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Geotechnical News • December 2013
39
THE GROUT LINE
Paolo Gazzarrini
Overture
33rd episode of the Grout Line. It’s
Christmastime and it’s a good time
for a fairy tale. So here we are; a short
rock grouting fairy tale.
The need to talk (again!) and to write
(again!) about very “basic” concepts
of rock grouting, is once again obvi-
ous after attending few conferences
and reading several grouting specifica-
tions.
“Basic” concepts such as: grout mixes
and grout pressures- let’s leave all the
different grouting theories out, for the
moment.
I realized that still now in 2013 (nearly
2014), I repeat 2013!, some of us
grouters, are still working with old
theories and procedures that I was
hoping had been completely aban-
doned and forgotten. So I am obliged
to insist, insist, insist!
And so begins my short tale.
Of course all of the characters
described in the story are absolutely
real, but the story is totally fictitious.
Any resemblance to real facts and
real persons is purely and accidentally
coincidental!
A Christmas Fairy Tale of Rock
Grouting in a Dam!
Characters:
à
à
The Hopeful Dam
à
à
The Thirsty Rock Mass (Main
character)
à
à
The Self-Conscious Grout
Curtain, Grout Mixes and
Grouting Pressures (All Main
characters, of course)
à
à
The Trusting Owner
à
à
The Happy Engineer
à
à
The Main Contractor and the
Drilling & Grouting Contractor
à
à
The Very Happy Grouting
Consultants
Once upon a time in a faraway land
there was a valley. (
Classic start of a
fairy tale
).
One day, someone decided that it was
a good idea to build there a dam and a
power house to produce energy. (
Up to
here nothing strange
).
The Owner hired an Engineering Firm
and a design was born. Voilá. (
Again
up to this point nothing strange
).
With the design in hand, the Engineer
prepared the Specifications.
“No problem”, thought the Engineer.
“For the concrete we have a lot of
experience. For the rebar the same, as
well as for the earthmoving.”
As for the Rock Grouting? Again: “No
problem”, as the Engineer remem-
bered a job at XYXY Dam. “We can
copy and paste the specifications used
there!” And so it was done. Unfortu-
nately the Engineer had forgotten that
XYXY Dam had been built in 1961,
more than 50 years ago! (
And herein
the problems begin
).
The Specifications were completed,
the Owner found the money, and the
tender was issued with a Main Con-
tractor selected.
The work started to the great satisfac-
tion of everybody.
Now we need to open a parenthesis
and clarify that the Dam location was
in a very remote area of the World
(
quite usual for a Dam
), with very
extreme meteorological conditions.
Consequently the Contractor had a
very short window (6 months) to build
the Dam.
A construction schedule was prepared,
a D & G contractor was chosen, and
the Grouting started immediately.
The schedule allowed two months for
the grouting, with the following four
months for the Dam Construction.
Everything was looking very good!
The Grouting Design called for a
single row (the rock mass was sup-
posed to be fairly good), 10 meters
deep with conventional Primary
holes (with spacing of 5 meters) and
Secondary holes (also with spacing of