First motorway box jack successfully completed
The first concrete bridge to be constructed beneath an operational motorway in the UK has been successfully completed by Nuttall, using the box jacking technique. The box jack is part of a nine million-euro project, undertaken on behalf of the Highways Agency to provide a section of dual carriageway road between the two roundabouts on the A43, either side of the M1 at junction 15A, near Northampton.
Box jacking involved the construction of a large concrete box weighing 3,500 tonnes and measuring 8.5 metre high, 14 metre wide and 45 metre long. The box itself was jacked forward against the motorway embankment using a number of hydraulic rams and friction was reduced to a minimum with the use of a patented anti-drag system. A tunnelling shield allowed the spoil material to be excavated ahead of the box. The box jacking technique was selected by the Highways Agency in order to minimise traffic disruption on the M1. This innovative solution allowed construction to take place beneath the motorway to provide an additional road bridge whilst allowing the motorway to operate normally above the excavation. The total project is due for completion in April.