This paper presents the experimental study of the granite rockburst under four different unloading rates. With the help of the collected fragments measurement after tests

the scale features of fragments can be obtained. Acoustic emission system is used to monitor the internal damage of the rock; and the typical time-frequency analysis tool is applied to the major frequency extraction of every acoustic emission (AE) waveform. The tested results indicate that the total number of fragments and the portion of fragments with blocky structure and plate shape have a decreasing trend with the unloading rate dropping down. The AE major frequency band is found to be located in the moderate low frequency band and it is up-shifting as the unloading rates decrease changing from intensive broadband to discrete narrowband. According to the distribution of RA and AF

the crack type evolution can be determined. During the unloading rockburst test

the cracks generating in the specimen are mainly tensile cracks. Further decreases in unloading rate do appear to drive the AE signals reduced indicating crack amount decrease. All these results will be helpful for us to understand the rockburst mechanism under different unloading rates and prove the feasibility of adjusting excavation speed to reduce rockburst risk in field site.