About the project:

Tunnelling Solutions worked with John Holland Bouygues Joint Venture and Transport for NSW on the excavation and permanent lining of the Arncliffe Pedestrian Tunnel.

Project snapshot:

• The tunnel was constructed through a rail embankment with only 2.5m of cover to live rail tracks and extremely poor ground conditions.
• The original design was for a complete array of clutched canopy tubes to be installed by the previous contractor but unfortunately during the installation process they ran into significant problems.
• The canopy tubes became unclutched resulting in significant gaps between them of up to 1m which caused major challenges through the excavation and support phase.
• A permit to tunnel process was strictly applied during the excavation period with attendance from the client and the designers signing off on the sequence of excavation that was required for that day.
• Steel sets were installed every metre along with infill shotcrete which made up the temporary support along with 50mm-100mm of shotcrete applied daily for face support.
• Surface and convergence monitoring was frequently carried out but with good tunnelling practices being implemented no settlement was reported.
• Both portals were constructed using traditional formwork systems that were challenging to build due to the potential of significant uplift pressures.

Completed work:

• The excavation and permanent lining were completed well ahead of schedule.
• Erected a purpose-built form used to line the tunnel.