Coal pillar design is a critical component of underground mine planning in BORD and Pillar workings, directly influencing extraction ratio, operational safety, and long-term stability. In India, nearly 60% of underground coal reserves remain locked within development pillars, emphasizing the need for optimized design methodologies that balance safety and recovery. This study presents a systematic evaluation of coal pillar stability using laboratory-derived strength parameters and empirical pillar strength formulations, with special reference to a Degree-II gassy underground mine in the JHARIA Coalfield operated by Bharat Coking Coal Limited.
Point Load Index, Brazilian Tensile Strength, and moisture content tests were conducted to estimate in-situ strength characteristics. Pillar strength was computed using the CMRI empirical formulation, while pillar stress was determined using the Tributary Area Method. Factor of Safety (FOS) was evaluated for varying gallery widths (3.0 m to 4.8 m) and pillar widths (5 m to 45 m). Results indicate that optimum pillar width ranges between 18 m and 22 m for a gallery width of 4.2 m at 266 m depth, yielding FOS between 1.3 and 1.7 with improved extraction ratio. The study proposes a correlation framework between extraction percentage and safety factor to assist mine planners in achieving higher productivity without compromising statutory safety requirements