The Cammazes Dam is a 70m high arch, built at the end of the 1950s. During its construction, it was noticed that the geological conditions were not as good as expected. The project was modified and the designer chose to build a large abutment (approximately 25m high) on this bank. The abutment consists of two shells which are burrowed into the bank and which are extended into the foundations by Bioge excavations.
The stability of this part of the dam was regularly questioned.
In 2001, an irreversible shift towards the bank was recorded by the pendulums. Investigations and a detailed calculation of the stability of the abutment confirmed the possibility of such irreversible shifts. Moreover, the calculations show the harmful effects of situations such as the hot summer of 2003.
A call for proposals was launched by the client to identify the best adapted strengthening solution.
ISL’s solution was chosen: the land, up to the Bioge excavations, between the two shells was removed; a thick slab was built between the two shells and backfill was placed over it. Wide drainage was installed. The works were carried-out in 2004. The dam’s examination equipement was reinforced. The reservoir was filled up to its nominal level. No pathology was recorded. The French Dam Committee communicated about this operation.
ISL provided most of the services for this dam. In 1988, ISL was the constracting authority for a drainage gallery under the right bank. In 2001, ISL prepared the PPI dossier. From 2003 to 2005, ISL carried-out the strengthening of the right bank abutment: solution outline, design, the CTPB file, the visa for the execution studies, works supervision, reception assistance.
ISL carried out the Risk Assessment study for the dam.
