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DRK Clinics Berlin, Westend

Facts and Figures
Company PORR Spezialtiefbau GmbH
Principal Wolfgang Bauer Ingenieurbau GmbH, Mühlenbeck
Location Berlin - Germany
Type Underpinning
Runtime 10.2022 - 11.2022

Construction under cramped conditions and during ongoing operations

A lift extension is being added to Building 6 of the hospital DRK Clinics Berlin Westend. The building houses the gynaecology and obstetrics clinics. New storage and changing rooms are also being built in the basement. Our Berlin branch produced a total of around 100m3 of jet-grouted elements to underpin the new and existing foundations. While the scope of the project was manageable, the work nevertheless posed a challenge for the specialist civil engineering team. The underpinning work had to be carried out in the basement while the clinic and delivery rooms on the floors above were still in operation. Conditions in the basement were frequently cramped, with ceiling heights of only approximately 2m.  

New foundation for lift extension and lowering of existing foundations 

The foundation of the new extension with the lift shaft will be built roughly 1m below the foundation bed of the existing building while the ceiling height of the existing basement rooms will be increased to accommodate different uses. To achieve this, 120 jet grouted elements with a diameter of approximately 1.25m will be used to lower the existing foundations.  

Efficiency and reliability with jet grouted underpinning 

Reliability and economic efficiency of the execution were key priorities for the employer. The team was able to meet the client’s requirements with a jet grouted underpinning: This method was adopted because the subsoil consists of extremely coarse-grained and non-cohesive sand. With conventional underpinnings in soils like this, there is a risk of the soil under the existing foundation “spilling out” every time a section of the underpinning zone is opened up, which can lead to damage to the existing buildings.

With the jet-grouting method, cylindrical jet grouted elements are produced in several passes from the lowest point of the borehole to the bottom of the existing foundation in what is known as a “pilgrim step” cycle (e.g. produce one element, skip three, etc.). The soil is “milled” with a rotating jet of cement slurry, and the soil surrounding the nozzle is incorporated into the jet grouted element as an aggregate. The resulting area is liquid at first, but the walls are supported by the slurry. After hardening, the grid is compacted one element at a time and a quasi-continuous new foundation body is produced underneath the existing one.    

Large parts of the historic hospital complex are listed buildings  

The DRK Kliniken Berlin Westend began as the municipal hospital of the town of Charlottenburg, which was independent from the rest of Berlin until 1921. Opened in 1904, the pavilion complex with its striking brick buildings in the neo-Renaissance style has been largely preserved to this day and, like the gardens, many parts of it are classified as historical monuments. The only prominent new building is the Head Clinic, built in 1971. In spite of the requirements that apply to listed buildings, the complex has performed a successful architectural balancing act between tradition and innovation for many years. The buildings are regularly remodelled and adapted to the requirements of modern medicine and nursing.