Environmental Engineering Reference
In-Depth Information
Fig. 2.36 Phenomena of loose blasting [
21
]. 1 inside cracking zone; 2 out cracking zone
waves pass through, the particles of media move out radially, and stop by the outer
layer media. But if there are ground surfaces or other free surfaces, the rocks and
soils of the free surfaces are not stopped by the outer layer media, and move out
radially. At the same time, the explosion waves become tensile waves from free
surfaces with transportation velocity of sound (Fig.
2.36
a).
Wherever the radiant waves reaches, the rocks and soils are under drawing
extension. If the drawing tension is larger than the limit of ultimate tensile strength,
the free surfaces expand inside layer by layer. Re
ected extension waves are
approximately spherical waves from optical mirror virtual center O
′
of explosives.
The damage of loose boosting has two parts.
fl
(1) Part 1 is inside cracking zone (Fig.
2.36
b), which is a spherical zone with
radial cracks, and with
fine medium particles.
(2) Part 2 is out cracking zone, which is produced by the damage of tensile waves
from free surfaces. The key feature of this zone is that the cracks expand along
the spheres of virtual centers with relatively larger medium particles. The
shape of this zone looks like a funnel. So this zone is also named as loose
funnel.
Fig. 2.37 Three different phenomena in the throwing blasting [
21
]. a A throwing blasting cone,
b the bulging motion in a throwing blasting, c an explosion cone
