Influence of field modulus non-linearity on pile settlement

In the paper a new approach, based on the idea above indicated and on the elastic solution by Randolph and Wroth (1978), is proposed. The main difference is that non-linearity is taken into account not resorting to a backcalculated “operational stiffness” but directly using a “typical” shear stiffness degradation curve, deduced from laboratory tests, and introducing “pseudostrain” values to be used in accordance to the decay curve. The "pseudo- strain” is evaluated according to field performance: so it is possible to pass from a laboratory modulus non-linearity to a field modulus non-linearity. The assumed “pseudo strain” is directly the ratio between the settlement w (at the head of the pile) and the diameter D (i.e. the relative settlement) or a shear strain g, function of the pile settlement. Starting from the knowledge of the soil initial stiffness and pile characteristics, a complete non-linear load settlement curve can be evaluated.