Author(s): Marcelo Leite Ribeiro; Jean-Louis Boillat; Anton J. Schleiss; Frederic Laugier; And; Claude Albalat
Linked Author(s): Anton J. Schleiss
Keywords: Dam rehabilitation; Labyrinth weir; PK-Weir; Effective overall crest length; Rating curve
Abstract: Labyrinth weirs are normally built to increase the total effective crest length for a given spillway width. They can be used to increase the discharge capacity for a given head or to decrease the head for a given discharge. As their application is sometimes difficult in rehabilitation projects due to inappropriate supporting conditions, a new concept of labyrinth spillways has been proposed with a new shape, called PK-Weir (Piano Key Weir). This innovative alternative of labyrinth spillway provides an increase in the stability of the structure which can be placed on the top of most existing or new gravity dams, unlike traditional labyrinth weirs. In this framework the results of physical modelling tests for the rehabilitation of St-Marc Dam with a PK-Weir are presented. A conceptual model for fitting the rating curve of the PKWeir of St-Marc is proposed, based on the loss of effective length with the increase of the upstream head. Original developments are presented concerning the crest geometry of the weir, the energy dissipation inside the structure itself and the nappe aeration of the overtopping jets.