Scale effect on bearing capacity of shallow foundations on strain-softening clays

Progressive failure is common in many natural clays of strain-softening behavior and may affect the bearing capacity of foundations placed on such soils. The progressive failure might be insignificant for small structures where the mobilized strains are generally uniform within the failed soil mass. This places a demerit to the applications of knowledge obtained from physical model tests to prototype. The study aims to understand and quantify this scale effect on bearing capacity of shallow foundations on strain-softening clays, with a numerical investigation using a large deformation finite element analysis. The progressive failure is numerically replicated and the controlling parameters for the bearing capacity have been discussed. A correction factor is introduced which is inversely proportional to the foundation size normalized by the proposed characteristic length. An empirical relationship of the correction factor and the normalized foundation size has been obtained via the numerical data, which may improve the design of shallow foundations on strain-softening clays.