Building Tunnels

Building Tunnels

Going Places For much of history, when travelers came across obstacles like mountains, they had a decision to make. Should they go around or over? Both options were difficult-until someone decided to go through! Today, tunnels allow safe and speedy passage through hills and mountains. They also allow people and goods to pass under cities, rivers, and seas. The largest tunnels are amazing examples of the work modern engineers can do.

The History of Tunnels People have been building tunnels for thousands of years. However, for much of that time, tunneling was dangerous and could take many years of hard work. In the 1860s, tunnel building became much easier when Alfred Nobel created dynamite. Easy to use and safer than other explosives at the time, dynamite allowed people to blast through rock in moments. Since then, technology has continued to advance, and tunnels have grown larger and more amazing.

Building Tunnels Today, workers have carved tunnels through rock mountains, under large bodies of water, and below busy cities. Before building a tunnel, engineers look at soil and rock samples. They drill test holes to discover the type of rock they will need to dig through. Once they have this information, they can design a tunnel that will not collapse.

Tunneling usually follows three basic steps: dig, support, and line. First, workers dig part of the tunnel. They may use tools, machines, or explosives. Once part of the tunnel has been cleared, it is time to start step two: support. Any unstable ground must be made stronger to prevent a collapse. How they do this depends on the material the tunnel has to go through. Once the tunnel has been made stable, workers build the lining, or inside, of the tunnel. Using these three basic steps, people have built amazing tunnels all over the world.

Tunnels Through Rock The Seikan Tunnel connects Honshu, the main island of Japan, with Hokkaido. It's 54 kilometers (34 mi. ) long, making it the second- longest tunnel in the world. To build the tunnel, workers had to blast through tons of hard rock.