Analisi sismica di dighe in terra con modello multifase

Finite elements analysis of the seismic behaviour of earth dams is presented. The earth dam and its foundation are considered to be a porous medium and described as a multiphase continuum. The medium is hence constituted by a solid skeleton with open pores filled by water or by water and air, this last one at atmospheric constant pressure. The macroscopic balance equations of the mass and momentum are derived within the hybrid mixture theory. These equations are integrated in space and in time using the Galerkin’ s procedure and the Newmark’ s scheme respectively. The solid skeleton is considered to be elasto-plastic in which the Mohr-Coulomb and Pastor-Zienkiewicz laws are used for cohesive and granular materials respectively. The water flow is assumed to obey to the Darcy’ s law. The partially saturation conditions are described using the Safai-Pinder’ s law. Numerical computations are performed analysing the earth dam in Acciano, (Pg, Italy) subjected to the Umbria-Marche earthquake of Sept. 97 as seismic input excitation. Comparison between the damage measured on the dam after the earthquake and the finite element analysis reveals the validity of the proposed approach.