RAIL travellers heading north from Eindhoven may notice a sudden quiet
descend on the train as it hits three kilometres of new track near the tiny
Dutch town of Best. Civil engineer Frans Kloesters has just completed a test
installation of a new type of track, based on a bed of cork composite, which
should make the high-speed train lines less noisy, longer lasting and cheaper to
maintain.
His employer, NS Railinfrabeheer, an engineering subsidiary of Dutch railway
Nederlandse Spoorwegen, believes this new method of laying track will be copied
all over Europe, if the tests are successful.
鈥淭he traditional rail line is based on steel rails, concrete sleepers and
crushed-stone ballast,鈥� Kloesters explains. 鈥淭he ballast provides a firm, yet
elastic bed for the rails, and works fine so long as train speeds stay below 250
kilometres per hour.鈥� But above this speed the ballast itself becomes a problem,
as the French railway has discovered with the TGV, which travels at between 280
and 300 kilometres per hour.
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Vibration from the train rushing overhead causes the stones to shake and
crumble. Small fragments end up on top of the rails, where they 鈥渋mprint鈥� and
ruin the surface, soon destroying the track.
鈥淎s the stones crumble, they become round, and the ballast loses both its
ability to resist lateral forces and its elasticity,鈥� says Kloesters. The
ballast turns into a loose layer of round stones sitting on top of a layer of
fine sand that has been sifted and compacted to the consistency of concrete.
Daily inspections and frequent maintenance are required, making the lines
expensive to run and prone to stoppages.
The Dutch railway has been experimenting with various alternatives since the
1970s, but has only now come up with an economical design. The new test track
has been made with the rails embedded in a polyurethane-cork composite, which is
poured into channels in a much lighter concrete base that can be laid in place
with a paving machine originally developed for roads.
Kloesters realised it could be used for railways after seeing it being used
to make tram lines in Sheffield. The paving machine moves along a path defined
by thin steel cables, so the precise geometry of the line is controlled, metre
by metre.
鈥淟ines with stone ballast must be checked often, because they work constantly
and get out of alignment,鈥� Kloesters says. 鈥淏ut these lines will never have any
alignment errors, unless they are introduced during construction.鈥�
He is confident that steel rails will last longer on the new tracks. 鈥淭hey
will last 50 years rather than 25,鈥� he says. And they should even pay for
themselves鈥攍ower maintenance costs will mean savings, so that even with
construction costing about 25 per cent more than normal, over a 40-year period
they will save 25 per cent in total costs. 鈥淭hey will also be quieter,鈥� says
Kloesters, 鈥渂oth for passengers and people living near the tracks.鈥�
