SECONDARY PRESSURE WAVES 



389 



measured peak pressures, corrected to a gauge distance of sixty feet 

 assuming a distance variation as 1/r, are plotted in Fig. 9.9. The 

 values plotted include the effects of surface and bottom reflections, 

 which account in large part for the large pressures near the bottom. 

 When corrections are made for these reflections, this effect largely dis- 



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DEPTH (ft) 



Fig. 9.10 Observed positive impulse 60 feet from 300 pound TNT charges 

 fired in 100 feet of water. 



appears, as shown in Fig. 9.11. This curve was constructed from 

 records of the gauge fifty feet deep, for which the corrections were least. 

 For comparison, the peak pressure curve predicted by the theory of 

 Shiffman and Friedman is plotted. The sharp maximum predicted for 

 a loAver rest position is not realized, the data showing instead a gradual 

 falling off of peak pressure as the charge is placed closer to the bottom. 

 As for small charges, an anomalous pulse is observed, in this case 



