Environmental Engineering Reference
In-Depth Information
(1) Brisance
The ability of direct effect or brisant effect from explosive explosion is the
brisance of explosives, which is another parameter to measure the blast action of
explosives.
The direct effect of explosive explosion is determined by the pressure of deto-
nation products and action time, also the pressure and momentum to the target.
Actions of pressure and momentum are different under various conditions. So the
pressure or momentum of detonation products is used to describe brisance.
(1) The pressure
of products in the ending of detonation reactions
The breaking surrounding media in the detonation of explosives is a result of
strong impact of high-temperature and high-pressure detonation products to the
media. The higher pressure of detonation products, the breaking ability to the
surrounding media is more powerful. So, the brisance of condensed explosives is
expressed in Eq.
2.48
.
ð
P
2
Þ
q
0
D
2
P
2
¼
1
=
4
ð
2
:
48
Þ
The above equation shows that the faster detonation velocity and greater density,
the higher brisance. Liquid explosives are noncompressible; the density cannot be
changed. Their densities and detonation velocities are constants.
For mixed or monomer liquid explosives, D
A
q
0
when the packing density is
1.0
1.7 g/cm
3
. A is the detonation velocity when the density is 1.0 g/cm
3
. Equa-
tion
2.28
is changed to P
2
¼ 1
=
4 A
2
-
0
.
The above equation fully describes that the brisance is linearly proportional to
the cubic of explosive density. Increasing the density of an explosive, raises its
brisance dramatically.
(2) The speci
q
c impulse affecting the target
When the affecting time of detonation products to one target is longer than its
natural period of oscillation, the damage ability for the targeted object is only
determined by the pressure of detonation products. When the affecting time is
shorter than its natural period of oscillation, the damage is determined not only by
the pressure of detonation products, but also the effecting time. The brisance of an
explosive is explained by the momentum, which is related to pressure and time.
The momentum aimed on one target
is the product of affecting force and
affecting time (Eq.
2.49
).
Z
SPd
I ¼
s
ð
2
:
49
Þ
Here, I is the momentum aimed on the target; P is the pressure on the target; S is
the area;
is the affecting time.
The momentum within unit area is the speci
˄
c impulse. If the affecting area of
the target S does not vary in time, Eq.
2.49
is changed to
2.50
.
