from the hundreds of blows necessary to drive a single pile
potentially exacerbates damage due to fatigue effects.
Figure 1 shows a typical plot of the levels of particle velocity
required to produce structural damage at a frequency of 10
Hz. Also shows are the measured peak vibration levels from
various construction activities as a function of distance away
from the vibration source. The measured data show how the
particle velocity decreases rapidly with distance from the
source. Figure 1 shows that if one is more than 15 feet away
from the vibration source for typical pile driving, the vibration
level is below that which may damage a structure. The
available data and experience show that unless pile driving is
occurring within a few feet of a structure, it doesn’t not cause
damage to the structure from vibrations. (There may be other
undesirable effects such as vibration induced ground settlement
or disruptions to very sensitive equipment, but these
FEATURE
are special cases.) The contents of Figure 1 are well known to
the geotechnical engineering profession and many pile driving
contractors.
So why do people complain about pile driving and resists
its use? Figure 1 holds a significant part of the answer. Figure
1 also shows criteria on the sensitivity of people to vibrations.
People can typically perceive vibrations above 0.01 in/
sec – one-hundredth the level at which structural damage
might occur. This can become troublesome to some people.
They can feel and become concerned about vibrations that
are only a tiny fraction of those that might begin to cause
damage to structures. People complain about pile driving
effects because they are much more sensitive to vibrations
than buildings are. They tend to extrapolate their personal
sensitivity to vibrations to a concern about the safety of their
building.
CONTINUED ON PAGE 45
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