The last of 39 pipejacked steel tubes was being driven in Dublin last week for the crossing of the £282M Dublin Port Tunnel beneath the main Dublin to Belfast railway line.
The twin tube, dual lane road tunnel connecting the port of Dun Laoghaire with the city will pass 6m below the level of the main line and two suburban lines which run alongside it on the embankment above. Irish rail authority Iarnrod Eireann was not willing to allow a jacked concrete box solution for construction, so joint venture NMI (Nishimatsu, Mowlem and Irishenco) has opted for a supporting frame of jacked pipes with those at the sides filled with concrete. The tunnel will be cast inside as it is excavated. The method has not been used much in Europe although JV partner Nishimatsu, which is engineering and carrying it out, has experience of the technique from Japan.