A seismic parameter for the prediction of crest settlements of earth dams induced by horizontal and vertical input motions

2D numerical analyses have been performed with the aim of evaluating the seismic performance of the San Pietro dam subjected to a large set of horizontal seismic motion and both horizontal and vertical components of the seismic motion acting simultaneously. In the analyses the soil behaviour has been described using an isotropic hardening elasto-plastic hysteretic model and a set of 58 horizontal and vertical components of earthquake records has been applied at the base of the model in both upstream and downstream directions. The results of the analyses allowed assessing the effect of the vertical component of the seismic motion on the activation of plastic mechanisms induced by the seismic loading and the vertical displacement of the crest. The vertical displacements of the crest of the dam have been scrutinized along with various seismic parameters, with the aim of detecting a reliable empirical correlation between the crest settlement and the relevant characteristics of the seismic motion. Therefore, an original seismic intensity measure, consisting in a combination of seismic parameters (IA-Tm-PGV) of the horizontal and vertical component of the seismic motion, has been detected and an empirical formula has been calibrated allowing a prompt prediction of the expected crest settlement of the San Pietro dam for both cases of only horizontal and horizontal and vertical input motion. The effectiveness of the proposed intensity measures has been verified against numerical results available in the literature for other earth dams.