Study on size effect and crushing characteristics of gangue-filling material under the confined compression

The diameter, particle size distribution, and diameter-height ratio of coal gangue backfill material directly affect its mechanical behavior. This study investigated the influence of different particle sizes on the bearing characteristics and particle breakage of coal gangue backfill material under constrained compression through orthogonal experiments. A numerical model of randomly geometrically filled stones under compression was developed to reveal the micro-damage mechanism of coal gangue backfill material under different particle size effects. The results indicate that the diameter Rd of coal gangue backfill material has the greatest impact on its mechanical behavior, followed by the particle size distribution Rg, with the diameter-height ratio Rd-h having the least impact. The diameter significantly affects the compressive strength of the samples, with larger diameters leading to poorer initial force chain stability and lower compressive strength. The particle size distribution has a significant impact on sample breakage, with the breakage rate and fractal dimension increment being negatively correlated with the initial particle size distribution. Particle breakage in the samples gradually progresses from the periphery towards the center, with tensile failure being the primary mode of damage.