23-08-2006
23/08/2006
Contractors widening the A3, Northway by-pass in Portadown, Northern Ireland, chose MacWall segmental retaining walls, to help speed the construction process and keep traffic disruption to a minimum during the 26 week contract period.
The original A3, Northway threaded its way through a heavily built up area of Portadown with only the minimum area of land available for widening. Working within these constraints meant that new retaining wall structures were needed to support the 3-4m high, elevated carriage ways, roundabouts and filter roads for the enhanced network.
Complex internal and external curves also meant that traditional reinforced concrete retaining walls would be too costly because of the in-situ concrete foundations, elaborate shuttering and many separate pours that would have been required.
The MacWall Vertica walling used at Portadown is a dry built, segmental retaining wall system made up of concrete facing blocks that work together with geogrids and compacted back-fill to form a highly efficient, engineered retaining wall. The MacWall system is installed by hand and does not require concrete foundations so temporary shuttering is not needed to retain the excavation while the concrete footings of conventional walls are allowed to cure.
Throughout the building works, there was controlled traffic flow and excavation below the carriage so installation had to be done quickly to reduce the risk of collapse. The inherent flexibility of the MacWall Vertica segmental retaining wall system allowed short lengths of wall to be excavated and installed quickly, before the ground became unstable and liable to collapse. Even with the intricate curves which were a part of the Department of Road Services (DRD), Road Services project, installation went smoothly with up to 40m2 of walling completed per day.
The £1.15m scheme was designed in association with Engineers Maccaferri and TAS Approval was sought and achieved. The construction works were carried out on site by Contractors, Gibson (Bainbridge) Ltd.
