GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 2.2 387 Fig. 2 - Results of Monte Carlo simulations for fluvial and marine terraced deposits in terms of (a) maximum shear strains and (b) acceleration response spectra. the effect of the Vs profile inversion is more evident respect the case of cliffs and lava rocks and the case of fluvial and marine terraces, respectively, due to the fact that higher values of the contrast of impedence and of H soft are expected in the last case with respect to the first two. Of course, there is also an effect due to the intensity of the input motion that controls the deformation level reached in the soft soil layer. The obtained results can be considered representative of one-dimensional conditions, so any morphological effect can modify the expected behavior. Conclusions. The most common Italian geological domains exhibiting Vs profile inversions have been identified and studied in terms of geometrical and geotechnical properties. The results of this preliminary study are the input data to carry out a parametric study of 1D site response analyses to investigare the effect of Vs inversions in such conditions. In general, the surface motion response is attenuated with respect to the outcrop. This effect is emphasized with V s and H of the soft layer increasing, that is the real controlling layer. The increasing of the input motion too increases this effect because of soil nonlinearity. Vs profile inversions are particular and complex geological conditions for which numerical site response analyses are required to better predict the seismic behavior of the colums for design considerations. These conclusions are valid in 1D conditions; in more complex morphological conditions, that can lead also to 2D conditions, the effect of Vs profile inversions can be surpassed by the morphological effects.