Numerical investigation on the modal properties of slopes

Earthquake-induced displacements of slopes are often evaluated through decoupled approaches combined with empirical relationships accounting for the characteristics of the input motion and the dynamic properties of the sliding mass. As per the latter point, recent studies highlighted the key role played by the system modal properties on the slope performance. Notwithstanding, the natural periods of the slope are commonly evaluated through over-simplified expressions relating to homogenous soil deposit with horizontal ground level. With the aim to provide a more realistic and comprehensive dynamic identification, this study presents a numerical investigation on the modal features of slopes with planar slip surface, implemented in the analysis framework OpenSees. The consideration of several slope geometries and mechanical properties point out i) the influence of the soil incompressibility, of particular interest under saturated conditions, and ii) effective ranges for the multiaxial modal periods and participation masses as a function of the soil stiffness. The results of the parametric study are finally used to derive a practice-oriented identification procedure of the modal features of slopes, as starting information for calibrating simplified numerical tools devoted to their large-scale assessment.