Preventing and Mitigating Side Spalling in Bord and Pillar Mining Methods: A Comparative Study

ABSTRACT: Side spalling of coal pillars (SSP) presents a persistent safety and stability challenge in Bord and Pillar Mining Methods (BPMM), particularly with the increasing adoption of Continuous Miner Technology (CMT). This study investigates SSP mechanisms through integrated field investigations across Indian coalfields and calibrated numerical modeling using FLAC3D. SSP is attributed to mining-induced stress concentrations, roof-floor competency, geological discontinuities, and pillar geometry. Field data from mechanized panels reveal spalling depths of 3-6 m, with extensive pillar dilation observed via four-way rib extensometers. Elastic and strain-softening simulations highlight the encroachment of stress into pillar cores and identify critical safety factor thresholds under varying gallery widths and acute corner geometries. The study evaluates mitigation strategies including rib/snook optimization, strategic rock bolting, shotcrete application, and advanced monitoring systems. Results emphasize the importance of adaptive support design in mitigating progressive pillar degradation and enhancing roof caving control. By correlating model outcomes with field performance, the study offers a framework for SSP prediction and control tailored to complex geo-mining conditions. These insights contribute to safer, more efficient pillar extraction practices, aligning with industry priorities for mechanized underground coal mining under high-stress regimes.