Validation of numerical modelling of explosive ground shock propagation in dry sand with digital image correlation experiments

Explosions from buried charges generate compressive stress waves, commonly referred to as ground shock, which displace and accelerate structures located both underground and on the surface. In this study, the effects of ground shock on a simplified buried structure have been recorded experimentally through digital image correlation from stereo high-speed video cameras at one hundred thousand frames per second, with this used to validate a numerical model. This testing utilised a steel pipe with a clamped aluminium base plate (to represent a deformable structure), filled with varying depths of Leighton Buzzard sand. From the DIC data, displacement-time histories were extracted from an area of 380 x 160mm of the base plate (approximately 3500 individual locations), allowing for high spatial and temporal resolutions for comparison against modelled outputs. Numerical modelling in LS-Dyna, utilising an MMALE scheme, was found to capture the shock propagation well, with good agreement between experimental and numerical findings, particularly at close stand-offs. As stand-off increased, mass soil movement had a larger influence on deformation of the structure, which the model struggled to capture effectively.