Protecting Underground Coal Miners From Rib Falls

摘要

In 2010, the number of fatal rib falls in U.S. underground coalmines exceeded fatal roof falls for the first time ever. While recenttrends have seen roof fall fatalities reduced by about 62% since the1990s (from an average of 9.6 per year in the 1990s to 3.6 per yearduring the last five years), the incidence of rib fall fatalities hasremained approximately constant (about 1.5 per year). In addition,injury incidents associated with pillar rib failure have been steadyat approximately 100 per year. The persistence of rib fall injuries,underlined by the recent increase in rib fall fatalities, has led tothis investigation of the coal rib failure parameters and methodsavailable to mitigate rib failure in U.S. underground coal minesA detailed study of the 21 fatal rib fall incidents that haveoccurred since 1995 (excluding coal burst incidents) indicates thatthe two most important risk factors are the mining height and thedepth of cover. The depth of cover was 700 ft (213 m) or greaterin 81% of the fatalities, and the mining height was at or exceeded7 ft (2 m) in every instance but one. Other risk factors includedmultiple seam interactions, rock partings in the seam, and retreatmining. The accident history reveals that joints or slickensidefeatures within the rib increase the hazard. Approximately threequartersof the rib fatality victims were roof bolting machineoperators and continuous mining machine operators.This paper includes a brief overview of techniques for ribcontrol; including bolts, standing support, bent steel straps,and rib strapping. The available mining equipment features forinstalling rib support and protecting operators from rib falls arealso discussed. A proactive approach to rib control using availabletechnologies will lower the risk to miners and is an endeavor thatmust be pursued to reduce rib fall accidents.