Seismic safety against base sliding of concrete gravity dams

Seismic safety against base sliding of Italian concrete gravity dams subjected to strong earthquakes is reached by means of a simplified procedure. The mechanical model is represented by a single degree of freedom system having dynamical characteristics which take into account dam-water-foundation interaction. To catch plastic displacement the non linearity of the substructure is modelled, having fixed a threshold value for the sliding foundation resistance presented with the Mohr-Coulomb yielding criterion including a frictional and a cohesive component. The positive effect of a passive wedge resistance is also included. Non linear dynamic response to several natural earthquakes is evaluated for typical examples of Italian concrete gravity dams, considering the effect of different foundation rocks. On the basis of the obtained results a simplified procedure to have a first estimate of the base sliding without performing non linear analysis is proposed.