Channel Tunnel or European Tunnel [RAE]

♦ Drilling operations began for this 50 km long tunnel linking Britain and France under the seabed in 1987, as each country dug from its coastline to reach the middle of the road and it ended in 1993.

It consists of two main tunnels for trains in addition to a service tunnel and 245 transit lanes for escaping in the event of a disaster or fire outbreak, in addition to ventilation outlets to release the air pressure created by high-speed trains.

The length of the giant drilling machine was 200 meters and weighs 1100 tons. 12 British and French drilling machines were used, as the daily productivity of this machine was 75 linear meters or 36 thousand tons of rocks per day .. Hundreds of concrete slabs were shipped to lining the roof during digging. The size of the slab was It is about the size of a regular car, weighs three times its weight, and is made of granite for durability.

◾️ Because of the fear of not meeting the drilling paths, the survey system that is used in regular surfaces has been replaced by a space-in-space system by means of the laser to be more accurate .. A geologist was also assigned to determine which rock layers are the best to pass through the drilling so that it must be waterproof to prevent The floods are compact enough not to collapse during digging and are blue chalk rocks.

In 1988 the catastrophe occurred on the British side, as sea water leaked into the tunnel, so the chief engineer worked to replace the concrete ceilings with other metal ones as a basic solution, but the water leak caused a malfunction in the drilling machine, as well as a water leakage occurred on the French side, but there was no malfunction in their drilling machine because Isolated against water.

The British faced another problem, which is storing the reinforced slabs, as the storage area next to the tunnel is small due to the hills, so they used the waste of digging the tunnel to fill an area of ​​the sea in order to enlarge the storage area, as 17 million tons of waste were thrown into the sea.

The British first reached the meeting point and introduced a small drilling machine to penetrate the French side and the two sides met successfully

THANKS [ RAE ]