Mannheim
Quartier Hoch 4
Mannheim, Germany / 01.2018 - 12.2019
For the Hoch 4 urban development in Mannheim city centre, PORR special civil engineering constructed a horizontal excavation pit waterproofing system using the soft gel injection method. The sealing slabs were installed to protect against rising groundwater and form an essential part of the excavation pit stabilisation. The project was situated in the immediate vicinity of Mannheim Central Station and involved the construction of a soft-gel base covering an area of approximately 6,000 m².
Facts & Figures
Company
PORR Spezialtiefbau GmbH
Type
Sealing slabs
Runtime
01.2018 - 12.2019
Soft-gel sealing slabs for excavation pit waterproofing
Soft gel injection for the horizontal construction pit wall seal
The construction pit wall seal was constructed as an injection slab with an area of around 6,000 m² and a thickness of 1.0 m. The soft gel slab serves as a horizontal barrier for the construction pit against vertically rising groundwater. The sealing slabs were constructed over a period of three months using large-scale grouting works. The works were carried out using several drilling and grouting systems operating in parallel.
Extensive drilling and grouting works
A total of 2,636 boreholes, each approximately 7.5 m deep, were drilled to construct the soft gel base. The drilling was carried out using two drilling rigs operating in parallel. Subsequently, a total of 7,908 injections were carried out. At times, up to 16 pumps were operated simultaneously for this purpose. In the course of the works, 55,356 m of injection lances were installed and a total of 1,882,104 l of soft gel was injected into the subsoil.
Construction under changing weather conditions
The grouting work was carried out over several months under varying weather conditions. Towards the end of the construction project, some of the work took place whilst temperatures remained below freezing. The sealing slabs were constructed in accordance with the requirements of the construction schedule and technical procedures.
Verification of technical watertightness
Once the work was completed, the constructed sealing slabs were inspected. A pumping test confirmed the contractually agreed technical watertightness of the construction pit waterproofing. This meant that the conditions were in place for further work within the construction pit.
Foundation for the quarter’s further development
By constructing the soft gel base, PORR special civil engineering laid the foundation for securing the excavation pit at the Hoch 4 quarter in Mannheim. The large-scale excavation pit waterproofing was adapted to the requirements of the inner-city site as well as the groundwater conditions.