Abstract:

Cut method not only affects the tunnel excavation efficiency, but also affects the blasting vibration control effect. No. 3 bid section of No. 3 line of Phase 1 project of Qingdao Metro crosses underneath an existing hospital. In the paper, the blasting in the tunneling under the hospital is studied. 3 parallel cut methods, i.e., smalldiameter single hollow hole cut method, largediameter single hollow hole cut method and largediameter double hollow hole cut method, are analyzed in terms of tunneling advance rate, blasting hole utilization rate and peak value of vibration velocity of monitoring point at ground surface above the working face. Conclusions drawn are as follows: 1) Under the same conditions, the largediameter single hollow hole cut method is superior to the other 2 cut methods in terms of blasting hole utilization rate and vibration control. The largediameter single hollow hole cut method is used in the blasting of tunnel underneath the hospital and good effect has been achieved, with the vibration velocity being controlled under 2 cm/s; 2) The tunnel excavation efficiency and vibration control effect of parallel cut method are related to the ratio between the distance from the charged hole to the hollow hole (l) and the diameter of the hollow hole ().

Key words: parallel cut, blasting, vibration, excavation, largediameter hollow hole