Technology of Roof Weakening Processing in Underlying Seam of Contiguous Seams

In order to solve the problem of large initial caving step,the deep hole presplitting blasting technology had been used in interconnection of mining face to decrease the initial caving step. According to the natural situations and the mining technical conditions of No. 11 coal seam in No. 2 Underground Coal Mine of Pingshuo,the initial main roof caving step of initial mining face was calculated based on the mechanical model which the main roof was regarded as a clamped rock beam. The pressure detection and analysis results showed that the first collapse step was merely 15. 6 m after weakening processing and hanging area of the main roof above goaf was reduced,which meaned the danger of large pressure while the roof caved was prevented effectively. The safety during downward mining the initial mining face in the underlying seam of contiguous seams had been ensured.