Experimental Study on Coal Specimens Subjected to Uniaxial Cyclic Loading and Unloading

Gao, Mingtao; Yan, Hongyu; Duan, Hongtao; Xiong, Shengwu

doi:10.3390/app122211810

Cited by 3 publications

(3 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The mechanical properties of rock (masses) will be different depending on the stress environment. Scholars have conducted indoor mechanical tests on various types of rocks (masses) under complex stress environments and these can be roughly divided into loading mechanical, unloading mechanical [2], cyclic loading and unloading mechanical [3][4][5][6][7], and damage reloading mechanical tests [8][9][10]. Previous studies [11][12][13] conducted indoor loading tests and studied the stress-strain curves, deformation, and failure characteristics of sandstone and conglomerate specimens under various confining pressures.…”

Section: Introductionmentioning

confidence: 99%

Reloading Mechanical Properties and Particle Flow Simulation of Pre-Peak Confining Pressure Unloading Sandstone

Ding²,

Chen

2023

Applied Sciences

View full text Add to dashboard Cite

The excavation-unloading damage effects of western high-geostress slopes on rock were explored by testing the pre-peak confining pressure unloading sandstone reloading mechanical properties. The deformation and failure mechanisms were studied from a mesoscopic perspective using the particle discrete-element method. (1) Approaching the unloading failure, confining pressure increased the specimen bearing capacity attenuation. (2) The confining pressure unloading promoted microdefect propagation and development; the specimens increased rapidly to the damage stress value after reaching the initiation stress value. The penetration fracture zone was more evident and expansive in the model, and the distribution of the dense crack areas was more concentrated in the fracture zone and area. (3) The average interval of the tangential contact force was the largest in the direction of crack expansion and propagation. The strong force chains were shown to primarily bear external loads, whereas the weak force chains played a key auxiliary role in maintaining stability. (4) The number of cracks developing in the confining pressure unloading damage process indicated that the loading process did not cause damage to the specimens. The fracture zones further propagated and formed on the dominant fractures based on the damage caused by the confining pressure unloading disturbance.

show abstract

Section: Introductionmentioning

confidence: 99%

Reloading Mechanical Properties and Particle Flow Simulation of Pre-Peak Confining Pressure Unloading Sandstone

Ding²,

Chen

2023

Applied Sciences

View full text Add to dashboard Cite

show abstract

“…Tang, J. et al [15] found that under cyclic loading and unloading, the AE characteristics of rock fracture show a clear Kaiser effect, and the Felicity effect is significantly observed when the loading force reaches 70% of the peak value. The b-value is commonly used, based on AE, to predict the precursors of rock failure, and a significant increase or decrease in the b-value suggests that the rock may have a large number of cracks or is about to become unstable and fail [16][17][18]. Under low stress conditions, b-value activity is weak and almost imperceptible, while under high stress states, b-value activity is intense.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Energy Evolution and Acoustic Emission Characteristics of Fractured Sandstone under Cyclic Loading and Unloading

Xie,

Sun,

Sheng

2024

Applied Sciences

View full text Add to dashboard Cite

To investigate the dynamic response of fractured rock under cyclic loading and unloading, a WHY-300/10 microcomputer-controlled electro-hydraulic servo universal testing machine was used to conduct uniaxial cyclic loading and unloading tests. Simultaneously, acoustic emission (AE) and a CCD high-speed camera were employed to monitor the fracturing characteristics of sandstone. The mechanical properties, energy evolution, AE characteristics, and deformation of 45° sandstone were analyzed. The results indicate that as the load cycle level increases, both the elastic modulus and deformation modulus exhibit a “parabolic” increase, with a rapid rise initially and a slower rate of increase later. The damping ratio generally shows a decreasing trend but tends to rise near the peak load. The total energy, elastic energy, dissipated energy, damping energy, and damage energy all follow exponential function increases with the load level. The b-value fluctuates significantly during the stable crack propagation phase, unstable crack propagation phase, and peak phase. When the FR (Felicity ratio > 1), the rock is relatively stable; when the FR (Felicity ratio < 1), the rock gradually extends towards an unstable state. The Felicity ratio can be used as a predictive tool for the precursors of rock failure. Shear fractures dominate during the compaction and peak phases, while tensile fractures dominate during the crack propagation phase, ultimately leading to a failure characterized by tensile fracture. High-speed camera observations revealed that deformation first occurs at the tips of the prefabricated cracks and gradually spreads and deflects toward the ends of the sandstone. This study provides theoretical support for exploring the mechanical behavior and mechanisms of fractured rock under cyclic loading and unloading, and it has significant practical implications.

show abstract

“…When a load or force is applied to a soil, its particles reorganize and compress [26,27], which can lead to microfractures or internal displacements [28] in the material that will release energy in the form of acoustic waves [29]. When these emissions are monitored, valuable information can be obtained about the evolution of soil deformation [28,30], changes in mechanical behavior [31,32], the location and propagation of microfractures [33], the presence of weaknesses or potentially unstable areas (of great importance for the safety assessment of structures built on the ground) [20], and, in general, the strength of the soil [29,34] to applied forces. Acoustic characteristics may vary according to the soil properties [33], applied load [13,26], and other factors [31], so specific equipment and knowledge [35], as well as a careful approach, are needed in each particular case.…”

Section: Introductionmentioning

confidence: 99%

Multivariate Statistical and Correlation Analysis between Acoustic and Geotechnical Variables in Soil Compression Tests Monitored by the Acoustic Emission Technique

García-Ros,

Villalva-León,

Castro

et al. 2023

Mathematics

View full text Add to dashboard Cite

In this research, a series of compression tests were carried out, under oedometric conditions, on sand samples prepared with different moisture contents. In these tests, in addition to the usual measurements of the stress and deformation of the sample, a series of acoustic emission sensors were used to monitor the parameters of the acoustic signals coming from inside the sample. This is a rather novel technique with great potential, but sometimes difficult to approach due to the large amount of acoustic emission data generated. In this paper, a correlation and regression analysis has been performed to quantify the correlations between the geotechnical variables and the parameters characterizing the acoustic emissions. The results presented open an interesting horizon of possibilities since, as it has been shown, it is possible to determine the values of the geotechnical properties from the acoustic variables, by means of the regression functions obtained for each type of soil or for each practical case. At the very least, this is a complementary tool in the determination of the mechanical properties of soils subjected to compression, although it could also be useful in those situations in which the monitoring of geotechnical variables describing the tenso-deformational behavior of the soil may be difficult or impossible.

show abstract

Experimental Study on Coal Specimens Subjected to Uniaxial Cyclic Loading and Unloading

Cited by 3 publications

References 17 publications

Reloading Mechanical Properties and Particle Flow Simulation of Pre-Peak Confining Pressure Unloading Sandstone

Reloading Mechanical Properties and Particle Flow Simulation of Pre-Peak Confining Pressure Unloading Sandstone

Experimental Study on Energy Evolution and Acoustic Emission Characteristics of Fractured Sandstone under Cyclic Loading and Unloading

Multivariate Statistical and Correlation Analysis between Acoustic and Geotechnical Variables in Soil Compression Tests Monitored by the Acoustic Emission Technique

Contact Info

Product

Resources

About