Experimental Study on Nonuniform Compaction and Re-Crushing Behavior for Crushed Coal Gangue Under Axial Loading

The crushed coal gangue particles are widely used in solid backfilling. However, the nonuniform compaction and internal re-crushing behavior of crushed coal gangue under bearing stress have not yet been revealed in current research. But this is particularly significant for improving the filling effect and quality. In this article, with the aid of the innovative compaction-acoustic emission (AE) test approach, the internal re-crushing properties of crushed coal gangue were studied. The main findings are listed; 1) the variation of AE parameters versus time is highly consistent with three stages of axial compression deformation; 2) the AE location and variation of AE intensity show that there are nonuniform compaction and layered re-crushing phenomenon in the compaction process of crushed coal gangue. The particle re-crushing transfers from the middle layer to the upper and lower layers; and 3) the particles screening results of the final compaction state show that the original particle size of the upper, middle, and lower layers account for 62%, 66%, and 76%, respectively, confirming the existence of layered crushing. The layered re-crushing characteristics of granular filling materials are revealed for the first time in this article.