than an accurate value. The long-term strength values determined by the isochronous stress–strain curve method are strongly influenced by subjective factors, among other things. Therefore, this paper proposes a new method for determining long-term strength, called the steady-state creep rate method, based on stress intervals. By comparison, the long-term strength values determined via this method are in good agreement with the transition creep method, the volume expansion method, and the stress relaxation method.

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Section: Transitional Creep Methodsmentioning

confidence: 99%

Study on Creep Characteristics and Long-Term Strength of Mud-Calcareous Conglomerates in the Three Gorges Reservoir Area

et al. 2023

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“…With the combination of elements, this model can represent the primary and secondary creep stages, such as the models of Maxwell, Kelvin, Burgers, and Nishihara [ 20 – 24 ]. Fractional order has been introduced into the viscous element to represent the tertiary creep stage [ 25 – 29 ]. A component model is relatively easy to understand, and the components and parameters have physical meaning.…”

Section: Introductionmentioning

confidence: 99%

Unified transient creep constitutive model based on the crack evolution of micritic bioclastic limestone

Li²,

Yao³

et al. 2022

PLoS ONE

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The surrounding rock at the exit of the No. 1 drainage tunnel of the Artashi Water Conservancy Project is micritic bioclastic limestone with 55% bioclastic material. This rock underwent unpredictable large and time-dependent deformation during excavation. To date, the mechanical behaviour of this kind of rock has rarely been studied. In this study, traditional triaxial compression tests and multilevel creep tests were conducted on micritic bioclastic limestone, and the results clarified the instantaneous and time-dependent mechanical properties of the rock. Considering that the essence of rock failure is crack growth, the crack strain evolution properties were revealed in rock triaxial compression tests and multilevel creep tests. Based on triaxial compression tests, the evolution of axial cracks with increasing deviatoric stress ratio Rd (ratio of deviatoric stress to peak deviatoric stress) was observed, and an axial crack closure element and new crack growth element were proposed. To simulate the creep behaviour of a rock specimen, the relationship of the rock creep crack strain rate with Rd was studied. A creep crack element was created, and the creep crack strain evolution equation was obtained, which closely fit the experimental data. Combining the 4 element types (elastic element, crack closure element, crack growth element, and creep crack element), a unified transient creep constitutive model (Mo’s model) was proposed, which represented both the transient and time-dependent mechanical properties of the micritic bioclastic limestone.

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“…The stress relaxation magnitude increases with increased unloading amplitude over a long time [6]. In addition, Zhang and Yang have implemented long-term unloading rheological tests of granite under different confining pressures [7]. Their findings indicate that there are instanta-neous deformation, slow creep deformation, steady-state creep deformation, and acceleration creep deformation in the unloading creep test curve.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Study on Stress Relaxation of Yunnan Sandstone

Zheng

2022

Lithosphere

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This study presents the results from five relaxation tests conducted under uniaxial compression at room temperature. Test specimens were from sandstone formations at a mine, in Yunnan, and exhibited brittle failure. The test apparatus was valid for conducting stress relaxation experiments on sandstones by theoretical model and deformation measurements. Multiple load levels were applied in steps to each specimen, with each displacement level maintained for 12 d or longer. As soon as axial stress was decreased, it stabilized at an almost constant value after 12–24 h. Three distinct relaxation phases were observed to exist at all displacement levels except the specimen 3 in all tests. Based on the LM-NLSF method, model parameters under different strain levels were obtained. Comparison of test curves with theoretical curves showed that the Burgers model, which considers damage, was suitable for describing the stress relaxation properties of sandstones and the obtained parameters had a certain practical value.

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Unloading Rheological Test and Model Research of Hard Rock under Complex Conditions

Cited by 7 publications

References 18 publications

Study on Creep Characteristics and Long-Term Strength of Mud-Calcareous Conglomerates in the Three Gorges Reservoir Area

Study on Creep Characteristics and Long-Term Strength of Mud-Calcareous Conglomerates in the Three Gorges Reservoir Area

Unified transient creep constitutive model based on the crack evolution of micritic bioclastic limestone

An Experimental Study on Stress Relaxation of Yunnan Sandstone

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