and Response of Tourmaline Gages for Measurement

direct wave can be estimated from the graph shown

of Underwater Explosion Phenomena," NSWC

in Figure 3 (Cole 1948), in which the abscissa is in

units of "scaled" range (*R/W*1/3), where *R *is in feet

TR-82-294, Naval Surface Weapons Center, White

Oak, MD.

and *W *is the explosive weight in pounds. The water

shock impulse (time integral of the pressure history)

for the direct wave from a TNT explosive source can

be estimated from the graph shown in Figure 4. The

ordinate in Figure 4 is in units of "scaled" impulse

(*I/W*1/3), where *I *is in pounds per square inch-

detonation of high explosives travels at a speed of

seconds. Table 1 provides approximate conversion

about 5,000 ft/sec for pressure levels less than

factors for converting several common explosives to

30,000 psi (Cole 1948). In shallow water, the distur-

an equivalent weight of TNT. If the actual value of

bance is characterized by the arrival of four principal

the equivalency factor is unknown, an upper estimate

waves (see Figure 1): (1) an exponentially-decaying,

value of 2.0 will cover most common explosives (i.e.,

direct wave from the explosive source, (2) a surface-

1 lb of explosive is equivalent to no more than 2 lb

relief wave (tensile image of the direct wave), (3) a

of TNT).

bottom-reflected wave, and (4) a wave transmitted

through the bottom materials and radiated back into

the water (Miller, Strange, and Pinkston 1971). The

pressure (in pounds per square inch), as a function of

effect of these different waves on the resultant pres-

time (*t*, in sec), for the direct wave is described in

sure history is shown schematically in Figure 2. The

Cole (1948) as:

resultant pressure-time history is the time-phased

superpositioning of the direct, surface relief, reflected,

(1)

and refracted pressure waves at a point.

θ

and bottom are far removed from the explosion

Where *P*m, the peak pressure (in psi) is

source and measuring locations, the direct wave is the

predominant factor.

21,600(λ)

(2)

1.13

2

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