Properties of concrete subjected to explosively generated impact and impulse loading
The use of models to simulate full scale structural effects has long been attempted and various types of models have been developed. One type, the replica model, in which prototype materials are used was selected for this study. Much interest has been shown in the past on damage prediction based on extrapolation of the results from small explosive charge tests. In this study, scale model concrete ground slabs have been subjected to high rates of loading using explosively propelled copper and aluminium projectiles impacting on the concrete to air surface and explosive devices buried in the soil beneath the concrete slab. The copper or aluminium projectile was produced from a truncated cone of metal in direct contact with a shaped charge of RDX/TNT explosive. The subsurface charge was uncased PE4 plastic explosive inserted into a hole through the slab and into the soil. In many tests the hole was produced by the metal jet impact without any modification. Other scaled concrete targets have also been tested using explosively propelled projectiles. Transient results from the tests have been collected using high speed photography, electrical resistance strain gauges, crack velocity detection devices and a projectile velocity measurement system. Other measurements of post test damage have utilised stereoscopic photography, coloured particles of soil in the foundations of the concrete slabs and a scanning electron microscope. Concretes of various strengths and densities have been used but all conformed to a scaled down specification for pavement quality concrete. Explosive charges were similarly scaled in size from prototype devices. Some additional experimental work has been carried out to obtain fundamental data on the explosive charges and on 'perspex', metal and concrete blocks for calculation and comparison purposes. Comparisons are also made with work of a related nature undertaken at larger scales.