Tunnel visionaries The Crossrail project

TUNNEL VISIONARIES

The construction of Crossrail is the largest infrastructure project in Europe and London’s first new railway for over 20 years. It will provide for the first time direct links from Berkshire in the west and Essex in the east into Heathrow, central London and Canary Wharf. Robert Williams reports.

Crossrail will provide a new underground line through central London, running 118km (73 miles) from Maidenhead and Heathrow in the west through 21.5km of new twin bore tunnels through central London and on to Canary Wharf, Woolwich, Abbey Wood and Shenfield in the east. There will be new underground stations at Paddington, Bond Street, Tottenham Court Road, Farringdon, Liverpool Street and Whitechapel.

The new railway is designed to initially accommodate 10-carriage trains, but construction is making provision for longer trains in the future, which may well be necessary as it is anticipated that over 200 million passengers will use Crossrail in the first year of operation.

Proposals for the construction of a new East-West rail link across London are not new. They were first drawn up shortly after the Second World War. Since then the idea resurfaced from time to time, but nothing happened until the late 1980s, when the original Crossrail scheme was developed. Meanwhile, London continued to grow, both economically and physically, placing everincreasing demands on its infrastructure.

Crossrail is in many ways identical to the Réseau Express Régional (RER) lines in Paris. It will bring passengers in from the suburbs to the heart of the city and continue out to the other side. RER lines absorb many passengers who might otherwise board congested metro lines, which can then more readily accommodate shorter city journeys without high volumes of commuters loading and unloading at each main line terminus.

Crossrail is the biggest engineering project in Europe. Main construction works for Crossrail began in 2010, and some preparatory work was carried out in 2009 at the major stations including Tottenham Court Road, Farringdon and Paddington.

At the heart of the project is the construction of a new 21.5km (12 mile) tunnelled route across London. This includes the branch of the eastern end to Shenfield and Abbey Wood. Portals for the main tunnels have been built at Royal Oak to the west of Paddington and in the east at Custom House and Pudding Mill Lane.

All of this adds up to 42km of bored tunnels located below the busy streets of London.

The tunnels will weave their way between existing underground lines, sewers, utility tunnels and building foundations from station to station at depths of up to 40m. The first two tunnel boring machines (TBMs) are about to start out on their journey from Royal Oak towards the west of Farringdon station.

The TBMs, built in Germany, each weigh 1000 tonnes and are longer than a football pitch. In March, the first of eight of these giant machines will start burrowing under

central London. They were built in Schwanau, Germany, by Herrenknecht. When the TBMs start work, they will operate 24 hours a day, grinding through the London clay at a rate of 100m a week.

The six million tonnes of earth they will remove will be transported to Wallasea Island in Essex, where they will be used to create a new nature reserve.

As the machine bores out the tunnel, it lines it with concrete segments. Production of those segments is at a purpose-built factory in west London. Each weighs almost three-and-a-half tonnes and takes a month to set solid. Two more factories will be built, and between them they will produce a quarter of a million concrete segments to line the Crossrail tunnels.

Each TBM will be operated by ‘tunnel gangs’ of 20 people working in shifts. Those working underground are being trained at a new Tunnelling and Underground Construction Academy at Ilford in east London.

Later in the year two further tunnel boring machines will be put to work in Docklands. They will head under central London towards the east of Farringdon. Further shorter tunnel drives will take place in the Royal Docks and east London

New stations

Teams of dedicated construction workers will be working 24 hours a day to complete the tunnels for Europe’s largest civil engineering project with thousands of others employed to upgrade the existing rail network and build major new stations along the central section of the route.

The new stations need to cope with large numbers of passengers throughout their life, be easy to navigate and able to endure wear and tear. There will be new stations at Paddington, Bond Street, Tottenham Court Road, Farringdon, Liverpool Street, Whitechapel and the Isle of Dogs. The station platforms will be 250m in length to accommodate 200m trains that will pass through each station, as well as enabling longer 240m trains to operate in the future as passenger demand increases.

Crossrail is following in the footsteps of the Paris RER lines in other ways. When routes were built, planners always sought to cater for future growth. This is partly why city centre tunnels and stations are being built to the generous dimensions of the RER, with long, wide platforms.

Because headways between trains in the city centre are very tight and the station dwell time is very short, high-capacity trains will be used, with the ability to load and unload passengers as quickly as possible. Stations are also designed to ensure that passengers can move to and from street level or interchange with other transport modes quickly and safely.

Crossrail’s brief is to provide the transport capability to cope with London’s forecast population and economic growth. With Crossrail services taking over from many of the trains routed into the main line stations, capacity will be freed at existing termini such as Liverpool Street and Paddington. The first service trains are expected to run in 2019, effectively adding 10 per cent to the capacity of London’s public transport. For those used to sardine-like conditions on the Tube, the first trains can’t come soon enough. n