SEISMIC DECOUPLING WITH CHEMICAL AND NUCLEAR-EXPLOSIONS IN SALT

An extensive series of simulations was performed of underground explos ions in salt, using both chemical and nuclear explosives. In both case s, the radius of the initial emplacement cavity was varied from the fu lly tamped configuration to as large as 80 m/kt1/3; when not fully tam ped, the cavity was assumed initially to contain air at ambient temper ature and pressure. In the nuclear source case, the simulations are sh own to be in good agreement with the Salmon/Sterling events conducted by the United States and with recently released Russian data on a simi lar pair of explosions in an Azgir salt dome. Simulation of the U.S. C owboy series of chemical explosions in a Louisiana salt mine are also shown to be in very good agreement with the experimental data; however , the constitutive model for the salt that best explains these data is different from that derived for Salmon; both salt models are amply su pported by laboratory and field data. The main result of these simulat ions is that cavity decoupling with chemical explosives is much less e fficient than with nuclear explosives. Although maximum decoupling fac tors, f(max) near 200 may be attainable with either of the two sources , the cavity size required to achieve this value appears to be >40 m/k t 1/3. For cavity radii half as large, f(max), is roughly 4 times lowe r with nuclear explosives, and lower by another factor of 4 with chemi cal sources. Moreover, if the initial cavity radius is a more modest 1 0 m/kt1/3, f(max) < 3 even with a nuclear source.