Monitoring and analysis of blasting vibration in diversion tunnel excavation

Analyzing the geological condition of the diversion tunnel, and according to the layout features of the tunnel and field construction situation, the scheme of fixed measuring points was adopted to monitor the tunnel excavation By analyzing the test data, we found that the particles vibration velocities have obvious directional effect; and the vibration velocities of the particles those faces towards free face are much greater than those of the particles in other direction. If measuring points and explosion points are not in the same elevation, and when the ratio between elevation difference and blast center distance is relatively large, the difference of the peak vibration velocities in different directions caused by elevation effect is obvious; and when the ratio is relatively small, the elevation effect weakens obviously. For the relation between elevation difference and the blasting vibration attenuation, previous studies put forward some amended formulas; however, these formulas took the elevation difference as an independent variable to consider, and the physical meaning was not clear. According to the previous data analysis, considering the practical meaning of elevation effect and combining dimensionless analysis, we take the ratio between elevation difference and blast center distance as the impact factor of elevation effect, and modify the traditional empirical formulas of blasting vibration attenuation. Through contrasting and analyzing, the modified empirical formula is relatively precise. In the meantime, the condition that vibration velocities exceeded the standard is analyzed and blasting parameters are adjusted in time, which control the damage effect of blasting vibration effectively. This research plays an important role in guiding the excavation blasting construction in tunnel projects and assuring the safety of dam body and dam curtain, which ensures the successful completion of blasting construction.