The effect of plasticity on decoupling of underground explosions.

A study of the effect of plasticity, including work hardening, on decoupling underground explosions for cavities designed to give full decoupling according to the Geneva specification (70 cubic meters per ton of explosive energy) as well as small (overdriven) cavities designed to give partial de- coupling. The results show that plasticity plays no role whatsoever for full-decoupling cavities, even those at great depth in which some plastic flow occurs during construction of the cavity. For overdriven cavities at great depth, plasticity affects the decoupling factor by an amount which depends on the degree of overdriving and the depth as well as the detailed stress-strain curve of the medium. For cavities at a depth of about one kilometer and in a medium like salt, which exhibits a reasonable amount of work hardening, the decoupling factor will be at least as great as that obtained in the overdriven Cowboy experiments and could be appreciably greater.