Smooth blasting is the main method for controlling excavations in hard rock tunnels,but due to the complex mechanism and process of rock fragmentation by blasting,as well as the rough design of blast parameters,it is difficult to achieve a smooth excavation profile for the entire tunnel.This study focuses on the Level Ⅲ hard rock section of the Zhaishan tunnel,and through a large number of blasting tests and investigations,it was found that there were problems such as over-excavation and under-excavation,misfire,and secondary blasting construction around the tunnel profile after the original blasting plan was carried out.Based on relevant specifications and engineering experience,optimization measures were proposed for the blasting parameters,including reducing the spacing between contour holes,increasing the number of relief holes,using water bag as the charge decking and stemming,as well as reducing the amount of explosives loaded in each hole.The results showed that the optimization measures can improve the utilization of explosive energy,achieve uniform fragmentation of the rock mass,and control over-excavation and under-excavation of the tunnel perimeter rock mass.The blast parameter optimization also results in smooth and round tunnel profile with clear blast hole marks,which helps to improve the quality of excavation and accelerate the progress of tunnel construction.