Abstract:

 In traditional soil mechanics, the cohesion of clayey soils is often described using the macroscopic cohesion parameter c within the Mohr-Coulomb failure criterion. In this study, siloxane-coated glass particles were used to prepare controllable cohesive granular materials (CCGM), enabling quantitative control of the microscopic cohesive forces between particles, that is, polymer-bridge bonding. This approach links particle cohesion to microscopic interparticle bonding forces and shifts the description of particle behavior from a macroscopic framework to a quantifiable physical characterization. To reveal the cross-phase evolution mechanism by which cohesive particles evolve from a quasi-static state to a flowing state, this study introduces a dynamic cohesive-force expression and develops a μ(I) rheological model for cohesive particles that relates the frictional coefficient μ to the inertial number I. Based on the proposed model and the material point method (MPM) framework, a continuum-mechanics model was established to describe the full transition of cohesive particles from rest to flow. The continuum model effectively reproduces the temporal evolution process of particle column collapse and captures experimentally observed phenomena, including delayed collapse initiation, reduced runout distance, and an increased angle of repose with increasing cohesion. Experiments and simulations also show that when the cohesive number Co≥8.1 or the aspect ratio a≥2.0, the granular flow forms a radial crack network due to non-uniform energy dissipation. The research provides a theoretical framework for predicting landslide and debris-flow motion.

Key words: granule, cohesion, granular column collapse, material point method (MPM), rheological behavior