Ricerc@Sapienza

The presented experimental study, from micro to macro scale, assesses the effects of grain shape on the strength-dilatancy behaviour and physical properties of seven natural sands of different origins and mineralogical composition. The micro-scale has been characterized by processing 2D image of grains, using the fractal analysis of particle contour to define their shape. The macroscopic material properties are evaluated performing direct shear tests at three different normal stresses, and measuring void ratios limit and angles of repose.

In this paper we analyse numerically the behaviour of an ideal sandy slope subjected to an earthquake, aiming at exploring the possible triggering and propagation of instability conditions within the domain. At the scope an advanced constitutive model is adopted within a non-linear fully-coupled dynamic finite elements environment.

A modified bounding surface plasticity model developed within the critical state soil mechanics framework is presented. Herein a modified version of the Dafalias and Manzari (2004) model is proposed, specifically de-veloped to improve its capability to reproduce the cyclic behaviour of sands under different strain levels adopting a unique set of constitutive parameters.