To allow the new Dresden–Prague line to cross the Ore Mountains (Erzgebirge) on the German-Czech border, a cross-border base tunnel is required.
The tunnel will be at least 25 km in length, at least 14 km of which will be on the German side. This will be Germany’s longest railway tunnel.
On double-track lines, long and very long tunnels (> 20 km) must be built as parallel single-track tunnels if unlimited mixed passenger and freight operations are planned.
In emergencies, the escape route for passengers and crew and the access route for emergency services is via the neighbouring tunnel tube. Cross-passages provide access between the two tubes.
The type of construction depends on the geology of the rock as well as on the height of the overburden, i.e. the mountain or hill being tunnelled through. Tunnels can be built by the cut-and-cover method or by using mining techniques. In the case of mined tunnels, the tunnel tubes are excavated step by step. This is achieved either by blasting or with the help of a special tunnel boring machine or excavator.
The blasting process involves laying and manually detonating explosives. In tunnel boring, by contrast, a tunnel boring machine (a large machine with a special cutting shield) is advanced through the tunnel under pressure. Behind the cutting shield, the engineers then immediately assemble concrete segments to form a ring, creating the shell of the tunnel. The excavated material is transported out of the tunnel by pumps and conveyor belts.
When a train enters a tunnel at high speed (> 200 km/h), the micro-pressure waves that it pushes in front of it are compressed. These pressure waves then travel ahead of the train at the speed of sound and produce an audible boom when they escape at the tunnel mouth. In single-track tunnels, this phenomenon is reinforced by the narrow tunnel cross-section. Unlike in double-track tunnels, the pressure waves are unable to disperse.
The solution is to install hoods with vents at the tunnel entrance portals. This allows a large part of the pressure waves compressed at the tunnel entrance to escape upwards. As a result, the micro-pressure waves travelling ahead of the train are minimised to such an extent that there is no sonic boom at the other end of the tunnel.
Safety and protection from fire and other disasters are the top priority in rail transport, especially in tunnels.