Abstract: Studying the unloading mechanical properties and energy dissipation law of rock is of great significance for understanding
the damage mechanism of surrounding rock,accurately judging the stability of surrounding rock,and economically
and reliably supporting underground engineering. In order to study the influence of unloading rate on the unloading mechanical
properties and damage of granite rock,constant axial pressure unloading confining pressure tests under different unloading rates
were carried out. The study found that in the case of rapid unloading,its mechanical properties accelerated degradation,from
the stable damage development stage directly to the damage stage. When the unloading rate is small,during the unloading
process,the stress is continuously adjusted,the mechanical properties are slowly deteriorated,and the plasticity is gradually enhanced.
As the unloading rate decreases,the elastic energy accumulated at the peak point of the rock sample gradually increases,
but the proportion of elastic energy continues to decrease. The damage variables of granite are obtained from the law of energy
dissipation and the law of acoustic emission,respectively. The variation of the two under unloading conditions is highly
consistent. At high unloading rate,the acoustic emission ringing count of the sample before fracture has strong suddenness. The
research results have important scientific value and engineering guiding significance for the safety design and disaster prevention
and control of deep buried tunnels,mines and other underground projects.

Key words: unloading mechanical properties,energy change law,damage,acoustic emission