Physical modelling of shallow foundation behaviour on collapsible unsaturated silt

Despite significant advances in laboratory testing of unsaturated soils, well-controlled boundary value data remain limited, while coupled hydro-mechanical constitutive models and numerical tools are increasingly used in practice. In this context, physical modelling provides an intermediate-scale approach to investigate field-representative behaviour and to support model validation. This study presents a series of 50g centrifuge experiments on a prototype shallow foundation (1.5 m diameter) founded on a compacted unsaturated silt layer. The investigation focuses on wetting-induced collapse due to water table rise and the bearing capacity of shallow foundation under fixed water level position and during wetting process. Suction profiles were monitored in flight at 50g using high-capacity tensiometers, which showed reliable performance. Results demonstrate that collapse induced by capillary rise can be effectively reproduced in a loosely compacted silty soil, with deformations concentrated in the lower part of the layer. A marked reduction in bearing capacity is observed as suction decreases. Experimental results are interpreted through coupled numerical analyses providing an insight into the mechanisms observed. The combined approach offers a robust framework for analysing geotechnical systems in unsaturated soils.