Abstract: For a deep circular tunnel excavated by the full-face millisecond delay blasting, a two-dimensional mechanical model is firstly developed to calculate the vibration caused by dynamic loads in the process of rock blasting fragmentation. Dynamic loads include transient release of in-situ stress occurring on excavation faces and blast loading. By using this theoretical model and analyzing the vibration signals measured in the field, characteristics of the vibration frequency and their influence factors are subsequently studied. The results show that the vibration frequency in deep tunnel during blasting excavation is mainly affected by the duration of stress release, rising time of blast loading and the dimension of excavation faces. Rock vibration in the vicinity of blasting source is primarily caused by blast loading. Since the rising time of blast loading is much shorter than the duration of stress release, the vibration caused by blast loading thus has a higher frequency than that induced by the transient release of in-situ stress, and the peak velocity of vibration attenuates faster with the distance. At the far distance, the vibration generated by the transient release of in-situ stress may become a primary component. It is also found that the vibration caused by the combined action of dynamic loads has two dominant frequency bands. The transient release of in-situ stress is mainly responsible for the low-frequency vibration, while the blast loading accentuates the high-frequency vibration.

Key words: deep tunnel, excavation, blasting, transient release, vibration, frequency