Close range effects on a concrete wall of an underwater explosion - a numerical approach
Olivier Loiseau, Karine Cheval, Bruno Autrusson, Crête, 29-31 mars 2004
The concern of this paper is the study of the effects on a thick concrete wall of the detonation produced by an underwater explosive device, in close range. This work applies in particular to the study of some industrial pools, filled with water and a few meters deep. These pools are generally build so as to ensure a certain watertightness, this function being obtained for instance by covering the internal surface with an internal liner, a few millimeters thick and made of stainless steel. Here, we focus on the possible loss of this function both by the damage caused to concrete and the perforation of the liner, due to the local effects of the explosion independently of the global structural response. In the paper, based on the Holmquist model for the behavior of concrete under high pressure, we first determine a clear transition between close range and far-field type solicitations. For a given explosive device, defined by its mass, the close range domain is materialized by a minimum reduced radius under which the quasi static characteristics are significantly modified due to the high pressure subsequent to the detonation. In second, we present a numerical example : the goal is to determine the depth of damaged concrete in relation with the explosive device mass and position. This problem is solved using the explicit dynamics code LS-Dyna and a weak coupling between an eulerian and a lagrangian computation. This example is commented and the results have been compared with experimental data.