Cologne Stollen
The Cologne tunnel (in "Cologne construction method") is a tunnel - tunneling in which steel shoring arches serve as support elements that are placed on steel or wooden sleepers. These arches serve as a lesson when driving ("seizing") the metal sheets into the ground. This means that it is a drive according to DIN 18312 excavation class 6/7. The pre-planking boards must be long enough that they always create an abutment in the natural ground in connection with the built-up face. The procedure was developed for the given conditions in Cologne soils.
These drives are mainly used for the construction of sewage systems , but also for the production of media channels ( telephone , cable TV and others) in the sandy gravel of the Rhine terrace. These are non-cohesive soils without cohesion .
Weak point
Until the beginning of the 1990s, the weak point of the Cologne tunneling was the area between the outer edge of the main arch and the seizure that was visible after the main arch was erected. Up to this point in time, this ring-shaped area was built with small-format wooden parts with the help of wood wool. Depending on the storage density and the grain distribution of the existing flooring material, with this type of construction, trickling of the grains, caused by the vibrations when driving in the planking, could not be avoided with absolute certainty. This is now prevented by the fact that the above-described annular surface is non-positively secured by a shotcrete securing device before the planking boards are driven in.
It is essential to ensure that the pre-planking boards are interlocked with one another through a lock shape and that the ridge area is conical. The flexibility of the procedure when driving up obstacles of all kinds is a great advantage .
Possible uses
- Big stones, boulders
- Stones and boulders are only an obstacle at all if they are encountered in the ramming line of the planking. In this case, the pre-seizure is interrupted, the soil excavation is carried out with a new face up to the existing boulder. The boulder can then be removed and the pre-attachment can be further collected. Cavities can be closed by closing them with shotcrete.
- Unexpected encounter of supply lines
- When encountering a crossing supply line, e.g. B. in the roof of the tunnel due to deviation from the exact altitude compared to the planning, the tunnel profile can be varied in its cross-sectional dimensions. The horseshoe profile can be varied up to a frame profile.
- Undermining engineering structures
- In the area of artificial structures that affect the seizure or parts of the tunnel construction, the selected tunnel profile can be converted to a frame profile either from the outset or afterwards. In extreme cases, the frame profile can be braced directly against the lower edge of the artificial structure. The static loads are absorbed by reducing the distance between the arches. Due to the provision of the shotcrete system, cavities and small gaps between arches or frame structures can be closed at short notice with shotcrete.
The Cologne construction method is suitable for all conceivable cross-sectional dimensions and sizes.
Due to the fact that the tunneling does not settle, the method is preferably used for undercutting railway lines, heavily trafficked roads, in the area of influence of foundation loads and for undercutting artificial structures that must be made free of settlement.
Depending on the requirements, the jacking can be carried out with radii up to 7.5 m.