Project Overview:
Located 5 km west of Walkamin, QLD, the Mt Emerald Wind Farm comprises 53 wind turbines with a combined capacity of 180.5 MW, connected to the grid via Powerlink Queensland’s switchyard and energy network. The terrain presented formidable geotechnical challenges, including extremely hard “welded tuff” rock with strengths exceeding 200 MPa, and a perched water table above void-filled blasted rock fill.
Traditional piling and excavation methods were deemed unfeasible due to access constraints, the extreme rock strength, and the proximity to live transmission lines. PCA Ground Engineering was engaged to deliver a precision foundation system for both gantries and 40m-tall monopoles under demanding structural and environmental conditions.
Challenges
- Extremely hard welded tuff rock (200 MPa+ strength)
- Voided rock fill and perched water table at switchyard pad
- Large base moments (up to 20,000 kNm) from 40m-high monopoles
- Infeasibility of conventional piling, excavation, or blasting
- Limited site access and difficult terrain
- Proximity to live 275kV transmission infrastructure
- Strict environmental and deflection compliance requirements
Innovative Solution
PCA designed and implemented a micropile foundation system for both gantries and monopoles. Key components of the solution included:
- Use of specialised rock drilling technology with compact, low-impact rigs
- Micropiles connected to structures via custom-designed steel pile caps, eliminating the need for concrete
- Finite Element Modelling (FEM) used to ensure cap and group performance under strict deflection limits
- Precision installation with tolerances of ±5mm in plan and <1° inclination
- No additional site preparation, pads, or access tracks required
- Capable of operating in close proximity to existing high-voltage infrastructure
- Enabled record-speed erection of gantries and monopoles due to pre-aligned tolerances
Outcome
- Delivered a safe, high-performance foundation solution in one of the toughest geotechnical environments in Australia
- Eliminated the need for heavy concrete foundations or large plant access
- Provided significant time and cost savings over traditional methods
- Met all performance, safety, and environmental compliance requirements
- Reinforced PCA’s industry leadership in complex micropile foundation systems
