THE PROBLEM
There was a requirement to carry heavy loads over peat for access roads and platforms in the development of a new wind farm. The access roads needed to support the trafficking from construction vehicles as well as from the turbine delivery vehicles and cranes.
THE SOLUTION
For the access road, a Tensar TriAx® mechanically stabilised layer using 700mm of imported stone was laid over fascine mats. Working platforms were designed with a 1300mm thick TriAx® mechanically stabilised layer with the geogrid/stone placed directly on a peat subgrade.
PROJECT DESCRIPTION
The project required the construction of a 7 turbine wind farm within upland forestry and which included 3km of new access roads. The site consisted of extensive coniferous forestry which was felled to permit the construction of new access route to the turbines. The construction encountered and accommodated tree stumps and peat up to 7m deep. Generally the CBR of the ground at the site was around 0.5%. This would normally necessitate the use of very thick stone layers in order to accommodate the trafficking expected which brings the associated problems of large numbers of vehicle movements and excessive settlement of the road.
Lagan’s Project Manager, Andy Davies commented, “We chose Tensar International for Pates Hill wind farm because we were confident that the design Tensar produced utilising their TriAx products would meet the performance specification for the roads and hard standings in the poor ground conditions encountered on both projects. The TriAx grids allowed the use of much less stone for the construction of the access roads and working platforms. This stone is an imported material, generally conforming to a DoT 6F2 sub-base and which requires quarrying, transport and plant to place in the site with all the CO2 emissions involved in these operations. Any significant reduction in stone is therefore to be welcomed both in financial and environmental terms”.
Tensar designed a floating road to suit the defined trafficking for access road construction and turbine erection plant. As traditional fascine mats were readily available these were included by the client in the road as a regulating platform. In addition, four working platforms were devised to perform the task of, firstly, piling the platform, then erecting the lifting crane and ultimately providing support to the outrigger positions during the lifting operations.
