TRACKISDN File: RGJberlin .MAC

Keeping it QUIET below Berlin
Dipl-Ing Mirko DoldGetzner Werkstoffe GmbHHE FOUR-track railway being built
in the heart of Berlin is intended
to create a 9 km link between thenorthern and southern sides of thecity’s inner rail ring (RG 6.97 p379).

T

About 3·5 km of the route runs underground, from the Landwehrkanal,
beneath the commercial centre of
Potsdamer Platz, and under thegovernment district to Lehrter station,
where the line intersects with theexisting east-west elevated Stadtbahn.
When completed, the new Berlin
Hauptbahnhof at this point will becomea major interchange for Germany’s eastwest and north-south inter-city routes.
Vibration and secondary airborne noise
emissions from the railway must not
impair the use and environment of theseimportant buildings along the route,and so the inclusion of preventative
measures was a high priority when
designing the infrastructure.
DB ProjektBau GmbH is building theline on behalf of Deutsche Bahn AG,
and commissioned engineering
consultants Dr Heiland to model thetransmission of vibrations from thetunnel floor into adjacent buildings.
This model formed the basis for thedesign of mass-spring measures toreduce vibration and noise.
Instead of being fixed to the tunnel
floor, the track sits in a massive, rigid
concrete trough which is supported above
the floor by individual and full-surface
resilient polymer bearings designed andsupplied by Getzner. The inertia of thisslab interacts with the resilient springs todamp the vibrations caused by trains. A
total of six different mass-springarrangements were chosen for use in thetunnel, with the heavy mass-spring
systems having calculated frequencies of7 to 12 Hz, and light examples natural
frequencies of 15 to 23 Hz.
The diverse requirements for specificbearings were met using bearings with arange of geometries, from the smallest at
380 x 310 mm to a maximum of 500 x
460 mm, with thicknesses ranging from60 to 95 mm. Each of the mass-spring
systems has been individually approvedby the Federal Railway Authority (EBA).

Building a main line railway under the heart of Berlin
demands the highest standards of vibration and noise
prevention. The answer is to use concrete slabs
supported on polymer bearings
concrete slab in situ, up to 700 mm
thick. This ensures that the slab will
replicate the shape of the tunnel withgreat precision.
The use of a lining ensures that once
hardened the entire slab can be lifted by
up to 110 mm without damage, usingsynchronously-controlled hydraulic jacks
which are placed in openings left in theslab during casting. The slab is lifted in
200 m sections, weighing in excess of
1 500 tonnes, and a template is used toposition the bearings precisely using asliding gauge, before the trough islowered onto the bearings withmillimetre-accuracy.
Up to eight individual bearings can beinstalled at each opening. Each bearing
is numbered , and written andphotographic records are made of its
installation site.
In the light mass-spring systems theInstallation
Assembly of the heavy mass-spring
systems involves installing a lining on
the tunnel floor, then pouring theAs part of the process to install the track slabs
though the low-level platforms at Berlin’s new
Hauptbahnhof, Sylomer mats andreinforcement bars were laid (top) before theconcrete slabs were cast (right). On the northsouth link, both full-surface and discrete
supports were used (Fig 1, inset right)
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January 2005 Railway Gazette International41

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concrete trough is poured directly onto
a double layer of pre-installed, fullsurface elastic 50 mm thick mats, which
act as sacrificial formwork. Some
35 000 m2 of slab in the Berlin tunnel isbeing fitted with full-surface resilient
mountings.
The two layers are installed with thejoints offset by half the width of themat, and the upper layer joints aresealed with an adhesive band to prevent
concrete slurry penetrating between themats. Any such seepage could lead tothe creation of ‘sound bridges’, which
would reduce the effectiveness of theanti-vibration measures.
The thickness of the resilient mats is
reduced from 50 to 25 and 12 mm
across the transitions between sections
with and without the mats, and by
adjusting the effective stiffness of themountings this will prevent excessive
bending stresses on the rail and slab atthe transitions. Once the mats are inplace the steel reinforcing bars are
installed, and concrete is pumped in.
The restricted space available in thetunnels requires close co-ordination
BELOW: Installation openings are left during
the casting of the track slab, so that it can bejacked up for the bearings to be installed
BELOW RIGHT: Up to eight individual bearings
can be positioned using each hole to an
accuracy of a few millimetres
RIGHT After the bearings are installed, the lab
is lowered into position so that the resilient
elements can take the full load

42

Railway Gazette International January 2005

between Getzner and the site supervisors
to ensure continuous and just-in-time
deliveries of the 1·5 m wide and 4·2 m
elastic mats as construction progresses.
Full-surface elastic mounting of theconcrete track slabs on the mats hasgone smoothly, with a low additional
cost above that of the sections without
vibration protection.

Quality assurance
Heavy mass-springs are a technicallyhigh-quality way of meeting extremely
stringent requirements, and using
Sylodyn polyurethane bearing elements
it is possible to achieve this at an
acceptable price. Similar noise andvibration protection measures wereinstalled on the Köln – Frankfurt highspeed line.
The quality of the bearings installed ischecked using comprehensive quality
assurance methods developed for theproject by ARGE FF/MFS(Heitkamp/Porr), Dr Heiland and theTechnical University of München’sInstitute for Road, Railway & Airfield
Construction. Measurements of theABOVE LEFT: Sylomer mats were installed inthe transition areas to adjust the track
stiffness between the rigid and resilientlymounted track slabs
ABOVE: Casting of track slabs in the maincross-city tunnel

natural frequencies of track sections
which have been completed provide further data, ensuring that the installation
work was being performed properly.
Constant measurements of ground andstructure-borne noise are being madeduring the work in Berlin, and up to
now the results obtained confirm thatthe forecast levels of vibration and noisein surrounding buildings have beenachieved.
Construction of the line is welladvanced, and almost all of the slabs
have now been laid. The final section,
totalling around 4 000 m2 of slab, is due
to be completed by March, completingthe link between the low-level sectionof the Lehrter Bahnhof and the entrance■
to the north-south tunnel.