Tunnel excavation in Berlin

Scope of Work

A 6,4 km expansion of the Berlin Underground bumped into trouble when ground water started pouring in during tunnel excavation under the Minna-Cauer-Strasse. Work had to be interupted, and the project put on hold. To keep moisture penetrating from below at bay, this part of the construction site was flooded.

That’s how we ended up with our underwater excavator in Berlin. It’s a typical example of a task where a land based excavator can be converted to a useful subsea tool.

There was a lot of grout piles inside the tunnel due to grout injection performed in the past. The remote-controlled excavator was used to cut grout and soil with a drumcutter in order to dredge and pump the material out of the pit.  Tunnel water was of very high turbidity, and there was practically no visibility (>5cm) – a fact that made the task even more complex.


Berlin, Germany

Main Spread



Cutter drum, Xcentric ripper, long suction nozzle, HP jetting

Water Depth



360 days



Planning Phase

Various underwater excavation works was required; dredging/removal of soil, demolition of grout blocks, silt suction/removal and removal of horizontal and vertical blinding layers with various material strength. The variety in material made the preparation phase demanding in terms of selection the most proper tooling. Several site visits and substantial hours of testing was performed prior to the operation to optimize the project execution.

  • Various soil/ layers to be removed
  • Sand
  • Mud/clay
  • Grout piles (Grid, 1,5 x 2m)
  • Horizontal and vertical steel and plastic pipes
  • Reinforced concrete blinding layer 
  • GEWI uplift anchors (not to be damaged)
  • 0-5cm visibility
Specific Tooling

A 20Te Scanmachine spread and various tooling was shipped to Berlin 

  • Extra long suction nozzle (2m)
  • Xcentric ripper
  • Drum cutter
  • Telescopic arm
  • 3D sonar to deal with the limited visibility

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