An important part of the reconstruction of metro line M3 is the renovation of the entire track, and an interesting and spectacular section of these works is to replace or repair the special track units, the so-called detours.
One of the contractors made a video about the work on these sections of the reconstruction. It can be seen that the new iron parts and structural elements of the detours are first assembled than fixed precisely against displacement. Following this the installation is carried out by concrete arriving via pipeline from the surface. After careful works the detour tracks are fixed to the concrete foundation with the necessary depth. After concluding the concrete - 2-3 weeks depending on the conditions - the structure is completely ready for use.
This abovementioned process is called „top-down” technology, with the advantage that - after concluding - the structure is completely finished, no after-assembly, setting, drilling or engraving is required.
A frame from the video