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Geotechnical News • June 2012
THE GROUT LINE
emergency remediation of a bridge
pier in deep water, subject to tidal
variation, founded on a concrete filled
timber caisson of unknown strength,
condition, or exact dimension. The
suspected “faulty” soil was at a depth
of 160 to 170 feet, underlying a deposit
of organic clay and silt mud approxi-
mately 100 feet thick. The soil was
variable, consisting of a range of sands,
some silt, and even some minor clay.
Sampling and sample retrieval were
time consuming and very difficult to
accomplish, and the soils were not well
understood when the grout injection
began. Because of the emergency con-
ditions, grouting was actually started
boring and installation of instrumen-
tation systems progressed, such that
primary guidance for the work was
through analysis of the ongoing injec-
tion as it progressed. Similar to the
California Aqueduct, monitoring data
was uploaded into Excel for analysis to
guide the ongoing injections. Further,
the remediation team members were
literally scattered across the country.
Many teleconferences were held dur-
ing which the team members could
observe and discuss the original data,
transmitted via an FTP site.
The above examples illustrate that
“unusual events” can be investigated
by exporting data to Excel for cross-
plotting (correlating), expanding
scales and so forth – data processing
features omitted in current “proprie-
tary” software. However, once the data
is in Excel we can go one step further
to understand what is happening in the
ground.
Understanding through analysis
Excel has a programming language
“VBA” that is readily accessed from
the worksheets (see the ‘Macro’
menu). Grouting data can be imported
and plotted in Excel, with all the plots
found in the real-time monitoring
systems easily replicated, but with
now the possibility of adding formal
analysis through VBA. This is easiest
appreciated by example.
For remediation of Bennett Dam by
compaction grouting, grout injec-
tion was simulated in finite element
software to develop a set of response
‘type curves’ that were transferred to a
VBA routine. These curves could then
be called up from within a worksheet
to overlay a simulation on the mea-
sured data in an “image matching”
process, with the ground parameters
adjusted to get the best-fit; those best-
fit parameters show the current state of
the ground. In effect, each compaction
grout injection was treated as if it were
a pressuremeter test with the evolution
of the estimated ground parameters
directly showing how the effectiveness
of the work was developing.
The process of modeling grouting has
now been extended to fractured rock
grouting. The Bingham equations for
flow in rough fractures can be solved
directly in VBA. Just like compaction
grouting, fracture roughness properties
estimated from for example televiewer
data,and then adjusted to best-fit the
Bingham solution on the measured
penetrability versus injected volume
curve – giving a measure of how far
the grout penetrated into the formation
in that stage.
These two examples show the
potential power of getting computer-
acquired grouting data into Excel.
They also illustrate two independent
functions for grouting data: i) job-
control in real-time situation – that
is, activities around Principle 1; and,
ii) protocol-assessment within hours
of an injection – that is, activity in
support of Principle 2. Whether this
Principle 2 assessment is done by an
onsite grouting engineer, an offsite
support engineer, or by the Owner’s
appointed review engineer, does not
matter – it is a distinct function with
different purpose from day to day job
control. And, today, Principle 2 needs
data that can be loaded into analytical
software such as Excel.
Of course these two cases of analysis-
guided grouting do not represent the
current state of practice. But, they do
show where the industry might go,
and how we can further improve and
expand our technology.
Required computer-based data
acquisition
Data in support of grouting covers a
wide range of drilling and grouting
activities, and all the data is needed to
guide the work. However, the ‘ruckus’
Grout Computers.
