Environmental Engineering Reference
In-Depth Information
area; the effect is weak if far away from the explosion center, but the effective area
is larger. For an explosion in the air, if the super pressure of shock waves is 0.2 kg/
cm
2
with total area 100, the area with super pressure >20 kg/cm
2
is only 1.3 %;
20 kg/cm
2
is about 6.7 %. For more than 92 %
while the area with super pressure 2
-
2 kg/cm
2
. Nonetheless, we cannot underestimate the
damage ability of shock waves. When shock waves impact the building in large
area, the super pressure 0.2
area, its super pressure is 0.2
-
2 kg/cm
2
of wave fronts has enough killing capacity for
human and damage for glasses of buildings and buildings with wood
-
brick
structure. In general, the shock waves from liquid explosives are stronger than that
of condensed explosives, so liquid explosives are more damageable. The parameter
change law study of shock waves in the explosion is a must to study the damage
capacity of explosives.
-
(1) Explosion similarity law of air shock waves
The shock wave impacts from same explosives with different masses follow the
geometry similarity law in the space before the shock waves meet the boundaries or
obstacles. For an explosive with packed radius r1, the super pressure of shock wave
front at R1is
D
P; and if the second explosive with r2, the super pressure of shock
wave front at R2is
D
P. These two explosives are similar in geometries of packing.
The geometric similarity rate is of practical importance for the design of engi-
neering. The experiments can be studied with small amount of explosives and
measure all parameters in free
field. The conditions of explosion with large amount
explosives can be calculated/predicted based on the experiments. It helps to reduce
the experiment numbers and lower the cost of experiments.
In all the shock wave parameters, if the super pressure of shock wave front is
known, all other parameters can be calculated according to the relationship of shock
waves. Once the dimension relationship is
fixed, the relationship of shock wave
parameters and explosive packing is reachable.
For the explosion of liquid explosives in air, the fundamental physical quantities,
which in
fl
uenced the pressure of shock wave fronts, are detonation heat Q
v
, packed
density
ˁ
0
of an explosive, packed radius r, distance to explosive
'
s center R, air
pressure P
a
, and its origin density
ˁ
a
. After ignoring the viscosity and thermal
conduction of air, the super pressure of air shock wave is a function of all
parameters (Eq.
2.65
).
D
P ¼ fQ
v
; q
0
;
r
;
R
;
P
a
; q
a
ð
Þ
ð
2
:
65
Þ
If the distance to an explosive
'
is center R is taken as unit to measure the distance,
= 1.0332 kg/cm
2
) to measure the pressure, and air density
air pressure (P
a
10
−
3
g/cm
3
) to measure the density, the distance to an explosive
ˁ
a
= 1.25
×
'
(
s
center, air origin density, and origin pressure are all 1.
