A dynamic roof fall risk index for coal mine roadways

Roof stability is very important for safety mining, and Roof fall accidents will cause huge personal property loss. This article establishes a dynamic roof fall risk index(RFRI) which can predict stability of roof surrounding rock simply and easily. It includes two factors called rock characteristics value and separation value, in which, the former reflects geology condition of the roadway roof and the latter represents support situation. According to borescope record, the roof rock characteristics include lithology change, soft interlayer, fissure zone and fracture zone. The variable characteristics and their positions will all influence the rock characteristics value. The separation value can be obtained by multi-point borehole extensometers, then the RFRI could be calculated Finally, the RFRI treated by mathematical software can be exported to excavation blueprints, thus monitoring variation of roof stability. The zones with higher or continually increasing RFRI are hazard zones, which need reinforced support.