Abstract: The systematic study of the blasting impact is of great importance to the dynamic response of the newly-built and the existing tunnel supporting structure. Taking a new tunnel neighboring the existing tunnel as a case， the three-dimensional model about the effect of the blasting construction on the existing and newly-built tunnel supporting structure was established. Combined with the LS-DYNA explicit dynamic analysis procedure and the multi-material flow-solid coupling algorithm， numerical simulation on the blasting mechanism of newly-built tunnel was made with relative accuracy. Besides， the dynamic response rules of the primary supporting of the newly-built tunnel and the secondary lining of the existing tunnel under different surrounding rock blasting load were studied， thus obtaining the vibration velocity distribution rule and the displacement nephogram change of them under different working conditions. The results show that the dynamic response rules of the secondary linings of different surrounding rocks are very similar， and that the explosive shock wave firstly transfers to the blasting side wall of the secondary lining of the existing tunnel and the peak vibration speed value of the mass point in the secondary lining structure along the X direction is at the maximum and attenuates very fast. When there is a certain distance from the working face of tunnel， the peak velocity at the arch foot of newly-built tunnel exceeds to that at the vault， and the vibration velocity in different locations display as arch foot， vault and arch waist from high to low in order. The vibration along the Z direction in the initial support with 3 vibration directions of X， Y and Z is larger， that is， the centerline of the tunnel， and its attenuation is faster. After the explosive is detonated， vibration occurs from the working face to the tunnel entrance under the action of blasting shock wave at different positions of the initial support in the newly-built tunnel. Besides， in the same fracture surface， the vibration velocity in the positions of the vault and of the arch foot is bigger， which should be given more monitoring during the construction.

Key words: Tunnel engineering, Explosion shock loading, Initial lining of a new tunnel, Lining of existing tunnel, Dynamic response