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Lesson 08 – The Incredible Chunnel

Read About the Incredible Chunnel


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The Incredible Chunnel

It took more than six years, required 13 000 workers, and cost over $15 billion. Building the Channel Tunnel (often called the “Chunnel”) was one of the largest engineering projects ever. It is 31.4 km long, and in places it lies as deep as 76 m below sea level.

The Digging Begins

The English Channel is a body of water that lies between southern England and northern France. The Chunnel runs under the English Channel and provides a link between England and France. In 1988, construction began in both countries. The project involved digging three tunnels. Two of the tunnels are for passenger trains and freight trains. These tunnels are each 7.6 m across. The third tunnel, which is just 5 m across, is a service tunnel that workers use for maintenance and to monitor the tunnels to ensure they stay safe.

William Stanley’s Channel Tunnel idea, 1903

Map of the Chunnel

This map shows only the two tunnels for trains. The service tunnel runs between the two train tunnels.

How was it possible to dig such large tunnels? Workers used huge tunnel-boring machines (TBMs), which are also called “moles.” At the front of each TBM is a large disc that has teeth made of tungsten, a very hard metal. The disc rotates to break up the rock as the TBM slowly moves forward. Behind each TBM, a conveyor belt carries away the broken rock. Thanks to TBMs, Chunnel workers were able to dig about 76 m of a tunnel each day.

Chunnel Challenges

The weight of ocean water presses heavily on the tunnels. What keeps the tremendous weight of the water from collapsing the tunnels? As each section of a tunnel was dug, the sides were lined with concrete to make the tunnels strong. The lining also helps make the tunnels waterproof.

Since TBMs started digging in both France and England at the same time, how could engineers make sure that both parts of a tunnel would meet at the same spot in the middle? Solving this problem was one of the biggest challenges of the Chunnel project. Using special lasers and other equipment, workers from the two countries carefully dug toward each other. But the Chunnel was such a huge project that no one knew for sure if the tunnels really would meet at the same spot.

Construction of the service tunnel happened first. On December 1, 1990, the two sides of this tunnel successfully connected with each other. What a relief! A British worker and a French worker shook hands through the opening. Near the end of May 1991, both ends of the second tunnel were joined. About a month later, the two sides of the third tunnel met in the middle.

There was still lots of work to do. Train tracks, electrical systems, fireproof doors, a ventilation system, and more had to be added. As well, train terminals (stations) needed to be built in England and France at the ends of the Chunnel.

To remove any water that got into the tunnel system, three pumping stations were built under the water, as well as one on the British shore and one on the French coast. A special vehicle was designed to zoom along the service tunnel. This vehicle is used for maintenance on the Chunnel, and can quickly reach the site of an accident or emergency.

The Chunnel officially opened on May 6, 1994.


Chunnel train car, National Railway Museum, York

The Chunnel Today

As many as 400 trains pass through the Chunnel daily. More than 21 million passengers take the 35-minute train trip between the two countries each year. An organization of American engineers has included the Chunnel on its list of “Seven Wonders of the Modern World.”

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