TWENTY YEARS OF THE CHANNEL TUNNEL

feature . With every system in the tunnel duplicated in the two nations : drainage , ventilation , power supply , railway control ; in the event of one system failing , the duplicate steps up and runs the whole tunnel independently .

Three challenges Despite its reputation as a groundbreaking engineering project , construction was not without setbacks . Sir Alastair Morton headed up an iron-willed leadership driving development to completion , overcoming several issues , identified by Keefe , which ultimately saw costs rise above £ 4.6bn .

“ Firstly , the design wasn ’ t totally finished when construction began , and the regulatory body put in place was a combination of French and

Geological profile along the tunnel as constructed . For most of its length the tunnel bores through a chalk marl stratum ( layer )

Typical tunnel cross section , with the service tunnel between twin rail tunnels . Shown linking the rail tunnels is a piston relief duct , necessary to manage pressure changes due to the movement of trains

British regulation . “ The AGC kept applying new regulations for safety and pushing

the standards further , so in the end things like the rolling stock , which had been specified at the beginning , had to be modified during manufacture , and additional safety fail-safe systems put in . The additional cost added was quite significant through that part of the process .

“ Combined with that , the British railways board and SNCF made traffic

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