Improved method for settlement prediction of shallow foundations on sand

Shallow foundations on sands are typically designed with reference to settlements that are, in turn, difficult to predict with a high level of accuracy. The main uncertainties originate from soil non-linear behaviour and by the fact that methods currently adopted in practice rely on linear elastic approaches and empirical correlations between soil stiffness and in situ test results. To improve the prediction of foundation settlement it is necessary to account, even in relatively simple methods, for the dependence of stiffness on soil density, stress state, strain levels. The main objective of the paper is to provide a contribution in this field. An already formulated elastic approach is revised and modified in order to improve the assessment of soil stiffness, taking into account non linearity due to strain levels and to mechanical non-homogeneity as well, through a definition of the “active zone”, more consistent with the geometry and size of the foundation. The comparison among calculated and measured settlements highlights the feasability of the proposed non-linear method both for small and large deformation levels.