Study on Frequency-Domain Shear Stress Characteristics and Flow-State Transitions Mechanism of Granular in Landslides

Landslides are essentially processes of granular materials undergoing flow instability under shear stress, where variations in the viscosity of the granular system directly control the initiation, cessation, and acceleration of slope movement. Therefore, investigating the jamming phenomenon in granular assemblies is of great significance for understanding landslide mechanisms and the shear behavior of granular materials. In this study, a signal analysis approach combining fast Fourier transform and empirical mode decomposition was applied to ring shear tests, aiming to quantitatively characterize the transitions between jammed and unjammed states from a frequency-domain perspective. Experimental investigations on glass bead assemblies with different particle size distributions reveal that the density of the contact network and the inertial effects of particles govern the frequency ranges of shear-dominant mechanisms. For example, in specimen S-2, the dominant frequency of IMF4 was identified as 0.22 Hz, corresponding to large-scale periodic reconstructions of the force-chain network, which marks the transition of the system from an unjammed to a jammed state. This study not only uncovers the frequency-dependent evolution of shear-dominant mechanisms in granular systems with varying particle sizes but also introduces the concept of a critical frequency as a criterion for distinguishing between jammed and unjammed states. The proposed index provides new quantitative insight for predicting landslide failure and early warning of geological hazards, while also offering guidance for the stable control of industrial granular flows.