S21-Berlin â€“ Design and Underwater Construction of a Covered Construction Pit without Direct Accessibility from AboveÂ-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes the design and construction of a covered construction pit for the S21-Berlin project, where direct access from above was unavailable.<br /><br />An initial concept used a jet-grouted cutoff and supporting layer beneath the existing deck. Water ingress during excavation led to a revised approach: constructing an underwater concrete base to seal and support the pit. Structural provisions included lateral steel cleats, local reinforcement, and a massive underwater concrete strut.<br /><br />Excavation was carried out remotely using specialized equipment, including a scanmachine, milling and suction tools, and a remote-controlled excavator. The work proceeded in staged excavation layers, with the existing blinding layer removed beneath the deck. Real-time 2D/3D visualization, sonar, and cameras helped operators monitor progress. Excavated material was processed through a treatment plant using desanding equipment, lamella separators, storage tanks, and filter presses. Reported excavation production was about 3 metres per hour, with round-the-clock operation.<br /><br />The underwater concrete base was placed using a concreting carriage and floats, with temporary formwork and levelling measures. The presentation also details construction of the underwater concrete strut.<br /><br />The project demonstrated that an underwater concrete-base pit can be built without direct access from above. The presenters emphasize the importance of flexible, goal-oriented collaboration, strong attention to worker safety, and careful consideration of pit geometry and available construction-site space.

Keywords

S21 Berlin

construction pit

underwater concrete base

jet-grouted cutoff

excavation

remote-controlled excavator

sonar visualization

desanding equipment

safety collaboration

pit geometry