The Rabaçal Hydropower project is located nearby the Bouçoais and Sonim villages, in the Rabaçal River, a sub-affluent of the international Douro River.
The hydraulic circuit, installed between the reservoir and the power station, comprises a tunnel with a length of nearly 1.350 m excavated in the granite formation of the right bank of the river and a 65 m length forced water pipeline. The excavation diameter is 4,20 m. The tunnel is concrete lined in sections where required, with a thickness of 0,30 m.
The occurrence of a fault intersection in the tunnel, a landslide in the left side (“rib”) and the existence of potential areas of collapse, associated with extensive subparallel discontinuities in the tunnel, made necessary to reinforce the tunnel in a section of 40 m.
The study carried out aimed to define appropriate solutions to the adduction tunnel’s critical section, for execution phase, which could add value in terms of deadlines and costs without jeopardising the stability and safety.