Nonlinear response of undrained clay to footings

Abstract

An analytical study of the static response of a homogeneous undrained clay stratum to footing loads is presented. Clay is modeled as a linear elastic-perfectly plastic material with the von Mises yield condition and associated flow rule. The effect of large deformations on the response of the clay is included in the analysis. Numerical results are obtained within the framework of the finite element method and a step-by-step integration procedure. In particular a single, strip surface footing bearing on a finite stratum of undrained clay is considered. The footing is assumed to be rigid and the interface between the footing and soil may be either smooth or rough. The base of the soil stratum is rigid and perfectly rough. A plane strain condition is assumed. Load-displacement curves, stress distributions, zones of yielding and velocity fields are presented. It was found that for a rough footing bearing on a undrained clay, the mode of failure corresponds to the so-called Prandtl velocity field. For a smooth footing, however, the failure mechanism appears to be a combination of the Hill and Prandtl type velocity fields.