A precisely-controlled blasting method and vibration analysis for tunnel excavation under dense buildings

To meet higher security requirements for blasting vibration from urban tunnel excavation under dense buildings, a new blasting technology was proposed and the corresponding method for obtaining parameters was explored.The proposed blasting technology uses non-electric detonators to precisely control blasting vibration.Chongqing Yuzhong connecting tunnel was taken as the research background.By applying Fourier function and MATLAB software, the vibration velocity curves were fitted for single-hole blasting with different charges and the quantification data of vibration superposition at different millisecond intervals from 1 to 50 ms were analyzed.The vibration-reduction effect was discussed for different millisecond intervals.The parameters about blasting charge and detonating time delayed were determined under given vibration velocities.Interval characteristics of each period between detonators in the field were measured and analyzed.Accordingly, the blasting scheme was designed, which using hole-by-hole cut blasting to control vibration.The blasting vibration velocity measured in the field is below 1.00 cm/s, and the corresponding reasonable single-hole charge is 1.2 kg for avoiding vibration superposition.The vibration velocity peak occurs after the detonation of the first or second-period detonator in the main cut area, which is consistent with the theoretical results.And the vibration velocity decreases by more fifty percent after 60 ms of hole-by-hole blasting. So blasting vibration can be precisely controlled by using non-electric detonators under high safety standard.