Pontoon in the Binnenalster

4th April 2024
Pontoon in the Binnenalster

The Free and Hanseatic City of Hamburg (FHH) intends to expand Hamburg's rail-based public transport system by extending the existing rapid transit network. The new U5 line will connect the east (Bramfeld) and west (Arenen/Volkspark) of Hamburg.

The in-depth subsoil investigations in the U5M3000 section between the main railway station and the university have begun. They form the basis for the upcoming design and approval planning and comprise a total of approx. 160 explorations (drillings and pressure soundings) up to a depth of 65 metres in two consecutive stages.

BBI Geo- und Umwelttechnik Ingenieur-Gesellschaft mbH, a company of our GuD group of companies, was commissioned to provide geotechnical consulting services for this section.

Special issues in this project are:

  • Alternating different construction methods over a short distance (tunnelling, open construction method for stops, reversing and parking facilities and emergency exits)
  • Heterogeneity of the subsoil (rolling soils, boulder soils, clays and silts)
  • Icing (for cross-passages, emergency exits and intersections with existing structures)
  • Inspection: arrangement of DSV grids for ground reinforcement, anchoring of the excavation base, embedment depth of the diaphragm walls, presence of natural sealing bases/sealing layers or arrangement of artificial sealing bases or UWB bases.

As a geotechnical expert, BBI Geo- und Umwelttechnik Ingenieur-Gesellschaft mbH examines the complex geotechnical boundary conditions of an inland tunnelling project and advises the client (U5 GmbH) and the general planner on the LPh 3 and LPh 4. The execution of subsoil explorations for the planning of the underground railway line in the Binnenalster is noteworthy. For this purpose, 2 pontoons will be used for the planned 26 water boreholes (drilling depth 65 m) and 14 water pressure soundings (sounding depth at least 30 m).