Geotechnical News • December 2015
39
THE GROUT LINE
Practical application of the GIN concept (Part 1)
Clif Kettle & Maren Katterbach
Designer’s overview
The GIN concept is a self-regulating
approach of controlling simultane-
ously both the injection pressure
and rate of injection, to avoid a
combination of high volumes and
high-pressure, whilst at the same time
setting defined limits on maximum
volume and maximum pressure. In
general terms the GIN concept aims
to optimize the grouting process. In
particular, it aims 1) to grout only
where absolutely necessary, in this
way avoiding any waste of grout and
2) to use highest practicable grouting
pressures without causing any dam-
age, in order to enhance the efficiency
and success of the grouting operation.
This concept was first introduced more
than 30 years ago by Eng. Lombardi
and Eng. Don Deere, with the inten-
tion of avoiding damage to the fissured
rock formation, whilst greatly improv-
ing the efficiency and effectiveness
of grouting operations. One of the
intentions of the process is to equalise
the radius of flow in fissures of vary-
ing widths.
Remarkably, with all the advance-
ments in grouting over the last
decades, the GIN concept has
remained largely intact and has
proved to be a reliable tool to manage
efficiently the grouting process under
varied conditions in numerous projects
worldwide. With its well-founded
physical basis, its generality, and
finally its simplicity, the GIN concept
clearly and consistently illustrates that
grouting does not, and should not,
represent an obscure art.
Contractor’s overview
Bachy-Soletanche personnel have
been using the GIN concept for rock
grouting for more than 30 years in a
wide range of rock conditions, from
karstic limestone, through finely
fissured chalk, to heavily fractured
sedimentary and volcanic formations,
and have come to value the technique
for its simplicity and efficiency, to the
extent that it is now a prime con-
sideration when reviewing any rock
grouting solution for either block
consolidation/impermeabilisation, or
as a grouted cut-off.
The GIN technique is considered not
so much as a method of grouting, but
simply as a tool, one of many essential
tools used by the grouting engineer
to achieve a successful outcome. As
with any tool used in any type of
work, it requires understanding, skill,
and experience to be able to employ it
effectively in the workplace. Further-
more, GIN grouting involves experi-
enced observation and interpretation
throughout the grouting programme.
Based upon the initial observed
results, the GIN value, and the vari-
ous injection parameters, should be
adjusted where necessary during the
course of the grouting programme, but
thereafter, the objective should be to
change as little as possible to maintain
a consistent strategy.
The technique has proven itself on
worksites where other techniques have
failed, and has delivered a high quality
of ground treatment in challenging
rock conditions, whilst at the same
time providing significant economic
benefit for both client and contractor
alike.
For success and maximum efficiency
it is essential that the technique, as
with all techniques, is configured to
suit the local ground conditions. This
may seem obvious, but there have
been many cases of specifications and
grouting strategies being too rigidly
applied, sometimes simply copied
from elsewhere, in the expectation that
these can be imposed on the ground,
and that the ground will comply.
Clearly, it will not, and thus this
approach is predestined for failure.
Within the Bachy Soletanche group,
the GIN concept of fissure grouting in
rock is seen as a major advance in the
practical application of rock grouting
technology. This view is also widely
held amongst practising contractors
due to the simplification of the core
injection process, the self-regulating
control of excessive hydro-fracture
pressures, and the improved facility
for comparison and interpretation of
the grout injection data across numer-
ous phases of injection.
On the following pages, some gen-
eral technical aspects related to GIN
grouting will be discussed. In the next
Groutline issue (Match 2016), several
case histories of projects in which
Bachy-Soletanche has been involved
are presented.
Technical aspects related to
GIN
Basic rules for GIN injection
When it was introduced some 30 years
ago, the grouting intensity number was
just a numerical value, defined as the
product of injected grout volume and
applied pressure, GIN = P.V. However,
over time, with technological advances
and improved field experience of the
approach, further aspects related to
grouting of fissured rock masses have
been developed and incorporated
within GIN injection.
Despite various developments, the
basic GIN concept itself has remained
unchanged across the industry, so that
today there is a broad consensus as to
what constitutes the essential features
of this technique, which can be sum-
marized as follows:
