In recent days, at the Olivettes dam, in Vailhan (Hérault), astonishing underwater robots have probed the depths of the Peyne. This meticulous operation is not intended to uncover remains, but to ensure that the hydraulic structure, built in the late 1980s, shows no signs of ageing.
Such monitoring, carried out by the department of Hérault, owner of the dam, is “crucial”. This “very precise inspection” makes it possible “to identify the presence of possible defects in its structure”, indicates Séverine Saur (PS), departmental councilor and president of the water management commission of the Olivettes dam. And to see whether the structure, which retains 2.9 million m3 of water, is still operational, to ensure the missions entrusted to it, 35 years ago, during its construction: supporting irrigation in surroundings and to limit the floods of the Peyne.
Robots to avoid draining water from the dam
Jifmar, a company specializing in hydraulic maintenance, piloted the robots at Les Olivettes. A few months ago, aerial inspections had already been carried out by drones, with millimeter precision, then divers had cleared the surroundings of the dam of algae, mussels and mud which tend to accumulate there. This exploration of the site by state-of-the-art machinery was the last phase of the inspection of the dam. “These robots make it possible to carry out a very detailed inspection of the structure, explains Jean Delarbre, engineer at Jifmar, in charge of this project. This makes it possible to complete the studies that are carried out on the emerged parts of the dam, and to access areas that would only be accessible by divers or by emptying the structure. And that, emptying the Olivettes, would be very expensive. And above all, it is not very ecological. Especially in these times of drought.
These ultra-sophisticated robots are equipped with several cameras. And if, as is sometimes the case, the water is cloudy, these machines, piloted from the surface by engineers, are also equipped with acoustic sensors, which can take over from the cameras. Once immersed, they make it possible to detect cracks or faults in the structure, which could cause leaks or accidents. By regularly immersing these droids in the depths of the Peyne, it makes it possible to observe their evolution, and to act, if necessary. “But very often, there is no need to repair, continues the engineer. When we talk about cracks, they are cracks of the order of a millimeter. Large openings are really very rare. And when they exist, we already know it. What is above all very important is to follow the evolution of these cracks. Some structures have cracks, but they do not evolve. They are under control. »