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London had the first underground
The stations must connect to the running
tunnels and the surface entrances, both of
which are being built by other contractors.
When station excavations are complete, the
tunnel boring machines will pass through
and resume their work on the far side, so
all tasks must be completed to rigid time-
tables to ensure smooth workflow without
delays. Alpine’s chief geotechnical engineer
Alfred Stärk says London clay “is pretty
much perfectly well formed for tunnelling, it
has no water and is easy to excavate”.
Nevertheless, it not fully known is what
structures the tunnellers may encounter. As
Dr Stärk explains: “London was the first city
that built an underground railway, and in the
1860s nobody paid attention to making re-
cords of where these underground structu-
res are. “At one stage nearly every building
had a well. Those days are gone but the
wells haven’t, and not all of them are recor-
ded. At Liverpool Street we were tunnelling
and suddenly there was a well that was not
on any drawing.”
That well was easily made safe, but the
work at Liverpool Street (which links to
nearby Moorgate station) is highly com-
plex because the site is crossed by London
Underground’s Hammersmith & City and
Northern lines, by the Post Office’s disused
rail line – now used for telecommunica-
tions cables – and by the long-abandoned
Queen Victoria tunnel.
One further complex piece of work will be
the Vallance Road crossover, to enable tra-
ins to change from the westbound to east-
bound track at Whitechapel. With up to a
20m span it will, Dr Stärk says, probably
be one of the largest structures ever built
in London clay.
It is essential that everything is built to last
– Crossrail structures have a 120 years de-
sign life – so two of Alpine BeMo’s most
experienced quality inspectors have been
called in. Hermann Dettelbacher and Karl
Fender have 70 years’ experience between
them. This experience will be essential in
order to complete one of the most complex
underground “jigsaws” that they are ever
likely to encounter.