Abstract: Reduced caving technology was a new method to treat the mined-out area. In this method，the dispersions bedding was used to separate the space connection between the working face and the mined-out area to prevent from the injury of impact air waves. Through summarizing the successful experience of preventing the injury of impact air waves with dispersions bedding，the formula to count the minimum thickness of the dispersions bedding was obtained. The dispersions beddings′ thickness of four deposits in Shujigou iron mine were calculated through the formula obtained above according to the actual situation of four medium mined-out areas at field No.2 and the specific technical measures were proposed to prevent the injury of impact air waves. The minimum thickness of dispersions bedding and the technical measures were proved effective through the implementation of the program.

Key words: Mined-out area, Dispersions bedding, Reduced caving, Impact air waves