More safety for large diameters on short distances
When tunnels with large diameters are realized across short distances, the pipe arch method is the safest and most efficient technique. Typical application examples are crossing beneath railway lines or the construction of new metro stations. First of all, a number of microtunnelling drills are carried out, during which mostly steel pipes are introduced. In this way, a kind of "protective frame" for the later tunnel is created. Thanks to a sophisticated folding mechanism, the machine can be drawn back into the launch shaft after these short drills and can get to grips with the next tunnel from the same side.
Depending on the geology, where required, additional icing equipment is installed into the steel pipelines; these freeze the underground, thereby creating a stable "water-soil skin". These protective measures create the best prerequisites for excavating and securing the actual tunnel using mining techniques. Depending on the project requirements, the jacking frame can be fixed to either a horizontally or vertically movable platform in order to facilitate the large number of drills. The advantage of this construction method consists mainly in the fact that the later tunnel can be excavated without settlement in the geology. Changes in altitude in the rail tracks can thus be avoided.