The blasting vibration in advance of a working tunnel was observed in a existing tunnel, that is active and crosses above 20m distant from the surface of the working one, and in rock which is not affected by the tunnel.
Vibration caused by blasting has an important effect upon underground structures. The dynamic response of the structures caused by blasting vibration is characterized by the combination among their supports and the condition of rock around the tunnel. It is expected that the vibration mode is variable according to a relationship between the natural rock and the weak one which is influenced by excavation, that is, the plastic state is generated in rock at the circumference of the tunnel.
Boundary element method was employed for examining the possible effects of a wide range of ground conditions. The magnification factor, which is defined as the ratio of the observed amplitude at the wall of tunnel to the input at same frequency, increases according to the decline of elastic wave velocity in the loosened zone and the growth of the thickness.
