Abstract
In order to study the acoustic emission characteristics and Felicity effect in the process of coal fatigue failure and reveal the internal relationship between the fatigue damage evolution law and the acoustic emission activity, with the help of MTS815.02 electrohydraulic servo rock mechanics test system and PCI-2 acoustic emission detection and analysis system, a triaxial cycling loading acoustic emission test was carried out on the coal samples. The results show that the higher the upper limit stress is, the more obvious the degree of fatigue damage will be caused by coal samples. At the same time, the more active acoustic emission signal will appear. The coal samples under linear loading are on the initial damage state, and slight fatigue, moderate fatigue, deep fatigue, and ultimate fatigue failure under cyclic loading. The acoustic emission shows the “L-” type development evolution law in any previous stress level range, while at the last stress level, it shows the obvious “U-” type development evolution law. The higher the frequency of the cyclic loading is, the higher the rate of initiation and expansion of the microcrack will be, while the more obvious acoustic emission phenomenon will appear. Furthermore, the ringing counting rate is basically the same as that of the energy counting rate. Under triaxial cyclic loading, a shear failure mode that extends along different directions of fracture surface will be presented. The acoustic emission in the range of different stress levels shows a different degree of Felicity effect. In contrast, it is more reasonable to use the principal stress difference as a parameter to study the Felicity effect of coal under cyclic loading.
Highlights
Damage failure mechanisms and mechanical properties of rocks and coal under monotonic loading have been extensively studied [1,2,3,4,5,6]
Zou et al [21] systematically studied the damage evolution characteristics of raw coal under uniaxial and triaxial cyclic loading using acoustic emission technology. ey concluded that acoustic emission phenomena during the initial stage of loading is more significant under graded cyclic loading conditions and that raw coal exhibits different damage evolution characteristics at different cyclic stages
Xiao et al [22] studied the law of energy conversion and acoustic emission characteristics of coal under cyclic loading. ey proposed that coal instability can be predicted by the abrupt rise of AE energy and abrupt drop of AE amplitude
Summary
Damage failure mechanisms and mechanical properties of rocks and coal under monotonic loading (uniaxial and conventional triaxial compression) have been extensively studied [1,2,3,4,5,6]. Liu et al [18] studied the damage evolution and acoustic emission characteristics of coal under uniaxial compression. Acoustic emission information is believed to be closely related to the formation, expansion, and penetration of primary fractures in coal and can provide insight into its deformation and damage evolution behavior. Zou et al [21] systematically studied the damage evolution characteristics of raw coal under uniaxial and triaxial cyclic loading using acoustic emission technology. Many studies have contributed important achievements in understanding the acoustic emission characteristics of rock deformation and failure, these features during different loading paths remain scarcely reported, especially for the fatigue damage failure evolution of coal under cyclic loading. We use the results to better understand the characteristics of acoustic emission and the Felicity effect under different stress levels and cyclic loading frequencies during coal fatigue failure
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
