Method for filling coal mine goaf with sand

The invention belongs to the technical field of goaf filling, and particularly relates to a method for filling a coal mine goaf with sand. The technical problems that follow-up utilization is difficult due to the fact that a goaf collapses along with time after a working face of a coal mine is excavated, and the backfilling cost is high in the prior art are solved. According to the method, a drilling machine is used for drilling from the earth surface to the position near an underground cut hole, a sand guide pipe is connected to a sleeve, and a sand outlet is cut in the lower portion of the sand guide pipe; the construction method comprises the following steps: after a digging face is tunneled for 20 meters, building trapezoidal blocking walls near a safety boundary supported by hydraulic props, reserving pipe penetrating openings in the blocking walls, penetrating sand guide pipes through the pipe penetrating openings, mounting blocking covers outside the walls, filling sand from the ground surface, and sto