Les revêtements anti-usure des barrages du Rhône

Anti-wear coating of the Rhône dams

Compagnie Nationale du Rhône

Abstract

The anti-wear coatings of the Rhône dams. 1. General considerations - The evolutions of protection The National Company of the Rhône (CNR) has built 16 barrages on the Rhône river since 1952 for heads between 6.30 meters and 13.10 meters and projected rates of flooding of between 2 800 and 14000 m3/ sec corresponding to a maximum energy output of the order of 500 to 4 500 kW per linear meter of dam. This energy to be dissipated and the solid substances contained in the water involve major risks of deterioration of aprons through wear and tear and impact. The CNR has accordingly sought to find a material providing the most resistance to theses phenomena and also lending itself well to use in large construction worksites. The protection of dam aprons against wear has changed correspondingly. The granite rubble once used has given way to cement-corundum coatings which have in turn been replaced by synthetic resin coatings and concrete. 2. Protection using syth etic resin. In a first stage, the research undertaken uncoverred two types of protection, used for the first time at the Villeneuve-les-Avignon dam. 2.1. Epoxy - corundum tar pitch - resin coating. This coating, thickness: 2 cm, is applied to a con crete surface which has undergone the necessary preparation. The surface is prepared as follows: - elimination by Bush hammerin!! of clements which are not bound to the surface; - sanding followcd by dusting ; - Impregnation, using a brush, with 200 grams per square meter of pure resin, liquefied by addition of 10% an appropriate solvent. The coating has the following composition per cubic metre of mortar. - coal tar pitch-epoxy resin binder : 300 kg. - 0.2 to 2 mm corundum elements : 500 kg. - 2 to 5 mm elements : 2000 kg. This compound is as resistant to wear as any high-grade granite. 2.2. Resin concrete undercoating below the expoxy-cofUndum tar pitch-resin coating. A resin-concrete coating is used in certain zones of dam aprons which are subject to vibrations or cavitation. The composition of this concrete, which is as resistant to wear as a low-grade granite, is as follows: - per m3 of concrete small 5/15 gravel : 1 200 kg 1.25/2.5 sand : 600 kg 0.15/0.3 sand : 300 kg epoxy resin : 220 kg 2.3. Evolution of surface protection In addition to protection against wear, the protection against impacts has been examined. As a result, so-called simple formulations have been specified and their resistance to wear is mostly equivalent to that of soft steel. Per cubic metre of mortar, the composition of this flexible coating is as follows: - epoxy-urethane resin : 320 kg - 0.18 - 0.42 m angular hematite : 880 kg - 1.7 - 2.4 mm round hematite : 4050 kg 3. Cast of protection The least costly protection (``epoxy-corundum tar pitchresin" coating + resin concrete) adopted for the St-Pierre de Boeuf dam represents approximately 8% of the amount of civil engineering work of the faeility. 4. Conclusion The diversification of the types of protection is specifie to the design and operation of the mobile dams on the Rhône. The choice of the type of protection is subordinated to the parameters pertaining to each dam and the efficiency associated with the quality of the methods used for their construction and control.