Abstract: Overlying strata in Sheng-Fu mining area belong to inferior hard roof．Because of the shallow burial depth and thick layered of main roof, it needs to avoid the large area caving of the main roof during the first weighting period of working face. In this paper, based on the different physical simulation experiments, the failure mechanism of main roof is discussed when blasting is used. In addition, the mechanical model of main roof failure is established, and the relationship between the first weighting step of main roof and the depth of blasting hole is deduced. Thus, the first weighting steps of main roof in Nanliang coal mine are calculated according to different explosion parameters. The parameters which are determined by experimental and theoretical studies have achieved good application results in field testing, which can provide reliable theoretical basis for determining the explosive parameters in implementing forced roof caving by deep-hole pre-blasting.

Key words: shallow coal seam, inferior hard roof, large area caving, forced roof caving, explosive parameters