Contractors put finishing touches to a section of slip-formed concrete evacuation walkway on the Channel Tunnel Rail Link.
Once the excavation of Channel Tunnel Rail Link tunnels had been completed, they were required to be fitted with evacuation and maintenance walkways – one each side of the track. In addition, these walkways are designed to prevent a train from derailing in the tunnel and so must be immensely strong. To speed up this process, walkways were constructed by using innovative slip-forming techniques. Slip-formed (or continuously formed) concrete was pioneered in America on the Hoover Dam. It uses a slowly moving (or slipping) machine called a paver that lays down concrete in a continuous action and, because the concrete is seamless, its strength in much greater than concrete placed in sections. 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. Fourteen new tunnels were constructed, the longest being the London Tunnel which is long from Ripple Lane to Stratford, after which the line briefly comes to the surface at Stratford Station. Five huge shafts of diameter ventilate the twin bore, single-track tunnels and provide emergency access and evacuation points. The line passes in tunnel under the River Thames and crosses the M25 at Thurrock. 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. The CTRL then negotiates the M25 motorway, going under the southbound and over the northbound carriageway.
Size: 5126px × 3411px
Location: 50m underground, East London, UK
Photo credit: © qaphotos.com / Alamy / Afripics
License: Licensed
Model Released: No
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