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Geotechnical News • December 2014
www.geotechnicalnews.com
THE GROUT LINE
Paolo Gazzarrini
Overture
Christmas is approaching, and for
the 37th episode of the Grout Line, I
present to you an article related to a jet
grouting job carried out in Austria few
years ago.
I have long been looking for the
world’s biggest jet grouting job, and
a few weeks ago, participating in a jet
grouting workshop in Italy, I watched
a presentation that just might have
solved my problem.
The following article, prepared by
Marco Ziller (Overseas Department-
mziller@trevispa.com), Maurizio
Siepi, (Head of Technological Office
-msiepi@trevispa.com) and Marco
Angelici (Technological Department-
mangelici@trevispa.com), writing
from TREVI SpA, describes a case
history of jet grouting, where 15,300
columns where installed for a total of
210,000 meters (690,000 ft) drilled.
Is this the biggest jet grouting job ever
carried out in the world?
Let me know if you know of anything
bigger!
Merry Christmas, and I wish, every
one of you who has the perseverance
to read this Grout Line, a
FANTASTIC 2015!
A challenging jet grouting project
for the construction of the railway tunnel in Stans (Austria)
Introduction
The new Munich-Verona high speed
railway line is part of the Trans-
European Transport Network rail link,
connecting Berlin to Palermo (TEN-
T, see Figure 1). The network also
encompasses the future Brenner Base
tunnel which, with its twin 55 km long
tubes, is slightly shorter than the 57
km Swiss Gotthard Base Tunnel.
To manage the design and engineering
processes of the works on the Aus-
trian side, the Austrian government
formed the Austrian Brenner Railway
(Brenner Eisenbahn Gesellschaft,
BEG) company. Consulting services
for the geotechnical design were
assigned to ILF-Geoconsult ZT-iC,
and Studio HBPM was the jet grouting
expert consultant.
In the proximity of Innsbruck, the new
railway line runs parallel to the Inn
River, to the A12 motorway, and to the
railway to Munich (see Figure 2).
Eventually BEG designed a series of
projects aimed at minimising the envi-
ronmental impact on the area adjacent
to the line, both during and after
construction. At design stage, BEG
defined methodologies to deal with
the diverse situations, selecting either
excavation and covering of trenches or
the use of TBMs.
However, close to the small village of
Stans, where the new line is situated
close to the river, close to a motor-
way viaduct and close to the existing
railway line, an alternative solution
was necessary; the 750m long tunnel
passes some 30 metres under the river
bed in difficult ground conditions.
In order to minimize the disruption
to existing lines, the BEG designers
foresaw for the tunnel a 2 m thick jet
grouted protective shell, which would
be watertight and strong. Moreover,
as a second line of defence, the use
of compressed air was foreseen to neu-
tralize any residual permeability.
BEG entrusted the job to Alpine/GPS,
which in turn subcontracted to Trevi
the execution of the specialized works
for soil improvement.