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Geotechnical News • December 2012
43
THE GROUT LINE
Use of the real time monitoring for micropile/
anchor testing and stressing
Paolo Gazzarrini P.Eng.
Abstract
The use of computers and real time
monitoring in the grouting industry
has become very popular, useful
and nearly mandatory in the last two
decades. Can we say the same for the
micropile/anchor industry?
This paper will describe some pre-
liminary tests carried out in micropile/
anchor projects in Vancouver, Canada,
with the use of commercially available
instruments, recording in real time the
testing and stressing of the micropiles/
anchors. The system used allows
recording and printing in real time the
behaviour of the micropiles/anchors,
to automatically create movement/load
graphs in performance tests, creep
tests and proof tests.
In the tests that were carried out the
system proved reliable, indicating a
great opportunity for the micropile/
anchor industry to increase its level of
quality control and quality assurance.
Introduction
Testing of micropiles (tension/com-
pression/lateral) and anchors (tension)
follow very strict standards and accep-
tance criteria. Literature for testing is
available, for example, in:
• FHWAMicropile Manual
• FHWA Ground Anchors and An-
chored Systems
• PTI Recommendations
• Eurocode 7
This paper does not analyze/discuss
the different kinds of tests (ultimate,
verification, proof or creep) or the
acceptance criteria, but only the appa-
ratus used and results obtained in a
couple of preliminary tests carried out
in Vancouver.
Conventional testing
What is used generally for micropile/
anchor testing?
• Hydraulic jacks,
• Dial Gauges,
• Load cells (sometimes),
• Reaction anchors/ frames for com-
pression test.
What is the difference between a load
test done in 1947 (see picture #1 ) and
a test done today?
The same, or similar, dial gauges,
same hydraulic jack, sometime today
also with a hand pump, a shiny steel
beam (I doubt today!), shine and
elaborated reaction anchors. Not much
difference today, 65 years later! The
only notable difference from today
is, definitely, the approach to safety
(please note the picture), much dirtier
shoes and a slightly different fashion
on site!
Monitoring of the testing in real
time
So, what can be done today to increase
the level of QA/QC in testing micro-
piles and anchors?
The use of computers and real time
monitoring in the drilling and grout-
ing industry has become very popular,
useful and nearly mandatory in the last
two decades. Electronic instruments
are now available on the market that
allow the monitoring, recording and
plotting of tension/compression tests
in micropiles/anchors in real time.
The apparatus used for the test in Van-
couver is composed of:
• Main recording unit with printer,
keyboard and electrical junction
box. See picture #2.
Picture 1. Compression test done in 1947 at Campione d’Italia (Lugano
Lake).