Asymmetric Collapse of LOS Pipe-LS-4

摘要

This report summarizes the results of a single laboratory experiment (LS-4) that was performed to further evaluate the feasibility of using asymmetries to suppress jetting in line-of-sight (LOS) pipes collapsed by the ground shock from an underground nuclear test. Underground conditions were simulated by using a sphere of high explosive to collapse twenty-six small-scale models embedded in saturated sand. Thin-walled, straight, stainless steel tubes were used to model LOS pipes. Models with no further alterations were called standard models. Other models contained some form of asymmetry added to the tube to alter the pipe collapse and jet formation process or to attenuate the jet after it is formed. The results of the experiment show that high-energy jetting of standard models always occurs, is enhanced by increasing the areal density of the pipe wall, and is unaffected by the presence of air in the pipe. Jet energy decreases with the pipe standoff relative to the surface of the high explosive sphere. The use of helical or ring asymmetries was effective in attenuating the jet in all cases where the asymmetry was loosely attached to the inner wall of the Pipe, even when it was positioned beyond the jet forming region of the pipe. Very little jet attenuation was observed when a ring or helical asymmetry was located entirely within an expansion chamber.