Ciaran Reilly & Associates recently assisted Thrace Synthetic with independent design checks of reinforced soil access roads for the first phase of the 164ha development of the Centre Parcs holiday village in Co. Longford. A set of designs were prepared to deal with a wide variation in ground conditions encountered on the site, with a common target CBR being set at the finished access road surface to ensure uniformity. Following a review of loadings and ground conditions, designs were progressed utilising Thrace Synthetic’s range of nonwoven geotextile separators and extruded punched-and-stretched polypropylene biaxial geogrids and crushed rock fill.

The thickness of the fill and the strength of the geogrid were adjusted to achieve efficient and economic designs in areas with differing ground conditions. Good construction site practice on the part of contractors Bennett Construction, high quality materials, and favourable weather conditions led to the target CBR value of 15% being consistently exceeded in acceptance testing, with CBR results in excess of 40% frequently being achieved at subformation level in the marginal tills at the site.