Tunnel construction

Tunnel construction is an part of engineering which is about buliding tunnels. There are different ways to do this:

• If the tunnel is not deep underground, the simplest way to construct it is an open put. A hole is dug, and the walls at the side are built. At the end, the tunnel gets a roof.
• An alternative to this is to first bulid the walls and the roof, and then remove the material as needed. This is also known as cut-and-cover.
• Especially when building tunnels in mountains, or deeper underground there are special tunnel-boring machines. They bulid tunnel with a cicular cross-section.