Morphology Evolution and Compaction Behavior of Gangue Particles under Abrasion: An Experimental Study

Abstract

Backfill mining is widely used to control strata movement and mitigate rockburst hazards in deep coal mines, and its effectiveness strongly depends on the compaction behavior of the backfill material. However, how abrasion that gangue particles experience during transport modifies their morphology and, in turn, governs their subsequent compaction response has received little systematic attention. In this study, gangue particles sized 10-30 mm were subjected to Los Angeles abrasion tests at five revolution levels (0, 250, 500, 750, and 1000 r). Three-dimensional scanning was used to extract morphological parameters - flatness and sphericity - followed by confined compression tests to evaluate compaction performance. The results suggest that the abrasion loss increases approximately linearly with revolution count. After 1000 r, the mass proportion of 25-30 mm particles was only 12.5%, while particles smaller than 1.7 mm accounted for 29.9% of the total mass. This redistribution of particle sizes increased the initial tapped density from 1.370 to 1.769 g/cm3. Morphologically, abrasion continuously reshaped the particles, rendering them smoother and more equiaxial. Flatness generally decreased with increasing revolutions, with the 15-20 mm range exhibiting the largest drop (0.23). Meanwhile, sphericity increased from a range of 0.796-0.813 to 0.843-0.871. Compaction performance also improved markedly: the secant modulus for the main loading stage (2-16 MPa) increased from 80.77 to 156.40 MPa, with a pronounced surge occurring between 500 and 750 r. The final axial strain decreased from 0.206 to 0.106 - a reduction of 48.5%. The abrasion process can be divided into three stages: mild modification (0-250 r), rapid improvement (250-750 r), and stabilization (750-1000 r). The strong correlation between abrasion loss and final axial strain further suggests that sieve-based abrasion measurements may provide a rapid proxy for evaluating the compaction state of gangue backfill, offering a quick assessment tool for field applications.