Monitoring blasting excavation of shallow-buried large-span tunnel and vibration reduction technology

Based on the engineering background of the Miaoya forked tunnel, the study of vibration characteristic of the ground at the large-span shallow part and blasting vibration reduction technology for large-span excavation has been done, according to the regression analysis for the results of monitoring on blasting vibration, the mathematical model for vertical propagation of blasting vibration has been established. Some conclusions are obtained by analyzing the vibration characteristic of the ground and the tunnel, the dominating vibration frequency at surface mass point mostly focuses on low frequency, the decreasing tendency of dominating vibration frequency at surface mass point is not obvious when distance increases, because some blasting earthquake waves are absorbed by the earth surface covered with soil of certain thickness; the high frequency is mostly absorbed by the concrete of the tunnel lining, so the blasting vibration impacting on the rock becomes weaker, the ground blasting vibration velocity of the excavation region is higher than that of the rock region; the ground blasting vibration velocity at the top of excavation region should be less than that of blasting security control in the large-span shallow tunnel.