Before the advent of tunnel boring machines, drilling and blasting was the only economical way of excavating long tunnels through hard rock, where digging is not possible. Even today, the method is still used in the construction of tunnels, such as in the construction of the Lötschberg Base Tunnel.

The decision whether to construct a tunnel using a TBM or using a drill and blast method includes a number of factors such as:

• Tunnel length


• Managing the risks of variations in ground quality


• Required speed of construction

The required shape of the tunnel.