Abstract: The 4 million t/a secondstage mining project of Dahongshan Iron Mine adopts the highsegment structure parameters of the subcolumn sublevel caving method of 30 m×20 m,which has played a leading level in similar mines in China.Affected by mining methods,the problem of overhanging after blasting has become a common problem in the sublevel caving method without bottom pillar.In order to solve this problem,the main reasons for the occurrence of the suspended ceiling and the measures for the natural fall of the blasting vibration of the peripheral approach to treat the suspended ceiling are mainly studied.After longterm use and verification in Dahongshan Iron Mine,its safe,reliable and lowcost characteristics are best arranged in the suspension treatment measures and have good promotion and application value.

Key words: Sublevel collapse of bottomless columns,Hanging top,Treatment plan,Research and Application