Measurements and calculations of peak shock-wave parameters from underground nuclear detonations

Instruments which measure peak shock pressures and shock positions from underground nuclear explosions have been developed, and results have been obtained from 33 detonations in alluvium, 3 in tuff, and 2 in granite. The measurement techniques in the high-pressure region have been so refined that the probability of obtaining meaningful data from any experiment is high. In a parallel effort, a computer calculation has been produced by means of which, once the necessary dynamic material properties are known, shock-wave parameters can be calculated as a function of time and a single space variable. For tuff and granite, the difference between most measured peak pressures and calculated values is less than 20%, with poorer agreement in the case of alluvium. Most calculated shock positions agree with measurements to within a fraction of a meter. At least half of the disagreement is due to uncertainty in relating raw data to values in the medium, caused primarily by our poor knowledge of the Hugoniots of earth and rock materials and the instrument coupling grout. Large inhomogeneities in the medium near instruments is the most likely explanation for those measurements which disagree by more than 20% with calculated values.