Abstract: The authors evaluate the safety and blast resistance performance of assembled frame tunnels subjected to explosive loads by analyzing the influence of their unique segment-connection systems. A three-dimensional refined numerical model is established using a coupled Eulerian-Lagrangian algorithm to simulate internal and surface explosion scenarios. The dynamic responses under varying explosive equivalents and charge positions are examined, and the effectiveness of corresponding protection measures is assessed. The results indicate the following: (1) The damage characteristics of the tunnel closely relate to the explosion position. Central explosions cause pronounced deformation of the middle partition wall, whereas edge explosions produce the maximum deflection at the midspan of the top plate. With increasing explosive equivalent, the failure mode of the middle partition wall transitions from bending to combined bending-shear failure. (2) Surface explosions cause the maximum damage at the center of the top plate. Because the assembled structure contains discontinuous connections between segments, sliding shear stresses and segment misalignment occur under explosive loads, resulting in response characteristics that differ considerably from those of monolithic cast-in-place tunnels. (3) Strengthening vulnerable sections with carbon-fiber-reinforced polymer and additional shear keys improves blast resistance performance.

Key words: assembled frame tunnels, dynamic response, structural damage, blast resistance performance, numerical model