With a population of about 617,000, the North Rhine-Westphalian capital Dusseldorf is the seventh largest city in Germany and the second largest city in North Rhine-Westphalia after Cologne. The UpperNord Tower, a modern residential development, is currently being built to meet the growing demand for living space and will become another landmark of the Dusseldorf skyline. Located at the northern entrance to the city, the 120m high residential tower will be the tallest of its kind in Dusseldorf and the third tallest skyscraper in the city. The UpperNord Tower will provide around 29,200 m² of floor space over 36 floors. The majority of this space will become 432 planned residential units. The plans also include a variety of restaurants on the ground floor, a three-story underground parking garage and a five-story hotel, which will adjoin the building.
The client, UpperNord Tower GmbH & Co. KG, a member of CG Group AG, contracted the "UpperNord Tower excavation pit" Joint Venture, which consists of BAUER Spezialtiefbau GmbH and Gerhard Kliemt GmbH, to carry out a variety of specialist foundation engineering and earth works as well as construct the dewatering system for the impermeable retaining structure of the UpperNord Tower.
Around 6,000 m² of shoring wall for the retaining structure is being constructed using the low-vibration mixed-in-place (MIP) method. The key feature of this method involves mixing the existing soil in-situ with a binding agent. A triple continuous flight auger is used to produce a homogeneous soil concrete. Using the embedded soil as a building material conserves resources and has economic and ecological advantages over conventional shoring. Drilling depths of up to 23.5 m, which would not have been possible with the former MIP equipment several years ago, present a special challenge. An RG 25 S from RTG Rammtechnik GmbH, a subsidiary of BAUER Maschinen GmbH, is used for the MIP work. In addition, an RG 16 is being used to install 700 t of reinforcement in the form of inserted double steel beams, each of which is 22 m long and weighs up to 5.4 t. This reinforcement is another special feature of the construction project.
"In order to secure this impressive excavation, an additional 5,300 m of anchors with three to six strands and drilling lengths of up to 24 m will be installed," says Tim Erkens, operations manager at Bauer Spezialtiefbau. A KR 806 from KLEMM Bohrtechnik GmbH is being used in the anchoring work. In addition, the second layer of ground anchors is being constructed to protect against pressurized groundwater. "Due to conditions imposed by the city of Dusseldorf, some of the anchors will have to be removed," says site manager Moritz Hahn.
The project also includes the scheduled removal of obstacles using a BAUER BG 40, dewatering for nine months and excavation of around 57,000 m³ of soil, including disposal by Gerhard Kliemt GmbH. The "UpperNord Tower" Joint Venture’s specialist foundation engineering and earth works project began in December 2018 and is expected to be completed by the end of June this year.