Geotechnical News • March 2016
33
GEOTECHNICAL INSTRUMENTATION NEWS
The following points were made in the
introduction to Part 1, and also apply
here:
• Of course it is recognized that
there may be additional geotechni-
cal questions and also additional
instruments that are not described
in this article.
• The sequence of geotechnical
questions is intended to match
the time sequence in which the
question may be addressed dur-
ing the design, construction, and
performance process, and does not
indicate any rating of importance.
• The suggestions for types of
instruments is not intended to be
dogmatic, because the selection
always depends on issues specific
to each project, and is influenced
by the personal experience of the
person making the selection. In
the tables some of the most likely
instruments that can be considered
are listed, with other possible types
in parentheses.
• The tables include the term “remote
methods” for monitoring displace-
ment. An overview of these remote
methods is given in a December
2012 GIN article by Paolo Maz-
zanti
.
com/instrumentation_news.php).
Readers who want to learn more
about these methods may want to
consider participating in the annual
International Course on Geotech-
nical and Structural Monitoring
held in Italy (
-
calmonitoring.com), where they
are discussed in detail.
Embankments on soft ground
General role of instrumentation
This article relates to the use of geo-
technical instrumentation where all the
geotechnical questions are associated
with the soft ground itself, and not
with the embankment.
In many cases, selection of soil param-
eters for the foundation soil is reliably
conservative. The embankment is
therefore designed with confidence
that performance will be satisfactory,
and “comfortable” factors of safety are
used. In such cases, many projects will
proceed without the use of instrumen-
tation. However, some uncertainties
always exist. Where design uncertain-
ties are great, factors of safety small,
or the consequences of poor perfor-
mance severe, a prudent designer will
include a performance monitoring
programme in the design.
Table 3. Some instruments that can be considered for monitoring embankments on soft ground
Possible geotechnical questions
Measurement
Some instruments that can be
considered
What are the initial site conditions
in the soft ground?
Pore water pressure
Vertical deformation
Vibrating wire piezometers installed
by the fully-grouted method
(Open standpipe piezometers)
(Pneumatic piezometers)
Conventional surveying methods
Remote methods
Is the embankment stable?
Horizontal deformation
Conventional surveying methods
Remote methods
Inclinometers
(In-place inclinometers)
What is the progress of consolidation
of the soft ground?
Vertical deformation of embankment
surface and ground surface at and
beyond toe of embankment
Vertical deformation of original ground
surface below embankment
Vertical deformation and
compression of subsurface
Pore water pressure
Conventional surveying methods
Remote methods
Probe extensometers
(Single-point and full-profile liquid
level gauges)
(Settlement platforms)
(Horizontal inclinometers)
Probe extensometers
Vibrating wire piezometers installed by
the push-in method
