Geotechnical News • June 2012
25
GEOTECHNICAL INSTRUMENTATION NEWS
Acknowledgements
The support provided by the Innova-
tion Committee of Barr Engineering
Company is gratefully acknowledged.
The careful performance of the
laboratory testing by Soil Engineering
Testing of Bloomington, Minnesota,
is greatly appreciated. The ongoing
assistance from Erik Mikkelsen and
John Dunnicliff, with their thoughtful
insights and contributions from the
beginning of our work on the fully-
grouted method has been extremely
helpful. The thorough reviews and
comments on this article by Mr. Jed
Greenwood and Mr. Rob Osborn are
greatly appreciated.
References
Contreras, I.A., Grosser, A.T., Ver-
Strate; R.H., 2008, “The Use of
the Fully-grouted Method for
Piezometer Installation”. Geotech-
nical News, Volume 26, No. 2,
June,
instrumentation_news.php
Contreras, I.A., Grosser, A.T., Ver-
Strate; R.H., 2011, “Practical
Aspects of the Fully-Grouted
Method for Piezometer Installa-
tion”, Proc. Eighth Int. Symp. on
Field Measurements in Geome-
chanics, Berlin, Germany, Sept.
Contreras, I.A. and Solseng; P.B.,
2006, “Slope Instabilities in Lake
Agassiz Clays.” Proc. 54
th
Annual
Geot. Eng. Conf., Univ. of Min-
nesota. pp. 79-93.
Mikkelsen, P.E. and Green, G.E.,
2003; “Piezometers in Fully
Grouted Boreholes.” Proc. Sixth
Int. Symp. on Field Measurements
in Geomechanics, Oslo, Norway,
Sept.
Mikkelsen, P.E., 2002, “Cement-Ben-
tonite Grout Backfill for Borehole
Instruments.” Geotechnical News,
Volume 20, No. 4, December,
instrumentation_news.php
Vaughan, P.R., 1969, “A Note on Seal-
ing Piezometers in Boreholes.”
Géotechnique, Vol. 19, No. 3,
pp. 405-413.
Iván Contreras, Aaron Grosser,
Rich VerStrate
Barr Engineering Co., 4700 West
77
th
Street, Minneapolis, MN. E:
; agrosser@
barr.com;
Editor’s Note
Another option for monitoring where
the predicted vertical compression is
greater than 15 percent is to use the
push-in method of installation. This
entails drilling to about one meter
above the piezometer location, push-
ing the piezometer to its location with
a pipe that will also serve as a grout
pipe, disconnecting the pipe from the
piezometer, grouting the borehole with
bentonite slurry, and withdrawing the
grout pipe. It is better to arrange for
the piezometer cable to emerge from
the grout pipe through a slot at the
bottom of the borehole, rather than
threading it through the grout pipe.
But this allows only one piezometer
per borehole, and again requires a
method for tracking changing eleva-
tions of the piezometers. I used this
method satisfactorily at the test fill
for the new Chek Lap Kok airport in
Hong Kong, where vertical compres-
sion was up to 35 percent.
If anyone
has experience of this issue, or other
ideas, will you please contact me?
