A complex tunnelling project to enable electric trains to
run between Bolton and Manchester has been delayed,
possibly until December, by exceptionally poor ground
Network Rail engineers enlarging the 1834-built
Farnworth Tunnel ran into large swathes of sand, rather
than a firmmaterial to bore through, which pours down
into the excavated area halting progress.
It has proved impossible to safely excavate while
concurrently installing and grouting sections of tunnel
wall as was originally planned.
Engineers are now pumping resin into the ground to
firm it up before 9 m wide Fillie, the UK’s largest tunnel-
ling machine, bores through it.
For local train passengers the railway between Bolton
and Manchester will continue to operate as it has since
Martin Frobisher, route managing director for
Network Rail, said:
“We first hit an area of running sand on August
14 when our engineers saw it suddenly pouring
from the working face. This has slowed progress
and created big voids, the largest of which
needed filling with around 35 tonnes of grout.
Again on August 27, sand poured into the
excavated area and our engineers had to remove
100 tonnes of material by hand.
“The nature of civil engineering, especially
deep below ground, is that you never fully know
the exact ground conditions until you start tun-
nelling or excavating. Taking soil samples acts
as a guide but is never 100% accurate because
conditions vary greatly with the amount of water
“The rate of progress is very dependent
upon the conditions and we are working around
the clock to complete this as quickly as
“Our top consideration is safety. Our engi-
neers face a huge challenge. We must allow
them the time they need to tackle it safely. We
Contractors World UK & Ireland Vol 6 No 1
Contractors World UK & Ireland