Experiments and Constitutive Modelling of Sand Ejecta Impact

Abstract

Analysis of the dynamic response of geological porous materials under shock and explosive loading is an important problem in numerous mining and military applications. The experimental characterisation of porous materials with planar shock impact and split Hopkinson pressure bar (SHPB) tests is well developed. However, progress in the test methodology and validation of advanced models is not yet adequate for the complexity of the materials. The present work suggests an experimental set-up aimed at the dynamic observation of momentum transfer from the plume of a porous material ejected by a high explosive (HE) charge. The momentum transfer provides data for model validation and is assessed from the target plate deformation due to impact by the ejecta from a HE charge buried under a layer of a porous material. The porous material used in the paper is represented by calcite sand. An earlier developed two-phase material model for porous materials implemented in the CTH hydrocode is employed for simulating the dynamic behaviour of the calcite sand. The validation experiments are complemented by tailored characterisation experiments for populating parameters within the model which describe (i) the plasticity and compaction behaviour of the sand; and (ii) a kinetic governing shock consolidation transformations within the sand. This includes an analysis of confined SHPB tests and the response of encapsulated sand loaded by HE products in two separate series of tests. The two-phase material model is validated for the calcite sand and comparison with the experimental data demonstrates a good description of the material behaviour.