Performance evaluation and hierarchical deformation control of coal gangue backfill in deep gob filling

For coal mining carbon neutrality and resource recycling, crushed gangue is widely used in underground backfilling to control surface subsidence and utilize waste; this study focuses on the mechanical response and deformation mechanisms of gangue backfill columns under varying loading/geometric conditions to support partial gob filling, via methods: laboratory uniaxial compression tests, DEM simulations, GRA, and theoretical derivation based on equivalent extraction height theory, with key indicators (residual height ratio, volumetric deformation, structural integrity) evaluated. Results show the residual height ratio’s two-stage decay with H/D ratio (rapid drop at 0.05–0.40, then gentle decline, remaining >0.9 under low stress/small aspect ratio); GRA identifies support confinement as the dominant factor (correlation = 0.65), followed by overburden stress (0.60) and H/D ratio (0.56), with confined conditions significantly enhancing anti-deformation capacity. A predictive deformation model and filling rate framework were established, revealing filling rate’s logarithmic attenuation with overburden load, positive correlation with planar filling efficiency (>0.5), and 15–20% improvement under 2 MPa pre-compaction. A hierarchical control strategy prioritizing confinement quality, stress regulation, and optimal geometry (H/D ≤ 0.40) provides direct guidance for deep mining backfill stability, while this research optimizes gangue backfill performance, enriches green mining technologies, and supports geotechnical engineering and sustainable mining.