A COMBINATION of piles and a geotextile basal reinforced platform are being used to support embankments for a new road bridge over the Rochdale Canal.
The system is also being used to support a temporary road to carry traffic diverted off the A664 in Kingsway during construction, which involves removing a concrete viaduct and replacing it with an integral bridge and embankments.
The old bridge, built about 70 years ago, crosses difficult terrain comprising layers of peat overlying soft clays. Its concrete support columns have been repaired several times and in the late 1990s Rochdale Metropolitan Borough Council decided to replace it.
Rochdale's technical services department designed the new bridge, which included supplementing the existing support piles with additional mini piles.
The piled embankments are supported by a load transfer platform including geotextile supplier Maccaferri's Paralink material - a double layer of unprotected woven polyester geotextile. The material is laid in strips along the line of the pile caps, carrying the load between adjacent piles and reducing the amount of materials and time needed to build the embankment.
Construction is complicated by the very restricted site, with an area of unusable land to the south east, a garden centre in the south west and houses close to the end of the bridge to the north west. The design had to accommodate a live gas main, which has to be retained within the western parapet and footpath of the new structure.
Galliford is the main contractor, with piling subcontracted to Stent Foundations. Stent brought in Maccaferri to come up with an embankment support solution.
A temporary diversion road was needed to ease traffic congestion during construction of the new bridge. It was decided to use the same basal reinforced platform system for the temporary works.
The first phase of construction, the temporary road bridge over the canal, opened to traffic in August. The second phase, to replace the old viaduct with the new bridge, is now under way.