Specialised civil engineering work for the first of seven construction phases began in March 2023. The subsoil consists mainly of clay. Firstly, a soldier pile shoring was constructed around the perimeter of the construction pit. Thanks to its ability to be customised to the local conditions and the possibility of constructing it close to existing buildings, its use offers flexibility and safety for the client. This was followed by the construction of 8,000 m2 of diaphragm walls with a wall thickness of 60 and 80 cm to a depth of 25 m from 4 m below ground level. Wherever possible, the walls were secured with grouted anchors in up to three anchor layers. Thanks to high anchor loads, they represent a safe solution within the complex construction pits. In other places, the shoring wall was secured with diagonal braces.
Designed as a permanent structure and external basement wall in exposed construction, the diaphragm walls transfer the loads from the building into the subsoil. A cost-saving solution, as no separate external wall is required. The ceilings of the basement floors tie into the diaphragm walls, which remain visible in the underground car parks. Therefore, there were increased requirements for the surfaces and positional accuracy. For example, the installation boxes in the reinforcement cage had to be positioned precisely to ensure that the ceiling connections fitted perfectly.
Optimised planning
Our colleagues at Stump-Franki Planung GmbH were also involved in the project from the very beginning. For example, the proposal to support the diagonal bracing on diaphragm wall beams was accepted and implemented by the client. As a result, there is no interruption to the structural work in the basement and the floor slab has fewer joints.
