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Channel Tunnel: Construction
built 629 days ago
The UK land sections of the Channel Tunnel involved various cut-and-cover construction techniques including embedded cantilever diaphragm walls, multi-propped walls, piled chambers and deep open cut. At Castle Hill near the portal, an extensive section of cut-and-cover had to be constructed wholly within an existing landslip, calling for close control of groundwater movements and levels plus a carefully phased sequence of top-down construction, including use of heave reducing piles.
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The Channel Tunnel is regarded by many people as one of the most remarkable construction achievements ever; indeed some might say as one of the wonders of the world. However, as much of it is underground, with only the two terminals at either end being obviously connected to the project, it is now difficult to visualise the scale of the project.
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The idea of connecting France and England with a tunnel under the English Channel has been considered since the time of Napoleon, when the first plan for building a tunnel was made. Work on the current tunnel actually started in the late 1970s but stopped because of money problems. Construction began again in 1984 and was completed in 1993. It opened in 1994. It was built with private funds, but treaties were signed between France and England permitting construction of the tunnel.
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The idea of a road tunnel between England and France was first suggested to Napoleon in 1802. It was not until nearly two centuries later that the dream became reality when digging began on the Channel Tunnel or "Chunnel" as it was known in its construction period. The $15 billion link, one of Europe's biggest infrastructure projects to date, was officially opened by President Mitterand of France and HRH Queen Elizabeth II of England, in 1994.
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Consequently the design of these sections was well advanced and the less critical sections of the route from the south portal of the Thames Tunnel to the Channel Tunnel barely started. The refunding and rescheduling of the project turned the initial assumptions on their head. The Section 1 work became the most time critical element of the project and Section 2 was put on hold. Consequently design had to run concurrent with both procurement and construction. Additionally, the plan to have a 6 month pre-construction period to enable RLE to work with the preferred contractors to Value Engineer the project, deal with planning and consents issues and prepare method statements, programmes and all the construction and support systems before commencing on site did not meet the new programme. To cope with this fluid situation the decision was made to adopt the New Engineering Contract option C, a target cost contract, combined with a pain gain share mechanism.
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The line aims to carry its first passengers on 14 November, travelling the 68 miles to the Channel Tunnel in 31 minutes. Significant regeneration benefits have been secured. Over 8,000 people have been employed during construction and it is estimated that the project would have created 50,000 jobs in East London and the Thames Gateway. Post construction benefits are estimated at £10bn including investment in deprived areas around King’s Cross.
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