Abstract: Due to continuous filling in Zhangzhuang Iron Mine，the accumulated water in the goaf is not easy to discharge，and the filling boreholes are damaged repeatedly due to long-term abrasion. There⁃ fore，it is necessary to optimize the underground filling boreholes and drainage facilities. Combined with the particle size characteristics of tailings in Zhangzhuang Mine，a new type of drainage pipeline is select⁃ ed to improve the drainage efficiency and roof-contacted filling speed. The causes of filling borehole failure are analyzed. Combined with the actual work，the filling pipeline is extended，the resistance of slurry along the way is increased，and the liquid level in the vertical pipeline is maintained on the erosion datum sur⁃ face，which effectively prolongs the life of filling borehole.

Key words: goaf filling, backfill drilling, drainage of filling