After thousands of athletes ran through the Dublin port toll tunnel, late December the US$593M project officially opened for business.
The twin 4.5km long tunnels had parallel 2.6km bores (by Nishimatsu), the rest cut and cover (Mowlem and Irishenco). Tunnellers dealt with faulted, partly folded limestone interbedded with mudstone and shale, and also boulder clay with fluvial deposits (T&TI, December 2006, p30-35).
Nishimatsu used two refurbished Herrenknecht TBMs. The hard rock TBM, “Grainne”, was a closed faced machine, cost nearly US$35M, weighed 1,800 tonnes, was 156m long, and needed a gang of 45 per shift, said the client Dublin City Council. The open machine, “Megan”, was 60m long, weighed 1,100 tonnes, cost almost US$13M and required a gang of 18 per shift.
Work started on the project in 2001.
The tunnel enables most HGVs to pass through in six to eight minutes to the north of the city. Early in the scheme there were claims it did not provide sufficient vehicle clearances for some HGVs from Europe. Operational height clearance is 4.65m for trucks within the 4.9m high, dual carriageway tubes.
