Improved Design of Room-And-Pillar Coal Mines for U.S. Conditions

The efficient and safe design of room-and-pillar coal mines still remains as one of the pressing problems facing the mining industry in the United States. Present day design is a trial-and-error approach based mostly on experience. Although much research has been directed to stability of mine roofs and coal pillars, no generally-accepted design method has been formulated. This paper reports on a three-year research effort directed to an improved design of room-and-pillar coal mining in the U.S.A. Essentially the study consisted of three aspects: (i) determination of stable roof spans; (ii) determination of the strength of coal pillars; and (iii) determination of safety factors for room-and-pillar coal mining in the United States. Furthermore, three novel approaches were utilized during this research: i) the "petite sismique" technique was assessed for possible determination of coal pillar deformability ii) the "Geomechanics Classification" was extended for determination of safe roof spans in room-and-pillar coal mining. iii) a national survey of the current design practice and mining dimensions was performed with the aim of assessing factors of safety for room-and-pillar coal mining The outcome of this work, which is summarized in this paper, is a design code for room-and-pillar mining in the United States.