Ground Improvement of Granville Harbour Wind Farm Foundations-Paper

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Granville Harbour Wind Farm, located on Tasmania’s remote west coast, comprises 31 turbines with a total capacity of about 112 MW. Geotechnical investigations found highly variable ground, including weathered volcaniclastic breccia, basalt, and soils with low SPT blow counts. At 27 turbine locations, these conditions were inadequate for conventional gravity-pad foundations.<br /><br />The project used Controlled Modulus Columns (CMCs) beneath the turbine pads—the first application of this ground-improvement technique for wind turbine foundations in Australia. Designs were developed for eight ground-profile zones and checked for bearing capacity, settlement, differential movement, and rotational stiffness. In a representative design, an octagonal pad was supported by a load-transfer platform and 133 CMCs, each 0.45 m in diameter and up to 24.2 m long.<br /><br />Construction installed 3,333 columns totalling more than 41,630 m. Column lengths ranged from 4.5 to 24.2 m; the longest was reported as the world’s second-longest CMC installed for a wind farm foundation. Remote-site logistics and the unusually deep columns required careful planning and specialist equipment.<br /><br />Quality assurance included automated installation records, concrete slump and strength tests, integrity testing, and two static load tests per turbine. A tested 18.9 m column settled 2.47 mm under a maximum load of 440 kN, with no observed creep during load holds. Design calculations predicted settlements of 19–33 mm and differential settlement below the project’s target.<br /><br />The successful project demonstrates that CMC ground improvement can enable wind turbine foundations on challenging ground, while highlighting the need for site-specific design, construction planning, and comprehensive quality control.

Keywords

Granville Harbour Wind Farm

Tasmania

wind turbine foundations

Controlled Modulus Columns

ground improvement

geotechnical investigation

gravity-pad foundations

bearing capacity

settlement control

quality assurance