Dublin Port Tunnel
Dublin City Council & National Roads Authority
Highways – Tunnelling and Infrastructure
The Dublin Port Tunnel Project links the M50 C-Link motorway system surrounding Dublin, with Dublin Port. The tunnel route passes under densely populated areas of the city, a major railway interchange, open parkland and the main north-south arterial route into Dublin. The main purpose of the project was to alleviate the traffic congestion within the city by removing heavy goods vehicles from the city’s roads.
The project consists of over 2.5km, 12m diameter Twin bored tunnel, 1.5km of cut-and-cover twin tunnels constructed within open-cut and diaphragm walls and a pipe-jacked crossing underneath a mainline railway system. Vehicular and pedestrian cross-passages are included within the tunnels and a new port interchange has been constructed to the south of the project.
The bored tunnels were constructed using a closed-face “hard rock” TBM within limestone and an open-face shield TBM within boulder clay. Cross passages were built using drill-and-blast techniques with associated ground stabilization by rock bolting and sprayed concrete linings.
LBA played a major role as part of the Construction Supervisor’s team, managing and auditing the works on behalf of the Client and administering the design-and-build contract. Key personnel were placed to oversee and audit the TBM drives and railway crossing works with further support being given in coordination of the Contractor’s geotechnical, geological and instrumentation activities. LBA was also directly involved in the assessment of the Contractor and Client’s commercial interests. The progress and compliance monitoring of the Contractor’s programme to completion was also undertaken, with additional planning requirements including third-party interface issues, being managed by the team.
The successful completion of the bored tunnels beneath the densely populated area of North Dublin, with minimum disturbance to the local community and negligible effect on the overlying structures, was a significant milestone in the Project.
The completion of the pipe-jack canopy, lying only 3.5m beneath the mainline & local railway system within poor ground conditions and exposed to large tidal influenced, water-table fluctuations was attained with no detrimental effects on the railway system itself. Coupled with the subsequent success of the major temporary works and excavations for the main works beneath the canopy, this aspect of the Project demonstrates an ability to design, construct and manage major civil engineering works in severe adverse conditions.
It is also pleasing to note that the Project was awarded the Fleming Award 2003 for the excellence of the geotechnical design and construction of the northern open-cut works within an existing dual-carriageway road system.
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