Read our feature in the Concrete in Australia Magazine.
SMALL STEPS FOR SIGNIFICANT IMPACT
Australia’s fast-expanding renewable energy sector has driven multi-disciplinary Engineering and Project Management Consultancy WGA (Wallbridge Gilbert Aztec) to make small steps for significant impact.
They believe that without applying a sustainable mindset, there won’t be a future at all. Innovative thinking combined with creative solutions drives WGA’s whole lifecycle approach, pushing boundaries of traditional design and applying practical and sustainable solutions that seek to improve the natural environment.
Expanding its portfolio with some of Australia’s largest energy providers, WGA has supported Australia in its mission to increase the supply of renewable energy to local communities, most recently at one of WA’s newest facilities, Yandin Wind Farm.
Located 175km from Perth, Yandin Wind Farm began generating power in 2021. The farm contains 51 turbines rated at 4.2MW per turbine and is anticipated to have an industry-leading capacity factor of around 50%.
As one of the country’s leading Engineering Consultancies, WGA was appointed by Civil Balance of Plant Contractor, Decmil, to apply specialist expertise in sustainable engineering to support the structural and geotechnical designs of the turbine foundations across the entire project.
WGA interpreted all geotechnical factual reports to specify the final soil parameters for structural design adoption. The constructed foundations consisted of around 630m3 concrete and 68 tonnes of steel reinforcement.
WA Sector Lead Joel Brown said, “Whilst the foundations can commonly be mistaken for big, dumb lumps of concrete to stabilise the tall turbines, the structural design is quite intricate. Technically, we needed to consider many ultimate, serviceability, and fatigue scenarios, and of course there are environmental factors, and co-ordination with other civil works, which need to be considered.
Our concrete design considered flexural design, shear design, pull-out of the anchor bolt cage, and limiting crack widths. In addition, there were several constructability issues to consider, such as the slope of the foundation face to achieve a cost-effective and constructable design. Whilst the design had to conform to the requirements of AS3600; there were many international standards and guidelines specific to wind turbine foundations that required consideration”.
The high loads transferred through the turbine base into the top of the foundation meant the top plinth was constructed using a 40MPa strength concrete rather than 32MPa. The transition between grades of concrete was necessary, and robust quality assurance protocols were put in place to monitor this.
The total depth of the foundation was 3.6m. The methodology to pour foundations in one go (over 10-12 hours) meant the heat of hydration and thermal effects within the concrete were considered.
“Decmil submitted the preferred concrete mix design and performed a thorough thermal analysis. The mix contained low heat cement, slag, and several admixtures to ensure that the concrete did not go off too quickly. Analysis determined that pours should begin in the middle of the night to avoid the hottest parts of the day. Following concrete finishing, the foundation should be covered in insulation for seven days to mitigate any differential thermal cracking”.
The site’s remote location required a logistical masterplan to manage effective supply and delivery of materials.
“Decmil set up two on-site batch plants and had between 8-12 agitator trucks delivering the concrete during any pour. Cold joints within the foundation can cause a host of issues. To mitigate this, backup concrete pumps, vibrators, aliphatic alcohol, and concrete workers were all on-site and ready to be called upon if required. Decmil successfully poured all 51 foundations with minimal issues”.
WGA’s scope expanded beyond foundation design with the civil design of approximately 40kms of access tracks, 51 crane pad hardstands, associated drainage infrastructure, and upgrades to several council intersections to facilitate access to the various parts of the site. The largest vehicle accessing was the blade truck spanning over 83 metres when fully loaded and with dual axle controls to help navigate any tight turns.
“The project was a success from all angles. The design, construction, and commissioning all went very smoothly, and it was a great project to give experience to some of our younger engineers in concrete design and on-site quality assurance roles.”
Yandin Wind Farm was delivered safely, on time, on budget, and according to the engineering design. Operating from mid-2021, Yandin Wind Farm now provides enough power for approximately 200,000 households across Western Australia each year.