Environmental Engineering Reference
In-Depth Information
Here, P
0
is the air pressure without disturbance; P
1
is the pressure of air shock
wave fronts; P
x
is the interface pressure of detonation products and air.
The pressure of detonation products drops rapidly in the expansion process.
When P
P
k
cm
2
the detonation products of general explosives in
their initial expansion follow the rule of P ¼ A
q
2
;
000 kg
=
;
3
The pressure changes following
the cubic density. The density of detonation products reduces rapidly following the
radius increase. If the packing geometry of explosives is spherical,
:
q /
r
3
;
hence,
P
/
r
9
When the radius of detonation products increases up 1 time, the pressure drops
1
2
9
1
to
500
.
The limiting volume of detonation products is the volume of products when their
pressure drops to the pressure of surrounding media. The volume of detonation
products may be roughly estimated using the below method. When the pressure of
detonation products P
\
P
k
;
k
the expansion process follows the rule of P ¼ A
q
(here, k ¼
4).
The volume of detonation products is V
L
at pressure P
0
.
1
:
2
1
:
P
0
V
L
¼ P
k
V
k
¼CCis a constant
ð
Þ
1
=
3
1
=
3
V
L
V
0
¼
V
k
V
0
V
L
V
k
¼
P
2
P
k
P
k
P
0
ð
2
:
63
Þ
Here, P
2
is the initial average pressure of detonation production.
If P
2
¼
cm
2
cm
2
cm
2
100
;
000 kg
=
;
P
0
¼
1kg
=
;
P
k
¼
2
;
000 kg
=
;
5
V
V
0
¼
when k ¼
7
=
50
1
=
3
2000
5
=
7
¼
800;
V
L
50
1
=
3
2000
4
=
5
when k ¼
:
For most of explosives, the volumes of detonation products which expand to
pressure P
0
is about 800
5
=
4
;
V
0
¼
¼
1600
1,600 times of their original volumes. If the limit volume
of detonation products is known, the limit impact distance can be calculated. The
geometry of explosives is assumed to be a sphere, so
-
3
1
=
3
V
L
V
0
¼
r
L
r
0
V
L
V
0
or
r
L
¼ r
0
ð
2
:
64
Þ
Here, V
L
is the limit volume of detonation products; V
0
is the volume of
explosive sphere; r
L
is the limit radius of detonation products; r
0
is the radius of
explosive sphere.
Most of experiments show that the volume of detonation products from liquid
explosives is about 20
60 % larger than that of condensed explosives. Under
standard condition, the expansion ratio is 920
-
1,600. For a spherical 1 kg liquid
explosive with density 1.58 g/cm
3
, the r
L
is calculated below.
-
