Study on the Longitudinal Decoupling Coefficient of Air-decked Charge for Tunnel

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,1.7mand 1.8m,from which an optimum longitudinal decoupling coefficient in the range of 1.94and 2.18was 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.