Hi there.
My name is Rob Morgan, and welcome to Victoria Road Crossover Box.
I'm here to tell you a little bit about how we built this massive structure.
I'm the Sub Agent for the Victoria Road Crossover Box,
which is the asset that you can see behind me.
We're here in West London, and we're on HS2 between
Old Oak Common Station and West Ruislip Portal.
So the Box serves three main purposes throughout its design life.
So the first is we're the launch location for two of the tunnel boring machines
that will bore from here to Green Parkway vent shaft
on the way to West Ruislip and out of London.
The second main purpose, is the Box will remain open to the air
throughout its design life, and that's to act as natural ventilation.
The trains pushing through the tunnels will generate a lot of heat
as well as when they break to come into the station.
That also produces a lot of heat, and that's got to escape.
So by having the natural ventilation here, it means that the temperatures
in the Old Oak Common station will be reduced by about seven degrees,
making the environment much nicer for passengers.
The third main purpose is to provide a crossover of tracks.
So this is one of the only places outside of the Old Oak Common station
that between Euston and West Ruislip, trains can cross tracks
to use a different track if there's a problem on the line.
So we took over this site from the early works contractor in March 2020.
We levelled the site and removed all of the old made ground,
and then we constructed a big 1.6 metre thick piling platform.
After that,
we brought in piling, a piling contractor and we constructed 77 tension piles
that will support the base slab.
After that, we mobilised a diaphragm walling contractor, and we built all of these walls
that you can see around me from ground level using diaphragm walling techniques.
The biggest challenge during the construction of the diaphragm walls
was the construction of the buttresses, which you can see at
either ends of the props.
Those involved a 100-tonne lift for each cage
and we had to build our own onsite manufacturing facility
to build those cages and then transport them
across Victoria Road using an SPMT,
which is a self-propelled mobile transporter, that's got 128 wheels.
After we finished pouring the diaphragm walls in 70 discrete panels,
we then started excavating and we dug down two metres
and we constructed the capping beam and the top row of props that you can see behind me.
After those were constructed we dug down about 13 metres,
and then constructed this ring beam and intermediate row of props.
After that was done, we dug down another ten metres.
The box is 128 metres long,
it's 42 metres wide at its widest point, and 25 metres deep.
The amount of steel that we've used to construct
all of the reinforced concrete elements is the equivalent
as the amount of steel in the Eiffel Tower.
We've excavated 240,000 tonnes of clay, from the Box
and we've mucked that all the way using the conveyor, which takes about
100 lorry movements off the road every single day.
So at scheme design, the Box was as you'd expect, rectangular,
but through engineering optioneering
we were able to change the shape to the 'caterpillar' shape that you see today.
What that does is, increase the utilisation of the concrete
and transfers the forces around to the props.
That reduces the amount of concrete that we've had to use by 40%
and saves a lot of carbon as well,
and also means that no temporary propping had to be installed, speeding up the construction.
So we're now at pit bottom of the Box. Ahead of me
will be the tunnels that go out towards Green Parkway and West Ruislip,
and then behind me is the route that'll go into the old Oak Common station.
Where we're stood right now is on the first base slab
of the Box, we poured this last Saturday.
It was our biggest pour to date at 1,385 cubic metres.
It took us 16 hours to pour and we've got four more
equivalent pours to do before we launch the TBM.
So this is the final stage of construction before we build the head walls,
which my colleague Ben is about to talk to you about.
So I'm Ben Newton.
I'm the FRC Section Engineer here at Victoria Road.
We're just preparing the head walls to be poured,
It's the last stage before we launch the TBMs.
There's three head walls here, we have the two head walls either side of the tunnel eye.
The purpose of the head wall is to support the diaphragm wall structure
when the TBM breaks through the wall,
essentially the forces are then sent through the walls and down to the piles.
Each head wall is around 130 metres cubed,
the head wall is nine metres tall by
around eight metres wide and 1.5 metres thick.
The main challenge is trying to pour the 'head pour' in one,
we need to try and create a nine metre tall shutter to hold the concrete in
and therefore all the green marks you see behind me
all the marks on the wall, we need to tie the former back into the diaphragm wall
to stop it from overturning during the pour.
So once the head walls are complete, we need to wait for them to gain strength,
that normally takes around a week to gain full strength,
and then TBMs will mobilise into the Box and they're ready to cut the tunnel eye.
So we're now at the Victoria Road ancillary shaft
this is on the same site as the Box, but over in the far corner.
The shaft is 25 metres in diameter and 25 metres deep,
It was constructed using a more common
method of construction with segments for the first 11 metres,
and then spray concrete lining down to the base.
After we completed that we constructed the secondary lining,
and a 1000 cubic metre base slab,
and then we handed the shaft over to our internal SCL team,
who are constructing the tunnels from here
back to the Crossover Box.
Once their works are complete, we will then take over the shaft and construct
a reinforced concrete core and a head-house.
Those will provide escape and access into the running tunnels
and will also provide services and signalling down to the track.
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