Immersed Tube Tunnel, Limerick - Projects - MLM
Immersed Tube Tunnel, Limerick - Projects - MLM
Immersed Tube Tunnel, Limerick - Projects - MLM

Immersed Tube Tunnel, Limerick

Project Information
  • Location
  • Limerick
  • Sector
  • Ports & Harbours / River & Marine
  • Services
  • Infrastructure, Temporary Works Design, River & Marine Engineering
  • Value
  • £100m

The immersed tube tunnel crossing the River Shannon in Ireland required the construction of large on-line temporary cofferdams on both banks of the River to allow the precast concrete tunnel units to be floated out through the tidal defences into the river.

MLM provided design and checking assistance to John Sisk and Sons who are part of a DBFO consortium for a new Immersed Tube Tunnel under the River Shannon, as part of a bypass to Limerick in Ireland. This involved complex stability analysis of the cofferdams under transverse and longitudinal loads at the many different stages of their construction and use.

Key Features

  • Large size of Cofferdams: 110m long x 31m wide x 17m deep.
  • Poor ground conditions: Soft alluvium overlying limestone bed-rock.
  • Large tidal range.
  • Very complex sequence of construction.
  • Frequent design changes to the temporary works, to assist the other consortium members in the programming of their work.
  • Load cell monitoring results fed back into design.

The temporary works design received the Fleming Award as an outstanding example of co-operation between the geotechnical engineer, the designer and the contractor.

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