In the course of the project "Adaptation of Lower and Outer Elbe", the Elbe River will not only be deepened, but a much wider meeting space for large-scale shipping will be built between the Mühlenberger Loch and the Lühekurve. For this reason, the Blankenese blaze line for incoming ships shifts south by 125 m and the nautical facilities have to be adapted and rebuilt. This means that the existing Richtfeuertürme (under-fire and overfire) must be dismantled and replaced by 2 new Richtungs towers in steel construction (OK UF about NN +36 m and OK OF NN about +68.5 m) at new locations on the new directional fire line , The new Unterfeuer is built about 90 meters east of the investor Blankenese in the water and the new upper fire north of the marina Mühlenberg ashore. Subject of this award procedure is the rebuilding of the foundation for the Unterfeuer.
Foundation of Unterfeuer (Lot1):
The construction of the Unterfeuer is to be carried out as a water construction site. In addition to the tide-conditioned currents in the work areas of the lower fire, ship-induced currents also occur due to the large ship traffic. The entire construction site is in the flood-prone area. For the construction site, a flood protection concept must be set up and implemented, in particular for the share of landside work on the abutment of the pedestrian bridge.
All foundation works are to be made vibration-free. For the construction task, an execution plan including statics is to be set up in the case of an order and submitted to the AG for examination.
The foundation of the later steel tower is to be made from a pile slab on bored piles in the water (distance to the shore approx. 20 m). The bored piles with a remaining steel pipe of approx. 13 m length, up to approx. 20 m length, partially inclined up to 6: 1 and a diameter of approx. 80 cm are to be produced by a floating device. In some cases, the bored piles are to be produced by a work platform or other suitable means, which has been founded on separately boring piles to be excavated and to be rebuilt. On the bored pile grid, a pre-fabricated reinforced concrete section with an apron up to approx. NN -2.0 m is manufactured and installed with a floating crane aid. The pile slab has to be designed as a foundation for the tower with a cleanliness layer approx. 0.6 m thick and a reinforced concrete slab approx. 1.5 m thick.
The abutment for the pedestrian bridge is in the embankment area (Ok length about NN +2.5 m) with an OK of about NN +3.5 m with landsseitigem device produce. All equipment for the production of the abutment shall be deposited or landed via the waterway on the embankment. The abutment consists of a steel sheet piling and is to be manufactured vibration-free in the pressing process with a reinforced concrete spar as bridge abutment and pre-hung reinforced concrete precast elements with wing wall.
Water side of the abutment is a scour protection with a revetment with a thickness of about 60 cm and with a mineral filter of about 35 cm thickness produce.