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ETL 1110-8-11(FR)
15 Jul 91
Table 1
Approximate TNT Conversion Factors for Selected High Explosive
Approximate Conversion Factor
Explosive
by Weight for Pressure
TNT
1
1.11
Nitromethane
1.042
Pentolite
0.3-0.823
ANFO
1.374
C-4
0.7-0.94
Ammonia Dynamite
0.7-0.84
Gelatin Dynamite
0.94
Nitroglycerin Dynamite
1
Hendry and Welch (to be published 1991).
2
Cole (1948).
3
Dependent on percent fuel oil; factors estimated based on energy content taken from Petes, Miller, and McMullan (1983).
4
Estimate based on airblast data and energy content (Swisdak 1975).
θ, a time constant (in sec), is
f. Approximate upper bound estimates for the
peak pressures and impulses generated by the pres-
(3)
ence of all four of these wave components is shown
θ
W 1/3(λ)0.18
5
6.0 10
in Figures 3 and 4. Upper bound limits of pressure
and impulse can also be approximated by multiplying
the value obtained from Equation 2 by 2.0, and that
ta, the shock arrival time (in sec) at the point of
obtained from Equation 4 by 2.5 (from Miller,
Strange, and Pinkston 1971). Note that, because of
interest, is
the interaction of the direct wave with the surface
relief wave, actual peak pressures and impulses for
ta
R/5,000
shallow-water explosions can be a factor of 10 less
than those given by Equations 2 and 4. Since varia-
and λ is the scaled range (in ft/W1/3), where W is the
tions in water depth can strongly affect the water
shock levels produced, especially at long ranges from
explosive weight (TNT equivalent (in lb)).
a detonation, it is important to monitor the actual
The water shock impulse at a scaled range of λ is
pressure and impulses generated by the explosive
activities.
(4)
1.46 W 1/3(λ)
0.89
I(t)
g. Significant secondary pressure pulsations can
be caused by the rapid, repeated collapse and expan-
sion of the explosion gas bubble in deep water. The
e. The effect of the relief wave on the direct
peak pressures produced by these pulsations are less
signal will be to shorten abruptly the duration of the
than 20 percent of the direct pulse. However,
pressure history seen at the point of interest. The
because the pulsations are of much longer duration,
effect of the bottom-reflected and bottom-transmitted
their associated impulse can be a factor of 4 larger
waves, for most bottom materials, will be to increase
than the impulse associated with the direct wave
the pressure history duration.
(Cole 1948).
4
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