Earlier today, a major upgrade to Victoria tube station was completed, when an entire new entrance and set of escalators was opened to the public.

This is the culmination of planning that can be dated all the way back to 1996 when options were repeatedly looked at to find a way of upgrading the station, without having to close it entirely.

Anyone who uses the station in the mornings will appreciate the need for the expansion. The station caters to around 82 million passengers per year at the moment — more than Heathrow Airport — and this is expected to increase to 100 million by 2020. Add in the possible Crossrail 2 coming through in a couple of decades time, and you have a clear need for a major upgrade of the station.

The easiest and quickest way to show the scale of the works is a couple of before/after images of the layout.

The new section that opened this morning comprises the new northern entrance (at the bottom of the above picture) and the escalators down to the Victoria line.

The new northern entrance aims to encourage passengers to use the entire length of the Victoria Line platform, as the platform will now have exits at both ends. It’s expected that the new ticket hall will suck away around 40% of the congestion in the existing ticket hall, and for those using it, reduce journey times from platform to Victoria Street by an average of 7 minutes.

In essence, those people who can use the new entrance will shave a quarter-of-an-hour per day off their commute, but it’s taken a surprising amount of work to build this new extension.

The new ticket hall

The deep box that houses the new escalators and ticket hall (minus ticket office) is built under the main road, which couldn’t be entirely closed off to allow excavation. So the box was dug in two halves, with the road only half-closed while the works proceeded on one side, then the road was flipped over to the completed half while the rest was dug out.

There was a plan to put the entrance on the other side of the road, and embed it into a new office block, but in the end that site is to be used for residential and a new library, so the entrance is on the probably more convenient side of the road, closer to the offices along Victoria Street.

Soil conditions

The area is notoriously difficult to work in, as the area is made up largely of soft sands and gravels, and they cannot support tunnels or deep box entrances being dug through them unless something is done to stop the gravels collapsing during the tunneling work.

This is not an unexpected problem in the area, for example, when Pimlico station was built, they froze the ground for several months to make it hard enough to dig through, but here at Victoria that was not viable.

In the end, some 2,400 pipes were pushed down into the ground, often at odd angles to avoid sub-surface utilities, and a soft concrete pumped into the ground to stabilize it. Only then could they start the tunnelling, in now safe solid ground.

Of the total cost of the tunnels, which come to around £64 million, half was spent on the jet grouting just to prepare the ground to be tunnelled. It’s a prime example of how so much construction work isn’t building the end product, but the enabling works needed before you can even start on the final construction site.

New tunnels

In total, over 300m of tunnels have been constructed beneath the streets of Victoria, between Wilton Road and Allington Street.

The tunnels link the new entrance over to the Circle/District lines, but aren’t finished yet, so will open in a few months time.

One of the new tunnels runs directly under the existing Circle and District lines and a new roof slab had to be installed to support the railway. Originally this called for a three-month closure of the railway, but an award winning design managed it in just one week, over Christmas 2014.

In addition to that, there is something that people using the tube station wouldn’t have seen — because they weren’t there. Props are normally needed to hold up existing tunnels when new entrances are cut into them, but here at Victoria they developed a brand new way of cutting into tunnel walls to create new entrances, without the use of massive bulky props. At most, people saw a bit of blue hording on the platform sticking out a few centimeters, not the massive tunnel congesting props used in the past.

New Shafts

With a new entrance, comes new emergency access, and here a deep shaft was dug down to the Victoria line, squeezing between the two Victoria line tunnels, with barely inches to spare.

It was exceptionally delicate work, as the Victoria Line tunnels at this specific location were built using an experimental form of tunnel ring, and no one was entirely sure how it would react to a large void appearing next to it.

In addition, the King Scholars Pond Sewer (old Tyburn river) runs right next to the new shaft, which called for a lot of works under the sewer to strengthen its foundations before the new shaft could be dug down beside it.

Although built for fire and emergency access, it has been future-proofed to allow space for a lift in the future.

As with a lot of construction work, we only see the tip of the proverbial iceberg. It took over 11,000 man hours to construct a 24 metre shaft between two live railway tunnels.

Unless there is a major disaster, no one will ever see it.

Existing Ticket Hall

The southern expansion of the ticket hall is still being worked on. That will see the ticket hall roughly double in size and a new bank of escalators added to the Victoria line.

Work on that is expected to be completed in late 2018.

When the £700 million upgrade is finished, Victoria tube station will be three times larger than before, and have gained 9 new escalators and 7 new lifts in addition to the new northern ticket hall.