Geotechnical News • March 2018
47
THE GROUT LINE
Mix design was started in the Contrac-
tor offices in Italy prior to mobiliza-
tion using cement and bentonite from
sources being considered for the proj-
ect. This effort continued at the site in
a brand new laboratory set up for the
project. MoWR laboratory person-
nel participated throughout the entire
testing program and they are currently
performing QA testing of the mixes as
part of the integration program.
A base mix is prepared at the mix-
ing plants. The base mix is circulated
through the grout conveyance system.
The batching and grouting units at the
injection hole draw the base mix from
the conveyance system and modify it
by adding bentonite slurry, admixtures
and water in appropriate proportions
to achieve the desired design mix.
Mortar mixes can be delivered through
larger pipes installed throughout the
gallery or vertical shafts from the crest
of the dam.
Grouting methodology
Up to date, a total of over 30,000 m3
of grout have been injected, in almost
1,900 boreholes. The adopted grout-
ing methodology has varied across the
dam based on encountered geology
and observed issues while drilling.
Issues encountered during drilling like
hole collapses, water loss were taken
into consideration while designing
the grouting methodology for each
section. The upstage method was the
most preferred grouting method to
keep up with the aggressive produc-
tion schedules. However, the down-
stage and downstage zone methods
were also used based on field obser-
vations and geology. Each hole was
pressure grouted in 5m intervals using
a single packer lowered in the hole,
at top of the stage to be grouted. The
entire grouting operations have been
automated using sophisticated grout-
ing software.
Grout monitoring systems
All the grouting operation are con-
trolled, monitored and managed by
“T-Grout”, a proprietary Automated
Control System of the Grouting Pro-
cess (Figure 12).
Automated data acquisition systems
(“manifolds”) are setup near the injec-
tion hole, directly connected with the
Figure 11. Batching and grouting unit.
Figure 12. Computerized grouting control, monitoring and recording system.
Table 1. Main types of grouted mixes. Average values, measured on 23011
samples of fresh grout and 3520 specimens (at each curing time).
