Ground Improvement Of Granville Harbour Wind Farm Foundations Using CMC

Granville Harbour Wind Farm is located on a remote site that is approximately 35 km northwest of Zeehan on Tasmania’s west coast. The project includes 31 wind turbines with the capacity to generate 112 MW of power when it is complete. Each giant turbine is 137 m from ground level to rotor hub and 200 m from ground level to blade tip. The site’s ground profile consists of extremely weathered to highly weathered volcaniclastic breccia overlain with stiff clays, silts and embedded basalt cobbles. At 27 turbine locations, the ground did not meet the project’s requirements and specific measures were required to improve the foundations’ behaviour. Whilst piling is commonly used for improving bearing and reducing ground settlements of foundations of highly sensitive structures, in an innovative first-time approach in Australia, an alternative foundation solution using Controlled Modulus Column (CMC) rigid inclusions was considered and developed to allow the safe operation of the turbines more affordably. During this process, foundation systems were designed for eight ground models. Approximately 44,000 m of CMC were installed to support the wind turbines. The longest and shortest columns were respectively 4.5 m and 22.8 m. Quality control and assurance included the installation of trial columns, concrete testing, integrity testing and static load testing of the columns.