Every railway line consists of a track substructure and superstructure – usually a ballast bed with the track lying on top. Substructure and superstructure serve to absorb and distribute the forces generated by the weight of trains, acceleration, hunting oscillation, train speed, temperature load and weather conditions. The maximum speed and permissible axle load of rolling stock also depend on them.
The rails lie on cross sleepers on the ballast bed. The ballast bed is flexible and transfers static and dynamic loads evenly to the substructure. The advantages of ballasted track are relatively good noise insulation and absorption of the vibrations created by moving trains.
In the case of slab track, the track does not lie on a ballast bed; instead, it is set in a bed of concrete. This means that sleepers and ballast are no longer required. The slab track system optimally meets the requirements of high-speed traffic: maintenance requirements are low, availability is high, and the track offers a high degree of safety and minimum wear and tear on rolling stock.
It has not yet been decided which system of track superstructure will be used in the Erzgebirge Tunnel.
Within the different options, bridges, flyovers and tunnels are required so that the new line can run under or over existing traffic routes or buildings.
To carry the new line over the parallel tracks of the existing line, a flyover consisting of a reinforced concrete frame is needed. Another solution for a grade-separated junction would be to carry the existing line over the tracks of the new line, also using a reinforced concrete frame flyover. In this case, the tracks belonging to the existing line would need to be re-laid and ramped up and over the new line.
The same principle would apply if the existing line passes beneath the new line in an underpass and vice versa in the event that the new line passes under the tracks of the existing line.
An optimal solution will be developed in the preliminary design phase.