6.1 A History of Tunnels
Read the text carefully about tunnels
A tunnel is a passage built underground to allow a road or railway to go through, for example a tunnel that goes through a hill. Tunnel building has been carried out for a long time since the Babylonians in ancient Baghdad, who around 2180 B.C built a tunnel under the Euphrates River. It is believed that they did this by first diverting the river and then built a tube-shaped tunnel of bricks covered it. When this was done, they let the Euphrates River to flow back into its normal channel over the tunnel.
Another method of tunnel building is one that involves cutting through a big rock until a large tunnel has been formed. In the old days, this was very difficult to carry out. Today, this job has become much easier since the invention of power tools that dig through the rock hundreds times faster than a man can with a primitive hacking tool. Still another method of cutting a tunnel involves blasting the hole with explosives. The inside of the big hole, that is the tunnel is lined with metal frames and the bricks, tiles or something of that sort. This will help strengthen the tunnel and will stop it from caving in.
Underwater tunnels which are common now required more thought in building. Marck Isambard Brunel developed a way of building tunnels under water and in soft sandy soil. His idea was building a shield-something like a huge, strong tin can-that could be rammed into the sand to hold it in place.
6.1 A History of Tunnels
This is followed by the placement of permanent rings of metal or framework. The rings are placed one by one. As each ring of metal is successfully placed at the starting point of the 'tin can shield', they are used to push the shield forward until one comes to the end of the tunnel.
Today, tunnels are big enough to have trains which are called subways going both ways. Some tunnels have double-storey roads or tracks. The next time you drive through a mountain or under a river or ride in a subway, stop and think about the ancient art of tunnel building. Imagine a trip to the world's most interesting tunnels starting with the Mont Cenis Tunnel in the Alps. The 8-mile long tunnel was opened in 1871 and was probably the first tunnel in the world to have been built with compressed-air drills.
In New York City, you could go on an entire tunnel tour without ever leaving the city area. The oldest of the tunnels linking New York City and New Jersey is the Holland Tunnel. London, Paris, Moscow and many other older cities have elaborate tunnel systems of subways. But for a really exciting railroad ride, you might want to go under the sea from the island of Hokkaido to the island of Honshu in Japan-by tunnel. The Seikan Undersea Tunnel is almost 34 miles long. Another exciting and state-of-the-art undersea tunnel is the Euro Tunnel that connects Great Britain to France. Undersea and river tunnels are now commonly found in many other big cities, such as Shanghai and Boston.
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels
6.1 A History of Tunnels