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where the explosive source function, S(t-t d ), and distance between
explosion and recorder, r metres, are given by:
(2.2)
r = (2.3)
d s and d r are the explosive source and the sensor depth respectively, x
their horizontal separation. H is the Heaviside step function. td is the
shock wave arrival time, assumed to be given approximately by td = ric, c
being the speed of sound in water. The maximum pressure, P (r), and time
m
constant, e(r) ms, depend on the type of explosive used but are of
general similitude form given by Britt's (1984), equations:
P (r) = K (V 1/3 /r)a,
m p
(2.4)
e(r) = Ke V1/3(V1/3/r)b. (2.5)
v kg is charge weight and values for the constants adopted in (2.4) and
(2.5) are those for TNT, viz:
K 52.4, a = 1.13;
p
Ke 0.084, b = -0.23.
Integrating equation (2.1) over time gives the impulse, I(r) MPa-ms:
(2.6)
I(r) (2.7)
with constants:
KI = 5.75, c 0.89. (2.8)
These constants are for integration carried to 50(r) ms after the main
pressure wave.
The preceding discussion closely follows Britt (1984) where further
details can be found. Forecasts of the maximum pressure and impulse for
both the direct wave and the surface reflected wave as a function of
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