SEISMIC CHARACTERISTICS OF CAVITY DECOUPLED EXPLOSIONS IN LIMESTONE -AN ANALYSIS OF SOVIET HIGH EXPLOSIVE TEST DATA

During the summer of 1960, Soviet scientists conducted a series of hig h-explosive, cavity decoupling tests in a mine in Kirghizia. These dec oupled tests were carried out in a variety of mined cavities in limest one, including spherical cavities with diameters ranging from 3.5 to 1 0 m as well as nonspherical cavities with volumes of about 25 m(3). Th e experiments of this test series consisted of 10 tamped and 12 decoup led explosions having yields of 0.1, 1.0, and 6.0 t, and seismic data were recorded at locations in the mine over a distance range extending from about 10 to 250 m from the sources. These data provide valuable new insight into the dependence of decoupling effectiveness on variabl es such as cavity volume, cavity shape, and charge emplacement geometr y. In particular, analyses indicate that chemical explosions at a dept h of 290 m in limestone are essentially fully decoupled in spherical c avities with scaled cavity radii larger than about 27 m/kt(1/3) and th at the low-frequency decoupling effectiveness under such conditions is approximately independent of cavity shape for roughly cylindrical cav ities with length-to-width ratios of as much as 6-12. These results su ggest that the possibility of cavity decoupling in nonspherical caviti es in hard rock media will have to be carefully evaluated in establish ing the seismic verification regime for the Comprehensive Test Ban Tre aty.