Abstract: To address the coupled requirements of long-distance pipeline transport and the load-bearing-deformation performance of hardened backfill in the mining of coal resources beneath buildings,railways,and water bodies at Pingdingshan No. 11 Mine,a coal-based solid-waste paste backfill was prepared using site-sourced coal gangue,fly ash,and cement as the primary constituents. A three-factor,three-level orthogonal experimental design was adopted,with solids mass fraction,fly ash content,and cement content as the governing variables. Slump,spread,28-day uniaxial compression,and three-dimensional fracture-surface scanning tests were conducted to systematically characterize the initial flowability,load-bearing-deformation behavior,and fracture-surface morphology of mixtures with different proportions. The results indicate that the solids mass fraction is the dominant factor controlling the initial flowability. As the solids mass fraction increased from 80% to 84%,the average slump decreased from 144. 3 mm to 129. 7 mm,while the average spread decreased from 402. 0 mm to 248. 7 mm. Increasing the fly ash content initially improved and subsequently reduced the flowability, whereas increasing the cement content generally diminished the spreading capacity of the paste. The 28-day uniaxial compressive strength of the nine mixtures ranged from 1. 87 MPa to 3. 02 MPa,and the hardened backfills exhibited pronounced compaction adjustment and sustained load-bearing behavior during compression. Range analysis showed that the influence on the 28-day peak stress followed the order of cement content > fly ash content > solids mass fraction,whereas both peak strain and the total input strain-energy density at peak stress were governed primarily by the solids mass fraction. These results demonstrate that the dominant factors controlling load-bearing capacity and deformation adaptability are not identical. Macroscopically,the specimens exhibited through-going cracking,radial dilation,localized spalling,and localized failure depending on the mixture proportion. The fracture-surface roughness parameters S_a,S_q,and S_z were generally positively correlated with compressive strength, with Pearson correlation coefficients of 0. 871, 0. 836,and 0. 667. In contrast,the fractal dimension D ranged from 1. 968 7 to 2. 018 2 and showed no evident linear correlation with compressive strength. Overall, mixture proportioning of coal-based solid-waste paste backfill should account for both transport-related flowability and post-hardening load-bearing-deformation performance. The findings provide an experimental basis for optimizing backfill mixtures under long-distance transportation conditions at Pingdingshan No. 11 Mine.