BLAST OVER VEGETATED AND CLEARED AREAS

Abstract

Abstract : Measurements were made to determine the difference in blast effects over a surface covered with low shrubs and grass and over a cleared sandy surface in the precursor region, and an attempt was made to correlate this difference with measurements of preshock sound speed over the surface. Overpressure was measured with groundbaffle gages and with pitot-static gages at 3-foot elevation. Dynamic pressures were measured at the 3-foot elevation with the pitotstatic gages. Measurements were made at the same ground ranges for vegetated surface as for the sandy surface. The vegetation reduced the severity of the precursor, showing later arrival times and smaller dynamic pressures than over the cleared area. The overpressures over the vegetation were the same at the ground and 3-foot levels. No measurements of sound speed after zero time were obtained, so a correlation is not possible.