Netherlands: high-tech fastening for high-speed track ... - Hilti

Magazine Fall/Winter 2005
Engineering
Page 19
tile. “At the planning stage, for
safety reasons, we had to conservatively
reduce the resulting coefficient
of friction from the measured
0.4 to a value of 0.1 in order to account
for vertical dynamic effects,”
continues Peter Meijvis. After
reducing friction in this way,
90% of the load is taken up by the
dowels. “The total of 13 dowels in
each concrete slab – 9 in the center
section and 2 at each end – is
capable of taking up this load with
the required high safety factor. In
theory, a lower number of dowels
would have been adequate, but we
decided on a redundant system because
even just a scratch in one of
the round bars could be enough to
initiate a fatigue fracture.”
Drawings of the entire stretch of
track hang along the walls of the
long corridor leading to Peter Meijvis’s
office. Although he knows
the details on the drawings by
heart, he’s still amazed to see how
this light-colored strip of concrete
is taking shape as it progresses
through the Dutch countryside. Peter
Meijvis and his colleagues will
almost certainly be sitting in one of
the very first trains. All of their
planning and problem-solving will
then seem to whiz past in a kind of
time-lapse playback as they travel
along the track at high speed.
Hilti Concrete Dowels proved
their load-beaning capacity and
reliebility in extensive tests.
Read more on page 20.
The new
railway pioneers
Project Manager Theo Winter has
an admission to make: “I certainly
had a few sleepless nights.” He is in
charge of all the work on the highspeed
rail track that the Infraspeed
consortium has entrusted to the
subcontractor Rheda 2000 vof. To
begin with, he and his team had no
answer to the question of how the
concrete superstructure could be
connected to the substructure. But
then the Hilti engineers laid their
proposal on the table and this
stretch of track between Amsterdam
and the Belgian border began
to take on pioneering character.
Mr. Winter, why did the concrete
to concrete connection
cause so much of a headache?
Theo Winter: Such a thin superstructure,
as is demanded by this
project, is the first of its kind in the
world. Not only that, but the points
at which the holes could be drilled,
and thus the number of holes for
anchoring the dowels in the substructure,
were strictly limited to
three zones. And, of course, the
concreting work for the substructure
had already been completed.
These limitations meant that the
use of conventional methods
could be ruled out.
Only 8 kilometers of the total of
about 90 kilometers from Amsterdam
to the Belgian border is laid
on ballast. The rest is slab track.
For about 60 kilometers of this –
that’s about two thirds of the entire
stretch – we’re now using the Hilti
concrete dowels.
Theo Winter: “The thin superstructure in this project
is the first of its kind in the world.”
What impresses you most
about this solution?
Theo Winter: Its simplicity – in
the true sense of the word and in
two ways. The dowels for the
center section of the superstructure
slab stand out, above all, due
to the simplicity of their design
and their ease of use. The installation
process can be easily organized
because it is so straightforward.
This method pays for itself,
especially when labor costs are so
high.
Did it allow you to raise
efficiency?
Theo Winter: Yes, certainly! When
I make a comparison with conventional
methods, we are definitely
making faster progress with the
Hilti dowel system.
Despite rapid progress, quality
still has to be guaranteed.
Theo Winter: The low tolerances
demanded by this project are an
indication of high quality and, at
the same time, are a great challenge.
We measure rail alignment
to a tenth of a millimeter! A tolerance
of only 2 millimeters is permissible
over a length of 5 meters.
And don’t forget that the trains will
reach speeds of up to 330 kilometers
per hour in tests and 300 kilometers
per hour in normal operation.
That makes precision essential.
The long service life of the railway
is also a question of quality, and I
look upon that as an even greater
challenge. The substructure has
been designed to last 100 years
and the superstructure has a projected
service life of at least 50
years. Maintenance of the rail
track for the first 25 years will be
the financial responsibility of the
Infraspeed consortium. The scope
of maintenance required must not
increase for a further 5 years beyond
this period. This has been
agreed by contract with the Dutch
government authorities. High
quality is thus also in our own interest.