G eorge Ranson and Bob Waller describe the Channel Tunnel as
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"just another job". To the rest of us it is the biggest European construction project ever.
Work on the central service tunnel started in December 1987, and as transport manager Waller is keeping this vast undertaking in line with a fleet of 140 commercial vehicles. Ranson is plant manager, and some of his hardware is truly awe inspiring.
Take the tunnel boring machine (TBM), for example, which is 215m long and weighs 600 tonnes. It was assembled in the 422m of tunnel left over from the 1974 Channel Tunnel project and is now grinding its way towards France. "The going is soft right now,says Ranson, "through chalk marl. On the French side it is much tougher: they're going through solid chalk."
The TBM looks like something out of a science fiction movie. Its head is a giant rotating circle studded with a cross of meanlooking "teeth-. As the head moves round. rock and marl fall back through the cross of teeth to be taken away through the belly of the machine by conveyor. As the TBM excavates the tunnel it propels itself forward by pushing with hydraulic rams, leaving prc-cast concrete tunnel walls in place behind it.
The chalk marl spoil is carried out of the tunnel by rail and conveyors to be placed in fill lagoons behind specially constructed sea walls at Shakespeare cliff. "We're using the spoil to reclaim about 45 acres along the shoreline here," says Ranson.
In all some nine million tonnes of spoil will be excavated and moved by conveyor to the reclamation sites. To illustrate the vast scale of the project, imagine that 38-tonners were to be used to carry it away in one go. each 15.5m rig taking a 25-tonne payload. The convoy would stretch for some 5.500 kilometres... The blue-grey marl through which the British end of the tunnel is being bored feels like plasticinc and. usefully, is impermeable to water. The service tunnel is some 45m below the seabed: at its deepest point. about 13km out from Dover. it will be 115m below.
When completed the fixed link will comprise not one but three tunnels: two 8.5mdiameter rail tunnels, linked at 370m intervals to the 5.7m-diameter service tunnel now being excavated. On I October work started on driving that tunnel the 8.5km back to Folkestone. At each end of the link giant TBMs. some far heavier than the "baby" already in action. and costing up to £9 million apiece, will be set up to bore out to sea and hack to the on-shore termini. That's a total of 12 separate excavations to be linked up into the three Channel tunnels, with an aggregate length of about 156km.
Trucks and vans are playing an essential part back on the surface. Different parts of the job are time-critical at different times, says Ranson: "We will bring all of our truck mixers in when there is a big pour needed, for instance.
A trio of 38-tonne artics is kept busy moving rails from the project's storage yards near Ashford. Kent to the Shakespeare Cliff site. Tippers swirl round the terminal site near Folkestone like bees round a honey pot and nine Leyland Daf Constructor tippers are on the move at the Shakespeare site 24 hours a day. "Gradeability and torque were important when we specified the mixers,says Waller. "We drive the mixers straight down into the tunnel, and the ramp's quite steep.
Access roads around the site are good, if occasionally steep. "We upgraded the ones we knew we would need,says Ranson.
"We've been lucky with tyres, too," adds Waller. "Marl is soft. When you start working into chalk you often get flint, and that is tough
on tyres." He plans to run the Constructors fol about six years before selling them and witi tunnel construction due for completion in 199: they should see out the job.
About 4,000 people are working at the LIE end on the tunnel project; at the constructior site itself and at other bases around the Soutl East. Another 2,000 arc involved at the French end, and the projected total cost is E cool £4.6 billion.
It's all a far cry from the first attempt at a Channel Tunnel. when an exploratory 30m shaft was sunk on the coast near Dover by Colonel Beaumont and Captain English of the Royal Engineers, funded by £6,000 grant from the South Eastern Railway Company. Mind you, that was a lot of money in 1880...