Page 270 - Civil Engineering Formulas

204 CHAPTER EIGHT

Inadequate stemming
of mudseam

Surface detonation Mudseam

Long free face

FIGURE 8.3 Three causes of air blast. (Hemphill-Blasting
operations, McGraw-Hill.)

Vibration Control in Blasting*
Vibrations caused by blasting are propagated with a velocity V, ft/s; frequency
f, Hz; and wavelength L, ft, related by
V
L (8.69)
f
Velocity v, in/s, of the particles disturbed by the vibrations depends on the
amplitude of the vibrations A, in
v 2
fA (8.70)
If the velocity v at a distance D from the explosion is known, the velocity v at
2
1
1
a distance D from the explosion may be estimated from
2
v 2 v 1 1.5 (8.71)
D 1
D 2
*Merritt—Standard Handbook of Civil Engineering, McGraw-Hill.