Construction World February 2021

PROJECT PROFILE

A completed foundation at Roggeveld Wind Farm ready for tower erection.

Remotely located in an area of rough terrain and challenging topography, Roggeveld Wind Farm in the Karoo demanded innovative construction design and implementation, as well as careful scheduling, logistics and environmental management. ROGGEVELDWIND FARM’S INNOVATIVE DESIGN AND IMPLEMENTATION

L everaging its experience in wind energy facilities, Concor constructed specially-designed concrete bases for 47 wind turbines. The company also built 34 km of roadway, with appropriate gradients to facilitate access for readymix trucks as well as the large, specialised vehicles that must haul the turbine towers and equipment. With a construction footprint of 40 hectares, the project dealt with reaching inaccessible areas to build the bases and hardstands. The highest point of the project area is 200 metres higher than the site office, with many construction areas difficult to access even using 4x4 vehicles. The 25 000 m 3 of concrete required for the project was batched on site, but the nearest turbine was 12 km from the batching plant.

construction of the foundations and the pre-assembly slabs. Each tower required the construction of the concrete doughnut-shaped slabs at its base, on top of which the five key-stones making up the bottom tower section were placed. The hilly rugged topography of the area – combined with strict environmental controls – had an impact on concrete slab construction, demanding the size of the hardstands be smaller. Topography limited the reach of the new roadway network, while the project footprint was constrained by the area’s sensitive ecology, leaving only a 12 metre corridor in which to work. A precast yard had to be built for the construction of the ‘doughnut’ slabs, from where they were transported to the hardstands. Using precast slabs in this application is not common practice in South Africa, although it is routinely applied in Europe. Each tower base required blasting, excavation and cleaning, after which blinding was poured. Levelling legs were installed on top of the blinding to hold the levelling template in place during casting. Approximately 2 000 tonnes of reinforcing steel were used for the turbine bases. The considerable weight of the concrete ‘doughnut’ slabs meant they had to be cast in two pieces, facilitating transportation across site. Once moved, the two items must be fitted together, with tight

Aggregate had to be sourced from 180 km away. Construction innovation technology

Unlike most wind energy projects, the turbine towers at Roggeveld Wind Farm are constructed from concrete not steel. This required several innovations from Concor including establishing a yard for placing and preparing tower sections as well as pre-assembly slabs – or ‘doughnuts’ – for the trestles used in the erection of towers. The heavier weight of concrete towers impacted the design and

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