The challenge
The A59 Kex Gill Road is a key east-west connecting route, linking Harrogate and Skipton, in the Washburn Valley area of North Yorkshire.
The road has been subject to a series of landslips, causing frequent unplanned closures over the last few years. The most recent landslide (in February 2024) resulted in emergency works to address the slippage at Blubberhouses, and to prevent future movement of the road.
Works were subject to limited access, sloping ground, and hard bedrock. Plus the road cuts through a Site of Special Scientific Interest (SSSI) to add to the complexity of the scheme.
The solution
Two structural retaining walls comprising a total of 140 No. GU27-600N steel sheet piles at 11 metres in length were installed, then trimmed to the required level.
Giken Supercrush was selected as the most viable method of installation for a number of reasons. This piling procedure uses ground reaction force, the machine operating from atop previously installed piles. This was an key consideration, as the use of this equipment would vastly reduce loadings on the already failed slope, when compared to alternative methods of installation. In addition, this technique is vibration-free; the hard strata found at site was able to be overcome by operating the Giken in Supercrush mode – whereby the ground is simultaneously augered as sheet piles are hydraulically pressed in.
To accelerate our part of the works, we deployed an additional Giken Silent Piler and operated extended hours, including evenings and weekends. This allowed us to swiftly hand back control to the main contractor ahead of schedule, for reconstruction of the carriageway behind the sheet piles, along with drainage works and the relocation of telephone cables.
