Structural Geotechnics at Glenconway

Aug 09, 2013

The Glenconway development is not only impressive for its generation capacity but also for the complex constraints under which the site was developed. Danny Glynn and his team at Byrne Looby Partners worked as designers on both Phase 1 and Phase 2 of the project, working for SSE Renewables, Glenconway’s developer and Gael Force Renewables, the main contractor for the entire scheme. 

As a chartered environmentalist and CEEQUEL Assessor, Danny was well-placed to address this environmentally sensitive site, which is situated in an upland catchment area and has significant depths of peat“. During the site investigation and peat assessment we were careful to make recommendations that would protect the natural environment both during construction and in the operational phase,” notes Danny.

The site had peat deposits up to 4.5m deep in places and unusual commercial peat harvesting requirements, “typically we would float roads over the peat, however, due to commercial harvesting constraints, the peat had to be excavated to more competent mineral soil level”, explains Danny. Deep cuttings were excavated for the haul roads and peat slopes/gradients had to be carefully designed and analysed to ensure long-term stability and safety.

Typically, wind farms are constructed from existing ground level, however, the Glenconway site was complex - primarily on Phase 2 - on account of the “deep peat cuttings” that had to be constructed across the site. In fact, one particular access track, referred to as the ‘orbital’ was exclusively built in cutting. Limiting haulage distance for excavated peat allowed for cost savings during construction; this required careful design of peat storage areas adjacent to roadways. To optimise the ground levels, access tracks, cuttings and storage areas, Danny’s design team created a 3D model of the site.

As with any wind farm project, the foundations for the turbines need to be assessed for fatigue and cyclic loading. Byrne Looby has a structural geotechnics team that comprises 50% structural and 50% geotechnical engineers. This team is ideally placed to carry out foundation design on wind farms and understand the complex nature of soil-structure interaction. The group designed piled foundations for the turbine bases and also carried out a value engineering review of the turbine bases, which identified significant opportunities for cost savings.

The final turbine was erected on Glenconway this month, bringing the project near to completion. Reflecting on the success of the project, Danny commented that “close collaboration between the client, contractor and design team has facilitated the smooth execution of this project on, what turned out to be, a fairly complex site. We are delighted to have been part of this successful project which will deliver large scale clean energy for Northern Ireland for many years to come”.