Research on Coal Acoustic Emission Characteristics and Damage Evolution During Cyclic Loading

Abstract

The acoustic emission, energy, and damage evolution of coal samples for three kinds of uniaxial cyclic loading and unloading are deeply analyzed in this study. The evolution of total absorption energy, elastic strain energy, and dissipated energy of coal samples is related to the stress path, and the increasing amplitudes cycle loading has an obvious damage effect on coal samples. During the loading stage, the acoustic emission phenomenon is most active when loading is increasing and the Felicity and post-Kaiser phenomena appear. The acoustic emission phenomenon during constant loading does not obviously change, but rather becomes active with the increase of the equivalent load. The damage to the coal sample shows nonlinear change increasing loading and unloading and shows linear change for other stress paths. Compared to waveforms with stepwise increasing amplitudes cyclic loading, the failure process of the coal sample is more closely related to the size of the external load, which indicates that reasonable hydraulic design is beneficial to the stability of the confining pressure in the chamber of an underground pumped storage hydropower station.

Numerical Simulation of Acoustic Emission Events in Supporting Roadways under Different Dynamic Loads

“…Te results showed that the characteristics of the AE waveform parameters well refect the growth behavior of coal HF. Zhili et al [10] studied the AE, energy, and damage evolution of coal samples under three uniaxial cyclic loading and unloading conditions. Based on the Braziliansplitting test and uniaxial and triaxial compression tests, Su et al [11] and Yang et al [12], respectively, studied the evolution of rock failure and AE characteristics under different loading rates, which further deepened the understanding of rock failure process and provided theoretical support for rock stability analysis in mining design and construction.…”

Study on Energy Density Distribution and Mass Fractal of Deep Saturated Coal Samples under Uniaxial Stepwise High Stressed Loading and Unloading Path

“…Deep mining is often in the complex environment of high geostress, high karst water pressure and strong mining disturbance [1][2][3][4]. While the coal in the roadway is bearing deep high stress, it is also affected by the repeated disturbance of coal seam group mining and surrounding mining activities [5][6][7][8] so that the internal cracks and damage continue to develop under the stress path of cyclic loading and unloading [9][10][11], resulting in frequent failure of anchor bolt or cable and continuous degrade of structural stability [10,12,13]. Relevant studies [14,15] also show that the strength characteristics and deformation law of coal (rock) under cyclic loading and unloading path are significantly different from bearing characteristics of coal (rock) under uniaxial compression path.…”