Mechanical properties and damage evolution characteristics based on the acoustic emission of gangue and high-water-content materials based cemented paste backfill

The long-term, continuous, high-intensity mining of coal resources has caused surface settlement, collapse of surface buildings, and stacking of gangue on ground. Backfill mining with high-water-content materials, as one of the core techniques in green coal mining, can control strata movement and surface settlement, while it fails to dispose of coal gangue. To dispose of coal gangue at large scale, single factor alternative tests were designed based on backfill mining with high-water-content materials and high-water-content materials were used as the binder and gangue as the aggregates. Furthermore, the mechanical properties and damage evolution of gangue and high-water-content materials based cemented paste backfill (GHW-CPB) under three main controlling factors (gangue particle size, gangue content, and water-cement ratio) were studied. The following conclusions were drawn: 1) GHW-CPB shows ductile failure under uniaxial compression and the material has high residual strength, exhibiting good stability after reaching the peak bearing capacity. 2) Relation equations of the three main controlling factors with the uniaxial compressive strength (UCS) and elastic modulus of GHW-CPB are obtained through regression, thus revealing the evolution of the mechanical strength of GHW-CPB. 3) Acoustic emission (AE) and failure characteristics of GHW-CPB in three periods in the uniaxial compression process are determined by using the monitoring systems for crack development and propagation. In addition, the damage equation of GHW-CPB is established based on the cumulative AE count, thus further revealing the damage evolution of GHW-CPB under uniaxial compression. These results provide a theoretical basis for the implementation of backfill mining with GHW-CPB.