Combined loading of spudcan foundations on clay: laboratory tests Available to Purchase

Recent research has shown that work-hardening plasticity theory provides a suitable framework for interpreting and predicting the load–displacement behaviour of rigid shallow foundations under combined vertical, moment and horizontal loading. Most previous work has, however, been restricted to footings on granular soils. This paper describes a series of laboratory tests conducted at unit gravity using a small circular footing and specimens of reconstituted kaolin. The results indicate that work-hardening plasticity concepts can also be applied to the modelling of shallow foundation behaviour on undrained clay. The footing shape chosen for the experiments is representative of the ‘spudcan’ foundations which support the legs of jack-up drilling platforms. A novel testing apparatus allows independent control of the vertical, rotational and horizontal footing displacements within a single vertical plane. Tests conducted at constant vertical penetration are used to investigate the shape and size of the combined load yield surface at embedments ranging from 0 to 1·6 footing diameters. Tests under vertical load control provide further information about the yield surface, and are used to assess the suitability of an associated flow rule for predicting plastic footing displacements. The yield surface shape determined experimentally is compared with that implied by the general bearing capacity formula of Brinch Hansen, and some significant discrepancies are highlighted.