Simple plasticity-based prediction of the undrained settlement of shallow circular foundations on clay

A kinematic plastic solution has been developed for the penetration of a circular footing into an incompressible soil bed. In this solution, the pattern of deformation around the footing is idealised by a simple plastic deformation mechanism. Strain-hardening behaviour and nonlinear stress-strain characteristics are incorporated. This application is different from conventional applications of plasticity theory as it can approximately predict both stresses and displacements under working conditions. This approach therefore provides a unified solution for design problems in which both serviceability and safety requirements are based directly on the stress-strain behaviour of the soil. The design strength that should limit the deformations can be selected from the actual stress-strain data recorded from a carefully specified location, and not derived using empirical safety factors. The validity of this design approach is examined against nonlinear finite element analyses and field measurements of foundations on clay under short-term loading.