Anyone passing near the Centre Point tower over the past few years cannot help to have noticed the huge construction site on the corner for the future Crossrail station.

Although generally considered a Crossrail site, it is in fact largely a London Underground building site, with most of the work going towards a huge expansion of the ticket hall and improving access to the tube platforms.

Although Crossrail gets one small corner, for its own escalators.

So this project really should be looked at as part of the tube upgrade project — and a very large exceptionally visible one. And an upgrade costing around £500 million to carry out.

The reason for such a huge upgrade is obvious to anyone who ever uses the station. At the moment, there is a very small ticket hall area, and one bank of escalators down to a concourse, where it splits to the Central or Northern Lines.

When finished, the ticket hall will be six times larger, and there will be three separate banks of escalators down to the three separate underground railway lines. That is necessary as the station currently handles some 150,000 people per day, and that is expected to reach 200,000 by 2018.

Last week was a chance to have a look around what has been hewn out of the soil.

Although the construction has been carried out in many stages, it is in essence, a two-phase construction site.

Phase 1 is the building of a new ticket hall and two new escalator shafts.

Phase 2 is the upgrade of the old ticket hall and modification of the existing escalator shaft to dedicate it to the Central Line.

Once finished, you shouldn’t really be able to see the join between old and new. In theory.

Phase 1 though is nearing completion, and will be essentially finished around the middle of next year, after which it will undergo several months of testing. Sometime late next year, the old ticket hall will close, and the new one will open.

Once the new ticket hall opens, sorry, but in 2015, the Central Line will stop calling at TCR station for nearly a year, as that part of the station gets a major overhaul and the platforms get the same treatment given to the Northern Line in 2011.

Phase 1 started construction in 2007 with diversions of sub-surface services and sewers.

Once the area was cleared, they dug down two floors — one for the ticket hall, and a basement for the staff and services.

tcr-tube-crossrail-station-interchange-level-minus-4-of-5-lg

However, the escalator shafts are a totally different affair.

In fact, before the roads in the area could be diverted to allow the main site works to go ahead, they had to dig the Northern Line shaft first, as the bypass road in use today runs right over the top of it.

escalator-box-below-charing-cross-road

You may recall that the Northern Line platforms were closed for a number of months in 2011, so that they could squeeze in new tunnels between the two platforms and a future lift shaft.

What has now been constructed is the escalator shafts down to a huge tunnel concourse, and then a side tunnel that leads down to the platforms. In the next few weeks, the escalators will be slowly lowered down the shafts and bolted into place.

tcr-image-3-full

That deep structure running so close to the existing Northern Line tunnels also needed some innovative new techniques. For example, piles driven down into the ground are usually circular, but here the pile needed to be a set width, but there simply wasn’t enough space.

A novel D-shaped pile was developed that could fit into the space and still deliver the necessary amount of support. Apparently it’s up for some engineering awards.

The massive chamber at the base of the escalators was constructed using “side wall drift”, which is basically four tunnels next to each other, then the thin walls between them are broken away to leave the single huge cavern.

On our site visit, the other equally impressive Crossrail escalator shafts were covered in scaffolding so it wasn’t possible to go down them.

Another area that will have escalators are at the new station entrance, which will have escalators direct from street level to the ticket hall.

Meanwhile, a long way from where we were taken, long tunnels have been dug for the Central Line — including a few extra bits for when Crossrail 2 gets approved — and there was a fascinating photo of how they dug around the outside of the railway tunnel to expose it, and then slice off the top for a new footbridge.

figure-5

Construction of those tunnels was affected by a sewer running just overhead, so the normal circular tunnel is flattened slightly at the tops to avoid the sewer.

Its worth remembering that these new tunnels are essentially dug by hand. Mainly using small mechanical diggers, but quite literally in places, hand shovels and brute force. No sexy tunnel boring machines down here.

central-line-interchange-with-waterproofing

The station upgrade will be completed towards the end of 2016 — with two dedicated tube escalator shafts working away, and a third laying dormant waiting for Crossrail to arrive.

Sadly, no photography inside the building site was allowed — so all images from within are from the TfL website, except the Central Line over bridge, via Dr Sauer Group.

And yes, before any one asks, the mosaics are being preserved.

The site visit was part of the weekend’s Open Doors event

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2 comments
  1. Josh says:

    So there is space to fit a circulation concourse between the two platforms?

    • IanVisits says:

      Nope — the bottom of the escalators is above, and to one side of the Northern Line platforms. There is a side passage shown in the image above, and steps down to the Northern Line platform.

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