Microscopic mechanisms of particle size effect on 2D arching effect development and degradation in granular materials

This study carries out a series of DEM numerical simulations to investigates the microscopic mechanisms of arching effect development and degradation in classical 2D trapdoor problem with different mean particle sizes. Both the macroscopic and microscopic behaviours of particles under the influence of arching effect are examined. The simulation results of the granular assembly above a displacement-controlled trapdoor are divided into three zones: a shield zone; an arch zone and a stable zone, according to the extent of particle vertical displacement for analysis. The impacts of the mean particle size relative to trapdoor width on various zones are carefully evaluated. Microscopic parameters, including the friction mobilisation index, the average coordination number, and the mean particle contact force, are found to be all influenced by the mean particle size and show different behaviours in the three zones. The average particle contact force within the arch zone shows the highest correlation to the evolution of arching effect in particle samples with different particle size. These findings not only provided new insights into the correlation between the particle scale mechanisms and the macroscopic arching effect but also highlight the mean particle size influence on the evolution of arching effect in granular materials.