Stability Analysis of Coal Pillars and Gallery Affected by Induced Stress-Driven Spalling Under Varying Depths

Abstract

Spalling in coal pillars leads to structural instability in deep underground mines, especially as depth increases. This study investigates spalling during seam development at CM Panel No. 95LE, Seam V, Churcha Mine (RO), SECL, situated at a depth of 385 m, with a 6.0 m width and an average gallery height of 3.8 m. A finite difference-based numerical modelling approach assessed spalling under various geo-mining conditions. Varying depths from 60 m to 600 m. Results, supported by field observations, carried out parametric analysis, show spalling begins at around 240 m and intensifies up to 600 m. At depths below 150 m, pillars remained stable with no deformation. Increased depth correlates with rising rock load height (RLH), indicating higher stress concentration. RLH values recorded at 240 m, 360 m, 500 m, and 600 m were 2.92 m, 3.15 m, 3.73 m, and 4.12 m, respectively. Field investigations confirmed spalling up to 1 m, highlighting the need for confinement in affected areas. GRP bolts were used to stabilise spalled sections. The Factor of Safety (FOS) increased from 2.03 (unbolted) to 2.55 (bolted), emphasising the effectiveness of bolting support in enhancing coal pillar stability.