Granular lift induced by confinement: Mechanism and modeling

Granular lift has attracted sustained attention over the past two decades due to its central role in governing the dynamics of objects moving within granular media, with direct relevance to excavation, robotic locomotion, and resource exploration. Despite significant progress in uncovering phenomenology and developing models, a first-principles understanding of granular lift remains elusive owing to the inherent complexity of granular physics. In this study, we employ discrete element method (DEM) simulations to reveal a lift-generation mechanism intimately associated with granular confinement and develop a theoretical model for predicting granular lift. We demonstrate that granular lift originates from the formation of a stable confined region, induced by geometric confinement between the intruding surface and the underlying stable granular layer. Within this confined region, lift and drag are linked by a geometry-dependent mathematical relation, which relates the lift force to the granular drag predicted by the plastic flow theory. The proposed lift model not only clarifies how drag contributes to lift in granular media but also demonstrates strong predictive capability when validated against DEM measurements. These results advance the fundamental understanding of the fluid-like nature of granular media and offer insights into the dynamics of soft matter–intruder interaction systems.