ABSTRACT
The Venda Nova III hydropower project is a key component of a hydroelectrical scheme, in the North of Portugal. This underground hydraulic circuit consists of headrace and tailrace unlined tunnels with 12m diameter, amounting to 5km in length, several construction galleries and a new powerhouse, reaching over 1000000m3 of underground excavations. Those characteristics, associated to the high-water head, that can reach 480m, imposes many challenges of great complexity, during the geological survey and namely during the construction phase. A relevant fault zone intersected the main circuit as well some of the construction galleries and brought several challenges during the construction phase. Was the geological investigation during the studies phases enough? An overview of the Venda Nova III Hydropower Project experience is performed; a review of the state of research to overcome these persistent geological issues is presented, as well as proposals for future studies on these subjects.
