Sophienkontor, Kiel

The Sophienkontor office and commercial building was constructed in a prime location in the city of Kiel: right next to the Sophienhof, the largest covered shopping centre in northern Germany. The direct connection to the existing buildings, high groundwater levels and the inner-city location all necessitated low-deformation, waterproof shoring for the temporary construction pit system. To this end, PORR created a 3,200m² cast in situ concrete diaphragm wall anchored by 151 strand anchors in two locations. The PORR subsidiary was also responsible for the dewatering and steel reinforcement of the construction pit walls. The construction pit was horizontally sealed by a till cover layer. Planning was completed by PORR Spezialtiefbau Planung GmbH.

Reduced CO₂ with optimised design engineering

Six floors, two stacked storeys, approx. 5,300m² of office space, 300m² of commercial space, over 740m² of archival space and two below-ground floors with underground parking constitute the key figures for the Sophienkontor building. Originally, the client’s design plan called for a one to two-storey basement beneath the new building, featuring numerous different levels. PORR optimised and streamlined these plans in close consultation with the architects and the client. The resulting plan provided additional space in the basement floors as well as significant reductions in concrete required, CO₂ emissions and time. It became possible to construct the below-ground floors in two storeys throughout.

This change of plans included a switch from an 80cm bored pile wall to a 60cm diaphragm wall, representing a saving of approximately 20% of the concrete originally allocated.3D planning and visualisation of the construction pit and anchoring played a significant part in the efficient and economical execution of the construction on site. This process reduced incidences of collision between new anchors and existing piles beneath the adjacent buildings. Probing of the construction soil revealed the precise location of the sealing marl layer, and the diaphragm wall lengths were able to be precisely determined.   

Limited space called for high precision

A particular challenge was presented by the limited space available on the 1,800m² construction site. This required great care and precision from the PORR team. In some places, the distance between the diaphragm wall gripper and the neighbouring building was as little as 10cm. Owing to the limited space, no additional protection could be inserted. Markus Wenke, Regional Manager North at PORR Spezialtiefbau GmbH, and project head Sebastian Grote had this to say about their collaboration: “That this challenging project was able to be completed on schedule is entirely due to an incredible team spirit among all project participants, beginning with project developer Urban Space and including the offices of Florian Fischötter Architekten as well as our own in-house planning and construction execution department.”