Dynamic Response and Mitigation of Tunnel Subjected to Internal Explosion

Tunnels play a crucial role in modern highway construction, serving as essential components that facilitate efficient travel within and between cities. Despite their inherent advantages, tunnels remain vulnerable to extreme loading events such as internal explosions. This study investigates the response of a reinforced concrete box road tunnel subjected to internal blast loading, by employing the Coupled Eulerian-Lagrangian (CEL) approach in Abaqus/Explicit. Two charge weights of TNT explosive, 227 kg (classic car), and 454 kg (SUV/van), were studied to assess the impacts of blast intensity. The tunnel response was examined by analyzing pressure-time histories, displacement, and damage progression at two critical observation points along the tunnel lining: the tunnel roof, and tunnel side wall. Mitigation influences using ultra-high-performance concrete (UHPC) also investigated. The results indicate a significant relationship between explosive mass and structural behavior, where larger TNT quantities result in greater pressure, increased displacement, and severe localized damage. The pressure–time records show clear wave reflections in the confined tunnel setting, increasing structural stress at certain locations. The displacement patterns further emphasize the susceptibility of specific areas of the tunnel, especially the roof and sidewalls, where considerable nonlinear deformations were detected. The use of UHPC contributes to a significant reduction in structural deflection, enhancing overall damage tolerance under blast loading.