Study on the Transient Response of Composite Lined Tunnels Subjected to Blasting P-Wave

Blasting-induced vibrations from new tunnel construction pose a significant threat to the structural safety of existing tunnel linings due to dynamic stress concentration. To address this, this study establishes a transient-response analytical model for composite lining tunnels using wave function expansion and a combination of the Duhamel integral and Fourier transform methods. Through a case study of the Hongshan South Road Tunnel, the research systematically quantifies the influence of critical factors such as load rise time, lining thickness, and material stiffness. Numerical results reveal that under blasting P-wave action, the inner vault of the secondary lining exhibits the most significant dynamic stress concentration, identifying it as the primary vulnerable zone. Furthermore, peak dynamic stress and vibration velocity increase sharply as the load rise time decreases, indicating that short-duration, high-intensity impacts present the greatest hazard. To mitigate these effects, the study identifies several optimization strategies: increasing the thickness of the initial support and employing high-modulus materials effectively reduce stress peaks. Specifically, maintaining the elastic modulus ratio of the surrounding rock to the initial support at approximately 2.0 provides an optimal balance for enhancing blast resistance. The findings suggest that tunnel design should prioritize optimizing the stiffness of the initial support and utilizing grouting to reinforce the surrounding rock. This research provides a robust theoretical framework and specific parameter optimization directions for the seismic and blast-resistant design of composite lining tunnels.