Chambon Dam Reinforcement Works

Chambon, a 137 m high concrete gravity dam completed in 1935, is affected by severe alkali-aggregate reaction, causing several types of pathologies as a result of the concrete expansion. They mainly result in important vertical cracking of the structure, likely to affect its integrity under earthquake, important shear stresses in the structure and deformation of the crest. Reinforcement works were performed from 1991 to 1997 to guarantee the safe operation of the dam: mainly a series of slot cutting, and a drained PVC sealing geomembrane system, installed to provide waterproofing protection at the upstream face. These measures allowed an extension of service of 20 years. New reinforcement works were performed in 2013-2014, in the continuity of those already performed in the 1990 s: (i) installation of 415 prestressed tendons crossing the structure from upstream to downstream, supplemented with a carbon fiber composite net on the upstream face, (ii) realization of 7 vertical diamond wire slot cuts and (iii) replacement of the existing sealing geomembrane to allow the works. This paper explains the approach that led to the choice of technologies based on the results of investigations and finite elements modeling.