Abstract: During tunnel outline excavation,airdecked charge as a newtype technology is being used gradually.The decoupling coefficient will directly influence the result of smooth blasting.Using rock mechanical properties obtained from airdecked charge testing site of tunnel excavation in Dabie mountain,and CowperSymonds failure criterion,a double arch decoupling charge blasting model was established by using LSDYNA,to obtain decoupling charge blasting stress and simulate the process of blasting stress over time. The stress of hole wall and its damage situation was analyzed in the case of the chargelength at 1.4m,1.5m,1.6m,1.7m and 1.8m,from which an optimum longitudinal decoupling coefficient in the range of 1.94 and 2.18 was obtained for Rock Class III in the hole depth at 3.5m.This offered a theoretical foundation for the parameters for presplitting and smooth blasting.

Key words: Tunnel, Airdecked Charge, Smooth Blasting, Longitudinal Decoupling Coefficient；LSDYNA