Geotechnical News June 2011
37
THE GROUTLINE
consultants are using them on smaller,
non-Federal projects.
However, the author has noted over
the past few years a distinctly retro-
gressive faction in the grouting indus-
try which, if left unchallenged, will
undo much of the advantages gained
over the last decade. Examples in-
clude a reversion to the use of highly
unstable HMG’s as engineers confuse
“thin” and high water content. Perhaps
more concerning is the re-emergence
in certain circles of the thirty-year-old
GIN Method (Grouting Intensity Num-
ber). This method was devised with the
laudable goal of trying to assure a cer-
tain basic standard of care in grouting
projects in countries of a lesser degree
of resource and sophistication.
In this paper, the author urges
against the regression in U.S. grouting
practice, which is in danger of occur-
ring due to a relapse into old, unsatis-
factory habits, and a “rediscovery” of
outdated and inappropriate methodolo-
gies. The U.S. grouting industry today
is ranked amongst the most active and
effective in the world, and this level
of approbation should be guarded and
cultivated, not let slide.
Introduction
Rock grouting for dam foundations
has been carried out in the U.S. since
at least 1893 when the limestone
bedrock of a dam in the New Croton
Project, NY, was treated with cement
grout (Franklin and Dusseault, 1989).
Opinions differ on the method of
injections (Glossop, 1961, Littlejohn ,
2003), although other reports (Verfel,
1989) strongly suggest that U.S.
grouting procedures had made “a good
start.”
For the best part of the following
hundred years, the intense history of
dam grouting in the U.S. is, to some
extent, a picture of objectives not fully
achieved, innovative procedures and
insightful ideas inconsistently imple-
mented, and a number of questionable
practices unthinkingly perpetuated.
During the last 15 years, however, in
many—but not all —parts of our prac-
tice, there has been a radical change in
our concepts and in our approaches
to such work. Partly drawing from
knowledge made available in the U.S.
by European specialists, for example
at the seminal grouting conferences
hosted in New Orleans in 1982, 1992
and 2003, and partly by the very chal-
lenging problems posed by the need to
construct remedial grout curtains in our
own dams, especially on karst, there
has been a technological revolution in
dam grouting practices in the U.S. This
revolution has greatly benefited the
owners of these dams, and dams them-
selves, and — by association — the
grouting profession at large.
However, the proven advantages
and successes of this uniquely tailored
advance have not yet everywhere been
recognized, and have not always been
upheld and consistently defended. We
therefore find that in some regions, or
in certain organizations — or most sad-
ly in certain sections of certain organi-
zations — rock grouting is still being
specified in the terms of 50 years ago.
Equally, there are increasing numbers
of projects being specified and run ac-
cording to “new concepts” which, in
reality, are new only to the designers
and represent a retrogressive step of
almost 30 years.
In the following sections, the old,
the new and the retrogressive concepts
of rock fissure grouting are presented
to provide a platform for logically
arguing against the old and the retro-
gressive ways of approaching work
of this type. Given the relatively high
volume of dam grouting — especially
for remedial applications — being con-
ducted today, we have now arrived at a
particularly important time to have this
debate.
Historical Concepts (“The Old”)
There is a trove of published
information to be found on this subject,
including the Proceedings from the
New Orleans Grouting Conference
in 1982, the “Foundations for Dams”
Conference (1974) and textbooks by
Houlsby (1990), and Weaver (1991)
in particular. Even more important are
the unpublished reports, memoranda
and manuals produced on a project-
specific basis, or by companies or
governmental organizations. These
had special gravitas because their
authors strongly influenced the next
generation of grouting engineers while
they, themselves, were elevated to
the position of “consultants” on other
projects in different governances.
Bearing in mind the unprecedented
level of activity in those years in new
dam grouting, as well as the national
puritanism towards “low bid” con-
tracting, specifications were highly
prescriptive and restrictive. Such pre-
scriptions did nothing to stimulate
innovation since the contractor was
reduced to the status of the cheapest
purveyor of labor, equipment and ma-
terials, while the goal of the owners’
inspectors was to ensure that the speci-
fications were enforced to the letter, via
“hole by hole” direction of the grouting
activities.
By the way of illustration, in 1974,
Polatty was invited to give an overview
of U.S. Dam Grouting Practices: “In
preparing this paper, I requested copies
of current specifications for foundation
grouting from several Corps of Engi-
neers districts, the TVA and the Bureau
of Reclamation. In comparing these
current specifications with copies of
specifications that I had in my file that
are 30 years old, plus my observations
and experience, I concluded that we
in the United States have not, in gen-
eral, changed any of our approaches
on grouting. AND THIS IS GOOD”
(emphasis added). Interestingly, he
then went on to list “difficulty in hav-
ing sufficient flexibility in the field to
make necessary changes to ensure a
good grouting job” as a problem. What
a surprise!
As a consequence, several impor-
tant historical paradigms became em-
bedded in our national practice as late
as the 1980’s. These include:
• The drilling of vertical holes, to a
target depth (as opposed to strati-
graphic horizon). The only com-
mon exception (e.g., Albritton,
1982) would be the concept of in-
clining the curtain upstream, so as
to physically distance it from the
downstream drains.
• The use of rotary drilling (often just
coring) since in the early days of
the 20th century since only such
drills could use water flush. Percus-
