Drill and Blast and Tunnel Boring Machine are two common types of tunnel construction methods. But roadheaders have been around for many years, getting their start in the coal mining industry. So where do they fit into the equation? According to Hans Greve, a Vice President with Aker Wirth, a manufacturer of roadheaders:
There are three basic ways to build a tunnel: convential drill-and-blast, fully mechanized with a TBM, or the in-between method with a roadheader," Greve said. "The roadheader is used for short tunnels – about 2 to 3 km [or about 1.5 miles] – that have self-supporting rock. But if the rock is too hard, the progress rate drops and the cost of wear and tear increases, so there is a certain point where roadheaders are no longer cost-effective.
[Source: Tunnel Business Online. Image: Tunnel Business Online]