Mechanical Behavior Evolution and Damage Characterization of Coal under Different Cyclic Engineering Loading

The cyclic loading causes the strength change of porous rocks, which can be frequently encountered in underground coal mining. In order to quantify the cumulative damage of porous coal, multilevel uniaxial cyclic compressive tests were carried out considering different loading frequencies. The resul...

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Bibliographic Details
Published in:Geofluids 2020, Vol.2020 (2020), p.1-19
Main Authors: Wang, Huajun, Li, Jian
Format: Article
Language:English
Subjects:
Amplitude
Amplitudes
Bearing capacity
Behavior evolution
Coal
Coal industry
Coal mines
Coal mining
Compressibility
Cumulative damage
Cyclic loading
Cyclic loads
Damage assessment
Deformation
Deformation mechanisms
Dilatancy
Laboratories
Mechanical properties
Mineral industry
Mining industry
Modulus of elasticity
Poisson's ratio
Rocks
Stone
Stress
Underground mining
Unloading
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Summary:The cyclic loading causes the strength change of porous rocks, which can be frequently encountered in underground coal mining. In order to quantify the cumulative damage of porous coal, multilevel uniaxial cyclic compressive tests were carried out considering different loading frequencies. The results show that under cyclic loading, Young’s modulus of coal shows a first drastic increase and then decrease trend in terms of the number of loading-unloading cycles, while the Poisson’s ratio gradually increased at lower peak stress amplitudes and then increased sharply with peak cyclic stress amplitude until losing load bearing capacity, following a stepwise rising trend. At a higher loading frequency, volumetric compressibility-dilatancy transition is shifted to an earlier time. The loading/unloading response ratio (LURR) was used to evaluate the damage of coal under cyclic loading. It is found that LURR is an effective parameter to evaluate the damage of coaly rock under cyclic loading and is also useful in distinguishing different deformation mechanism at different loading stages. The results also show that the damage of coal can initiate at the early stage of cyclic loading at a low loading frequency; however, the increase in frequency of cyclic loading can delay the damage time, requiring a relatively higher level of peak cyclic stress amplitude.
ISSN:1468-8115
1468-8123
DOI:10.1155/2020/8812188