Geotechnical News • June 2016
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GEOTECHNICAL INSTRUMENTATION NEWS
Lessons learned in vibration monitoring
Vincent Le Borgne
Introduction
Vibration monitoring is growing
in popularity as a complement to
geotechnical monitoring because
infrastructure work generates noise
and vibration that can have deleterious
effects on structures and people. To
ensure compliance with local ordi-
nances and to protect sensitive struc-
tures, long-term vibration monitoring
is more and more commonly used.
The relevance of vibration monitoring
was recently brought to the attention
of the readers of Geotechnical Instru-
mentation News (GIN) by Turnbull
in a March 2016 article entitled “The
fundamentals of vibration monitor-
ing - things to consider”. The article
provides an overview of the technical
requirements of vibration monitoring.
Our company has worked on several
major projects in which vibration
monitoring was a key component in
addition to “traditional” geotechnical
monitoring. In each of the projects
detailed in this article, the first and
perhaps most important thing to be
decided was the goal of vibration
monitoring. These goals led to the
choice of the acceptable vibration
limits and the appropriate sensors
and data loggers. Finally, the method
of data collection was determined
according to the requirements of the
client and the technological limitations
of the equipment used. In addition to
giving examples for each of the steps,
we will explain how, despite follow-
ing this basic methodology, unfore-
seen issues and human elements end
up playing key parts in the lessons
learned in vibration monitoring.
Project 1
Technical requirements
In this project, vibration monitoring
was required for the construction of a
tunnel linking a water treatment plant
and Lake Ontario. Vibration had to be
maintained below a certain threshold
for several reasons: to ensure the well-
being of residents; to protect private
buildings and homes; and to protect a
historical building that was identified
as being more prone to vibration-
induced damage. Near the historical
building, peak particle velocity (PPV)
of 2 mm/s at frequency below 100
Hz was chosen as the threshold not to
be crossed. For other buildings, the
threshold was 8 mm/s at less than 4
Hz, 15 mm/s between 4 and 10 Hz and
25 mm/s above 10 Hz. The threshold
is varied as a function of frequency
because low frequency vibration is
much more damaging than high fre-
quency vibration for any given PPV.
Sensors and loggers were thus chosen
according to these requirements.
Stations were installed at eight loca-
tions clustered around shafts and close
to the historical building. The instal-
lation next to the historical building
is shown in Figure 1. The assembled
system is anchored to the concrete
slab, and the old stone and mortar wall
behind can clearly be seen. There are
whiter parts in the wall where the mor-
tar has been repaired before, showing
that this building is indeed weakened
and requires extra caution.
To minimize long-term costs to the cli-
ent, vibration data are uploaded daily,
automatically to the client’s server,
Figure 1. The geophone system and the historical building to be monitored.
