A rocky road

The Welsh Assembly Government, UK, awarded Alfred McAlpine a #10 million design and build contract to improve the 4km stretch of road between Blaenau Ffestiniog and Cancoed in Wales. The main challenge was to ensure that the road remained open during the scheme. In addition, the project involved the protection of two listed bridges and a listed weighbridge. Engineers are using a reinforced soil system to protect the listed structures in a 200m diversion to divert traffic away from a triple-arch bridge that will be demolished and rebuilt. Temporary concrete abutments and PU32 steel sheet piles have been installed as a base for the soil-reinforcement structure. Huesker Fortrac 55/30 and 35/30 geogrids have been used to form a wraparound reinforced soil structure. Temporary wooden shutters support the edge of the new embankment. The depth of the layer of fill and strength of the geogrid varies along the diversion. The Blaenau Ffestiniog to Llandudno railway, which runs close to the west side of the site, is being monitored to ensure that there is no movement. The workers have also had to be careful not to dislodge the local slate tip. A dead roller is being used instead of a vibratory roller to compact the fill. The road has been widened to allow more room for pedestrians and cyclists.