Centrifuge modelling of shallow foundations on firm over soft layered clay

In practice shallow foundations are rarely simply founded on a homogenous soil beds hence there are uncertainties surrounding the mode of failure that will prevail and the bearing capacity factor that should be adopted in design. A series of centrifuge model tests on surface strip footings resting on a layered soil bed having firm clay overlying soft clay of varying thickness are presented. Plane strain test conditions enabled the use of Digital Image Correlation (DIC) to determine the relative displacement of the soil and reveal the foundation failure mechanics. Complementary numerical modelling is also conducted which verifies the model experimental data. General shear and punch failure were observed and the dominant failure mechanism shown to depend on the ratio of the upper layer thickness and footing width.