Basic HTML Version
www.geotechnicalnews.com
Geotechnical News • June 2013
27
GEOTECHNICAL INSTRUMENTATION NEWS
some European countries, and fiber
optic is merely a newer technology
for temperature measurements with
the added advantage of distributed
measurements. Inaudi gave a number
of examples of strain measurement
especially for dam and levee slope
deformation monitoring and showed
how the hardware has improved
recently. Among these improvements
are fiber optic cables designed espe-
cially for buried applications as well
as improved software.
Four presenters described several geo-
physical techniques that can be used
for dam monitoring. Gordon Anderlini
of BC Hydro uses crosshole seismic
shear wave tomography to character-
ize and confirm the remediation of a
past sinkhole. Continued monitoring
of the sinkhole repairs and embank-
ment dam is done using the simplified
common elevation method which
has proven to be very repeatable. By
monitoring changes in patterns of
seismic wave velocity between bore-
holes, Anderlini monitors changes in
void ratio and/or stress with time and
expects to get early warning of future
sinkhole or internal erosion develop-
ment.
Phil Sirles of Zonge International, a
geophysics company, described how
traditional geophysical methods,
especially seismic, resistivity and
self-potential are used beneficially for
assessment of internal erosion, seep-
age mapping and soil composition in
dam embankments and foundations.
He also discussed a project that is
underway deploying wireless solar-
powered self-potential and resistivity
instrumentation for early detection
of seepage and internal erosion using
buried electrodes and passive sen-
sors, thereby enabling “4D” monitor-
ing, i.e., geophysical measurements
through time.
William Doll of Battelle presented the
background and the current status of
an airborne electromagnetic survey
system using a low-flying helicopter.
This system was tested on a levee
segment and showed good correlation
with areas that are dominated by clays
or sands as well as known sand boil
locations.
Yogi Sookhu of Gotham Analytics
talked about extensive data communi-
cation systems being used to transmit
multiple streams of monitoring data
along robust paths. One data stream he
focused on is from long-wave infrared
cameras that may be used to measure
wet surfaces and provide notification
in the event of sudden enlargement of
wet areas.
There were four presentations focused
on topics of “traditional” instrumenta-
tion. Jay Stateler of the US Bureau of
Reclamation talked about anomalous
readings and the process by which
an anomalous reading is turned into
an interpretation of how the dam is
performing. Jim Hummert of URS
showed results from DamSmart and
related products that focus on help-
ing the user manage and graph data.
Pierre Choquet of RST Instruments
and Christopher Hill of Metropolitan
Water District of Southern Califor-
nia presented information about the
progress of data acquisition systems
focusing on changes in communica-
tion topology and energy usage. These
improvements are gradually making
automatic data acquisition systems
more and more practical for users.
Finally, in this section, Erik Mikkelsen
of GeoMetron made a case for the
value of fully-grouted piezometers and
described how to install them for best
effect.
The final section of the workshop
was on deformation measurement.
A rail-mounted system for accu-
rate horizontal measurements using
terrestrial inSar was presented by
Larry Olson, of Olson Engineer-
ing. Pieter Bas Leezenbeg of Hansje
Brinker, although unable to attend
the workshop because of last minute
commitments, had prepared slides
on satellite-based InSAR applied
to deformation monitoring of dams
with millimeter accuracy. A 3-D
laser scanning system being used for
dam deformation measurements by
the Metropolitan Water District was
shown by Julio Castillo of MWD.
Finally, Craig Hewes of Leica made
a presentation on using differential
GPS and total stations for deformation
monitoring.
An abstract of the 14 presentations
can be downloaded from the follow-
ing link: http://mail.rstinstruments.
com/DOWNLOADS/USSD2013.pdf .
The email address of each presenter is
included in the document for anyone
who would be interested to obtain
their PowerPoint presentation.
Additionally, a slightly modified
program based on this workshop will
be facilitated at the 81
st
Annual Meet-
ing of ICOLD (International Com-
mission on Large Dams) in Seattle,
WA on August 16, 2014 (http://www.
icold2013.org/workshops.html)
Christopher J. Hill
Team Manager, Safety of Dams
Team, Metropolitan Water District
of Southern California, P.O. Box
54153, Los Angeles, CA 90054,
U.S.A. 213-217-7969, chill@
mwdh2o.com
Pierre Choquet
Vice-President of Sales, RST Instru-
ments Ltd., 11545 Kingston Street,
Maple Ridge, BC, Canada, 604-540-
1100, pchoquet@rstinstruments.com