In order to explore the influence law of damage accumulation effect on the surrounding rock of a large span chamber under multiple blasts,acoustic method and borehole imaging method were used in a large span chamber blasting project.The results show that the ultrasonic wave velocity decreases with the increase of blasting times.Besides,the damage value of surrounding rock increases,but the growth rate decreases and finally becomes stable.After several blasts,the radius of the broken rock zone in the surrounding rock of the chamber has gradually expanded from 2.8 m to 3.2 m,and the broken rock zone at the top of the chamber is larger than that at the side wall.Therefore,the stability of the surrounding rock at the top of the chamber must be taken into account in such cases.In addition,the influence of damage accumulation caused by multiple blasts on the radius change of the broken rock zone should be fully considered in surrounding rock support and safety protection.