Influence of Loading Rate on the Energy Evolution Characteristics of Rocks under Cyclic Loading and Unloading

Li, Jielin; Liu, Hong; Zhou, Keping; Xia, Caichu; Zhu, Longyin

doi:10.3390/en13154003

Cited by 16 publications

(5 citation statements)

References 14 publications

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“…The elastic strain energy is stored in the rock during loading, which is gradually released during unloading and is the major energy cause of rock deformation and failure. Then, the energy is dissipated due to plastic strain and microdamage of the rock, which is irrecoverable with the unloading of the stress [31]. When the elastic strain energy reaches the rock energy storage limit, the rock enters the failure stage.…”

Section: Establishment Of the Brittleness Indexmentioning

confidence: 99%

Rock Brittleness Evaluation Index Based on Ultimate Elastic Strain Energy

Zhang

Shaikh

et al. 2022

Processes

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Brittleness is an essential parameter to determine the deformation and failure behavior of rocks, and it is useful to quantify the brittleness of rocks in numerus engineering practices. A novel energy-based brittleness evaluation index is proposed in this study, which redefines the dissipated proportion of ultimate elastic strain energy relative to post-peak failure energy and residual elastic strain energy. A series of conventional triaxial compression (CTC) tests were performed on shale rock to verify the reliability and accuracy of the brittleness index. The results show that the proposed index can precisely reflect the deformation and failure characteristic of rocks under different confining pressures. Based on the testing data from six types of rocks in previous studies, the universality of the novel index was verified. According to comparison with existing brittleness indices, the new brittleness index can more precisely characterize the brittleness of rock.

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Section: Establishment Of the Brittleness Indexmentioning

confidence: 99%

Rock Brittleness Evaluation Index Based on Ultimate Elastic Strain Energy

Zhang

Shaikh

et al. 2022

Processes

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“…e average porosity of the rock samples measured via nuclear magnetic resonance (NMR) was 0.53%. Tables 1 and 2 are reproduced from the work of Li et al [10] (under the Creative Commons Attribution License/ public domain).…”

Section: Rock Samplesmentioning

confidence: 99%

Mechanical Characteristics and Mesostructural Damage of Saturated Limestone under Different Load and Unload Paths

Liu

Zhou

et al. 2021

Advances in Civil Engineering

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To study the evolutionary characteristics of mesostructural damage to saturated limestone under different loading and unloading paths, three types of loading and unloading tests involving three different loading rates and initial peak stresses were performed. Nuclear magnetic resonance technology and scanning electron microscopy were used to investigate the evolutionary characteristics of pore water during the loading and unloading of the limestone. The results indicated that, with an increase in the initial peak stress, the rock viscoplasticity gradually decreased, and the variation of pore radius and the reduction of bound water decreased. With an increasing loading rate, the mesostructure evolution law under disturbance-increasing amplitude (DIA) cycling was opposite to those under increasing amplitude (IA) and repeated-increasing amplitude (RIA) cycling. With the increasing loading stress level, the porosity decreased and then increased. Under increasing amplitude cycling, a larger initial porosity resulted in higher pore compaction and expansion limits. Reducing the initial peak stress inhibited the pore expansion, whereas it had the opposite effect under RIA and DIA cycling. During loading and unloading, bound water exists in pores of organic matter and mesopores, and free water exists in macropores of intergranular and transgranular fractures. These changes indicate certain laws under different loading and unloading paths. The results of this study indicate that the mesostructure characteristics of rock depend on the loading and unloading paths.

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“…During the pre-peak failure stage, the dissipated energy density of the rock gradually increased. When the load reached peak stress, the dissipated energy significantly extended, the elastic energy stored in the specimen was gradually released in the form of kinetic energy and fracture energy, and the specimen began to deform and eventually destroyed (Li et al 2020;Xiao et al 2019; energy density (U d ) is illustrated in Fig. 8(b).…”

Section: Energy Composition Of the Rockmentioning

confidence: 99%

Deterioration Characteristics and Energy Mechanism of Red-Bed Rocks Subjected to Drying-Wetting Cycles

Huang

Zha

Kang

et al. 2021

Preprint

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The red-bed rocks were chosen and studied by using uniaxial compressive experiment and scanning electron microscopy to investigate the effect of drying-wetting (D-W) cycles on the mechanical properties and microstructural characteristics of red-bed rock. Additionally, the energy mechanism of specimens subjected to drying-wetting cycles was also explained. Experimental results showed that, the stress-strain could be divided into four characteristic stages in the compression failure process. After subjecting to cycles of D-W, the stress-strain curve gradually changed from softening to hardening. At the same time, uniaxial compression strength (UCS) and elastic modulus dropped obviously, while Poisson’s ratio gradually raised. Microstructural analysis results indicated that the microstructure of the specimen surface was no longer dense and uniform, and the porosity of tested specimens significantly increased with D-W cycles increasing. As the porosity grew, UCS and elastic modulus gradually declined. According to the first law of thermodynamics, the process of rock failure was an event of energy transfer and conversion. As the number of D-W cycles increased, the energy density of specimens all present linear fell. From the perspective of the theory of energy dissipation, the dissipated energy was essential for rock failure, and closely related to the strength of the specimen. With D-W cycles increasing, the specimens were more prone to failure, and the dissipated energy required for failure decreased gradually.

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Influence of Loading Rate on the Energy Evolution Characteristics of Rocks under Cyclic Loading and Unloading

Cited by 16 publications

References 14 publications

Rock Brittleness Evaluation Index Based on Ultimate Elastic Strain Energy

Rock Brittleness Evaluation Index Based on Ultimate Elastic Strain Energy

Mechanical Characteristics and Mesostructural Damage of Saturated Limestone under Different Load and Unload Paths

Deterioration Characteristics and Energy Mechanism of Red-Bed Rocks Subjected to Drying-Wetting Cycles

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