Experimental investigation on pillar burst under high-stress conditions: insights from an energy perspective

Pillar burst is one of the common geological disasters in deep mines. However, the mechanism of pillar burst has not been well studied, especially the energy mechanism. In this study, a novel horizontal bidirectional unloading method is proposed to simulate pillar bursts under different stress conditions. Then, evolution process of different energies during the pillar burst are captured. Last, a rockburst energy criterion is proposed and verified. The results show that the failure process and failure mode of pillar burst is consistent with engineering practice, and the intensity of pillar burst gradually increases with the increase of stress and this rule is confirmed by the evolution processes of different energies. The elastic energy density remains constant after horizontal stresses detaching, while the total and dissipation energies substantially increase. The evolution process of acoustic emission energy and temperature on the free faces of the rock samples is consistent with the crack development process. Besides, infrared radiant energy increases with increasing of axial stress, which could be considered an indicator for evaluating the intensity of pillar bursts. The ejection speed of rock fragments is determined by particle image velocimetry technology and the average kinetic energy increases almost linearly with axial stress. The uniaxial compression experiments are performed under the same condition to calculate excess energy ΔUe. Then, the energy criterion is verified compared with the required energy of uniaxial compression failure and pillar burst.