(1. Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031, China; 2. National Engineering Research Center of Geological Disaster Prevention Technology in Land Transportation, Southwest Jiaotong University, Chengdu, Sichuan 611756, China; 3. Sichuan Highway Planning Survey and
Design Institute Ltd., Chengdu, Sichuan 610041, China)
Abstract：To investigate the longitudinal dynamic response characteristics of mountain tunnels with wall-type portals, a simplified mass-beam-spring mechanical model was developed. In this model, the portal retaining wall is idealized as a lumped mass, while the tunnel structure is represented as a Timoshenko beam. Based on this model, an analytical solution for the steady-state response of tunnels with wall-type portals was derived using the Green?s function method. The correctness and effectiveness of the analytical solution were validated through numerical experiments, and the influence of key parameters of the theoretical model on the dynamic response of tunnel structures was analyzed. The results indicate that the analytical solution aligns well with the numerical findings, confirming the reliability of the model. When the portal mass is excessively large or its foundation stiffness is inadequate, the portal structure amplifies the displacement of the tunnel near the entrance. Conversely, a lighter portal or a stiffer foundation mitigates this displacement. The influence of the portal on the tunnel increases with the contact stiffness between them. Additionally, poor-quality surrounding rock at the tunnel entrance significantly diminishes seismic resistance. Two primary strategies exist for enhancing the seismic performance of tunnels with wall-type portals: the first involves adjusting the portal?s mass or foundation stiffness to achieve deformation compatibility with the tunnel structure; the second entails implementing seismic mitigation measures to reduce the interaction forces between the portal and the tunnel structure. These findings provide valuable insights for the seismic design of mountain tunnels featuring wall-type portals.
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2025, Vol. 44 
