THE PROBLEM

Access roads were needed to allow safe delivery and erection of 11 new 2MW wind turbines. Initial proposals for road construction suggested a large thickness of granular fill would be required for the construction of roads and platforms over the site conditions encountered, providing cost challenges for the contractor.

THE SOLUTION

A Tensar MSL system, which is a mechanically stabilised granular layer incorporating Tensar TriAx® geogrids, was designed to value engineer original road thickness proposals whilst maintaining serviceable access for heavy construction vehicles and cranes.

PROJECT DESCRIPTION

The renewable energy market has made giant strides over the past ten years and wind farms in particular have played a prominent part in the expansion of this sector. However, wind farm developments are often located in remote areas where weak ground conditions are encountered, meaning that innovative methods of access road design are required to keep project costs down. Swinford Wind Farm near Lutterworth in Leicestershire was no different.

The successful contractor, Jones Bros Ruthin (Civil Engineering) Ltd needed to build 6km of access roads and 11 separate working platforms over ground conditions where CBR values were as low as 2%. After the original road construction thickness was determined, Jones Bros approached Tensar to use their extensive experience in wind farm infrastructure applications to explore the potential for reducing granular layer thicknesses and contributing to value engineering across the site.

Taking anticipated trafficking and site specific ground conditions into account, a Tensar MSL was proposed for access road construction which offered the contractor an overall saving of around 43% compared to an non-stabilised thickness. Associated carbon savings of 39% were also made, which can be an important consideration in the approach to renewable energy. The thickness of the Tensar MSL was determined on the basis of direct trafficking of the granular layer with surface deformation limits included within the assessment.

Project Manager for Jones Bros Eryl Roberts commented that “Access roads for any wind farm are of paramount importance and the construction of these roads has been a major success. The roads have been built using Tensar TriAx geogrid with no evidence of rutting or surface deformation. We have had 2000 vehicles pass over the roads, including concrete mixers, dumpers and stone delivery vehicles and these roads have been smooth and consistent throughout the project.”