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 reections) and to the geometrical conditions. Considering this problem, two patterns can be revealed. Near the explosive, the well known freeeld pressure wave can be observed. After multiple reections 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 simplied subway station is also investigated which shows that signicant planar waves can be transmitted to the neighboring stations via the junction tunnels.

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The aim of this work is to assess the influence of the dynamic stresses (due to the projectile displacement and the gas pressure) on the lifetime of certain medium caliber (less than 40 mm) gun barrels. First, an experimental study of tube dynamics under high speed loads was made. The large number of experimental measurements made it possible for us to identify the forcing effect of the projectile. In parallel, experimental samples were submitted to periodic traction-compression forces in order to obtain the material parameters of the barrels used in the study. Second, a finite element (FE) model was elaborated which faithfully forecasts the experimental strain records. Three-dimensional modeling permitted us to correctly evaluate the response in the zones of stress concentration. Third, a lifetime calculation was performed. This shows that the lifetime of the barrel is determined by the most constrained zones during firing: in the present case by the stresses appearing at the bottom of the grooves.