The first construction stage saw the installation of the first 73 micro-piles on the third basement floor of the building at the end of 2019. The second stage began at the start of 2021. Additional temporary and permanent anchors were produced by April 2021. A total of roughly 2,000m of micro-piles and 750m of anchors have been installed so far. There will be one more stage, making three in total.
Challenging conditions: low working heights and possible presence of explosive ordnance
The installation of the micro-piles was hampered by complex conditions on the construction site. The available working height proved to be very limited at just under 3m. Drilling points were sometimes difficult to reach because it was impossible to remove the columns needed for the false ceilings at higher levels. In addition, the distance from the drilling axis to the existing walls of the building was very small, in some cases only 25cm. One particular challenge was that the cramped conditions meant that it was impossible to guarantee the absence of explosive ordnance in some areas. The drilling rig was upgraded for pressure-sensitive drilling in these zones. The suspected areas were subjected to test drills under the supervision of an expert certified in accordance with section 20 of the German Explosives Act (Sprengstoffgesetz) in order to obtain a drilling permit. Stump-Franki has a special permit for this in accordance with section 7 of the Explosives Act.
Tough logistical challenges
The drilling rig, which was individually adapted by Stump-Franki, had to be hoisted into the building by crane through a narrow opening. The confined spatial conditions of the WDR building, which is located in the centre of Cologne, the very limited set-up space available on the construction site and the fact that several trades were working at the same time meant that high-precision logistics were critical.
Effective and targeted communication
Potential obstructions and costly downtimes were avoided thanks to regular and consistently excellent coordination with the client, Kögel Bau GmbH, and the other trades working at the same time. Stump-Franki Spezialtiefbau was able to successfully carry out the work as agreed thanks to its meticulous preparations, its highly experienced specialist in-house staff and its own special equipment.