Near – Field Pollutant Dispersion Due to Explosions

When an explosive is encased in a material that is prone to disintegrate into small particles, these particles are dispersed over a wide area by the explosion and subsequent aerodynamic effects. This situation occurs for example in the case of covered-earth detonation for ammunitions disposals and dirty bombs. The dispersed particles may have adverse effects on the environment and human health. Thus, suitable data need to be collected in order to develop accurate models to predict the extent and level of contamination. The purpose of this research is to investigate the blast wave, plume evolution and particle dispersion around full–scale buried detonations. Two explosives of charge mass 19 kg TNT equivalent and 40 kg TNT equivalent were detonated using World War I
explosives. The following instruments were used: blast pencils to measure the blast wave, high speed camera to measure the plume motion, particle counters to measure particle dispersion (particle concentration and number) were placed at 20 m and 30 m from the explosion center. It was observed that a soil volume of 20.7 m3 attenuated the peak pressure by 95%, positive impulse by 98% and positive impulse duration by 68%, compared to the values for an equivalent surface detonation computed from literature data. The plume area increased linearly with time for 1 second. The increase in particle concentration and number lasted for about 7 minutes. The explosion led to 800% and 200% increase in particle number for particle counters placed at 20 m and 30 m respectively. Over 10 m (distance between the two counters) and for 1.3 minutes duration, particle number decreased by 95%, particle concentrations PM10 decreased by 90%, PM2.5 by 81% and PM1 by 59%. Despite the efforts done to record and analyze data around full-scale explosions, it was concluded that to be able to make statistically sound conclusions, more experiments need to be carried out by varying the explosive charge mass, under different environmental and soil conditions.