The paper reports an experimental study and parameter calibration exercise centred on the hydro-mechanical response of an unsaturated soil. The study benefits from compacted silt samples retrieved from a fully instrumented experimental embankment, which was built under poorly compacted conditions to study the collapse response upon artificial flooding. In addition to the hydraulic characterisation, the experimental programme includes controlled-suction tests intended to follow similar wetting and drying paths to those undergone by the material under real conditions. The suction dependent elastoplastic BBM model is used to simulate selected experimental results related to the collapsible behaviour (its time evolution and its response with decreasing suction). Mechanical and hydraulic parameters of the model are determined by both direct experimental procedures and numerical back analysis.