NUMERICAL STUDIES OF THE MOMENT CARRYING CAPACITY OF A SHORT PIER FOUNDATION IN A CLAY SOIL

Abstract

Numerical predictions of the immediate moment carrying capacity of a short pier foundation in saturated clay are presented. Three-dimensional finite element analyses are carried out using linear and non-linear programs and using a linear axi-symmetric program. Preliminary investigations are made to determine suitable boundary distances for analysis at full-scale and size of loading increment for non-linear analyses. Predictions of the behaviour of prototype pier and of conventional and centrifuge models of this pier are then made. It is shown that the axi-symmetric program yields significantly higher rotations per unit moment than the linear three-dimensional program and that, using both of these programs, elastic analyses of the conventional and centrifuge models and of the prototype yield very similar results. It is also shown that non-linear analyses of the conventional and centrifuge models yield significantly different moment/rotation relationship in accordance with the behaviour actually observed in the model tests. The relationship obtained for the centrifuge model is shown to differ only slightly from that obtained for the prototype, due to the boundary restrictions in the model, and to be of the same order as the centrifuge test result at working condition but not at ultimate capacity.