The Channel Tunnel

1. History

[MB1] 2. Design and Engineering

The final scheme consists of two running tunnels, one service tunnel and a piston relief duct. The total length of the tunnel is 50 km. The piston relief duct is used to keep the airpressure in both tunnels equal. These pistons are placed every 250m. Every 375m there are cross passages to connect the service tunnel with the running tunnels. The air pressure in the service tunnel is higher than in the others to prevent, in case of a fire, that smoke can infiltrate it. In the running tunnels is a coolingsystem, because the system is constructed to handle a train every 1,5 min and every train produces heat. The main type of rock was chalk. This material is waterproofed and easy to dig.

3. Construction of the tunnel

The tunnelling involved 12 separate drives (tunnelborings): three underland tunnels on each side and the three underseatunnles, which were started on both sides. On the French side there have been some serious problems with the rock. At this part it was a water-bearing rock and the tunnel boring machines had to work at a slower rate and in sealed mode under water pressure. For these 12 tunnels only one of the tunnel boring machines was used a second time. The tunnel boring machines were about 210 meters long and weighed over 1000 tonnes. In operation, the cutting head of the tunnel boring machine was thrust forward to the rock face by hydraulic operated rams pushing against a gripper section behind it. These gripped the walls with hydraulic pads. The spoil was transported with conveyor belts backward and large concrete lining sections foreward. They were manned by four teams of 44 operators in eight-hour shifts. They advanced about 300 meters each week. The record was made in March 1991 with 428 metres in one week. The cross passages and the Piston relief duct were made manually.

One of the mayor problem was the disposal of the spoil. On the British side, they had to dispose about 4 million cubic meters and on the French side about 3 million cubic meters. The British build with the spoil an artificial cliff, called Lower Shakespeare Cliff. In France, the spoil was crushed and mixed with water to form a slurry. This was pumped to an artificial lake. As the slurry dries the area will be landscaped to blend into the surrounding hills.

There are two crossovers at each side of the tunnel. They are placed about 10 km from the beginning of the tunnels. They are the largest artificial undersea caverns ever built.

The first breakthrough was a probe which was about 5 cm wide and 100 meters long. The two tunnels were only 10 cm apart vertically and 50 cm apart horizontally. Adjustments were made and the real breakthrough took place on 1 December 1990. After this breakthrough the British tunnel boring machines were buried in concrete whilst the French machines were dismantled and removed from the tunnel.

After the completion of the boring work the track and the equipment had to be installed. The tunnel would be, with about 24 trains per hour, one of the most frequently used rail links in the world. Due to that the track had to be build very carefully. They laid 195 km of track, 95 km of which were laid at the two terminals.

Alongside the rail track several other systems were installed including the power and lighting, signalling and communications, fire mains and detection systems.

The Eurotunnel has adopted the signalsystem "cab signal", which is already used by the TGV. This system displays the information in the cabin, because it is nearly impossible to read a sign at a speed of about up to 500 kph. The system can handle up to one train per 2 1/2 minutes.

The final phase of the project was the testing of the tunnel under "real conditions". They tested it during a period of nearly one year.

4. Terminals at Folkestone and Calais

For the construction of the terminal at Folkestone several million cubic meters of sand were necessary. It has a total expansion of 346 acres. Calais covers about 1186 acres. The main controllcenter is in Folkestone whereas the servicecenter is in Calais. There have been strong efforts to protect nature. For example trees and grass have been transplanted before the building of the terminals was started. Afterwards they were replanted.

5. General information

The Le Shuttle wagons are used to carry trains from and to the continent. There are three different types: a double decker shuttle carrying cars, motorbikes and bicycles; a single deck shuttle for carrying coaches, and other vehicles above 1,85 metres in height; and another single deck shuttle for carrying fully loaded road freight vehicles.

It takes about 35 minutes from platform to platform, with 27 minutes in the tunnel.

The service works on a 'turn up and go' basis so there is no fixed check-in time. Drivers of cars, coaches and heavy good vehicles can expect four departures per hour. It is guaranteed that there is at minimum one departure per hour.

All shuttles have two 7600 HP locomotives with one diesel-machine for emergency- cases.

There is a connection between Folkestone and Waterloo and between Calais and Paris and Brussels. The train needs for Brussels-London about 2 hours 10 minutes and Paris-London 2 hours 30 minutes.

6. Words