Pressure-Relief Mechanism and Application of Large-Diameter Boreholes in Coal Seams with Rockburst Hazard

Drilling of large-diameter boreholes is regarded as an effective measure for rockburst prevention. By investigating the morphological characteristic and evolution plastic zone in borehole surrounding rock, pressure-relief mechanism was ascertained, engineering application assessed 13230 working face Gengcun Coal Mine, Henan Province, China. The results showed that (1) rock appear circular, elliptical, butterfly shapes, which maximum size wings several times larger than diameter; (2) under certain stress conditions, multiple distributed coal seam with risk lead to generation coalescence large-range butterfly-shape zone. They reduce concentration capacity storing elastic energy seam, thus reducing seam; (3) significantly decrease front improve environment head entry, promoting safe mining face.