The influence of soil density and moisture content on the impulse from shallow buried explosive charges

A series of experimental trials has been conducted at University of Sheffield, UK to assess the effect of density and moisture content of Leighton Buzzard sand on the impulse applied to a target when exposed to loading from the detonation of a shallow-buried charge. Sand samples have been prepared in stiff cylindrical steel bins 1000mm internal diameter and 750mm deep, and loading has been generated using explosive charges of up to 1kg PE4 buried at a depth of <100mm. Preparation of the sand has been carefully controlled, with densities consistent to within +/- 3kg/m3 and moisture content within +/-0.05% of target values in sand masses >1000kg. The impulse has been determined from vertical displacement vs time records of a c. 1500kg reaction mass, recorded using high-speed digital video and laser displacement gauges. Results will be presented which demonstrate that it is possible to achieve a very high level of consistency in the loading even at this relatively large scale, with measured impulses typically within a spread of +/-2% for nominally identical tests. This spread is considerably lower than in previously reported studies at this scale, and facilitates a careful and accurate parametric analysis of the effect of variations in the geotechnical conditions on the impulse imparted to the target.