A Railway Tunnel with High Demands
Top architectural concrete surface achieved with regenerated rental formwork
Data & Facts
- Burgberg tunnel and river bridge
- German Railways, DB Netz AG, Berlin
- ED. Züblin AG, Direktion IU Tunnelbau, Stuttgart
- MEVA Systems
- MEVA Formwork Systems, Munich, Germany
Unconventional pouring order
The Munich-Nuremberg-Berlin line is being upgraded for high-speed traffic. North of Nuremberg where the line passes through hillside area, a second tunnel tube is being added to a tunnel built in 1844 and known under the name Burgberg tunnel. MEVA formwork is used to pour the retaining walls, concrete beams and tunnel portals at both tunnel entries, plus bridge abutments and piers close to the southern tunnel entry. The building site is narrow, the workflow complex and the schedule tight. High demands on concrete finish, inclined areas and a board pattern finish added to the challenges. MEVA engineers found ways and solutions to master them.
Abutments with a board pattern and rounded bridge piers
The base slabs for the abutments and the piers for the bridge over the Schwabach river at the southern tunnel entry were poured with the heavy-duty Mammut wall formwork. The system‘s 97 kN/m² allowed the 4.29 m high piers to be done in a single pour.
Special effects achieved with custom-built special forms
The board pattern for the abutments was easily achieved with boards attached to the panel facing. Additional tasks included wooden fillers for the inclined lower sides of the wing walls of an abutment and special forms for the rounded piers.
Top architectural concrete surface achieved with rental formwork
A top concrete surface was specified for a 27.5 m retaining wall, 6.10 m to 10 m high. Yet pouring had to be done not with new but with used rental formwork. Not a problem with MEVA panels and their alkus all-plastic facing. Scratches, nail holes and other damages on the facing can be repaired – even on site between the pours – and the facing is then like new, delivering a top concrete surface from the first to the last pour. Used Mammut 350 panels were regenerated for this job at a MEVA plant and then ganged on site to pour the wall in cycles up to 10 m wide and 2.90 m high. „I am thrilled by the top architectural concrete surface we have achieved with the regenerated rental formwork,” says foreman Mario Thiele “and I am impressed by the stability of the Mammut 350 panels that handled the heavy loads with only few ties.”
Unconventional pouring order
A special solution had to be found for another retaining wall. Here, the 2.38 m high concrete beam that extends horizontally over the bore piles and the concrete shell covering the front of the bore piles had to be poured before – and not after – the concrete shell below it. Hence, the conventional pouring method – climbing cycle by cycle from the bottom to the top – was not feasible. Another challenge were the enormous loads that had to be transferred from the heavy concrete beam that overlaps the bore piles and the concrete shell on both sides. A heavy-duty support structure that would carry the Mammut wall formwork, serve as a working platform, transfer the loads and could be attached to the bore piles was a must and KLK 230 climbing scaffolds were the ideal solution for these requirements. In a second step, the 85 m long concrete shell was poured with an architectural concrete surface using regenerated Mammut 350 panels. The job was accomplished with 10 length cycles and 4 height cycles.
Last but not least: New tunnel portals with a historical look
The portals of the old and the new tunnel tubes are located side by side on either tunnel end. Built in 1844, the Burgberg tunnel is Bavaria‘s oldest railway tunnel and a listed monument whose portals must not be changed. In order to preserve the historical look at both tunnel ends, the new tunnel portals will also receive a historical look. They are poured with Mammut panels on MEP shoring towers. Trapezoidal strips on the panel facing create a joint pattern that fully resembles the brickwork of the old portals.
Fast progress in line with the schedule
Work is done both inside and outside the tunnel tube on both tunnel ends. The new tunnel tube is planned to be operational in 2017 and travel time from Munich to Berlin will then be reduced from 6 to only 4 hours.