Rib stability: A way forward for safe coal extraction in India

Abstract

Ensuring rib stability during pillar extraction is of prime importance in bord and pillar (B&P) method of underground coal mining with caving. Rib stability has been assessed here by way of assessing factor of safety (FOS), a ratio of the strength of rib to stress on it. Earlier formulations for rib stability when applied to case studies gave very low FOS value suggesting significant ground control problems, which were contrary to the field observations. This has necessitated the need to revisit the concept of rib stability. The stress coming on the rib is estimated with the use of numerical modeling technique using the FLAC3D software. The methodology of assessing rib-stability with the help of suggested rib-strength formulation has been validated at eight Indian coal mines. The outcome of this study finds relevance and importance in ensuring underground coal liquidation with improved safety and conservation. Keywords: Rib stress estimation, Rib-strength, Rib-stability, Numerical modeling, Bord & pillar method, Underground coal extraction