Tunnelling method

There are two basic methods used for tunnel construction: cut-and-cover tunnelling and underground excavation. Cut-and-cover means the excavation pit is open from the surface and is covered after the work has been finished. Underground excavation means the tunnel is cut through rock, under the sea as e.g. the Channel Tunnel between GB and France, e.g. using a Tunnel boring machine (TBM) or the New Austrian Tunnelling Method (NATM).