Environmental Engineering Reference
In-Depth Information
Here, W is the mass of an explosive; Q
V
is the detonation heat of an explosive;
Q
VTNT
is the detonation heat of TNT (4,180 J/g); W
E
is the TNT equivalent of an
explosive.
(2) Super pressure calculation of shock waves from explosions of liquid
explosives
When spherically packed TNT explodes in free space, the super pressure cal-
culation of shock waves follows the below equations.
2
3
p
3
p
3
p
3
E
R
þ
E
E
D
P ¼
0
:
84
2
:
7
þ
7
R
R
or
0
:
84
R
þ
2
7
R
2
þ
:
7
R
3
D
P ¼
ð
2
:
84
Þ
R
1
10
15
R
¼
p
3
W
is the contrast distance.
If the explosive is on the ground, the energy transferred into the ground is
negligible. All energy is approximately transferred into the hemispherical space.
For an open space, the re
R
ection waves are also negligible. For the explosion on the
ground, W
E
=2W. Substitute this into
2.84
, Eq.
2.85
is obtained.
fl
1
:
06
R
þ
4
3
R
2
þ
:
14
R
3
D
P
E
¼
ð
2
:
85
Þ
Here,
D
P
E
is the super pressure of shock waves when explosion occurs on the
ground.
If the unit of R is meter, and W is kg, all calculated results are basic data for
theoretical shock waves. The relationship of shock wave super pressure and dis-
tance is in Table
2.2
. For all explosives, their explosion heats are TNT equivalents.
The application range of Eq.
2.85
is between 1 and 10
15. When R
\
1, the errors
-
are larger.
The packed geometry of explosives impacts the super pressure of shock waves in
some degree. Probably because in explosion, the transportation forms of detonation
products are impacted by the geometries of explosives. The impaction of packed
geometries is in Table
2.3
.
(3) Calculation of action time and speci
c impulse in the positive pressure area
The action time t
+
in the positive pressure area of liquid explosive explosion is
another parameter of air shock waves, which paly an important role for the damage
of targets. Like the determination of super pressure
D
P, t
+
is an empirical formula
using similar principle and experiments.
