The document summarizes the Crossrail tunneling project taking place beneath London streets. Giant tunnel boring machines will construct 26 miles of tunnels costing £16 billion. The reporter describes visiting two Crossrail construction sites - at Stepney Green where tunnels are being carved out using traditional mining techniques and concrete lining, and at Pudding Mill Lane where giant tunnel boring machines costing £10 million each will bore through London's clay soils. Once completed in 2018, Crossrail will connect locations in London and the surrounding counties, serving an estimated 200 million passengers annually.

1. 4 Wednesday July 10, 2013
Beneath our streets giant
‘moles’ will be munching
away at the earth to carve out
26 miles of tunnels for Eu-
rope’s largest construction
project worth £16billion.
After being kitted out with
orange clothing complete
with hard hat, glasses and
gloves, and sitting in on a
safety briefing, I stay close
to construction manager Rob
Gordon as we enter a big lift
lowering us 40-metres down a
shaft at Stepney Green.
Above ground, the location
of this Crossrail construc-
tion site could not be more
peaceful with animals graz-
ing at Stepney City Farm and
children playing at nearby
Sir John Cass School.
Rob emphasises that they
have only had one noise
complaint from nearby resi-
dents and that all the activ-
ity is underground. Lorry
movements to and from the
site are restricted to outside
school hours.
As we step out from the
lift below we are faced with
immense activity as I find
myself inside one of the larg-
est mined caverns ever con-
structed in Europe.
Flashing red lights warn
of moving vehicles, cranes,
and skips unloading cement
and carrying excavated earth
as we stand between the
eastbound and westbound
caverns. About 7,500 cubic
metres of soil was dug to
create the eastbound cavern
and 9,000 cubic metres for the
westbound cavern.
Technique
Stepney Green will not be a
stop on the Crossrail network
but it is unique among the
construction sites as this is
where the line coming from
Whitechapel will branch out
in two directions – one head-
ing to Shenfield via Stratford
and the other towards Abbey
Wood via Canary Wharf, Cus-
tom House and Woolwich.
Tunnelling machines Eliz-
abeth and Victoria are ex-
pected to break through here
in October – one into the east-
bound cavern and one into
the westbound cavern.
Two other twin machines,
which will be named in a
competition, will be coming
from Pudding Mile Lane and
are expected to arrive here in
August.
The caverns are five metres
apart – 35 and 40 metres deep
– allowing the tunnel to Strat-
ford to run under the route to
Canary Wharf as they cross
each other.
The tunnels are being
made using a technique
called sprayed concrete lin-
ing rather than letting the
giant boring machines carve
their way through.
Rob explained that it took
two months to get the texture
of the concrete right.
“Normal concrete is a bit
like scrambled egg whereas
this stuff is a bit like a souf-
fle – it is very sensitive, you
need to get all the constituen-
cies right. It’s got additives,
microsilica and steel fibres.
“Normal concrete takes
longer to settle, which is fine
if you have got a supported
building, but we need to
achieve an inner strength or
the cement won’t stick to the
tunnel walls.
“The mix is made off site
because of the school and
residential homes nearby
and dispatched over. It
then goes through a special
pumping unit, which sprays
the concrete out with an ac-
celerator at the nozzle.
“The reasons these tech-
niques are employed here
are because of the geology
of the cavern itself. It’s a bit
of a trumpet that gets larger
and larger. London clay is
soft like cheese and ideal for
tunnelling.”
While the cement is being
sprayed on the walls of the
westbound cavern, a water-
proof lining is being fitted
to the floor of the eastbound
tunnel, allowing water to
drain away.
The £500,000 contract to
build the Crossrail caverns
was awarded to a Span-
ish-Irish venture, Draga-
dos/Sisk JV, and the highly
skilled workforce, which
includes civil engineers
and miners, has come from
across the world.
Rob says: “Most of the
guys here have been doing
this type of work for at least
20-odd years.
“They may have worked
on the new stations at Tot-
tenham Court Road, King’s
Cross and Heathrow, and
before that the Jubilee Line
and Channel Tunnel or else-
where in the world. Cur-
rently we have about 30 peo-
ple on site but at one point
we had about 40.”
The site operates 24/7
with 12-hour shift. A longer
weekend allows workers
from places such as Wales
to return home to see their
families while others have
settled within commuting
distance.
A £13m Tunnelling and
Underground Construction
Academy, part-funded by
Crossrail, was set up in Il-
ford after it was recognised
that there was a skill short-
age for future projects in
this country.
Once I have surfaced from
underground, I’m taken
with our photographer on a
minibus to the nearby Pud-
ding Mill Lane Portal.
As we are lowered in
a basket, offering a view
across to the Olympic Park
at Stratford, a very different
construction site is unveil-
My journey into
a subterranean
world of activity
Reporter Else Kvist pays a visit to Crossrail sites at Stepney
Green and Pudding Mill Lane to discover the work going on
underground
Tunnelling in Stepney Green that will form the Crossrail link
Crossrail
London
clay is soft
like cheese
and ideal for
tunnelling
Huge machinery at the Pudding Mill Lane site Pictures: Isabel Infantes

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Wednesday July 10, 2013 5
Tunnelling
machines
Eight boring
machines will be
used to construct
the new tunnels.
Each is manned
by a 20-person
‘tunnel gang’
working in shifts.
As the machines
move forward,
precast concrete
segments are built
in rings behind
– 250,000 tunnel
segments will
be used to line
Crossrail’s tunnels.
4.5 million tonnes
of excavated
material from
the tunnels will
be shipped to
Wallasea Island in
Essex to create a
1,500-acre RSPB
nature reserve.
ing itself before our eyes.
Inside a box-shaped hole,
16 metres deep, one of the
giant boring machines is al-
ready in place underground
waiting for take-off to the
cavern at Stepney Green.
Its twin machine is cur-
rently going through final
factory testing in Germany
before it will be dismantled
and shipped over.
It is expected to arrive on
site in about two months
when it will be put together.
Construction manager
Frank Jenkins explains that
each of these beasts costs
£10million.
Each machine is about
150 metres long and weighs
1,000 tonnes and on average
creates 100 metres of tunnel-
ling a week.
He said: “Whereas the
construction method at the
Stepney Green cavern is
more traditional mining
– using traditional excava-
tors to dig away against
the ground before spraying
on the supportive concrete
– here we use the tunnel bor-
ing machines.
“It’s basically like a huge
mole. At the front of it there
is a cutter disk which rotates
about three times a minute
and grinds away at the clay
and the chalk and it gradu-
ally gets pushed forward
by hydraulic rams creating
rings in the earth.”
Though computerised, a
driver sits inside a control
panel at the front of the ma-
chines to monitor progress.
Their route has been care-
fully planned to avoid any
obstacles such as water pipes
and to stay clear of build-
ings that may not withstand
movement in the ground.
Once the machines reach
Stepney Green they will be
lifted out and taken by police
convoy to the Limo site at
Canning Town before being
put to work again as Cross-
rail takes shape.
Else Kvist is lowered into the construction site at Pudding Mill Lane
Frank Jenkins
The Crossrail site at Pudding Mill Lane
The Crossrail project
A 73-mile (118km) railway will link
Berkshire and Buckinghamshire via
Greater London to Essex with 26
miles (42km) of new tunnels.
The estimated cost stands at
£16billion.
Work started in 2009 and there
are 8,000 people working across 40
construction sites.
There will be 37 Crossrail stations
– the line will bring an extra 1.5
million people to within 45 minutes
of central London.
The first services will start through
the tunnels in late 2018.
An estimated 200 million annual
passengers will use Crossrail.
Crossrail will replace the trains run
by Greater Anglia through stations
such as Forest Gate and Manor
Park. These trains will remain on the
surface before branching off on to a
new track and entering the tunnel at
Pudding Mill Lane.