Experiments and modelling for characterisation and validation of a two-phase constitutive model for describing sands under explosive loading

Abstract

Specification of constitutive equations and validation of advanced material models is a developing area which is yet to be adequate for the complexity of granular geological materials such as sands and soils. In consideration of these materials as an air-solid mixture, the present work suggests a consistent procedure for specifying the constitutive equations to close a two-phase model for these materials. The following data are used: (i) Hugoniot data for the solid constituent specifying the equation of state; (ii) rate sensitive strength data of the solid constituent for the plasticity constitutive equations; (iii) data from Split Hopkinson Pressure Bar (SHPB) tests for the compaction kinetic; and (iv) post-test analysis of encapsulated samples loaded by High Explosive for the consolidation response. The model specified with this procedure and implemented in the CTH hydrocode is validated with independent tests in an axisymmetric setup. The suggested experimental setup observes deformation in time of a circular plate loaded by sand ejecta from a detonating buried HE charge, using flash X-ray radiography. These experiments characterise both temporal and spatial distribution of the impulse and also enable an integral assessment. The experimental investigation of a calcite sand, several silica sand variants, a glass powder and a soil mixture was conducted in the present paper, employing the methodology developed for the material characterisation and model validation. Comparison of the test results for these materials with the calculations demonstrated a good agreement.