Tangjiahui Mine No. 6 coal seam remains North China type Carboniferous Permian system. No. 6 coal seam mined under pressure, and the coal seam floor was subjected to O-ash water pressure of about 1.5 MPa, and the distance between the coal seam and O-ash is about 40-60 m. Because of the strong water-richness of No. 6 coal and the fault development, the safe mining of No. 6 coal was threatened by ash water at the bottom. The DF2 fault was developed in the west wing of the mine, and the fault drop was 18 m. The transportation roadway in the west wing must pass the fault, so the ground treatment project was carried out, and the tuff roots of the DF2 fault were grouted and blocked by using large-diameter directional drilling, and the underground transportation road safely passed the DF2 fault in 2019, and there was no water when the fault was exposed, and there were cement lumps in the fault zone, which proved that the fault zone was filled with cement slurry and reinforced thoroughly. The treatment effect was good.