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INFRASTRUCTURE
At 8.1 metres in diameter, the tunnels beneath London that
High Speed 1 will be using are the largest ever under a UK city.
waving razzmatazz. The second phase, which
includes 11.5 miles of tunnelling under the
approaches to London, was always seen as
carrying more risk.
‘Obviously, coming into south-east London
there are hundreds of thousands of homes that
potentially could have been affected,’ explains
Bennett. ‘But the construction of the tunnels
went exceptionally well with very little
disruption.’
Not that everything went entirely to plan.
Bennett recalls one well-publicised incident at
Stratford when a tunnelling machine hit an
uncharted well. ‘Sometime after the tunnelling
machine passed through, part of a back garden
disappeared. It was behind a row of very pleasant
but fairly modest terraced houses. But it was
reported that the insurance claim included a
Harley Davidson and several crates of
Champagne that had disappeared down the
hole!’
That’s the sort of thing that can happen when
you are digging nearly 12 miles of tunnels, which
also leaves you with a mountain of spoil to
dispose of. ‘Potentially we were looking at
Tunnel vision
Constructing a railway line in nearly 12 miles of
tunnels isn’t easy – particularly when the track
has to be fixed onto concrete slab.
‘You are limited to how you can get the
materials in,’ says Dave Bennett, highlighting
one of the main difficulties.‘There’s the tunnel
entrance and a small number of major shafts –
and that’s it!’
Undeterred, contractors working on the highprofile
project came up with an innovative
hundreds of thousands of lorry loads of material
that would have had to have been transported
through London, with a hefty bill to be paid for
disposing of it all,’ says Bennett.
The development site at Stratford, which will
be home to the 2012 London Olympics, came
to the rescue, as Bennett explains: ‘It is a lowlying
area prone to flooding. So we used almost
all of the tunnelling material to raise the entire
40-hectare sight by up by eight metres. It had the
dual benefit of making the land significantly
more developable and cutting out the need for
solution. Rather than take the concrete into the
tunnels, they decided to make it on a specially
adapted train.
Bennett elaborates:‘In practice we created a
complete concrete factory on a train that was
several hundred metres long.
‘The raw materials were carried on the train
and the concrete mix was pumped out of a pipe
at the front to exactly where it was needed in
the tunnel.’
all those environmentally damaging lorry
journeys. It’s a very good example of how High
Speed 1 has worked to minimise its impact on
the environment.’
With attention switching inevitably to
November’s grand opening, all eyes are now on
St Pancras and the new International station
taking shape behind the familiar Victorian
edifice on London’s busy Euston road. Bennett
says: ‘People talk about the station in the same
way as they would St Paul’s cathedral. And we
have the job of putting four railways into it: high
MAY 2007 : RAIL PROFESSIONAL
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