Safety assessment of tunnel infrastructure under upgrades of ventilation systems through side rock blasting

Early-designed tunnel infrastructure in rock environments often requires ventilation system upgrading, which may involve rock excavation or controlled blasting adjacent to existing tunnel linings. Under such conditions, tunnels may be exposed to damage induced by TNT-based blasting. The severity of tunnel response depends on stand-off distance, TNT charge weight, detonation layout, tunnel configuration, and rock mass properties. Tunnel safety under rock blasting on the side consolidates an essential engineering problem that has been rarely investigated in the literature. As a novel contribution to the state of the art, this study develops a three-dimensional numerical framework to assess the safety of tunnels subjected to sequential side rock blasting. High-fidelity nonlinear material models and a coupled Eulerian–Lagrangian formulation are adopted, and the numerical approach is validated against field test data. Parametric analyses show that tunnel damage decreases significantly with increasing stand-off distance and rock strength, while distinct response mechanisms are observed under different blasting configurations. Tensile damage concentrates in critical regions under close-range blasting but remains negligible at larger stand-off distances. A comparative analysis of side and top blasting further highlights the influence of loading configuration on tunnel response. The results provide quantitative insight and practical guidance for safe blasting design during ventilation upgrading of existing tunnel infrastructure.