Rock damage is considered as a state of instability phenomenon under the driving of energy

the law of energy evolution in the process of deformation and failure can reflect the essential characteristics of rock mass deformation and failure. The loading and unloading tests were carried out on coal samples to explore the laws of energy evolution under different unloading confining pressure rates. The experimental results show that before the peak stress

the coal sample mainly experiences the energy storage and dissipation

whereas it mainly experiences the energy release and dissipation after the peak stress. It is found that when the unloading confining pressure rate is high

the duration of unloading confining pressure is short

the internal cracks of coal sample extend and circumferentially deform insufficiently

and the powers for energy dissipation and overcoming confining pressures are small. Moreover

most of the energy release when the coal sample ruptures

which make the coal sample damage seriously. Meanwhile

when the unloading confining pressure rate is larger

the damage rate of the coal sample increases faster before and after the rupture

which results in the sharp increase of the damage curve. Therefore

when the high-stress coal is excavated with a high construction speed

it is easy to cause a sudden release of a large amount of accumulated energy

causing serious disasters.