© Eurotunnel
TUNNEL VISIONARIES For hundreds of years, probably since the English Channel was created after sea levels rose, schemes have been made to span the 21 miles of water separating the UK from the rest of Europe with tunnels and bridges. Robert Williams celebrates 20 years of the Channel Tunnel.
T
he first plan in recent times was developed by Albert Mathieu Favier. In 1802 the French mining engineer proposed to tunnel under the English Channel with illumination from oil lamps, horse drawn coaches and an artificial island mid channel for changing horses. Napoleon supported the plan but the British vetoed it, fearing that he wanted to build the tunnel in order to invade England (although one would think that soldiers emerging from a tunnel would have been rather easy to stop…). There were many other plans that never left the drawing board until, in 1973, Prime Minister Edward Heath and French President Pompidou signed an agreement to push ahead with a Channel tunnel. Work actually started on this tunnel, although it was soon abandoned. Then, in 1984, French president Francois Mitterrand and UK Prime Minister Margaret Thatcher jointly agreed to construct a link across the Channel. There were ten proposals, including various tunnels and bridges. The proposal that 14 Industry Europe
won was the plan for the Channel Tunnel, submitted by the Balfour Beatty Construction Company (this later became Transmanche Link). The tunnel would be the longest undersea tunnel in the world with 38km out of the 50km length under the sea. The geology of the Channel was examined and digging began simultaneously from the British and the French coasts, with the finished tunnel meeting in the middle. On the British side, construction began near Shakespeare Cliff outside Folkestone; the French side began near the village of Sangatte. The short stretch of tunnel dug in 1974 was used as the starting and access point for tunneling operations from the British side for today’s tunnel. Huge tunnel boring machines, (TBMs), cut through the chalk marl, collected the debris, and transported the debris behind it using conveyor belts. As the TBMs bore through the chalk, the sides of the newly dug tunnel had to be lined with concrete. This concrete lining was to help the tunnel withstand the intense pressure from above as well as to help
waterproof the tunnel (although the tunnel is, on average, 40metres below the sea bed). The project used eleven boring machines each of which were the length of two football fields and capable of chewing though 250 feet of earth a day. On the British side six were lowered into an excavation near Dover’s Shakespeare Cliff. Three were pointed toward the channel to make the underwater portion of the tunnel and three toward the mainland to make the tunnel approaches. In France the same thing was done with five machines at an excavation near Sangatte. The Channel Tunnel is actually two parallel railway tunnels and a third, smaller, service tunnel that is used for maintenance, including communication cables and drainage pipes. One of the most challenging tasks on the project was making sure that both the British side of the tunnel and the French side actually met up in the middle. Special lasers and surveying equipment was used; however, with such a large project, no one was sure it would actually work.
