Unjamming and yielding of intruder-deformation-driven dense granular materials

Abstract

Dense driven granular materials have garnered significant interest due to their complex rheological phenomena such as dynamical heterogeneities and frequency dependence. However, the unjamming/yielding transition induced by intruder deformation, which is critical for applications in living matter interactions with sand and foundation-soil, remains poorly understood compared to boundary- or friction-driven granular systems. To address this knowledge gap, we first study the relaxation dynamics of granular medium driven by oscillatory intruder deformation, and the evidence of an abrupt unjamming/yielding transition in frequency domain is provided. The evaluation was performed by combining the bulk rheology manifested as the temporal evolution of beam deformation, dynamical and mesostructural heterogeneities. We find that the transition is characterized by the emergence of vortices, which cause shear bands accompanied by superdiffusion, transforming spatial correlations from exponential to power-law decay. This study demonstrates the potential for controlling and predicting elastic and flow properties in the intruder-deformation-driven flow and provides future theoretical or numerical modeling of active mesorheology through comparisons with complex fluids and boundary-driven scenarios.