Study on leading tunnel vibration response and isolation layer optimization in rear tunnel blasting in large-span tunnel construction

Based on the TJ-02 section of Jiaozhou Bay Second Subsea Tunnel, this study explores the leading tunnel’s vibration response to rear tunnel blasting and the vibration reduction performance of isolation layer schemes under the double-side drift method, combining on-site monitoring and numerical simulation. Results show that the leading tunnel’s partition wall adjacent to the rear tunnel’s cut area suffers the strongest vibration. The peak particle velocity (PPV) attenuation rate in the excavated zone behind the tunnel face is notably higher than that in the unexcavated zone ahead. The 4 cm-thick, 5.5 m-high, 10 m-long L-600 polyethylene closed-cell foam isolation layer achieves the optimal vibration reduction effect, with an average attenuation amplitude of 61.9 % at the lower partition wall of the leading tunnel. This study provides technical references for similar large-span tunnel construction.