Abstract: For the control of the overlying filling body in extracting the pillars in large rooms at high and medium levels, a mechanical state model of the roof of drift stoping face was established by using the finite difference simulation software FLAC3D and the stability of the orebody at setting different pillar and drift widths was calculated. The feasibility of extracting the pillars by upward drift continuous mining with advanced grouting was demonstrated and a series of safety technical measures taken before the pillar extraction were proposed: advanced roof-making by grouting, support enhancement by long cable anchorage and setting of roof protection layer. It was concluded that the subsidence of the overlying filling body can be effectively controlled by this roof protection layer so as to safe extraction of the pillars.

Key words: Pillar extraction, Filling body, Roof protection layer, Numerical simulation