Secondary debris resulting from concrete slabs subjected to contact detonations

Abstract

As a consequence of terrorist attacks with explosives and malfunction of machinery detonations can lead to secondary debris on the protective side of a concrete wall. The term secondary debris in this context describes the debris resulting from a breakup of the loaded concrete structure in contrast to primary debris which results from the explosive or its casing. A test series has been conducted in order to investigate the physical phenomenology of the damaging process. A total of 15 reinforced concrete slabs with scaled thicknesses between 1.6 and 2.8 cm g−1/3 were loaded by contact detonations. The protective side of the concrete slabs was recorded with high-speed cameras during testing, and the damaged concrete slabs were measured with 3D-scans afterward. The acquired data will be evaluated for the velocity and mass of the secondary debris, to build the basis for an empirical model, which can make predictions about the occurring secondary debris. The objective of this paper is, to present the conducted experiments and propose the first part of an empirical model. This model predicts the geometry of the spalling crater on the protective side of the concrete slab, as well as the maximum velocity of the secondary debris. In following papers, the correlation between the mass and the velocity of the secondary debris will be derived from numerical simulations. With this, predictions can be made about the effects of the secondary debris on humans and installations on the protective side of the concrete slabs.