Directional presplit blasting in an innovative no-pillar mining approach

Abstract

Abstract Directional presplit blasting (DPB) technology for an innovative no-pillar mining approach is introduced. First, a mechanical model is established to analyze crack initiation and coalescence using the new technology. The explosion pressure formula containing tress concentration factor explains the relationship between the quantity of explosives and the crack initiation and coalescence. Subsequently, a dynamic finite element simulation method is used to study the stress and damage evolution process of the blasthole wall in ordinary explosion and DPB. The simulation results indicate that the stress concentration factor is approximately 4c10 for the same quantity of explosives. Finally, a field test was conducted in the Fucheng coal mine of China. Based on the field test, the concept of cracking ability is proposed, the relationship between the quantity of explosives and cracking ability is determined, and the quantity of explosives is divided into four stages that are compatible with the roof rock strength. The results can provide some clinical guidance for application of DPB in other projects of the gob-side entry retaining by roof cutting.