9 Big Tunnels

Big Tunnels written by John Lockyer

Big tunnels are long, deep holes under the ground. They are used by cars, trains and trucks. Sometimes they have electric lines and water pipes, too. round tunnel Big tunnels are built in different shapes, so they can hold up the rock, earth or water above them.

Rock tunnels have straight walls and a curved top. The arch shape holds up the heavy rock in a mountain. rock tunnel Round tunnels are built through soft ground. Tunnels built under water are round, too. Square tunnels are built under busy city streets.

There are different ways to build a big tunnel. In a rock tunnel, the rock is moved away with explosives. In a round tunnel, a machine cuts through the soft ground. drill A square tunnel is built by digging a big open hole in the ground. The roof is made of concrete and steel.

Some tunnels are dug from each end until they meet in the middle. Other tunnels are dug all the way from one side to the other. laser lights The tunnel-builders use special lights, called laser beams, to keep the tunnel straight.

Building a tunnel is hot and dangerous work. All tunnel-builders wear safety gloves, a hard hat, and hard boots. safety gear Sometimes they wear safety glasses, face masks, and ear protectors.