Concrete lining segments being transported by conveyor to build area inside the Boring Machine on the Channel Tunnel Rail Link
As a Tunnel Boring Machine excavates a passage under the ground (unless this is through hard and non-faulted rock), the tunnel must be lined to prevent collapse and the ingress of water. This lining is usually made of prefabricated and steel reinforced concrete segments (made watertight with special gaskets) that will create a support ‘ring’ or ‘tube’ in the bored tunnel. As most tunnels are designed to have an expected life of 100 years (or more) and are being increasingly excavated in areas of difficult geological conditions, these lining segments must be made with great precision and accuracy from the highest quality materials. The supply of segments dictates the speed of the tunnel’s advance, so, on large tunnel projects, they are often manufactured on the tunnel site in special fabrication plants. As every tunnel is unique and tunnels don't run in conveniently straight lines, linings must be adjustable to allow changes in alignment and levels without compromising the fit of the concrete segments or gasket seals. The £ billion Channel Tunnel Rail Link (now High Speed One) was built between 1998-2007 and partly funded by the European Union, it forms a section of the Trans European Rail Network. It is basically a French-style high-speed rail line linking London with the Channel Tunnel, the Eurostar trains were developed on proven technology from the French TGV high-speed system. Stations on the CTRL are the existing Ashford International and new stations at Ebbsfleet and Stratford. The line ends at the rebuilt St. Pancras. For the Thames crossing (a 3km twin-bore tunnel), the line drops 1 in 40 down under the river and then climbs 1 in 40 up, curving at the same time. In total, the new line took 9 years to build and comprises 109kms of new track, 152 new bridges, 3 viaducts, 14 new tunnels with a total length of 26kms (25% of route), 2 new and 2 refurbished stations and the project created 8000 new construction jobs. And Eurostar travels at 300kph!
Size: 2430px × 2430px
Location: Under River Thames between Swanscombe and Thurrock, London, UK
Photo credit: © qaphotos.com / Alamy / Afripics
License: Licensed
Model Released: No
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