Blast Loading of Small Buried Arches

Experiments that define the general behavior of a 30-in. span thin metal arch buried in 50 tons of dry sand and subjected to plane-wave blast loading are described. Time-variation and space-variation of deflection, thrust, and moment are given. An attempt to measure interface pressures was largely unsuccessful, although it was found that the pressure rise time at the crown interface was approximately 6 millisec which is much longer than expected. Repeated loading of a given soil-structure system showed that the deflections from the first loading in a series were much greater than for subsequent loadings at the same overpressure. Under long-duration loads, recovery from the maximum displacement was only about 15% of the total deflection. An effort was made to get a first approximation to the variation of arching with time. Approximately 40% of the surface load was found to be carried by arching after the dynamic response had damped out.