A sinkhole is a sudden collapse of the ground, often triggered by the progressive disintegration of an underground cavity. In cohesive or karstic soils, this process begins when the roof of a cavity weakens and gradually forms a bell-shaped void that eventually reaches the surface. In Paris, centuries of underground quarrying have made the subsurface particularly prone to such collapses. The shape and dynamics of sinkholes depend on multiple factors — cavity size, soil cohesion, and surface structures — making them difficult to predict from field data alone. To better understand these mechanisms, a 2D laboratory experiment will be carried out using a cohesive granular medium with tunable adhesion. After removing the underlying support, the formation and growth of the cavity will be studied as a function of grain size, cohesion, and orifice size. The goal is to identify distinct collapse regimes, from gradual deformation to brittle fracturing, and to explore possible scaling laws and self-similar dynamics. Field measurements in Nature or in Paris’ quarries with Inspection Générale des Carrières (Mairie de Paris) can also be included, depending on the candidate’s interests.