The deterioration of earth dams - an example: The Rendina dam

The Rendina dam is a zoned earth dam which was completed in 1956. It has a crest length of 1200 m, a maximum height of 32m and a maximum rum length of 200 m. The two supporting fills consist of sandy-clay silt and the core was obtained by an artificial mixture of gravel and pebbles, sandy-clay silt and bentonite. Some cracks began to appear in 1988, lengthwise to rite crest. They were first observed on the left side of the dam, then extended to most of the embankment. Thanks to a long series of surveys (boreholes, laboratory and in situ geotechnical trials, inclinometers, piezometers, etc, etc.) and to a painstaking and detailed study of measurements taken while the dam was being constructed, the type and extension of deterioration of the embankment could be defined. The first cause of deterioration is due to defective construction (poorly compacted layers, sand levels, etc.). Water seepage has gradually softened zones of the dams that were already comparatively loose thereby producing less resistant zones. Under certain conditions of operation, plastic failures developed locally leading to deformation of the dam. Consolidation and waterproofing works have been designed to achieve conditions of safety.