Abstract: A safe and environment coal-based solid waste hole-sealing material was prepared by us⁃ ing fly ash（FA）and slag（GGBS）as the main raw materials and adding DOPA modified polyacrylic acid （PAA）hydrogel. The mass ratio of FA to GGBS，sodium silicate modulus，water-cement ratio and DOPA modified PAA content were selected as independent variables，and the slurry viscosity and setting time were used as response values. The single factor effect and interaction analysis were carried out，and the quadratic polynomial regression model was established to optimize the comprehensive performance ratio. Scanning electron microscopy（SEM），Fourier transform infrared spectroscopy（FTIR），thermogravimet⁃ ric analysis（TG）and mercury intrusion analysis（MIP）were used for microscopic characterization. The results show that the water-cement ratio has the most significant effect on the rheology and condensation process of the slurry，and the interaction between the content of DOPA modified PAA and the water-ce⁃ ment ratio significantly affects the viscosity and stability of the slurry. When the mass ratio of FA to GGBS is 3∶7，the modulus of sodium silicate is 0.9，the water-cement ratio is 0.8，and the content of DOPA modified PAA is 8%，the setting time of the slurry is 91.2 min，and the viscosity is 543.1 mPa·s. Micro⁃scopic analysis showed that the early formed DOPA and Ca2+ or Al3+ water gel constructed a three-dimen⁃ sional network，which regulated free water through water absorption and promoted the increase of slurry viscosity and condensation propulsion. In the middle and late stages，the hydrogel slow-releases Ca2+ and Al3+，reacts with the active silicon-aluminum component to form a new gel phase，and superimposes the interfacial bonding of the particles to densify the structure and maintain a high viscosity level.

Key words: coal-based solid waste, modified hydrogel, response surface methodology, hole-sealing material, microstructural characterization