Presa de Grandval

This important project is situated on the top section of the river Truyere, within the region of the French Central Massif. The dam has been constructed by the Electricité de France. The total hydroelectric development project in this zone involves six dams and six power stations, to exploit an overall hydrostatic head of 520 ms. The water accumulated by these dams has a maximum volume of 540.10⁶ cubic metres, and will produce a yearly output of 1450 .10⁶ kWh. The Grandval dam rests on strong microschistous rock folds. Its length is 330 ms, and its maximum height 88 ms, measured from the foundation base. Structurally it is formed by a series of vaults supported by abutments, which are spaced at 50 ms intervals. The mean thickness of the vaults at the base is 4.90 ms, and 1.50 at the crown. The vertical slope on the upstream side is 0.70. A feature of this design is that the vaults are not uniformly cylindrical up to the top, as is customary. The top part of the dam consists, in fact, of a small gravity dam, resting on the underlying vaulted structure. The dam is straight at the top, and a road runs along it, on an overhanging structure. The dam has a surface spillway, which is ski jump shaped, and runs over the two abutments on either side of the power station.<br><br>Esta importante obra se halla situada en el tramo superior del río Truyère, en la región del Macizo Central francés. Las presas se han realizado por cuenta de Electricité de France. El conjunto del aprovechamiento hidroeléctrico tiene seis presas y otras tantas centrales que aprovechan un salto total de 530 m de altura, y las aguas almacenadas en un embalse cuya capacidad total se eleva a 540x10⁶m³ que proporcionarán una producción anual de 1.450x10⁶ kWh. La presa se apoya sobre un banco microesquistoso, que en algunas partes presenta grandes pliegues de gran potencia. El dique de cierre tiene una longitud total de 330 m y 88 m de altura máxima, a partir de la base de cimientos. Su estructura está constituida por una serie de bóvedas que se apoyan en contrafuertes. La luz entre éstos es de 50 metros