PREDICTION AND EXPERIMENTAL RESULTS OF CONFINED UNDERWATER BLASTING GENERATORS

摘要

Underwater blasting operations have been, during last decades, subject of research and development of maritime blasting operations, including torpedo studies. Aquarium tests, for the measurement of blasting energy of industrial explosives, are based in studies of confined underwater blast wave generators (WBWG). The present study shows the behavior of WBWG, based in water plastic containers, having in the center a detonator inside a cylindrical explosive charge. The used explosive was an industrial ammonium nitrate emulsion explosive. Prediction of detonation properties of emulsion explosive were done using thermochemical computer code, - named THOR, with four calculating clusters, related to the thermal equation of state (EoS), to the energetic equation of state, to the conservation equations - mass, atomic species, momentum and energy, and to the reaction regime - Chapman-Jouguet (CJ) detonation. Emulsion explosive is assumed as mixture of 77.6 % of ammonium nitrate, 4.9% of Fuel, 0.03% of air (corresponding to . the sensitizing air microballoons) and 17.59 % of water. Expansion of detonation products, inside water of WBWG, is predicted starting from THOR results. Good adjustment (between the theoretical adiabatic and isentropic curves, from CJ point obtained by THOR code, and predicted expansion curve using JWL equations) allow to define and optimise JWL parameters, under restrictions conditions. Gruneisen coefficient of 0.328 reveals to be a very good compromise value. Autodyn 3D predictions of WBWG, using a cubic meter water container, show the possibility of having emulsion charges without destruction of WBWG containers. Experimental results confirm this assumption. It is always observed the elastic deformation of containers wall, under the water shock reflections, changing from its original cubic shape to a transient spherical one. Water pressure levels, close to plastic walls, under maximum admissible charges, are closed to 6 MPa. Experimental results validate simulations and prove the possibility of a new nondestructive method to collect detonation products of small charges.