Performance based seismic analysis of an existing rockfill dam,

The paper reports a numerical analysis of the performance of the seismic response of a bituminous faced rockfill dam located in southern Italy. A brief description of the principles of PBSD is initially presented, as provided by current codes and guidelines and specifications for the analysis of dams. Then performance objectives are defined in terms of accepted accelerations and movements with reference to safety levels suggested in the literature. A deterministic spectrum-compatibility method, particularly customized to the Italian codes (M.LL.PP. 2008) and to the hazard of the site where the dam is located, has been adopted for the selection of the input time histories. A two dimensional numerical model has been then created to geometrically reproduce the embankment and its foundation. The stress-strain response of the coarse grained material forming the embankment has been simulated with a visco-elastic perfectly plastic constitutive model, adapted to introduce the dependency of stiffness and strength parameters on the stress components as observed in previous experimental studies. A detailed description is given to the calibration of the parameters of this model, based on a comparison with the results of laboratory tests. The performance of the numerical model has been initially tested by comparing simulations with the results obtained on a small scale centrifuge model of the dam. Finally, an analysis of the full scale performance of the dam is made with respect to limit states defined in the European code (EN, 1998). The results are presented, accordingly with observations provided in the literature, by relating the residual horizontal and vertical displacements to the maximum accelerations applied at the dam’s base.