Overview


As part of an engineering, procurement and construction (EPC) contract, BERGNET was in charge of the Ashegoda Wind Farm project in Ethiopia. With 120 MW of power, it is Sub-Saharan Africa’s largest wind farm at the date of the project launch (October 2009). In addition to providing and installing the wind turbines, this project involved creating access points for the machines (around 35 km in total), electricity cables (33 kv overhead and underground) and the 33kV/ 230kV power sub-station that injects the energy generated into the national transport network.
setec carried out geotechnical studies for VERGNET on the turbine foundations, including scaling the anchoring micropiles for the machine cables, as well as monitoring implementation.

Assignment


• Defining and monitoring geotechnical investigations
• Providing a geotechnical summary
• Scaling cable anchoring elements
• Monitoring and interpreting traction tests on the micropiles
• Supervising foundation work

Owner

Key figures

• 30 x 1 MW wind turbines (54 in phase 2)
• 300 4-21 m micropiles
• 3,500 ml of micropiles
• 2,700 m3 of concrete for the foundations

Period of services

Key challenges

Our teams developed a scaling methods based on the notion of the cyclic stability diagram: this approach involves tracing a stability range for cyclic stresses on a plane defined by their average share on the x-axis and their cycle share on the y-axis, and comparing this field, defined using the properties of the micropile and the surrounding soil, with the cyclic stresses on the foundation.