Author(s): Alberto Vaquero; Cesar Mayoral

Linked Author(s):

Keywords: Guistolas

Abstract: The Guístolas dam is a straight gravity dam with a height of 32 m on foundations, which forms part of the hydroelectric dam of the river Navea and specifically of the Guístolas-Pontenovo system, in the province of Ourense (Spain). Construction work on the dam was carried out between 1947 and 1952. The typical cross-section is gravity, with a vertical face upstream and an inclined face with a 0.8/1 slope downstream. The body of the dam was built with concreted masonry, with the downstream face made of faced masonry and a conventional concrete front screen on the upstream face. The spillway is located in the central area of the dam, has two 10 m long separated by a 3.5 m basin and is regulated by two 7 m high Stoney type gates. Throughout the dam's operation, in some episodes of discharges there has been damage caused by the detachment of the masonry of the discharge channel, which can be counted on four occasions over the last two decades. In view of the geometry of the spillway, it can be seen that its profile does not exactly follow the theoretical slope (0.8/1), but that the central part of the spans are somewhat sunken. This could have given rise to suction which, together with the action of filtration and ice, could have caused some of the stones with the worst grip to detach, and once the damage had been created, the strong turbulence generated during a spill caused the successive pulling out of the adjoining masonry, increasing the damage. According to the existing records, it can be seen that damage has occurred in those events in which the flows drained by the spillway have exceeded 100 m3/s. In the last episode that occurred at the end of 2019 the peak flows discharged exceeded 170 m3/s and significant areas were damaged in both spillway spans with an estimated loss of material that almost reached 50 m3. For this reason, it was decided to carry out an integral rehabilitation of the spillway, mainly involving the following activities: waterproofing of the upstream face of the dam, injection of the body of the dam in the spillway area and adjacent area on the left bank, demolition of the covering of the spillway discharge channel, construction of a reinforced concrete slab sewn by bolts to the body of the dam and with a drainage system at the base. Iberdrola's technicians were directly involved in the project, initially discussing the technical issues raised by the designer and during the execution of the works with the contractor, according to their own technical criteria

DOI: https://doi.org/10.3850/IAHR-39WC252171192022969

Year: 2022