Douglas West Wind Farm Extension (78MW)
CLIENT'S CHALLENGE
The Douglas West Wind Farm Extension required the construction of a 6.5km access road across areas underlain by weak peat and clay subgrades. With in-situ CBR as low as 0.5%, the project demanded a solution capable of accommodating heavy construction traffic while maintaining pavement stability and minimising aggregate requirements.
TENSAR SOLUTION
Tensar designed a mechanically stabilised layer (MSL) using Tensar InterAx® geogrids designed in accordance with the LAAMS methodology, which is available through the Unpaved Road module within Tensar+™ design software. The stabilised haul road enhanced load distribution and aggregate confinement within the road construction, enabling haul roads to be constructed over very weak peat and clay subgrades using locally sourced Class 6F5 fill material beneath a Type 1 granular running surface. A number of alternative haul roads designs were assessed, incorporating either single or double-layer InterAx® geogrid configurations, allowing the client to optimise the balance between construction cost, haul road performance, and material volumes. The stabilised road sections provided improved bearing capacity, increased resistance to rutting and deformation, and reduced aggregate thickness requirements when compared with conventional solutions. The final design was engineered to support both the intensive construction-phase traffic loading and the long-term operational requirements of the wind farm road network, whilst delivering a cost-effective and sustainable solution for the challenging ground conditions encountered on site.
CLIENT'S CHALLENGE
The project required crane hardstandings capable of supporting outrigger pressures of 250 kPa over a loaded area of 2.5m × 6.0m. The area included twelve hardstanding locations and totalled around 16,800 m². The construction traffic was up to 9,000 ESALs, in addition to in-service traffic of approximately 300 ESALs.
TENSAR SOLUTION
Tensar proposed the use of a Mechanically Stabilised Layer (MSL) incorporating Tensar InterAx® geogrid technology to improve load distribution and enhance platform performance. The design was developed using Tensar’s T-Value design methodology, targeting a factor of safety of 2 against shear failure at formation level. Two alternative platform configurations were developed for the client to enable them to balance between platform thickness and geogrid usage. The option chosen was the simplified construction approach, which utilised a single layer of geogrid instead of Tensar InterAx geogrid, providing a reduction in thickness and a technically robust solution.
