Experimental Study on Properties of Rock‐Cemented Coal Gangue‐Fly Ash Backfill Bimaterials with Different Coal Gangue Particle Sizes

Abstract

Properties of rock-cemented coal gangue-fly ash backfill (CGFB) bimaterials determine the effects of strip CGFB mining on controlling the surface subsidence in coal mines, which are affected by the coal gangue particle size in CGFB. In this paper, uniaxial compression tests were conducted on the coarse sandstone-CGFB composite samples with different coal gangue particle sizes, and their strength, acoustic emission (AE), and failure characteristics were investigated. The uniaxial compressive strength (UCS) and elastic modulus of the composite sample decreased with the coal gangue particle size. The strength of the composite sample is mainly dependent on that of CGFB in it, affected by interactions between CGFB and coarse sandstone. The deformation of the coarse sandstone weakened the damage accumulation within CGFB, resulting in the strength of the composite sample larger than that of CGFB. The average UCS values of composite samples with coal gangue particle sizes of 0∼5 mm, 5∼10 mm, and 10∼15 mm, increased by 10.78%, 14.98%, and 12.70% compared with CGFB in them, respectively. AE event signal regularity of the composite sample was divided into three stages: rising period, calm period, and active period. The intensity and frequency of AE event signals in three periods were strengthened with the coal gangue particle size. The calm period can be taken as the precursory information for the failure and instability of composite sample under loading, whose duration became shortly with the coal gangue particle size. The rebound deformation of coarse sandstone caused the fluctuations of AE event signals at the later stage of active period. The failures of the composite sample occurred within CGFB, and no obvious failures were found in the coarse sandstone. The CGFB mainly experienced the splitting failure accompanying by varying degrees of surface spalling failures. The broken degree of CGFB increased with the coal gangue particle size, and the largest weight ratio of CGFB fragments (chips) after failure was determined by the coal gangue particle size.

Experimental Investigation of the Effects of the Gangue Particle Size on the Evolution Rules of Key Seepage Parameters

“…The filling materials mainly consisting of different sizes of gangues are essentially a kind of discontinuous media [29][30][31][32], which themselves change in the compaction process.…”

A Method of Backfill Mining Crossing the Interchange Bridge and Application of a Ground Subsidence Prediction Model

“…(2) Material and size selection of barricade Regarding the material of the filling barricade, concrete, sand, and gravel can be selected [45,46]. The selection of high-water materials has advantages over other materials due to its fast load-bearing characteristics.…”

Influence of Mass Concentration on Microstructure and Pore Structure of Coal-Gangue-Based Green Cemented Filling Body

“…Tere are many factors afecting the performance of the flling body. In [10][11][12][13], the authors studied the working performance and uniaxial compressive strength of the mine flling paste with diferent mix ratios and coarse and fne aggregate types. Zhang et al [10] mainly studied the efect of diferent watercement ratios on the performance of iron ore tailings flling paste.…”

“…Trough testing its workability and strength, it was found that the optimal water-cement ratio was 0.4, but the general applicability was not known. Wang et al [11] analyzed the change of strength by changing the particle size of coal gangue in rock glue gangue fy ash fllings, and found that the increase of coal gangue particle size would lead to the decrease of flling body strength. Jia and Feng [12] and Feng et al [13] used waste concrete as fne aggregate and coarse aggregate, respectively, to replace coal gangue to prepare flling paste and studied the infuence of waste concrete coarse and fne aggregate on the performance of flling paste from the perspective of working performance and uniaxial cubic compressive strength.…”