Numerical and reduced-scale experimental investigation of blast wave shape in underground transportation infrastructure

Abstract When an explosion occurs in a tunnel, the study of the blast wave quickly becomes complicated, owing to the multiple propagation patterns of the blast wave (incident wave, regular and Mach reflections) and to the geometrical conditions. Considering this problem, two patterns can be revealed. Near the explosive, the well-known free-field pressure wave can be observed. After multiple reflections on the tunnel's walls, this overpressure behaves like a one-dimensional (1D) wave. One aim of this paper is to determine the position of this transition spherical-to-planar wave propagation in a tunnel using both numerical and reduced-scale experiments, and thereby validate the dedicated law established in a previous work. For this purpose, a detonation of TNT in a tunnel with a cross-section of up to 55 m 2 is considered. Results show good agreement between the numerical simulations and experiments. The transition zone between the three-dimensional (3D) and the 1D wave is well detected. An application to a simplified subway station is also investigated which shows that significant planar waves can be transmitted to the neighboring stations via the junction tunnels.