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The challenge that inspired engineers to solve a major problem in the train stations of Europe’s biggest infrastructure project

What springs to mind when you hear the word Crossrail?

If you’ve been following the news you might be thinking of £1.4 billion bailouts, long delays and issues with staff morale.

But this is Europe’s biggest infrastructure project, increasing central London’s rail capacity by 10%. It will be the biggest increase since the Second World War.

So while it’s disappointing that it’s behind schedule and over budget, it’s not particularly surprising. Right now, Elizabeth Line trains are running from Shenfield in the east, to Liverpool Street, and from Paddington to Hayes & Harlington in the west.

But the full line, running from Reading and Heathrow in the west, through central London and out to Abbey Wood and Shenfield in the east, isn’t expected to open now until 2020, at least a year behind schedule.

With the project coming in at £17.6 billion (so far) and with between 6000 and 7000 people working on it, not including supply chain workers, it’s a massive undertaking.

Some of the challenges of this project

The new line needs to be fully integrated with London’s existing transport network, which is no mean feat. Workers need to create 42km (26 miles) of new tunnels and link them up with existing ones.

Ten new stations are being created, and 30 others are being upgraded.

But what’s interesting from a structural point of view is how the new tunnels are being integrated with the old ones. It’s not just tunnels for the trains to travel through that are needed. There are also tunnels for passengers to walk through, tunnels for station staff, and maintenance tunnels too. With all of these different tunnels, each station is a large engineering project in its own right.

Without wishing to state the obvious, one of the biggest challenges is the geometry. Rather than the right angles and straight lines of most buildings, engineers are dealing with cylinders of differing diameters.

These cylinders often come together at strange angles, creating a complex 3D geometry that can’t always be communicated via drawings. An additional challenge is that the tunnels don’t conform to strict engineering tolerances or permissible limits of variation in size.

This makes it very difficult to use a standard fixing system, so the civil and structural engineering firm involved in fitting out three of the most complicated stations has designed a new system for making tunnel interior cladding. To be clear, this is for the tunnels for people, rather than the tunnels for trains.

The original design used a steel fixing system, attached to the wall of the tunnel, which in turn would have panels attached to it. The fixing system had to be very complex, to take the weight of the panels.

Can we simplify this?

So Bryden Wood – the firm involved – looked at reducing the thickness of the panels so they could reduce the support structure needed. The solution they came up with made it much easier to seamlessly cover tunnels of different geometries.

The panels had to be subjected to bomb blast tests and physical tests to ensure they were still fit for purpose despite being thinner. The team managed to reduce the weight by two thirds, meaning the panels could fix to a single rail. The rail was positioned with a laser line, so even if the tunnel geometry varies, the cladding is independent of these variations.

The system created here solved a difficult problem, but also dramatically cut costs. These kinds of breakthroughs are at the core of engineering and being innovative in engineering solutions, and is one of several reasons why I am so passionate about what I do. This solution means that the tolerance problems are now irrelevant. Part of being an engineer is to always be looking for innovative solutions and looking beyond the obvious and that is why one of our Company Values is “Innovate and Challenge – There is a better way – We are Solution Focussed.”

I’m sure there are numerous other examples of innovation and problem solving on this project, but this one in particular caught my eye.

The benefits of the project as a whole will be huge, not just in engineering innovation, but in the impact on the capital. Anyone who lives and works here in London knows that our transport network is badly in need of greater capacity and, in places, an increase in speed.

Crossrail will allow residents of Abbey Wood in south east London, to get to Heathrow in 51 minutes – a full 42 minutes faster than they can right now.

Whenever it opens, this project will be transformational.

I hope you’ve found this an interesting read – I’d enjoy hearing your thoughts and comments. And if you need assistance with the structural elements of a project you’re working on, please do get in touch.

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