Abstract: In order to study effects of grouting time and amount on spatial diffusion behaviors of slurry in high-level borehole grouting in goaf, FLUENT numerical calculation method was adopted to construct a mathematical model of slurry diffusion in three-dimensional heterogeneous goaf under a condition of grouting with variable gravity and constant inclination. Then with 29406 working face of certain mine as a research object, it was confirmed through simulation analysis that fire prevention effect would be the best when grouting volume of a single hole is 40 m³/h and the maximum distance that slurry tends to flow is 50.8 m. The research shows that diffusion radius of slurry increases gradually and would have a peak value during vertical diffusion in goaf while during diffusion at bottom plate peak concentration of slurry will not change significantly with time. And as grouting amount increases, the maximum distance at which slurry tends to flow along with inclination shows a nonlinear upward trend. According to indicating gas monitoring data of goaf, simulation analysis results are consistent with that of field application.

Key words: high position drilling, goaf, grouting, fire prevention, slurry diffusion, numerical simulation