Optimization of backfill materials and mechanistic study of full-stage stress-energy coupling evolution in continuous mining and filling stopes

• Constructed an integrated research framework combining material testing, constitutive parameter inversion, and four-stage energy evolution analysis in CMCB mining areas. • Elucidated the stress-energy coupling evolution mechanism across all stages of CMCB mining areas. • Quantitatively assessed the energy absorption capacity of the backfill material, revealing its role in regulating deformation and failure of the surrounding rock from an energy perspective. While China's " three unders " coal mining areas contain abundant resources, conventional coal mining technologies struggle to achieve green mining objectives, such as high recovery rates and surface subsidence control. Continuous mining-continuous backfilling (CMCB) technology has emerged as an effective technical approach under such conditions. Nonetheless, the coupling mechanism between material properties and stope stress-energy responses remains insufficiently explored quantitatively. An integrated research framework combining material properties, mechanical parameter inversion, and whole-process simulation was developed in this study under the engineering background of the CT11 working face of a coal mine in Shaanxi Province. It systematically elucidates the relationship between filling material ratio and stope stability. Additionally, SEM and XRD analyses were conducted to evaluate and confirm the suitability of coal gangue as a filling aggregate. Orthogonal tests were performed to determine the optimal mix ratio of coal gangue. Furthermore, with the strain-softening and energy model, the stress-energy evolution process in the mining area under different working conditions was analyzed. The results suggest that CMCB substantially enhances the mechanical environment of the stope. The total elastic energy of the stope drops to −0.62 × 10^4 J, and energy release is lowered by 32.9 times. The backfill material effectively restrained the deepening expansion of the plastic zones in the roof and floor strata, enabling the significantly enhanced stability of the mining area. These findings lay a theoretical foundation and practical reference for the optimal design of filling materials and the implementation of green and safe mining under CMCB conditions.