<p>In northern China, there are a large number of fault-cut karst collapse columns that create risks of water inrush from the Ordovician limestone aquifers beneath the coal seams. In this study, the movement of grouting slurry in a fault-cut karst collapse column and its seepage reduction and structural reinforcement mechanism were symmetrically studied by theoretical analysis, laboratory simulation, and field data verification. The flow of grouting slurry was found to be limited by the column boundary and fault-cut fractures. Under the combined actions of grouting pressure, column weight, and water pressure, the grout slurry mainly flows and diffuses along the column and fault-cut fractures to form a slurry vein skeleton. Specifically, a slurry movement model was established and a theoretical formula was deduced. The 9–6 karst collapse column in the Hemei No. 9 Coal Mine was taken as a research subject. The diffusion distance of the slurry in the column was calculated to be 24&#xa0;m, less than the field measured distance along the column and fractures (22–34&#xa0;m). A karst collapse column reinforcement mechanism of grouting was then proposed based on fracture closing and stress enhancement. The laboratory simulation tests suggest that the high pressure grout slurry increased the water pressure and soil pressure in the material simulation model by up to 44.4% and 71.4%, respectively. The extrusion of grout into the column closes fractures, increases the column’s density, reduces the column water output, and enhances the horizontal support stress of the column on the surrounding rock and the vertical stress to the highly confined water below the coal seam.</p>