Geotechnical and geology solutions for the development of a hydro power plant, supplying renewable electricity to industrial, commercial and residential consumers.
The situation
The Serra do Facão Hydro Power Plant (HPP) was constructed on the São Marcos River, in State of Goiás, Brazil.
With an installed capacity of 210 MW, Serra do Facão HPP is connected to the Brazilian energy grid, supplying renewable electricity to industrial, commercial and residential consumers.
Our approach
In an EPC/Turnkey contract, we were was responsible for all of the engineering for the project, including hydraulic, hydrology, hydrogeology, civil, structural, mechanical, electrical, architectural, geology and geotechnical.
The main geotechnical challenge of the project was a horizontal discontinuity in the dam foundation that was filled with chlorite material, resulting in a lower friction reaction against the horizontal shear stress. Our geotechnical team developed a solution to counteract the chlorite based on lowering the water head at the foundation level by using dewatering galleries excavated into the rock (shale).
The geology showed a deep weathered rock horizon in the embankments, resulting in poor availability of sound rock from the mandatory excavations. Several studies were performed to prove the use of lighter material (weathered shale) inside the dam mass, which gave significant benefits in firstly avoiding the need to open a deep quarry and also removing the need to dispose of a significant volume of earthworks material.
Our technical staff were present on site during the entire construction period and reservoir filling, following and analysing of the dam's monitoring instrumentation.
Results
Two types of dam were used. The main dam is Rolled Compacted Concrete (RCC) - 90m maximum height and 240m long. The spillway and the powerhouse are incorporated.
A second dam was constructed from earthfill and rockfill - 90m maximum height and 342m long, totaling 1,342,000m3 of material.
The river diversion was through a 560m long tunnel at the left embankment with 128m2 cross-section. Design and construction of access roads and the switch yard patio were also part of our scope.
