CONTRACTORS for a major town centre link road in Runcorn, Cheshire used the Forticrete Keystone geosyntheticreinforced dry-build modular block retaining wall system to overcome a earth retaining problem.
Ground conditions, live loading and the presence of a culvert at the site of the Daresbury Expressway Junction in Runcorn, Cheshire, presented a challenge for Birse Construction's Cheadle Hulme office, which was responsible for the contractor-designed wall element for client Halton Borough Council.
With conventional brick walls or cast insitu concrete ruled out because of the risk of differential settlements above a culvert, the Warrington office of consulting engineer WS Atkins recommended a reinforced soil retaining wall using a blockwork cladding system.
The BBA-certificated Keystone system was chosen as the best match to both technical and aesthetic requirements.
Built on a reinforced granular base, the 60m long,4m high wall was combined with Tensar geogrids for reinforcement of the soil mass behind. The wall forms part of the overall structure, featuring an integrated precast parapet.
Mortar-free, the modular Keystone system uses immensely strong 'pultruded'fibreglass fixing pins, which ensure accurate alignment of the units and lock in the geogrid reinforcement.
On its landscaping section's advice, the authority specified Terracotta from the Keystone 12-colour range and the choice of lighter weight Compac units contributed to the requirement to reduce loading. Bands of shotblasted units feature among the main body of splitface units to produce mixed textures and to reduce the visual mass of the wall.
The Keystone system also met the authority's brief to provide a finish that deterred graffiti and was difficult to climb.