THE PROBLEM
Stabilised access was required to allow for the construction of wind turbines using roads affected by melting snow and ice, as well as periods of heavy rain during the planned two year construction phase. The road was required to carry construction traffic as well as turbine delivery and erection traffic. However, as low strength soils were present, large thicknesses of granular fill would normally be required.
THE SOLUTION
A Tensar mechanically stabilised layer (MSL) incorporating Tensar TriAx® geogrids was designed to cater for the anticipated reduced bearing capacity of the existing soils, as well as high loading from the wind farm construction traffic. The MSL produced a thinner than expected granular layer whilst maintaining serviceable access roads.
PROJECT DESCRIPTION
The installation of wind farms requires the construction of access roads to carry traffic from heavy trucks. In regions with cold winter climates such as Sweden, when the snow and ice melts in spring or during heavy rains, a significant amount of water can be trapped in the upper layer of soil beneath the road surface, softening the soils and leading to premature road failure.
The damaged roads can cause project delays or potentially halt materials being transported to and from the site.
For the wind farm development at Hafsnas, 14km of 5.5m wide access road were to be constructed over variable and low strength formation soils affected by seasonal thawing and heavy rains. Sections of existing roadway had been damaged by earlier trafficking operations, therefore remediation as well as new areas of construction were needed. It had already been identified that conventional reconstruction methods would require the existing roads to be widened. However, by adopting Tensar Technology this meant the existing road footprint could be maintained.
A mechanically stabilised layer incorporating Tensar TriAx geogrid was designed to cater for vehicles with axle loads up to 15 tonnes. The design minimised the road layer thickness needed to provide access for wind farm traffic – greatly reducing the volumes of granular fill required.
The Tensar TriAx was rolled out over the leveled surface of the existing roads. After this, well graded granular fill was placed and compacted on top to achieve the required design thickness of the mechanically stabilised layer.
The adoption of the Tensar solution achieved the Client and Contractor’s joint objective which was to maintain the serviceability of the access roads during the planned 2 year construction period to avoid any disruption to wind farm construction operations.
