The quarry has 200 years of activity. Since 2016, exploitation under the embankments of the former open-air quarry has started to prepare for the fully underground activity of the quarry, initiated in 2021. The site has 80 hectares underground, authorized in 2017 for thirty years, and 85 open-air hectares which are no longer exploited, but backfilled with a view to the redevelopment of the old quarry. It was on the occasion of this changeover that the thermal extraction shovels were put into service in 2016.
Materials which, even before the question of their energy supply, no longer corresponded to needs. “The exploitation was carried out using cutters and tridents. The gypsum was then loaded onto dump trucks and stored near the crusher. We had to manage five 50-ton excavators, thermal equipment, which consumed a lot of diesel and whose reliability was rather hazardous. These were not continuous production shovels, to attack the rock as they were asked to”explains Philippe Di Mascio, the operations manager of the Cormeilles-en-Parisis quarry.
One job at a time
Placo therefore opted for new equipment, called “Point Attack Machine” (MAP). “That pointed us toward equipment designed for this task, which is mining rocks. The point attack machine is designed for this: it is designed as a mini extraction workshop, which extracts the rock (with one arm) and, simultaneously, loads it into the dump trucks stuck nearby. All this is done at the same time. The dump trucks are then emptied into the open sky.continues Philippe Di Mascio. For the extraction of gypsum in France, whether at Placo or its competitors, the use of a machine of this type is a first.
Instead of attacking several small extraction fronts, the teams only follow one. Instead of ventilating the dust throughout the quarry, they are equipped with a dust collector which filters and spits air into a dedicated gallery. Underground gypsum extraction takes place in two stages. Over 6.50 meters, the workers carry out the tracing in the rock with the point attack machine. In a second step, one to two years later, they continue to dig deeply so that the gallery reaches 12 meters high, an operation called “lifting”.
New working methods for staff
100% of the tracing is carried out with the MAP, while the lifting is, today, still carried out with thermal excavators. In fact, Placo estimates that its new machine is now contributing to the 50% reduction in carbon emissions linked to gypsum extraction on the Cormeilles-en-Parisis site. To accommodate the machine, Placo installed a 1000 volt power station powered by cable. With between 400 and 500 meters of possible shelving, the organization of the work will be gradually rethought.
Another change brought about by the arrival of the new machine is that of the organization of work. Previously, the staff remained practically on the machines from morning to evening. 70% of working time is now devoted to operating the machine, but there is more preparation time upstream, with the installation of dust extraction ducts or monitoring of installations. “On thermal excavators, extraction depended on the dexterity of the driver; on the MAP, the driver launches an extraction program and must be more supervised”describes Philippe Di Mascio.
To support the change, management organized working groups for its seven machine operators and its two team leaders and carried out visits to the Sandvik factory, and to mines and quarries where the same type of equipment is used. In England, one of the group’s quarries has a similar machine, but of a different size. Two weeks of certification training followed. “The machine is no less noisy outside, the cabin is soundproofed. There are fewer vibrations, since the cabin is separated from the extracting arm.illustrates Philippe Di Mascio, who is also satisfied with no longer needing to refuel. Its delivery is part of Saint Gobain’s objective of being “net zero carbon” in 2050.
Source: www.usinenouvelle.com
