Quelques exemples de dégradation des bétons par cavitation dans des ouvrages hydroélectriques

Abstract

In 1965 the Hydraulic Production Section of Electricite de France carried out a survey of cavitation damage to concrete among operational structures. Twenty cases were observed, resulting in the following findings:- 1) Cases of erosion were fairly infrequent; 2) Comparatively major damage usually occurred after exceptionally prolonged operation (e.g. after passing part or the whole of the flow diverted through the relief arrangements during staggered starting-up of power sets; 3) More severe damage seems liable to occur with the two following types of flow:- a) Moderate mean flow velocities (10-20 m/sec) with considerable turbulence, b) High mean flow velocities (above 30 m/sec) with little turbulence. Relief works belong to category (a). Their energy dissipation arrangements frequently seem to require full sheeting protection. Where high flow velocities are experienced, e.g. in bottom outlets, careful surface outline design and a smooth finish are important factors in preventing rapidly spreading damage.