Seismic behaviour of large earth dams: from site investigations to numerical modelling

This paper presents selected results from the study on the seismic behaviour of a large earth dam. The study relies on the availability of field and laboratory tests, as well as on monitoring data collected during the construction and impounding phases. Specifically, a two-dimensional numerical model was calibrated by comparing the settlements of the dam measured during the construction with the computed values. Iterative pseudo-static numerical analyses were carried out to investigate the plastic mechanisms forming under critical conditions. The seismic performance of the dam was then evaluated through a series of dynamic analyses in terms of effective stress. The results evidenced that a significant reduction of the seismic energy is obtained if the deformability of the bedrock is accounted for in the analyses, resulting in lower permanent displacements of the dam body, and, conversely, the vertical component of the seismic action induces a sensible increase of the seismic displacements.