Measurements and Calculations of Shock Propagation in Dry Desert Alluvium

摘要

A recent underground nuclear detonation in alluvium utilized a large diameter device emplacement hole and the entire instrumentation array was installed in the backfill material. No significant spall or surface reflections were noted in the data obtained in this large cased hole and the shock structure was clearly detailed to locations close to the surface. Several smaller conventional high explosive detonations located closer to the surface have also been studied in detail. In these instances several satellite instrumentation holes were available and measurements were made at or near the detonation horizon minimizing surface effects. Data from two explosive detonations and the data from the nuclear detonation are compared with computer code calculations made to describe underground explosions in alluvium. Supportive data from a plane wave surface detonation are also discussed. Good agreement between the data and the calculation of hydrodynamic shock propagation in dry desert alluvium was observed. The use of the hydrodynamic model appears valid as long as the velocity of the plastic wave is greater than the speed of sound in air. Beyond this point, at pressures of less than 0.4 kilobars, a constant propagation velocity is observed. This seems to indicate that the air contained in this weak porous material is the factor controlling shock propagation. The porosity of the dry alluvium in the four explosions studied was approximately 40%. We have not yet developed a satisfactory physical model for the effects noted. 5 refs., 4 figs. (ERA citation 10:040065)